TWI697234B - Self-calibrating optical detector - Google Patents

Abstract

The present disclosure includes systems and methods for calibration of an optical sensor package, including setting an initial detection threshold of a detector, gradually increasing a power level of a signal generator that is in communication with a detector to cause a detected power at the detector to exceed the initial detection threshold, storing in a memory a first power level of the signal generator at which the detected power at the detector exceeds the initial detection threshold, and adjusting the initial detection threshold of the detector to an adjusted detection threshold to include a detection buffer amount within the adjusted detection threshold.

Description

Self-calibration of optical detector [Cross-reference of related applications]

This application declares that it has the priority of the US patent application 15/170,511 filed on June 1, 2016, and the patent application declares that it has the US temporary patent application 62/filed on May 31, 2016. 343,657 Priority rights and interests, this application hereby cites the entire content of the provisional patent application for reference, as if the provisional patent application is fully described below, and for all applicable uses.

The disclosure of the present invention is generally related to a system and technique for self-calibrating optical sensor combinations used to detect changes in a target medium.

In various industries, there is a need for sensor combinations that can detect changes in the material passing between a signal generator and a detector at a high rate. For example, a user may wish to run a sensor combination when an adhesive label attached to a side of a backing paper is run through a sensor Count the number of self-adhesive labels attached to a piece of backing paper. By sensing the change in transparency between the label and the backing paper, the sensor combination can pass the signal generator (eg, a light emitting diode) and the detector (eg, a light detection) at each label Between the detector (photodetector).

The changes that the sensor combination looks for may be extremely small, requiring very sensitive detection. In some applications, the change may be small enough to cause variations in the manufacture of parts of the sensor assembly, variations in the temperature of the sensor assembly, changes in the material path when the material passes through the sensor assembly, etc. May cause detection errors. Therefore, the sensor combination must be calibrated according to the specific environment in which the sensor combination is used and the specific components used to assemble the sensor combination. Usually, the calibration is performed manually, and a one-time permanent adjustment of the sensor combination is performed based on the test in the target environment. Therefore, it is hoped that such a calibration method can be improved.

Therefore, it is desirable to have a system and method that can calibrate a sensor combination by itself, and the method of the system and method to calibrate a sensor combination by itself is: setting a detection threshold of a detector and gradually ramping up The power level of a signal generator enables the detector to receive signal energy exceeding the detection threshold under normal operating conditions, and adds a detection buffer to the detection threshold to ensure that even in the The system can also perform detection when there is variation in the signal energy received by the detector.

In one aspect disclosed by the present invention, a calibration method includes: a controller sets an initial detection threshold of a detector. The method further Including: gradually increasing the power level of a signal generator communicating with the detector and the controller, so that the detected power on the detector exceeds the initial detection threshold. The method further includes: storing, by the controller, a first power level of the signal generator when the detected power on the detector exceeds the initial detection threshold in a memory. The method further includes: after the power level of the signal generator reaches the first power level, the controller adjusts the initial detection threshold of the detector to make an adjusted detection threshold A detection buffer amount is included in the adjusted detection threshold.

In another aspect disclosed by the present invention, a computer program product has a computer-readable medium that can tangibly record computer program logic for calibrating a detector and a signal generator. The computer program product includes program code for receiving a detection threshold setting signal including the initial detection threshold from a user. The computer program product further includes program code for receiving a calibration signal from the user to instruct the computer program product to gradually increase the power level of the signal generator. The computer program product further includes code for receiving from the user a threshold change signal including a user programmable amount for adjusting the initial detection threshold.

In yet another aspect disclosed by the present invention, a computing device includes a memory for accommodating a machine-readable medium, the machine-readable medium includes machine-executable code, and the machine-executable code has been stored therein For executing a method of calibrating a sensor and a signal generator. The computing device further includes a processor coupled to the memory, the processor configured to perform an initial detection for the processor to set the sensor Machine executable code for critical values. The processor is further configured to execute a machine for gradually increasing the power level of the signal generator communicating with the sensor so that the detected power on the sensor exceeds the initial detection threshold Execution code. The processor is further configured to execute a machine for storing a first power level of the signal generator in a memory when the detected power on the sensor exceeds the initial detection threshold Execution code. The processor is further configured to execute the initial detection threshold of the sensor after the signal generator reaches the first power level such that an adjusted detection threshold will detect The amount of buffer contains the machine executable code within the adjusted detection threshold.

100‧‧‧Optical sensor combination

102‧‧‧ LED

104‧‧‧ Photodiode

106‧‧‧slot

108‧‧‧Target medium

112‧‧‧Part 1

114‧‧‧Part Two

202‧‧‧Power

204‧‧‧Oscillator

206‧‧‧ bandgap reference voltage

208‧‧‧ Analog front end

210‧‧‧Comparator

222‧‧‧ LED driver

226‧‧‧ State machine

228‧‧‧Multiplexer

214‧‧‧ memory

216‧‧‧Communication interface

218‧‧‧ Calibration status pin

220‧‧‧Output pin

302‧‧‧stable mode

304‧‧‧Operation mode

306‧‧‧Enable mode of LED driver

308‧‧‧LED driver not enabled mode

310‧‧‧Calibration mode

312‧‧‧ Status mode

502‧‧‧No adjustment calibration detection threshold

504‧‧‧Minimum detection threshold

508‧‧‧Detection threshold

510‧‧‧Adjusted calibration detection threshold

FIG. 1A shows an optical sensor combination according to an embodiment disclosed by the present invention.

FIG. 1B shows an alternative optical sensor combination according to an embodiment disclosed by the present invention.

FIG. 2 shows a control system of the optical sensor combination according to an embodiment disclosed by the present invention.

FIG. 3 shows a state diagram of the operation of a state machine according to an embodiment disclosed by the present invention.

FIG. 4 shows a block diagram of a method for self-calibrating the sensor combination according to an embodiment disclosed by the present invention.

Figure 5A shows a graph of the power received by a photodiode at room temperature.

Figure 5B shows a graph of the power received by a photodiode at high temperature.

The detailed description, which will be described in the following in connection with the drawings, is intended to be a description of various configurations, and is not intended to represent the only configurations that can implement the concepts described in the present invention. This detailed description contains specific details in order to provide a thorough understanding of various concepts. However, those skilled in the art should understand that these concepts can be implemented without these specific details.

The disclosure of the present invention describes a system and method for self-calibrating a sensor system including a signal generator and a detector to detect changes in a target medium. For simplicity, the embodiments of the present invention will use a light emitting diode (Light Emitting Diode; LED for short) as the signal generator and a light diode as an optical sensor of the detector Detector combination, but the scope of the embodiments may include any suitable signal generator or photon detector.

In some applications, the sensor combination can be used to detect small changes in the light received on the photodiode. For example, the difference in transparency (or transmittance) between a label affixed to a backing paper and the backing paper itself may be very small. The sensor combination should be able to sense this slight change in transparency. However, the change may be so small that changes in the sensor assembly and environmental changes may cause false detection. For example, the change in the LED output or the sensitivity of the photodiode, the change in the lens of the LED package or the change in the photodiode package, the LED or the photodiode Changes in the placement of the polar body within the sensor combination, changes in the temperature in the sensor combination, or changes in the path of the target medium through the sensor combination, etc. may each be sufficient alone or together to cause Detect errors.

In order to prevent detection errors due to these changes, it is desirable to be able to calibrate the sensor combination. In one embodiment, the sensor combination is designed to calibrate itself. The self-calibration can be initiated by a command from the user, or can be automatically calibrated immediately after the sensor combination is powered on. In some embodiments, as will be explained further below, the user can supply various parameters to the sensor combination before calibration.

The embodiments disclosed in the present invention describe a system and method for calibrating an optical sensor combination so as to detect changes between two target materials as they pass through the sensor. After receiving a calibration request, the output power of an LED is gradually increased until the light received from the LED on a photodiode exceeds a preset detection threshold. Then, the LED power level when performing the detection is stored as a calibration parameter. However, when using the above detection threshold and LED power level to operate the sensor combination in order to sense the target material, the amount of light received on the photodiode will be reduced by even a small amount of variation in the system Changes will also reduce the received light below the detection threshold, resulting in the failure of the required detection.

To solve this problem, the detection threshold is adjusted by an amount that exceeds the expected change, and a detection buffer amount is provided. For example, if the change may reduce the amount of light received on the photodiode by 15%, reducing the detection threshold by 20% will ensure that the change will not cause the amount of received light to decrease below the detection Measure the critical value. In this example, the detection buffer amount is the adjusted The 5% difference between the detection threshold of the detector and the expected effect of the change on the detector.

Of course, the percentages provided above are examples, because other systems may include appropriately different detection buffers. In various embodiments, the detection threshold can be adjusted by testing, simulation, or other methods, so that the difference between the impact of the change and the adjusted detection threshold reduces the chance of false detection to a specific Acceptable degree of application. The adjusted detection threshold is stored as a calibration parameter. When power is supplied to the optical sensor combination after power off, for example, the LED power level and the adjusted detection threshold are used, so no recalibration is required.

An embodiment disclosed in the present invention includes a controller having a memory address for storing calibration values and storing computer-readable program codes that use those calibration values during normal detection operations. In one example, the user sets a first detection threshold in a memory address of the controller and starts a calibration operation. The system then gradually increases the amplifier level of a signal generator until the detector detects the signal that reaches the first threshold, and verifies the first threshold. If the detector does not detect the signal using the first threshold, the user can change the first threshold so that the signal generator can operate within the operating range based on its available amplifier level The signal is detected.

Assuming that the first threshold level has been verified by a successful detection, the controller stores the amplifier level corresponding to a point at which the first threshold level is reached, and continues the calibration operation. The user can then set a second detection threshold with a detection buffer, and adjust the detection level. The detection buffer amount will be described in further detail below, and in this embodiment, the detection buffer amount corresponds to the difference between the effect representing the expected change and the second threshold level to avoid false detection and/or An undetectable quantity. The controller then stores the amplifier level and the second threshold in memory addresses used during normal operation of the controller. After rebooting or at some other appropriate time later, the controller then uses the amplifier level and the second threshold to perform detection, and the detection buffer amount built into the second threshold is Unnecessary operations caused by changes will be reduced or minimized.

Referring now to FIG. 1A, an optical sensor assembly 100 according to an embodiment disclosed by the present invention is shown. In this embodiment, the sensor assembly 100 includes a light-emitting diode (LED) 102 and a light-emitting diode 104 with a slot 106 between the LED 102 and the light-emitting diode 104, as shown by the directional arrow 110 , A target medium 108 can pass through the slot 106. In some embodiments, the LED 102 may be an infrared (IR) LED or other LEDs with appropriate wavelengths. The LED 102 outputs light toward the photodiode 104. When the target medium 108 passes through the groove 106, the amount of light transmitted through the target medium 108 changes according to the transmittance of the portion of the target medium 108 between the LED 102 and the photodiode 104. In some embodiments, a first portion 112 of the target medium 108 may be more opaque or reflective than a second portion 114 of the target medium 108. For example, the target medium 108 may be a piece of backing paper with a self-adhesive label attached to it. In this example, the labels are the first portion 112 of the target media 108, which is more opaque than the backing paper that is the second portion 114 of the target media 108.

Referring now to FIG. 1B, there is shown an alternative embodiment of an optical sensor assembly 100 according to an embodiment disclosed by the present invention. In this embodiment, an LED 102 and a photodiode 104 are positioned close to each other, and as indicated by the directional arrow 110, a target medium 108 passes over the LED 102 and the photodiode 104. In this embodiment, the LED 102 outputs light toward the target medium 108, and the light diode 104 detects the light reflected from the target medium 108. When the target medium 108 passes over the sensor assembly 100 along the directional arrow 110, the amount of light reflected from the target medium 108 is based on the reflectance of the portion of the target medium 108 between the LED 102 and the photodiode 104 ) And change.

Referring now to FIG. 2, a control system of an optical sensor assembly 100 according to an embodiment disclosed by the present invention is shown. The control system can be implemented as an application specific integrated circuit (ASIC for short), which is one of the logics for executing the actions shown in the state machine of FIG. 3. However, the scope of the various embodiments may include any kind of logic circuit such as a general-purpose central processing unit that executes machine-readable program code for performing calibration and detection actions according to the present invention. A power supply 202 supplies power to the circuit. An oscillator 204 generates a clock signal for providing the timing of the operation of the circuit of the sensor assembly 100. In some embodiments, the oscillator 204 may provide a high frequency clock signal such as a 4 million hertz (MHz) signal. An energy bandgap reference voltage 206 generates a fixed voltage independent of the voltage supplied by the power source 202 and independent of the temperature change in the system. The fixed voltage is fed to the system such as oscillator 204, analog front end 208, comparator 210, and LED driver that will benefit from the fixed voltage Other elements such as actuator 222.

The analog front end 208 receives analog signals from the LED 102 and, as will be explained further below, processes the analog signals for comparison on the comparator 210 with a detection threshold determined by a user. In some embodiments, the photodiode 104 is part of the analog front end 208, but it should be understood that the photodiode 104 may be a discrete element connected to the analog front end 208. The analog front end 208 further includes a transimpedance amplifier, an integrator stage, a gain stage, and a comparator with a programmable reference signal generator. The transimpedance amplifier is used to amplify the output of the photodiode 104 to a voltage that can be used by the rest of the system.

The transimpedance amplifier of the analog front end 208 may have its own gain controlled by a bandpass filter feedback loop to compensate for the current generated by the photodiode 104 in response to ambient light. As will be further explained with reference to FIG. 4 below, the gain of the transimpedance amplifier can be further automatically increased by one of the gains of the transimpedance amplifier during calibration according to the intensity of the signal received by the photodiode 104 from the LED 102 Gain selection circuit control. The automatic gain selection circuit may also be provided with a gain level that will be used by the state machine 226 if calibration has been performed. In some embodiments, the automatic gain selection circuit may have 3 gain settings, but in some embodiments any suitable number of gain settings may be used.

The integrator stage of the analog front end 208 performs operations such as eliminating low frequency noise and power supply ripple, making the optical diode 104 signal reference to the bandgap reference voltage 206, and output from the optical diode 104 (possibly It is a pulse wave) to generate a sawtooth wave signal and thus reduce the various functions such as the influence of the bandwidth variation in the output of the optical diode 104. This gain stage of the analog front end 208 boosts the output signal to a level suitable for the comparator 210.

The comparator 210 receives the output of the analog front end 208 and a pre-programmed reference level, and compares the two. The output state of the comparator 210 changes according to this comparison. For example, when the output of the analog front end 208 exceeds the pre-programmed reference level, the output state may be a binary one, or when the output of the analog front end 208 is lower than the reference level, the output state may be a binary zero (or vice versa) ). In other words, when the output level of the analog front end 208 changes above or below the reference level, the output state may change. The reference level can thus be used as a detection threshold. In one embodiment, the user can select the pre-programmed reference level from a range of 16 available reference levels (for example, a change of approximately 7% between each reference level and the next reference level) Standards, but the scope of the embodiments includes any suitable number of reference levels.

The output of the comparator 210 is sent to a filter 212. The filter 212 is used to filter out changes in the state of the comparator 210 due to the detection of an event outside the desired portion of the target medium 108. Such events may include ambient light incident on the light diode 104 that causes the output of the analog front end 208 to exceed the reference level on the comparator 210, or the sensor combination 100 that causes the comparator 210 to output a state change Events such as electrical noise. The filter 212 may need to view a state change on its input in multiple consecutive cycles before transmitting the state change to its output. In some embodiments, the filter 212 may wait until the input is within an appropriate number of clock cycles During a period (for example, 2 cycles), a state of change is maintained before the state change is output. This state change can be output to the state machine 226 and the multiplexer 228, and these two cases will be further explained below.

The memory 214 stores various information blocks used by the sensor combination 100. In this embodiment, the memory 214 is an Electrically Erasable Programmable Read Only Memory (EEPROM), but it can be any other suitable memory device. In one example, the memory 214 stores computer-readable program code that provides the logic of the state machine 226 to be read and executed by the processor. In some embodiments, after the calibration is performed, various information blocks related to the calibration of the sensor combination 100 are stored in the memory 214, and will be described below with reference to FIGS. 3 and 6, The state machine 226 accesses the memory 214 to retrieve calibration information immediately after the sensor assembly 100 is powered on. For example, the memory 214 may store a driving level of the LED driver 222, an automatic gain selection value of the transimpedance amplifier gain of the analog front end 208, and a calibration bit for indicating whether the sensor combination 100 has been previously calibrated ( (Or flag), an output type and polarity, a detection threshold of the comparator 210, an internal oscillator calibration factor of the oscillator 204, and a temperature compensation factor of the bias generator 224 factor).

The communication interface 216 facilitates communication between the sensor assembly 100 and the user for functions such as calibration. The communication interface 216 may be an interface such as an internal integrated circuit (I2C) bus. An external microcontroller controlled by the user can be connected to the sensing via calibration status pin 218 and output pin 220 器组合100。 100 combination. In one embodiment, the input to the communication interface 216 is received via the calibration status pin 218, and as will be explained further below, these inputs are transmitted to the state machine 226. The output is received from the state machine 226, and the outputs are transmitted to the user microcontroller via the calibration state pin 218 or the output pin 220 according to the type of output. As will be described further below, the multiplexer 228 can multiplex the output of the communication interface 216 transmitted to the output pin 220 and the output of the comparator 210.

As will be explained further below, the LED driver 222 drives the LED 102 according to input received from the state machine 226. In some embodiments, the LED driver 222 may drive the LED 102 to 95 milliamperes (mA) at room temperature, but in some embodiments any suitable maximum or minimum current may be used. As will be explained further below, the LED driver 222 can be controlled by the output of the state machine 226.

The bias voltage generator 224 may be a Proportional To Absolute Temperature (PTAT) bias voltage generator that provides a current to the LED driver 222 according to the internal temperature of the sensor assembly 100. The current supplied to the LED driver 222 may increase or decrease the output size of the LED driver 222 when the internal temperature of the sensor combination 100 changes. Such a method may, for example, compensate for variations in the output of the LED 102 due to changes in temperature.

The state machine 226 automatically manages the functions of the components of the sensor assembly 100 when powered on, and dynamically manages the functions of the components of the sensor assembly 100 according to user input received via the calibration status pin 218. In this embodiment, the state machine 226 manages the memory 214 and the communication interface. 216. Functions of each element of the LED driver 222 and the multiplexer 228. The state machine 226 represents the logic function of the ASIC or other processor when executing the calibration procedure described in the present invention. Although a processor is not explicitly shown as a hardware part in Figure 2, it should be understood that the system of Figure 2 can be implemented as an ASIC or other processor including input, output, and power supply terminals .

The multiplexer 228 receives input from the filter 212 and the communication interface 216, and multiplexes the input to the output pin 220. The state machine 226 provides the selector input to the multiplexer 228, and thus selects which of these inputs to pass through the multiplexer 228 to the output pin 220. Generally, the output of the filter 212 will be selected as the output. This method allows the user to read the processed output of the photodiode 104 to determine whether a target medium has been detected. In some embodiments, the user controller may send a read request to the state machine 226 (eg, a read request for the calibration information of the memory 214). In this case, the state machine 226 will The memory 214 retrieves the requested information, and transmits the information to the multiplexer 228 via the communication interface 216, and then selects the input from the communication interface as the output from the multiplexer to the output pin 220.

Referring now to FIG. 3, there is shown a state diagram 300 of one of the operations of the state machine 226 according to an embodiment of the invention. Immediately after the sensor assembly 100 is powered on, the state machine 226 enters the stability mode 302 during a period that allows the memory 214 to settle to a stable state. Depending on the frequency of the oscillator 204, this period may be from about 2.5 ms to about 26 ms from the EEPROM memory 214. However, it should be understood that the stability mode may be used in various embodiments 302 any suitable duration. In the stability mode 302, the calibration state pin 218 becomes the output of the state machine 226, and the calibration state pin 218 is set to indicate to the user microcontroller that the sensor assembly 100 is in a state of the stability mode 302. In some embodiments, the calibration state pin 218 may be set to a low binary state (logic "0") for this purpose. After allowing the maximum possible amount of time for the memory 214 to settle, the state machine 226 may retrieve the automatic gain selection from the memory 214 and provide the automatic gain selection to the transimpedance amplifier of the analog front end 208 to adjust the gain setting value. In some embodiments, there may be any suitable number of possible gain settings, and two or more bits in the memory 214 may accommodate the automatic gain selection value. The acquisition of the automatic gain selection value may take from 10 microseconds to 102 microseconds, but in operation, each embodiment may use any appropriate amount of time.

After the stabilization period ends and the automatic gain selection value is captured, the state may automatically transition to the operation mode 304. During the operation mode 304, the calibration status pin 218 becomes an input of the state machine 226, and the communication interface 216 is enabled to receive communication from the user. In some embodiments, during operation mode 304, an internal pull-up resistor can pull the calibration status pin 218 to a high level (pull to logic "1"). The state machine 226 then reads from the memory 214 a calibration flag indicating whether one of the previous calibrations has occurred.

If the calibration flag is set (eg, a flag bit is set to "true" or logic "1"), the state machine 226 transitions to the LED driver enable mode 306. State machine 226 reads a calibrated LED driver bit from memory 214 And enable the LED driver 222 to start transmitting the pulse wave at the calibrated level.

If the calibration flag is not set (eg, the flag bit is set to "false" or logic "0"), the state machine 226 transitions to the LED driver inactive mode 308. In this state, the LED driver 222 is disabled, and the state machine 226 only has to wait for a calibration request from the user.

When a calibration request is received from the user (eg, from a microcontroller controlled by the user) via the calibration status pin 218 in the LED driver enabled mode 306 or the LED driver disabled mode 308, the state machine 226 transitions to Calibration mode 310. When entering the calibration mode 310, the state machine 226 returns the calibration state pin 218 back to being raised to a high level. In addition, the state machine 226 instructs the memory 214 to clear calibration-related values (eg, LED driver level, automatic gain selection value, and calibration flag), and allows the memory 214 to have a stable time (eg, approximately 5 ms) .

The state machine 226 guides the calibration procedure described further below with reference to FIG. 4. After successful calibration, the state machine 226 instructs the memory 214 to store various calibration values. For example, the memory 214 may store the LED driver level due to the calibration, the automatic gain selection value used for successful calibration, and it may set the calibration flag to indicate successful calibration (eg, setting Is "true" or logical "1"). If the calibration is unsuccessful, the state machine 226 can keep the memory 214 unchanged.

After the calibration is completed, the state machine 226 can enter the state mode 312 whether or not it is successful. Calibration takes a known amount of time. In a method such as that shown in Figure 4, calibration may take about 10 milliseconds. After passing this After the memory settling time and the calibration time (which may take about 15 milliseconds in total), the user controller can be programmed to look for a calibration completion signal during a selected time window. If the calibration is successfully completed, the state machine 226 may drive the calibration state pin 218 to a low level (eg, logic "0") during the selected time window, and indicate to the user that the calibration was successful. If the calibration is unsuccessful, the state machine 226 may keep the calibration state pin 218 at a high level (eg, logic "1") during the selected time window. After the selected time window has passed, the state machine 226 automatically transitions back to the operating mode 304 until further user input such as another calibration request is received.

Referring now to FIG. 4, a block diagram of a method 400 for self-calibrating the sensor assembly 100 according to an embodiment disclosed by the present invention is shown. For ease of description, the reference sensor assembly 100 is designed to detect an example of a decrease in light received on the photodiode 104 (eg, when the transmittance of the target medium 108 decreases). In this embodiment, calibration is performed with the most transmissive portion of the target medium 108 in the groove 106. It should be understood that calibration can also be performed on the least radiopaque portion of the target medium 108 in the slot 106. It should also be understood that other embodiments may use a similar method to detect an increase in light received on the photodiode (for example, to detect when the transmittance of the target medium 108 increases).

In block 402, a controller such as state machine 226 supplies a reference level to comparator 210. As mentioned above, the reference level can be pre-programmed by the user from a set of available reference levels. In an embodiment described above, the device may have 16 reference levels selected from it. For example, make The user can instruct the state machine 226 to set the reference level to 7, and the state machine can supply an appropriately increased or decreased voltage signal to the comparator 210.

In block 404, the state machine 226 applies an automatic gain selection to the transimpedance amplifier of the analog front end 208. In this example, there are 3 possible gain levels selected for the automatic gain selection, and the state machine 226 starts calibration with the lowest gain selection. This automatic gain selection is used to adjust the sensitivity of the analog front end 208 to the light received on the optical diode 104. The higher the gain, the more sensitive the front end 208 is to the output from the photodiode 104.

In block 406, the state machine 226 instructs the LED driver 222 to gradually increase the current supplied to the LED 102 from the initial current output such as 0 mA to a maximum current output such as 95 mA. In some embodiments, the LED driver 222 may be instructed to transmit a current pulse to the LED 102, while increasing the current output in discrete steps, and repeating the pulse for a preprogrammed number of times at each current step . For example, the LED driver 222 may be instructed to gradually increase the current output from 0 mA to 95 mA in 1000 steps or levels (thus increasing the current output by 95 μA in each step), and at each step The current pulse is transmitted to the LED 102 five times in the current step. The width of each pulse can also be pre-programmed, and the width can be such as 250 nanoseconds. Each pulse can have a neutral period such as 150 nanoseconds, resulting in a period of 2 microseconds per current step, and gradually increasing to a total period of 2 milliseconds when completing all 1000 steps. However, the number of steps, the amount of current, and the width of the pulse wave may be different in other embodiments.

In decision block 408, the state machine 226 monitors the output of the filter 212 as the LED driver 222 gradually increases its current output supplied to the LED 102 Is there any change in output status? As mentioned above, the reference level supplied to the comparator 210 is effectively used as a detection threshold, and the filter 212 operates to filter out abnormalities that exceed the detection threshold due to interference Detection. Therefore, the state change of the output of the filter 212 indicates the successful detection of one of the light exceeding the detection threshold of the photodiode 104 processed by the analog front end 208. If the LED driver 222 gradually increases up to its maximum current output without successful detection, then the method 400 moves to decision block 410. If there is a successful detection, the method 400 moves to block 416. Each block will be explained in turn below.

In decision block 410, the state machine 226 checks whether the automatic gain selection is at its maximum value. If the automatic gain selection is not at its maximum value, the method 400 moves to block 412. If the automatic gain selection is already at the maximum value (eg, the automatic gain selection is such as level 3 of 3 possible levels), the calibration fails, and the method 400 moves to block 414. Each block will be explained in turn below.

In block 412, the state machine 226 increases the automatic gain selection of the transimpedance amplifier of the analog front end 208 in order to increase the sensitivity of the analog front end 208. For example, if the automatic gain selection is set to 1, the state machine 226 increases it to 2. The method 400 then returns to block 406 and gradually increases the current of the LED driver 222 again under the new automatic gain selection supplied to the analog front end 208.

Returning to decision block 410, if the automatic gain selection is at its maximum value, the method moves to block 414.

In block 414, the state machine 226 returns the system to the previous section The normal operating mode 304 described in FIG. 3 and awaiting further user input such as another calibration request.

Returning to decision block 408, if there is a successful detection, the method 400 moves to block 416.

In block 416, the state machine 226 outputs a calibration success signal.

In block 418, after a successful detection, the state machine 226 immediately reduces the reference level on the comparator by a pre-programmed amount (or performs a calibration such as in the least radiopaque portion of the target medium 108 in the slot 106 On time, increase the reference level) to generate an adjusted calibration reference level, and accordingly incorporate a detection buffer into the adjusted calibration reference level. In some embodiments, the pre-programmed amount that can be supplied by the user before calibration may be about 10% to 25% of the total amount of reference levels. For example, after a successful detection, the user can immediately instruct the state machine to reduce the reference level to reference level 2 of a total of 16 reference levels. The adjusted calibration reference level reduces the detection threshold and generates a detection buffer. As will be described below with reference to FIGS. 5A and 5B, the system is introduced to reduce the detection threshold due to changes such as changes in internal temperature, changes in the path of the target medium 108 through the groove 106, accumulation of dust on the surface of optical components, etc. The strength of false detection caused by changes in the system.

At block 420, the state machine 226 stores the value resulting from the successful calibration in the memory 214 for future use when the sensor assembly 100 is powered on. The stored values may include, for example, the LED driver level when a successful detection occurs (eg, 1000 possible power levels/steps among steps/step 650), automatic gain when a successful detection occurs Choice (for example, 3 possible 2 of the automatic gain selection levels), the adjusted calibration reference level (for example, reference level 7 of the 16 possible reference levels), and one used to indicate that the system has been successfully calibrated "True" flag.

In one embodiment, the LED driver level is selected from 1000 possible current levels, and 10-bit storage of memory 214 is used; the automatic gain selection can be selected from 3 possible levels, and 2 Bits for storage; select the adjusted calibration reference level from 16 possible levels and require 5 bits for storage; and select the calibration flag from two possible values and require 1 Bits for storage. After successful calibration and storing the calibration values in the memory 214, the method 400 may move to the aforementioned block 414, and the normal operating mode 304 is restored.

Referring now to FIG. 5A, there is shown a graph 500 of the power received on the light diode 104 as a percentage of the power driven to the LED 102. In this example, self-calibration with the method shown in FIG. 4 in the case where there is a more transmissive second portion 114 in the slot 106 has resulted in a set of calibration detection thresholds 502 without adjustment, so when the target medium 108 The second portion 114 is between the LED 102 and the photodiode 104, and the photodiode 104 receives 85% of the power driven to the LED 102. Occasionally, when the first portion 112 of the target medium 108 is between the LED 102 and the photodiode 104, 65% of the power driven to the LED 102 is received on the photodiode 104. Therefore, if the detection threshold is set to the minimum detection threshold 504, when the first portion 112 or the second portion 114 of the target medium 108 is between the LED 102 and the photodiode 104, the sensor combination 100 Both will record a successful detection, which is an undesirable result. Therefore, block 416 of method 400 The adjusted calibration reference level should be kept high enough to maintain a detection threshold above the minimum detection threshold 504.

Referring now to FIG. 5B, there is shown a graph 506 of the power received on the light diode 104 as a percentage of the power driven to the LED 102 after dust has accumulated in the lens of the LED 102. In this example, the debris on the lens causes the LED 102 to output 10% less power than the operation at the same drive current without dust on the lens. Therefore, the power received on the optical diode 104 is also reduced by about 10%. Therefore, if the calibration reference level is not adjusted (ie, remains at the detection threshold 502), the sensor combination 100 will not be able to detect the presence of the second portion 114 of the target medium 108, because the light two The power received on the pole body 104 will not exceed the detection threshold 502.

The reference level can be lowered so that the detection threshold is set to the detection threshold 508. In this case, the sensor combination 100 will be able to successfully detect the second portion 114 of the target medium 108, At the same time, the first portion 112 of the target medium 108 can be distinguished. However, because the detection threshold 508 will be lower than the minimum detection threshold 504, if debris is removed from the lens of the LED 102, it will cause undesirable detection of the first part 112 (ie, when sensing When the combination 100 considers that it is detecting the second part 114, it will detect the first part 112).

Alternatively, the reference level can be lowered to set the detection threshold to the adjusted calibration detection threshold 510. In this case, the sensor combination 100 will be able to successfully detect the target medium 108 The second portion 114 of the LED, and regardless of whether dust accumulates on the lens of the LED 102, can also distinguish the first portion 112 of the target medium 108 at the same time. In other words, the LED 102 Under a blur range of the lens, when the second portion 114 of the target medium 108 appears between the LED 102 and the photodiode 104, the sensor combination 100 will record the successful detection using the calibration detection threshold 510, Regardless of whether the lens is blurred or not, when the first portion 112 of the target medium 108 appears between the LED 102 and the photodiode 104, the sensor combination 100 will not record successful detection using the calibration detection threshold 510.

Therefore, the user can test the transmittance of the target medium 108 in order to determine the difference between the first portion 112 and the second portion 114, and the obtained information can be used to select the reference position to be applied to the block 416 of the method 400 The amount of reduction in the standard, so as to obtain an appropriate adjusted calibration reference level. For example, as shown in FIGS. 5A and 5B, if the first portion 112 is between the LED 102 and the photodiode 104, the amount of light detected on the photodiode 104 is greater than the second portion 114 is on the LED 102 When it is reduced by 20% between the photodiode 104 and the reference level is reduced by more than 20%, it will result in the above-mentioned reference to FIG. 5B, no matter which part of the target medium 108 is between the LED 102 and the photodiode. Between the polar bodies 104, the light detected on the photodiode 104 always exceeds the detection level.

It should be understood that in some embodiments, the first portion 112 of the target medium 108 may be more transparent or reflective than the second portion 114 of the target medium 108, and may therefore need to be reversed for detecting the target medium 108 Part of the conditions. The sensor combination 100 can be designed or calibrated to detect a decrease in opacity (ie, an increase in transmittance or transparency). For example, when the light received on the photodiode 104 increases above a detection threshold, the sensor combination 100 may indicate a successful detection.

The disclosed embodiments of the invention may include advantages over previous solutions. Common optical sensor combinations must be screened after manufacturing, because combinations that change too much during manufacturing cannot be used for sensitive applications. The combination of optical sensors that pass the screening must still be manually calibrated for use in a specific environment. In contrast, the optical sensor combination of the present application can be easily calibrated to deal with changes in manufacturing and usage environments.

Information and signals can be expressed using any of various techniques and techniques. For example, data, instructions, commands, information, signals, which may be mentioned in the previous description, can be represented by voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or any combination of the above Bits, symbols, and chips.

It can be general purpose processor, digital signal processor (DSP), application specific integrated circuit (ASIC), field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, Or any combination of the above items designed or designed to perform the functions described in the present invention is implemented or executed in a manner related to the disclosure of the present invention. A general-purpose processor may be a microprocessor, but in alternative embodiments, the processor may be any common processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (eg, a combination of a DSP and a microprocessor, a combination of multiple microprocessors, one or more microprocessors in conjunction with a DSP core A combination of, or any other such configuration).

100‧‧‧Optical sensor combination

102‧‧‧ LED

104‧‧‧ Photodiode

106‧‧‧slot

108‧‧‧Target medium

112‧‧‧Part 1

114‧‧‧Part Two

Claims (18)

A calibration method implemented by a controller using an optical detector system. The method includes: increasing the power level of the signal generator so that the power detected by the optical detector exceeds the initial detection threshold; After the optical detector exceeds the initial detection threshold, an indication of the first power level of the detector is stored in memory, the first power level corresponding to the detection exceeding the initial detection threshold The measured power; by applying the detection buffer from the memory to the initial detection threshold, adjusting the initial detection threshold to become the adjusted detection threshold; and the adjusted detection The threshold value is stored in the memory. A method as claimed in item 1 of the patent application, wherein the optical detector includes a photodetector and the signal generator includes a light emitting diode (LED). For example, the method of claim 1, wherein: adjusting the initial detection threshold value includes: reducing the detection threshold value. For example, the method of claim 1, wherein: adjusting the detection threshold value includes: increasing the detection threshold value. If the method of applying for item 1 of the patent scope further includes: Before the power level of the signal generator, the target medium is placed in the communication path between the signal generator and the detector. The method of claim 1 of the patent scope further includes: receiving a calibration signal instructing the controller to gradually increase the power level of the signal generator. The method of claim 1 of the patent scope further includes: setting the calibration flag in the memory after storing the indication of the first power level and the adjusted detection threshold. An optical detector system includes: a photon generation device for generating photons; a photon detection device for detecting photons; and a calibration device for calibrating the optical detector system, which calibrates the optical detector The system includes: by increasing the power level of the photon generating device, the power detected by the photon detecting device exceeds the initial detection threshold; storing the indication of the first power level of the photon generating device in memory In the body, the first power level corresponds to the detected power exceeding the initial detection threshold; by applying a detection buffer to the initial detection threshold, adjusting the initial detection threshold becomes an adjustment The detected threshold value; and the adjusted detection threshold value is stored in the memory. For example, the optical detector system in the 8th scope of patent application, in which the light The sub-generating device includes a light emitting diode (LED). For example, the optical detector system of claim 8 of the patent application, wherein the photon detection device includes a photodiode. Such as the optical detector system of claim 8 of the patent scope, the optical detector system is configured to detect the reflectance of the target medium in the communication path between the photon generating device and the photon detecting device . As in the optical detector system of claim 8, the optical detector system is configured to detect the transmittance of the target medium in the communication path between the photon generating device and the photon detecting device . A computing device includes: a memory containing a non-transitory machine-readable medium, the non-transitory machine-readable medium includes machine-executable code having stored therein for performing calibration Instructions for the method of the optical detector system; a processor coupled to the memory, the processor configured to execute the machine executable code for causing the processor to perform the following operations: gradually increase the output of the signal generator Detect that the power received by the optical sensor during the gradual increase of the output has exceeded the initial detection threshold; store the indication of the first level of the signal generator in the memory In this, the first level corresponds to the received power exceeding the initial detection threshold; by applying a compensation buffer to the initial detection threshold, an adjusted detection threshold is generated; and the adjustment The later detection threshold is stored in the memory. As in the computing device of claim 13, the processor is further configured to execute the machine-executable code for causing the processor to perform the following operations: receiving from the user includes one of a plurality of discrete levels A level of detection threshold setting signal; receiving a calibration signal from the user instructing the processor to gradually increase the output of the signal generator; and receiving a signal from the user including the compensation buffer Threshold change signal. As in the computing device of claim 13, the processor is further configured to execute the machine-executable code for causing the processor to perform the following operations: before gradually increasing the output, the analogy of the optical sensor Set the gain on the front-end amplifier; in response to determining that the output of the signal generator is gradually increased to the maximum output level before the initial detection threshold has been exceeded, increase the gain on the analog front-end amplifier; and The output level of the signal generator is increased so that the detected power at the optical sensor exceeds the initial detection threshold. A computing device as claimed in item 13 of the patent application, wherein the machine executable code is used to apply the compensation buffer amount, so that the initial detection threshold is reduced. A computing device as claimed in item 13 of the patent application, wherein the machine executable code is used to apply the compensation buffer amount so that the initial detection threshold is increased. A computing device as claimed in item 13 of the patent application, wherein the optical detector includes a photodetector, and the signal generator includes a light emitting diode (LED).

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