JPH071202B2 - UV detector - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultraviolet ray detecting device for detecting an ultraviolet ray irradiation amount, and more particularly, it can be used for detecting an ultraviolet ray irradiation amount having an intensity exceeding a predetermined intensity threshold value.

[0002]

2. Description of the Related Art There are several methods for detecting a specific wavelength of ultraviolet rays that are harmful to the human body. For example, one that uses a photoelectric tube having a metal photocathode with a large work function, one that uses an ultraviolet fluorescent substance and a photodiode that detects its fluorescence, and various types of glass filters or interference filters that allow only ultraviolet light to pass through and be detected by the photodiode There are things. Further, commercially available ultraviolet detectors, which show the current ultraviolet intensity using the above-mentioned sensor,
There is one that displays the amount of integrated ultraviolet rays. Many of these display only the numerical value or the integrated value. For example, "Japanese Patent Laid-Open No. 56-7403"
As described in "0", it is considered that an alarm is issued when the integrated value reaches a constant value.

[0003]

In such an ultraviolet ray detector, it is required to selectively detect only ultraviolet rays of a specific wavelength harmful to the human body, and various measures are considered for that purpose. At this time, when detecting the ultraviolet rays of the sun rays, wavelengths shorter than harmful ultraviolet rays are absorbed by ozone and the atmosphere, so there is no problem even if the sensitivity of the sensor is high in this wavelength range, but visible light, Since infrared rays and the like are 20 to 100 times stronger, it is necessary to remove them by some method. As a countermeasure against this, a filter having a strict long-wavelength removing characteristic is provided, or the above-mentioned photoelectric tube is used so that the sensor itself does not show sensitivity on the long-wavelength side.

However, when this measure is taken by using a filter, an expensive interference filter and a high-order stray light removing filter are combined to remove long wavelengths. This is because a filter generally does not pass only short wavelengths, resulting in a complicated structure and high cost.
Further, since the wavelength characteristic of the filter changes depending on the incident angle of light, the directivity becomes narrow.

On the other hand, when a countermeasure is taken by using a photocell, it does not show sensitivity to light having a wavelength longer than a specific wavelength determined by the work function of the photocathode, but a high-voltage circuit is required around the photocell so that the size is small. There is a limit to the development, portability, mechanical strength,
There are problems such as high cost.

As another countermeasure, there is an indirect method in which the amount of harmful ultraviolet rays is estimated by detecting visible short-wavelength light that is easy to detect instead of ultraviolet rays that are difficult to detect. However, the correlation between the intensity of the harmful ultraviolet rays and the visible short-wavelength light and the scattering property is not always good, and a rough amount of the harmful ultraviolet rays is measured.

Furthermore, since the sensitivity to ultraviolet rays varies from person to person, the harmful effects of ultraviolet rays on the human body are not uniform. Even in the same human body, there is a large difference in the degree of inflammation depending on the irradiation site even with the same amount of ultraviolet irradiation. As described above, the current ultraviolet detector has the above-mentioned practical inconvenience.

[0008]

In order to solve the above-mentioned problems, an ultraviolet detector of the present invention comprises a photodetector for converting incident ultraviolet light into a photocurrent having a current value according to its intensity, and a photocurrent. , Pulse output means for outputting pulses at a cycle corresponding to the intensity of ultraviolet rays, counting means (for example, counter IC) for counting the pulses, and display means (for example, liquid crystal) for displaying the count value of the counting means. The display device), and the pulse generation means is configured to integrate the photocurrent when the photocurrent exceeds a predetermined threshold current and convert the photocurrent into an integrated voltage, and the integrated voltage is determined by a preset voltage. When the voltage exceeds a predetermined voltage, the integrated charge of the integrator is discharged to output a pulse and the integrated voltage has a switch means for setting the initial value, and a set voltage generating means for generating a set voltage. To.

Further, the photodetector may be a semiconductor ultraviolet detector.

[0010]

In the ultraviolet detector of the present invention, the incident ultraviolet light is converted into a photocurrent according to the intensity by the photodetector. When the photocurrent exceeds a predetermined threshold current, the photocurrent is integrated and converted into an integrated voltage by the integrating means included in the pulse generating means, and the integrated voltage is set to a predetermined setting by the setting voltage generating means. When the voltage determined by the voltage is exceeded, the integrated charge of the integrating means is discharged by the switch means and a pulse is output, and at the same time, the integrated voltage is initialized. The photocurrent is then integrated again from this initial value,
When the voltage determined by the predetermined set voltage is exceeded,
Similarly, a pulse is output and the integrated voltage is set to the initial value. By repeating such an operation, the pulse is converted into a pulse having a cycle corresponding to the intensity of the ultraviolet rays. This pulse is counted by the counting means and becomes an integrated value, and this integrated value is displayed on the display means.

When the photodetection element is a semiconductor ultraviolet detection element, the structure is very simple, and it is not necessary to provide an ultraviolet transmission filter on the photodetection element when assembling the apparatus.

[0012]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows the configuration of the ultraviolet ray detection device of the present invention.

This ultraviolet detector comprises a light intensity-frequency conversion circuit (hereinafter referred to as an IF conversion circuit) 110, a counter 130 as counting means, a display drive circuit 140 and a liquid crystal display 150 as display means. A buzzer 160 as an alarm means and a program switch 120 that determines an operating condition as the buzzer are provided. I-F conversion circuit 11
0 converts ultraviolet rays into a pulse train having a frequency proportional to its intensity and outputs the pulse train to the counter 130. This circuit will be described in detail later. The program switch 120 determines the count value when the counter 130 outputs an alarm signal. The counter 130 is composed of a CMOS programmable counter or the like, counts the pulse train from the I-F conversion circuit 110 and outputs the count value to the display drive circuit 140, and when the count value determined by the program switch 120 reaches the buzzer 160. To generate an alarm signal. The buzzer 160 emits an alarm sound when an alarm signal is received. The display drive circuit 140 is an interface IC for displaying the count value from the counter 130 on the liquid crystal display 150.

The I-F conversion circuit 110 includes an ultraviolet sensor P.
As shown in FIG. 2, the pulse train D has a pulse width D and outputs a pulse train having a frequency corresponding to the intensity of the ultraviolet rays detected by the ultraviolet ray sensor PD. Here, the intensity of harmful ultraviolet rays is the intensity necessary to cause inflammation in the human body (for example, 0.1 MED (MI
NIMAL ERYTHEMA DOSE)) or less), the photoelectric capacitor is not integrated into the integrating capacitor C shown in FIG. When irradiated, the IF conversion circuit 110 does not perform pulse output operation.

The ultraviolet sensor PD selectively detects only ultraviolet rays (UVB) of a specific wavelength harmful to the human body,
For example, semiconductor UV sensor G361 manufactured by Hamamatsu Photonics KK
Four series are used. Since this UV sensor is made of a material (such as GaAsP) having a barrier potential that is essentially insensitive to visible light and infrared light, the burden of the bandpass characteristics of the optical filter can be reduced. The optical system is simple, compact and lightweight. This UV sensor, as shown in FIG. 3, is an ultraviolet ray (UVB) of a specific wavelength.
, It has a good spectral sensitivity characteristic, and has an extremely good linearity between the incident ultraviolet intensity and the output current. Further, it has the characteristics as shown in Table 1, and in particular, the dark current is extremely small (50 pAMax, actually smaller than 1 pA).

[0016]

[Table 1]

The I-F conversion circuit 110 is composed of, for example, the circuit shown in FIG. In this circuit, the pulse generating means is a capacitor C for integration and a PUT as a switch.
(PROGRAMABLE UNIJUNCTION TRANSISTOR), with load resistor R3 for converting output pulse to current / voltage, and PU
The set voltage generating means for determining the on / off condition of T is composed of bias voltage dividing resistors R1 and R2.
The output current Ish of the ultraviolet sensor PD generated by the irradiation of ultraviolet rays is charged in the integrating capacitor C, and P
It flows from the anode of the UT to the gate. This output current Ish
However, if the current is less than the current for turning on the PUT, the PUT remains off and the oscillation does not occur. However, the output current Ish is P
When the threshold value determined by the value of the gate resistance Rg (Rg = R1 // R2) of the UT is exceeded, that is, the condition of the equation (1) described below is satisfied, integration of photocurrent, that is, charging, and pulse output operation, that is, discharging The oscillation operation is repeated. This oscillation operation will be briefly described. When the output current Ish exceeds the above threshold value, the photocurrent is charged in the integrating capacitor, and the integrated voltage thereby becomes a value determined by the voltage Vg set by the voltage dividing resistors R1 and R2. Then, the PUT is turned on and an impulse-shaped pulse current flows from the capacitor C to discharge the electric charge charged in the capacitor C. This pulse current is converted into current / voltage by the load resistor R3, and is given to the counter 130 of FIG. 1 as a pulse.
At the same time, when the voltage of the integrating capacitor C drops and falls below the valley voltage, the PUT turns off and the output current Ish
Charging of the capacitor C is started. Then, when the integrated voltage of the capacitor C becomes higher than the gate voltage Vg (becomes the peak point voltage) again, the PUT is turned on and the pulse current flows from the capacitor C. Such an operation is repeated to oscillate. Here, the oscillation start condition is PUT
It is expressed as Ish> Vag / Rg (1) by using the gate-anode voltage Vag that turns on. The oscillation period t is expressed as t to C (Vg + Vag) / Ish (2), and the characteristic is that the oscillation frequency is linearly proportional to the ultraviolet intensity above the threshold value under the constant value of the capacitor C. is there.

PUT is represented by the equivalent circuit of FIG.
It is an extremely sensitive element and has the advantage of having a small leakage current. Further, in this circuit, the standoff ratio, the valley current, the peak current, and the like are determined by the constants of the circuit, so that the oscillation frequency, the consumption current, and the like can be designed with flexibility. For example, set the gate resistance Rg to 1
When it is set to 0 MΩ, Vag is about 0.1 V, and the oscillation starts when the output current Ish of the ultraviolet sensor PD is “Ish> 10 ⁻⁸ A”. Further, the current consumption of the circuit is several μA or less. Therefore, it can be driven by a battery, which is extremely convenient for a portable device.

Next, the operation of the ultraviolet detector of FIG. 1 will be described.

Of the light incident on this device, only ultraviolet rays (UVB) of a specific wavelength harmful to the human body are selectively detected by the ultraviolet ray sensor PD, and when a predetermined intensity threshold value is exceeded, the IF conversion circuit 110 , Ultraviolet rays are converted into a pulse train having a cycle corresponding to the intensity. The counter 130 counts this pulse train. When this count value reaches a value set by the user with the program switch 120 in advance, an alarm signal is generated to the buzzer 160, and the buzzer 160 sounds, whereby the preset limit of the amount of exposure to ultraviolet rays can be known. . In addition, the display drive circuit 14
When the count value is 0, the count value is displayed on the liquid crystal display 150, and the integrated value of ultraviolet rays, that is, the exposed amount is displayed as a numerical value or a bar graph.

The set value preset in the counter 130 by the program switch 120 can be freely determined according to individual differences and changes in skin sensitivity. Further, when the user of this ultraviolet detector applies sunscreen material (sunscreen), the program switch 120 sets a value corresponding to the SPF (SUN PROTECTION FACTOR) value written on the sunscreen material. It is possible to increase the apparent amount of UV exposure until the alarm is issued.

The present invention is not limited to the above-described embodiment, but various modifications can be made.

The counter 13 with the program switch 120
Instead of setting the count value at which 0 outputs an alarm signal, this value may be fixed and the value of the capacitor C may be changed.
The integrated value of ultraviolet rays, that is, the time until an alarm is issued can be changed. Further, the I-F conversion circuit is not limited to the one shown in FIG. 4, but a semiconductor UV sensor G3 manufactured by Hamamatsu Photonics.
Sensor circuit with OP amplifier configuration described in the 614 series catalog (detection output Vo = Rf × output current Ish)
Also, the pulse generating means may be configured by a comparator for comparing the detection output of this sensor circuit with a predetermined set voltage and a VF conversion circuit for converting the detection output into a square wave train when there is an output of the comparator. it can. In this case, there is a drawback that the power consumption is slightly increased.

In the IF conversion circuit of FIG. 4, the ultraviolet sensor PD may be provided via a buffer or a current amplifier for amplifying the output current. In addition, the voltage dividing resistors R1 and R
Instead of 2, the constant voltage source and the gate resistance Rg may be replaced. Further, instead of the load resistance R3 of the PUT, a pulse transformer may be used and the output may be taken out from this pulse transformer.

[0025]

As described above, according to the ultraviolet ray detecting apparatus of the present invention, when the threshold current is exceeded, the photocurrent is integrated, the pulse is output, and the integrated voltage is set to the initial value. Ultraviolet rays exceeding a predetermined intensity threshold value can be converted into pulses having a frequency according to the intensity, and by counting the pulses, it is possible to integrate ultraviolet rays having an intensity higher than the intensity to be measured. Furthermore, when the photodetector is a semiconductor ultraviolet detector, the ultraviolet detector can be made compact and portable, and the assembly process can be simplified.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an ultraviolet ray detection device of the present invention.

FIG. 2 is an ultraviolet intensity-frequency characteristic diagram of an I-F conversion circuit.

FIG. 3 is a characteristic diagram of an ultraviolet sensor.

FIG. 4 is a circuit diagram of an IF conversion circuit.

FIG. 5 is an equivalent circuit diagram of PUT.

[Explanation of symbols]

 110 ... IF conversion circuit 120 ... Program switch 130 ... Counter 140 ... Display drive circuit 150 ... Liquid crystal display 160 ... Buzzer C ... Capacitor PD ... UV sensor R1, R2 ... Dividing resistance R3 ... Load resistance PUT ... PUT

Claims (2)

[Claims] 1. A photodetector for converting incident ultraviolet light into a photocurrent having a current value according to its intensity, and a pulse for inputting the photocurrent and outputting a pulse at a cycle corresponding to the intensity of the ultraviolet light. The pulse generator includes a generating unit, a counting unit that counts the pulse, and a display unit that displays the count value of the counting unit.The pulse generating unit is configured to detect the photocurrent when the photocurrent exceeds a predetermined threshold current. Integrating means for integrating and converting the integrated voltage into an integrated voltage, and discharging the integrated charge of the integrating means when the integrated voltage exceeds a voltage determined by a predetermined set voltage, and outputting the pulse and the integrated voltage. An ultraviolet ray detection device, comprising: a switch means for setting the above-mentioned value as an initial value and a set voltage generation means for generating the set voltage. 2. The ultraviolet detector according to claim 1, wherein the photodetector is a semiconductor ultraviolet detector.