JPH11105343A - Image forming apparatus and copier - Google Patents

Abstract

(57) [Problem] To provide an image forming apparatus using multiple lasers, in which line omission is prevented even when a failure occurs in a certain laser and image formation can be continued. I do. An image forming apparatus for forming an image on an image carrier by guiding a laser beam light-modulated by an image signal from a laser light source using a plurality of lasers adjacent to each other and facing the image carrier. Failure detection means for detecting a failure of each of the plurality of lasers, and when the failure detection means detects a failure of a part of the plurality of lasers, switches the emission output intensity of the non-failed laser among the plurality of lasers to a higher stage Means,
When a part of the plurality of lasers fails, the potential area formed on the image carrier by the laser that has not failed is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus,
In particular, a laser beam light-modulated by an image signal from a laser light source is guided on an image bearing surface such as a photoreceptor or an electrostatic recording medium to form image information such as an electrostatic latent image on the surface. The present invention relates to an image forming apparatus suitable for a copying machine, a laser beam printer, a facsimile, etc.

[0002]

2. Description of the Related Art Conventionally, in this type of image forming apparatus, a laser chip composed of one laser and a PD sensor has been used for generating laser light, and a bias current source and a pulse current source have been used. By having two current sources, the emission characteristics of the laser are improved. In order to stabilize the laser emission, the laser emission at the time of image formation is fed back using the output signal from the PD sensor, and the pulse current amount is automatically controlled (hereinafter, APC (Au)
tomaric Power Control)).

Therefore, an image forming apparatus using a multi-laser composed of a plurality of lasers employs a configuration as shown in FIG. Laser chip 4 in FIG.
Reference numeral 4 denotes an internal configuration of the semiconductor laser 31 shown in FIG. 5, which is a twin laser including an A laser 42, a B laser 43, and a PD sensor 41. Reference numeral 47 denotes a bias current source of the A laser 42, 45 denotes a pulse current source of the A laser 42, and D of the image processing unit 58 as image data.
The light emission of the A laser 42 is controlled by a switch 57 that is turned on / off by a signal output from the ATA 1. The control of the emission of the B laser 43 is the same as the control of the A laser 42. DAT of the image processing unit 58 as image data
The light emission of the B laser 43 is controlled by a switch 56 that is turned ON / OFF by a signal output from A2.

The output signal of the PD sensor 41 is converted into a voltage signal by a current / voltage converter 49, input to a comparator 55 via an S / H circuit 51, and output to a pulse current source 45.
Control. The output signal of the PD sensor 41 that has passed through the current / voltage converter 49 is also input to the comparator 54 via the S / H circuit 50, and controls the pulse current source 46.
52 and 53 are target values for controlling the respective pulse current sources. Reference numeral 58 denotes an image processing unit for generating the image data, and reference numeral 59 denotes a system controller for controlling the image processing unit 58.

[0005]

FIG. 7 shows a sequence at the time of output of image data at the time of pull-in of feedback control of a multi-laser composed of two lasers using the conventional example. First, at the timing T1, the switch 56 is turned off to cause the B laser 43 to emit light, and further, the S / H circuit 50 is set to the sample state, and the pulse current amount ItB of the B laser 43 generated by the pulse current source 46 is controlled. APC of B laser 43
Is completed, and S / H immediately before the switch 56 is turned ON.
The circuit 50 is set in the hold state to hold the pulse current ItB. Next, at the timing T2, the switch 57 is turned off to cause the A laser 42 to emit light, and further, the S / H circuit 51 is set to the sample state, and the pulse current amount ItA of the A laser 42 generated by the pulse current source 45 is controlled. A of the laser 42
After the PC is completed, S
/ H circuit 51 is held to hold pulse current ItA. Next, as described later, when the BD light receiving unit 36 detects a BD, the BD light receiving unit 36 is ready to output image data, and the sequence described below is repeated every two lines.

At the timing T3, the APC of the A laser 42 is performed, and at the timing T4, the APC of the B laser 43 is performed similarly. Then, at timing T5, BD emission is performed to detect the scanning timing, and the image processing unit 58 outputs image data DATA1, DATA2 based on the timing at which the BD light receiving unit 36 receives the BD light.

In an image forming apparatus using a multi-laser (a plurality of lasers) having, for example, two laser light-emitting elements as in this conventional example, image data DATA1 and DATA2 are used.
When one of the plurality of lasers constituting the multi-laser fails at the time of output, an image in which a line to be scanned by the failed laser is missing is formed, so that normal image formation is continued. It was impossible.

Therefore, the present invention provides an image forming apparatus using a plurality of lasers, in which line omission is prevented even when a failure occurs in a certain laser, and image formation can be continued. The purpose is to:

[0009]

According to the present invention, there is provided an image forming apparatus, comprising: a laser beam modulated by an image signal from a laser light source using a plurality of lasers; In an image forming apparatus that forms an image on an image carrier, a failure detection unit that detects a failure of each of the plurality of lasers, wherein the failure detection unit detects a failure of a part of the plurality of lasers. Means for switching the emission output intensity of a non-failed laser out of the lasers to a higher stage, wherein a potential formed on the image carrier by the non-failed laser when a part of the plurality of lasers fails. It is characterized in that the area is increased.

Further, the image forming apparatus according to the present invention, in the above image forming apparatus, further comprises: means for switching a warning display according to a failure condition when the failure detecting means detects a failure; and switching control of the apparatus. Means.

Further, in the image forming apparatus according to the present invention, in the above-mentioned image forming apparatus, the modulation signal for driving the non-failed laser is transmitted when all of the plurality of lasers are not defective. And a means for calculating from a plurality of modulation signals for driving.

A copying machine according to the present invention includes the above-described image forming apparatus.

[Operation] According to the present invention, when a laser failure is detected in an image forming apparatus using a plurality of lasers, the emission output intensity of another laser that has not failed is switched to a higher level to change the image line. Omission is prevented, and image formation can be continued.

[0014]

FIG. 4 is a sectional view of an entire copying machine having an image processing apparatus to which the present invention is applied. The basic operation of the copying machine will be described with reference to FIG.

Documents stacked on a document feeder (not shown) are sequentially conveyed one by one onto a glass platen glass surface 2.
When the document is conveyed, the lamp of the scanner 3 is turned on, and the scanner unit 4 moves in the horizontal direction to irradiate the document. The reflected light of the document is focused by the lens 8 via the mirrors 5, 6, and 7, and then input to the image sensor unit. The image signal input to the image sensor unit 9 is directly or temporarily stored in an image memory (not shown), read out again, and input to the exposure control unit 10.

The exposure controller 10 emits a laser beam modulated by an image signal, and the laser beam that has passed through the optical system irradiates the photosensitive member 11 to form a latent image on the photosensitive member.

That is, referring to FIG. 5, which is a block diagram of the exposure control unit 10 shown in FIG.
The light beam emitted from 4 is made substantially collimated by a collimator lens 35 and a stop 32, has a predetermined beam diameter, and enters a rotary polygon mirror 33. Rotating polygon mirror 3
Numeral 3 rotates at a constant angular velocity in the direction indicated by the curved arrow. With this rotation, the incident light beam is reflected as a deflected beam that continuously changes its angle. The light that has become a deflected beam is condensed by the f-θ lens 34. On the other hand, the f-θ lens 34 simultaneously corrects the distortion so as to guarantee the temporal linearity of the scanning, so that the light beam is directed onto the photoconductor 11 as an image carrier in the direction indicated by a straight arrow in FIG. At the same speed. Writing of image data to the photoconductor 11 is performed by controlling the light amount of the semiconductor laser 31.

Referring back to FIG. 4, the latent image formed on the photoreceptor 11 by the irradiation light is developed into a toner image by the developing device 12 or 13. The transfer paper is conveyed from the transfer paper stacking unit 14 or 15 in synchronization with the latent image, and the developed toner image is transferred to the transfer paper in the transfer unit 16. After the transferred toner image is fixed on the transfer paper by the fixing unit 17, the transfer paper is discharged by the paper discharge unit 1.
8 to the outside of the apparatus.

FIG. 1 shows the configuration of a laser drive circuit for driving a semiconductor laser 44 used in such an image processing apparatus. This laser drive circuit is provided in the exposure control unit 10, and the same parts as those in the conventional example shown in FIG. The present embodiment differs from the conventional example shown in FIG. 6 in the configuration blocks in that a laser failure detection unit 84 that detects a laser failure when APC is performed on a laser and a target for switching the laser output intensity when a laser failure is detected. Values 73 and 75, switches 80 and 81, and display unit 85
This is the point that has been added.

The laser chip 44 shown in FIG.
3 shows the internal configuration of the semiconductor laser 44, and is a multi-laser composed of an A laser 42, a B laser 43, and a PD sensor 41. Reference numeral 47 denotes a bias current source of the A laser 42, and reference numeral 45 denotes a pulse current source of the A laser 42. The switch 57 is turned on / off by a signal output from the data processing unit 82 as image data.
Thus, the emission of the A laser 42 is controlled. The control of the emission of the B laser 43 is the same as the control of the A laser 42.
The light emission of the B laser 43 is controlled by a switch 56 that is turned ON / OFF by a signal output from DATA2 of the image processing unit 82 as image data.

The output signal of the PD sensor 41 is converted into a voltage signal by a current / voltage converter 49, input to a comparator 55 via an S / H circuit 51, and output to a pulse current source 45.
Control. The output signal of the PD sensor 41 that has passed through the current / voltage converter 49 is also input to the comparator 54 via the S / H circuit 50, and controls the pulse current source 46.
Each of 72 and 74 is a pulse current source 45 in a normal state,
Each of 46 is a target value for control, and 73 and 75 are target values for switching the laser output intensity when the laser failure detection unit 84 detects a laser failure. Target value 7
The values of 3 and 75 are set to, for example, twice the target values 72 and 74. 82, an image processing unit for generating the image data; 83, a system controller for controlling the image processing unit 82; 84, a laser failure detection unit;
Output signal of PD sensor 41 and target value Vref1 during PC
1 (reference numeral 74) and Vref21 (reference numeral 72) to detect a failure of the laser A42 or the laser B43. When each failure is detected, the image processing unit 82 outputs trouble detection signals trouble1 and trouble2.
Send. Trouble1 or tr which is a failure detection signal
The image processing unit 82 which has received the output signal "ouble2" outputs the signal ref1 or the signal ref2, switches the target value for controlling the pulse current source of the non-failed laser, and outputs two-line data to the non-failed laser. Convert to one line and send. In addition, the signal trouble1 or the signal trouble1
The image processing unit 82 receiving le2 sends a signal to the system controller 83 to cause the display unit 85 to display that the resolution can be reduced and the image formation can be continued. When receiving the signals trouble1 and trouble2, the image processing unit 82 sends a signal for displaying on the display unit 85 that image formation is impossible to the system controller 83. Also, the system controller 8
3 takes measures such as stopping the image forming operation.

Next, the principle of this embodiment will be described with reference to an operation example in the case where the B laser fails.

FIG. 3 shows a sequence when the feedback control is performed and when image data is output. First, at timing T11
The switch 56 is turned off to cause the B laser 43 to emit light. At the time of APC of the B laser 43, the laser failure detection unit 84 detects the failure of the B laser at the timing T12 and troubles.
The le2 signal is output to the image processing unit 82. Upon receiving this, the image processing unit 82 outputs ref1, which causes the switch 80 to switch from Vref21 (reference numeral 72) to Vref22.
(Reference numeral 73), and the target value of the A laser is changed.

Next, APC of the A laser 42 is performed. That is, the switch 57 is turned off at the timing T14, and the A laser 42 emits light. APC for A Laser 42
Is completed, the pulse current of the pulse current source 45 of the A laser 42 is held, and the image data can be output. The sequence described below is repeated every two lines.

At timing T15, the APC of the A laser 42
I do. At timing T16, the A laser emits light to irradiate the BD light receiving unit 36, and outputs image data based on the light receiving timing at the BD light receiving unit 36.

It should be noted that the signal output from DATA1 and the signal output from DATA2 when there is no failure are averaged after being subjected to timing correction for adjusting the timing when the photosensitive member 6 is irradiated, and output from DATA1. May be.

By adopting such a configuration, when the laser failure detecting section 84 detects a laser failure, the target value of the output intensity of the laser which has not failed is switched to increase the output intensity, thereby making it possible to form a latent image at the time of forming a latent image. The potential area formed on the image carrier can be increased. Therefore, two lines of latent images can be formed by scanning one line.

When the laser A is out of order,
This can be detected at the time of APC starting at timing T15, but after detection, the target value of the B laser may be switched to 73 and APC for the B laser may be performed again.

At this time, the image processing section 82 has the configuration shown in FIG. When a laser failure occurs, the trouble signal is received, the signal processing unit 90 converts the data of two lines into one line, and switches switches 92 and 94 to send a signal to the laser which has not failed, and switches switches 91 and 93. The process of shutting off the signal for the failed laser is performed. FIG. 2 shows the switch positions when the two lasers have not failed. For example, if the B laser 43 breaks down, the switch 92 switches down,
The switch 93 also switches to the lower side.

[0030]

As described above, according to the present invention, in an image forming apparatus using a plurality of lasers, when a laser failure occurs, line omission of an image can be prevented and image formation can be continued.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a multi-laser driving circuit according to an embodiment of the present invention.

FIG. 2 is a block diagram of an image switching unit in the image processing unit shown in FIG. 1 according to the embodiment of the present invention.

FIG. 3 is a timing chart showing operation timings of the multi-laser drive circuit according to the embodiment of the present invention at the time of APC and at the time of outputting image data.

FIG. 4 is a cross-sectional view illustrating a configuration of a copying machine including an image forming apparatus according to the present invention and a conventional example.

5 is a configuration diagram of an optical system in an exposure control unit shown in FIG. 4 according to the present invention and a conventional example.

FIG. 6 is a circuit diagram showing a configuration of a multi-laser drive circuit in a conventional example.

FIG. 7 shows a conventional multi-laser drive circuit APC.
6 is a timing chart showing operation timings at the time of outputting image data.

[Explanation of symbols]

 41 PD sensor 42 A laser 43 B laser 44 Laser chip 45, 46 Pulse current source 49 Current / voltage converter 50, 51 S / H circuit 54, 55 Comparator 72, 73, 74, 75 Target value 82 Image processing unit 83 System controller 84 Laser failure detection unit 85 Display unit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuharu Kaji 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Isamu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inside the corporation

Claims (4)

[Claims] 1. An image forming apparatus for forming an image on an image carrier by guiding a laser beam light-modulated by an image signal from a laser light source using a plurality of lasers adjacently to an image carrier. Failure detection means for detecting a failure of each of the plurality of lasers; emission output intensity of a non-failed laser among the plurality of lasers when the failure detection means detects a failure of a part of the plurality of lasers Means for switching to a higher stage, wherein when a part of the plurality of lasers fails, the potential area formed on the image carrier by the non-failed laser is increased. . 2. The image forming apparatus according to claim 1, further comprising: a unit that switches a warning display according to a failure condition when the failure detection unit detects a failure; and a unit that switches control of the device. An image forming apparatus comprising: Means for calculating a modulation signal for driving the non-faulty laser from a plurality of modulation signals for driving the plurality of lasers when all of the plurality of lasers are not faulty. The image forming apparatus according to claim 1, wherein: 4. A copying machine comprising the image forming apparatus according to claim 1.