JP3362404B2 - Image output device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to scanning a laser beam.
Laser printer or digital copying machine to output image information
The present invention relates to an image output device such as a device. [0002] 2. Description of the Related Art Conventionally, as this type of image output apparatus,
For example, there is one as shown in FIG. This image output device
Is a laser beam emitted from the semiconductor laser 100.
LB is converted to a rotating polygon mirror 1 through a collimator lens 101.
02 and the rotating polygon mirror 102.
The laser beam LB obtained is transmitted to the rotating polygon mirror 102
By being reflected by a mirror that moves with the roll
And the axis of the photosensitive drum 104 via the imaging lens 103.
Photoreceptor that has been scanned and exposed along the direction and is uniformly charged in advance
Forming an electrostatic latent image on the surface of the drum 104 according to image information
I do. Then, the photosensitive drum 104 is formed on the photosensitive drum 104.
Visualize electrostatic latent images using known electrophotographic processes
That are configured to record images
It is. [0003] At this time, in the above-mentioned image output device, the sense
To keep the writing position of the image on the optical drum 104 constant
Of the laser beam LB on the photosensitive drum 104
A beam for detecting a laser beam is placed at one end of the scanning path.
And a beam detector 105 for detection.
Laser beam LB in synchronization with the beam scanning timing
By starting the modulation according to the image signal of the photoreceptor
The writing position of the image on the drum 104 is now aligned.
ing. Image output using such a beam detector
The apparatus detects the laser beam LB as described above.
Is deflected by the rotating polygon mirror 102.
Laser beam LB is applied to one end of the photosensitive drum 104
When passing near the placed beam detector 105
First, a laser beam LB is emitted from the semiconductor laser 100.
It is controlled in such a manner. In such an image output device, the output device is
During normal operation, the beam detector 105
At predetermined intervals according to the scanning timing of the laser beam LB.
A frame detection signal is output. Therefore, the output interval of this beam detection signal is
By monitoring, the image output device is operating normally.
Can be confirmed. Thus, the beam
By monitoring the output interval of the detection signal, the image output device
To check if the device is working properly
Various technologies have been proposed as follows. For example, Japanese Patent Application Laid-Open No. Sho 60-213919 discloses
A photoreceptor, a means for generating a light beam, and the light beam
A modulating unit for modulating a system with recording information;
A scanning system for scanning the photoconductor with the light beam,
The light beam scanned by the scanning system is applied to the photosensitive member.
Detected at a predetermined scanning position prior to scanning the fixed scanning range
And determining a start time of the light beam modulation based on the recording information.
A first detector for obtaining a reference signal for
Therefore, the light beam to be scanned is detected by the first detector.
After that, except for the predetermined scanning range of the photoconductor,
Second detection in the scanning range where no
A technology provided with the above-described detector is disclosed. Further, Japanese Patent Application Laid-Open No. 60-8729 discloses that
Light generator for printing in electrostatic printing apparatus, and the light generator
Light collecting portion for collecting light from the device, and a mark collected by the light collecting portion
Character light is polarized according to the print signal.
For printing consisting of a polarizer that separates into ineffective light that does not contribute
In the optical system, the ineffective light polarized by the polarizer
A detector to be detected, and an output signal and a reference signal of the detector.
A technique of providing a comparison unit for comparison is disclosed. Further, Japanese Patent Application Laid-Open No. 51-93219 discloses
Is fixed on the recording medium by the beam modulated by the information
In a device that prints by scanning repeatedly in a cycle,
Beam detection means to detect that the
A step, and a beam detection output from the beam detection means is provided.
It detects that it has not arrived for a certain period of time and
A technique for detecting goodness is disclosed. In Japanese Patent Publication No. 3-48510,
Modulated by the recording signal by applying the recording signal
A beam generator for generating a focused beam;
Polarizes the beam generated by the beam and places it on the beam
A polarizer for irradiating, and a beam polarized by the polarizer
Beam detector for detecting whether or not light has reached a predetermined position
And beam detection output from the beam detector.
Marking the recording signal on the beam generator based on the signal.
A recording apparatus for performing a recording operation by adding
The signal output from the detector occurs within the specified allowable time zone
Determining means for determining whether or not the determination has been made;
Is a counting method for setting the predetermined allowable time zone.
Stage and detection for detecting the signal generated by the beam detector
Means, and wherein the counting means
The detection means outputs a signal when counting the time period.
If detected, the recording signal is detected based on the detection signal.
Signal to the beam generator and the counting
When the means has not counted the predetermined allowable time period.
When the detection means detects a signal, an error signal is generated.
A technique for outputting is disclosed. [0011] However, the above prior arts
In the case of (1), there are the following problems. Sand
That is, it is disclosed in the above-mentioned Japanese Patent Application Laid-Open No. Sho 60-213919.
In the case of technology, it is necessary to determine when to start modulating the light beam.
Other than the first detector that obtains the reference signal for
Laser beam is not originally transmitted except for the scanning range
Need to provide a second detector to detect in the scanning range
Yes, put this second detector together with a mirror etc. in a narrow place
Installation is difficult because it must be installed
With the increase in the number of parts and cost
There are points. Also disclosed in Japanese Patent Application Laid-Open No. 60-8729.
In the case of the technology, the ineffective light polarized by the polarizer is
Since it is necessary to provide a new detector to detect
The same as the technology disclosed in Japanese Unexamined Patent Publication No. 60-213919.
The installation is difficult and the number of parts increases,
There is a problem that the cost is high. Also, in this proposal
Such technology requires a light generator that continuously emits laser light.
Assuming that the light source itself is
Not applicable for direct on-off modulation
There is a problem. Further, Japanese Patent Application Laid-Open No. 51-93219 and
And Japanese Patent Publication No. 3-48510
The beam is not scanned properly for some reason.
Beam can be detected, but the beam is modulated
Failures that are continuously emitted without being detected
There is a problem that it cannot be known. In particular, the above-mentioned image output device is connected to a facsimile
When used for image output, the beam is modulated.
If the light is continuously emitted without being output,
This is because the image is completely blank or black
Failure to detect a failure is fatal and defective. Therefore, the present invention has been made to solve the above-mentioned problems of the prior art.
It was done to solve a point.
Rollers are difficult to install due to the increased number of beam detectors.
The cost is high and the beam is modulated
Failures that are continuously emitted without being detected
It is an object of the present invention to provide an image output device capable of performing such operations. [0016] Means for Solving the Problems The above-mentioned technical problems
In the image output device according to the present invention,
A light beam generator for generating a modulated light beam;
Deflects the light beam from the light beam generator of
And a beam deflector for scanning the beam.
Beam detector for detecting a directed light beam at a predetermined position
And the light beam in synchronization with the deflection operation of the beam deflector.
A modulation signal is supplied to the beam generator, and the modulated signal is supplied to the beam detector.
A first modulating means for irradiating the light beam,
Irradiation of the light beam by the modulating means to the beam detector
Therefore, the light beam is generated in synchronization with the detected timing.
A modulation signal corresponding to the image information to the
Providing a light beam modulated by
And an image output device for outputting an image.
AndDue to the first modulating means, the period differs from the normal period.
Periodically modulates the light beam at a predetermined cycle,
At a predetermined period different from the period, the light beam detector
Error detection to detect an error depending on whether the
KnowledgeAchieved by configuring to have
You. The beam deflector is, for example, a rotary polygon mirror.
And on the photoreceptor corresponding to each mirror surface of this rotating polygon mirror.
Is configured to scan once. And this beam
The light beam scanned by the deflector is at the beginning of each scan
Is set to pass over the beam detector. This and
If a light beam is emitted from the beam generator,
Detection signal is output from the beam detector and
If no light beam is emitted, the beam detection signal is
No output. In the present invention, when a device abnormality is confirmed, for example,
For example, once every two scans, the light beam passes over the beam detector
Before and after the timing of the beam generation
Is applied. Therefore, when the device is operating normally,
From the beam detector, for example, once every two scanning periods
A detection signal is output. When the device does not operate normally and the beam detector
When the light beam is generated continuously, one scan period
The beam detection signal is output once. At this time,
The means outputs an abnormality warning signal. [0021] According to the present invention, the first modulating means provides
To the beam generatorAt a predetermined cycle different from the normal cycleBi
And apply theThe abnormality detection means
At a predetermined period different from the normal period, the light beam detector
An abnormality is detected depending on whether or not the light beam is detected. [0022] BRIEF DESCRIPTION OF THE DRAWINGS FIG.
I will tell. FIG. 2 shows one embodiment of the image output apparatus according to the present invention.
It shows an example. In FIG. 2, reference numeral 1 denotes a semiconductor laser and its half.
Parallelizing laser beam LB emitted from conductor laser
Laser beam generator consisting of a collimating lens
Emitted from the laser beam generator 1.
Laser beam LB is deflected by beam deflector 2
Scanning exposure on the photosensitive drum 5 via the imaging lens 3
Is done. The beam deflector 2 is driven by a motor (not shown).
Is a mirror of a regular polyhedron driven to rotate in the direction of the arrow
It is composed of a polygon mirror. Further, the above-mentioned imaging lens 3
Is a lens having f-θ characteristics, and the beam deflector 2
The laser beam LB scanned by the photosensitive drum
This is for scanning the upper part at a constant speed along the axial direction. Further, at the scanning start end of the photosensitive drum 5,
Is a reflection mirror for guiding the laser beam LB to the beam detector 4.
Is provided, and the beam detector 4
The laser beam LB that scans the photosensitive drum 5 is detected.
It is. The surface of the photosensitive drum 4 is
After being uniformly charged by a charger not shown,
The laser beam LB controls the image information under the control of the control circuit 7.
A scanning exposure is performed according to the information, and an electrostatic latent image is formed. this
The electrostatic latent image formed on the surface of the photosensitive drum 4 is a known image.
Visualized by electrophotography process on recording paper
The image is transferred and fixed, and the image is recorded. At this time, the surface of the photosensitive drum 4
The exposed portion may be colored to form an image,
Also, the non-exposed area may be colored to form an image.
No. FIG. 1 shows the control of the image output apparatus according to this embodiment.
It shows a control circuit. In FIG. 1, reference numeral 10 denotes a reference for an image output operation.
A pixel clock generator for generating a pixel clock to be
Denotes a beam arranged at the scanning start end of the photosensitive drum 5.
The detector 11 receives the output from the pixel clock generator 10.
Pixel clock and beam output from the beam detector 4
Output the reference pixel clock by synchronizing with the
The phase locked loop circuit 12 includes the phase locked loop circuit 11 and a
Controller that controls a counter and a latch circuit
3 is a reference pixel clock output from the phase locked loop 11
The counter 14 counts the signal CLK.
Where the count value of the data 13 is stored in the reference value storage unit 15.
A magnitude comparator for comparing with a fixed upper limit, 16 is the above counter
13 is stored in the reference value storage unit 17 as a predetermined value.
The magnitude comparator for comparing with the lower limit value of
A latch circuit for latching the outputs of
9 is an abnormality warning signal in accordance with the output signal of the latch circuit 18.
An abnormal warning signal generating circuit that generates a signal
Lighting timing that controls the lighting timing of the timer generator 1
The control circuit 21 outputs the output of the lighting timing control circuit 20.
Signal from the host computer (not shown)
Or times to input the incoming image information signals
, 22 drives the semiconductor laser of the laser beam generator 1
Laser drive circuit 23 is connected to the laser drive circuit 22.
Semiconductor laser of the laser beam generator 1 driven by
Are respectively shown. In the figure, reference numeral 24 denotes the phase synchronization circuit 11
Divides the reference pixel clock output from it into 周期 cycle
A frequency divider 25 is provided between the output of the frequency divider 24 and the phase synchronization circuit 1.
A changeover switch for switching between 1 and output, 26 is phase-synchronized
Count a predetermined number of reference pixel clocks output from the circuit 11
A timing signal to input an image information signal
The image signal timing circuit that is generated
Reference numeral 25 denotes a portion which is controlled by a CPU (not shown) of the image output apparatus.
The switching is controlled at a fixed timing. Ma
In addition, the image signal timing circuit 26
Synchronized by output, one run each by switch 25
Or a period of two scanning periods. In the above configuration, the image according to this embodiment is
In the image output device, the laser beam generator is operated as follows.
An output abnormality of the semiconductor laser is detected. That is, this
In the image output device, as shown in FIG.
The semiconductor laser 23 of the laser beam generator 1
The laser beam LB emitted from the beam deflector 2
Therefore, it is deflected and runs on the photosensitive drum 5 according to the image information.
The image is output by the inspection and exposure. At this time, the image output device shown in FIG.
As the print operation starts (step
1) A scanner motor that rotationally drives the beam deflector 2
Start up (Step 2) and generate laser beam
Of the laser light amount of the semiconductor laser 23 of the heater 1
(Step 3), lighting timing for beam detection
Control of the optical unit (step 4), and
Execute the fault check operation of the That is, the lighting timing control circuit 20
Is, as shown in FIG.
A laser lighting signal is output to the driving circuit 22 to generate a laser beam.
The semiconductor laser 23 of the creature 1 is connected as shown in FIG.
Light up at a predetermined timing. At that time, changeover switch
25 is switched to the 1/2 frequency divider 24 side (step
5), lighting timing control circuit 20 generates laser beam
The timing for turning on the semiconductor laser 23 of the heater 1 is
Is set to の of the normal lighting timing.
The lighting timing of the semiconductor laser 23 is determined by beam deflection.
The laser beam LB deflected and scanned by the device 2 is
Of the beam detector 4 disposed at the end of the scanning path of the body drum 5
When passing through the vicinity, the area before and after the beam detector 4
The laser beam LB is emitted from the semiconductor laser 23 across
The semiconductor laser 2 is set as described above.
The timing to turn on 3 is 1/2 of the normal cycle
Therefore, the semiconductor laser 23 is located near the beam detector 4.
When passing through, as shown in FIG. 5, once every two times
Is set to emit the laser beam LB. Then, the semiconductor laser 23
When the beam LB is emitted, this laser beam LB
The beam is deflected and scanned by the beam deflector 2 and the laser beam L
B is a beam arranged at the scanning path end of the photosensitive drum 5
When passing through the vicinity of the detector 4, the beam detector 4
Is detected. From this beam detector 4, FIG.
As shown in (c), a beam detection signal is output. Next, the beam is detected by the beam detector 4.
Is checked (step 6). That is, from the pixel clock generator 10
Outputs a pixel clock as shown in FIG.
However, this pixel clock is, as shown in FIG.
Output from the beam detector 4 by the phase locked loop 11
Is synchronized with the rising edge of the beam detection signal
Output as a raw clock. This reference pixel clock
Is input to a counter 13 as shown in FIG.
The counter 13 counts as shown in FIG.
Is done. In FIG. 4C, the LSB is the lowest order.
Count data, MSB is the top count data
Each is shown. The counting operation by the counter 13 is as follows.
As shown in FIG. 4C, the beam detection signal was output.
Stops after the first rising of the reference pixel clock
Counting is performed by the falling edge of the next reference pixel clock.
Value is latched and the next reference pixel clock is
The rising edge of the clock clears the count value,
Again by the fall of the next reference pixel clock
The controller 12 starts the counting operation.
Is controlled. The count value of the counter 13 is shown in FIG.
As shown in FIG.
Is compared with the predetermined lower limit stored in
The predetermined value stored in the reference value storage unit 15 by the comparator 14
Is compared to the upper limit. The reference value storage unit 17 and the reference
The predetermined lower limit and the predetermined upper limit stored in the value storage unit 15
The value is such that the semiconductor laser 23 is normally on-off modulated,
Laser beam L deflected and scanned by beam deflector 2
B is a beam arranged at the scanning path end of the photosensitive drum 5
Time interval for passing through the vicinity of the detector 4 once every two times
Corresponds to the lower limit and the upper limit. Therefore, semiconductor
When the laser 23 is normally modulated on / off,
Laser beam LB is detected by beam detector 4
The count value of the counter 13 up to
It is set to fall between the value and the upper limit. Therefore, the magnitude comparators 16 and 14
The count value of the counter 13 compared by
As long as the body laser 23 is normally on-off modulated,
Always higher than the predetermined lower limit value stored in the quasi-value storage unit 17
The predetermined upper limit value stored in the reference value storage unit 15
Is always small. For this reason, the comparison result of the
The output which is the result is, as shown in FIG.
Has reached the predetermined lower limit value stored in the reference value storage unit 17.
At the stage, the signal becomes H level. On the other hand, the above large and small comparator
The output of the comparison result of No. 14 is as shown in FIG.
The predetermined value stored in the reference value storage unit 15
Since the signal does not reach the upper limit, the signal is always at the L level. So
The outputs of these magnitude comparators 14 and 16 are
As shown in FIG.
Latched at the latch timing of the counter 13. On the other hand, the semiconductor laser 23 operates normally.
It is always lit without on-off modulation
In this case, the semiconductor laser 23 is originally a beam detector.
When passing through the vicinity of No. 4, one every two times as shown in FIG.
The laser beam LB is emitted at a rate of
When the conductor laser 23 passes near the beam detector 4,
In this case, as shown by a broken line in FIG.
It will be emitted. Therefore, the counter 13
The value is １ ／ of the normal value, and compared by the size comparator 16.
Reaches the predetermined lower limit value stored in the reference value storage unit 17
The output of the magnitude comparator 16 is always at L level.
Signal. On the other hand, the output of the magnitude comparator 14 is the same.
The signal remains at the L level as shown in FIG.
The signal is input to the abnormality warning signal generation circuit 19 through the control circuit 8. On the other hand, the semiconductor laser 23 is normally turned on and off.
If it is not modulated and does not light at all,
Originally, the semiconductor laser 23 passes near the beam detector 4.
As shown in the figure, once every two
The semiconductor laser 2 to emit the laser beam LB.
When passing near the beam detector 4, the laser beam 3
The beam LB will not be emitted. Therefore, cow
The count value of the counter 13 becomes infinitely large, and
The predetermined value stored in the reference value storage unit 17 to be compared by the
Not only the lower limit value of, but also the reference value compared by the magnitude comparator 14
Exceeding a predetermined upper limit value stored in the storage unit 15;
Become. As a result, the outputs of the magnitude comparators 14 and 16 are
These also become H level signals, which are transmitted through the latch circuit 18.
Then, it is input to the abnormality warning signal generation circuit 19. Therefore, the abnormality warning signal generation circuit 19
Are output from the magnitude comparators 14 and 16, and the latch circuit 1
8 according to the state of the signal latched by the semiconductor laser 2.
It is determined whether or not No. 3 is normally modulated on / off.
Swelling. And the time interval of beam detection is predetermined
If the value is shorter than the range of the values, FIG. 4 (i) (j) (k)
As shown, it is determined that the semiconductor laser 23 is continuously turned on abnormally.
Output a printer stop signal to the CPU of the image output device
Stops the image output operation and displays a message to that effect.
(Step 7). At that time, an image output device
Is used for facsimile image output
Etc., so that the image information sent is not lost,
The image information is stored in the memory together with the printer stop operation described above.
It is desirable to perform an avoidance operation to remember. On the other hand, the abnormality warning signal generation circuit 19
When the beam detection time interval is longer than the specified range
Indicates that the semiconductor laser 23 does not light or the laser
Judgment of abnormal lighting such as deflector 2 not rotating etc.
Outputs a linter stop signal to the CPU of the image output device,
Output operation is stopped, and the fact is displayed on the display panel.
An operation such as indicating is performed (step 8). The abnormality warning signal generating circuit 19
When the beam detection time interval is within the specified range
Determines that the operation is normal and ends the abnormality check operation (step
9), switch the changeover switch 25 to the phase synchronization circuit 11 side
(Step 10), as shown in FIG.
An action is performed (step 11). This optical system abnormality check operation is performed, for example,
For example, as shown in FIG.
However, it may be performed at a predetermined timing other than the above.
Of course. Also, the changeover switch 25 is set to a normal lighting time.
If you return to the normal operation, the semiconductor laser
If the LED does not light up, monitor it using the same circuit
be able to. As described above, the lighting timing control circuit 20
A beam generation signal is applied to the beam generator 1 by
Deflected by the beam deflector 2 by the beam generator 1
Beam LB passes near the beam detector 4
A beam is generated only when it corresponds to twice the scanning interval
You. Then, the beam detector detects the laser beam.
The time interval of the counter 13 and the magnitude comparators 14 and 16
And by these magnitude comparators 14 and 16
Whether the measured value of the time interval measured within the specified range
Is detected by the abnormality warning signal generation circuit 19,
If the interval is not within the specified range, an abnormal warning signal
The generation circuit 19 outputs an abnormal signal. Therefore, it is necessary to increase the number of beam detectors.
Installation difficulties due to the increased number of beam detectors
There is no increase in performance and cost. Also, the beam is modulated
Failures that continue to be emitted without being
Deflected by a beam deflector 2 by a beam generator 1
Beam LB passes near the beam detector 4
Generate a beam only when it corresponds to twice the scanning interval
Thus, the counter 13 and the magnitude comparators 14, 1
6 can be detected. The count value of the counter 13 is
Allowed by comparing only the upper bits of counter 13
The range can be set arbitrarily. The counter 13 counts
Clock is slower than the pixel clock.
It does not matter. However, the high precision of the pixel clock level
By using the clock, the mode of the beam deflector 2 is
That the number of rotations of the motor can be checked at the same time.
There are advantages. It should be noted that the sequence of abnormality detection is based on image output.
The beam generation signal at this time
The beam passes through the beam detector 4 only once for inspection.
Apply beam generation signal to beam generator 1 before and after
I do. However, the present invention is not limited to this.
The beam is detected only once in the above multiple scans.
4 before and after the timing of passing over
It is of course possible to apply a frame generation signal. Further, according to the present invention, abnormality detection is performed.
In this case, the synchronization status of normal control is maintained.
Therefore, regardless of the state of the changeover switch 25,
Synchronous input of image signal enables abnormal detection during recording operation
Can be informed, and can respond quickly when an abnormality occurs.
In this case, jitter may occur, but anomalies are detected locally.
Practical use can make it less noticeable
This is not a problem. Select all white or all black lines
If abnormalities are detected, the image quality will be affected even during printing.
No abnormality can be detected. In this embodiment, a semiconductor laser is used.
However, using a gas laser with an acoustic deflection element or galvanometer
The present invention is also applicable to a device for
You. It should be noted that the abnormal operation test is performed only at the start of the recording operation.
When performing the image processing, the image signal generation circuit 26 is omitted, and
A timing signal for inputting an image signal from the controller 12
Can be generated. Also, the determination of whether or not there is an abnormality is made only once.
For checking multiple intervals instead of checking the interval between
Is it based on noise to prevent false detections?
Are also desirable. [0055] The present invention has the above-described structure and operation.
Installation difficulties due to the increase in beam detectors
And the cost is high, and the beam is modulated.
Failures that are continuously emitted without being detected.
Can be output while maintaining control system synchronization.
An image output device can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing one embodiment of a control circuit of an image output device according to the present invention. FIG. 2 is a configuration diagram showing an embodiment of an image output device according to the present invention. FIG. 3 is a flowchart showing the operation of an embodiment of the image output apparatus according to the present invention. FIGS. 4A to 4K are signal waveform diagrams respectively showing the operation of the control circuit. FIGS. 5A and 5B are signal waveform diagrams respectively showing a detection state at the time of abnormality. FIGS. 6A and 6B are signal waveform diagrams respectively showing a detection state in a normal state. FIG. 7 is an explanatory diagram showing the timing of abnormality detection. FIG. 8 is a configuration diagram showing a conventional image output device. [Description of Signs] 1 semiconductor laser, 2 beam deflector, 3 imaging lens, 4 beam detector, 10 pixel clock generator, 1
1 phase synchronization circuit, 12 controller, 13 counter, 14 magnitude comparator, 16 magnitude comparator, 18 latch circuit, 19 abnormality warning signal generation circuit, 20 lighting timing control circuit, 22 laser drive circuit.

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H04N 1/113 B41J 2/44 G02B 26/10 H04N 1/23 103

Claims (1)

(57) [Claim 1] A light beam generator for generating a light beam modulated in accordance with a modulation signal, and a light beam from the light beam generator is deflected to form a light beam on a photosensitive member. A beam deflector for scanning the beam deflector, a beam detector for detecting a light beam deflected by the beam deflector at a predetermined position, and a modulation signal to the light beam generator in synchronization with a deflection operation of the beam deflector. First modulating means for irradiating the beam detector with a modulated light beam; and generating the light beam in synchronization with the timing of detecting the light beam irradiation by the first modulating means by the beam detector. vessels giving a modulation signal corresponding to image information, a light beam modulated by the image information and a second modulation means for applying to said photosensitive member, an image output device for outputting an image, the first It is given by the modulation means, for a normal period different
Periodically modulates the light beam with a period of
At different predetermined periods, the light beam detector emits a light beam.
Abnormality detection means for detecting abnormality depending on whether or not to detect
An image output apparatus characterized by having a.