JP2006201669A - Optical scanner and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure (monitor) operating condition of optical beam scanning, to fulfill the requirement of a user who desires no stopping of the device nor processing of an abnormal mode only if writing operation is available even if operating abnormality is detected, and to facilitate a counter measure for a required maintenance. <P>SOLUTION: With an optical beam scanner ready to form an image, and with a beam passing time measured between two points on both sides of a photoreceptor, normal completion of the measurement is confirmed (S104). If the measurement is made normally, a pixel clock frequency is changed for the purpose of correcting image magnification. Even in the occurrence of abnormal measurement, image forming is performed without adjusting the image magnification (pre-setting) (S111). In this case, in spite of a possibility of causing deterioration of image quality, priority is given to the merit of uncorrected outputting rather than stopping of the operation. In the occurrence of the abnormal measurement, error information is stored (S109) and used for the analysis of the abnormality. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light beam scanning device and an image forming apparatus (for example, a laser printer, a digital copying machine, a facsimile machine, etc.) for writing an image using the light beam scanning device, and in particular, measures (monitors) a light beam scanning state. The present invention relates to an optical scanning apparatus and an image forming apparatus that perform a control operation corresponding to a case where an abnormality occurs in a detection result of a means for performing the above.

Conventionally, in an image forming apparatus such as a laser printer, a digital copying machine, and a facsimile machine, an image is written by a light beam scanning method. In this method, laser light whose lighting is controlled by image data (video signal) is periodically scanned in the main scanning direction on the surface to be scanned of a photoconductor to be image-written by a scanning means such as a polygon mirror. In this method, the scanning surface is moved in the sub-scanning direction and an image is written line by line on the photosensitive member.
In the beam scanning type writing system, the laser light generated by the light source is deflected by a polygon mirror that rotates at a constant angular velocity, and since the surface to be scanned is a plane, the surface to be scanned can be obtained using an fθ lens or the like. The light beam scanning system is configured so that the above scanning speed is constant. In this light beam scanning system, the state of the system changes over time, so when the device is used, the operating state of the light beam scanning is measured (monitored), and when the operating state changes, the write timing is changed accordingly. By adjusting the above, an appropriate image output can be obtained, or an abnormal operation can be detected based on the measurement result and the abnormal can be dealt with. In the case of abnormal operation, the apparatus is stopped to avoid low-quality image output and to eliminate the cause of the abnormality, such as adjustment or replacement of parts. It should be noted that in a light beam scanning system in which writing is performed with a plurality of beams (for example, a method of forming an image on one writing surface with a multi-beam or a method of forming an image of one color image with a tandem method) In order to obtain a reliable image output, the deviation of the scanning position between a plurality of beams becomes an object of abnormality detection.
Abnormal operation of the light beam scanning occurs due to various factors such as deterioration of the light source, and a recovery method according to the detection of the abnormality has been proposed conventionally, and the following Patent Documents 1 to 3 can be exemplified.

An image forming apparatus described in Japanese Patent Application Laid-Open No. 2003-89237 is obtained by detecting a light beam from a light source by a synchronization detection sensor provided on a scanning path in an image forming apparatus including a plurality of light sources. When the synchronization detection signal is abnormal, it is possible to select whether or not to stop the printing operation. When the synchronization detection signal is not stopped, it is possible to continue the image forming operation using only a normal light source.
An image forming apparatus described in Patent Document 2 (Japanese Patent Laid-Open No. 2003-266757) is an image forming apparatus that uses a multi-beam light source, and controls an abnormal operation mode based on a detection result of a light amount sensor of each light source of the multi-beam. I do. In the abnormal operation mode, it is possible to identify an abnormal light source and select an image forming process in an operation mode (multiple exposure mode, etc.) that can complement the abnormal light source, and suppress deterioration in image quality and productivity. I am doing so.
An image forming apparatus described in Patent Document 3 (Japanese Patent Laid-Open No. 2003-57908) relates to an image forming apparatus having a function of automatically correcting color misregistration (registration misregistration) at the time of multiplex (color) image formation. A detection image is formed, detected by a registration sensor, and a color misregistration correction operation for correcting the color misregistration from the obtained result is performed. By repeatedly performing this correction operation, even if the belt is soiled or scratched, it is possible to perform correction with high accuracy. If it is determined as abnormal as a result of repeated operations, an error is displayed and a service person is called so that maintenance can be performed, or correction of color misregistration is performed by using previous correction data. Make it possible.
JP 2003-89237 A JP 2003-266757 A JP 2003-57908 A

However, any of the image forming apparatuses described in Patent Documents 1 and 2 does not form an image using a light source in which an abnormality has been detected, and uses only a normal light source to form an image. Quality will deteriorate. In addition, when an image is formed only with a normal light source, Patent Document 1 reduces the scanning pitch to suppress deterioration, and Patent Document 2 causes the operation in the abnormal operation mode to be performed. Basically, it is unavoidable that the output image is changed and the output image changes.
Further, in the image forming apparatus described in Patent Document 3, the color misregistration correction is repeatedly performed. However, naturally, it takes much time, and the correction may not be performed normally even if time is taken. The decline in sex becomes a problem. If correction fails, the previous correction data is used. However, if the previous data is used without knowing the state of the current shift, the shift may increase. .
In addition, when such an abnormality is detected, if the machine is stopped in all cases and a service man call is made, the machine cannot be used until it is repaired. In this case, if there is a slight image degradation, there are some users who can tolerate, while there are rare cases where there is no problem for users who output many black-and-white images, and there are cases where abnormalities are falsely detected, without stopping the machine. For users who want to choose to output, usability is compromised.
The present invention has been made in view of the above-described problems of the prior art in an optical scanning apparatus and an image forming apparatus that perform writing by optical beam scanning. The problem to be solved is to measure (monitor) the operating state of optical beam scanning. ), Even if an operation abnormality is detected from the result, if the writing operation is possible, the apparatus is stopped or the process according to the operation mode at the time of abnormality (conventional techniques exemplified in Patent Documents 1 and 2 above, In other words, it is possible to perform an operation in response to a user's request that does not want to be referred to, and to handle a case requiring maintenance.

  According to the first aspect of the present invention, a light source that emits light in response to a drive signal, a light beam scanning unit that projects light generated by the light source onto a target surface as a scanning beam at a predetermined period, and an operation state of the light beam scanning are measured. And a control unit capable of controlling the operation of the light beam scanning according to the measurement result of the operation state measurement unit. The control unit is a measurement result of the operation state measurement unit. The optical beam scanning operation is detected by comparing with the predetermined abnormality occurrence condition, and when the abnormality is detected, the optical beam scanning is continued under the condition that the optical beam scanning is in an operating state. It is an optical scanning device characterized by managing the detection results of.

According to a second aspect of the present invention, in the optical scanning device according to the first aspect, the operation state measuring means detects the light beam at two predetermined positions on the optical scanning beam path, and detects the light beam. The time difference between the two positions obtained in this way is measured as a scanning speed of the light beam, and the control means detects a case where the scanning speed of the light beam is not normally measured as an abnormality. Is.
According to a third aspect of the present invention, in the optical scanning device according to the first or second aspect, the operating state measuring means is means for monitoring an operating current of a light emitting source, and the control means is a monitored light emitting source. When the operating current becomes a predetermined current value or more, it is detected as an abnormality.

According to a fourth aspect of the present invention, there is provided the apparatus according to any one of the first to third aspects, further comprising: a plurality of light sources, and means capable of varying a pitch between a plurality of light beam scanning lines as the light beam scanning means corresponding to each light source. In the described optical scanning device, the operation state measuring unit is a unit that measures the adjustment amount of the pitch between the light beam scanning lines, and the control unit normally measures the adjustment amount of the pitch between the light beam scanning lines. The case where it is not detected is detected as an abnormality.
According to a fifth aspect of the present invention, in the optical scanning device according to any one of the first to fourth aspects, the control device recognizes it as an effective abnormality detection result on condition that the abnormality is detected a plurality of times. This result is managed.

According to a sixth aspect of the present invention, there is provided the method according to any one of the first to fifth aspects, wherein a signal generated based on image data is used as a driving signal of the light source, thereby causing the light emitted from the light source to carry the image data. An image forming apparatus comprising: an optical scanning device; a photosensitive member having a target surface that is scanned with a light beam by the optical scanning device; and a unit that develops a latent image formed on the photosensitive member as a visualized image.
According to a seventh aspect of the present invention, there is provided the image according to the sixth aspect, wherein each of the optical scanning devices is provided corresponding to the constituent colors of the color image, and the color image is formed on the photosensitive member scanned by the light beam by each of the optical scanning devices. In the forming apparatus, the operation state measuring unit is a unit that measures a positional deviation amount between color images formed on the photosensitive member by each optical scanning device, and the control unit is a color formed on the photosensitive member. A feature is that a case where the measurement of the amount of positional deviation between images is not normally performed is detected as an abnormality.

(1) According to the first to fifth aspects of the invention, when an abnormal operation of the light beam scanning is detected, the light beam scanning is continued on the condition that the light beam scanning is in an operating state, and the abnormality detection result It is possible to respond to the user's request that does not want to stop the device or output in the operation mode at the time of abnormality, and also supports the case of abnormal operation that requires maintenance It becomes possible to do.
(2) In addition, when the measurement of the scanning speed of the light beam is not normally performed (Claim 2), when the operating current of the monitored light emitting source becomes a predetermined current value or more (Claim 3), and When the measurement of the amount of adjustment of the pitch between the light beam scanning lines is not normally performed in the multi-beam method (Claim 3), it is detected as an abnormal operation of the light beam scanning, and the effect of the above (1) is corresponding to each. It becomes possible to embody.
(3) In addition, on the condition that an abnormality has been detected multiple times, it is recognized as an effective anomaly detection result, and this result is managed to avoid false positives and eliminate accidental anomalies. Therefore, it is possible to improve the reliability of the detection result.
(4) Further, in the optical writing to the photosensitive member of the image forming apparatus, the effects of the inventions (1) to (3) are realized, and the performance as the image forming apparatus can be improved (claims). Item 6).
(5) Further, in an image forming apparatus that forms a color image on a photoconductor that is scanned with a light beam by an optical scanning device that corresponds to the constituent colors of the color image, the color image formed on the photoconductor A case where the measurement of the positional deviation amount is not normally performed is detected as an operation abnormality of the light beam scanning, and the effect of the above (1) can be realized corresponding to the abnormality detection. ).

An optical scanning apparatus and an image forming apparatus according to the present invention will be described based on the following embodiments. In the embodiments described below, a light beam scanning device that performs LD (laser diode) light writing in the main / sub scanning method according to the present invention, and a paper medium as an image written on a photoconductor by the light beam scanning device as a visualized image An example applied to the image forming apparatus formed in FIG.
FIG. 1 shows a schematic configuration of the image forming apparatus of the present embodiment.
A light beam scanning device 1 shown in FIG. 1 is a device that projects light generated by a light source LD of an LD unit (see FIG. 2 to be described later) onto a photoconductor 31 as a scanning surface at a predetermined cycle as a scanning beam. is there. The lighting of the LD is controlled by image data, and an image is written on the photoreceptor 31.
Although not shown in FIG. 1, the light beam from the LD is collimated by a collimator lens, passes through the cylinder lens, and is projected onto the reflecting surface of the polygon mirror 3 in FIG. The light beam is deflected by the polygon mirror 3 rotated by the polygon motor 3M, passes through the fθ lens 4, passes through the BTL 5, is reflected by the folding mirror 6, and scans on the photoreceptor 31. Here, the fθ lens 4 keeps the scanning speed on the surface to be scanned constant, and the BTL (barrel toroidal lens) focuses in the sub-scanning direction to collect light and correct the position in the sub-scanning direction (surface tilt). Etc.) It functions as a means.
Around the photoreceptor 31, a charger 36, a developing unit 32, a transfer unit 33, a cleaning unit 34, and a static eliminator 35 are provided, and recording is performed in the order of charging, exposure, development, and transfer, which is a normal electrophotographic process. An image is formed on a medium (recording paper or the like). The image formed on the recording paper is fixed on the recording paper by a fixing device (not shown).

2 shows a schematic configuration of an image forming control system and a light beam scanning device in the image forming apparatus (FIG. 1) (the same elements in FIGS. 1 and 2 are denoted by the same reference numerals). The image forming control system is synchronized with the rotation of the polygon mirror 3 that deflects the light beam from the LD unit 2 in order to write an image at a predetermined position on the image forming surface of the photoreceptor 31 in the light beam scanning device 1. Thus, it has a function of controlling the image writing timing by the LD.
A synchronization detection sensor (1) 8 and a synchronization detection sensor (2) 9 for detecting a scanning light beam are provided at both ends in the main scanning direction of the light beam scanning apparatus 1, and the light beam transmitted through the fθ lens 4 is a mirror (1 ) Reflected by 8M, mirror (2) 9M, condensed by lens (1) 8L, lens (2) 9L, and incident on synchronization detection sensor (1) 8 and synchronization detection sensor (2) 9 Has been.
When the light beam passes over both synchronization detection sensors, the synchronization detection sensor (1) 8 outputs a start side synchronization detection signal XDETP, and the synchronization detection sensor (2) 9 outputs an end side synchronization detection signal XEDETP. Each synchronization detection signal is input to the magnification error detector 17. The magnification error detection unit 17 measures the time from the falling edge of the start side synchronization detection signal XDETP to the falling edge of the end side synchronization detection signal XEDETP, compares it with the reference time difference, and a correction amount corresponding to the difference, that is, Then, correction data for changing the pixel clock frequency is generated and sent to the pixel clock generation unit 11 to correct the image magnification.

The pixel clock generator 11 includes a reference clock generator 12, a VCO (Voltage Controlled Oscillator) clock generator 13, and a phase-synchronized clock generator 14.
The magnification correction data from the magnification error detector 17 includes both the frequency setting value of the reference clock FREF generated by the reference clock generator 12 and the setting value of the frequency division ratio (N) in the PLL circuit constituting the VCO clock generator 13. Or one of them.
The start side synchronization detection signal XDETP from the synchronization detection sensor (1) 8 is sent to the magnification error detection unit 17 and to the pixel clock generation unit 11 at the same time. The pixel clock generation unit 11 generates a pixel clock PCLK synchronized with the start side synchronization detection signal XDETP and sends it to the LD control unit 2C and the synchronization detection lighting control unit 7.
The sync detection lighting control unit 7 first turns on the LD forced lighting signal BD to forcibly light the LD in order to detect the start side synchronization detection signal XDETP, but after detecting the start side synchronization detection signal XDETP, By using the start side synchronization detection signal XDETP and the pixel clock PCLK, an LD forced lighting signal BD for turning on the LD is generated at a timing at which the start side synchronization detection signal XDETP can be reliably detected without causing flare light. Send to. As for the detection of the end-side synchronization detection signal, the LD is turned on before the position 9 of the synchronization detection sensor (2) at the time of measurement so that XEDETP can be detected.
In the LD control unit 2C, the LD of the LD unit 2 is controlled to be turned on according to the synchronization detection forced lighting signal BD and the image signal synchronized with the pixel clock PCLK. The laser beam emitted from the LD unit 2 is deflected by the polygon mirror 3, passes through the fθ lens 4, and scans on the photoreceptor 31.
The polygon motor control unit 3C controls the polygon motor 3M at a specified rotational speed (constant speed) by a control signal from the printer control unit 10.

The VCO clock generator 13 that constitutes the pixel clock generator 11 will be described in more detail. FIG. 3 shows the internal configuration of the VCO clock generator 13.
As shown in FIG. 3, the VCO clock generator 13 constitutes a PLL (Phase-Locked Loop) circuit, and the reference clock signal FREF from the reference clock generator 12 and the VCLK output are output by a 1 / N divider 137. The signal divided by N is input to the phase comparator 131. The phase comparator 131 compares the phases of the falling edges of both signals and outputs the difference at a constant current. An output representing this difference is passed through an LPF (low-pass filter) 133 to remove unnecessary high frequency components and noise, and sent to the VCO 135. The VCO 135 outputs an oscillation frequency depending on the output of the LPF 133. Therefore, the frequency of VCLK can be varied by varying the frequency of FREF and the frequency division ratio N by correction data from the printer control unit 10.
The phase-synchronized clock generator 14 generates a pixel clock PCLK from VCLK set to a frequency that is eight times the pixel clock frequency. The pixel clock PCLK generated at this time is a clock synchronized with the start side synchronization detection signal XDETP. Thus, when the frequency of VCLK is changed, the frequency of the pixel clock PCLK is also changed accordingly.

FIG. 4 shows the internal configuration of the magnification error detector 17 of FIG. Since the magnification depends on the scanning speed of the light beam, the magnification error is a speed corresponding to the reference magnification (from the falling edge of the start-side synchronization detection signal XDETP due to the light beam at that speed to the rising edge of the end-side synchronization detection signal XEDETP. The time until the falling edge) is compared with the measured value between the two points.
The magnification error detection unit 17 includes a time difference counting unit 171 and a comparison control unit 172. The time difference counting unit 171 includes a counter 173 and a latch 175 as components.
When the time measurement between the two points is started, the counter 173 is cleared by the start side synchronization detection signal XDETP, counted up by the clock VCLK, and counted by the latch 175 at the falling edge of the end side synchronization detection signal XEDETP. Latch. The latched count value (time: T) is compared with a reference count value (time T0) corresponding to a preset reference magnification by the comparison control unit 172 to obtain the difference data (magnification error data), and the printer This is sent to the control unit 10.
The printer control unit 10 calculates correction data from the magnification error data and sends it to the pixel clock generation unit 11. The pixel clock generation unit 11 varies the frequency based on the correction data, and outputs the pixel clock PCLK having the corrected frequency to the LD control unit 2C, thereby correcting the image magnification. The reference time difference T0 needs to be experimentally measured in advance in a state where the image magnification is suitable.

By the way, in the above-described image formation control system (FIG. 2), in order to perform light beam scanning normally, the synchronization signal is detected by the above-described synchronization detection sensor, and the operation state of the light beam scanning is detected by various sensors. Although measurement (monitoring) is performed, measurement (monitoring) may not be performed normally for some reason, and an abnormality or error may occur.
In such a case, the occurrence of an abnormality is detected, and if the image forming operation is already in progress or the image forming operation can be started at that time, the apparatus may be stopped. Is possible.
However, if the detection of abnormality is a false detection, the output image will not deteriorate, and depending on the degree of abnormality, the result of continuing the operation as is can be accepted Therefore, as long as the image forming operation is possible, even if the occurrence of an abnormality is detected, the device will not be stopped, and output will not be performed in the operation mode at the time of abnormality. There is also a request that it is desirable to output continuously.
Actually, when the image deteriorates, the user can judge the image by viewing the output image without displaying the screen to notify the user of the abnormality or stopping the machine. You can call for repairs. If an abnormality is detected erroneously, it is better not to display it on the screen or stop the machine to notify the user of the abnormality.
In order to meet these demands, in the present invention, even if the occurrence of an abnormality is detected, if the image forming operation is possible at that time, the apparatus is not stopped and the image is kept as it is. It is designed to continue the formation operation and output, and to manage information about the abnormality that has occurred so that you can see later what kind of abnormality has occurred in the device, including erroneous detection. is there.

“Embodiment 1”
This embodiment corresponds to a case where the measurement of the scanning speed of the light beam is not performed normally. That is, as shown in the image forming control system (FIG. 2), the magnification error is detected in order to form an image at the reference magnification, but the magnification error is detected for some reason. An embodiment relating to image formation control that can cope with a case where an abnormality or an error occurs without time measurement between two points being performed normally will be described.
FIG. 5 is a flowchart of image formation control according to the present embodiment. The control flow of this example will be described below with reference to FIG.
Before starting the image forming operation, the printer control unit 10 operates the image forming control system (FIG. 2) to make adjustments for generating a pixel clock that enables image formation at a predetermined magnification. For this purpose, first, a pixel clock is set in the pixel clock generation unit 11 (step S101), the polygon motor control unit 3C is instructed to rotate the polygon mirror, and the LD control unit 3C is instructed to turn on the LD. (Step S102) The light beam scanning apparatus 1 is started up. The pixel clock setting at this time is set using a correction value stored in the printer control unit 10 at this point (usually, the value set immediately before is stored and used). The
When the light beam scanning device 1 is in an image forming operation ready state, time measurement between two points, that is, detection of a synchronization signal by the synchronization detection sensors (1) and (2) is started (step S103). Time measurement between two points is performed by the magnification error detection unit 17.

Next, it is confirmed whether or not the time measurement between two points has been normally completed (step S104). This confirmation may be determined from the time measurement result between two points, or may be performed based on the presence or absence of the start side synchronization detection signal XDETP and the end side synchronization detection signal XEDETP.
When the time measurement between two points is completed normally (step S104-YES), it is necessary to compare and correct the measurement result (time T) and the reference value (time T0) corresponding to a preset reference magnification. It is determined whether or not there is (step S105). This determination is determined by the correction resolution (correction accuracy) of the magnification. For example, correction is performed when an error of 1/2 or more of the correction resolution is detected.
When correction is performed, the correction value (correction data) is calculated, the LD is turned off (step S106), and then the correction data is set in the pixel clock generation unit 11 (reference clock FREF generated by the reference clock generation unit 12). Are set as the setting value of the frequency division ratio (N) in the PLL circuit constituting the VCO clock generation unit 13), thereby changing the frequency of the pixel clock and adjusting the magnification (step S 107).
Thereafter, the LD is turned on again (step S108), and the image forming operation (image writing operation) is started (step S111). Here, the LD is turned off once because there is a possibility that the LD light is irradiated onto the photosensitive member when performing the operation of changing the pixel clock frequency. . If correction is not performed, the image forming operation is started without changing the pixel clock setting.
After the image forming operation is finished, the LD is turned off and the polygon motor is also stopped (step S112).

On the other hand, when the time measurement between the two points is not normally performed (step S104-NO), the printer control unit 10 stores the error information (step S109). The error information is stored in a nonvolatile storage unit so that the information is not lost even when the power is turned off / on, and can be used as information for analyzing an abnormality in maintenance.
The content of the error information indicates the error determination reason, that is, the reason for determining the abnormality such that the time measurement result between two points is larger / smaller than the normal value range or the end side synchronization detection signal XEDETP is not output. , To be able to provide the information necessary to analyze the anomaly. The error information can be confirmed by a serviceman from an operation panel or the like, but a function that allows confirmation from a remote location using a communication means may be installed in the apparatus.
Furthermore, the following method can be employed for the error information storage process. That is, it is a method of recognizing an effective abnormality detection result on the condition that an abnormality has been detected a plurality of times and managing this result as error information. Depending on the result obtained by one abnormality detection operation, the history may be left, but there is a false detection or a single abnormality that is not an accidental abnormality that has no significant effect on the image. There is also. In such a case, a more stable result can be derived by storing the error as an error when it occurs multiple times.
Returning to the control flow, the error information is stored in step S109 and the time between the two points cannot be measured. Therefore, the correction is not performed and the image forming operation is started (step S111). In this case, since there is no correction (the pixel clock is not adjusted), the image forming operation is performed with the pixel clock set in step S101. Therefore, although there is a possibility that the image quality is deteriorated, as described above, priority is given to the merit by performing the uncorrected output rather than stopping the operation.

“Embodiment 2”
This embodiment corresponds to the deterioration that occurs in the LD of the light source in the image formation control system (FIG. 2) similar to that of the first embodiment. In other words, the LD of the LD unit 2 shown in the above-described image formation control system (FIG. 2) is monitored so as to obtain a predetermined light emission amount, but is deteriorated to a reference light amount or less due to a change with time. As the process proceeds, this monitoring result is output. An embodiment relating to image formation control that can cope with a case where an output for notifying the occurrence of such deterioration will be described.
FIG. 6 shows a configuration of an LD circuit used in the LD unit 2 of the image formation control system (FIG. 2). As shown in FIG. 6, the LD circuit includes an LD (laser diode) and a PD (photodiode). The LD control unit 2C controls the LD current Id so as to keep the PD monitor voltage Vm (proportional to the light emission amount of the LD) constant in order to light the LD with the light amount instructed by the printer control unit 10 (that is, APC operation: Auto power control is performed).
When changing the amount of light, Vm is changed by an instruction from the printer control unit 10, and the LD current Id is controlled so as to keep the set Vm constant. Further, the LD control unit 2C has a function of monitoring the LD current Id, and notifies the printer control unit 10 when the current value exceeds a preset current value. The monitoring result of the LD current value is used for determining the deterioration of the LD.

FIG. 7 is a flowchart of LD current value monitoring control according to the present embodiment. The LD current value monitoring control flow shown in FIG. 7 is always performed when the polygon motor rotates and the LD is lit. In the image forming control of the present embodiment, it is executed at the time of rotation of the polygon motor and LD lighting before starting the image forming operation (see step S101 in FIG. 5).
The control flow of this example will be described with reference to FIG. 7. First, the LD control unit 2C confirms that the polygon motor rotates and the LD is lit (step S201), and these operations can be confirmed. Then, it is determined whether or not the LD current value is equal to or greater than a specified value for determining deterioration (step S202).
As a result of the determination, if it is not equal to or more than the specified value (step S202-NO), the flow returns to the state at the start of the flow without doing anything and waits for the next LD lighting operation.
On the other hand, if the value is equal to or greater than the specified value, the LD has deteriorated. Therefore, when error information is notified to the printer control unit 10, the printer control unit 10 stores the error information (step S203). The flow ends and the control flow returns to the initial state. The error information is stored in a non-volatile storage unit so that the information will not be lost even if the power is turned OFF / ON, and the error information can be used as information for analyzing abnormalities in maintenance. Also write down the contents. Further, the error information can be confirmed by the service person from the operation panel or the like, but a function that can be confirmed from a remote place by using the communication means may be installed in the apparatus.
In response to a case where an output for informing the occurrence of deterioration as image formation control is generated, the occurrence of deterioration is managed as error information, and then the image forming operation is not stopped as in the first embodiment. Then, the image forming operation is started.

“Embodiment 3”
The present embodiment is an image formation control system (FIG. 2) similar to that of the first embodiment, but corresponds to the case where the measurement of the pitch adjustment amount between the light beam scanning lines is not normally performed in the multi-beam method. It is.
FIG. 8 shows a multi-beam optical beam scanning apparatus according to this embodiment.
As shown in FIG. 8, an LD unit 2 that selectively emits a light beam by being driven and modulated in accordance with image data is provided, and a cylinder lens is disposed on the optical path of the light beam emitted from the LD unit 2. And a polygon mirror 3 that is rotated at high speed by a motor (not shown) and deflected and scanned in a horizontal plane.
The polygon mirror 3 constitutes a deflecting means together with its rotational driving motor, and is formed in a regular hexagon in the illustrated example and has six reflecting surfaces. A scanning lens formed by a combination of the fθ lens 4 and the BTL 5 and a folding mirror 6 are sequentially arranged in front of the deflection scanning direction by the polygon mirror 3, and a drum-shaped photoconductor 31 serving as a surface to be scanned with the deflection scanning beam. It is set to form an image on the top. The BTL is used for focusing in the sub-scanning direction, and has a condensing function and a function of position correction (surface tilt etc.) in the sub-scanning direction.
Further, by receiving the light beam deflected by the polygon mirror 3 ahead of the image writing position in the non-image writing area in the main scanning direction, a synchronization detection signal for timing the writing start in the main scanning direction is output. A synchronization detection sensor 8 is provided.

The LD unit 2 is configured as a multi-beam light source capable of simultaneously emitting a plurality of light beams, in this example, two light beams. Two LDs (LD (1), LD (2)), which are individually controlled by the LD control unit, are provided as light sources, and two light beams emitted from the LD (1) and LD (2) are provided. The eaves are also combined and emitted so as to be emitted from one light source.
The beam combining principle of the LD unit 2 that generates these two beams will be described. Here, the image data is divided into odd-numbered rows and even-numbered rows, and the LD control unit turns on LD (1) and LD (2) according to the data. The light beam from the LD (1) is collimated by a collimating lens and enters the beam combining prism. The light beam from the LD (2) is collimated by the collimator lens, but is tilted by an angle x with respect to the light beam of the LD (1), and the light beam tilted by the angle x is a λ / 2 plate. Then, the light is incident on the beam combining prism. This beam combining prism has polarization, transmits the light beam of LD (1), and the light beam of LD (2) is 90 ° polarized so that it is reflected so that any light beam can be efficiently used. It is emitted from the beam combining prism. At the time of this emission, the two light beams pass through the λ / 4 plate, thereby bringing the polarization states of the light beams by the LD (1) and LD (2) closer to each other.
Also, the LD unit 2 itself constituted by these optical elements is provided so that the tilt angle can be varied by an angle θ around the optical axis of the light beam by the LD (1).
With this configuration, the light beam emitted from the LD (2) is inclined by an angle x and enters the beam combining prism, whereby the light beam from the LD (1) and the light beam from the LD (2) are shifted in the main scanning direction. Furthermore, the amount of deviation in the sub-scanning direction between the light beam by LD (1) and the light beam by LD (2) is determined by the inclination angle θ of the LD unit itself.
FIG. 9 is a diagram showing a positional relationship between two light beams generated by the above-described light beam scanning apparatus (FIG. 8).
As shown in FIG. 9, these two light beams are simultaneously scanned and detected by the same synchronization detection sensor 8. Therefore, the main scanning direction deviation amount Δx of the two light beams on the synchronization detection sensor 8 is less than zero. Bigger is better. That is, since LD (1) and LD (2) indicated by circles in FIG. 9 consider the spread of the beam, if Δx> 0, two beams can be detected by the single synchronous detection sensor 8. .
Therefore, by adjusting the angle x and the angle θ so that Pθ = 1 line pitch (42.3 μm at 600 dpi) and Δx> 0, the setting is made according to the intended condition.

FIG. 10 shows a schematic configuration of the image forming control system and the light beam scanning apparatus of the present embodiment. In addition, the same code | symbol is attached | subjected to the same element in FIG. 8 and FIG.
The image forming control system is basically the same as the configuration shown in FIG. 2, but a component is added for the two-beam light beam scanning method. That is, in order to write an image at a predetermined position on the image forming surface of the photosensitive member 31 by the light beams from the LD (1) and LD (2), the pitch switching control unit 19 and the synchronization signal separating unit 18 are added, The LD control unit 2C has a function of controlling the image writing timing corresponding to each of the two beams.
A synchronization detection sensor 8 for detecting a light beam is provided on the image writing side at the end in the main scanning direction of the light beam scanning device 1, and the light beam transmitted through the fθ lens 4 is reflected by the mirror 8M and condensed by the lens 8L. Thus, it is configured to enter the synchronization detection sensor 8.
The synchronization detection signal XDETP from the synchronization detection sensor 8 is sent to the synchronization signal separation unit 18 and separated into the synchronization signal XDETP1 of LD (1) and the synchronization signal XDETP2 of LD (2).
FIG. 11 shows an internal configuration of the synchronization signal separation unit 18 of FIG. 10, and FIG. 12 shows a timing chart of signals generated in the synchronization signal separation unit 18.
11 and 12, the sync signal separation operation will be described. First, when only the LD (1) is turned on, the detected XDETP is input to the sync signal separation unit 18 and configured by a gate circuit. It passes through the separating unit 183 as it is, and XDETP = XDETP1. XDETP1 is sent to a separation signal generator 181 composed of a counter and a comparator that are counted up by the pixel clock PCLK1, and a separation signal MASK is generated. As shown in FIG. 12, the MASK signal is a signal that is turned on at a predetermined timing from XDETP1 and turned off at a predetermined time, and there is no problem as long as XDETP1 and XDETP2 can be reliably separated.
By generating the MASK signal, LD (1) and LD (2) are turned on from the next scan, and the XDETP signal and the MASK signal are sent to the separation unit 183, whereby the XDETP signal can be separated into XDETP1 and XDETP2.

The separated XDETP1 and XDETP2 are sent to the pixel clock generator 11 and the sync detection lighting controller 7. The pixel clock generation unit 11 generates pixel clocks PCLK1 and PCLK2 synchronized with the synchronization detection signals XDETP1 and XDETP2, and sends them to the LD control unit 2C and the synchronization detection lighting control unit 7.
The sync detection lighting control unit 7 first turns on the LD forced lighting signal BD1 to forcibly light LD (1) in order to detect XDETP1, but after detecting XDETP1, it uses XDETP1 and the pixel clock PCLK1. Then, an LD forced lighting signal BD1 for lighting the LD (1) is generated at a timing at which XDETP1 can be reliably detected without causing flare light, and is sent to the LD controller 2C. Further, it turns on at a predetermined timing after detecting XDETP1, and generates an LD forcible lighting signal BD2 for turning on LD (2) for reliably detecting the synchronization detection signal XDETP2 of LD (2). And it sends to LD control part 2C.
The pixel clock generation unit 11 is the same as that in the image formation control system shown in FIG. 2 (in this example, the part relating to correction of the magnification error in FIG. 2 is omitted).
The LD control unit 2C controls the lighting of the LD in accordance with the synchronous detection forcible lighting signal and the image data (even-numbered rows and odd-numbered rows) synchronized with the pixel clocks PCLK1 and PCLK2.
The two laser beams emitted from the LD unit are deflected by the polygon mirror 3, pass through the fθ lens 4 and the like (BTL, folding mirror not shown), and scan on the photoreceptor 31.
The polygon motor control unit 3C controls the polygon motor 3M at a specified rotational speed (constant speed) by a control signal from the printer control unit 10.

  Further, a pitch switching control unit 19 that variably controls the beam pitches of LD (1) and LD (2) is provided, and the beam pitches of LD (1) and LD2 are varied according to instructions from the printer control unit 10. Although the variable means is not shown, for example, a pulse motor for varying the angle θ of the LD unit 2 shown in FIG. 8 is mounted on the LD unit 2 and the number of pulses for rotating the motor is varied. A configuration in which the angle θ changes can be employed. In this case, if the relationship between the number of pulses and the beam pitch is obtained in advance, when the beam pitch is actually set, the corresponding number of pulses is sent from the pitch switching control unit 19 to the motor. In order to judge whether or not the pitch switching operation is actually performed, a sensor for detecting the home position is provided in the LD unit 2, and the sensor is moved once to be detected by the sensor, and is stopped when the sensor is detected. Therefore, the number of pulses specified from the above can be moved to adjust the pitch.

In this embodiment, in the above-described two-beam image formation control system (FIG. 10), the measurement of the pitch adjustment amount between the light beam scanning lines is not normally performed, and it is possible to cope with an abnormality or an error. This is related to image formation control.
FIG. 13 is a flowchart of image formation control according to this embodiment. Hereinafter, the control flow of this example will be described with reference to FIG.
The image formation control flow shown in FIG. 13 is executed by the printer control unit 10 before the rotation of the polygon motor or the LD is turned on as an initial adjustment when the setting of the operation mode is changed.
First, the printer control unit 10 determines whether or not to perform a pitch switching operation (step S301). For example, when the current setting is a setting corresponding to an operation mode of 600 dpi and the setting is changed to an image output of 1200 dpi, a pitch switching operation is necessary to adjust the pitch between light beam scanning lines. . Note that this operation may always be performed regardless of the current state.
Here, when the pitch switching operation is not performed, the procedure proceeds to a procedure necessary for the image forming operation.

When the operation mode is changed and the pitch switching operation is performed, the pitch switching operation is executed (step S302), and then it is checked whether or not the pitch adjustment has been normally performed (step S303). This is because, as described above, an abnormality occurs in the sensor for detecting the position provided in the LD unit 2, for example, a case where the detection signal of the sensor is not output. It is possible to check by a method such as judging.
If there is no abnormality as a result of the check, the pixel clock is set (step S305), the polygon motor is rotated, the LD is turned on (step S306), and the image forming operation is started (step S307).
After the image forming operation is finished, the LD is turned off, the polygon motor is also stopped (step S308), and the control flow is finished.
On the other hand, if the pitch switching operation is not normally performed in step S303, there is a possibility that the pitch adjustment is not normally performed. Therefore, when the error information is notified to the printer control unit 10, the printer control unit 10 The error information is stored (step S304). The error information is stored in a non-volatile storage unit so that the information will not be lost even if the power is turned OFF / ON, and the error information can be used as information for analyzing abnormalities in maintenance. Also write down the contents. Further, the error information can be confirmed by the service person from the operation panel or the like, but a function that can be confirmed from a remote place by using the communication means may be installed in the apparatus.
When an abnormality is detected in the pitch switching operation, after performing the procedure for managing the error information, the image forming operation is performed without stopping the image forming operation as in the first and second embodiments. Therefore, the operation is performed according to the control flow from the setting of the pixel clock (step S305) to the end of the image forming operation (step S307).

“Embodiment 4”
In this embodiment, in order to form a color image, a color formed on the photoconductor in a so-called tandem image forming control system that scans the photoconductor with a light beam corresponding to the constituent colors of the color image. This corresponds to the case where the measurement of the amount of positional deviation between images is not performed normally.
FIG. 14 shows a schematic configuration of a 4-drum tandem type image forming apparatus according to the present embodiment.
The image forming apparatus shown in FIG. 14 corresponds to color constituent colors in order to form a color image in which four color images of yellow (Y), magenta (M), cyan (C), and black (BK) are superimposed. Four sets of image forming units (having a photosensitive member 31, a developing unit 32, a charger 37, a transfer unit 35, etc.) and four sets of light beam scanning devices 1 are provided.
A color image in which the four color images are superimposed by forming the first color image on the recording paper conveyed in the direction of the arrow by the transfer belt 33 and then transferring the second color, third color, and fourth color images in that order. Are formed on the recording paper, and the image on the recording paper is fixed by a fixing device (not shown).
The image forming unit for each color is provided with a charger 37, a developing unit 32, a transfer unit 35, a cleaning unit (not shown), and a static eliminator (not shown) around the photoreceptor 31. An image is formed on a recording medium (recording paper or the like) in the order of charging, exposure, development, and transfer, which are electrophotographic processes.

The light beam scanning device 1 has the same configuration as that of the first embodiment (see FIGS. 1 and 2), and the light beam from the LD that is controlled to be turned on by image data is output by a collimator lens (not shown). The beam is collimated and passes through a cylinder lens (not shown) and is projected onto the reflecting surface of the polygon mirror 3. The light beam is deflected by a polygon mirror 3 rotated by a polygon motor (not shown), passes through an fθ lens 4, passes through a BTL 5, is reflected by a folding mirror (not shown), and scans on the photoreceptor 31. Here, the fθ lens 4 makes the scanning speed constant on the surface to be scanned, and the BTL (barrel toroidal lens) 5 focuses in the sub-scanning direction, and condenses and corrects the position in the sub-scanning direction (inconvenient). This functions as a means.
In addition, a sensor (1) 41 and a sensor (2) 42 for detecting a positional deviation correction pattern between color images are provided. Sensors (1) 41 and (2) 42 are reflection-type optical sensors that detect misalignment correction patterns between color images formed on the transfer belt 33. This detection result is used to correct the image position shift in the main scanning direction and the sub-scanning direction between the colors and the image magnification in the main scanning direction.

FIG. 15 shows a schematic configuration of the image forming control system and the light beam scanning apparatus of the present embodiment. The same elements in FIGS. 14 and 15 are denoted by common reference numerals.
The image forming control system is basically the same as the configuration shown in FIG. 2, but has a configuration part for correcting misalignment of a 4-drum / tandem system. That is, the difference is that the sensor (1) 41 and the sensor (2) 42 are added, and the writing start position control unit 20 that controls the writing start position according to the result of the image position deviation correction operation.
The positional deviation correction pattern signal detected by the sensor (1) 41 and the sensor (2) 42 is sent to the printer control unit 10 to calculate the deviation amount (time) of each color with respect to BK. The calculated deviation amount is sent as data for correcting the writing start position in the main scanning direction and the sub-scanning direction to the writing start position control unit 20, so that the main scanning gate signal XLGATE and the sub-scanning gate signal XFGATE are Change the timing.
The printer control unit 10 receives the error data from the magnification error detection unit 17 and sends the frequency setting data to the pixel clock generation unit 11 to correct the image magnification in the main scanning direction. The frequency of is variable.

FIG. 16 shows an internal configuration of the writing start position control unit 20 in the image forming control system (FIG. 15) of the present embodiment.
The writing start position control unit 20 includes a main scanning line synchronization signal generation unit 23, a main scanning gate signal generation unit 27, and a sub scanning gate signal generation unit 25. The main scanning line synchronization signal generation unit 23 generates a signal XLSYNC for operating the main scanning counter 271 in the main scanning gate signal generation unit 27 and the sub scanning counter 251 in the sub scanning gate signal generation unit 25.
The main scanning gate signal generation unit 27 generates a signal XLGATE that determines the image signal capturing timing (image writing timing in the main scanning direction), and the sub scanning gate signal generation unit 25 performs the image signal capturing timing (sub scanning direction). Signal XFGATE is determined.
The main scanning gate signal generation unit 27 compares the main scanning counter 271 operating with XLSYNC and PCLK, the counter value with the correction data 1 from the printer control unit 10, and outputs the result, and the comparator 273 outputs the result. The gate signal generation unit 275 generates XLGATE from the comparison result.
The sub-scanning gate signal generation unit 25 compares the control signal from the printer control unit 10, the sub-scanning counter 251 operating with XLSYNC and PCLK, the counter value and the correction data 2 from the printer control unit 10, and outputs the result. And a gate signal generation unit 255 that generates XFGATE from the comparison result from the comparator 253.
The writing start position control unit 20 can correct the writing position in units of one cycle of the pixel clock PCLK for main scanning, that is, in units of one dot, and in sub scanning, in units of one cycle of XLSYNC, that is, in units of one line. .

FIG. 17 shows a buffer for sending image data to the image formation control system (FIG. 15).
A line memory 25 shown in FIG. 17 that functions as a buffer for image data fetched from the source is provided in the preceding stage of the image formation control system shown in FIG.
The line memory 25 is configured to output an image signal of image data captured from an external device such as a frame memory or a scanner at the timing of XFGATE in synchronization with PCLK only when XLGATE is 'L'. The output image signal is sent to the LD control unit 2C, and the LD is turned on at that timing.
Therefore, if the timing of XLGATE and XFGATE is changed, the timing of the image signal is also changed, and the image writing start position in the main scanning direction and the sub-scanning direction can be changed. The timings of XLGATE and XFGATE are determined by correction data set by the printer control unit 10 in the comparator 273 of the main scanning gate signal generation unit 27 and the comparator 253 of the sub scanning gate signal generation unit 25, respectively.
FIG. 18 is a timing chart of signals generated in the writing start position control unit 20.
As shown in FIG. 18, for main scanning, the counter 271 is reset by XLSYNC and counted up by PCLK, and the counter value becomes the correction data (in this case, “X”) set by the printer control unit 10. The comparison result is output from the comparator 273, and XLGATE is set to “L” (valid) by the gate signal generation unit 275. XLGATE is a signal that becomes 'L' by the image width in the main scanning direction.
For sub-scanning, counting up with XLSYNC is different from main scanning.

FIG. 19 shows a pattern for correcting misregistration between color images formed on the transfer belt.
As shown in FIG. 19, horizontal line and diagonal line images are formed as correction patterns on the transfer belt 33 (see FIG. 14) at a preset timing for each color (BK, C, M, Y). As the transfer belt 33 moves in the direction of the arrow (sub-scanning direction), the horizontal and oblique lines of each color are detected by the correction pattern sensor (1) 41 and the correction pattern sensor (2) 42, and are sent to the printer control unit 10. The amount of shift (time) of each color with respect to BK is calculated.
The detection timing is changed when the image position and the image magnification are shifted in the main scanning direction for the oblique line, and the detection timing is changed for the horizontal line when the image position is shifted in the sub-scanning direction.
Referring to FIG. 19, in the main scanning direction, on the correction pattern sensor (1) 41 side, the time from pattern BK1 to pattern BK2 is used as a reference, and the time is compared with the time from pattern C1 to pattern C2. The minute TBKC12 is obtained. On the correction pattern sensor (2) 42 side, the time from the pattern BK3 to the pattern BK4 is used as a reference, and the time from the pattern C3 to the pattern C4 is compared to obtain the deviation TBKC34. The magnification error of the cyan image with respect to the black image can be obtained as the difference 'TBKC34-TBKC12'.
Thereafter, an amount corresponding to the obtained magnification error is instructed to the pixel clock generation unit 11 as a correction amount, and the frequency of the pixel clock PCLK is varied to obtain the magnification based on the black image.
Then, the same correction pattern is formed by using the corrected pixel clock PCLK, and TBKC12 and TBKC34 are similarly obtained. Further, the main scanning deviation of the cyan image with respect to the black image can be obtained as '(TBKC34 + TBKC12) / 2'.
Thereafter, the main scanning deviation is instructed to the writing start position control unit 20 as a correction amount, and the writing start timing is changed in units of one cycle of the writing clock, thereby eliminating the main scanning deviation on the basis of the black image. it can.
For magenta and yellow, the main-scanning deviation of each color image can be eliminated by the same procedure as described above.
In the sub-scanning direction, assuming that the ideal time is Tc, the time from pattern BK1 to pattern C1 is TBKC1, and the time from pattern BK3 to pattern C3 is TBKC3, '((TBKC3 + TBKC1) / 2) -Tc' is the cyan image. A sub-scanning shift occurs with respect to the black image. Also in this case, the writing start position control unit 20 is instructed with the amount of sub-scanning deviation as a correction amount, and the writing start timing is varied in units of one line.
For magenta and yellow, the sub-scanning deviation of each color image can be eliminated by the same procedure as described above.
In the above, the example in which the detection of the magnification error and the detection of the main scanning deviation are performed in different patterns is shown. However, the correction of the magnification error and the correction of the main scanning position are obtained by obtaining the time change due to the magnification error correction. Can be performed in the same pattern.

In the present embodiment, in the image formation control system (FIG. 15) that performs the above-described tandem color image formation, the measurement of the amount of misregistration between color images formed on the photoconductor is not normally performed, and an abnormality or error is detected. The present invention relates to image formation control that can cope with the occurrence of the above.
FIG. 20 shows a control flow for correcting misregistration between color images according to this embodiment. The control flow shown in FIG. 20 is executed by the printer control unit 10 at a stage before starting the image forming operation.
The control flow of this example will be described with reference to FIG. 20. First, the printer control unit 10 sets correction data (step S401). The correction data set at this time is, for example, the correction values for the previous main scanning position, sub-scanning position, and main scanning magnification stored in the printer control unit 10. The determined data is set in the writing start position control unit 20 and the pixel clock generation unit 11 as an initial value.
Next, the polygon motor is rotated at a specified rotational speed, the LD is turned on, and the apparatus is started up so that image formation is possible (step S402). Thereafter, a misregistration correction pattern (see FIG. 19) between color images is formed on the transfer belt 33 (step S403).
Thereafter, the pattern formed on the transfer belt 33 is detected by the correction pattern sensor (1) 41 and the correction pattern sensor (2) 42 (step S404). At the time of this pattern detection, it is checked whether or not the detection was successful (step S405). For example, since the number of patterns to be detected is known in advance, it is possible to check whether or not the detection has been normally performed based on the number that can be detected.

If the pattern detection can be performed normally, the printer control unit 10 calculates the main scanning deviation amount, sub-scanning deviation amount, and main scanning magnification error amount with respect to the reference BK for each color based on the detection result. (Step S406).
Next, it is determined whether or not the deviation amount calculated in the previous stage is at a level that actually requires correction (step S407). This determination is performed, for example, by a correction resolution of 1 dot unit or 1 line unit, so that the correction is performed if the deviation amount is 1/2 dot or more, or 1/2 line or more. Is possible.
If the amount of deviation is at a level that requires correction, correction data (correction data 1, 2) instructed to the writing start position control unit 20 is calculated for each color based on the amount of deviation (step S408). . The calculated correction data is stored for use as setting data in the subsequent image forming operation (step S409).
Also, regarding the correction of the main scanning magnification, it is determined whether or not the detected magnification error is at a level that actually requires correction. This determination is also determined by the magnification correction resolution. The correction data for the image magnification is calculated as a set value of the frequency instructed to the pixel clock generator 11, and is stored for use in the image forming operation performed thereafter.
After executing the correction operation according to the above flow, the polygon motor is stopped and the LD is also turned off. At the time of image formation, XLGATE, XFGATE, and PCLK of each color are generated according to the stored setting value generated by this misalignment correction flow, and by using these signals, image misalignment and image magnification can be reduced. It is possible to output a corrected image.

If the misregistration correction pattern cannot be detected in step S405, the misregistration correction between the color images may not be performed normally. Therefore, the printer control unit 10 stores the error information, and Management is performed (step S411). Accordingly, the correction data is not updated. Even when such an abnormality occurs, the subsequent image forming operation is executed without being stopped. In this case, since the correction data is not updated, the previous data is set.
The error information is stored in a non-volatile storage unit so that the information will not be lost even if the power is turned OFF / ON, and the error information can be used as information for analyzing abnormalities in maintenance. Also write down the contents. Further, the error information can be confirmed by the service person from the operation panel or the like, but a function that can be confirmed from a remote place by using the communication means may be installed in the apparatus.
Note that when the detection of the magnification error and the detection of the main scanning deviation are performed in different patterns, this control flow is repeated twice.
In addition, it is conceivable that the detection of various abnormal operations in the light beam scanning shown in the above embodiments is performed in combination. In such a case, all the error information obtained as a result of the executed abnormality detection is stored and retained (for example, in order to correct the image magnification, the method and implementation by the two-point measurement of the first embodiment) Even in the case where both of the methods of detecting the misregistration correction pattern of the form 4 are performed, the respective detection results are left), so that the cause of the abnormality can be analyzed correctly.

1 shows a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 1 shows a schematic configuration of an image forming control system and a light beam scanning device of an image forming apparatus (FIG. 1). 2 shows an internal configuration of a VCO clock generator of a pixel clock generator (see FIG. 2). The internal structure of a magnification error detection part (refer FIG. 2) is shown. 5 is a flowchart of image formation control that can cope with a case where an abnormality occurs in the measurement of the scanning speed of the light beam. 2 shows an LD circuit configuration of an LD unit in an image formation control system (FIG. 2). The flowchart of the monitoring control of LD electric current value is shown. 1 shows a multi-beam type light beam scanning apparatus according to an embodiment of the present invention. The positional relationship between two light beams generated by the light beam scanning device (FIG. 8) is shown. 1 shows a schematic configuration of an image formation control system and a light beam scanning apparatus in a multi-beam scanning type image forming apparatus. The internal structure of a synchronizing signal separation part (refer FIG. 10) is shown. The timing chart of the signal which arises in a synchronous signal separation part is shown. 6 is a flowchart of image formation control that can cope with a case where an abnormality occurs in the measurement of the inter-scan line pitch adjustment amount. 1 shows a schematic configuration of a 4-drum tandem type image forming apparatus according to an embodiment of the present invention. 1 shows a schematic configuration of an image forming control system and a light beam scanning device in a 4-drum tandem type image forming apparatus. . The internal structure of the writing start position control part in an image formation control system (FIG. 15) is shown. A buffer for sending image data to the image formation control system (FIG. 15) is shown. 18 is a timing chart of signals generated in the writing start position control unit in the image formation control system (FIG. 15). 2 shows a pattern for correcting misregistration between color images formed on a transfer belt. The control flow of position shift correction between color images is shown.

Explanation of symbols

1 .... Light beam scanning device, 2 .... LD unit,
2C ・ ・ LD control unit, 3 ・ ・ Polygon mirror,
8. Synchronous sensor (1), 9. Synchronous sensor (2),
10 .. Printer control unit, 11 .... Pixel clock generation unit,
17 .. Magnification error detector, 18 .. Sync signal separator,
19 .. Pitch switching control unit 20.. Writing start position control unit
31..Photoconductor, 33..Transfer belt,
41 ··· Pattern sensor for correction (1), 42 ··· Pattern sensor for correction (2).

Claims (7)

  A light source that emits light in response to a drive signal, a light beam scanning unit that projects light generated by the light source onto a target surface as a scanning beam at a predetermined period, an operation state measurement unit that measures an operation state of the light beam scanning, An optical scanning device having a control unit capable of controlling the operation of light beam scanning according to a measurement result of the operation state measurement unit, wherein the control unit uses a measurement result obtained by the operation state measurement unit as a predetermined abnormality occurrence condition. Contrast is detected to detect abnormal operation of the light beam scanning, and when the abnormality is detected, the light beam scanning is continued on the condition that the light beam scanning is in an operating state, and the abnormality detection result is managed. An optical scanning device characterized by that.   2. The optical scanning device according to claim 1, wherein the operation state measurement unit detects a light beam at two predetermined locations on the optical scanning beam path and a time difference between the two locations obtained by detecting the light beam. Is a means for measuring the scanning speed of the light beam, and the control means detects that the measurement of the scanning speed of the light beam is not performed normally as an abnormality.   3. The optical scanning device according to claim 1, wherein the operating state measuring unit is a unit that monitors an operating current of the light emitting source, and the control unit is configured such that the operating current of the monitored light emitting source is a predetermined current. An optical scanning device that detects an abnormality when a value exceeds a value as an abnormality.   4. The optical scanning device according to claim 1, comprising a plurality of light sources, and means capable of changing a pitch between a plurality of light beam scanning lines as the light beam scanning means corresponding to each light source. 5. The operating state measuring means is a means for measuring the adjustment amount of the pitch between the light beam scanning lines, and the control means is abnormal when the measurement of the pitch adjustment amount between the light beam scanning lines is not normally performed. An optical scanning device characterized by detecting.   5. The optical scanning device according to claim 1, wherein the control device recognizes the abnormality as a valid abnormality detection result on condition that the abnormality is detected a plurality of times, and manages the result. An optical scanning device characterized by that.   The optical scanning device according to any one of claims 1 to 5, wherein a signal generated based on image data is used as a driving signal of the light source, thereby causing the light emitted from the light source to carry the image data, and the light. An image forming apparatus comprising: a photosensitive member having a target surface to be scanned with a light beam by a scanning device; and a means for developing a latent image formed on the photosensitive member as a visualized image.   7. The image forming apparatus according to claim 6, further comprising an optical scanning device corresponding to each constituent color of the color image, and forming a color image on a photoconductor scanned with a light beam by each optical scanning device. The measuring means is a means for measuring the amount of misregistration between color images formed on the photoconductor by each optical scanning device, and the control means is for measuring the amount of misalignment between color images formed on the photoconductor. An image forming apparatus, wherein a case where measurement is not normally performed is detected as an abnormality.

Images