Image forming apparatus

Abstract

To solve the problem in which: as a data transfer method in a printing system in recent years, a method for serializing image data in a transmitting device that transmits data and transferring the image data at high speed, is known; in the above-described communication technique, a recovery circuit does not restore a clock signal at a predetermined frequency due to the influence of noise, and conversion of serial data into parallel data may be suspended; and especially, when conversion of image data indicating turn-off of a light emitting element provided on the final line of the image data is suspended, the light emitting element is not turned on, and a photoconductor drum may be excessively exposed.SOLUTION: An image forming apparatus transmits first turn-off image data indicating that a plurality of light emitting units is turned off after transmission of image data of one page, and transmits second turn-off image data indicating that the plurality of light emitting units is turned off after transmission of the first turn-off image data.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] Image forming apparatus [Background technology]

[0002] In electrophotographic printers, a commonly known method is to expose a photosensitive drum to light using an exposure head that uses light-emitting elements such as LEDs or organic EL elements to form a latent image.

[0003] Among the light-emitting elements used in exposure heads of this type are hold-type light-emitting elements that continue to emit light once they start emitting light until they are turned off, and these light-emitting elements require control to turn them off when exposure is complete.In Patent Document 1, the last line of the image to be exposed is determined, and image data instructing the light-emitting element to be turned off after the last line is added, thereby controlling the light-emitting element to go into a non-light-emitting state.

[0004] Incidentally, a method for transferring data in recent printing systems is known in which image data is serialized on the transmitting device side that transmits the data and then transferred at high speed. For example, Patent Document 2 discloses a configuration in which image data generated by an image processing controller for controlling the light emission of light-emitting elements is converted from parallel to serial and sent to an exposure head driver via a data communication unit that transmits and receives the data.

[0005] When performing high-speed serial communication, a clock-embedded serial communication technique is known in which image data and a clock are superimposed on each other and transmitted in the same serial signal in order to reduce the number of signal wirings.

[0006] A serial data receiving device has a recovery circuit for recovering a clock signal superimposed on the serial data, and the serial data is converted into parallel data based on the recovered clock signal. In such communication technology, the recovery circuit may not recover the clock signal of the specified frequency due to the influence of noise or other factors, and the conversion of the serial data into parallel data may be interrupted. In this case, the recovery circuit notifies the transmitting device that the clock signal of the specified frequency has not been recovered, and the transmitting device retransmits the remaining serial data. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-142425 [Patent Document 2] Japanese Patent Application Publication No. 2019-217654 Summary of the Invention [Problem to be solved by the invention]

[0008] In the above-mentioned communication technology, there are cases where the recovery circuit does not recover a clock signal of a predetermined frequency due to the influence of noise or the like, and the conversion of serial data to parallel data is interrupted.

[0009] In particular, if the conversion of image data indicating the turning off of light emitting elements given to the last line of image data is interrupted, the light emitting elements may not be turned off, and the photosensitive drum may be overexposed.

[0010] In view of the above-mentioned problems, an object of the present invention is to reduce the risk of overexposure of a photosensitive drum in an image forming apparatus that transmits image data using serial communication. [Means for solving the problem]

[0011] The image forming apparatus according to the present invention comprises: A rotating photoreceptor; an exposure head that emits light to expose the photosensitive member and has a plurality of light-emitting units arranged along the rotation axis of the photosensitive member; a controller that outputs image data for controlling turning on and off the plurality of light-emitting units, the controller outputting first lights-out image data indicating that the plurality of light-emitting units are to be turned off after transmitting the image data for one page, and outputting second lights-out image data indicating that the plurality of light-emitting units are to be turned off after outputting the first lights-out image data; a driver that drives the plurality of light-emitting units based on the image data; The present invention is characterized by comprising: [Effects of the Invention]

[0012] According to the present invention, in an image forming apparatus that transmits image data using serial communication, the risk of the photosensitive drum being overexposed can be reduced. [Brief explanation of the drawings]

[0013] [Figure 1] Configuration diagram of an image forming apparatus [Figure 2] Photosensitive drum and exposure head arrangement diagram [Figure 3] Printed circuit board configuration diagram [Figure 4] Image controller and printed circuit board block diagram [Figure 5] Timing chart for signals controlling the light-emitting element driving unit [Figure 6] Flowchart showing job execution process control [Figure 7] Flowchart showing the processing flow when unlocking is detected [Figure 8] Image formation operation concept diagram [Figure 9] Block diagram of light-emitting element driver [Figure 10] Analog block diagram [Figure 11] Drive unit diagram DETAILED DESCRIPTION OF THE INVENTION

[0014] [Example 1] Overall configuration of the image forming device The electrophotographic image forming apparatus of this embodiment will be briefly described. The overall configuration of the apparatus is shown in Figure 1. This image forming apparatus is composed of a scanner unit 100, an image creating unit 103, a fixing unit 104, a paper feed / transport unit 105, and a printer control unit (not shown) that controls these units.

[0015] The scanner unit 100 illuminates a document placed on a platen, optically reads the document image, and converts the image into an electrical signal to create image data. The image-creating unit 103 rotates a photosensitive drum 102 around its axis of rotation, and charges the photosensitive drum 102 with a charger 107. The exposure head 106 emits light in accordance with the image data, and the light emitted from the chip surfaces of the arrayed light-emitting element group is focused on the photosensitive drum 102 to form an electrostatic latent image. The developer 108 develops the electrostatic latent image formed on the photosensitive drum 102 with toner. The developed toner image is transferred onto paper transported on a transfer belt 111. The image-creating unit has four image-creating units that perform the above-mentioned series of electrophotographic processes (charging, exposure, development, transfer), and are arranged in the order of cyan (C), magenta (M), yellow (Y), and black (K) to form a full-color image. The four imaging units sequentially perform magenta, yellow, and black imaging operations after a predetermined time has elapsed since the start of imaging at the cyan station. The paper feed / transport unit 105 feeds paper from a pre-selected paper feed unit—inside paper feed units 109a and 109b, external paper feed unit 109c, or manual paper feed unit 109d—and transports the paper to registration rollers 110. The registration rollers 110 transport the paper onto a transfer belt 111 at the timing when the toner image formed by the imaging unit 103 is transferred onto the paper. Opposite the transfer belt 111 is an optical sensor 113, which detects the position of a test chart printed on the transfer belt 111 to calculate the amount of color misregistration between the stations. The calculated amount of color misregistration is reported to an image controller (not shown), which corrects the image position for each color. This control ensures that a full-color toner image is transferred onto the paper without color misregistration. The fixing unit 104 is composed of a combination of rollers and has a built-in heat source such as a halogen heater. It melts and fixes the toner on the paper onto which the toner image has been transferred from the transfer belt 111 using heat and pressure, and then discharges the paper outside the image forming apparatus using paper discharge rollers 112.

[0016] The printer control unit (not shown) communicates with the MFP control unit that controls the entire MFP, and executes control in accordance with its instructions, while managing the status of the aforementioned scanner, imaging, fixing, and paper feed / transport units, and issuing instructions to ensure that the entire unit operates smoothly and in harmony.

[0017] Configuration of exposure head 106 The exposure head 106 that exposes the photosensitive drum 102 will now be described.

[0018] 2(a) and 2(b) show the arrangement of the exposure head 106 relative to the photosensitive drum 102, and how light emitted from the light-emitting element group 201 is focused onto the photosensitive drum by the rod lens array 203. The exposure head 106 and the photosensitive drum 102 are each attached to the image forming apparatus by attachment members (not shown). The exposure head 106 is made up of the light-emitting element group 201, a printed circuit board 202 on which the light-emitting element group 201 is mounted, a rod lens array 203, and a housing 204 on which the rod lens array 203 and the printed circuit board 202 are attached, and is fixed so that the light emitted from the light-emitting element group 201 forms an image on the photosensitive drum 102.

[0019] Configuration of printed circuit board 202 FIG. 3 shows a printed circuit board 202 on which a group of light emitting elements 201 are arranged.

[0020] FIG. 3(a) shows the surface opposite to the surface on which the light-emitting element group 201 is mounted (hereinafter referred to as the light-emitting element non-mounting surface), and FIG. 3(b) shows the surface on which the light-emitting element group 201 is mounted (hereinafter referred to as the light-emitting element mounting surface). The light-emitting element group 201 is configured by an array of multiple light-emitting elements 602 (602-1 to 602-n). Each light-emitting element is arranged at a predetermined resolution pitch in the longitudinal direction of the chip. In this embodiment, the pitch between adjacent light-emitting elements in the longitudinal direction of the chip is a 1200 dpi resolution pitch (approximately 21.16 μm). Furthermore, the light-emitting element group 201 is arranged with n=14173 light-emitting elements 602, enabling image formation corresponding to an image width of approximately 300 mm in the longitudinal direction of the photosensitive drum 102. Note that, in the present invention, the spacing between and the number of the light-emitting elements do not necessarily have to be limited to the resolution pitch and number described above. Furthermore, the light-emitting element group 201 corresponds to multiple light-emitting units.

[0021] On the surface where the light emitting elements are not mounted, a serial-parallel conversion control unit 720, a light emitting element driving unit 400, and a connector 305 are arranged.

[0022] A control signal for controlling the light-emitting element driving unit 400 is input as serial data to the serial-parallel conversion control unit 720 from an image controller unit (not shown) via the connector 305. The serial-parallel conversion control unit 720 restores the input serial data to parallel data and supplies the restored parallel data to the light-emitting element driving unit 400. In addition, a power supply line required for the printed circuit board 202 is also supplied to the printed circuit board 202 via the connector 305.

[0023] Details of the serial-to-parallel conversion control unit 720 will be described later together with the parallel-to-serial conversion unit on the transmitting side using FIG.

[0024] Control Block 4 shows a block diagram of the image controller unit 700 and the printed circuit board 202. In this embodiment, data communication between the image controller unit 700 and the printed circuit board 202 is performed by clock-embedded serial communication.

[0025] In this embodiment, for the sake of simplicity, processing for a single color will be described, but similar processing is performed simultaneously in parallel for four colors.

[0026] The image controller section 700 has a function of generating and transmitting a signal for controlling the light emitting element driving section 400 to the printed circuit board 202 in response to an instruction from the printer control section. In other words, the image controller section 700 corresponds to a controller.

[0027] The image controller section 700 comprises a CPU 703 , an image data generating section 701 , a communication control section 702 , a parallel-serial conversion section 710 , and a differential driver 711 .

[0028] The image data generation unit 701 generates signals for controlling the light emission of the light emitting element drive unit 400 on the printed circuit board 202 in response to instructions from the printer control unit. Specifically, the image data generation unit 701 performs dithering processing on image data received from the scanner unit 100 or from outside the image forming apparatus at a resolution instructed by the CPU 703 to generate image data for print output. In this embodiment, dithering processing is performed at a resolution of 1200 dpi in the chip longitudinal direction (main scanning direction) and 1200 dpi in the sub-scanning direction in accordance with the pitch of the light emitting elements. Furthermore, the image data is binary, with 1 representing lighting.

[0029] The communication control unit 702 transmits the image data generated by the image data generation unit 701 as a data signal 707 at a timing that results in a sub-scanning resolution of 1200 dpi based on speed information indicating the speed at which the surface of the photosensitive drum 102 moves in the rotational direction relative to a predetermined rotational speed of the photosensitive drum 102. More specifically, it generates a clock signal 705, a synchronization signal 706 indicating the start timing of communication data, and a data signal 707 for image data for light-emitting elements or for setting the register of the light-emitting element drive unit 400. Furthermore, when the CPU 703 requests transmission of a register setting value to the light-emitting element drive unit 400, the communication control unit 702 operates to transmit register setting data. At this time, header information is added to the beginning of the data signal 707 so that the data type can be identified. A synchronization signal 706 is also transmitted at the same time so that the beginning of the data can be identified. This communication is shown in Figures 5(a) and 5(b).

[0030] FIG. 5(a) shows the operation of transmitting image data from the communication control unit 702.

[0031] First, the clock signal 705 continues to toggle during transmission, and when the synchronization signal 706 goes high, a header indicating the image data is transmitted from the data signal 707, followed by the image data for each light-emitting element 602. When transmission of image data for all light-emitting elements 602 is complete, all signals go low until the next transmission begins. This is repeated in accordance with the speed at which the surface of the photosensitive drum 102 moves in the rotational direction, at a timing at which the sub-scanning resolution becomes 1200 dpi, thereby transmitting the image.

[0032] FIG. 5B shows the operation of transmitting register setting data from the communication control unit 702.

[0033] As with image data transmission, first, the clock signal 705 continues to toggle during transmission, and when the synchronization signal 706 goes high, a header indicating register data is transmitted from the data signal 707, followed by the register setting value. This changes the setting information for the drive current that drives the light emitting element 602, and changes the light intensity. This will be described in detail later.

[0034] The signal output from the communication control unit 702 is converted into a serial signal by a parallel-serial conversion unit 710. Specifically, a clock signal 705, a synchronization signal 706, and a multi-bit data signal 707 are converted into a serial signal and output. In other words, the parallel-serial conversion unit 710 corresponds to a conversion unit.

[0035] The serial signal output from the parallel-serial conversion unit 710 is converted into a differential signal 712 by a differential signal driver 711 and output to the printed circuit board 202 .

[0036] In this embodiment, an example is shown in which data is transferred between the image controller unit 700 and the printed circuit board 202 using one set of differential signals, but two or four sets may be used depending on the required transfer speed.

[0037] 3, and is composed of a serial-to-parallel conversion control unit 720, a light-emitting element driving unit 400, a light-emitting element group 201, and a connector 305. The serial-to-parallel conversion control unit 720 further comprises a differential signal receiver 721, a clock recovery unit 723, and a serial-to-parallel conversion unit 724.

[0038] A differential signal 712 output from a differential signal driver 711 of the image controller unit 700 is input to the printed circuit board 202 via the on-board transmission path, cable, and connector 305, received by a differential signal receiver 721, and converted to a normal single-ended signal. The converted single-ended signal is input to a clock recovery unit 723, which recovers the clock superimposed on the serial signal. That is, the clock recovery unit 723 corresponds to a generator that generates a clock signal 725 based on the clock superimposed on the serial signal. The signal converted to single-ended by the differential receiver 721 is also input to a serial-to-parallel converter 724, where the data is sampled using the recovered clock by the clock recovery unit 723, converted to a parallel signal, and output. As will be described in detail later, the clock signals 705 and 725 also control the timing of image data transfer. The clock signal superimposed on the serial signal is timing data containing timing information, and the clock signal 725 is generated based on the clock signal superimposed on the serial signal.

[0039] The parallel signal output from the parallel-to-serial conversion unit 724 is the same as the signal before serialization output from the communication control unit 702. Specifically, a clock signal 725, a synchronization signal 726, and a data signal 727 are output to the light-emitting element driving unit 400.

[0040] Here, a certain amount of time is required for a signal to pass through parallel-to-serial conversion unit 710 and serial-to-parallel conversion unit 724. This time (delay) varies depending on the implementation form and the transmission path between chips, but in a system with a fixed implementation form and transmission path, the delay is approximately constant regardless of the data being transferred.

[0041] A drive signal 401 is supplied from the light emitting element drive unit 400 to each light emitting element of the light emitting element group 201, and light emission is controlled by this.

[0042] The clock recovery unit 723 also outputs a lock signal 704. This lock signal 704 indicates that the phase and frequency adjustments for restoring the clock signal superimposed on the serial signal input to the clock recovery unit 723 have been completed. This lock signal 704 is input to the parallel-to-serial conversion unit 710 and the CPU 703.

[0043] Next, the operation of the lock signal 704 will be described. First, immediately after the image forming apparatus is powered on, the clock recovery unit 723 is not locked, so the parallel-to-serial conversion unit 710 transmits a communication training signal to the clock recovery unit 723 to lock it. When the clock recovery unit 723 completes clock regeneration, the clock recovery unit 723 sets the lock signal to low level, thereby notifying the parallel-to-serial conversion unit 710 and the CPU 703 that image data transfer is possible. Furthermore, if the clock is once locked by initial communication training and then becomes unlocked due to noise, the clock recovery unit 723 sets the lock signal to high level. This notifies the parallel-to-serial conversion unit 710 that the clock to be regenerated is unstable, and upon receiving the notification, the parallel-to-serial conversion unit 710 transmits a communication training signal again to perform communication training operation to lock it. Because this communication training operation is performed without the intervention of the CPU 703, even if the lock is lost during image data transfer via the serial communication unit, communication can be re-established by transmitting the training signal again as described above. This allows image transfer to continue, but if the lock is released during transfer of white data for turning off the light-emitting element group 201, the white data may not be transferred normally, causing the light-emitting element group 201 to continue emitting light. For this reason, the CPU 703 monitors the lock signal 704, and if the lock is released during image transfer, controls to transmit white data after relocking.

[0044] The series of operations of the CPU 703 will be described in detail with reference to the flowcharts of FIGS. 6 and 7 and FIG.

[0045] Fig. 6 is a flowchart showing job execution process control of the image processing apparatus in this embodiment. Note that each procedure in the flowchart of Fig. 6 is executed by the CPU 703, and each process is performed by controlling each element of the image processing apparatus under the control of the CPU 703.

[0046] First, in S1101, when the image processing apparatus is powered on, initial communication training of the serial communication unit is performed. This is performed by the parallel-serial conversion unit 710 and the serial-parallel conversion control unit 720. When the initial communication training is completed, the lock signal 704 goes low, which notifies the parallel-serial conversion unit 710 and the CPU 703, enabling image data transfer via the serial communication unit. If the initial communication training of the serial communication unit is completed in S1101, the process proceeds to S1102.

[0047] In S1102, the image processing apparatus waits for reception of a print job. If the image processing apparatus receives a print job in S1102, the process proceeds to S1103.

[0048] In S1103, when a print operation is started in response to an instruction from the printer control unit, the CPU 703 performs a register setting operation. This is done by transmitting register setting data for the light-emitting element driving unit 400 in response to an instruction from the CPU 703, thereby setting information on the drive current for driving the light-emitting element 602.

[0049] In S1104, the image data generation unit 701 generates the image data described above in response to an instruction from the CPU 703. As a result, image data to be printed with a resolution of 1200 dpi in both the main scanning and sub-scanning directions is generated.

[0050] In S1105, the CPU 703 controls the communication control unit 702 to output image data generated at regular intervals based on speed information of the movement of the surface of the photosensitive drum 102 in the rotation direction, and image formation begins. The data output from the communication control unit 702 passes through the parallel-to-serial conversion unit 710 and the serial-to-parallel conversion unit 724 and is supplied to the light-emitting element drive unit 400. Then, under the control of the light-emitting element drive unit 400, each light-emitting element emits light, thereby forming an image for each line. By performing this operation up to the last line, an image for one page is formed.

[0051] In S1106, it is determined whether the line transmitted in S1105 is the last line. If it is not the last line, the process returns to S1105 and repeats image transmission, and if it is the last line, the process proceeds to S1107.

[0052] In S1107, since the output of image data for one page to be formed has been completed, white data is output after the output of the image data for the final line, thereby stopping the light emission of the light emitting element group 201.

[0053] In S1108, it is determined whether the series of printing operations is complete, and if there is a next page, the process returns to S1103 and the same process is repeated to perform continuous printing operations.If there is no next page, the process returns to S1102 and the process waits again for reception of a print job.

[0054] Next, detection of lock-out by the clock recovery unit 723 and the processing flow executed when lock-out is detected will be described with reference to Fig. 7. Note that each procedure in the flowchart of Fig. 7 is executed by the CPU 703, and each process is performed by controlling each element of the image processing device under the control of the CPU 703. Also, the flowchart of Fig. 7 is executed in parallel with the flowchart of Fig. 6.

[0055] The flowchart in FIG. 7 starts when the image processing apparatus is powered on, initial communication training of the serial communication unit is completed, and the lock signal 704 output by the clock recovery unit 723 indicates a locked state.

[0056] In S1201, the CPU 703 monitors whether the serial communication unit is unlocked. If the lock signal goes high in S1201, this means that the clock recovery unit 723 is unlocked, and the process proceeds to S1202.

[0057] In S1202, the CPU 703 monitors whether the lock signal 704 is in a state indicating that it is locked again. If the lock is released in S1201, the lock signal output by the clock recovery unit 723 goes to high level. When the lock signal goes to high level, the parallel-serial conversion unit 710 transmits a communication training signal to the clock recovery unit 723 to perform processing to re-lock. This communication training is performed without the intervention of the CPU 703. If the clock recovery unit 723 is locked again during this communication training, the process proceeds to S1203.

[0058] In S1203, the CPU 703 determines whether the lock has been released during image data transfer. If the lock has not been released during image data transfer in S1203, the transfer of white data for turning off the light-emitting element group 201 is not affected and the light-emitting element group 201 has been re-locked, so the process returns to S1201 and resumes monitoring to see if the lock has been released. FIG. 8(a) shows the operation when the lock has been released at a timing other than during image transfer. As shown in FIG. 8(a), if the lock has been released at a timing other than during image data transfer, the light emission of the light-emitting element group 201 has stopped, so there is no need to transfer the white data again. On the other hand, if the lock has been released during image data transfer in S1203, the process proceeds to S1204.

[0059] In S1204, it is determined whether relocking occurred during image transfer. If relocking occurred during image transfer in S1204, it means that the lock was released during image transfer, but the relock occurred during the transfer of image data for that page. This means that serial communication was occurring normally during the transfer of white data to turn off the light-emitting element group 201. FIG. 8B shows the operation when the lock is released during image transfer and the relock occurs during image transfer. As shown in FIG. 8B, if the lock signal is released during image data transfer but the relock is performed immediately, the normal data transfer state resumes from the time of relocking. If relocking occurs during image transfer, white data after the last line of the page can also be transferred, eliminating the need to transfer white data at the time of relocking. Therefore, if relocking occurred during image transfer in S1203, the process returns to S1201 and resumes monitoring to see if the lock is released again. On the other hand, if relocking did not occur during image transfer in S1203, the process proceeds to S1205.

[0060] If the process proceeds to S1205, the lock was released during image data transfer and relocking was not performed during image transfer. In other words, the transfer of white data to turn off the light-emitting element group 201 after transferring one page of image data was not performed properly. In this state, the light-emitting element group 201 continues to emit light, leading to drum memory. Therefore, in S1205, white data is transferred again. In this case, since the lock was released and relocking was performed again in S1204, the transfer of white data can be performed normally. Figure 8(c) shows the operation when the lock was released during image transfer and relocking was not performed during image transfer. As shown in Figure 8(c), if the lock was released during image data transfer and relocking was not performed during image data transfer, the transfer of white data to turn off the light-emitting element group 201 after transferring one page of image data was not performed properly. Therefore, the light-emitting element group 201 is turned off by transferring white data at the timing of relocking.

[0061] Depending on the timing at which the lock is released, it is possible that the image data assigned to the last line of image data for one page was transmitted as serial data from the controller but not converted to parallel data. In this case, in addition to the white data assigned to the last line of one page, white data may be transmitted again at the timing of relock. Even in this case, the light-emitting element group 201 can be reliably turned off, reducing the risk of overexposure of the photosensitive drum. In other words, the white data assigned to the last line of one page corresponds to the first lights-out image data, and the white data transmitted again at the timing of relock corresponds to the second lights-out image data.

[0062] By using the above flow, if the lock is released during image data transfer and there is a possibility that the transmission of white data to turn off the light-emitting element has not been completed, it is possible to prevent drum memory by sending white data again after relocking.

[0063] Furthermore, according to this embodiment, instead of transmitting white data uniformly when the lock is released, it is possible to transmit white data only when the transmission of white data for turning off the light emitting element group 201 after the transmission of image data of one page has not been performed normally. This prevents unnecessary interruption of the image data transmission, and makes it possible to continue the image data transmission when the image data transmission can be continued.

[0064] Furthermore, in this embodiment, a configuration has been described in which white data is transmitted via the serial communication unit when the lock is released and then re-locked. However, a configuration in which the light-emitting element drive unit 400 can transmit white data when the lock is released may also be used. In this configuration, when the lock is released, the CPU 703 instructs the light-emitting element drive unit 400 without going through the serial communication unit, and the light-emitting element drive unit 400 transmits the white data. With this configuration, when the lock is not released, the white data transmission after the transfer of one page of data is performed via the serial communication unit, emphasizing productivity. Only when the lock is released does the CPU 703 instruct the light-emitting element drive unit 400 to turn off the light-emitting element group 201. If the light-emitting element drive unit 400 itself is capable of transmitting white data, it is also possible for the CPU 703 to instruct the light-emitting element drive unit 400 to transmit white data after the transfer of one page of data other than when the lock is released, without going through the serial communication unit. However, in this case, it takes extra time to switch between image data transfer from the serial communication unit and white data transmission processing from the light-emitting element drive unit 400, which has a negative impact on productivity when printing consecutive pages, etc. Therefore, the reason why the CPU 703 instructs the light-emitting element drive unit 400 to transmit white data without going through the serial communication unit is to respond when the lock is released.

[0065] Circuit block of the light emitting element driving unit 400 9 shows a circuit block diagram within the light-emitting element driving unit 400. The circuit unit 406 within the light-emitting element driving unit 400 is composed of a digital unit 800 and an analog unit 806. The digital unit 800 receives a clock signal 725, a synchronization signal 726, and a data signal 727 transmitted from the serial-parallel conversion control unit 720 at a receiving unit 801, and if the received content is image data, it has the function of generating a lighting signal 808 (808-1 to 808-n) for lighting the light-emitting elements and sending it to the analog unit 806. If the received content is register setting, the content is stored in a register unit 802, the setting for controlling the operation of the analog unit 806 is changed, and the changed signal is sent to the analog unit 806 as a register signal 807. This setting includes, for example, setting information for the drive current used to drive the light-emitting elements in the analog unit 806.

[0066] The analog unit 806 generates a signal required to drive the light-emitting elements based on the lighting signal 808 generated by the digital unit 800. Figure 10 shows a block diagram of the analog unit 806. In this embodiment, for the sake of simplicity, only two light-emitting elements 602-1 and 602-2 and two drive units 1601-1 and 1601-2 are shown, but it is assumed that similar drive units are formed corresponding to all the light-emitting elements in the light-emitting element group 201. First, a register signal 807 transmitted based on data set in the register unit 802 is input to a DAC 1602 (digital-analog converter), and an analog voltage 1603 that determines the drive current for the light-emitting elements 602-1 and 602-2 is supplied to the drive units 1601-1 and 1601-2. Next, when lighting signals 808-1 and 808-2 are input to the driving units 1601-1 and 1601-2, the driving units 1601-1 and 1601-2 cause each light-emitting element (602-1, 602-2) to start emitting light independently using the driving circuit described below based on the analog voltage 1603 that determines the driving current and the lighting signals 808-1 and 808-2.

[0067] FIG. 11 shows the circuit of the driver 1601-1. Drivers for other light-emitting elements (e.g., 1601-2) are also driven by a similar circuit. The MOSFET 1702 supplies a drive current to the light-emitting element 602-1 according to the gate voltage value, and controls the current so that the drive current is turned off (exited) when the gate voltage is low. The analog voltage 1603 is connected to the gate of the MOSFET 1704, and when the drive signal 401 is high, the voltage charged in the capacitor 1706 is transferred to the MOSFET 1702. In this embodiment, the DAC 1602 sets an analog voltage in the capacitor 1706 before image formation and maintains the voltage level during the image formation period. Through the above operation, the MOSFET 1702 supplies a drive current to the light-emitting element 602-1 in accordance with the set analog voltage and the drive signal 401, causing it to emit light. A signal obtained by logically inverting the lighting signal by an inverter 1705 is input to the gate of the MOSFET 1703. As a result, when the lighting signal is low, the gate of the MOSFET 1703 becomes high, and the charge stored in the input capacitance of the light emitting element 602-1 is forcibly discharged, thereby accelerating the response speed until the light emission stops.

[0068] Even when the light emission is stopped, the power supply connected to the capacitor 1706 and the MOSFET 1702 is still operating, and the light emission stops when the supply of drive current to the light-emitting element 602-1 is stopped, so there is no need to install chip components with input-tolerant functions in the power supply section.

[0069] As described above, according to the present invention, if the lock is released during image data transfer and there is a possibility that the transmission of white data has not been completed, the white data is sent again after relocking, thereby preventing drum memory from filling up and providing a high-quality printer that does not produce abnormal images. [Explanation of symbols]

[0070] 102 Photosensitive drum 602 Light-emitting element 106 Exposure head 703 CPU

Claims

1. A rotating photoreceptor; an exposure head that emits light to expose the photosensitive member and has a plurality of light-emitting units arranged along the rotation axis of the photosensitive member; a controller that outputs image data for controlling turning on and off the plurality of light-emitting units, the controller outputting first lights-out image data indicating that the plurality of light-emitting units are to be turned off after transmitting the image data for one page, and outputting second lights-out image data indicating that the plurality of light-emitting units are to be turned off after outputting the first lights-out image data; a driver that drives the plurality of light-emitting units based on the image data; An image forming apparatus comprising:

2. the controller outputs serial data including the image data and timing data having timing information for transmitting and receiving the image data; the image forming apparatus, a generator that generates a clock signal of a predetermined frequency based on the timing data included in the serial data; a conversion unit that converts the image data included in the serial data into parallel data based on the clock signal generated by the generation unit; The image forming apparatus according to claim 1 , further comprising:

3. the conversion unit suspends conversion of the image data included in the serial data into the parallel data when the generation unit stops generating the clock signal of the predetermined frequency; 3. The image forming apparatus according to claim 2, wherein the image forming apparatus is a recording medium.

4. when the generation unit stops generating the clock signal of the predetermined frequency, it outputs a signal indicating that the generation unit has stopped generating the clock signal of the predetermined frequency; the controller retransmits the image data whose conversion into parallel data has been interrupted based on the signal; 4. The image forming apparatus according to claim 3, wherein the image forming apparatus is a recording medium.

5. the controller does not output the second lights-out image data when the generation unit stops generating the clock signal of the predetermined frequency while outputting the image data, and outputs the second lights-out image data when the generation unit stops generating the clock signal of the predetermined frequency while outputting the first lights-out image data.

4. The image forming apparatus according to claim 3, wherein the image forming apparatus is a recording medium.

6. the controller assigns the first lights-out image data to a final line of the image data and outputs the image data, and outputs the second lights-out image data after a predetermined time has elapsed since transmitting the image data to which the first lights-out image data has been assigned.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

7. The plurality of light-emitting units are organic electroluminescent (EL) units.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

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