Image forming apparatus

Abstract

The invention provides an image forming apparatus capable of reliably detecting synchronization without erroneous detection due to stray light or missing detection due to insufficient light quantity even if the light quantity of a laser beam incident on a synchronization detection sensor changes due to printing conditions and the like. The present invention relates to an image forming apparatus for forming an image by a developer for developing an electrostatic latent image formed on a photoreceptor, the image forming apparatus having an optical writing device for exposing the photoreceptor, the optical writing device comprising: a light emitting element; a light emission control element; a deflection element; a synchronous detection element; a gain switching circuit; and a gain control signal selection circuit.

Description

Technical Field

[0001] This invention relates to an image forming apparatus. Background Technology

[0002] In an electrophotographic image forming apparatus that uses a light-emitting element such as a laser diode (LD) to expose a photoreceptor, the light beam output from the LD is reflected by a rotating polygon mirror. In this apparatus, when the LD's light beam (laser beam) shines from one end of one side of the polygon mirror to the other, the beam is deflected according to the angle of the polygon mirror and scans a line on the photosensitive element. At this time, by switching the LD on or off according to the input image data, a single line of electrostatic latent image can be formed on the photoreceptor. Then, the electrophotographic image forming apparatus repeats the line scan while rotating the photoreceptor, thereby forming an electrostatic latent image of the desired image.

[0003] When repeatedly scanning one line of the laser beam on the photoreceptor, it is necessary to align with the timing of writing the initial image. To determine this writing start timing, a light detection sensor is installed before scanning the photoreceptor to detect the scanning position of the laser beam. This light detection sensor is used as a synchronization detection sensor, and the writing start timing of the image data is determined based on the output signal of the synchronization detection sensor.

[0004] Here, the light detection sensor is a photodiode, which uses an amplifier and a gain resistor to detect minute changes in current. Based on this change in current, the presence or absence of a laser beam can be determined. Although light detection sensors can be fabricated by combining components into a circuit, photoelectric ICs with slits or glass covers to improve detection accuracy and stability are commercially available and inexpensive.

[0005] For example, Patent Document 1 discloses a configuration in which, in order to prevent detection omissions and false detections under conditions of light intensity variation, the gain of the synchronous detection circuit is switched by an external signal according to the light intensity set for each condition.

[0006] However, the amount of light from the laser beam changes depending on the imaging conditions. These imaging conditions include not only changes in the resolution of the output image, but also changes in productivity (e.g., linear velocity), temperature environment, etc. Therefore, the amount of light from the laser beam input to the synchronous detection sensor also changes. Furthermore, when the amount of light from the laser beam changes, false detections due to stray light or missed detections due to insufficient light may occur. Additionally, in the configuration described in Patent Document 1, when a synchronous detection signal includes synchronization timings for multiple colors, the optimal gain for each color cannot be selected.

[0007] The present invention was made in view of the above-mentioned problems, and its object is to provide an image forming apparatus that, even if the amount of light of the laser beam incident on the synchronization detection element changes due to printing conditions or other reasons, will not cause false detection due to stray light or missed detection due to insufficient light, and can reliably detect synchronization.

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2002-113899 Summary of the Invention

[0009] To solve the above problems and achieve the objective, the present invention is an image forming apparatus that forms an image by developing an electrostatic latent image formed on a photoreceptor using a developer. The apparatus is characterized by having an optical writing device that exposes the photoreceptor. The optical writing device includes: a light-emitting element that illuminates the photoreceptor; a light-emitting control element that outputs a light-emitting control signal to control the illumination state of the light-emitting element, thereby controlling the light emission of the light-emitting element; a deflection element, which is a multi-faceted reflector disposed in the light path from the light-emitting element, and deflects the light illuminating the surface of the reflector by rotational drive to scan the photoreceptor in one direction; and a synchronous detection element, which is illuminated by... The system includes light from a first-color light-emitting element among the plurality of light-emitting elements used in the formation of the electrostatic latent image on different photoreceptors, and light from a second-color light-emitting element among the plurality of light-emitting elements that is different from the first color, and detects the start timing of writing the electrostatic latent image caused by the illumination of light onto the photoreceptor; a gain switching circuit capable of switching the gain of the synchronization detection element; and a gain control signal selection circuit connected to the light emission control signal, which selects one of a plurality of gain control signals connected to the gain switching circuit of the same synchronization detection element and sets the gain of the synchronization detection element according to the light emission control signal.

[0010] The effect obtained by the present invention is that even if the amount of light of the laser beam incident on the synchronization detection element changes due to printing conditions or other reasons, false detection caused by stray light or missed detection caused by insufficient light will not occur, and synchronization can be reliably detected. Attached Figure Description

[0011] Figure 1-1 This diagram illustrates the decrease in light intensity at both ends of the photoreceptor when the light intensity of the light-emitting element is controlled to be constant in the image forming apparatus according to this embodiment.

[0012] Figure 1-2 This diagram illustrates the decrease in light intensity at both ends of the photoreceptor when the light intensity of the light-emitting element is controlled to be constant in the image forming apparatus according to this embodiment.

[0013] Figure 2 This diagram illustrates an example of the selection operation of the gain of the synchronous illumination signal of the image forming apparatus according to this embodiment.

[0014] Figure 3 This is a diagram illustrating an example of the gain selection operation of the APC signal of the image forming apparatus according to this embodiment.

[0015] Figure 4 This is a diagram illustrating an example of the waveform of the synchronous detection signal when each imaging color LD in the image forming apparatus according to this embodiment has multiple light-emitting elements.

[0016] Figure 5 This is a diagram illustrating an example of the substrate configuration for the light emission control IC and gain control signal selection circuit of the image forming apparatus according to this embodiment.

[0017] Figure 6 This diagram illustrates an example of the initialization function of the gain control signal selection circuit in the image forming apparatus according to this embodiment.

[0018] Figure 7 This is a diagram illustrating another example of the initialization function of the gain control signal selection circuit in the image forming apparatus according to this embodiment.

[0019] Figure 8 This diagram illustrates an example of the timing of the operation of the initialization signal of the gain control signal selection circuit in the image forming apparatus according to this embodiment.

[0020] Figure 9 This is a diagram illustrating an example of the configuration of an update system having a characteristic value for writing the deviation of the start timing in an image forming apparatus according to this embodiment.

[0021] Figure 10 This is a diagram illustrating other configurations of an update system having characteristic values ​​of the deviation in the writing start timing in an image forming apparatus according to this embodiment.

[0022] Figure 11-1 The diagram shown is a flowchart of an example of the density adjustment operation of the image forming apparatus according to this embodiment.

[0023] Figure 11-2 The diagram shown is a flowchart of an example of the printing operation of the image forming apparatus according to this embodiment.

[0024] Figure 12-1 The diagram shown is a flowchart of an example of the color alignment operation of the image forming apparatus according to this embodiment.

[0025] Figure 12-2The diagram shown is a flowchart of another example of the printing operation of the image forming apparatus according to this embodiment. Detailed Implementation

[0026] Hereinafter, embodiments of the image forming apparatus will be described in detail with reference to the accompanying drawings.

[0027] Figure 1-1 and Figure 1-2 This diagram illustrates the decrease in light intensity at both ends of the photoreceptor when the light intensity of the light-emitting element is controlled to be constant in the image forming apparatus according to this embodiment. Figure 1-2 In the diagram, the vertical axis represents the amount of light emitted from the LD (light-emitting element) or the amount of light reaching the photoreceptor 106, and the horizontal axis represents the scanning position of the light beam on the photoreceptor 106.

[0028] This embodiment of the image forming apparatus is an example of an image forming apparatus (e.g., a color image forming apparatus of an electrophotographic method) that forms an image by developing an electrostatic latent image formed on a photoreceptor 106 with a developer. Furthermore, the image forming apparatus of this embodiment includes a light writing device 1 for exposing the photoreceptor 106. This light writing device 1 includes a light-emitting element and a light-emitting control IC 102 (see reference 102). Figure 2 ), deflection element 103, synchronization detection IC 104, gain switching circuit 104a (refer to) Figure 10 The light-emitting element is an example of a light-emitting element that illuminates the photoreceptor 106. The optical writing device 1 may include multiple light-emitting elements. The light-emitting control IC 102 is an example of a light-emitting control element that outputs a light-emitting control signal to control the illumination state of the light-emitting element in order to control the light emission of the light-emitting element. The deflection element 103 is a multifaceted reflector that is disposed in the light path emitted from the light-emitting element and is driven by rotation to deflect the light illuminating the surface of the reflector, thereby scanning the photoreceptor 106 in one direction. The synchronization detection IC 104 is an example of a synchronization detection element that detects the start time of writing an electrostatic latent image formed by illuminating light onto the photoreceptor 106. Furthermore, the synchronization detection IC 104 illuminates the synchronization detection IC 104 (the same synchronization detection IC) with light from a first-color light-emitting element among the multiple light-emitting elements used to form electrostatic latent images of different photoreceptors 106, and with light from a second-color light-emitting element among the multiple light-emitting elements that is different from the first color. That is, multiple lights are emitted from multiple light-emitting elements and irradiated into the synchronization detection IC through different optical paths. Here, different optical paths mean that in the configuration where two laser beams are emitted towards the first color (a photosensitive element 106), the laser beams are different from those of the first color. Furthermore, the optical path refers to the optical path leading up to the synchronization detection IC 104. The gain switching circuit 104a is an example of a gain switching circuit capable of switching the gain of the synchronization detection IC 104.

[0029] However, when an electrostatic latent image is formed on the photoreceptor 106, due to the characteristics of the optical system 107, there is a phenomenon where the amount of light reaching the light-emitting element decreases as it moves away from the center of the photoreceptor 106. To compensate for this decrease in light amount, a driver with a correction function that enhances the amount of emitted light from the light-emitting element at both ends is known. If this correction function is used, the amount of incident light to the synchronization detection plate (synchronization detection IC 104) can be constant regardless of conditions, but the cost will increase. Therefore, in this embodiment, using a driver with constant light amount control without correction function limits the configuration to an inexpensive one. Specifically, the light emission control IC 102 controls the amount of light from the light-emitting element to a constant during the scanning of light irradiated from one end of one side of the deflection element 103 to the other in one direction. Thus, an inexpensive system without black spot correction can be realized.

[0030] Figure 2 This diagram illustrates an example of the gain selection operation of the synchronous illumination signal of the image forming apparatus according to this embodiment. In this embodiment, the image forming apparatus includes an illumination control IC 102, a CPU (central processing unit) 201, a gain control signal selection circuit 202, a synchronization detection IC 104, etc.

[0031] The light-emitting control IC 102 outputs a synchronous lighting signal (an example of a light-emitting control signal) to control the lighting state of the light-emitting elements. The CPU 201 is connected to the gain switching circuit 104a of the synchronization detection IC 104 and outputs a gain signal (an example of a gain control signal) to set the gain of the synchronization detection IC 104. Furthermore, the CPU 201 outputs multiple gain signals corresponding to each of the multiple light-emitting elements. The gain control signal selection circuit 202 is an example of a gain control signal selection circuit that selects a gain selection signal, which is one of multiple gain signals connected to the gain switching circuit 104a of the same synchronization detection IC 104. Additionally, the gain control signal selection circuit 202 is connected to the synchronous lighting signal output from the light-emitting control IC 102. That is, the gain control signal selection circuit 202 selects a gain selection signal as one of the multiple gain signals based on the synchronous lighting signal (an example of a light-emitting control signal) output from the light-emitting control IC 102. Therefore, even if laser beams of different powers are directed into a synchronous detection IC104, synchronous detection can be performed appropriately, that is, stray light and missed detection can be suppressed.

[0032] Figure 2The example shown is a system that uses a single synchronization detection IC 104 to synchronize two color beams, Bk and Ye. Synchronization lighting signals for each color are activated before and after the laser beams of each color scan the synchronization detection IC 104. Since this timing coincides with the timing of the gain signal selection, it is reasonable to use the synchronization lighting signal, in particular, as the gain control signal in the light emission control signal. That is, the gain control signal selection circuit 202 can be connected to the synchronization lighting signal (i.e., the input synchronization lighting signal) in the light emission control signal. Alternatively, the gain control signal selection circuit 202 can also be connected to (input) a single-ended signal in the light emission control signal.

[0033] Figure 3 This diagram illustrates an example of the gain selection operation of the APC signal in the image forming apparatus according to this embodiment. In this embodiment, the sync lighting signal is also used as a data signal. When it cannot be connected to the gain control signal selection circuit 202 (i.e., when the sync lighting signal is not input to the gain control signal selection circuit 202), the APC signal is used instead of the sync lighting signal. Since the sync lighting timing (the timing when the sync lighting signal is activated) is the gain selection timing, the APC signal can be used as a gain switching signal by performing APC control so that the timing of APC control overlaps with the timing of the sync lighting signal (not necessarily completely overlapping). That is, the gain control signal selection circuit 202 is connected to the APC signal in the light emission control signal (i.e., the APC signal is input). Since the APC signal is activated near the sync lighting, it is suitable for switching the gain signal. Furthermore, the timing of the APC signal operation can also overlap with the timing of the sync lighting.

[0034] Figure 4 This is a diagram illustrating an example of the waveform of the synchronous detection signal when each imaging color LD in the image forming apparatus according to this embodiment has multiple light-emitting elements. Figure 4 This diagram illustrates an example where two laser beams of different colors are incident on a single synchronization detection board (synchronization detection IC104), with each laser beam having two light-emitting elements. Since the amount of light required for imaging is shared among light-emitting elements of the same color, the increase in circuit area can be suppressed by sharing the gain signal. That is, when the light writing device 1 has multiple light-emitting elements illuminating a photoreceptor 106, these multiple light-emitting elements share the synchronization detection signal. Specifically, the light emission control IC102 outputs a light emission control signal based on any one of the synchronization detection signals from the synchronization detection IC104. Therefore, by sharing the synchronization detection signal among light-emitting elements of the same color, the circuit area can be reduced.

[0035] Figure 5This diagram illustrates an example of the substrate configuration for the light emission control IC and gain control signal selection circuit of the image forming apparatus according to this embodiment. Generally, the control substrate 2 and the light writing device 1 are separately configured within the image forming apparatus and electrically connected by a wiring harness. Since the wiring harness is susceptible to external noise, the impact of noise can be reduced by arranging the gain control signal selection circuit 202 and the light emission control IC 102 on the same substrate. Furthermore, by mounting multiple synchronization detection boards (synchronization detection IC 104) and laser drive substrate 108 within the light writing device 1, the number of wires can be reduced.

[0036] This diagram illustrates an example of the initialization function of the gain control signal selection circuit in the image forming apparatus according to this embodiment. The gain control signal selection circuit 202 has an initialization function that initializes the state of the gain control signal selection circuit 202. Figure 6 The gain control signal selection circuit 202 specifically includes a D flip-flop (an example of a flip-flop) and a NAND gate. This allows the state of the gain selection signal to be maintained. Then, when the CLR signal of the D flip-flop goes low, the gain selection signal is correspondingly reset to its initial state, and the gain selection signal provided to the synchronization detection IC 104 also becomes initial. The light emission control IC 102, which generates the light emission control signal, outputs an initialization signal (gain selection initialization signal) to set the initialization function to be active or inactive. Therefore, since the state of the gain selection signal is initialized row by row, discrepancies between the gain selection signal and the corresponding color of the incident light to the synchronization detection IC 104 can be prevented. The gain control signal selection circuit 202 is not limited to logic ICs such as D flip-flops or NAND gates, as long as it has the function of switching the gain selection signal.

[0037] In this embodiment, a configuration is adopted in which a light emission control signal branch is connected to control the light emission of the LD (light-emitting element) on the LDB (laser drive substrate). The operation of a signal output from the light emission control IC102 is to control the gain selection initialization circuit (gain control signal selection circuit 202) while controlling the light emission of the LD (light-emitting element) on the LDB.

[0038] Furthermore, if the LVDS signal (differential signal) is used as the initialization signal for branching connections, it can lead to increased circuit load, waveform collapse and signal quality degradation, or unwanted radiation. LVDS signals are also used for high-speed transmission signals such as data signals (signals that turn the LD on or off according to the image in the image area), and especially when connected to data signals, they can potentially have adverse effects on the image itself. To prevent such adverse effects, it is preferable to use a configuration where the single-ended signal in the luminance control signal is branched and connected as the initialization signal (gain selection initialization signal). That is, the single-ended signal in the luminance control signal can also be used as the initialization signal. Therefore, compared to using the LVDS signal as the initialization signal, the impact on waveform quality and EMI can be reduced.

[0039] Figure 7 This is a diagram illustrating another example of the initialization function of the gain control signal selection circuit in the image forming apparatus according to this embodiment. Figure 7 The configuration of the image forming apparatus shown is similar to Figure 6 The difference in the configuration of the image forming apparatus shown is that the gain selection initialization signal output from the light-emitting control IC 102 and the light-emitting control signal that controls the light emission of the LD (light-emitting element) on the LDB are independently connected to the gain control signal selection circuit 202. That is, the gain selection initialization signal can also be independently connected to the light-emitting control IC 102 along with the light-emitting control signal that controls the illumination state of the light-emitting element. Therefore, by using the empty terminal of the light-emitting control IC 102, no new generation circuit is required. Whether the connection is branched or independent, the commonality is that the initialization state is controlled by the light-emitting control IC 102.

[0040] Figure 7 A point that should be particularly noted in the configuration of the image forming apparatus shown is that it can be processed with the initialization timing of the gain selection signal based on the gain selection initialization signal as the target timing. The light emission control IC 102 operates synchronously with the synchronization detection signal input from the synchronization detection IC 104, and thus generates the gain selection initialization signal corresponding to its operating cycle, thereby initializing the gain selection signal. Then, the timing of this initialization can be adjusted to the target timing of the operating cycle.

[0041] Figure 8 This diagram illustrates an example of the timing of the operation of the initialization signal in the gain control signal selection circuit of the image forming apparatus according to this embodiment. In this embodiment, in Figure 7In the configuration of the image forming apparatus shown, the timing of the generation of the gain selection initialization signal is such that it can be adjusted independently of the emission control signal (e.g., the synchronization detection signal). The gain selection initialization signal can be generated at any time during the cycle from the activation (=low) of the synchronization detection signal to the next activation (=low).

[0042] Initializing the gain selection signal means that in this optical system (the light detection sensor 104b on the synchronization detection IC104), it returns to the synchronization lighting signal located at the beginning ( Figure 8 The state of the synchronization detection signal (Bk) is appropriately generated. That is, in this embodiment, the state of the gain selection signal is transitioned to output the gain selection signal of Bk. In this way, the gain selection signal must be initialized before generating the synchronization lighting signal of Bk at the beginning.

[0043] Additionally, the gain selection signal must be switched simultaneously to activate the final sync lighting signal. Figure 8 The gain selection signal is used to generate the synchronization detection signal appropriately. That is, the gain selection signal must be initialized after the synchronization lighting signal at the end of Ye. If the initialization is performed between the two times mentioned above, the ideal gain signal can be initialized.

[0044] That is, when a latent image is formed on different photoreceptors 106 by the rotational drive of the deflection element 103, and the photoreceptor 106 that initially forms the latent image is represented as the beginning photoreceptor 106 and the photoreceptor 106 that last forms the latent image is represented as the last photoreceptor 106 on the time axis, the initialization function operates during the period from the detection of the sync lighting signal related to the last photoreceptor 106 to the detection of the sync lighting signal of the beginning photoreceptor 106. Therefore, by initializing at the appropriate time, erroneous operation can be prevented.

[0045] Figure 9 This diagram illustrates an example of the configuration of an update system having a characteristic value for writing the deviation of the start timing in an image forming apparatus according to this embodiment. The gain switching circuit 104a of the synchronization detection IC 104 includes at least two gain signals ( Figure 9 (SIG1 and SIG2 in the diagram). One of the gain signals operates by switching the gain according to the behavior of the light control IC 102. Then, the other gain signal is connected to circuitry that is not affected by the behavior of the light control IC 102.

[0046] The light-emitting control IC102 is a circuit that repeats its operation based on the cycle of synchronous detection. Therefore, another gain signal ( Figure 9SIG1 in the context is a signal that does not operate according to the period of the synchronization detection signal and does not require activation. For example, to measure the timing deviation of the detection when the amount of light illuminating the light sensor 104b of the synchronization detection IC 104 changes, the gain signal of the other party can also be used. Figure 9 (SIG1 in the middle). Measure the gain signal of the other party respectively. Figure 9 The SIG1 signal is fixed at a low level while the gain signal of Bk or Ye is set. Figure 9 The detection timing of the light detection sensor 104b at SIG2, and the gain signal of the other party ( Figure 9 The SIG1 signal is fixed at a high level, while the gain signal of Bk or Ye is set. Figure 9 The system calculates the detection timing of the light detection sensor 104b when the light intensity changes (SIG2) and determines the characteristic value of the deviation of the detection timing based on the result. Then, a correction amount is calculated based on the calculated characteristic value of the detection timing deviation. Thus, in order to correct the detection timing deviation, at least one or more of the plurality of gain signals are configured to be connected to circuitry outside the light emission control IC 102.

[0047] That is, when the system operates to update the characteristic value of the deviation in the image write-out start timing caused by the gain switching, the gain signal connected to the gain control signal selection circuit 202 is activated, and when the system operates otherwise, it operates in a manner in which the logic of the gain signal connected to the gain control signal selection circuit 202 is fixed. As a result, high-quality images can be provided.

[0048] Figure 10 This is a diagram illustrating other configurations of an update system having a characteristic value for writing the start timing deviation in the image forming apparatus according to this embodiment. In this embodiment, the gain switching circuit 104a of the synchronization detection board (synchronization detection IC 104) includes at least two gain signals ( Figure 10 The gain switching signal (SIG1, SIG2) can also be adjusted based on the action of the light emission control IC102. Then, the other gain signal is connected to a circuit unaffected by the behavior of the light emission control IC102.

[0049] The gain switching circuit 104a is implemented, for example, through a combination of resistors and transistors. When the gain resistor R1 is 3.0kΩ, R2 is 10.0kΩ, R3 is 5.10kΩ, and the gain ratio is 1.30 or 0.69, the gain resistor values ​​are 3.0kΩ, 2.31kΩ, 1.89kΩ, and 1.59kΩ, depending on whether the transistor is on or off. For example, suppose 2.31kΩ and 1.59kΩ are used in the printing process. When used in the printing process, the gain of Bk or Ye needs to be appropriately switched by the light-emitting control IC 102; therefore, 2.31kΩ and 1.59kΩ must be selectable by the gain signal of Bk or Ye. Figure 10 In the circuit, the impedance is 2.31kΩ when SIG1 is ON and SIG2 is OFF, and 1.59kΩ when SIG1 is ON and SIG2 is ON. Therefore, the SIG2 side becomes the signal connected to the light emission control IC 102. SIG1 is not connected to the light emission control IC 102, but is connected to the engine CPU, for example, to switch between low and high level outputs when the update system for updating the characteristic value of the deviation of the detection timing of the light detection sensor 104b is activated. Then, during the printing operation, SIG1 remains in the normally on state (= high level).

[0050] With this configuration, a system can be constructed that, through the light emission control IC 102 and the gain control signal selection circuit 202, appropriately switches the gain signal of Bk or Ye during the printing operation, while simultaneously updating the characteristic value of the detection timing deviation of the light detection sensor 104b. That is, there are multiple gain signals for setting the gain of the synchronous detection IC 104, at least one of which is connected to circuitry other than the gain control signal selection circuit 202. Thus, it is possible to select the gain used during the printing operation and the gain not used during the printing operation, respectively.

[0051] Figure 11-1 The diagram shown is a flowchart of an example of the density adjustment operation of the image forming apparatus according to this embodiment. Figure 11-2 The diagram shown is a flowchart of an example of the printing operation of the image forming apparatus according to this embodiment.

[0052] exist Figure 11-1 In the concentration adjustment operation shown, the amount of light from the laser beam, which is one of the imaging conditions, is adjusted. Specifically, the image forming apparatus performs a preprocessing step (step S1101) to detect the amount of light from the laser beam. Next, the image forming apparatus forms a concentration adjustment pattern (step S1102). Then, the synchronous detection IC 104 detects the concentration adjustment pattern (step S1103) and calculates the amount of light from the LD (light-emitting element) based on the detection result (step S1104).

[0053] If the amount of light in the laser beam changes, the amount of light in the laser beam incident on the light detection sensor 104b of the synchronization detection IC 104 also changes, thus requiring a determination of whether the gain of the synchronization detection IC 102 needs to be switched. Therefore, the image forming apparatus determines whether the calculated result of the light amount of the LD (light-emitting element) is within the normal range (step S1105). When the light amount of the LD is within the normal range (step S1105: Yes), the image forming apparatus updates the setting value of the light amount of the LD (step S1106). Then, if it is determined that a gain switch is needed (step S1107: Yes), the image forming apparatus updates the gain setting value (gain setting value) of the synchronization detection IC 104 stored in a storage unit such as a memory (step S1108).

[0054] At this time, since the gain setting value stored in the storage unit only contains the number of laser beams incident on the light detection sensor 104b, the gain setting value stored in the storage unit is updated according to the laser beam whose light intensity has been adjusted by the concentration adjustment operation. When the printing operation or adjustment operation is performed, the updated gain setting value is reflected.

[0055] exist Figure 11-2 In the printing operation shown, the image forming apparatus first sets the sensitivity of the light detection sensor 104b (step S1109) and performs printing operation preprocessing (step S1110). Here, setting the sensitivity of the light detection sensor 104b includes reading the gain setting value stored in the storage unit and setting the gain of the light detection sensor 104b to an appropriate value. At this time, if it is a monochrome operation, the gain setting value for that monochrome operation is read; if it is a full-color operation, the gain setting values ​​for all colors are read. Thus, appropriate gain setting values ​​are set according to the laser beams corresponding to each color after the light intensity adjustment. Furthermore, in the printing operation preprocessing, in addition to the rotation control of the multifaceted mirror, it also includes setting the light-emitting control IC 102 and the laser driver substrate 108 to begin illuminating the LD. After the printing operation preprocessing, the image forming apparatus performs LD initialization (step S1111).

[0056] Then, when the LD is initialized normally (step S1112: Yes), the image forming apparatus enters a state of waiting for the detection of the synchronization detection signal (step S1113). When laser beams corresponding to various colors are sequentially input to the photodetector sensor 104b, the hardware gain control signal selection circuit 202 outputs an appropriate gain signal corresponding to each synchronization lighting timing. Then, when the laser beam is detected normally by the photodetector 104b and the synchronization detection signal is detected by the image forming apparatus (step S1113: Yes), the image forming apparatus performs the adjustment of the write start timing (step S1114) and processing during the printing operation (step S1115). Then, when all printing jobs are completed (step S1116: Yes), the image forming apparatus performs post-printing processing (step S1117). On the other hand, if the LD fails to initialize normally (step S1112: No) and if the synchronization detection signal is not detected (step S1113: No), the image forming apparatus performs forced termination processing of the printing operation (step S1118).

[0057] Figure 12-1 The diagram shown is a flowchart of an example of the color alignment operation of the image forming apparatus according to this embodiment. Figure 12-2 The diagram shown is a flowchart of another example of the printing operation of the image forming apparatus according to this embodiment.

[0058] exist Figure 12-1 In the color alignment operation shown, the image forming apparatus sets the sensitivity of the light detection sensor 104b of the synchronous detection IC 104 (step S1201) and also performs detection preprocessing (step S1202). Then, the image forming apparatus forms a color alignment pattern (step S1203) and detects the color alignment pattern (step S1204). When the detection of the color alignment pattern is successful (step S1205: Yes), the image forming apparatus calculates the correction value (step S1206).

[0059] Then, if the calculated correction value is a normal value (step S1207: Yes), the image forming apparatus updates the color alignment correction amount (step S1208) and also updates the color alignment execution conditions (step S1209). This embodiment is for correction... Figure 9 and Figure 10 The start time shown is when the execution conditions for updating color alignment are updated (step S1209), and the amount of light from the laser beam during the color alignment operation is stored in a storage unit such as a memory. Figure 9 and Figure 10 The image forming apparatus shown has an update system for the correction amount of color alignment and the execution conditions of color alignment, but the update system may also be located outside the image forming apparatus.

[0060] exist Figure 12-2 In the printing operation shown, the image forming apparatus first sets the sensitivity of the light detection sensor 104b (step S1210) and performs printing operation preprocessing (step S1211). Next, the image forming apparatus initializes the LD (step S1212). When the LD is correctly initialized (step S1213: Yes) and a synchronization detection signal is detected (step S1214: Yes), the image forming apparatus reads the execution conditions for color alignment during the printing operation (e.g., the amount of light stored in the storage unit) (step S1215). Next, the image forming apparatus adjusts the write-out start timing (step S1216) and performs processing during the printing operation (step S1217). For example, if there is a difference between the amount of light from the laser beam during the color alignment operation and the current amount of light from the laser beam, the detection timing of the optical detection sensor 104b will deviate from the amount of this difference. Therefore, the image forming apparatus calculates a correction amount based on the characteristic value of this deviation and adjusts the write-out start timing (step S1216). At this point, Figure 12-2 The printing action shown is Figure 11-2 The printing actions shown are different.

[0061] When all printing jobs are completed (step S1218: Yes), the image forming apparatus performs post-printing processing (step S1219). On the other hand, if the LD fails to initialize properly (step S1213: No) or if the synchronization detection signal is not detected (step S1214: No), the image forming apparatus performs forced termination processing of the printing operation (step S1220).

[0062] Thus, according to this embodiment, even if the amount of light from the laser beam incident on the synchronization detection sensor changes due to printing conditions or other factors, false detection caused by stray light or missed detection caused by insufficient light will not occur, and synchronization can be reliably detected.

[0063] Furthermore, in the above embodiments, an example was given of applying the image forming apparatus of the present invention to a multifunctional peripheral device having at least two of the following functions: copying, printing, scanning, and faxing. However, it can also be applied to any of the image forming apparatuses such as copiers, printers, scanners, and faxing devices.

[0064] Examples of embodiments of the present invention are described below.

[0065] <1>

[0066] An image forming apparatus that forms an image by developing an electrostatic latent image formed on a photoreceptor, characterized by having an optical writing device for exposing the photoreceptor, the optical writing device comprising: a light-emitting element that illuminates the photoreceptor; a light-emitting control element that outputs a light-emitting control signal to control the illumination state of the light-emitting element, thereby controlling the light emission of the light-emitting element; a deflection element, which is a multifaceted reflector disposed in the light path from the light-emitting element, and by rotational drive, deflects the light illuminating the surface of the reflector to scan the photoreceptor in one direction; and a synchronous detection element that is illuminated by light from different sources on the photoreceptor. The system includes light from a first-color light-emitting element among the plurality of light-emitting elements used in the formation of the electrostatic latent image of the photoreceptor, and light from a second-color light-emitting element among the plurality of light-emitting elements that is different from the first color, and detects the timing of writing the electrostatic latent image caused by the illumination of light onto the photoreceptor; a gain switching circuit capable of switching the gain of the synchronization detection element; and a gain control signal selection circuit connected to the light emission control signal, which selects one of a plurality of gain control signals connected to the gain switching circuit of the same synchronization detection element and setting the gain of the synchronization detection element according to the light emission control signal.

[0067] <2>

[0068] according to <1> The image forming apparatus is characterized in that: the light emission control element controls the amount of light emitted by the light emission element to be constant during the period when light irradiates from one end of one side of the deflection element to the other end is scanned in one direction.

[0069] <3>

[0070] according to <1> or <2> The image forming apparatus is characterized in that: the single-ended signal in the light emission control signal is connected to the gain control signal selection circuit.

[0071] <4>

[0072] according to <1> or <2> The image forming apparatus is characterized in that: the synchronous lighting signal in the light emission control signal is connected to the gain control signal selection circuit.

[0073] <5>

[0074] according to <1> or <2> The image forming apparatus is characterized in that: the APC signal in the light emission control signal is connected to the gain control signal selection circuit.

[0075] <6>

[0076] according to <5> The image forming apparatus is characterized in that the timing of the APC signal activation overlaps with the timing of synchronous illumination.

[0077] <7>

[0078] according to <1> to <5> The image forming apparatus according to any one of the following is characterized in that: the light writing device has a plurality of light-emitting elements for illuminating a photoreceptor, the plurality of light-emitting elements sharing a synchronous detection signal from the synchronous detection element.

[0079] <8>

[0080] according to <1> to <7> The image forming apparatus according to any one of the following is characterized in that: the gain control signal selection circuit has an initialization function for initializing the state of the gain control signal selection circuit, and outputs an initialization signal from the light emission control element for setting the validity and invalidity of the initialization function.

[0081] <9>

[0082] according to <8> The image forming apparatus is characterized in that: the initialization signal is independent of the light emission control signal used to control the lighting state of the light emission element, and is connected to the light emission control element.

[0083] <10>

[0084] according to <8> The image forming apparatus is characterized in that: the single-ended signal in the light emission control signal is used as an initialization signal.

[0085] <11>

[0086] according to <9> or <10> The image forming apparatus is characterized in that, when a latent image of a scan amount is formed on each of the different photoreceptors by rotational drive of the deflection element, the photoreceptor that first forms a latent image on the time axis is designated as the beginning photoreceptor, and the photoreceptor that last forms a latent image is designated as the last photoreceptor, the initialization function operates during the period from the detection of a synchronous illumination signal associated with the last photoreceptor to the detection of a synchronous illumination signal associated with the beginning photoreceptor.

[0087] <12>

[0088] according to <1> to <11> The image forming apparatus according to any one of the following is characterized in that: there are a plurality of the gain control signals, and at least one of the plurality of gain control signals is connected to a circuit other than the gain control signal selection circuit.

[0089] <13>

[0090] according to <12> The image forming apparatus is characterized in that: during system operation, when updating the characteristic value of the deviation of the image write start timing caused by the gain switching of the synchronization detection element, the gain control signal connected to the gain control signal selection circuit is activated; and during other system operations, the gain control signal connected to the gain control signal selection circuit is activated in such a way that the logic of the gain control signal is fixed.

[0091] <14>

[0092] according to <1> to <13> The image forming apparatus according to any one of the following is characterized in that: the gain control signal selection circuit and the light emission control element are on the same substrate.

[0093] <15>

[0094] according to <9> The image forming apparatus is characterized in that: the gain control signal selection circuit includes a flip-flop and a NAND gate.

Claims

1. An image forming apparatus that forms an image by developing an electrostatic latent image formed on a photoreceptor, characterized in that... An optical writing apparatus having an exposure device for the photoreceptor, the optical writing apparatus comprising: A light-emitting element that illuminates the photoreceptor; A light-emitting control element outputs a light-emitting control signal to control the lighting state of the light-emitting element, thereby controlling the light emission of the light-emitting element; A deflecting element, which is a multifaceted reflector, is placed in the light path of the light emitted from the light-emitting element. By rotating and driving it, the light that hits the surface of the reflector is deflected, thereby scanning the photosensitive element in one direction. A synchronous detection element is irradiated with light from a first-color light-emitting element among a plurality of light-emitting elements used in the formation of the electrostatic latent image of different photoreceptors, and light from a second-color light-emitting element among the plurality of light-emitting elements that is different from the first color, and detects the timing of the writing start of the electrostatic latent image caused by the irradiation of light onto the photoreceptor. A gain switching circuit that can switch the gain of the synchronization detection element; A gain control signal selection circuit is connected to the light emission control signal, and selects one of a plurality of gain control signals that are connected to the gain switching circuit of the same synchronization detection element and set the gain of the synchronization detection element according to the light emission control signal.

2. The image forming apparatus according to claim 1, characterized in that: The light-emitting control element controls the amount of light emitted by the light-emitting element to be constant during the period when light irradiates from one end of one side of the deflection element to the other end in one direction.

3. The image forming apparatus according to claim 1 or 2, characterized in that: The single-ended signal in the light emission control signal is connected to the gain control signal selection circuit.

4. The image forming apparatus according to claim 1 or 2, characterized in that: The synchronous lighting signal in the light emission control signal is connected to the gain control signal selection circuit.

5. The image forming apparatus according to claim 1 or 2, characterized in that: The APC signal in the light emission control signal is connected to the gain control signal selection circuit.

6. The image forming apparatus according to claim 5, characterized in that: The timing of the APC signal activation overlaps with the timing of the synchronous lighting.

7. The image forming apparatus according to claim 1, characterized in that: The optical writing device has a plurality of light-emitting elements for illuminating one of the photoreceptors. The plurality of light-emitting elements share a synchronous detection signal from the synchronous detection element.

8. The image forming apparatus according to claim 1, characterized in that: The gain control signal selection circuit has an initialization function for initializing the state of the gain control signal selection circuit. The light-emitting control element outputs an initialization signal to set the validity and invalidity of the initialization function.

9. The image forming apparatus according to claim 8, characterized in that: The initialization signal is independent of the light-emitting control signal used to control the lighting state of the light-emitting element, and is connected to the light-emitting control element.

10. The image forming apparatus according to claim 8, characterized in that: The single-ended signal in the light emission control signal is used as an initialization signal.

11. The image forming apparatus according to claim 9 or 10, characterized in that: In the case where a latent image of a scan quantity is formed on each of the different photoreceptors by rotational drive of the deflection element, When the photoreceptor that first forms a latent image on the timeline is designated as the beginning photoreceptor, and the photoreceptor that last forms a latent image is designated as the last photoreceptor, The initialization function operates during the period from the detection of the sync lighting signal associated with the last photoreceptor to the detection of the sync lighting signal of the first photoreceptor.

12. The image forming apparatus according to claim 1, characterized in that: There are multiple gain control signals, and at least one of the multiple gain control signals is connected to a circuit other than the gain control signal selection circuit.

13. The image forming apparatus according to claim 12, characterized in that: When the system operates to update the characteristic value of the deviation of the image write start timing caused by the gain switching of the synchronization detection element, the gain control signal connected to the gain control signal selection circuit is activated, and in other system operations, the gain control signal connected to the gain control signal selection circuit is activated in a manner in which the logic of the gain control signal is fixed.

14. The image forming apparatus according to claim 1, characterized in that: The gain control signal selection circuit and the light-emitting control element are on the same substrate.

15. The image forming apparatus according to claim 8, characterized in that: The gain control signal selection circuit includes a flip-flop and a NAND gate.

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