Optical scanning device, image forming device, and control method

Abstract

To provide an optical scanner and the like which can properly perform initialization.SOLUTION: An optical scanner includes: a light emission unit which emits a laser beam; a drive unit which is operated in any of a master state of performing initialization by reading out a storage device and a slave state of driving the light emission unit according to the operation mode corresponding to the signal according to the input signal; and a signal output unit which outputs the signal to the drive unit. The signal output unit outputs a signal of turning the drive unit into the slave state and making the prescribed operation mode when performing initialization of the drive unit. The drive unit performs initialization based on a light amount of the laser beam emitted from the light emission unit driven according to the operation mode based on the signal output from the signal output unit.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an optical scanning device and the like. [Background technology]

[0002] Some image forming devices perform an exposure process in which an electrostatic latent image is formed on the surface of a photosensitive member by scanning the surface of the photosensitive member with a laser beam. In addition, a technique for controlling a laser diode (light-emitting element) used for the exposure process has been proposed.

[0003] For example, a technology has been proposed for stably performing feedback control of a semiconductor laser by storing the gain of the detection output of a light receiving element used for feedback control of the drive current of the semiconductor laser in a non-volatile memory (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-098494 Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, a laser diode driver (LDD, Laser Diode Driver; hereafter simply referred to as "laser driver") is used to control a laser diode. There are digital laser drivers that operate as a master during initialization, performing initialization (for example, setting the bias current) based on data read from an EEPROM, and as a slave during normal operation. The function that automatically sets the laser driver is generally called APC (Automatic Power Control). Using such a laser driver in an optical scanning device enables automatic bias current setting and shading correction functions through digital calculations, improving image quality while reducing the number of external components and costs.

[0006] On the other hand, initializing the laser driver requires a dedicated EEPROM and harness for the laser driver, which increases costs and increases the board area. Such issues were not taken into consideration in the prior art such as Patent Document 1.

[0007] In view of the above-mentioned problems, an object of the present disclosure is to provide an optical scanning device or the like that is capable of performing appropriate initialization. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the optical scanning device of the present disclosure comprises a light emitting unit that emits laser light, a drive unit that operates in either a master state that reads out a memory device and performs initialization according to an input signal, or a slave state that drives the light emitting unit according to an operation mode corresponding to the signal, and a signal output unit that outputs the signal to the drive unit, wherein when initializing the drive unit, the signal output unit outputs a signal that causes the drive unit to enter the slave state and a predetermined operation mode, and the drive unit performs initialization based on the light amount of the laser light emitted from the light emitting unit that has been driven according to the operation mode based on the signal output from the signal output unit.

[0009] The image forming apparatus of the present disclosure comprises a light emitting unit that emits laser light, a drive unit that operates in either a master state that reads a memory device and performs initialization according to an input signal, or a slave state that drives the light emitting unit according to an operation mode corresponding to the signal, a signal output unit that outputs the signal to the drive unit, an image carrying unit that carries an electrostatic latent image formed by irradiation with the laser light, and a fixing unit that fixes an image based on the electrostatic latent image onto recording paper, wherein when initializing the drive unit, the signal output unit outputs a signal that puts the drive unit into the slave state and switches it to a predetermined operation mode, and the drive unit performs initialization based on the light amount of the laser light emitted from the light emitting unit that has been driven according to the operation mode based on the signal output from the signal output unit.

[0010] The control method disclosed herein is a control method for a drive device that operates in either a master state in which a memory device is read and initialized according to an input signal, or a slave state in which an emitting unit that emits laser light is driven according to an operating mode corresponding to the signal, and is characterized in that when initializing the drive device, the control method includes an output step of outputting a signal that puts the drive device into the slave state and sets it to a predetermined operating mode, and an initialization step in which the drive device performs initialization based on the amount of laser light emitted from the emitting unit that has been driven according to the operating mode based on the output signal. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to provide an optical scanning device or the like that is capable of performing appropriate initialization. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view of an image forming apparatus according to a first embodiment. [Figure 2] 1 is a block diagram showing a functional configuration of an image forming apparatus according to a first embodiment. [Figure 3] FIG. 2 is a block diagram of a digital LDD according to the first embodiment. [Figure 4] FIG. 1 is a diagram showing IP characteristics of a laser diode (LD). [Figure 5] 1 is a block diagram showing a functional configuration of an optical scanning device according to a first embodiment. [Figure 6] FIG. 1 is a block diagram showing a functional configuration of a conventional optical scanning device. [Figure 7] 3 is a diagram illustrating an example of connection between a digital LDD and a light-emitting unit in the first embodiment. FIG. [Figure 8] FIG. 3 is a flowchart showing the flow of main processing in the first embodiment. [Figure 9] FIG. 4 is a flowchart showing the flow of initialization processing for each channel in the first embodiment. [Figure 10] FIG. 3 is a diagram showing signals input to a digital LDD in the first embodiment. [Figure 11] FIG. 10 is a flowchart showing the flow of main processing in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an embodiment for carrying out the present disclosure will be described with reference to the drawings. Note that the following embodiment is an example for explaining the present disclosure, and the technical scope of the invention described in the claims is not limited to the following description.

[0014] [1. First embodiment] In the first embodiment, a case will be described in which an optical scanning device according to the present disclosure is mounted in an image forming apparatus 10. The image forming apparatus 10 is an information processing apparatus having a copy function, a scan function, a document print function, etc., and is also called an MFP (Multi-Function Printer / Peripheral) or a multifunction machine.

[0015] [1.1 Functional Configuration] [1.1.1 Functional configuration of image forming device] The functional configuration of the image forming apparatus 10 of this embodiment will be described below. Fig. 1 is an external perspective view of the image forming apparatus 10, and Fig. 2 is a block diagram showing the functional configuration of the image forming apparatus 10.

[0016] As shown in FIG. 2, the image forming apparatus 10 includes a control unit 100, an image input unit 110, an image forming unit 120, a display unit 140, an operation unit 150, a storage unit 160, and a communication unit 170.

[0017] The control unit 100 is a functional unit for controlling the entire image forming apparatus 10. The control unit 100 realizes various functions by reading and executing various programs stored in the storage unit 160, and is configured, for example, by one or more arithmetic units (CPUs (Central Processing Units)). The control unit 100 may also be configured as an SoC (System on a Chip) having multiple functions among those described below.

[0018] The control unit 100 executes a program stored in the storage unit 160 to function as an image processing unit 102. The image processing unit 102 performs various image-related processes. For example, the image processing unit 102 performs sharpening processing and gradation conversion processing on an image input by the image input unit 110.

[0019] The image input unit 110 inputs an image to the image forming apparatus 10. For example, the image input unit 110 is configured with a scanner device or the like that reads an original placed on a platen. The scanner device is a device that converts an image into an electrical signal using an image sensor such as a CCD (Charge Coupled Device) or a CIS (Contact Image Sensor), and quantizes and encodes the electrical signal. Note that the image input unit 110 may also be configured with an automatic document feeder (SPF, Single Pass Feeder) and a scanner device or the like that reads an image of an original transported by the automatic document feeder.

[0020] Image forming unit 120 forms (prints) an image on a recording medium such as recording paper. Image forming unit 120 is configured, for example, by a printing device such as a laser printer that uses an electrophotographic method. Image forming unit 120 feeds recording paper from paper feed tray 138 in FIG. 1, forms an image on the surface of the recording paper, and discharges the recording paper from paper discharge tray 139.

[0021] The image forming unit 120 also includes a PCU (Process Control Unit) 122, an ASIC (Application specific integrated circuit) 124, a digital LDD (Laser Diode Driver) 126, an EEPROM (Electrically Erasable Programmable Read-Only Memory) 128, a light emitting unit 130, a light receiving unit 132, an image carrying unit 134, and a fixing unit 136.

[0022] The PCU 122 controls the image formation process. For example, the PCU 122 controls and monitors the movement of motors related to the transport of recording paper, a sorter, etc., based on the control of the control unit 100. The PCU 122 also controls the ASIC 124 by sending predetermined data and signals to the ASIC 124. The PCU 122 is composed of a board, a circuit, etc.

[0023] The ASIC 124 controls the digital LDD 126 based on the control of the PCU 122. The ASIC 124 controls the digital LDD 126 by transmitting (outputting) predetermined data and signals to the digital LDD 126. In other words, the ASIC 124 is a signal output unit that outputs signals to the digital LDD 126.

[0024] The digital LDD 126 drives the light emitting unit 130, which is a laser diode (LD). That is, the digital LDD 126 is a drive unit that drives the light emitting unit 130. In addition, as settings for driving the light emitting unit 130, the digital LDD 126 sets a current (LD current, drive current) to be output to drive the light emitting unit 130 and sets a bias current.

[0025] The digital LDD 126 may implement a digital APC (Automatic Power Control) function for maintaining the optical output (LD light amount) of the light emitting unit 130 constant. The digital LDD 126 may also include a register for storing data. The digital LDD 126 is configured with a substrate, a circuit, etc. The detailed configuration of the digital LDD 126 will be described later.

[0026] The EEPROM 128 is a rewritable read-only memory. The EEPROM 128 stores data related to the settings of the digital LDD 126. The data related to the settings of the digital LDD 126 is stored in advance in the EEPROM 128. Note that the data stored in the EEPROM 128 may be rewritable by a service person or the like.

[0027] The light-emitting unit 130 is a light-emitting element that emits laser light. The light-emitting unit 130 is configured, for example, by a laser diode (LD) that increases or decreases optical output in proportion to the amount of current that exceeds the bias current among the input currents. In this embodiment, the light-emitting unit 130 is connected to the digital LDD 126 and emits laser light based on the current output from the digital LDD 126. That is, the light-emitting unit 130 emits laser light based on the control of the digital LDD 126.

[0028] The light receiving unit 132 is a light receiving element that receives light. The light receiving unit 132 is configured, for example, by a photodiode (PD) that receives incident light and outputs a light receiving signal (for example, a current) based on the intensity of the received light. In this embodiment, the light receiving unit 132 is provided near the light emitting unit 130, thereby receiving the laser light emitted by the light emitting unit 130 and outputting a current according to the intensity of the received light.

[0029] The image carrier 134 is charged and forms an electric latent image (electrostatic latent image) by being irradiated with laser light from the light emitting unit 130. The image carrier 134 is a so-called photosensitive body (photosensitive drum). The image carrier 134 also transfers the image onto the recording paper by adhering toner thereto and then transferring the toner to the recording paper.

[0030] The fixing unit 136 fixes (fuses) the toner (image based on the electrostatic latent image) transferred onto the recording paper. The fixing unit 136 is composed of, for example, a fixing roller and a pressure roller.

[0031] The display unit 140 displays various types of information. The display unit 140 is configured by a display device such as an LCD (Liquid Crystal Display), an organic EL (Electro-Luminescence) display, or a micro LED (Light Emitting Diode) display.

[0032] The operation unit 150 accepts operation instructions from a user who uses the image forming apparatus 10. The operation unit 150 is configured with input devices such as key switches (hard keys) and touch sensors. The touch sensor may detect input by contact (touch) using any common detection method, such as a resistive film method, an infrared method, an electromagnetic induction method, or a capacitance method. The image forming apparatus 10 may be equipped with a touch panel in which the display unit 140 and the operation unit 150 are integrally formed.

[0033] The storage unit 160 stores various programs and various data necessary for the operation of the image forming apparatus 10. The storage unit 160 is configured by a storage device such as a solid state drive (SSD) or a hard disk drive (HDD), which is a semiconductor memory.

[0034] The communication unit 170 communicates with external devices via a LAN (Local Area Network) or WAN (Wide Area Network). The communication unit 170 may be configured with a communication device or a communication module such as a NIC (Network Interface Card) used in a wired / wireless LAN, and may have an interface connectable to a network. The communication unit 170 may also be connected to a communication network such as a public line network, a LAN, or the Internet, and may be capable of transmitting data to an external device via the communication network by a communication method such as facsimile or email.

[0035] [1.1.2 Functional configuration of digital LDD] 2, the digital LDD 126 of this embodiment includes an operation mode setting unit 1261, a function setting unit 1262, a light amount correction unit 1263, an APC control unit 1264, and a PD detection unit 1265. Also, FIG. 3 is a block diagram of the digital LDD 126.

[0036] 3, DATAP1, DATAN1, DATAPx, DATANx, ILD1, ILDx, P0, P1, P2, P3, P4, P5, DOI / DIO, and PD indicate pins (interfaces) for inputting and outputting signals (for example, voltages and currents) to and from external devices. The pins will be explained below.

[0037] (1)DATAP1, DATAN1, DATAPx, DATANx, DATAPx and DATANx are pins for inputting data (LVDS (Low Voltage Differential Signaling)) corresponding to channel x.

[0038] A channel (also referred to as CH) is an interface that outputs a drive current (LD current) to be supplied to the light emitting unit 130 (LD) to emit laser light. For example, DATAP1 and DATAN1 are pins that input data to CH1.

[0039] The digital LDD 126 may have multiple channels. In this embodiment, the digital LDD 126 will be described as having four channels. That is, the digital LDD 126 has DATAPx (x is any value from 1 to 4) and DATANx (x is any value from 1 to 4) as pins for inputting data.

[0040] (2) ILD1, ILDx ILDx is a pin that outputs the LD current of channel x based on the data input from DATAPx and DATANx.

[0041] (3)DOI / DIO DOI / DIO are pins for inputting and outputting data to and from a storage device (for example, the storage device 200 shown in FIG. 3) externally connected to the digital LDD 126. The storage device externally connected to the digital LDD 126 is, for example, an EEPROM.

[0042] (4)P0, P1, P2, P3, P4, P5 P0 is a pin for setting the state of the digital LDD 126. P1, P2, P3, P4, and P5 are pins (parallel interface) for setting the operation mode of the digital LDD 126.

[0043] To P0 to P5, a signal is input, either H, which is a high voltage level, or L, which is a voltage level lower than H. In the following explanation, when L is input to Pn (n is any value from 0 to 5), it will be written as Pn=L, and when H is input to Pn, it will be written as Pn=H.

[0044] In this embodiment, the digital LDD 126 will be described as operating in either of two states: a slave state and a master state. The digital LDD 126 is in the slave state when P0=L, and in the master state when P0=H.

[0045] The slave state is a state in which the digital LDD 126 operates according to an operation mode set in response to signals input to P1, P2, P3, P4, and P5, and the light-emitting unit 130 connected to the digital LDD 126 is driven. The operation mode is a mode indicating an operation performed by the digital LDD 126 when the digital LDD 126 is in the slave state. That is, when the digital LDD 126 is in the slave state, the digital LDD 126 performs a predetermined operation, such as driving the light-emitting unit 130 in response to a signal input from an external device. The predetermined operation is, for example, an operation of outputting an LD current from each channel (ILDx) in response to data (LVDS) corresponding to each channel, or an operation of outputting an LD current in response to the operation mode. That is, when in the slave state, the digital LDD 126 performs a normal operation as a laser diode driver.

[0046] P1 is a pin for inputting a signal (enable signal) that sets whether or not the digital LDD 126 is enabled.

[0047] P2 is a pin that inputs a signal (non-APC mode setting signal) that switches whether or not APC is executed. When P2=H, it indicates that APC is not executed (non-APC), and when P2=L, it indicates that APC is executed.

[0048] P3 and P4 are pins for inputting a signal (channel designation signal) for designating a channel on which APC is to be executed.

[0049] P5 is a pin for inputting a signal (APC mode switching signal) for switching the operation mode of the digital LDD 126 between the APC-H mode and the APC-L mode.

[0050] The operation mode is set by an operation mode setting unit 1261, which will be described later. The operation mode set by the operation mode setting unit 1261, and the APC-H mode and APC-L mode will be described later.

[0051] On the other hand, the master state is a state in which data is read from a storage device (e.g., storage device 200 shown in FIG. 3) externally attached to the digital LDD 126, and an initial APC sequence is executed in accordance with the read data, thereby initializing (initializing) the digital LDD 126. Initialization refers to the digital LDD 126 performing various settings so that the digital LDD 126 can appropriately drive the light-emitting unit 130. During initialization, the digital LDD 126 adjusts the LD light intensity and sets the bias current, for example. When in the master state, the digital LDD 126 actively executes the initial APC sequence regardless of the operation mode set by the signals input to P1 to P5.

[0052] The initial APC sequence is a sequence that initializes each channel (for example, setting the LD current and bias current) in the order of CH1, CH2, CH3, and CH4. Note that when the initial APC sequence is executed, the digital LDD 126 may store values ​​in registers based on data acquired from a storage device externally attached to the digital LDD 126.

[0053] In this way, when the digital LDD 126 is in the master state, the digital LDD 126 performs the initial APC sequence to initialize (start up) the digital LDD 126. Furthermore, when the execution of the initial APC sequence ends and the digital LDD 126 enters the slave state (P0=L), the digital LDD 126 performs normal operation.

[0054] (5)PD PD is a pin for inputting the current output from the light receiving unit 132.

[0055] Next, the functional units constituting the digital LDD 126 will be described. The operation mode setting unit 1261 sets the operation mode of the digital LDD 126 based on signals input to pins P1 to P5, except when the digital LDD 126 is in a reset state (until it becomes possible to input external signals after power-on) or when it is in a master state. The signals input to pins P1 to P5 are output from the ASIC 124. In this way, the digital LDD 126 is controlled by the ASIC 124.

[0056] The operation modes set by the operation mode setting unit 1261 include the following operation modes. (1) DISABLE mode (2) CH1 initialization mode (3) CH2 initialization mode (4) CH3 initialization mode (5) CH4 initialization mode (6) OFF mode Each operation mode will be explained below.

[0057] (1) DISABLE mode The DISABLE mode is a mode in which the output current is shut down in all channels of the digital LDD 126. The DISABLE mode is set when P1=L. In this case, the digital LDD 126 does not output current from each channel, regardless of the inputs to P2 to P5 or the data (LVDS) input.

[0058] (2) CH1 initialization mode CH1 initialization mode is a mode for initializing CH1. CH1 initialization means adjusting the LD light intensity related to CH1 and setting the bias current. CH1 initialization mode is when P1=H, P2=L, and further P3=L and P4=L.

[0059] In particular, when P5=H, the operation mode setting unit 1261 sets the operation mode of the digital LDD 126 to the APC-H mode of CH1 (first operation mode). On the other hand, when P5=L, the operation mode setting unit 1261 sets the operation mode of the digital LDD 126 to the APC-L mode of CH1 (second operation mode). That is, the CH1 initialization mode corresponds to the case where the operation mode of the digital LDD 126 is either the APC-H1 mode or the APC-L1 mode.

[0060] The APC-H mode of CHx will be referred to as APC-Hx mode (x is any value from 1 to 4), and the APC-L mode of CHx will be referred to as APC-Lx mode (x is any value from 1 to 4).

[0061] In the APC-Hx mode, the digital LDD 126 controls the output current of the IDAC_SW (IDAC_SWx) of the CHx so that the light intensity of the light-emitting unit 130 (LD) connected to the ILDx becomes a preset target light intensity (first light intensity). The IDAC_SW is a circuit that adjusts the output of the switching current. The digital LDD 126 also sets the bias current and the switching current based on the convergence value of the previous APC-Hx mode (digital convergence value of the LD current) and the convergence value of the previous APC-Lx mode. In other words, the digital LDD 126 executes a specific APC sequence for the CHx.

[0062] By executing a specific APC sequence, the digital LDD 126 drives the light-emitting unit 130 connected to CHx, causing the light-emitting unit 130 to emit laser light. Furthermore, the digital LDD 126 changes the settings of IDAC_SWx and IDAC_BIAS (IDAC_BIASx) of CHx based on the light intensity of the emitted laser light. Note that IDAC_BIAS is a circuit that adjusts the output of bias current.

[0063] On the other hand, in the APC-Lx mode, the digital LDD 126 controls the output current of the IDAC_SWx so that the light intensity of the light emitting unit 130 (LD) connected to the ILDx becomes a second light intensity (a second light intensity) smaller than the light intensity in the APC-Hx mode. The light intensity in the APC-Lx mode is, for example, a light intensity equivalent to P0 / 3 when the light intensity in the APC-Hx mode is P0.

[0064] Furthermore, when the operation mode of the digital LDD 126 is switched to the APC-Hx mode or the APC-Lx mode, a predetermined current is output to the light-emitting unit 130 connected to the ILDx, and laser light is emitted from the light-emitting unit 130. Furthermore, the digital LDD 126 detects the light intensity of the emitted laser light, and based on the detected light intensity, the LD light intensity, bias current, etc. are set in a light intensity correction unit 1263 and an APC control unit 1264, which will be described later.

[0065] 4 is a diagram showing the IP characteristics of the laser diode (LD) constituting the light-emitting unit 130 when the operation mode of the digital LDD 126 is switched between APC-H mode and APC-L mode. The horizontal axis of FIG. 4 represents the LD current, and the vertical axis of FIG. 4 represents the LD light intensity.

[0066] M1 in Fig. 4 is the intersection point between the value of the LD current (P0) input to the light-emitting unit 130 and the value of the LD light intensity in the APC-H mode. M2 in Fig. 4 is the intersection point between the value of the LD current (P0 / 3) input to the light-emitting unit 130 and the value of the LD light intensity in the APC-L mode. The digital LDD 126 estimates the intersection point between the line passing through M1 and M2 and the axis of the LD current as the threshold current Ith of the light-emitting unit 130 of interest.

[0067] Moreover, the digital LDD 126 sets a bias current (Ibias) based on the estimated threshold current Ith and a value (a code value equivalent to Ith-Ibias) that is set in advance in a register R_BIAS_COEF of the digital LDD 126.

[0068] By repeatedly inputting H or L alternately to P5 multiple times, the operation mode of the digital LDD 126 switches between the APC-H mode (APC-H1) of CH1 and the APC-L mode (APC-L1) of CH1, and CH1 is initialized. By switching the operation mode of the digital LDD 126 between APC-H1 and APC-L1 multiple times, the light-emitting unit 130 is driven, and the LD light intensity, bias current, etc. are set multiple times according to the light intensity of the light-emitting unit 130 each time the operation mode is switched. By setting the values ​​of the bias current, etc. multiple times, the digital LDD 126 can bring the values ​​of the bias current, etc. closer to the values ​​set in the master state. In this way, even when the digital LDD 126 is in the slave state, the digital LDD 126 can set the values ​​of the bias current, etc. of a specific channel to appropriate values ​​by switching the operation mode according to the signal output by the ASIC 124.

[0069] (3)~(5) CH2 initialization mode~CH4 initialization mode The CH2 initialization mode is a mode for initializing CH2. The CH2 initialization mode is when P1=H, P2=L, and further, P3=L, P4=H. In this case, by repeatedly inputting H or L to P5 multiple times, the CH2 APC-H mode (APC-H2) and the CH2 APC-L mode (APC-L2) are switched, and CH2 initialization is performed.

[0070] When P1=H and P2=L, if P3=H and P4=L, this corresponds to the CH3 initialization mode, and if P3=H and P4=H, this corresponds to the CH4 initialization mode.

[0071] (6) OFF (standby) mode The OFF mode is a mode in which an LD current is output from the digital LDD 126 in response to input of data (LVDS), and is a mode in which input of data is awaited. The OFF mode is set when P1=H and P2=H.

[0072] When the digital LDD 126 is in the master state, the function setting unit 1262 reads the external EEPROM and initializes the digital LDD 126 (for example, sets the target light intensity).

[0073] The light intensity correction unit 1263 receives a convergence value in the APC-Hx mode, generates a signal for changing the setting of IDAC_SWx (190a in FIG. 3), and outputs the signal to IDAC_SWx. As a result, the light intensity correction unit 1263 corrects the LD light intensity of the light-emitting unit 130 connected to CHx. The light intensity correction unit 1263 may also perform shading correction to correct the LD light intensity in the main scanning direction at the irradiation destination of the LD light.

[0074] The APC control unit 1264 controls the execution of APC and sets the bias current. The APC control unit 1264 receives a comparison result between the voltage output from the PD detection unit 1265 and the voltage indicating the APC target value output from the DAC_APC (190b in FIG. 3), sets the bias current, and generates a signal for changing the setting of IDAC_BIASx (190c in FIG. 3). The APC control unit 1264 also outputs the generated signal to IDAC_BIASx. As a result, the APC control unit 1264 sets the bias current.

[0075] The PD detector 1265 receives the current output from the light receiving unit 132, detects the amount of light, and outputs a voltage corresponding to the detected amount of light.

[0076] Next, the flow of outputting a current from ILD1 will be described. First, the LVDS driver 1 (190d in FIG. 3) outputs an LD current based on the voltages input from DATAP1 and DATAN1.

[0077] IDAC_BIAS1 sets a bias current to be output by inputting a signal output from the APC control unit 1264, and outputs a predetermined bias current. IDAC_SW1 sets a switching current to be output by inputting a signal output from the light intensity correction unit 1263, and outputs a predetermined switching current.

[0078] Furthermore, a current Ild1 based on the LD current output from the LVDS driver 1, the bias current output from IDAC_BIAS1, and the switching current output from IDAC_SW1 is output from ILD1. The current Ild1 is input to the light-emitting unit 130 (light-emitting unit 130a) connected to CH1. This causes the light-emitting unit 130a to emit laser light. In this way, a current is output from ILD1 by the configuration included in 191 in FIG. 3.

[0079] For CH2 to CH4, as shown by 194 in FIG. 3, a current Ildx is output from ILDx based on the LD current output from the LVDS driver x, the bias current output from IDAC_BIASx, and the switching current output from IDAC_SWx.

[0080] The digital LDD 126 may be a digital type laser driver that digitally controls the operation mode setting unit 1261, the function setting unit 1262, the light amount correcting unit 1263, and the APC control unit 1264.

[0081] [1.1.3 Configuration of optical scanning device] 5 is a block diagram showing the functional configuration of the optical scanning device of the image forming apparatus 10. As shown in FIG. 5, the optical scanning device of the image forming apparatus 10 is made up of a PCU 122, an ASIC 124, a digital LDD 126, an EEPROM 128, and a light emitting unit 130.

[0082] The PCU 122 and the ASIC 124 communicate (transfer) data and signals using, for example, an SCI (Serial Communication Interface). Similarly, the ASIC 124 and the digital LDD 126 communicate data using, for example, a Microwire. The ASIC 124 and the EEPROM 128 communicate data using, for example, an I 2 Data transfer is performed using C.

[0083] In this embodiment, the digital LDD 126 is always in a slave state. When the data stored in the EEPROM 128 is reflected in the digital LDD 126, the data stored in the EEPROM 128 is transferred from the EEPROM 128 to the digital LDD 126 via the ASIC 124, as shown in A1 of FIG.

[0084] The image forming apparatus 10 may also be configured with a laser beam scanner unit (LSU) including the optical scanning device shown in Fig. 5. In addition to the optical scanning device, the LSU includes a polygon mirror (polarizing device) for deflecting the laser light emitted from the light emitting unit 130 in the main scanning direction, an fθ lens for focusing the deflected laser light on the surface of the image carrier 134, and a predetermined mirror. In this case, the ASIC 124 may be called an LSU ASIC.

[0085] FIG. 6 shows a block diagram illustrating the functional configuration of a conventional optical scanning device. In the conventional case, in addition to an EEPROM 128 (EEPROM 128a) that stores data to be input to the ASIC 124, a dedicated EEPROM 128 (EEPROM 128b, corresponding to the storage device 200 in FIG. 3) for initializing the digital LDD 126 was required. Furthermore, when initializing the digital LDD 126, the ASIC 124 had to communicate with the digital LDD 126 using a microwire or the like to switch between a master state and a slave state. Specifically, when initializing the digital LDD 126, the digital LDD 126 had to be set to the master state (LDD master), and during normal operation of the digital LDD 126, the digital LDD 126 had to be set to the slave state (LDD slave). In this case, if the ASIC 124 did not have a microwire communication function, the ASIC 124 had to communicate with the PCU 122 using an SCI and transmit a predetermined signal to the digital LDD 126 via the PCU 122, as shown in FIG. 6. For this reason, a harness was required between the ASIC 124, the PCU 122, and the digital LDD 126.

[0086] 5, it is possible to eliminate the dedicated EEPROM and dedicated harness (for PCU connection / EEPROM connection) that were required to initialize the digital LDD 126. In other words, it is possible to omit the configuration of the portion enclosed by the dotted line in FIG. 6.

[0087] FIG. 7 shows an example of the configuration and connection of the digital LDD 126 and the light-emitting unit 130 in this embodiment. FIG. 7(a) is a diagram showing the configuration of the digital LDD 126 and the light-emitting unit 130 when the image forming apparatus 10 is a two-beam model. The two-beam model is a model in which two laser beams are used to form an electrostatic latent image corresponding to one color component. In the two-beam model, when a digital LDD 126 having four channels (a four-channel digital LDD) is used, eight light-emitting units 130 (light-emitting units 130a to 130h) are connected to two digital LDDs 126 (digital LDD 126a and digital LDD 126b). In this case, the light-emitting unit 130a and the light-emitting unit 130b are used to form an electrostatic latent image of the K color component. Similarly, light-emitting units 130c and 130d are used to form an electrostatic latent image of the C color component, light-emitting units 130e and 130f are used to form an electrostatic latent image of the M color component, and light-emitting units 130g and 130h are used to form an electrostatic latent image of the Y color component. Furthermore, light-emitting units 130a to 130d are connected to CH1 to CH4 of digital LDD 126a, and light-emitting units 130e to 130h are connected to CH1 to CH4 of digital LDD 126b.

[0088] FIG. 7B is a diagram showing the configuration of the digital LDD 126 and the light-emitting unit 130 when the image forming apparatus 10 is a 1-beam model. The 1-beam model is a model in which one laser beam is used to form an electrostatic latent image corresponding to one color component. When a digital LDD 126 having four channels is used in the 1-beam model, four light-emitting units 130 (light-emitting units 130a to 130d) are connected to one digital LDD 126. In this case, the light-emitting unit 130a is used to form an electrostatic latent image of the K color component, the light-emitting unit 130b is used to form an electrostatic latent image of the C color component, the light-emitting unit 130c is used to form an electrostatic latent image of the M color component, and the light-emitting unit 130d is used to form an electrostatic latent image of the Y color component. The light-emitting units 130a to 130d are connected to CH1 to CH4 of the digital LDD 126.

[0089] The configuration shown in FIG. 7 is an example, and for example, a two-channel digital LDD may be used instead of the four-channel digital LDD.

[0090] [1.2 Processing flow] 8 and 9, a description will be given of the flow of main processes executed when initializing the digital LDD 126 in this embodiment. In this embodiment, the ASIC 124 executes the processes shown in Fig. 8 and 9 under the control of the control unit 100, thereby initializing each channel of the digital LDD 126.

[0091] [1.2.1 Main Processing] First, the flow of the main processing shown in Fig. 8 will be described. The ASIC 124 puts the digital LDD 126 into a slave state (step S100). That is, the ASIC 124 causes the digital LDD 126 to perform normal operation. For example, the ASIC 124 outputs (applies) a signal (voltage) to P0 of the digital LDD 126 to put the digital LDD 126 into a slave state, setting P0=L.

[0092] Next, the ASIC 124 assigns 1 to the variable x and selects CHx (the xth channel) (step S102 → step S104). Furthermore, the ASIC 124 executes a process for performing initialization for each channel (channel-specific initialization process) for the selected channel (step S106). The channel-specific initialization process will be described in detail later.

[0093] Next, the ASIC 124 determines whether all channels have been selected (step S108). If all channels have not been selected, the ASIC 124 increments the variable x by substituting the value of x+1 for the variable x, and returns to step S104 (step S108; No → step S110 → step S104).

[0094] On the other hand, if all the channels have been selected, the ASIC 124 sets the operation mode of the digital LDD 126 to the OFF mode (standby mode) and ends the processing of FIG. 8 (step S108; Yes→step S112).

[0095] [1.2.2 Initialization process for each channel] The flow of the channel-specific initialization process will be described with reference to Fig. 9. The ASIC 124 switches the operation mode of the digital LDD 126 to the APC-H mode of the channel selected in step S104 of Fig. 8 (step S150). For example, the ASIC 124 outputs (applies) predetermined signals (voltages) to P1 to P5 so that the operation mode of the digital LDD 126 becomes the APC-Hx mode. As a result, the digital LDD 126 detects the light intensity in APC-H, and executes a specific APC sequence for the channel selected in step S104 of Fig. 8.

[0096] Next, the ASIC 124 switches the operation mode of the digital LDD 126 to the APC-L mode of the channel selected in step S104 of Fig. 8 (step S152). For example, the ASIC 124 outputs (applies) predetermined signals (voltages) to P1 to P5 so that the operation mode of the digital LDD 126 becomes the APC-Hx mode. As a result, the digital LDD 126 detects the light intensity in APC-L.

[0097] Next, the ASIC 124 determines whether or not the end condition of the channel-specific initialization process is satisfied (step S154). The end condition is, for example, the following condition. (1) Switching to APC-H mode (or APC-L mode) a certain number of times (2) A predetermined time has elapsed since the process shown in Figure 9 began. (3) The change in the LD light intensity and bias current settings is less than the specified amount. If any one of the above conditions is met, the ASIC 124 determines that the termination condition is met.

[0098] If the termination condition is not satisfied, the ASIC 124 returns to step S150 (step S154; No→step S150). In this way, the ASIC 124 alternately switches the operation mode of the digital LDD 126 between the APC-H mode of the channel selected in step S104 of Fig. 8 and the APC-L mode of the channel. On the other hand, if the termination condition is satisfied, the ASIC 124 terminates the processing shown in Fig. 9 (step S154; Yes).

[0099] 8 and 9, the ASIC 124 switches the operation mode of the digital LDD 126 between APC-H and APC-L for each channel. At this time, a specific APC sequence is executed in the digital LDD 126, and the LD light intensity, bias current, etc. for the specific channel are set. In this way, the ASIC 124 can perform initialization for each channel of the digital LDD 126 having multiple channels.

[0100] That is, when initializing the digital LDD 126, the ASIC 124 sets the digital LDD 126 to a slave state instead of a master state, and outputs a predetermined signal to the digital LDD 126. As a result, the ASIC 124 switches the operation mode of the digital LDD and causes the digital LDD 126 to perform a specific APC sequence based on the amount of laser light emitted by driving the light-emitting unit 130 in accordance with the operation mode. As a result, the ASIC 124 initializes a specific channel in the digital LDD 126. Furthermore, the ASIC 124 can initialize all channels of the digital LDD 126 by repeating the initialization of a specific channel.

[0101] [1.3 Example of operation] 10, a description will be given of signals input from the ASIC 124 to the digital LDD 126 at the time of initialization of the digital LDD 126 in this embodiment. Fig. 10 is a diagram showing signals (H or L) output from the ASIC 124 to P1 to P5 of the digital LDD 126 and the operation modes of the digital LDD 126 corresponding to the signals.

[0102] 10 indicates a signal (P1=L) output from the ASIC 124 to the digital LDD 126 in order to set the operation mode of the digital LDD 126 to the DISABLE mode. At this time, the ASIC 124 may read data from the EEPROM 128 and set a predetermined value in a register of the digital LDD 126 based on the data.

[0103] 10 indicates signals (P1=H, P2=L, P3=L, P4=L) output from the ASIC 124 to the digital LDD 126 to set the operation mode of the digital LDD 126 to the CH1 initialization mode. In particular, t2a in Fig. 10 indicates a signal (P5=H) to set the operation mode of the digital LDD 126 to the APC-H mode (APC-H1) of CH1, and t2b in Fig. 10 indicates a signal (P5=L) to set the operation mode of the digital LDD 126 to the APC-L mode (APC-L1) of CH1.

[0104] The operation mode of the digital LDD 126 is repeatedly switched between APC-H1 and APC-L1 multiple times, causing the light emitting unit 130 to emit a laser beam according to the operation mode, and CH1 is initialized based on the light intensity of the laser beam. In this way, an APC sequence for a specific channel (specific APC sequence) is executed.

[0105] (3) CH2 initialization mode ~ CH4 initialization mode 10 indicates signals (P1=H, P2=L, P3=L, P4=H) output from the ASIC 124 to the digital LDD 126 to set the operation mode of the digital LDD 126 to the CH2 initialization mode. Similarly, t4 in Fig. 10 indicates signals (P1=H, P2=L, P3=H, P4=L) to set the operation mode of the digital LDD 126 to the CH3 initialization mode. t5 in Fig. 10 indicates signals (P1=H, P2=L, P3=H, P4=H) to set the operation mode of the digital LDD 126 to the CH4 initialization mode. 10, the ASIC 124 also repeatedly outputs a signal (P5=H) for setting the operation mode of the digital LDD 126 to the APC-H mode (APC-Hx) of CHx and a signal (P5=L) for setting the operation mode of the digital LDD 126 to the APC-L mode (APC-Lx) of CHx to the digital LDD 126. This causes CH2, CH3, and CH4 to be initialized.

[0106] 10 indicates signals (P1=H, P2=H) output from the ASIC 124 to the digital LDD 126 to set the operation mode of the digital LDD 126 to the OFF (standby) mode. In the OFF mode, the digital LDD 126 outputs a predetermined LD current in each channel of the digital LDD 126 in response to input data (LVDS).

[0107] In this way, initialization (slave initialization) of any channel can be performed by combining H or L signals input to P2, P3, and P4. Furthermore, by repeatedly switching the signal input to P5 between H and L multiple times, the operation mode of the digital LDD 126 is switched between APC-H mode and APC-L mode, and digital calculation errors related to bias current and switching current are absorbed. At this time, by switching between APC-H mode and APC-L mode multiple times, the ASIC 124 can properly initialize the channel of the digital LDD 126.

[0108] The initialization of the digital LDD 126 may be performed automatically when the image forming apparatus 10 is powered on, or may be performed based on a user operation. By initializing the digital LDD 126 in this way, the user can use the image forming apparatus 10 with the optical scanning device in a state where it operates properly.

[0109] As described above, the optical scanning device of this embodiment is an optical scanning device using a digital type laser driver that is in a master state during initialization and in a slave state during normal operation, and the laser driver is also in a slave state when the laser driver is initialized. The optical scanning device of this embodiment then executes a specific APC sequence when the laser driver is in the slave state, thereby initializing a specific channel. Because the digital LDD, which is the laser driver, can be initialized while the digital LDD remains fixed in the slave state, communication control within the optical scanning device is simplified.

[0110] Furthermore, by providing the ASIC with Microwire communication functionality, it is no longer necessary to communicate via a PCU to control the laser driver, reducing the number of harnesses required. Also, because the laser driver can be initialized while remaining fixed in slave status, the dedicated EEPROM for the laser driver, which is required for initialization, can be eliminated. As a result, costs can be reduced.

[0111] Furthermore, in the optical scanning device of this embodiment, by connecting multiple light-emitting units to one laser driver, it becomes possible for one laser driver to irradiate multiple image carriers (photosensitive drums) with laser light. This reduces the number of laser drivers required for the optical scanning device, reduces the board area of ​​the optical scanning device, and also reduces costs.

[0112] [2. Second Embodiment] Next, a second embodiment will be described. The second embodiment is an embodiment of an optical scanning device that can execute a process for initializing only a specific channel among the channels provided in a digital LDD, in addition to the process described in the first embodiment. In this embodiment, FIG. 8 of the first embodiment is replaced with FIG. 11. Note that the same processes are assigned the same reference numerals, and descriptions thereof will be omitted.

[0113] The main processing executed by the ASIC 124 in this embodiment will be described with reference to Fig. 11. In this embodiment, after the ASIC 124 puts the digital LDD 126 into a slave state, it determines whether the output mode is a monochrome mode (step S200). The monochrome output mode refers to a case where an image forming apparatus 10 (a color machine) capable of color output does not perform color output but performs monochrome output. In other words, this refers to a mode in which an image is formed using only K toner.

[0114] In the monochrome mode, the ASIC 124 assigns 1 to the variable x (step S200; Yes → step S102), and determines whether or not CHx is a K-color LD channel (step S202). That is, the ASIC 124 determines whether or not CHx is a channel that outputs an LD current to the light-emitting unit 130 used to form an electrostatic latent image of the K-color component.

[0115] If CHx is a K-color LD channel, the ASIC 124 selects the CHx (step S202; Yes → step S104) and executes channel-specific initialization processing for the CHx (step S106). Note that if CHx is not a K-color LD channel in step S202, the ASIC 124 omits the processing of steps S104 and S106, thereby omitting the channel-specific initialization processing for CHx.

[0116] Next, the ASIC 124 executes the processes from step S108 to step S 112. As a result, the ASIC 124 can initialize only the K-color LD channel of the digital LDD 126.

[0117] If the ASIC 124 determines in step S200 that the output mode is the color mode, it may perform initialization for all channels in the same manner as in the first embodiment (step S200; No).

[0118] Furthermore, in the above-described process, initialization of the K-color LD channel is described, but the initialization is not limited to the K-color LD channel, and ASIC 124 may also initialize a specific channel based on the status of image forming device 10, the settings of image forming device 10, etc.

[0119] In this way, the optical scanning device of this embodiment can execute an APC sequence (a specific APC sequence) for each channel. Therefore, for example, when the image forming apparatus is a color machine and executes monochrome mode, the optical scanning device of this embodiment can initialize only the K-color LD channel and not initialize the LD channels of other colors (C-color, M-color, Y-color).

[0120] Typically, during initialization, an initial APC sequence is executed to initialize all channels, switching the digital LDD's operating mode to APC-H mode or APC-L mode and emitting laser light. In this case, deterioration of the photoconductor due to exposure to the same location (sub-scanning side) on the photoconductor cannot be prevented, shortening the photoconductor's lifespan. On the other hand, rotating the photoconductor to prevent deterioration increases power consumption in monochrome mode. Therefore, in monochrome mode on color machines, initialization (initial APC sequence) must not be performed on channels other than the K-color LD channel. In other words, in the past, when initializing a digital LDD, the digital LDD was set to the master state, automatically executing the initial APC sequence to initialize all channels. Therefore, in color machines with multiple color laser diodes connected to one laser driver, it was not possible to initialize only the channel used to form an electrostatic latent image on the black (K) photoconductor, making it impossible to support monochrome mode.

[0121] To address this issue, the optical scanning device of this embodiment executes a specific APC sequence while keeping the digital LDD in the slave state, even during initialization, to initialize a specific channel. This allows multiple light-emitting units to be connected to a single laser driver, enabling laser light to be irradiated onto multiple different photosensitive drums. As a result, when initializing the digital LDD in monochrome mode on a color machine, only the K LD channel is initialized. In this case, the optical scanning device of this embodiment prevents the C, M, and Y LD channels from being simultaneously initialized when initializing the K LD channel, thereby preventing laser light from being exposed to the photosensitive drums corresponding to the C, M, and Y colors. This allows the optical scanning device of this embodiment to be configured to use multiple light-emitting units for a single laser driver to irradiate multiple different photosensitive drums with laser light, further reducing the board area and reducing costs.

[0122] 3. Third Embodiment Next, a third embodiment will be described. In the third embodiment, in addition to the processing described in the first embodiment, initialization of the laser scanning unit is performed.

[0123] In this embodiment, the control unit 100 initializes the laser scanning unit in parallel with the initialization of the digital LDD 126 of the optical scanning device. For example, the control unit 100 initializes the laser scanning unit by initiating rotation of the polygon mirror in advance so that the polygon mirror rotates steadily. In this way, the control unit 100 can shorten the warm-up time of the image forming apparatus 10 by realizing the initialization of the digital LDD 126 and the steady rotation of the polygon mirror.

[0124] As described above, according to this embodiment, the initialization of the laser scan unit is performed in parallel with the initialization of the digital LDD, thereby realizing a reduction in the warm-up time.

[0125] [4. Modifications] The present invention is not limited to the above-described embodiments, and various modifications are possible. In other words, embodiments obtained by combining technical means that are appropriately modified within the scope of the gist of the present invention are also included in the technical scope of the present invention.

[0126] Although the above-described embodiments are described separately for convenience of explanation, they may be combined within the scope of technical feasibility. For example, the second embodiment and the third embodiment may be combined. In this case, the channel corresponding to the K color can be properly initialized in monochrome mode of a color machine, and the polygon mirror can be initialized in parallel with the initialization.

[0127] In addition, the programs that run on each device in the embodiments are programs that control the CPU, etc. (programs that make a computer function) so as to realize the functions of the above-described embodiments. Information handled by these devices is temporarily stored in a temporary storage device (e.g., RAM) during processing, and then stored in various storage devices such as ROMs (Read Only Memories) and HDDs, and is read, modified, and written by the CPU as needed.

[0128] Here, the recording medium for storing the program may be any of semiconductor media (e.g., ROM, non-volatile memory card, etc.), optical recording media / magneto-optical recording media (e.g., DVD (Digital Versatile Disc), MO (Magneto Optical Disc), MD (Mini Disc), CD (Compact Disc), BD (Blu-ray (registered trademark) Disc), etc.), magnetic recording media (e.g., magnetic tape, flexible disk, etc.), etc. Furthermore, not only are the functions of the above-described embodiments realized by executing the loaded program, but the functions of the present invention may also be realized by processing in cooperation with an operating system or other application programs, etc., based on instructions from the program.

[0129] Furthermore, when distributing the program on the market, the program can be stored on a portable recording medium and distributed, or transferred to a server computer connected via a network such as the Internet. In this case, the storage device of the server computer is of course included in the present invention. [Explanation of symbols]

[0130] 10 Image forming device 100 control section 102 Image processing section 110 Image input unit 120 Image forming unit 122 PCU 124 ASIC 126 Digital LDD 1261 Operation mode setting section 1262 Function setting section 1263 Light intensity correction unit 1264 APC control unit 1265 PD detector 128 EEPROM 130 Light-emitting part 132 Light receiving part 134 Image carrier 136 Fixing section 140 Display section 150 Operation section 160 Storage section 170 Communications Department

Claims

1. a light emitting unit that emits laser light; a driving unit that operates in either a master state in which the memory device is read and initialized in response to an input signal, or a slave state in which the light-emitting unit is driven in accordance with an operation mode corresponding to the input signal, and that has a plurality of channels that provide a driving current to the light-emitting unit to emit the laser light; a signal output unit that outputs the signal to the drive unit; Equipped with the signal output unit, when the drive unit is in the slave state, performs initialization by alternately outputting to the drive unit a signal corresponding to a first operation mode in which the light emitting unit is driven with a first light amount and a signal corresponding to a second operation mode in which the light emitting unit is driven with a second light amount smaller than the first light amount, and is capable of switching between the first operation mode and the second operation mode for each channel; An optical scanning device characterized in that, when in a mode in which only a specific channel is operated, the signal output unit performs initialization by alternately outputting to the specific channel a signal to switch to the first operating mode and a signal to switch to the second operating mode, and does not initialize channels other than the specific channel.

2. a light emitting unit that emits laser light; a driving unit that operates in either a master state in which the memory device is read and initialized in response to an input signal, or a slave state in which the light-emitting unit is driven in accordance with an operation mode corresponding to the input signal, and that has a plurality of channels that provide a driving current to the light-emitting unit to emit the laser light; a signal output unit that outputs the signal to the drive unit; an image bearing unit that bears an electrostatic latent image formed by irradiation with the laser light; a fixing unit that fixes an image based on the electrostatic latent image onto a recording sheet; Equipped with the signal output unit, when the drive unit is in the slave state, performs initialization by alternately outputting to the drive unit a signal corresponding to a first operation mode in which the light emitting unit is driven with a first light amount and a signal corresponding to a second operation mode in which the light emitting unit is driven with a second light amount smaller than the first light amount, and is capable of switching between the first operation mode and the second operation mode for each channel; An image forming apparatus characterized in that, when in a mode in which only a specific channel is operated, the signal output unit performs initialization by alternately outputting to the specific channel a signal to switch to the first operating mode and a signal to switch to the second operating mode, and does not initialize channels other than the specific channel.

3. An image forming device as described in Claim 2, characterized in that when the image output mode is monochrome mode, the channel corresponding to the color K is set as the specific channel, and initialization is performed by alternately outputting a signal to switch to the first operating mode and a signal to switch to the second operating mode to the specific channel, and initialization of channels other than the color K is not performed.

4. An image forming apparatus having a laser scanning unit, 3. The image forming apparatus according to claim 2, wherein the signal output section initializes the driving section and the laser scanning unit in parallel.

5. A control method for a drive device having a plurality of channels that operates in either a master state in which a memory device is read and initialized in response to an input signal, or a slave state in which a light emitting unit that emits laser light is driven in accordance with an operation mode corresponding to the signal, and that supplies a drive current to the light emitting unit to emit the laser light, comprising: an output step of outputting a signal for causing the driving device to enter the predetermined operation mode when the driving device is in a slave state during initialization of the driving device; an initialization step in which the driving device performs initialization based on the amount of laser light emitted from the light-emitting unit driven in accordance with the operation mode based on the output signal, In the output step, when the driving device is in a slave state, initialization is performed by alternately outputting to the driving device a signal corresponding to a first operation mode for driving the light emitting unit with a first light amount and a signal corresponding to a second operation mode for driving the light emitting unit with a second light amount smaller than the first light amount, and the first operation mode and the second operation mode can be switched for each channel, A control method characterized in that, in the initialization step, in a mode in which only a specific channel is operated, initialization is performed by alternately outputting to the specific channel a signal to switch to the first operating mode and a signal to switch to the second operating mode, and initialization of channels other than the specific channel is not performed.

Images