JP6769148B2 - Light source drive device, image forming device, light intensity control method - Google Patents

Description

The present invention relates to a light source driving device, an image forming device, and a light amount control method.

In an electrophotographic image forming apparatus, an exposure apparatus using a laser diode, an LED, or the like as a light source exposes a photoconductor drum based on image data to form a latent image. The developing roller supplies toner while rotating together with the photoconductor drum, and adheres the toner to the photoconductor drum by electrostatic force to create a toner image.

Since the light source used in such an electrophotographic image forming apparatus emits light by a driving current, it is preferable to form a rectangular light pulse whose waveform of the driving current corresponds to a pixel (called a dot or a pixel). .. However, the optical pulse does not follow the waveform of the drive current due to a delay in responsiveness represented by an oscillation delay of the light source. Therefore, the light pulse emitted so as to correspond to the pixel is not rectangular, and the amount of light emitted to the pixel is smaller than the target.

OV (overshoot) control and UD (undershoot) control are known as techniques for improving such a shortage of light amount (see, for example, Patent Document 1). Patent Document 1 uses a lighting pattern signal that shortens the time during which the supply of a predetermined current is stopped as compared with the lighting pattern signal used when setting the value of the first auxiliary drive current Iov. An optical drive circuit for setting a value of the drive current Iud is disclosed.

However, the conventional OV control and UD control have a problem that it is difficult to obtain the target amount of light at the time of high-speed lighting due to the high resolution and high speed of the image. For example, in the case of continuous dots, the amount of light of each dot may not be the target amount of light, which may affect the image quality.

An object of the present invention is to provide a light source driving device in which a light source forms a light pulse having an appropriate amount of light.

INDUSTRIAL APPLICABILITY The present invention is a light source driving device in which a first current value is added to the rising edge of a driving current for driving a light source, the driving current obtained by subtracting the second current value from the falling edge is output, and an optical pulse is emitted to the light source. The first current value determining means for outputting the driving current in the first lighting pattern and determining the first current value based on the integrated light amount of the optical pulse is provided. The current value determining means drives the light source with the driving current from which the second current value at which the fall time of the optical pulse is equal to or less than the threshold value is reduced , and the first current value determining means determines the current value. The drive current to which the first current value is added is output in a second lighting pattern having a shorter lighting interval than the first lighting pattern, and the second current value is based on the integrated light amount of the optical pulse. The first current value determining means determines the first current value by changing the lighting interval of the first lighting pattern, and the second current value determining means determines the current value. The current value determining means determines the second current value for each of the first current values, and the first current value and the first current value that are stable with respect to a change in the lighting interval of the first lighting pattern. Adopt the second current value .

It is possible to provide a light source driving device in which a light source forms a light pulse having an appropriate amount of light.

It is an example of the figure explaining the outline of the method of determining the OV value in this embodiment. It is an example of the figure explaining the outline of the method of determining the UD value in this embodiment. This is an example of a schematic configuration diagram of an image forming apparatus. It is an example of the figure explaining the formation of a toner image. This is an example of a schematic configuration diagram of an optical scanning device. This is an example of the hardware configuration diagram of the light source drive device. This is an example of a functional block diagram for explaining the function of the drive control circuit. It is an example of the figure which shows the light pulse and the integrated light amount. It is an example of the figure for demonstrating the effectiveness of the conventionally known OV control and UD control. It is an example of the figure explaining the drive current and the light pulse for continuous dots when the light amount of OV control and UD control is not appropriate. It is an example of the figure explaining the light pulse of the subsequent dot when the light amount of OV control and UD control is not appropriate. It is an example of the figure explaining the method of determining the OV value. It is an example of the figure explaining the method of determining the UD value. This is an example of a flowchart showing a procedure in which the drive control circuit determines the optimum OV value and the optimum UD value. It is an example of the flowchart which shows the procedure of the optimum OV adjustment. It is an example of the flowchart which shows the procedure of the optimum UD adjustment. This is an example of a flowchart showing a procedure in which the drive control circuit determines the optimum OV value and the optimum UD value (Example 2). It is an example of the figure explaining the determination of the set of the optimum OV value and the optimum UD value.

Hereinafter, the light source control device for carrying out the present invention and the light amount control method performed by the light source control device will be described with reference to the drawings.

<Outline of determination of OV value 1 and UD value 2>
The light source driving device of the present embodiment determines the optimum OV value and uses this optimum OV value to determine the optimum UD value.

FIG. 1 is an example of a diagram illustrating an outline of a method for determining an optimum OV value in the present embodiment. FIG. 1 shows a drive current 4. The light source driving device of the present embodiment lights the light source for each M dots with a driving current 4 set with an OV value 1 which is gradually increased in a state where a predetermined UD initial value 2I is set.

The predetermined UD initial value 2I is determined so that the falling time of the optical pulse is equal to or less than the threshold value. That is, the value is sufficiently large so that the fall of the optical pulse does not become dull. That is, the drive current 4 at which the rising time of the optical pulse does not become dull can be obtained. The driving current 4 because it has a spacing of M _OV-number fraction of a dot, even UD initial value 2I is sufficiently large, the UD initial value 2I has no influence on the rise of the optical pulses of the subsequent dot. In this state, the light source driving device determines the optimum OV value of 1 op as follows.
(1) The light source driving device measures the integrated light amount when the OV value 1 is zero (FIG. 1 (a)).
(2) The light source driving device measures the integrated light amount by increasing the OV value 1 by a predetermined amount (FIG. 1 (b)).
(3) The light source driving device measures the integrated light amount by increasing the OV value 1 by a predetermined amount (FIG. 1 (c)).
(4) The light source driving device measures the integrated light amount by increasing the OV value 1 by a predetermined amount (FIG. 1 (d)).

Hereinafter, when the light source driving device measures the integrated light amount by gradually increasing the OV value 1 while keeping the UD initial value 2I constant, the optimum OV value 1op at which the measured integrated light amount becomes equal to or more than the target integrated light amount is determined. Since the falling edge of the optical pulse is not blunted, it can be estimated that the rising edge of the optical pulse whose measured integrated light amount is about the same as the target integrated light amount is not blunted. Therefore, an optical pulse having a shape close to a rectangle can be obtained as one optical pulse. With the drive current 4 in which the optimum OV determined in this way is set, the amount of light of each dot of continuous dots can be brought close to the target amount of light.

Since the OV value 1 is optimized by this (since the optimum OV value is obtained), the UD value 2 is subsequently optimized.

FIG. 2 is an example of a diagram illustrating an outline of a method for determining the UD value 2 in the present embodiment. FIG. 2 shows the drive current 4. The light source driving device repeats the control of turning on the light source for each dot with the driving current 4 in which the UD value 2 which is gradually increased is set in the state where the optimum OV value 1 op is set.
(1) The light source driving device measures the integrated light amount when the UD value 2 is zero (FIG. 2A).
(2) The light source driving device measures the integrated light amount by increasing the UD value 2 by a predetermined amount (FIG. 2B).
(3) The light source driving device measures the integrated light amount by increasing the UD value 2 by a predetermined amount (FIG. 2 (c)).
(4) The light source driving device measures the integrated light amount by increasing the UD value 2 by a predetermined amount (FIG. 2 (d)).

Hereinafter, when the integrated light amount is measured by gradually increasing the UD value 2 while maintaining the optimum OV value of 1 op, the UD value 2 at which the measured integrated light amount is equal to or less than the target integrated light amount is determined. When the UD value 2 is small, the falling edge of the light pulse is smoothed, so that the off-lighting section and the subsequent dots include the excess light amount. However, by gradually increasing the UD value 2, the amount of surplus light decreases, and it is possible to determine the optimum UD value 2 op in which the amount of surplus light has almost no effect on the integrated light amount even if the light is turned on every other dot. That is, the drive current 4 with less rounding of the falling edge of the optical pulse can be obtained. Since the OV value 1 is optimized, the bluntness of the rising edge of the optical pulse is sufficiently small. Therefore, the drive current 4 makes it possible to bring the amount of light of the succeeding dots close to the target amount of light when the dot interval is short.

By obtaining the optimum OV value of 1 op and the optimum UD value of 2 op in this way, an optical pulse with a small roundness can be obtained at both the rising and falling edges of the optical pulse. Considering the case where the optimum UD value 2 op is obtained first, when the lights are lit at 1 dot intervals, the UD value affects the OV value of the subsequent dots and easily affects the rise of the optical pulse. The UD value 2op is easily affected by the OV initial value (provisionally set). Therefore, when, for example, 1by1 is lit at the optimum OV value 1op determined next, it may be necessary to determine the optimum UD value 2op again. In the present embodiment, the optimum UD value 2 op is obtained after the optimum OV value 1 op, so that each can be appropriately determined.

<Terminology>
An optical pulse is light whose intensity changes in a rectangular shape. The optical pulse may be formed repeatedly or sporadically. In addition, the same pattern may be repeated periodically.

A light source is an element having a function of outputting light. It may be called a light emitting element or the like. Specifically, it is a laser diode (semiconductor diode), an LED, or the like.

The lighting pattern is a lighting rule of a periodic optical pulse. For example, there are a pattern in which light pulses are continuously formed, a pattern in which every other light pulse is formed, a pattern in which every two light pulses are formed, ..., A pattern in which every n light pulses are formed, and the like. ..

<Configuration example>
FIG. 3 is an example of a schematic configuration diagram of the image forming apparatus. FIG. 3 is an example of a schematic configuration diagram of the image forming apparatus 2000. The image forming apparatus 2000 is a tandem multicolor printer that forms a full-color image by superimposing four colors (black K, cyan C, magenta M, and yellow Y). The image forming apparatus 2000 includes an optical scanning apparatus 2010 having a function as an exposure apparatus, four photoconductor drums (2030a, 2030b, 2030c, 2030d) that are sensitive to light, and four cleaning units (2031a, 2031b, 2031c, 2031d). It has four charging devices (2032a, 2032b, 2032c, 2032d), four developing rollers (2033a, 2033b, 2033c, 2033d), and four toner cartridges (2034a, 2034b, 2034c, 2034d).

Further, the image forming apparatus 2000 includes a transfer belt 2040, a transfer roller 2042, a fixing roller 2050, a paper feed roller 2054, a resist roller pair 2056, a paper discharge roller 2058, a paper feed tray 2060, a paper discharge tray 2070, a communication control device 2080, and a density. It has a detector 2245. Further, four home position sensors (2246a, 2246b, 2246c, 2246d) so as to detect the rotation of each photoconductor drum (2030a, 2030b, 2030c, 2030d), a printer control device 2090 that collectively controls each of the above parts, and the like. It has.

In the following, when the four photoconductor drums (2030a, 2030b, 2030c, 2030d) are not distinguished, they are collectively referred to as the photoconductor drum 2030. When the four charging devices (2032a, 2032b, 2032c, 2032d) are not distinguished, they are collectively referred to as the charging device 2032. When the four developing rollers (2033a, 2033b, 2033c, 2033d) are not distinguished, they are collectively referred to as the developing roller 2033.

The communication control device 2080 controls bidirectional communication with a higher-level device (for example, a PC: Personal Computer) via a network or the like. For example, a network card such as Ethernet (registered trademark).

The printer control device 2090 is an information processing device, a microcomputer, or the like, and is a CPU, a ROM in which a program described by a code decodable by the CPU and various data used when executing the program are stored, and a work. It has a RAM, which is a memory for use, an AD conversion circuit that converts analog data into digital data, and the like. The printer control device 2090 controls each unit in response to a print job execution request from the host device, and sends image data (image information) included in the print job to the optical scanning device 2010.

The photoconductor drum 2030a, the charging device 2032a, the developing roller 2033a, the toner cartridge 2034a, and the cleaning unit 2031a operate as a set of devices for forming a single color (for example, black K) image. Such a set of devices may be referred to as an image forming station, and a black image forming station may be hereinafter referred to as a "K station" for convenience.

Similarly, the photoconductor drum 2030b, the charging device 2032b, the developing roller 2033b, the toner cartridge 2034b, and the cleaning unit 2031b operate as a set of devices for, for example, forming an image of cyan C, and an image forming station that forms an image of cyan. In the following, may be referred to as "C station" for convenience.

The photoconductor drum 2030c, the charging device 2032c, the developing roller 2033c, the toner cartridge 2034c, and the cleaning unit 2031c operate as a set of devices for, for example, magenta M image formation, and the image forming station for forming the magenta M image is described below. Then, for convenience, it may be referred to as "M station".

The photoconductor drum 2030d, the charging device 2032d, the developing roller 2033d, the toner cartridge 2034d, and the cleaning unit 2031d operate as a set of devices for the yellow Y image forming device 2000, and the image forming station for forming the yellow image is described below. Then, for convenience, it may be referred to as "Y station". In the following, when the toner color is not limited, the image forming station is also simply referred to as a “station”.

A photosensitive layer is formed on the surface of each photoconductor drum 2030. That is, the surface of each photoconductor drum 2030 is the surface to be scanned. Each photoconductor drum 2030 is rotated in the arrow direction (clockwise direction) in the paper surface in FIG. 3 by a rotation mechanism.

In FIG. 3, in the three-dimensional Cartesian coordinate system of the X-axis, Y-axis, and Z-axis, the direction along the longitudinal direction of each photoconductor drum 2030 is along the Y-axis direction and along the arrangement direction of the four photoconductor drums 2030. This direction will be described as the X-axis direction.

Each charging device 2032 uniformly charges the surface of the corresponding photoconductor drum 2030. The optical scanning device 2010 is charged with a light beam modulated for each color based on multicolor image information (black image information, cyan image information, magenta image information, yellow image information) from a higher-level device. It emits light onto the surface of the photoconductor drum 2030. As a result, on the surface of each photoconductor drum 2030, the electric charge disappears only in the portion where the light is emitted, and a latent image corresponding to the image information is formed on the surface of each photoconductor drum 2030. The latent image formed here moves in the direction of the corresponding developing roller 2033 as the photoconductor drum 2030 rotates. A more detailed configuration of the optical scanning apparatus 2010 will be described later.

By the way, in each photoconductor drum 2030, the area in which the image information is written is called an "effective scanning area", an "image forming area", an "effective image area", or the like.

Black toner is stored in the toner cartridge 2034a, and the toner is supplied to the developing roller 2033a. Cyan toner is stored in the toner cartridge 2034b, and the toner is supplied to the developing roller 2033b. Magenta toner is stored in the toner cartridge 2034c, and the toner is supplied to the developing roller 2033c. Yellow toner is stored in the toner cartridge 2034d, and the toner is supplied to the developing roller 2033d.

As each developing roller 2033 rotates, toner from the corresponding toner cartridge is thinly and uniformly applied to its surface. Then, when the toner on the surface of each developing roller 2033 comes into contact with the surface of the corresponding photoconductor drum 2030, it migrates only to the portion of the surface where the light is emitted and adheres to the portion. That is, each developing roller 2033 attaches toner to the latent image formed on the surface of the corresponding photoconductor drum 2030 to visualize it. Here, the image (toner image) to which the toner is attached moves in the direction of the transfer belt 2040 as the photoconductor drum 2030 rotates.

The yellow Y, magenta M, cyan C, and black K toner images are sequentially transferred onto the transfer belt 2040 at predetermined timings and superposed to form a color image.

Recording paper is stored in the paper feed tray 2060. A paper feed roller 2054 is arranged in the vicinity of the paper feed tray 2060, and the paper feed roller 2054 takes out the recording paper one by one from the paper feed tray 2060 and conveys it to the registration roller pair 2056. The resist roller pair 2056 feeds the recording paper toward the gap between the transfer belt 2040 and the transfer roller 2042 at a predetermined timing. As a result, the color image on the transfer belt 2040 is transferred to the recording paper. The recording paper transferred here is sent to the fixing roller 2050.

In the fixing roller 2050, heat and pressure are applied to the recording paper, whereby the toner is fixed on the recording paper. The recording paper fixed here is sent to the output tray 2070 via the output roller 2058, and is sequentially stacked on the output tray 2070 that functions as a paper ejection unit.

Each cleaning unit removes the toner (residual toner) remaining on the surface of the corresponding photoconductor drum 2030. The surface of the photoconductor drum 2030 from which the residual toner has been removed returns to the position facing the corresponding charging device 2032.

The concentration detector 2245 is arranged on the −X side of the transfer belt 2040. The home position sensor 2246a detects the home position of rotation on the photoconductor drum 2030a. The home position sensor 2246b detects the home position of rotation on the photoconductor drum 2030b. The home position sensor 2246c detects the home position of rotation on the photoconductor drum 2030c. The home position sensor 2246d detects the home position of rotation on the photoconductor drum 2030d.

Four potential sensors (2247a, 2247b, 2247c, 2247d) are individually opposed to the four photoconductor drums 2030, and each potential sensor receives surface potential information of the opposing photoconductor drums 2030. Detect.

<Construction around the photoconductor drum>
FIG. 4 is an example of a diagram illustrating the formation of a toner image. A cleaning unit 2031, a charging device 2032, an optical scanning device 2010, a developing unit 2035, a transfer unit 2045, and a separating unit 2046 are arranged around the photoconductor drum 2030. In addition, the image forming apparatus sets an image processing unit that performs necessary image processing on print data, a data receiving unit that receives print data from a higher-level device (personal computer, scanner, etc.), various operation modes of a laser printer, and the like. It has operation keys to operate and an operation panel to display various information.

An electrostatic latent image is formed on the photoconductor drum by emitting a laser beam modulated by the optical scanning device 2010 to the photoconductor drum 2030 based on image data on the photoconductor drum uniformly charged by the charging device 2032. .. Next, the developing unit 2035 attaches toner to the photoconductor drum 2030 to form a toner image as a developing agent image. Next, the transfer unit 2045 transfers the toner image of the photoconductor drum to the recording medium (printing paper) 2047 that is fed from the paper feed unit through the paper feed path between the photoconductor drum and the transfer unit 2045. Next, the separation unit 2046 separates the recording medium 2047 on which the toner image is transferred from the photoconductor drum and conveys it to the fixing unit 2051.

The fixing unit 2051 includes a heating roller that is rotationally driven and heated to a predetermined fixing temperature, a pressure roller that comes into contact with the heating roller and rotates together with the heating roller, and a heating heater that heats the heating roller to a predetermined fixing temperature. I have. Then, the recording medium on which the toner image is transferred is conveyed while being heated and pressurized by the heating roller and the pressure roller, and the toner image is fixed on the recording medium to form an image.

Further, the cleaning unit 2031 removes static electricity from the photoconductor drum for which the transfer of the toner image has been completed to remove residual toner. After this, image formation by the charging device 2032 or the like is performed again.

FIG. 5 is an example of a schematic configuration diagram of the optical scanning apparatus 2010. The optical scanning device 2010 mainly includes a writing control unit 11, a light source driving device 12, a light source 13, a synchronization detection sensor 14, and a polygon mirror 15. Note that FIG. 5 shows the main elements of the present embodiment, and elements other than those shown in the drawings are omitted.

The write control unit 11 is realized by hardware such as ASIC and FPGA. The print data acquired from the host device is converted into raster data (bitmap data) by RIP (Raster Image Processor) processing. In addition, the image data read by a scanner or the like is raster data. Image area separation, color conversion, γ conversion, etc. are performed on these raster data, and further, by performing pseudo-halftone processing such as dither processing and error diffusion processing, 8-bit image data has pixels (1). , 0) is converted to screen data.

The write control unit 11 outputs a polygon control signal for controlling the rotation speed of the polygon mirror 15 to the polygon mirror 15. Further, the write control unit 11 outputs to the light source driving device 12 a DATA signal indicating a timing (pixel clock) corresponding to a pixel and a lighting control signal requesting lighting according to the timing when there is a pixel. To do.

The light source driving device 12 turns on or off the light source 13 according to the DATA signal and the lighting control signal from the writing control unit 11. The light source driving device 12 is realized by an information processing device such as an ASIC, an FPGA, or a microcomputer. The light source driving device 12 controls the lighting of the light source 13 one scan line in the main scanning direction based on the DATA signal and the lighting control signal. That is, the light source 13 is turned on when the lighting control signal is turned on, and the light source 13 is turned off when the lighting control signal is turned off.

When the light source 13 is, for example, LD21 (laser diode), the light source driving device 12 is an LD driver. That is, it has a circuit for generating a constant current, an auto power control circuit for keeping the optical output constant, a circuit for controlling lighting and extinguishing, and the like, and outputs a driving current 4 for driving the LD 21 to the light source 13. That is, the light source driving device 12 has a function of outputting a controlled pulse-shaped driving current 4.

Further, as will be described later, the light source driving device 12 adds a current corresponding to the OV value 1 to the pulsed driving current 4 and reduces the current corresponding to the UD value 2 to obtain a driving current in which a preferable optical pulse is obtained. Output 4 It also has a function of controlling to determine the optimum OV value 1 op and the UD value 2.

The light source 13 has an LD 21 and a PD 22 (Photo Detector). The LD 21 emits a laser beam 25 toward the polygon mirror 15 as a front beam, and also emits a back beam (laser beam) 26 toward the PD 22. This back beam 26 is used when determining the optimum OV value 1 op and the optimum UD value 2 op.

The laser beam 25 emitted toward the polygon mirror 15 is reflected by the polygon mirror 15 rotating at an angular velocity according to the resolution of the image forming apparatus, and is imaged on the photoconductor drum via the fθ lens, the reflection mirror, and the synchronous reflection mirror. .. The dashed arrow in the figure indicates the laser beam 25.

As the polygon mirror 15 rotates, the imaging position on the photoconductor drum moves in the direction of the arrow in the figure. The direction of the arrow is the direction of the generatrix of the cylinder, which is the shape of the photoconductor drum 2030, and is the main scanning direction of the image.

The laser beam 25 reflected by the polygon mirror 15 is also incident on the synchronous reflection mirror 27 arranged close to a position outside the image forming region on the scanning line of the photoconductor drum 2030. The synchronous reflection mirror 27 reflects the incident laser beam 25 to the synchronous detection sensor 14. The synchronization detection sensor 14 has, for example, a PD, and when the laser beam 25 is incident, it generates a synchronization detection signal which is a pulse output. In the illustrated configuration, the synchronous reflection mirror 27 is arranged on the scanning start side of the photoconductor drum 2030 on the scanning line. However, synchronous reflection mirrors may be arranged at both ends on the scanning line of the photoconductor drum 2030.

The photoconductor drum is scanned once on one surface of the polygon mirror 15, and this is detected by the synchronization detection signal. That is, the write control unit 11 is notified of the timing at which one scan in the main scan direction starts by the synchronization detection signal. The writing control unit 11 can set an effective scanning period, which is a period for writing an image on the photoconductor drum 2030 based on the synchronization detection signal. That is, the effective scanning period is set between the acquisition of the synchronization detection signal and the next acquisition of the synchronization detection signal, and the DATA signal and the lighting control signal are generated based on the image data.

The back beam 26 emitted from the LD 21 is incident on the PD 22 of the light source 13, and the PD 22 outputs a PD current (light amount feedback control signal described later) proportional to the strength of the back beam 26 to the light source driving device 12. As a result, the light source driving device 12 can perform feedback control of the amount of light.

The LD21 of the light source 13 in FIG. 5 may be called a semiconductor laser. Further, although the general LD21 is an end face emitting type laser, a surface emitting laser such as VCSEL (Vertical Cavity Surface Emitting LASER) may be used. Further, the light source 13 may be an LED. In this case, by arranging a plurality of LEDs corresponding to the resolution, scanning by the polygon mirror 15 can be eliminated. Further, a plurality of LD21s may be arranged for each light source 13 of each color. Each LD21 of such a light source 13 is referred to as a channel (CH).

Further, the configuration of FIG. 5 relates to monochromatic image data, and the color image forming apparatus performs the same scanning on each image data of CMYK.

FIG. 6 is an example of a hardware configuration diagram of the light source driving device 12. The light source driving device 12 includes a drive control circuit 31, four DACs (Digital Analog Converters) 32, an adder 34, a subtractor 35, and one ADC (Analog Digital Converter) 33.

The drive control circuit 31 outputs a drive current 4 for obtaining a rectangular optical pulse. Further, the drive control circuit 31 acquires the PD current detected by the PD 22 as a light amount feedback control signal, and determines the optimum OV value 1 op and the optimum UD value 2 op.

The drive control circuit 31 receives the DATA signal and the lighting control signal from the write control unit 11 and controls the drive current 4 for lighting the LD 21. The lighting timing is controlled by the DATA signal, and a predetermined UD control signal, OV control signal, bias control signal, and light amount control signal are output by the lighting control signal.

For example, when the lighting control signal means lighting, the UD control signal, the OV control signal, the bias control signal, and the light amount control signal are output. If the lighting control signal does not mean lighting, only the bias control signal is output.

The light amount control signal is a signal for outputting a reference current when the LD21 is lit. That is, it is a signal for outputting a current in a state where neither OV control nor UD control is performed. This is a signal corresponding to the current on the upper side of the pulsed drive current 4.

The bias control signal is a signal for constantly outputting a constant current to the LD 21 of the light source 13. It is a signal corresponding to the current at the bottom of the pulsed drive current 4. The current flowing by the bias control signal is a current for improving the light emission responsiveness of the LD21. The LD21 does not emit light unless a current equal to or higher than the threshold value flows, but by constantly flowing a current slightly smaller than the threshold value, the time until the LD21 emits light can be shortened as compared with a current flowing from zero to exceeding the threshold value.

The OV control signal is a signal corresponding to the OV value 1 at the rising edge of the drive current 4, and the UD control current is a signal corresponding to the UD value 2 at the rising edge of the drive current 4. Therefore, in the present embodiment, the optimum OV control signal and UD control signal are determined. The OV control signal is output for a shorter time than the light amount control signal when the drive current rises. For example, it is 1/2, 1/3, 1/4, 1/5 of the light amount control signal. The UD control signal is output for a shorter time than the light amount control signal when the drive current falls. For example, it is 1/2, 1/3, 1/4, 1/5 of the light amount control signal. The OV control signal and the UD control signal do not have to be the same.

The UD control signal, the OV control signal, the bias control signal, and the light amount control signal are input to the DAC 32 and converted from a digital value to an analog value. This analog value is the current value of the drive current 4. That is, the UD control signal is converted into a UD current, the OV control signal is converted into an OV current, the bias control signal is converted into a bias current, and the light amount control signal is converted into an LD21 current. The reference LD21 current and bias current are added to each other by the adder 34 to form a pulsed drive current 4. Further, when the OV current is applied by the adder 34, an OV-controlled drive current 4 is formed. The UD current is subtracted by the subtractor 35 to form the UD controlled drive current 4.

Then, as described with reference to FIG. 5, a part of the laser beam emitted from the LD 21 lit by the drive current 4 is incident on the PD 22, and the PD 22 outputs the PD current to the light source drive device 12. The light source driving device 12 converts the input PD current from an analog value to a digital value by the ADC 33. This digital value is input to the drive control circuit 31 as a light amount feedback control signal.

The drive control circuit 31 determines the optimum OV value 1 op and the optimum UD value 2 op using the light amount feedback control signal.

In FIG. 6, one example is shown in which the LD21 of the light source 13 is one, but when there are a plurality of LD21s, there are as many light amount control signals, bias control signals, OV control signals, and UD control signals as there are LD21s.

FIG. 7 is an example of a functional block diagram illustrating the function of the drive control circuit 31. The drive control circuit 31 has an OV value determination unit 40 and a UD value determination unit 50. The OV value determination unit 40 includes a current control unit 41, an integrated light amount calculation unit 42, a comparison unit 53, and an optimum OV value determination unit 44. Each of these functions is realized by each circuit included in the drive control circuit 31. Alternatively, it is realized by the CPU executing the program and cooperating with the hardware resources of the drive control circuit 31. Further, the OV value determining unit 40 has a storage unit 49 in which the UD initial value 2I and the target integrated light amount 46 are stored. The storage unit 49 is realized by a storage device such as a RAM or a flash memory of the drive control circuit 31.

The current control unit 41 gradually increases the OV current and outputs the drive current 4 to the light source 13 in order to determine the optimum OV value 1 op using the UD initial value 2I. The bias control signal and the light intensity control signal may be constant.

The integrated light amount calculation unit 42 acquires the light amount feedback control signal and calculates the integrated light amount. The integrated light amount is an integrated value of the light amount per unit time. For example, the amount of light is integrated with the time during which the drive current 4 for 10 dots of the image data is formed as a unit time.

The comparison unit 43 compares the integrated light amount calculated by the integrated light amount calculation unit 42 with the target integrated light amount, and feeds back the comparison result to the current control unit 41 and the optimum OV value determining unit 44. Since the OV value 1 gradually increases, the integrated light amount also gradually increases. Therefore, in the case of "integrated light amount <target integrated light amount", the current control unit 41 increases the OV value 1 and outputs the drive current 4. The current control unit 41 ends the output of the drive current 4 when “integrated light amount ≥ target integrated light amount”.

When the comparison unit 43 notifies the optimum OV value determination unit 44 that “integrated light amount ≥ target integrated light amount”, the optimum OV value determining unit 44 acquires the OV value 1 at that time from the current control unit 41. The acquired OV value 1 is the optimum OV value 1 op. The optimum OV value determination unit 44 stores the optimum OV value 1 op in the storage unit 59 of the UD value determination unit 50.

The UD value determination unit 50 includes a current control unit 51, an integrated light amount calculation unit 52, a comparison unit 53, and an optimum UD value determination unit 54. Each of these functions is realized by each circuit included in the drive control circuit 31. Alternatively, it is realized by the CPU executing the program and cooperating with the hardware resources of the drive control circuit 31. Further, the UD value determining unit 50 has a storage unit 59 in which the optimum OV value 1 op and the target integrated light amount 46 are stored. The storage unit 59 is realized by a storage device such as a RAM or a flash memory of the drive control circuit 31.

The current control unit 51 outputs the drive current 4 to the light source 13 by gradually increasing the UD current in order to determine the optimum UD current using the optimum OV value 1 op. The bias control signal and the light intensity control signal may be constant. The integrated light quantity calculation unit 52 is the same as the OV value determination unit 40.

The comparison unit 53 compares the integrated light amount calculated by the integrated light amount calculation unit 52 with the target integrated light amount, and feeds back the comparison result to the current control unit 51 and the optimum UD value determination unit. Since the UD value 2 gradually increases, the integrated light amount also gradually decreases. Therefore, in the case of "integrated light amount> target integrated light amount", the current control unit 51 increases the UD value 2 and outputs the drive current 4. The current control unit 51 ends the output of the drive current 4 when "integrated light amount ≤ target integrated light amount".

When the comparison unit 53 notifies that the optimum UD value determination unit 54 is “integrated light amount ≦ target integrated light amount”, the optimum UD value determining unit 54 acquires the UD value 2 at that time from the current control unit 51. The acquired UD value 2 is the optimum UD value 2 op. The optimum UD value determination unit 54 stores the optimum UD value 2 op in the storage unit 59 of the UD value determination unit 50.

When the optimum OV value 1 op and the optimum UD value 2 op are determined in this way, the drive control circuit 31 can output the drive current 4 to the light source 13 using the optimum OV value 1 op and the optimum UD value 2 op.

<About integrated light intensity>
The drive control circuit 31 uses the integrated light amount obtained by integrating the light amount feedback control signal in a unit time as the magnitude of the light pulse emitted by the LD21 of the light source 13. This integrated light quantity will be described.

FIG. 8 is an example of a diagram showing the light pulse 3 and the integrated light amount. In FIG. 8A, the LD21 is repeatedly lit at 1-dot intervals. Such lighting is called "1by1" lighting. 1by1 refers to a lighting pattern in which there is one dot between lighting. The integrated light amount is calculated by calculating the light amount of the light pulse 3 that repeats periodic lighting in this way as an integrated value per unit time.

Assuming that the integrated light amount per unit time when the light is always lit is 1, in FIG. 8A, the LD21 repeats turning on and off at 1-dot intervals, so that the integrated light amount per unit time is halved. However, this integrated light amount is the case of an ideal light pulse 3 in which the light pulse 3 has a rectangular shape. In other words, there is a possibility that the ideal light pulse 3 is obtained when the integrated light amount is halved when the light is turned on at 1by1. It is difficult for the drive control circuit 31 to temporally sample the light intensity to reproduce the 1-dot light pulse 3, but by measuring the integrated light amount, it is determined whether or not the light amount per dot is appropriate. it can.

FIG. 8B is a diagram showing an optical pulse 3 of a lighting pattern of 1by3 in which the LD21 repeatedly lights at intervals of 3 dots. When the light pulse 3 is an ideal square wave, the integrated light amount is 1/4. FIG. 8C is a diagram showing an optical pulse 3 of a lighting pattern of 1by9 in which the LD21 repeatedly lights at 9-dot intervals. When the light pulse 3 is an ideal square wave, the integrated light amount is 1/10. As described above, the target integrated light intensity differs depending on the M value of the lighting pattern of 1 by M.

The drive control circuit 31 lights the LD21 at 1 byM (an integer of M: 1 or more) and acquires a light amount feedback control signal. Then, the optimum OV value 1 op and the optimum UD value 2 op are determined so that the target integrated light amount of 1 byM can be obtained.

In the present embodiment, the lighting pattern in determining the optimum OV value 1op (1byM _OV), in the lighting pattern in determining the optimum UD value 2op (1byM _UD), the M OV _{<M UD.} As a result, the optimum OV value 1 op can be determined in a state where the rising edge of the optical pulse is not easily affected by the UD initial value 2I. In addition, the optimum UD value 2 op can be determined so that the falling edge of the optical pulse of the succeeding dot is not blunted.

<About OV value 1 and UD value 2>
The effectiveness of OV control and UD control, which are prerequisites, will be described with reference to FIG. That is, FIG. 9 is an example of a diagram for explaining the effectiveness of conventionally known OV control and UD control. FIG. 9A shows a drive current 4 in which OV control and UD control are not performed, and FIG. 9B shows an optical pulse 3 when the light source 13 is driven by the drive current 4 in FIG. 9A. Shown.

As shown in FIG. 9B, even when a pulsed drive current 4 is applied as a characteristic of the LD 21, the optical pulse 3 does not become a square wave due to the influence of a responsive delay such as an oscillation delay of the LD 21. That is, there is a delay until the rising edge becomes dull and reaches the maximum value. Furthermore, there is a delay until the amount of light becomes zero due to the slow rise. The dullness of the fall in the optical pulse 3 is caused by the time required for the potential of the light source 13 to transition from the potential in the lit state of the light source 13 to the potential in the extinguished state.

Therefore, there is known a technique of shaping the drive current 4 by OV control and UD control so that an optical pulse 3 close to a square wave can be obtained. FIG. 9C shows a drive current 4 in which OV control and UD control are performed, and FIG. 9D shows an optical pulse 3 when the light source 13 is driven by the drive current 4 in FIG. 9C. .. The OV control means that an overshoot is provided when the drive current 4 rises, and a current larger than the light quantity control current is output. Further, the UD control means that an undershoot is provided when the drive current 4 falls and a current smaller than the bias control current is output.

As shown in FIG. 9D, it can be seen that the OV control improves the bluntness of the rising edge of the optical pulse 3 and the UD control improves the blunting of the falling edge of the optical pulse 3.

When the LD21 is lit, heat is generated and the temperature changes, so that the amount of light fluctuates even with the same drive current 4. Therefore, the drive control circuit 31 is controlled by auto power control control so that the amount of light at the time of lighting becomes constant.

In this way, the light pulse 3 can be brought closer to a square wave by OV control and UD control, but the amount of light of continuous dots or subsequent dots when the interval between dots is short may not be the target amount of light as described below. It was. This will be described below.

<Light pulse at continuous dots>
FIG. 10 is an example of a diagram illustrating a drive current 4 and an optical pulse 3 for continuous dots when the light amounts of OV control and UD control are not appropriate. The drive control circuit 31 calculates the integrated light amount from the light amount feedback control signal when the LD21 is driven by the drive current 4. Further, the OV value 1 and the UD value 2 can be determined so that the integrated light amount equivalent to the target integrated light amount can be obtained. Therefore, as shown in FIG. 10A, the integrated light amount of one isolated dot can be appropriately determined.

However, since the drive control circuit 31 determines based on the integrated light amount, there is a possibility that the rising edge and the falling edge will be smoothed even if the integrated light amount is appropriate for one dot. This is because it cannot be determined whether or not the shape of the optical pulse 3 is appropriate because the determination is made based on the integrated light amount.

Note that the optical pulse 3 in FIG. 10A is an example in which the OV value 1 and the UD value 2 are smaller than the ideal values. Since the target integrated light amount is obtained in a state where the rising edge is blunt and the falling edge is blunted, the surplus light amount 201 is generated at the falling portion of the optical pulse 3.

FIG. 10B shows an optical pulse 3 when continuous dots are formed by the drive current 4 of FIG. 10A. As shown in FIG. 10B, neither dot 1 nor dot 2 of continuous dots can obtain an appropriate amount of light. First, at dot 1, the surplus light amount 201 is emitted to dot 2, so that the integrated light amount becomes insufficient. Further, at the dot 2, the surplus light amount 201 that should have been emitted to the dot 1 and the surplus light amount 201 that is emitted to the dot 2 are emitted, so that the integrated light amount becomes excessive.

In this way, if there is a bluntness in the light pulse 3 at the time of falling, the integrated light amount will differ between the isolated dot and the continuous dot. Since there is a difference in the integrated light amount per unit area between the isolated dots and the continuous dots, there is a possibility that uneven density may occur.

Therefore, even if the integrated light amount of one dot is appropriate, in the case of continuous dots, the target light amount of each dot may not be obtained.

<Light intensity of subsequent dots when the distance between dots is short>
Next, the optical pulse 3 when the OV value 1 is increased to reduce the rising bluntness and the UD value 2 is increased to reduce the falling bluntness will be described. In this case, the succeeding dot is affected by the UD control of the previous dot, and a bluntness occurs at the rising edge.

FIG. 11 is an example of a diagram for explaining the light pulse 3 of the succeeding dot when the light amount of the OV control and the UD control is not appropriate. Since the OV value 1 is set to reduce the rising bluntness and the UD value 2 is set to reduce the falling bluntness, the optical pulse 3 of the dot 1 has a rectangular shape. However, when the dot spacing is close at high speed lighting (1by1 in the figure), the subsequent dots, dots 2 and 3, are affected by the UD control of the dot 1, and the rising edge becomes blunt.

Therefore, for example, even if the OV value 1 and the UD value 2 in which the integrated light amount is the target integrated light amount are determined in a pattern with a wide interval such as 1by9, the quality of the optical pulse 3 deteriorates at high speed lighting with a short dot interval. May occur. If the quality of the light pulse 3 is poor, there is a possibility that uneven density may occur due to the unevenness of dots and the difference in the integrated light amount per unit area.

<Determination of OV value 1 and UD value 2 of this embodiment>
Conventionally, it has been known that it is effective to set the OV value 1 and the UD value 2, but the method for determining the appropriate OV value 1 and the UD value 2 has not been known. The present embodiment provides a determination method for appropriately determining the OV value 1 and the UD value 2 as follows.

FIG. 12 is an example of a diagram illustrating a method for determining the optimum OV value of 1 op. The current control unit 41 of the OV value determination unit 40 outputs the drive current 4 to the light source 13 while gradually increasing the OV value 1 using the UD initial value 2I. The UD initial value 2I is a UD value 2 in which the falling time of the optical pulse 3 is equal to or less than the threshold value. The fall time is, for example, the time from the peak to 1 / n (natural number) of the light intensity value. The UD initial value 2I can be experimentally determined by the person in charge of the image forming apparatus or the like. Further, the UD initial value 2I can take the value of the bias control current at the maximum, but may be the same as the bias control current.

The lighting pattern is 1 by M _OV . Here, the _MOV is preferably at least 2 or more (2 dots or more). Higher M _OV larger UD initial value 2I is possible to reduce the influence of the rise of optical pulses 3 subsequent dot. _{Therefore, M OV} may be to some extent large. For example, the person in charge or the like determines that the rise time of the optical pulse 3 is equal to or less than the threshold value under the UD initial value 2I. The rise time is the time from when the signal reaches 10% of the peak value to when it reaches 90%. Even with a large UD value 2 such that the shape of the falling light pulse 3 is rectangular, there is almost no possibility that the UD value 2 will affect the light pulse of the subsequent dots because the dot spacing is large. Therefore, an appropriate optimum OV value of 1 op can be determined.

12 (a) shows the light pulse 3 when the OV value 1 is zero, and FIGS. 12 (b) to 12 (d) show the light pulse 3 when the OV value 1 is gradually increased. In any case, the UD value 2 is the UD initial value 2I. It can be seen that as the OV value 1 increases, the bluntness of the rising edge of the optical pulse 3 decreases. For example, at the OV value 1 in FIG. 12 (d), the optical pulse 3 has a rectangular shape.

When the integrated light amount calculation unit 42 calculates the integrated light amount in each of FIGS. 12 (a) to 12 (d), the bluntness of the rising edge becomes small, so that the integrated light amount also gradually increases. Further, since the bluntness of the falling edge is sufficiently small, the integrated light amount should be about the same as the target integrated light amount when the light pulse 3 becomes rectangular as shown in FIG. 12D. Therefore, the drive control circuit 31 can determine the optimum OV value 1 op by gradually increasing the OV value 1 and comparing the integrated light amount with the target integrated light amount.

Since the drive current 4 having the optimum OV value of 1 op determined in this way has a rectangular wave, the amount of light of each dot of the continuous dots becomes the target amount of light, and the influence on the image quality can be reduced.

FIG. 13 is an example of a diagram illustrating a method of determining the optimum UD value 2 op. The current control unit 51 of the UD value determination unit 50 outputs the drive current 4 to the light source 13 while gradually increasing the UD value 2 using the optimum OV value 1 op. Lighting pattern is a 1byM _UD, in this embodiment the _{M UD} = 1. That is, the UD value 2 at which the integrated light amount becomes the target integrated light amount in high-speed lighting with a small dot interval is determined. When the UD value 2 is small, the fall of the optical pulse is smooth, but since the UD value 2 is small, there is no possibility that the integrated light amount of the subsequent dots will be smaller than the target integrated light amount. The light intensity value at the rising edge of the subsequent dots may increase and the integrated light intensity may become larger than the target integrated light intensity. However, as the UD value 2 gradually increases, the effect of increasing the rising edge of the light pulse 3 of the succeeding dots disappears. It should be _noted that M _UD = 2 or more may be used, but M _UD <M _ov .

13 (a) shows the light pulse 3 when the UD value 2 is zero, and FIGS. 13 (b) to 13 (d) show the light pulse 3 when the UD value 2 is gradually increased. In any case, the OV value 1 is the optimum OV value 1 op. It can be seen that as the UD value 2 increases, the dullness of the falling edge of the optical pulse 3 decreases. For example, at the UD value 2 in FIG. 13 (d), the optical pulse 3 has a rectangular shape. That is, the maximum UD value 2 can be determined without the UD value 2 reducing the rise of the light pulse 3 of the subsequent dots.

When the integrated light amount calculation unit 52 calculates the integrated light amount in each of FIGS. 13 (a) to 13 (d), the bluntness of the falling edge becomes small, so that the integrated light amount also gradually decreases. Further, since the OV value 1 is optimum, there is almost no blunting at the rising edge, and the integrated light amount should be about the same as the target integrated light amount when the light pulse 3 becomes rectangular as shown in FIG. 13D. Therefore, the drive control circuit 31 can determine the optimum UD value 2 op by gradually increasing the UD value 2 and comparing the integrated light amount with the target integrated light amount.

The optimum UD value 2op is determined so that the falling edge of the light pulse and the rising edge of the light pulse 3 of the succeeding dot do not become dull when the lighting interval is short, so aim for the amount of light of each dot of the succeeding dot with high-speed lighting. Easy to control the amount of light.

As described above, the drive control circuit 31 of the present embodiment can determine the optimum OV value 1 op by gradually increasing the OV value 1 with a sufficiently large UD value 2. Further, the optimum UD value 2 op can be determined by gradually increasing the UD value 2 in the lighting pattern of 1 by 1 using the optimum OV value 1 op.

<Operation procedure>
FIG. 14 is an example of a flowchart showing a procedure in which the drive control circuit 31 determines the optimum OV value 1 op and the optimum UD value 2 op. The process of FIG. 14 is executed, for example, before one job is executed. However, when the image-forming engine is adjusted, it is executed following the adjustment of the image-forming engine. The adjustment of the image forming engine is a control in which a pattern for adjusting the image forming conditions is generated on the transfer belt 2040, the pattern is read by a potential sensor, a density sensor, or the like, and feedback is given to the image forming engine. By this control, the density of the toner image is appropriately adjusted. Since the state of the image formation engine changes, the amount of light is corrected according to the adjusted state.
First, the drive control circuit 31 sets the lighting channel (CH) (S101). The lighting channel corresponds to each LD21 when the light source 13 is a multi-beam having a plurality of LD21s. As the number of LD21s increases, the scanning time of the photoconductor drum can be reduced.

Next, the OV value determining unit 40 adjusts the optimum OV (S102). Details will be described with reference to FIG. The OV value determination unit 40 adjusts the optimum OV until the determination of the optimum OV value 1 op for all channels is completed (S103).

Next, in order to perform the optimum UD adjustment, the drive control circuit 31 sets the lighting channel (S104).

Next, the UD value determining unit 50 performs the optimum UD adjustment (S105). Details will be described with reference to FIG. The UD value determination unit 50 performs the optimum UD adjustment until the determination of the optimum UD value 2op for all channels is completed (S106).

<< Optimal OV adjustment >>
FIG. 15 is an example of a flowchart showing a procedure for optimum OV adjustment. First, the current control unit 41 reads the UD initial value 2I from the storage unit 49 and sets the UD initial value 2I as the UD control signal (S201). It is assumed that the bias current signal and the light amount control signal are predetermined.

Next, the current control unit 41 lights up in a periodic lighting pattern of 1 byM _ov (S202). The initial OV value of 1 is zero.

The integrated light amount calculation unit 42 integrates the light amount feedback control signal to calculate the integrated light amount (S203).

The comparison unit 43 determines whether or not the integrated light amount exceeds the target integrated light amount (S204). As a result, it is possible to determine the OV value 1 that reduces the roundness of the rising edge.

When the determination in step S204 is No (No in S204), the current control unit 41 increases the OV control signal by a predetermined amount and turns on the LD21 (S205). Therefore, the OV value 1 can be gradually increased.

When the determination in step S204 is Yes (Yes in S204), it can be estimated that the optical pulse 3 has become a rectangular wave, so the optimum OV value determination unit 44 determines the current OV control signal to the optimum OV value 1 op (S206). ..

Thus, to set the UD initial value 2I in a sufficiently large value, by a sufficiently large dot spacing periodic lighting pattern of 1ByM _OV, the rectangular optical pulses 3 to determine the best OV value 1op can get.

<< Optimal UD adjustment >>
FIG. 16 is an example of a flowchart showing a procedure for optimum UD adjustment. First, the current control unit 51 acquires the optimum OV value 1 op from the optimum OV value determination unit 44 and sets it as an OV control signal (S301). It is assumed that the bias current signal and the light amount control signal are predetermined. In the case of the multi-beam LD21, the optimum OV value of 1 op determined for each LD21 is set.

Next, the current control unit 51 lights up in a periodic lighting pattern of 1by1 (S302). The initial UD value 2 is zero.

The integrated light amount calculation unit 52 integrates the light amount feedback control signal to calculate the integrated light amount (S303).

The comparison unit 53 determines whether or not the integrated light amount is equal to or less than the target integrated light amount (S304). As a result, it is possible to determine the UD value 2 in which the dullness of the falling edge is small.

When the determination in step S304 is No (No in S304), the current control unit 51 turns on the LD21 by increasing the UD control signal by a predetermined amount (S305). Therefore, the UD value 2 can be gradually increased.

When the determination in step S304 is Yes (Yes in S304), it can be estimated that the optical pulse 3 has become a rectangular wave, so the optimum UD value determination unit 54 determines the current UD control signal to the optimum UD value 2 op (S306). ..

By such control, it is possible to determine the maximum UD value 2 in which the UD value 2 hardly blunts the rising edge of the optical pulse 3 of the subsequent dots without making the UD value 2 excessive.

In the case of multi-beam, the optimum OV value 1 op and the optimum UD value 2 op may have set values for each channel or may be average values of all channels.

<Summary>
As described above, it is possible to determine the OV value 1 and the UD value 2 that can obtain the target integrated light amount even in the continuous dots of high-speed lighting and the subsequent dots.

In Example 1, _{M OV} was fixed in the lighting pattern in determining the optimum OV value 1op (1byM _OV). In this _embodiment, will be described a drive control circuit 31 can determine the optimum OV value 1op while changing the _{M OV.}

It is assumed that the hardware configuration diagram and the functional block diagram of the optical scanning apparatus 2010 are the same as those in the first embodiment.

FIG. 17 is an example of a flowchart showing a procedure in which the drive control circuit 31 determines the optimum OV value 1 op and the optimum UD value 2 op (Example 2). In the description of FIG. 17, the difference from FIG. 14 will be mainly described.

First, OV value determination unit 40 sets the _{M OV} (S100). The initial value of _MOV is 2. Rather than maintaining a constant M _OV in this embodiment, variably controls the M _OV.

Next, the drive control circuit 31 sets the lighting channel (CH) (S101).

Next, the OV value determining unit 40 adjusts the optimum OV (S102). The content of the optimum OV adjustment may be the same as that in the first embodiment. The OV value determination unit 40 adjusts the optimum OV until the determination of the optimum OV value 1 op for all channels is completed (S103). The processing of the transition steps S104 to S106 may be the same as that of the first embodiment.

Next, the UD value determination unit 50 increases the _MOV by one (S107).

_Then, until _{M OV} is greater than 10 for example (No in S108), the process returns to step S103, the optimum OV value 1op and optimum UD value 2op is determined.

If M _OV is greater than 10 (Yes in S108), UD value determination unit 50 determines a set of one optimal OV value 1op and optimum UD value 2op a plurality of sets of optimum OV value 1op and optimum UD value 2op (S109). Note that 10 is an example, and may be less than 10 or more than 10.

FIG. 18 is an example of a diagram illustrating the determination of the set of the optimum OV value 1 op and the optimum UD value 2 op. For example, as shown in FIG. 18, UD value determination unit 50 _calculates the inclination of the optimum OV value 1op and optimum UD value 2op for _{M OV.} UD value determination unit 50 to each of the slope of the optimum OV value 1op and optimum UD value 2OP, calculated in each _{M OV.} It can be estimated that the optimum OV value 1 op and the optimum UD value 2 op when the absolute value of the slope is less than the threshold value are stable. The UD value determining unit 50 determines to adopt the set of the first optimum OV value 1 op and the optimum UD value 2 op in which the slopes of the optimum OV value 1 op and the optimum UD value 2 op are both less than the threshold value. Figure 18 The _{M OV} = 5 in the optimal OV value 1op is _{stabilized, if M OV} = 4 at the optimum UD value 2op is stabilized, the optimum OV value determining unit 44 and the optimum UD value determining unit 54 of the _{M OV} = 5 best An OV value of 1 op and an optimum UD value of 2 op are adopted respectively.

Alternatively, the optimum OV value determining unit 44 may adopt the average of the optimum OV value 1 op after the slope of the optimum OV value 1 op becomes less than the threshold value. The optimum UD value determination unit 54 determines to adopt the average of the optimum UD value 2op after the slope of the optimum UD value 2op becomes less than the threshold value.

To determine the best OV value 1op leave determined in advance one _{M OV} In Example 1, it was then determined optimum UD value 2op in lighting pattern 1By1. However, _{M OV} when determining the optimum OV value 1op is not necessarily optimal. In this _embodiment, since the calculated optimum OV value 1op and optimum UD value 2OP by changing the _{M OV,} by estimating the appropriate Mov, you can determine the optimum OV value 1op and optimum UD value 2OP.

<Other application examples>
The best mode for carrying out the present invention has been described above with reference to Examples, but the present invention is not limited to these Examples, and various modifications are made without departing from the gist of the present invention. And substitutions can be made.

For example, the OV value was gradually increased in the determination of the optimum OV value of 1 op, but the integrated light amount was calculated from a plurality of OV values, and the OV value at which the integrated light amount closest to the target integrated light amount was obtained was determined to be the optimum OV value of 1 op. You may. The same applies to the determination of the optimum UD value 2op.
Further, in this embodiment, the optimum UD value 1 op is determined and then the optimum UD value 2 op is determined, but the optimum UD value 1 op may be determined after the optimum UD value 2 op. In this case, the optimum UD value 2op is determined by gradually increasing the UD value with respect to the appropriate initial value of OV, and the optimum OV value 1 is gradually increased by using this optimum UD value 2op. Determine 1 op.

Further, the optimum OV value 1 op and the optimum UD value 2 op may be determined by changing the output times of the OV control signal and the UD control signal. Further, after the optimum UD value 2 op is determined, the optimum OV value 1 op may be determined again.

Further, the configuration examples shown in FIG. 7 and the like are divided according to the main functions in order to facilitate understanding of the processing by the light source driving device. The present invention is not limited by the method or name of dividing the processing unit. Further, the processing of the light source driving device can be divided into more processing units according to the processing content. It is also possible to divide one processing unit so as to include more processing.

The lighting pattern when determining the optimum OV value 1op is an example of the first lighting pattern, and the lighting pattern when determining the optimum UD value 2op is an example of the second lighting pattern. The OV current or OV value is an example of the first current value, the UD current or UD value is an example of the second current value, and the OV value determining unit 40 is an example of the first current value determining means. The UD value determining unit 50 is an example of the second current value determining means.

11 Write control unit 12 Light source drive device 13 Light source 40 OV value determination unit 41 Current control unit 42 Integrated light intensity calculation unit 43 Comparison unit 44 Optimal OV value determination unit 46 Target integrated light intensity 50 UD value determination unit

JP-A-2014-229691

Claims (8)

A light source driving device that adds a first current value to the rising edge of a driving current that drives a light source, outputs the driving current obtained by subtracting the second current value from the falling edge, and emits an optical pulse to the light source.
It has a first current value determining means for outputting the driving current in the first lighting pattern and determining the first current value based on the integrated light amount of the optical pulse.
The first current value determining means drives the light source with the driving current from which the second current value at which the falling time of the optical pulse is equal to or less than the threshold value is reduced .
The drive current to which the first current value determined by the first current value determining means is added is output in a second lighting pattern having a shorter lighting interval than the first lighting pattern, and the optical pulse is generated. It has a second current value determining means for determining the second current value based on the integrated light amount of
The first current value determining means determines the first current value by changing the lighting interval of the first lighting pattern.
The second current value determining means determines the second current value for each of the first current values, respectively.
A light source driving device that employs the first current value and the second current value that are stable with respect to a change in the lighting interval of the first lighting pattern . The light source drive according to claim 1, wherein the first lighting pattern has a lighting interval such that the second current value at which the falling time of the light pulse is equal to or less than a threshold value does not affect the rising of the light pulse. apparatus. The first current value determining means outputs the driving current from which the second current value has been reduced in the first lighting pattern by changing the first current value, and is about the same as the target integrated light amount. The light source driving device according to claim 1 or 2, wherein the first current value from which the integrated light amount is obtained is determined. The second current value determining means changes the second current value of the drive current to which the first current value determined by the first current value determining means is added, and changes the second lighting. The light source driving device according to claim 1 , wherein the second current value is determined by outputting in a pattern and obtaining an integrated light amount equivalent to the target integrated light amount. The light source driving device according to any one of claims 1 to 4 , wherein the first lighting pattern is a lighting pattern having a lighting interval of 2 dots or more. The light source driving device according to any one of claims 1 to 5 , wherein the second lighting pattern is a lighting pattern having a lighting interval of 1 dot. A method for controlling the amount of light of a light source driving device in which a first current value is added to the rising edge of a driving current for driving a light source, the driving current is output by subtracting the second current value from the falling edge, and an optical pulse is emitted to the light source. And
A step in which the first current value determining means outputs the drive current in the first lighting pattern,
It has a step of determining the first current value based on the integrated light amount of the light pulse.
The first current value determining means drives the light source with the driving current from which the second current value at which the falling time of the optical pulse is equal to or less than the threshold value is reduced .
The second current value determining means transfers the drive current to which the first current value determined by the first current value determining means is added to a second driving current having a shorter lighting interval than the first lighting pattern. It has a step of outputting in a lighting pattern and determining the second current value based on the integrated light amount of the light pulse.
The first current value determining means determines the first current value by changing the lighting interval of the first lighting pattern.
The second current value determining means determines the second current value for each of the first current values, respectively.
A light amount control method that employs the first current value and the second current value that are stable with respect to a change in the lighting interval of the first lighting pattern . The light source driving device according to any one of claims 1 to 6 .
A developing unit that develops a latent image formed by the light source driving device with toner, and
An image forming apparatus having a paper feeding unit and a paper discharging unit.

Images