JP2022106520A - Optical scanner, image forming apparatus, control method, and program - Google Patents

Abstract

To provide an optical scanner that does not require time for processing according to a change in target light quantity, maintains its resolution when performing shading, and does not cause deviation of the target light quantity.SOLUTION: An optical scanner comprises: a laser emitting unit in which an excess current from a bias current increases and decreases in proportion to an input analog signal; a laser driver for driving a laser emitting unit; an optical scanning unit that scans a laser beam emitted from the laser emitting unit on an object; an offset value determination unit that, based on a target light quantity of the laser emitting unit, determines an offset value of the analog signal input to the laser emitting unit; and a laser driver control unit that superposes a signal of the determined offset value on the analog signal to offset the analog signal, and inputs the offset analog signal to the laser driver to control the quantity of light emitted from the laser emitting unit.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to an optical scanning device and the like.

In the image forming apparatus, a laser diode (laser diode () for an exposure process of forming an electrostatic latent image on the surface of a photoconductor drum in a process of forming an image based on an image signal on a recording sheet (sheet-shaped image recording medium). An optical scanning device that scans the photoconductor drum as an object to be scanned by the laser light emitted by the light emitting element) is mounted.

In general, a laser diode has a characteristic that an optical output rises at a threshold current as the input current is increased. Due to its characteristics, it was common to always pass a bias current in order to shorten the delay in the rise time of laser oscillation.

Regarding the bias current, in order to follow the change of the threshold current caused by the temperature change and the time measurement change without fixing the bias current, the auto bias circuit type light emitting element drive device that automatically adjusts the bias current according to the change of the threshold current. Is disclosed (see Patent Document 1).

On the other hand, there is a technique relating to a laser driver in which an excess current from a fixed bias current increases or decreases in proportion to an input analog signal without adopting an auto-bias circuit as in Patent Document 1.

Regarding the fixed bias current, Patent Document 2 discloses an optical scanning device that corrects the amount of emitted light of a light source by using an optical driving unit that does not have an auto-bias control function.

In Patent Document 2, the voltage value of the analog signal that controls the laser driver according to the target light amount is calculated after storing the light amount and current characteristics (PI characteristics) of the laser diode for each temperature. There was a challenge.

It was necessary to calculate the voltage value of the analog signal again according to the change in the target light amount such as the environment and the life (use time) correction, and the processing took time.

When shading was performed with a low target light intensity, the shading resolution was deteriorated.

When the PI characteristics and the amount of light at the root of the laser diode varied individually, the target amount of light was deviated.

Japanese Unexamined Patent Publication No. 2003-298178 JP-A-2018-69518

In view of such circumstances, the present disclosure provides an optical scanning device and the like that do not require time for processing according to a change in the target light amount, maintain resolution when shading is performed, and do not cause a deviation in the target light amount. It is something to try.

The present disclosure includes a laser emitting unit in which an excess current from a bias current increases or decreases in proportion to an input analog signal, a laser driver for driving the laser emitting unit, and a laser beam emitted from the laser emitting unit. An optical scanning unit that scans on an object, an offset value determining unit that determines the offset value of an analog signal input to the laser emitting unit based on the target light amount of the laser emitting unit, and a signal having the determined offset value. It is characterized by comprising a laser driver control unit that controls the amount of light emitted from the laser light emitting unit by superimposing it on the analog signal and offsetting it and inputting the offset analog signal to the laser driver. It is an optical scanning device.

Further, in the present disclosure, the optical scanning device, an image carrier in which an electrostatic latent image is formed on the surface by scanning the laser light emitted from the laser emitting unit by the optical scanning unit, and the image bearing. An image forming apparatus including a developing unit for developing an electrostatic latent image formed on the surface of a body.

Further, the present disclosure discloses a laser light emitting unit in which an excess current from a bias current increases or decreases in proportion to an input analog signal, a laser driver for driving the laser light emitting unit, and a laser emitted from the laser light emitting unit. It is a control method of an optical scanning device including an optical scanning unit that scans light on an object, and determines an offset value of an analog signal input to the laser emitting unit based on a target light amount of the laser emitting unit. The amount of light emitted from the laser emitting unit is controlled by the offset value determining step, the signal of the determined offset value is superimposed on the analog signal and offset, and the offset analog signal is input to the laser driver. It is a control method characterized by having a laser driver control process.

Further, the present disclosure discloses a laser emitting unit in which an excess current from a bias current increases or decreases in proportion to an input analog signal, a laser driver for driving the laser emitting unit, and a laser emitted from the laser emitting unit. An offset value determination in which a computer of an optical scanning device including an optical scanning unit that scans light onto an object determines an offset value of an analog signal input to the laser emitting unit based on a target light amount of the laser emitting unit. Laser driver control that controls the amount of light emitted by the laser emitting unit by superimposing the function and the signal of the determined offset value on the analog signal and offsetting it, and inputting the offset analog signal to the laser driver. It is a program that realizes functions.

According to the optical scanning apparatus and the like of the present disclosure, the signal of the determined offset value is superimposed on the analog signal and offset, and the offset analog signal is input to the laser driver to reduce the amount of light emitted from the laser emitting unit. Since it is controlled, it does not take time for processing according to a change in the target light amount, the resolution is maintained when shading is performed, and an excellent effect that the target light amount does not deviate can be obtained.

It is an external view of the image forming apparatus equipped with the optical scanning apparatus which concerns on embodiment. It is a control block diagram of an image forming apparatus and an optical scanning apparatus. It is a circuit diagram of the signal transmission path of a laser light emitting part of an optical scanning apparatus and a laser driver. It is explanatory drawing of the example of the offset adjustment table. It is explanatory drawing of the mechanical structure of an optical scanning part. It is a flowchart explaining the process flow of an optical scanning apparatus. In the explanation of the shading correction value signal, the offset value signal, etc., (a) is the detection signal of the BD sensor, (b) is the shading correction value signal, (c) is the offset value signal, and (d) is. It is each explanatory diagram of the input signal to a laser driver. It is a diagram which shows the example of the light-current characteristic of the laser light emitting element which changes with temperature for demonstrating the optical scanning apparatus in 2nd Embodiment. (A) to (c) show each example of the offset adjustment table for each temperature.

Hereinafter, an embodiment for carrying out the present disclosure will be described with reference to the drawings.

The following embodiments are examples for explaining the present disclosure, and the technical scope of the invention described in the claims is not limited to the following description.

[1. First Embodiment]
First, the configuration of the image forming apparatus 10 according to the first embodiment will be described.

[1.1 Overall configuration]
As shown in FIG. 1, the image forming apparatus 10 is an information processing apparatus provided with a document reading unit 112 above the image forming apparatus 10 to read an image of a document and output the image by an electrophotographic method. An example of the image forming apparatus 10 is a multifunction printer.

As shown in the control system diagram of FIG. 2, the image forming apparatus 10 mainly includes a control unit 100, an image input unit 110, a document reading unit 112, an image processing unit 120, an image forming unit 130, and an operation unit. It includes 140, a display unit 150, a storage unit 160, and a communication unit 170, and also has a function of an optical scanning device 200.

[1.2 Functional configuration]
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, and is composed of, for example, one or a plurality of arithmetic units (for example, a CPU (Central Processing Unit)).

The image input unit 110 is a functional unit for reading image data input to the image forming apparatus 10. Then, the image input unit 110 is connected to the document reading unit 112, which is a function unit for reading the image of the document, and inputs the image data output from the document reading unit 112.

Further, the image input unit 110 may input image data from a storage medium such as a USB memory or an SD card. Further, the image data may be input from the other terminal device by the communication unit 170 that connects to the other terminal device.

The document reading unit 112 has a function of optically reading the document placed on the contact glass (not shown) and passing the scan data to the image processing unit 120.

The image forming unit 130 is a functional unit for forming output data based on the image data on a recording medium (for example, recording paper). For example, as shown in FIG. 1, the recording paper is fed from the paper feed tray 122, and after the image is formed on the surface of the recording paper in the image forming unit 130, the paper is discharged from the paper ejection tray 124. The image forming unit 130 is composed of a laser printer using an electrophotographic process using an electrophotographic method.

In the electrophotographic process of the image forming unit 130, a laser beam (corresponding to laser light) corresponding to the image data is scanned on the surface of the photoconductor drum (image carrier) 130a (see FIG. 4) by the optical scanning device 200 described later. An electrostatic latent image is formed, the electrostatic latent image is developed with a toner, and the developed toner image is transferred and fixed on a recording medium to form an image.

The image processing unit 120 has a function of converting to a set file format (TIFF, GIF, JPEG, etc.) based on the image data read by the document reading unit 112. Then, an output image is formed based on the image data that has undergone image processing.

The operation unit 140 is a functional unit for receiving an operation instruction by a user, and is composed of various key switches, a device for detecting an input due to contact, and the like. The user inputs the function to be used and the output conditions via the operation unit 140.

The display unit 150 is a functional unit for displaying various information to the user, and is configured by, for example, an LCD (Liquid crystal display) or the like.

That is, the operation unit 140 provides a user interface for operating the image forming apparatus 10, and the display unit 150 displays various setting menu screens and messages of the image forming apparatus.

As shown in FIG. 1, the image forming apparatus 10 may include a touch panel in which the operation panel 141 and the display unit 150 are integrally formed as the configuration of the operation unit 140. In this case, the method for detecting the input of the touch panel may be a general detection method such as a resistance film method, an infrared ray method, an electromagnetic induction method, or a capacitance method.

The storage unit 160 is a functional unit that stores various programs including a control program necessary for the operation of the image forming apparatus 10, various data including read data, and user information. The storage unit 160 is composed of, for example, a non-volatile ROM (Read Only Memory), a RAM (Random Access Memory), an HDD (Hard Disk Drive), or the like. Further, an SSD (Solid State Drive) which is a semiconductor memory may be provided.

The communication unit 170 makes a communication connection with an external device. A communication interface (communication I / F) used for transmitting and receiving data is provided as the communication unit 170. By the communication I / F, the data stored in the storage unit of the image forming apparatus 10 can be transmitted / received to another computer device connected via the network by the operation by the user in the image forming apparatus 10. can.

[1.3 Optical scanning device 200]
As shown in FIG. 2, the image forming apparatus 10 is equipped with an optical scanning apparatus 200.

FIG. 3 shows a specific circuit diagram of a signal transmission path around the laser driver in the optical scanning device 200. FIG. 5 shows the mechanical configuration of the optical scanning device 200.

As shown in FIGS. 2 and 3, the optical scanning device 200 includes a laser light emitting unit (LD: Laser Device) 200a in which the excess current from the bias current increases or decreases in proportion to the input analog signal, and laser light emission. The laser driver 210 for driving the unit, the optical scanning unit 220 that scans the laser beam (laser light) emitted from the laser emitting unit 200a onto the photoconductor drum 130a of the object, and the light scanning on the object are shaded. Offset that determines the offset value of the analog signal input to the laser light emitting unit 200a based on the target light amount (Vref) of the shading correction signal unit 230 that outputs the shading correction value signal (Vshade) and the laser light emitting unit 200a. The value determination unit 240 and the determined offset value signal (Voffset) are superimposed on the analog signal (shading correction value signal (Vshade)) and offset, and the shading correction signal (Vsw) of the offset analog signal is applied. It includes a laser driver control unit 250 that controls the amount of light emitted from the laser light emitting unit (LD) 200a by inputting to the laser driver (LD Driver) 210.

The shading correction value (Vshade) output by the shading correction signal unit 230 is calculated in the adjustment step of the optical scanning device 200 and stored in the ROM or the like of the storage unit 160. The shading correction value is sequentially read from the storage unit 160 according to the irradiation position of the laser beam with respect to the surface of the photoconductor drum 130a in the main scanning direction.

As shown in FIG. 3, the shading correction value signal (Vshade) is connected via the path s1 via the resistor r1, and the offset value signal (Voffset) is connected via the path s2 via the resistor r2. An analog signal (Vsw) in a state in which the shading correction signal is offset by being superimposed in unit c1 is input to the laser driver 210. The connecting portion c1 is provided with a resistor r3 between the connecting portion c1 and the ground (G).

Further, the optical scanning device 200 has a light amount detecting unit 260 for detecting the light emitting amount of the laser light emitting unit 200a, and the laser driver control unit 250 measures the light emitting amount of the laser light emitting unit 200a detected by the light amount detecting unit 260. It is controlled so that the target amount of light is reached.

Specifically, the laser driver control unit 250 measures the light output (optical power) of the laser diode by, for example, a light amount detection unit 260 composed of a photo diode (PD: Photo Diode) built in the laser diode (laser light emitting unit 200a). It uses an APC (Automatic Power Control) control method that monitors and controls the drive current of the laser diode with a reference voltage signal (Vref) so that the light output reaches the target amount of light.

The offset value determining unit 240 determines the offset value (signal Voffset) based on the signal (reference voltage signal (Vref)) of the target light amount of the laser driver control unit 250 during APC control. The storage unit 160 stores the offset adjustment table 240a in which the relationship between the target light amount and the offset value is set, and the offset value determination unit 240 refers to the stored offset adjustment table 240a and is based on the target light amount. To determine the offset value.

In the embodiment, the offset adjustment table 240a as shown in FIG. 4 is stored in the ROM (: Read Only Memory) of the storage unit 160. In the offset adjustment table 240a shown in FIG. 4, the relationship between the target light amount signal (reference voltage signal (Vref)) and the offset value (signal Voffset) is set.

By temporarily storing in the storage unit 160 in the form of the offset adjustment table 240a, it is not necessary to recalculate the set value of the analog signal to the laser driver 210 according to the change in the target light amount such as the environment and life correction. , Does not take time to process.

Further, in order to cope with the change of the offset value (signal Voffset) according to the temperature, the storage unit 160 may store a plurality of offset adjustment tables 240a according to the temperature as shown in FIG. 9 described later. can.

FIG. 5 shows the mechanical configuration of the optical scanning unit 220 of the optical scanning device 200.

As shown in FIG. 5, the optical scanning unit 220 scans the laser beam onto the photoconductor drum 130a to form an electrostatic latent image on the photoconductor drum 130a.

As shown in FIG. 5, the optical scanning device 200 includes a laser emitting unit 200a that generates a laser beam (laser light), and an incident laser is emitted in the emission direction of the laser beam emitted from the laser emitting unit 200a. By combining a collimeter lens 200b that converts a beam into a parallel beam, an aperture 200c composed of a plate-shaped member having an opening 200c1 formed in a substantially central portion, and an fθ lens 200d that expands a laser beam described later in the scanning direction. A concave lens 200e that magnifies the incident laser beam, a cylindrical lens 200f, and an incident beam folding mirror 200g are sequentially arranged.

Further, in the direction of reflection of the laser beam by the incident beam folding mirror 200g, an fθ lens 200d and a polygon mirror 200h having a plurality of reflection surfaces on the outer peripheral surface are arranged in order, and the laser beam by the reflection surface of the polygon mirror 200h. In the reflection direction of the above, an fθ lens 200d, a reflection mirror 200i, an emission beam folding mirror 200j for correcting the surface tilt of the polygon mirror 200h, and a photoconductor drum 130a are arranged.

The reflected light reflected by the reflection mirror 220i is detected by the beam detect sensor (BD sensor) 200k. The BD sensor 200k is an optical sensor that outputs a detection signal according to the magnitude of the amount of light received by the laser beam. The BD sensor 200k has a function of detecting reflected light from the start end side of the main scanning region of the laser beam (scanning region along the axial direction of the photoconductor drum 130a), and displays an electrostatic latent image on the photoconductor drum 130a. It is used to control the writing timing.

Further, the laser light emitting unit 200a includes a light amount detecting unit 260 provided with a PD (photodiode) for detecting the laser emission amount in the vicinity.

[1.4 Processing flow]
FIG. 6 is a flowchart illustrating a processing flow of the optical scanning apparatus. Each step-is abbreviated as "S-". FIG. 6 shows a specific example of the offset adjustment table 240a.

It is determined whether or not the power of the optical scanning apparatus 200 is on (S100), and when the power is on (S100: Yes), it is determined whether or not the power of the laser driver 210 is turned on (S110). If the power of the laser driver 210 is on (S110: Yes), the light emission amount of the laser light emitting unit 200a is detected by the light amount detection unit 260 (S120).

Next, the laser driver control unit 250 controls (APC control) so that the light emission amount of the laser light emitting unit 200a detected by the light amount detection unit 260 becomes the target light amount (Vref signal) (S130).

Next, it is determined whether or not the mode is the shading correction mode (S140), and if it is the shading correction mode (S140: Yes), the target light amount (S140: Yes) is referred to with reference to the offset adjustment table 240a stored in the storage unit 160. The offset value (signal Voffset) is determined based on the signal Vref) of (S150). Specifically, as shown in FIG. 4, in the offset adjustment table 240a, the target light amount (signal Vref) is 0 to 255 (dec), and the offset value (signal Voffset) is 192 to 32 (dec). It is set in the range of, and the offset value decreases as the target light intensity increases.
If the mode is not the shading correction mode (S140: No), the process proceeds to S170.

Next, the shading correction value signal (Vshade) is superposed on the analog signal offset value signal (Voffset) to generate an analog signal (Vsw) in which the shading correction signal is offset (S160).

Next, the amount of light emitted from the laser light emitting unit (LD) 200a is controlled by inputting an analog signal (Vsw) to the laser driver (LD Driver) 210 (S170).

Next, it is determined whether or not to end the control (S180), and if the control is not ended (S180: No), the process returns to S110 and the control is repeated. It ends with the end of control (S180: Yes).

[1.5 Operation example]
FIG. 7 shows an example of a shading correction value signal (Vshade), an offset value signal (Voffset), and an offset shading correction signal (laser driver input signal: Vsw). Both signals are analog voltage signals. The BD signal is a detection signal from the start end side of the main scanning region detected by the beam detect sensor (BD sensor) 200k.

As shown in FIG. 7, the shading correction value signal (Vshade) has a portion close to 0 level, but the offset value signal (Voffset) is superposed and lifted, and the offset shading correction signal (Vsw) is used. It is far from the 0 level. The analog signal of the shading correction signal (Vsw) in this offset state is input to the laser driver 210.

[1.6 effect]
According to the optical scanning apparatus of the embodiment, a shading correction value signal (Vshade) is used as an offset value signal (Voffset) linked with a target light amount signal (reference voltage signal (Vref)) of the laser driver control unit 250 during APC control. ) To generate a shading correction signal (Vsw) in an offset state and adjust the offset.

Therefore, since the shading correction value is only offset, it is not necessary to calculate and set the shading correction value for all segments again according to the change in the target light amount such as the environment and life correction. In comparison, the calculation and control load is reduced.

Further, even if shading is performed with a low target light amount, the shading resolution is maintained.

Since the offset value is stored in the storage unit 160 such as the ROM by the offset adjustment table 240a, it is not necessary to recalculate the set value of the analog signal according to the change in the target light amount such as the environment and the life change, so that the processing takes time. I don't need it. Further, since the processing of the CPU spent for the processing becomes unnecessary, the usage load of the CPU can be reduced.

Further, since the offset value is individually stored corresponding to the target light amount, the target light amount does not deviate even if the PI (light-current) characteristics and the fundamental light amount of the laser light emitting element (laser light emitting unit 200a) vary.

[2. Second Embodiment]
In the second embodiment, the offset adjustment table 240a of the optical scanning apparatus 200 is set for each temperature. FIG. 8 shows an example of PI (photo-current) characteristics of the laser emitting element that changes with temperature, and FIGS. 9 (a) to 9 (c) show an example of an offset adjustment table for each temperature.

As shown in FIG. 8, the laser light emitting element drives and emits light when the operating current IF exceeds the oscillation start current (threshold value) _Ith , and the oscillation start current Ith (
Ith1, Ith2, _Ith3 ...), the operating current IF, and the laser emission amount P change.

In FIG. 8, when the temperature is 10 ° C., the laser emission amount P is large even if the oscillation start current Ith1 and the operating current IF are small, but the temperature ranges from 25 ° C. (oscillation start current _Ith2 ) to 40 ° C. (oscillation start current Ith3). It can be seen that the oscillation start current Ith and the operating current IF increase in order to obtain the same laser emission amount _P as 10 ° C. as the temperature increases.

In the second embodiment, as shown in FIG. 9, the offset adjustment table for each temperature band is stored in the ROM of the storage unit 160, and the table to be referred to is switched for each temperature. 9A is an offset adjustment table having a temperature band of 5 to 15 ° C., FIG. 9B is an offset adjustment table having a temperature band of 15 to 30 ° C., and FIG. 9C is an offset adjustment table having a temperature band of 30 to 45 ° C.

As can be understood by comparing the offset adjustment tables shown in FIGS. 9A, 9B, and 9C, the offset value signal (Voffset) with respect to the target light amount signal (Vref) increases as the temperature rises. As a result, the shading correction value is offset so as to increase as the temperature rises. That is, as the temperature rises, the amount of light emitted by the laser light emitting element with respect to the same drive current decreases, so the offset value is increased to increase the drive current, thereby bringing the amount of light emitted closer to the target amount of light.

According to the second embodiment, as shown by an example in FIG. 9, by storing the offset value for each temperature, the target is even if the PI (photo-current) characteristic of the laser emitting element (laser emitting unit 200a) varies depending on the temperature. It has a remarkable effect that the amount of light does not deviate.

Although the offset value is stored for each temperature in the second embodiment, the offset value storage of the present disclosure can store the offset value according to an event other than the temperature.

For example, if the offset values are individually stored for each of the light intensity-current characteristics (PI characteristics) of the laser emitting unit or the root light intensity characteristics, the optimum offset value according to the individual characteristics of the laser element is selected. It is possible to input an analog signal that reaches the target amount of light to the laser driver.

Conventionally, it is necessary to calculate the voltage set value of the analog signal according to the target light amount and calculate it again according to the problem in the method of approaching the target light amount, that is, the change in the target light amount such as the environment and life correction. There are problems such as poor shading resolution when shading with a low target light amount, and deviation in the target light amount when the PI characteristics and root light amount of the laser element vary individually. According to the present disclosure, by storing the offset value, it is possible to solve the problem simply by applying an offset to the analog input without requiring calculation.

Further, the signal offset by the offset value is not limited to the shading correction signal as long as it is an analog signal to the laser driver, and can be applied to various analog signals such as a target light amount (Vref) signal and an image input signal. As a result, in an optical scanning device using a laser driver in which the excess current from the bias current increases or decreases in proportion to the analog signal, the analog signal is offset according to the target light amount in order to approach the target light amount. Can be done.

Although the embodiments have been described above, the specific configuration is not limited to the embodiments, and the claims include designs and the like within a range that does not deviate from the gist of the present invention.

Further, in the embodiment, the program that operates in each device is a program that controls a CPU or the like (a program that causes a computer to function) so as to realize the functions of the above-described embodiment. Then, the information handled by these devices is temporarily stored in a temporary storage device (for example, RAM) at the time of processing, then stored in various ROM or HDD storage devices, and read and corrected by the CPU as necessary. Writing is done.

Here, as the recording medium for storing the program, a semiconductor medium (for example, ROM, a non-volatile memory card, etc.), an optical recording medium / magneto-optical recording medium (for example, DVD (Digital Versataile Disc), MO (magneto Optical Disc), etc. Any non-temporary recording medium such as (MD (Mini Disc), CD (Compact Disc), BD, etc.), magnetic recording medium (for example, magnetic tape, flexible disk, etc.) may be used.

In addition, by executing the loaded program, not only the functions of the above-described embodiment are realized, but also by processing in collaboration with the operating system or other application programs based on the instructions of the program, the present invention Disclosure functions may also be realized.

Further, when the program is distributed to the market, the program can be stored and distributed in a general-purpose storage device, or transferred to a server computer connected via a network such as the Internet. In this case, it goes without saying that the storage device of the server computer is also included in the present invention.

Further, a part or all of each device in the above-described embodiment may be realized as an LSI (Large Scale Integration) which is typically an integrated circuit. Each functional block of each device may be individually chipped, or a part or all of them may be integrated into a chip. Further, the method of making an integrated circuit is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. In addition, when an integrated circuit technology that replaces LSI appears due to advances in semiconductor technology, it is of course possible to use an integrated circuit based on this technology.

10 Image forming device 100 Control unit 130 Image forming unit 130a Photoreceptor drum 160 Storage unit 200 Optical scanning device 200a Laser emitting unit 200k BD sensor 210 Laser driver 220 Optical scanning unit 230 Shading correction signal unit 240 Offset value determination unit 240a Offset adjustment table 250 Laser driver control unit 260 Light intensity detection unit

Claims (10)

A laser emitting unit that increases or decreases the excess current from the bias current in proportion to the input analog signal,
The laser driver for driving the laser emitting unit and
An optical scanning unit that scans the laser beam emitted from the laser emitting unit onto the object,
An offset value determining unit that determines an offset value of an analog signal input to the laser emitting unit based on a target light amount of the laser emitting unit, and an offset value determining unit.
A laser driver control unit that controls the amount of light emitted from the laser light emitting unit by superimposing a signal having a determined offset value on the analog signal to offset it and inputting the offset analog signal to the laser driver.
An optical scanning device characterized by being equipped with. A shading correction signal unit for outputting a shading correction signal for shading correction of the light scanned on the object is provided.
The optical scanning apparatus according to claim 1, wherein the analog signal includes a shading correction signal. A light amount detection unit for detecting the light emission amount of the laser light emitting unit is provided.
The laser driver control unit controls the light emission amount of the laser light emitting unit detected by the light amount detection unit so as to reach a target light amount.
The optical scanning apparatus according to claim 1 or 2, wherein the offset value determining unit determines an offset value based on the target light amount. It has a storage unit that stores an offset adjustment table that sets the relationship between the target light amount and the offset value.
The optical scanning apparatus according to claim 1, wherein the offset value determining unit determines an offset value from the offset adjusting table according to the target light amount. The light according to claim 1 to 4, wherein the offset adjustment table individually stores an offset value for each of the light amount-current characteristic or the root light amount characteristic of the laser emitting unit. Scanning device. The optical scanning apparatus according to claim 1, wherein the offset value changes depending on the temperature. The optical scanning apparatus according to claim 6, wherein the storage unit stores a plurality of offset adjustment tables according to the temperature. The optical scanning apparatus according to claim 1 to 7.
An image carrier in which an electrostatic latent image is formed on the surface by scanning the laser light emitted from the laser light emitting unit by the optical scanning unit.
An image forming apparatus including a developing unit for developing an electrostatic latent image formed on the surface of the image carrier. A laser emitting unit whose excess current from the bias current increases or decreases in proportion to the input analog signal, a laser driver for driving the laser emitting unit, and a laser beam emitted from the laser emitting unit are placed on an object. A control method for an optical scanning device including an optical scanning unit for scanning.
An offset value determining step of determining an offset value of an analog signal input to the laser emitting unit based on a target light amount of the laser emitting unit, and an offset value determining step.
A laser driver control step of controlling the amount of light emitted from the laser emitting unit by superimposing a signal having a determined offset value on the analog signal to offset it and inputting the offset analog signal to the laser driver.
A control method characterized by being equipped with. A laser emitting unit whose excess current from the bias current increases or decreases in proportion to the input analog signal, a laser driver for driving the laser emitting unit, and a laser beam emitted from the laser emitting unit are placed on an object. A computer of an optical scanning device equipped with an optical scanning unit for scanning,
An offset value determination function that determines the offset value of the analog signal input to the laser light emitting unit based on the target light amount of the laser light emitting unit, and
A laser driver control function that controls the amount of light emitted from the laser emitting unit by superimposing a signal having a determined offset value on the analog signal to offset it and inputting the offset analog signal to the laser driver.
A program that realizes.

Images