JPH04352119A - Magnification error correcting method for scanning optical device - Google Patents

Abstract

PURPOSE:To correct and minimize a magnification error at all times even if environment is changed by controlling a basic clock according to the difference between the time of the scanning of a scanned body in a main scanning direction and a reference scanning time. CONSTITUTION:An arithmetic circuit 15 inputs luminous flux detection signals from sensors 8 and 9 and calculates the scanning time of the scanning of the scanned surface 7 with luminous flux from image formation optical systems 5 and 6 in the main scanning direction by using the time difference between those luminous flux detection signals. A ROM 16, on the other hand, is stored with the reference time of scanning of the scanned surface 7 with the luminous flux from the image formation optical systems 5 and 6 in the main scanning direction previously, and the arithmetic circuit 15 compares the real scanning time calculated from the luminous flux detection signals from the sensors 8 and 9 with the reference scanning time stored in the ROM 16 to calculate the difference. Then one kind of basic frequency which minimizes the magnification error among plural kinds of basic frequencies stored in the ROM 16 is selected and read out to control the basic clock, thereby correcting the magnification error of the scanning optical device.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for correcting magnification errors in scanning optical devices used in laser printers, digital copying machines, and the like.

0002

2. Description of the Related Art Conventionally, scanning optical devices have been used in laser printers, digital copying machines, etc. For example, after a photoreceptor is rotationally driven by a drive mechanism and uniformly charged by a charger, the surface of the photoreceptor is transferred to the scanning optical device. An electrostatic latent image is formed by being scanned in the main scanning direction by a light beam carrying image information, and this electrostatic latent image is developed by a developing device and transferred to a recording material, so that this recording material is recorded. It is discharged outside as a material.

[0003] A scanning optical device includes a light source consisting of a semiconductor laser or the like that emits a light beam, a deflector that deflects the light beam from the light source as it rotates at a constant angular velocity, and a light beam from the deflector that directs the light beam in the main scanning direction. Scanned at a constant speed and sub-scanned (rotated)
a surface to be scanned, such as a photoreceptor, and an imaging optical system that forms an image of the light beam from the deflector on the surface to be scanned, and modulates the light beam with an information signal to form an image on the surface to be scanned. Writing a latent image.

[0004] The deflector used is a rotating polygon mirror or the like, and the deflection angle of the light beam is often relatively narrow. Further, the imaging optical system has an fθ characteristic that causes a beam deflected by a deflector rotating at a constant angular velocity to be imaged on the scanned surface so that the scanned surface is scanned at a constant speed in the main scanning direction. A combination of many lenses made of glass or the like is used.

Furthermore, Japanese Patent Laid-Open No. 2-161410 describes a scanning optical device in which plastic is used for the imaging optical system, and the curvature of field can be corrected regardless of temperature. has been done. However, this Japanese Patent Application Laid-Open No. 2-161410 does not describe the uniform speed scanning property of the light beam on the surface to be scanned and the magnification error of the written latent image.

Furthermore, Japanese Patent Laid-Open No. 62-32764 discloses that in the above-mentioned scanning optical device, in order to scan the surface to be scanned with a light beam at a constant speed in the main scanning direction, the scanning is performed in accordance with a clock. A device that continuously changes the clock frequency is described.

[0007]

[Problems to be Solved by the Invention] Conventionally, in the above-mentioned scanning optical device, since the deflection angle of the light beam is relatively narrow, it is possible to suppress the fθ characteristic of the imaging optical system to a small value. there were. Therefore, the time t required for scanning per pixel on the scanned surface is t≒L/(f×ω×N) L: Effective scanning width of the scanned surface N: Number of pixels within the effective scanning width of the scanned surface If ω is the rotational angular velocity of the deflector and f is the focal length of the imaging optical system in the main scanning direction, then the error in the magnification of the latent image on the scanned surface relative to the original image (hereinafter simply referred to as magnification) can be kept small. did it.

However, recently, there has been a demand for a wider field of view of the imaging optical system due to the miniaturization of devices, and a reduction in the number of lenses in the imaging optical system due to lower prices. It has become difficult to keep the fθ characteristic of the imaging optical system small, resulting in a drawback that magnification error becomes large.

In the method described in the above-mentioned Japanese Patent Application Laid-open No. 62-32764, the clock frequency is continuously changed, so this drawback can be overcome, but the scanning time for each pixel on the surface to be scanned is A circuit for continuous change is required, which increases cost.

In addition, in recent years, there has been a movement to make part or all of the imaging optical system plastic in scanning optical devices, as shown in the above-mentioned Japanese Patent Application Laid-Open No. 2-161410, but the imaging optical system after the deflector is made of plastic. In this case, the fθ characteristic of the imaging optical system changes due to a change in the shape or the refractive index due to a change in the environmental temperature, and the magnification error fluctuates.

[0011] Furthermore, even when glass is used for the imaging optical system in a scanning optical device, a semiconductor laser is often used as a light source. The fθ characteristic of the imaging optical system changes due to the chromatic aberration, and the magnification error fluctuates.

Furthermore, in the scanning optical device, since the degree of influence of temperature on the magnification error of each component is different, the magnification error fluctuates depending on the internal temperature distribution.

The present invention aims to improve the above-mentioned drawbacks and to provide a method for correcting magnification errors in a scanning optical device that can be realized at low cost and that can correct magnification errors regardless of environmental changes, temperature distribution within the device, etc. purpose.

[0014]

[Means for Solving the Problems] In order to achieve the above object, the invention of claim 1 provides a light source that emits a luminous flux, a deflector that deflects the luminous flux from this light source, and a main unit that uses the luminous flux from this deflector. a surface to be scanned that is scanned in a scanning direction; an imaging optical system that forms an image of the light beam from the deflector on the surface to be scanned;
In the magnification error correction method for a scanning optical device, the scanning optical device has a clock generating section that generates a basic clock that determines the timing at which the surface to be scanned is scanned in the main scanning direction by the light beam from the deflector. The invention according to claim 2 provides the method according to claim 1, wherein the scanning optical device detects the scanning time in the direction, and controls the basic clock based on the difference between this time and a reference scanning time to correct the magnification error of the scanning optical device. In a magnification error correction method for a scanning optical device, a control means is provided to control the frequency of the basic clock in an analog manner, detects a time during which the surface to be scanned is scanned in the main scanning direction, and compares this time with a reference scanning time. The control means controls the basic clock to correct the magnification error of the scanning optical device due to the difference between the control means and the scanning optical device. A scanning device comprising: a deflector for scanning, a surface to be scanned which is scanned in the main scanning direction and sub-scanned by a light beam from the deflector, and an imaging optical system for forming an image of the light beam from the deflector on the surface to be scanned. In a magnification error correction method for an optical device, the time during which the surface to be scanned is scanned in the main scanning direction is detected, and the rotation speed of the deflector and the sub-scanning of the surface to be scanned are determined based on the difference between this time and a reference scanning time. The invention according to claim 4 includes: a light source that emits a light beam; a deflector that deflects the light beam from the light source; and a light beam from the deflector. a surface to be scanned that is scanned in the main scanning direction; an imaging optical system that forms an image of the light beam from the deflector on the surface to be scanned; and a surface to be scanned that is scanned in the main scanning direction by the light beam from the deflector. In the magnification error correction method for a scanning optical device, the scanning optical device has a clock generating section that generates a basic clock that determines the timing at which the optical scanning device is scanned. The basic clock is controlled to correct a magnification error of the scanning optical device, and the invention according to claim 5 provides a method for correcting a magnification error of the scanning optical device according to claim 4, in which the frequency of the basic clock is controlled in an analog manner. further comprising a control means for detecting the temperature inside the scanning optical device by a temperature detection means, and controlling the basic clock by the control means based on a temperature detection signal from the temperature detection means to correct a magnification error of the scanning optical device. The invention according to claim 6 provides a light source that emits a light beam, a deflector that deflects the light beam from the light source, a scanned surface that is scanned in the main scanning direction by the light beam from the deflector, and the deflector. In a magnification error correction method for a scanning optical device having an imaging optical system that forms an image of a light flux from 7. A magnification error of the scanning optical device is corrected by controlling the rotation speed of the deflector and the sub-scanning speed of the scanned surface based on the detection signal.
According to the invention of claim 4, 5 or 6, the temperature sensing means is disposed at an upper part and/or a lower part of the scanning optical device, , the light source of the scanning optical device is a laser light source, the temperature detection means is arranged near the laser light source, and the temperature of the laser light source is detected by the temperature detection means, At 8, the temperature sensing means is arranged at an upper and/or lower part within the scanning optical device.

[0015]

Embodiment FIGS. 2 and 3 schematically show a scanning optical device used in an embodiment of the present invention. The laser light source 1 is composed of a semiconductor laser and a collimating lens, and emits a substantially parallel beam of light. The light beam from the laser light source 1 passes through a beam shaping cylinder lens 2, forms an image on a reflecting surface 4 of a deflector 3 made of a rotating polygon mirror, and is deflected by the rotation of the polygon mirror 3. The polygon mirror 3 is rotated by a motor at a constant angular speed in the direction of an arrow 3A, and deflects the light beam from the beam shaping cylinder lens 2 at a constant angular speed. The light beam deflected by the polygon mirror 3 passes through an imaging optical system 5, 6 consisting of two imaging lenses having anamorphic fθ characteristics, and scans the surface to be scanned 7 in the main scanning direction. Sensors 8 and 9 are arranged at both end positions on the surface to be scanned 7, and detect the light beams from the imaging optical systems 5 and 6 at both ends of the scanning area in the main scanning direction. The time it takes for the light beams from the imaging optical systems 5 and 6 to scan the scanned surface 7 in the main scanning direction corresponds to the difference in time during which the sensors 8 and 9 detect the light beams from the imaging optical systems 5 and 6. becomes. In addition, near the laser light source 1,
For example, temperature sensors 10 to 12 are installed at the end of the semiconductor laser.
are arranged, and the temperature sensors 10 to 12 detect the temperature and output a voltage signal according to the temperature. Furthermore, temperature sensors 13 and 14 are arranged at predetermined positions within the scanning optical device, for example, at both ends of the imaging optical systems 5 and 6, and these temperature sensors 13 and 14 detect the temperature and respond accordingly. outputs a voltage signal.

As described above, this scanning optical device is used in laser printers, digital copying machines, etc., and the surface to be scanned 7 is made of, for example, the surface of a photoreceptor. This photoreceptor is rotated by a motor to perform sub-scanning, and the imaging optical system 5, 6
It is repeatedly scanned in the width direction (main scanning direction) by the light beam from.

FIG. 1 shows the circuit configuration of this scanning optical device. The arithmetic circuit 15 receives the light flux detection signals from the sensors 8 and 9, and calculates the scanning time for the light fluxes from the imaging optical systems 5 and 6 to scan the scanned surface 7 in the main scanning direction based on the time difference between these light flux detection signals. calculate. On the other hand, the ROM 16 stores in advance a standard scanning time during which the light beams from the imaging optical systems 5 and 6 scan the scanned surface 7 in the main scanning direction, and the arithmetic circuit 1
5 compares the actual scanning time calculated from the luminous flux detection signals from the sensors 8 and 9 with the reference scanning time stored in the ROM 16, and calculates the difference therebetween. Here, a plurality of types of basic clock frequencies are stored in the ROM 16. The arithmetic circuit 15 operates according to the difference between the actual scanning time and the reference scanning time.
Among the plurality of fundamental frequencies stored in the ROM 16, one fundamental frequency with the minimum magnification error is selected and read out, and this fundamental frequency is D/A converted by the D/A converter 17. and output to the clock generating section 18. The clock generator 18 generates a clock,
The frequency of this clock is corrected by an analog signal from the D/A converter 17. The LD drive circuit 19 drives the semiconductor laser in the laser light source 1 using the clock from the clock generator 18, and this semiconductor laser is turned on/off by a modulation circuit according to image information and emits a light beam carrying an image signal. The surface to be scanned 7 is uniformly charged by the charger as described above, and then scanned in the main scanning direction by the light beam from the semiconductor laser to form an electrostatic latent image. After being developed and transferred onto a recording material, this recording material is discharged outside as a recorded matter.

FIG. 4 shows the configuration of the clock generating section 18. Phase comparator 20, low pass filter (LPF) 21
, voltage controlled oscillator (VCO) 22 and programmable divider 23 are PLL (Phase Locked
Loop), and the VCO 22 oscillates at a frequency f2 according to the input control voltage. The output signal of the VCO 22 is divided by a programmable divider 23 to a frequency f2/n with a division ratio n, and the phase is compared in a phase comparator 20 with a signal of a constant frequency f1 from an oscillator (not shown). The output signal of this phase comparator 20 corresponds to the phase difference between the signal from the oscillator and the output signal of the programmable divider 23, is converted into a DC voltage by the LPF 21, and is outputted to the VCO 22 as a control voltage. Therefore, the oscillation frequency f2 of the VCO 22 becomes f2=nf1. Programmable divider 23 is D/A converter 1
The frequency division ratio n is controlled by the analog signal from 7, and thereby the oscillation frequency f2 of the VCO 22 is corrected so that the magnification error is minimized. Frequency f from VCO22
The clock of 2 is mixed with a clock of frequency f3 from an oscillator (OSC) 25 by a double balanced mixer 24, a component of frequency f2+f3 is extracted by a tuner 26, and is binarized at 0V by a comparator 27. It becomes a clock of frequency f2+f3 and is output to the LD drive circuit 19 as is or via a D/A converter. Here, the frequency f1 is set to be 0.1% of the pixel clock frequency, for example 8 MHZ, that is, a frequency around 800 Hz, and the oscillation frequency f2 of the VCO 22 is approximately 2 MHZ. The oscillation frequency f3 of the OSC 25 is 6MHZ, and the frequency f2+f3 of the clock from the comparator 27 is 8M
It will be around HZ.

Although the arithmetic circuit 15 outputs the fundamental frequency read from the ROM 16 to the programmable divider 23 via the D/A converter 17, the fundamental frequency read from the ROM 16 is output directly to the programmable divider 23. You can.

FIG. 5 shows the circuit configuration of a scanning optical device used in another embodiment of the present invention. This scanning optical device uses the circuit shown in FIG. 5 in place of the circuit shown in FIG. 4 in the scanning optical device described above, and the same parts as those in the scanning optical device described above are given the same reference numerals. That is, in the above scanning optical device, the arithmetic circuit 15, ROM 16 and D/A
An arithmetic circuit 28, a ROM 29, and an analog control circuit 30 are used in place of the converter 17, and the ROM 29 stores in advance a reference scanning time during which the light beams from the imaging optical systems 5 and 6 scan the scanned surface 7 in the main scanning direction. Stored. The arithmetic circuit 28 compares the actual scanning time calculated from the light flux detection signals from the sensors 8 and 9 with a reference scanning time stored in the ROM 29 to calculate the scanning time difference. The analog control circuit 30 converts the scanning time difference from the arithmetic circuit 28 into a corresponding voltage signal and outputs it to the programmable divider 23 . For example, this analog control circuit 30 turns on a counter for a time corresponding to the scanning time difference from the arithmetic circuit 28, causes this counter to count clocks, and outputs each final count signal via a D/A converter. This can be achieved using a conventionally simple circuit.

FIG. 6 shows a circuit configuration of a scanning optical device used in another embodiment of the present invention. This scanning optical device uses a fuzzy control calculation circuit in the scanning optical device described above, and the light flux detection signals from sensors 8 and 9 are A/D converted by A/D converters 31 and 32, respectively. The signal is input to the fuzzy control calculation circuit 33. Furthermore, the luminous flux detection signals from the sensors 8 and 9 are transmitted to the A/D converter 3, respectively.
After A/D conversion by 4 and 35, the FIFO memory 3
6 and 37, the signal is delayed by one scan and inputted to the fuzzy control calculation circuit 33, and a reference scanning time signal is inputted to the fuzzy control calculation circuit 33 from a circuit not shown. The fuzzy control calculation circuit 33 is connected to the A/D converters 31 and 3.
A fuzzy calculation is performed to calculate the difference between the actual scanning time and the reference scanning time from the luminous flux detection signal from 2, the luminous flux detection signal after one scan from the A/D converters 34 and 35, and the reference scanning time signal. This is then output to the analog control circuit 30 via the D/A converter 38.

In the analog control circuit 30 shown in FIG. 5, instead of controlling the clock generator 18 by calculating the difference between the actual scanning time and the reference scanning time, the rotation speed of the deflector 3 and the scanned surface are The configuration may be such that the sub-scanning speed (linear speed of the photoreceptor) of 7 is controlled. Similarly, in the analog control circuit 30 of FIG. 6, instead of calculating the difference between the actual scanning time and the reference scanning time to control the clock generator 18, the rotation speed of the deflector 3 and the scanning surface are controlled. 7 sub-scanning speed (
The linear velocity of the photoreceptor may be controlled. Furthermore, in the circuits of FIGS. 4 and 5, the temperature inside the device is detected by detecting the temperature with temperature sensors near the sensors 8 and 9, and the clock generated by the clock generator 18 is further controlled by the temperature detection signal. You may also do so.

By the way, there are three main possible causes for the magnification error caused by changes in environmental conditions, particularly temperature changes. The first is a change in the shape of the imaging optical systems 5 and 6, the second is a change in the shape of the housing of the scanning optical system, and the third is a change in the oscillation wavelength of the semiconductor laser. Therefore, there is an optimal location to install a temperature sensor to correct these.

Regarding changes in the shape of the imaging optical systems 5 and 6,
As shown in FIG. 2, the temperature sensors 13 and 14 are connected to the imaging optical system 5.
, 6 is preferably installed near the imaging optical systems 5 and 6, such as at the ends of the optical systems 5 and 6. Furthermore, in response to changes in the shape of the housing of the scanning optical system, it is desirable to install temperature sensors at multiple locations, such as at the four corners of the housing. Furthermore, in response to fluctuations in the oscillation wavelength of a semiconductor laser,
For example, as shown in FIG. 2, it is desirable to install temperature sensors 10 to 12 at the ends of the semiconductor laser unit.

FIG. 7 shows a temperature correction circuit in the above scanning optical device. The arithmetic circuit 39 connects the temperature sensors 10 to 14
Each voltage signal from the A/D is compared with each reference temperature signal from a circuit not shown, and the difference between them is calculated.
The data is A/D converted by the converter 40 and written into the ROM 41. This ROM 41 reads input signals written from the A/D converter 40 when not being recorded. The signal read from the ROM 41 is D/A converted by the D/A converter 42 and output to the control circuit 43. Deflector drive circuit 4
4 is a deflector 3 by driving a deflector drive motor.
For example, rotate the photoreceptor drive circuit 45 at 400 dpi.
By driving the photoreceptor driving motor, the photoreceptor is rotated at a linear speed of 63.5 mm/s, for example, and the scanned surface 7 is moved in the sub-scanning direction. The control circuit 43 is the D/A converter 4
By controlling the deflector drive circuit 44 and the photoreceptor drive circuit 45 according to input signals from the deflector 3, the rotation speed of the deflector 3 and the linear velocity of the photoreceptor are adjusted so that the magnification error caused by temperature fluctuation is corrected. control. In this case, the rotational speed of the deflector 3 and the linear velocity of the photoreceptor are controlled during non-recording so that they are the same for the same recorded object, and the distortion of the recorded image due to the control for each main scan is reduced. Does not occur. Further, the deflector drive circuit 44 and the photoreceptor drive circuit 45 are configured using a clock generation section similar to the clock generation section 18, and the clock generated by this clock generation section is controlled by the control circuit 43. The rotational speed of the photoreceptor and the linear speed of the photoreceptor may be controlled. Furthermore, the temperature sensor may be arranged at an upper part and/or a lower part within the scanning optical device.

FIG. 8 shows an example of the relationship among the effective scanning period, scanning start signal, clock control signal, etc. in the scanning optical device. Generally, after the power is turned on, the deflector 3 consisting of a rotating polygon mirror rotates at a low speed and enters a standby state for image recording. In this standby state, the clock control signal (RE) goes low and its inverted signal (WE) goes high. The clock control signal (RE) and inverted signal (WE) are each RO
This is a signal that selects whether the M41 signal can be read or written.
) is at a high level, signals can be read in accordance with the address signal, and when the inverted signal (WE) is at a high level, signals from the A/D converter 40 can be written in accordance with the address signal. Signals are written into the ROM 41 once after the power is turned on, and thereafter every time immediately before one page of image recording is performed. Address setting for the ROM 41 uses a counter that is cleared each time each surface of the deflector 3, which is a rotating polygon mirror, becomes a beam scanning surface. This is done by counting the scan start signal that is generated when the next scan starts. This scan start signal may be replaced with an ineffective scan period signal.

[0027]
stomach.

[Effect of the invention] As described above, according to the invention of claim 1,
A light source that emits a light beam, a deflector that deflects the light beam from the light source, a scanned surface that is scanned in the main scanning direction by the light beam from the deflector, and a light beam from the deflector that is directed to the scanned surface. A magnification error correction method for a scanning optical device having an imaging optical system that forms an image, and a clock generation unit that generates a basic clock that determines the timing at which the surface to be scanned is scanned in the main scanning direction by the light beam from the deflector. In this method, the time during which the surface to be scanned is scanned in the main scanning direction is detected, and the basic clock is controlled based on the difference between this time and a reference scanning time to correct the magnification error of the scanning optical device.
Even if the environment changes, the magnification error can always be corrected to the minimum, and it can be realized at low cost.

[0028] Furthermore, according to the invention of claim 2, claim 1
In the magnification error correction method for a scanning optical device described above, a control means is provided to control the frequency of the basic clock in an analog manner, detects the time during which the surface to be scanned is scanned in the main scanning direction, and compares this time with the reference scanning. Since the control means controls the basic clock according to the difference from the time and corrects the magnification error of the scanning optical device, the magnification error can always be corrected to the minimum even if the environment changes, and it can be realized at low cost. can.

According to the third aspect of the invention, there is provided a light source that emits a light beam, a deflector that deflects the light beam from the light source as it rotates, and a light beam that is scanned in the main scanning direction by the light beam from the deflector and scanned in the sub-scanning direction. In the magnification error correction method for a scanning optical device having a scanned surface and an imaging optical system that images a light beam from the deflector on the scanned surface, the scanned surface is scanned in a main scanning direction. The rotational speed of the deflector and the sub-scanning speed of the surface to be scanned are controlled based on the difference between this time and the reference scanning time to correct the magnification error of the scanning optical device. Even if the magnification error changes, the magnification error can always be corrected to the minimum, and it can be realized at low cost.

According to the fourth aspect of the invention, a light source that emits a light beam, a deflector that deflects the light beam from the light source, and a scanned surface that is scanned in the main scanning direction by the light beam from the deflector. an imaging optical system that forms an image of the light beam from the deflector on the scanned surface; and a clock generator that generates a basic clock that determines the timing at which the scanned surface is scanned in the main scanning direction by the light beam from the deflector. In the magnification error correction method for a scanning optical device having Since the magnification error is corrected, even if the temperature distribution within the apparatus changes, the magnification error can be corrected more precisely, and it can be realized at low cost.

According to the fifth aspect of the invention, in the magnification error correction method for a scanning optical device according to the fourth aspect, a control means for controlling the frequency of the basic clock in an analog manner is provided, and the temperature inside the scanning optical device is is detected by the temperature detection means, and the basic clock is controlled by the control means using the temperature detection signal from the temperature detection means to correct the magnification error of the scanning optical device, so even if the temperature distribution inside the device changes, The magnification error can be corrected more precisely and can be realized at low cost.

According to the sixth aspect of the invention, a light source that emits a light beam, a deflector that deflects the light beam from the light source, and a scanned surface that is scanned in the main scanning direction by the light beam from the deflector. In a magnification error correction method for a scanning optical device having an imaging optical system that images a light beam from the deflector on the scanned surface, the temperature inside the scanning optical device is detected by a temperature detection means, Since the rotational speed of the deflector and the sub-scanning speed of the scanned surface are controlled by the temperature detection signal of the means to correct the magnification error of the scanning optical device, even if the temperature distribution inside the device changes, it can be more precisely corrected. The magnification error can be corrected, and it can be realized at low cost.

According to the seventh aspect of the present invention, in the fourth, fifth, or sixth aspect, the temperature detection means is disposed at the upper and/or lower part of the scanning optical device, so that the temperature distribution inside the device changes. However, the magnification error can be corrected more precisely, and it can be realized at low cost.

According to claim 8, in the above-mentioned claim 4, 5, or 6, the light source of the scanning optical device is a laser light source, and the temperature detecting means is disposed near the laser light source, and the temperature detecting means Since the temperature of the laser light source is detected by this method, even if the temperature distribution inside the device changes, the magnification error can be corrected more precisely, and it can be realized at low cost.

According to the invention of claim 9, in claim 8, the temperature detection means is disposed at the upper and/or lower part of the scanning optical device, so that even if the temperature distribution inside the device changes, it can be detected more finely. The magnification error can be corrected, and it can be realized at low cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the circuit configuration of a scanning optical device used in an embodiment of the present invention.

FIG. 2 is a perspective view schematically showing the scanning optical device.

FIG. 3 is a front view schematically showing the scanning optical device.

FIG. 4 is a block diagram showing the configuration of a clock generation section in the scanning optical device.

FIG. 5 is a block diagram showing the circuit configuration of a scanning optical device used in another embodiment of the present invention.

FIG. 6 is a block diagram showing a circuit configuration of a scanning optical device used in another embodiment of the present invention.

FIG. 7 is a block diagram showing a temperature correction circuit in the scanning optical device.

FIG. 8 is a timing chart of the temperature correction circuit.

[Explanation of symbols]

8, 9 Sensor 15 Arithmetic circuit 16 ROM 17 D/A converter 18 Clock generation section 19 LD drive circuit

Claims (9)

[Claims] 1. A light source that emits a luminous flux, a deflector that deflects the luminous flux from the light source, a scanned surface that is scanned in the main scanning direction by the luminous flux from the deflector, and a scanning surface that deflects the luminous flux from the deflector. A scanning optical device comprising: an imaging optical system that forms an image on the scanned surface; and a clock generator that generates a basic clock that determines the timing at which the scanned surface is scanned in the main scanning direction by the light beam from the deflector. In the magnification error correction method, the time during which the scanned surface is scanned in the main scanning direction is detected, and the basic clock is controlled based on the difference between this time and a reference scanning time to correct the magnification error of the scanning optical device. A magnification error correction method for a scanning optical device, characterized in that: 2. A magnification error correction method for a scanning optical device according to claim 1, further comprising control means for controlling the frequency of the basic clock in an analog manner, and controlling the time during which the scanned surface is scanned in the main scanning direction. A method for correcting a magnification error of a scanning optical device, characterized in that the magnification error of the scanning optical device is corrected by detecting the difference between this time and a reference scanning time by controlling the basic clock by the control means. 3. A light source that emits a light beam, a deflector that deflects the light beam from the light source as it rotates, and a scanned surface that is scanned in the main scanning direction and sub-scanned by the light beam from the deflector. A magnification error correction method for a scanning optical device having an imaging optical system for forming an image of a light beam from the deflector on the surface to be scanned includes: detecting the time during which the surface to be scanned is scanned in the main scanning direction; The magnification error of the scanning optical device is corrected by controlling the rotation speed of the deflector and the sub-scanning speed of the scanned surface based on the difference between the time and the reference scanning time. Correction method. 4. A light source that emits a luminous flux, a deflector that deflects the luminous flux from the light source, a scanned surface that is scanned in the main scanning direction by the luminous flux from the deflector, and a scanning surface that deflects the luminous flux from the deflector. A scanning optical device comprising: an imaging optical system that forms an image on the scanned surface; and a clock generator that generates a basic clock that determines the timing at which the scanned surface is scanned in the main scanning direction by the light beam from the deflector. In the magnification error correction method, the temperature inside the scanning optical device is detected by a temperature detection means, and the basic clock is controlled by a temperature detection signal from the temperature detection means to correct the magnification error of the scanning optical device. Features a magnification error correction method for scanning optical devices. 5. A magnification error correction method for a scanning optical device according to claim 4, further comprising a control means for controlling the frequency of the basic clock in an analog manner, and detecting a temperature inside the scanning optical device by a temperature detection means. A method for correcting a magnification error in a scanning optical device, characterized in that the basic clock is controlled by the control device based on a temperature detection signal from the temperature detection device to correct a magnification error in the scanning optical device. 6. A light source that emits a luminous flux, a deflector that deflects the luminous flux from the light source, a scanned surface that is scanned in the main scanning direction by the luminous flux from the deflector, and a scanning surface that deflects the luminous flux from the deflector. In the magnification error correction method for a scanning optical device having an imaging optical system that forms an image on the surface to be scanned, the temperature inside the scanning optical device is detected by a temperature detection means, and the temperature detection signal of the temperature detection means is used to detect the temperature within the scanning optical device. A method for correcting a magnification error in a scanning optical device, characterized in that the magnification error in the scanning optical device is corrected by controlling the rotation speed of a deflector and the sub-scanning speed of the surface to be scanned. 7. A magnification error correction method for a scanning optical device according to claim 4, wherein the temperature sensing means is disposed at an upper portion and/or a lower portion within the scanning optical device. 8. In claim 4, 5, or 6, the light source of the scanning optical device is a laser light source, and the temperature detecting means is disposed near the laser light source, and the temperature detecting means detects the temperature of the laser light source. A magnification error correction method for a scanning optical device characterized by detecting temperature. 9. A magnification error correction method for a scanning optical device according to claim 8, wherein the temperature sensing means is disposed at an upper portion and/or a lower portion within the scanning optical device.