JP2002350769A - Exposure equipment - Google Patents

Abstract

(57) [Problem] To provide an exposure apparatus for optically correcting image light to be distributed to a photoreceptor by a liquid crystal lens. SOLUTION: A liquid crystal lens 4 having electrodes 46 and 47 disposed thereon, a photosensitive drum 11, a control circuit 22, and an ultrasonic sensor 9 are provided.
Is provided. The electrodes 46 and 47 form a three-dimensional electric field distribution according to the optical correction to be applied to the light beam in the liquid crystal lens 4 for optical correction of the light beam emitted from the light source. The control circuit 22 applies a voltage between the electrodes 46 and 47 to deflect the light beam irradiation direction in the sub-scanning direction B. The ultrasonic sensor 9 detects a moving error of the photosensitive drum 11 in the sub-scanning direction B by ultrasonic waves. The power supply to the electrodes 46 and 47 of the liquid crystal lens 4 is controlled based on the detection result of the ultrasonic sensor 9 to deflect the light beam that scans the surface of the photosensitive drum 11 in the main scanning direction A in the sub-scanning direction B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus for exposing a photoreceptor with a light beam from a light source to form an electrostatic latent image on the surface of the photoreceptor in electrophotographic image formation. And an exposure apparatus having a liquid crystal lens disposed in the optical path of the exposure apparatus.

[0002]

2. Description of the Related Art In electrophotographic image formation, an electrostatic latent image is formed on the surface of a photoreceptor uniformly charged with a predetermined charge by photoconductive action, and this electrostatic latent image is visualized as a toner image. Transfer to recording paper. For this reason, an image forming apparatus that forms an electrophotographic image uses an exposure device that exposes and scans the surface of a photoconductor with image light.

In this exposure apparatus, a light source is driven based on image data, and a light beam, which is image light emitted from the light source, is orthogonal to a moving direction (sub-scanning direction) of the photosensitive member surface via a mirror. Direction (main scanning direction) to write an electrostatic latent image line by line on the surface of the photoconductor.
In this case, in order to form an image having excellent reproducibility through the surface of the photoconductor, not only the image light irradiated from the light source in the exposure device is accurately formed on the surface of the photoconductor, but also the image light It is necessary to perform optical correction such as distortion, curvature of field, and surface tilt.

Further, since the image density changes depending on the exposure time of the image light on the surface of the photoreceptor, it is necessary for the optical correction of the image light to deflect the surface of the photoreceptor at a constant speed in the main scanning direction. Become. For these reasons, the exposure apparatus is provided with a plurality of optical lenses for optical correction in the optical path of image light from the light source to the surface of the photoconductor.

However, in order to perform a plurality of necessary optical corrections on image light using an optical lens made of glass or plastic, a large number of optical lenses must be arranged in the optical path of the image light. However, there is a problem that the size of the exposure apparatus is increased and the cost is increased.

Therefore, Japanese Patent Application Laid-Open No. 4-196869 discloses a configuration in which a liquid crystal device having a non-uniform refractive index performs a plurality of optical corrections on image light from a light source.

In this configuration, a liquid crystal lens whose refractive index is changed by controlling a voltage to be applied is used to perform not only optical correction of distortion, curvature of field, surface tilt, etc., but also
It is suggested that a function of an f-θ lens for scanning the image light on the surface of the photoconductor at a constant speed in the main scanning direction can also be obtained.

On the other hand, in an electrophotographic image forming apparatus, a cylindrical photosensitive drum is generally used as a photosensitive member, and at a timing synchronized with the movement of the surface of the photosensitive drum in the sub-scanning direction by rotation. The exposure device scans image light in the main scanning direction. However, if the rotation of the photoconductor drum becomes uneven, the scanning interval of the image light on the surface of the photoconductor drum changes widely and narrowly, and density unevenness occurs in a formed image.

For this reason, Japanese Patent Application Laid-Open No. H5-40398 discloses a method of arranging a deflecting member which generates a deflecting effect by an electro-optical effect in the optical path of image light, and detecting the speed information in the sub-scanning direction on the surface of the photosensitive drum. There is disclosed a configuration in which the voltage applied to the deflecting member is controlled on the basis of the above, so that the image light is deflected in the sub-scanning direction according to the rotation unevenness of the photosensitive drum.

Conventionally, the rotation of a photosensitive drum in an image forming apparatus is detected by a rotary encoder, and the quality of a printed image has been improved by feedback-controlling the speed unevenness.

However, since the rotary encoder described above detects the rotation of the drum shaft, it cannot detect the speed fluctuation of the photosensitive member surface due to the eccentricity of the drum. Would.

Further, since the photosensitive drum is detached from the apparatus for maintenance and replacement, a speed error occurs due to the accuracy of the detachable chucking mechanism.

Further, in order to perform highly accurate detection by the above-described method, a high-resolution rotary encoder is required, so that it cannot be realized at low cost. (For example, in order to detect a frequency fluctuation frequency component up to 200 Hz with a 100 mm / s φ30 drum, 1000 pulse / r
ev, 1000 pulse to detect at 1200 dpi
/ Rev is required)

As a method for solving the above-mentioned problem, Japanese Patent Application Laid-Open No. 8-160829 discloses that a drum speed can be detected by using a laser Doppler velocimeter, thereby making it possible to detect a photosensitive drum speed with high accuracy.

[0015]

However, in the configuration disclosed in Japanese Patent Application Laid-Open No. 4-196869, optical correction of distortion, field curvature and surface tilt using a liquid crystal lens, and the surface of a photosensitive member There is no description about the specific method of arranging the electrodes for uniform velocity deflection in,
It is actually difficult to replace an optical lens with a liquid crystal lens.

In the configuration disclosed in Japanese Patent Application Laid-Open No. H5-40398, it is necessary to additionally arrange a deflection member in the optical path of image light in addition to the existing optical lens. There is a problem that causes an increase in cost.

Further, drum speed detection using a laser Doppler velocimeter disclosed in Japanese Patent Application Laid-Open No. 8-160829
Since it is a method using reflection of laser light, if the reflection surface is stained by toner or scratches due to sliding, etc.,
The detection signal drops out and becomes uncontrollable.
Further, when measuring the surface of the photosensitive drum, malfunction is likely to occur due to the low reflectance of the photosensitive drum itself.

SUMMARY OF THE INVENTION It is an object of the present invention to address the above-mentioned problems by optically correcting image light to be distributed to a photoreceptor by a liquid crystal lens. In this case, the optical axis can be deflected in the sub-scanning direction in accordance with the above, and a plurality of optical lenses can be replaced with a single liquid crystal lens, thereby realizing a reduction in size and cost of the apparatus. An exposure apparatus is provided.

Therefore, according to the present invention, in electrophotographic image formation, high resolution and high image quality of the photoconductor can be achieved by using a detecting means for detecting the movement error of the photoconductor by ultrasonic waves to achieve high precision and low cost. The challenge is to achieve the realization.

[0020]

According to an exposure apparatus of the present invention, an optical correction of a light beam emitted from a light source is applied to the light beam in the liquid crystal lens by a liquid crystal lens arranged in an optical path from a light source to a photosensitive member. In an exposure apparatus in which a first electrode and a second electrode that form a three-dimensional electric field distribution according to a power correction are to be irradiated, a light beam is applied between the first electrode and the second electrode. A voltage control unit for applying a voltage for deflecting the direction in the sub-scanning direction, and a detection unit for detecting the movement error of the photoconductor in the sub-scanning direction by ultrasonic waves, and Based on this, the power supply to the electrodes of the liquid crystal lens is controlled to deflect the light beam that scans the surface of the photoconductor in the main scanning direction in the sub-scanning direction.

3 corresponding to the optical correction to be applied to the light beam
By arranging the first electrode and the second electrode so as to form a two-dimensional electric field distribution, it is possible to apply a desired optical correction to the light beam to be distributed to the photoconductor by the liquid crystal lens.

By deflecting the irradiation direction of the light beam in the sub-scanning direction by applying a voltage between the first electrode and the second electrode, the time between the scanning timing of the light beam in the main scanning direction and the reference timing is reduced. Can be canceled out by the liquid crystal lens, and a predetermined resolution can be accurately maintained, thereby reliably preventing the occurrence of image density unevenness.

An error in the scanning timing of the light beam caused by a movement error of the photoconductor in the sub-scanning direction with respect to the reference timing is corrected by deflection of the irradiation direction of the light beam in the sub-scanning direction. Even if an error occurs in the movement in the scanning direction, the light beam that has passed through the liquid crystal lens can be applied to an appropriate position synchronized with the movement of the photoconductor, so that a predetermined resolution can be accurately maintained. It is possible to reliably prevent the occurrence of density unevenness in an image.

Since the moving speed of the photoreceptor of the image forming apparatus is determined by the detecting means using ultrasonic waves, the detecting means for detecting the moving speed of the photoreceptor on the observation surface of the photoreceptor may detect the toner contamination, sliding scratches and the like. It is possible to realize stable speed detection without being affected, and in electrophotographic image formation, by using a detection unit that detects a moving error of the photoconductor by ultrasonic waves, it is possible to increase the accuracy and cost of the photoconductor, thereby making it possible to reduce the sensitivity. High resolution and high image quality of the body can be realized.

In the exposure apparatus according to the present invention, a resistor in which one of the first electrode and the second electrode is continuously arranged around the light beam, and a plurality of resistors electrically connected to the resistor. And a bias connection part.

One of a first electrode and a second electrode formed to form a three-dimensional electric field distribution in the liquid crystal lens is
A ring-shaped electric field surrounding the light beam is formed in a smoothly continuous state by being electrically connected to the plurality of bias connection portions and being constituted by resistors arranged continuously around the light beam. Thus, desired optical correction can be applied to the light beam to be distributed to the photoreceptor by the liquid crystal lens.

An exposure apparatus according to the present invention has a configuration in which one of the first electrode and the second electrode is divided and arranged around a light beam.

By disposing one of the first electrode and the second electrode to be formed on the liquid crystal lens discontinuously at a plurality of positions around the light beam, one of the first electrode and the second electrode is formed. In this case, a resistor for connecting a plurality of bias connection portions can be omitted, and the manufacturing process of the liquid crystal lens can be simplified and the cost can be reduced.

The exposure apparatus according to the present invention is characterized in that one of the first electrode and the second electrode is formed into four parts, each of which is arranged in a single plane orthogonal to the light beam. The configuration has

One of the first electrode and the second electrode to be formed on the liquid crystal lens is divided into four portions in a single plane orthogonal to the light beam. Therefore, mutual interference between the divided electrodes is reduced, and a three-dimensional electric field distribution in the space between the first electrode and the second electrode arranged in the light beam passing direction is reliably formed. Further, since the plurality of divided electrodes are arranged on the same plane, it is easy to draw out the bias power supply line.

The exposure apparatus according to the present invention is characterized in that the liquid crystal lens is arranged in the optical path of the light beam together with the optical lens having a light beam condensing function.

A liquid crystal lens is arranged together with an optical lens having a condensing function in an optical path of a light beam from a light source to a photosensitive member. Therefore, the optical correction of the light beam emitted from the light source is shared and performed by the liquid crystal lens and the optical lens, and the burden of the optical correction on the liquid crystal lens is reduced.

In the exposure apparatus according to the present invention, the voltage control means determines the amount of deflection of the light beam in the sub-scanning direction based on the phase difference between the detection signal of the detection means and the reference signal, and realizes this amount of deflection. The power supply to the electrodes of the liquid crystal lens is controlled.

The amount of deflection of the light beam in the sub-scanning direction in the sub-scanning direction is determined based on the phase difference between the movement signal of the photoconductor in the sub-scanning direction and the reference signal. (Phase Loc
k Loop) control enables high-accuracy control.

The exposure apparatus according to the present invention has a configuration in which the detecting means detects the phase of the reflected sound.

Since the detecting means detects the moving speed of the photoreceptor by detecting the phase of the reflected sound, the detecting means can be constituted by a simpler circuit and can be realized at low cost without providing a complicated circuit or the like. it can.

The exposure apparatus according to the present invention has a constitution in which the detecting means detects the speed fluctuation of the photoconductor from the phase fluctuation of the reflected sound.

Since the detecting means detects the speed fluctuation of the photoconductor from the phase fluctuation of the reflected sound, the influence of the change in the sound speed due to the temperature and humidity can be reduced, and the reliability of the speed measurement value of the photoconductor is independent of the surrounding environment. Performance can be improved.

The exposure apparatus according to the present invention has a configuration in which the transmission signal from the detecting means is an intermittent pulse.

Since the signal transmitted from the detecting means is an intermittent pulse, the phase shift from the received signal can be easily recognized, and the device can be realized at low cost without providing a complicated circuit or the like.

The exposure apparatus according to the present invention has a configuration characterized in that the detection means applies a window (mask processing) to the received signal.

Window (mask processing) for received signal
Is applied, only the period permitted in the window can be used as an effective signal, the influence of the external noise of the received signal can be suppressed, and the speed measurement value of the photoconductor can be reliably measured without being affected by noise or the like. Can be enhanced.

The exposure apparatus according to the present invention has a structure in which the detecting means is installed at an angle with respect to the normal to the surface of the photosensitive member from which the surface speed is detected.

Since the detecting means can be installed at an angle from the normal line of the observation point on the surface of the photoreceptor, the degree of freedom in the location of the detecting means is increased, and the size of the image forming apparatus can be suppressed.

In the exposure apparatus according to the present invention, the positions of the transmitting source and the receiving source of the detecting means are set such that the angle from the vertical direction of the tangent to the surface of the photosensitive member at the reflection position of the photosensitive member is n, The angle between the tangent of the center of the body reflection position and θs is the angle between the center of the receiving source and the tangent of the center of the reflection position of the photoconductor.
When n ≦ θs ≦ n + 90, n ≦ θo ≦ n
+90 or n + 90 ≦ θs ≦ n + 180. The same quadrant is set such that n + 90 ≦ θo ≦ n + 180.

By arranging the transmitting source and the receiving source of the detecting means in the same quadrant, the Doppler effect appears remarkably at the receiving source, the accuracy of detecting the speed of the photosensitive member can be improved, and the size of the image forming apparatus can be increased. Can be suppressed.

The exposure apparatus of the present invention has a configuration in which the speed detection position of the photosensitive member is a rough surface.

Since the speed detection position of the photosensitive member may be a rough surface,
A portion other than the photosensitive surface can be used as a speed observation point, and thus the installation position of the detecting means can be installed at the longitudinal end of the photoconductor, so that the image forming apparatus can be suppressed from being enlarged, and inexpensive. Can be realized.

The exposure apparatus according to the present invention has a configuration characterized in that the transmitting element and the receiving element of the detecting means are shared.

By using both the transmitting element and the receiving element of the detecting means, the size of the detecting means can be reduced, thereby suppressing an increase in the size of the image forming apparatus and an increase in the number of parts.

[0051]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic diagram illustrating the operation of a liquid crystal lens in an exposure apparatus according to an embodiment of the present invention. According to the exposure apparatus of the present invention, the liquid crystal lens 4 disposed in the optical path from the light source to the photoconductor applies optical correction of the light beam emitted from the light source to the liquid crystal lens 4 according to the optical correction to be applied to the light beam. This is achieved by arranging a first electrode 46 and a second electrode 47 that form a two-dimensional electric field distribution.

When a voltage is applied between the first electrode 46 and the second electrode 47, a space between the first electrode 46 and the second electrode 47 is formed in the liquid crystal lens 4, as shown in FIG. , A three-dimensional electric field distribution is formed.

When a light beam is passed through the liquid crystal lens 4 in which a three-dimensional electric field distribution is formed, as shown in FIG. 1, the light path of the light beam is deflected according to the electric field distribution.

Therefore, by arranging the first electrode 46 and the second electrode 47 so as to form a three-dimensional electric field distribution according to the optical correction to be applied to the light beam, FIG.
As shown in (1), a desired optical correction is applied by the liquid crystal lens 4 to the light beam to be distributed to the photoconductor.

FIG. 2 is a schematic diagram showing a configuration of a main part of an image forming apparatus having an exposure apparatus according to an embodiment of the present invention. As shown in FIG. 2, the image forming apparatus rotatably includes a photosensitive drum 11, which is a photosensitive member having a photosensitive layer having a photoconductive function formed on a surface of a cylindrical substrate made of aluminum or the like. .

The photosensitive drum 11 has a drive motor 21
, Through a gear 13.

As shown in FIG. 2, the exposure apparatus 1 of the present invention deflects the light beam irradiation direction between the first electrode and the second electrode in the sub-scanning direction (the direction of arrow B in FIG. 2). A control circuit 22 serving as voltage control means for applying a voltage to be applied, and an ultrasonic sensor 9 serving as detection means for detecting the movement error of the photosensitive drum 11 in the sub-scanning direction B by ultrasonic waves. The power supply to the electrodes of the liquid crystal lens 4 is controlled based on the detection result of the ultrasonic sensor 9 to control the surface of the photosensitive drum 11 in the main scanning direction (arrow A in FIG. 2).
Direction) is deflected in the sub-scanning direction B.

The drive motor 21 is driven by a control circuit 22 having a waveform shaping circuit 23 and a phase difference detection circuit 24 based on the phase difference signal output from the phase difference detection circuit 24.

The phase difference detection circuit 24 includes a waveform shaping circuit 23
The phase difference between the rotation pulse Pm of the drive motor 21 output from the controller and the reference clock pulse Pref is obtained, and a signal corresponding to the phase difference is output.

The waveform shaping circuit 23 shapes a detection signal of an encoder (not shown) for detecting the rotation of the drive motor 21 into a rectangular wave and outputs it to the phase difference detection circuit 24.

Accordingly, the rotation of the drive motor 21 whose rotation is controlled at a constant speed based on the reference clock pulse by the control circuit 22 is transmitted to the photosensitive drum 11.

As shown in FIG. 2, the exposure apparatus 1 includes a semiconductor laser 2, an optical lens 3, a liquid crystal lens 4, a polygon mirror 5, a control circuit 6, a counting circuit 7, an ultrasonic sensor 9, and a synchronous detector 10. ing.

As shown in FIG. 2, the liquid crystal lens 4 is disposed in the optical path of the light beam together with the optical lens 3 having a light beam condensing function.

The exposure device 1 drives the semiconductor laser 2 based on image data, and uses the laser light emitted from the semiconductor laser 2 as image light via the optical lens 3, the liquid crystal lens 4, and the polygon mirror 5 to form a photosensitive drum. The light is distributed by scanning the surface 11 in the main scanning direction A.

The optical lens 3 performs focus correction among the optical corrections to be applied to the laser light in order to form the laser light emitted from the semiconductor laser 2 on the surface of the photosensitive drum 11.

In order to move the laser beam at a constant speed in the main scanning direction A with respect to the surface of the photosensitive drum 11, the liquid crystal lens 4 performs f−c of optical correction to be applied to the laser beam.
In addition to performing θ correction, deflection correction for moving the irradiation direction of the laser beam in the sub-scanning direction B is performed to cancel the rotation error of the photosensitive drum 11.

The exposure apparatus 1 scans the surface of the photosensitive drum 11 with image light in the main scanning direction A in synchronization with the rotation of the photosensitive drum 11 which rotates by receiving a rotational force from the drive motor 21. .

For this purpose, the exposure apparatus 1 has an ultrasonic sensor 9 and a synchronous detector 10.

The control circuit 22 determines the amount of deflection of the light beam in the sub-scanning direction B based on the phase difference between the detection signal of the ultrasonic sensor 9 and the reference signal, and controls the liquid crystal lens 4 to realize this amount of deflection. The power supply to the electrodes is controlled.

FIG. 3 is a schematic diagram showing the arrangement of the transmitter and the receiver of the ultrasonic sensor with respect to the photosensitive drum. The ultrasonic sensor 9 is, as shown in FIG.
And a receiver O as a receiving source, and the moving speed V of the photosensitive drum 11 is obtained as follows.

The transmitter S of the ultrasonic sensor 9 reflects the ultrasonic wave of the transmission wave fs to the observation surface of the photosensitive drum 11.

The receiver O of the ultrasonic sensor 9 receives the reflected wave from the observation surface of the photosensitive drum 11, and the received wave f
When the surface of the photosensitive drum 11, which is the observation surface, is moving (rotating) at the speed V, the frequency o is a frequency obtained by adding the Doppler effect to the transmission wave fs.

The general formula based on the Doppler effect is as follows. fo = {(C−Vo) / (C−Vs)} · fs Expression 1 s: sound source o: observer V: moving speed C: sound speed f:
From the above formula 1, when the transmission wave fs is reflected by the photosensitive drum 11, fo = {1 + V (cos θs + cos θo) / C} · f
s V = C (fo / fs−1) / (cos θs + cos θo) Expression 2 The general expression of the sound velocity C is as follows. C = 331.5 + 0.607 · T (m / s) Equation 3 T: ambient temperature (° C.) (at 15 ° C., C = 340 m / s)

Accordingly, the moving speed V of the photosensitive drum 11 can be obtained by detecting the reception wave fo by the above equations (2) and (3) and the receiver O.

In the above-mentioned method, the receiver O receives the received wave fo
Is detected, the moving speed V of the photosensitive drum 11 is recognized. A method of recognizing the moving speed V which is simpler and suppresses the error will be described below.

FIG. 4 shows a time chart of the transmission wave fs at the transmitter S and the reception wave fo at the receiver O. The reception wave fo is out of phase with the transmission wave fs by t1, t2 or t3. The phase shift is determined by the moving speed V of the photosensitive drum 11 in FIG.

Therefore, the receiver O of the ultrasonic sensor 9 detects the phase of the reception wave fo that is a reflected sound, and
If the speed fluctuation of the photosensitive drum 11 is detected from the phase fluctuation of the reflected sound between the transmission wave fs and the reception wave fo, the moving speed V of the photosensitive drum 11 can be recognized.

As described above, in order to easily detect the phase fluctuation between the transmission wave fs and the reception wave fo, as shown in FIG. 4, the transmission as the transmission signal from the transmitter S of the ultrasonic sensor 9 is performed. The wave fs may be an intermittent pulse.

As shown in FIG. 4, there is a possibility that noise may be mixed in the received wave fo. When this noise is detected, the phase difference between the transmitted wave fs and the received wave fo is erroneously recognized. I will.

Therefore, by providing a window signal as shown in FIG. 4 and detecting the phase difference between the logical product of the received wave fo and the wind signal and the transmitted wave fs, the ultrasonic sensor 9 applies the window ( (Mask processing), the effect of noise can be suppressed.

The synchronization detector 10 is a polygon mirror 5
The laser beam is detected at the scanning start position in the main scanning direction A of the laser beam deflected by the rotation of.

If the rotation speed of the photosensitive drum 11 is constant, the resolution of the image in the sub-scanning direction B is determined according to the time interval of the detection signal of the synchronous detector 10.

Therefore, the exposure apparatus 1 controls the rotation of the polygon mirror 5 and the driving of the semiconductor laser 2 so that the synchronous detector 10 detects the laser light at time intervals according to a preset resolution.

Thus, an electrostatic latent image having a predetermined resolution is formed on the surface of the photosensitive drum 11 by the photoconductive action of the photosensitive layer.

However, if an error occurs in the rotation speed of the photosensitive drum 11, the irradiation position of the laser light on the surface of the photosensitive drum 11 can be maintained even if the time interval for detecting the laser light by the synchronization detector 10 is kept constant. In the sub-scanning direction B, and the resolution of the image cannot be kept constant.

The exposure apparatus 1 uses the reference clock pulse Pre of the reference clock pulse generator 15 to determine the phase difference between the transmission wave fs and the reception wave fo at the transmitter S and the receiver O.
Recognized by the counting circuit 7 based on the window by f2, the voltage corresponding to the amount ΔV of the moving speed of the photosensitive drum 11 is calculated by
The voltage is applied between the first electrode and the second electrode of the liquid crystal lens 4 at a timing according to the detection signal of the synchronization detector 10.

As a result, when the laser light emitted from the semiconductor laser 2 passes through the liquid crystal lens 4, the irradiation direction is changed according to the rotation error of the photosensitive drum 11 in the sub-scanning direction B.
To offset the deviation of the irradiation position of the laser beam due to the rotation error of the photosensitive drum 11. As described above, the speed of the photosensitive drum 11 is detected by the ultrasonic wave.

Therefore, only a part of the transmission wave fs from the transmitter S shown in FIG. 3 which is irregularly reflected on the observation surface of the photosensitive drum 11 needs to be received by the receiver O as the reception wave fo. The transmitter S and the receiver O are arranged at an angle with respect to the normal to the surface of the photosensitive drum 11 whose surface speed is detected, so that the transmitter S and the receiver O There is no need to install on the line.

If the moving speed observation surface at which the speed of the photosensitive drum 11 is to be detected is a rough surface (the condition under which irregular reflection occurs is an uneven surface substantially equal to or greater than the reception wavelength), the transmission wave fs of the transmitter S is reduced. By being able to effectively diffuse light,
The installation positions of the transmitter S and the receiver O are accommodated in the same quadrant, so that the degree of freedom in selecting the moving speed observation surface of the photosensitive drum 11 is increased.

In order to more effectively observe the moving speed V of the photosensitive drum 11 by the transmitter S and the receiver O of the ultrasonic sensor 9, the installation position of the transmitter S and the receiver O of the ultrasonic sensor 9 is required. Is the same quadrant as shown in Equations 4 and 5 below, the received wave fo with respect to the transmitted wave fs can be received with high sensitivity. When n ≦ θs ≦ n + 90, n ≦ θo ≦ n + 90 (Equation 4) or when n + 90 ≦ θs ≦ n + 180, n + 90 ≦ θo ≦ n + 180 (Equation 5) n: The photosensitive drum 1 at the reflection position center of the photosensitive drum 11
The angle from the vertical direction of the tangent of one surface θs: The angle between the center of the transmitter S and the tangent of the center of the reflection position of the photosensitive drum 11 θo: The tangent of the center of the receiver O and the center of the reflection position of the photosensitive drum 11 Angle made with

As a method for most effectively realizing the above formulas 4 and 5, the transmitter S and the receiver O of the ultrasonic sensor 9 are integrated, or the transmitting element (transmitting element) of the detecting means.
By using a transceiver that also serves as a receiver and a receiving element, it is possible to receive the reception wave fo with respect to the transmission wave fs with high sensitivity.

For example, when the rotation of the photosensitive drum 11 is delayed, the irradiation position of the light beam is deflected to the upstream side in the sub-scanning direction B on the surface of the photosensitive drum 11, and the rotation of the photosensitive drum 11 becomes faster. In this case, the irradiation position of the light beam is deflected to the downstream side in the sub-scanning direction B on the surface of the photosensitive drum 11. In this manner, the liquid crystal lens 4 corrects the deflection of the laser beam according to the rotation error of the photosensitive drum 11.

FIG. 5 is an exploded perspective view showing the structure of a liquid crystal lens provided in the exposure apparatus. As shown in FIG. 5, the liquid crystal lens 4 includes flat glass plates 4a, 4b and electrodes 41,
48 and the liquid crystal 4c.

In the liquid crystal lens 4, two flat glass plates 4a and 4b, which are flat translucent supports having electrodes 41 and 48 formed on the surfaces facing each other, are arranged at a predetermined interval.
A liquid crystal 4c is filled between the two flat glass plates 4a and 4b.

One or both of the translucent supports may be formed in a three-dimensionally formed non-flat shape.
By using a and 4b, the liquid crystal lens 4 can be manufactured inexpensively and easily.

FIGS. 6A and 6B are diagrams showing a first example of the shape of the electrodes of the liquid crystal lens, wherein FIG. 6A is a sectional side view of a main part of the liquid crystal lens, and FIG. 6B is a line aa of FIG. Arrow view, (C)
FIG. 3 is a view taken along line bb in FIG. In this example, FIG.
As shown in FIGS. 2A and 2B, of the two flat glasses 4a and 4b constituting the liquid crystal lens 4, the upper and lower surfaces on the inner surface of one flat glass 4a facing the optical lens 3 in the configuration of FIG. Parallel linear electrodes 41 near the ends
a, 41b are formed, and as shown in FIG. 6 (C), parallel linear electrodes 4 are formed near the left and right ends on the inner surface of the other flat glass 4b which also faces the polygon mirror 5.
2a and 42b are formed. Note that the laser light passes through substantially the center of the flat glass 4a, 4b.

As shown in FIG. 6B, a vertical bias potential Ey is applied to the electrode 41a via the control circuit 22.
Is applied to the electrode 42a via the control circuit 22 as shown in FIG. 6C.
Is applied.

By applying these potentials, the electric field distribution in the space between the electrodes 41a and 41b and the electric field distribution in the liquid crystal 4c filled between the two flat glass plates 4a and 4b.
An electric field distribution in the space between the electrode and the electrode 42b, that is, a three-dimensional electric field distribution is formed.

As a result, the lines of electric force are indicated by broken lines in FIG. 1, and the direction of irradiation of the laser beam passing through the liquid crystal lens 4 in the vertical direction, that is, by the electric field distribution in the space between the electrodes 41a and 41b, ie, The light is deflected in the sub-scanning direction B.

The direction of irradiation of the laser beam passing through the liquid crystal lens 4 is deflected in the left-right direction, that is, in the main scanning direction A, due to the electric field distribution in the space between the electrodes 42a and 42b.

Accordingly, the electrodes 41a and 41b perform deflection correction for canceling the irradiation position error due to the rotation unevenness of the photosensitive drum 11, and also perform the electrodes 42a and 4b.
By 2b, f-θ correction for deflecting the laser beam at a constant speed on the surface of the photosensitive drum 11 is performed.

FIGS. 7A and 7B are diagrams showing a second example of the shape of the electrodes of the liquid crystal lens. FIG. 7A is a side sectional view of the liquid crystal lens, and FIG. 7B is a view taken along line aa of FIG. FIG. 7C is a view taken along line bb in FIG. The first electrode is shown in FIG.
As shown in FIG. 2B, an annular resistor 42 continuously arranged around the light beam, and electrodes 43a and 43 electrically connected to the resistor 42 and serving as a plurality of bias connection portions.
b, 43c and 43d.

In this example, as shown in FIGS. 7 (A) and 7 (B), electrodes 43 are provided at four places, namely, the center of the upper and lower sides and the center of the left and right sides inside the flat glass 4a facing the optical lens 3.
a, 43b, 43c, 43d, and an annular resistor 42 connecting these electrodes 43a, 43b, 43c, 43d, and a flat plate facing the polygon mirror 5, as shown in FIG. Resistor 4 on the inner surface of glass 4b
2 are formed.

As shown in FIG. 7B, a vertical bias potential Ey1 is applied to the electrode 43a.
A vertical bias potential Ey2 is applied to 3b, a horizontal bias potential Ex1 is applied to the electrode 43c, and a horizontal bias potential Ex2 is applied to the electrode 43d.

By applying these bias potentials, 2
In the liquid crystal 4c filled between the flat glass plates 4a and 4b, a three-dimensional electric field distribution is formed in the space between the resistor 42 and the electrode 44.

As a result, the electrodes 43a, 43b, 43
bias potentials Ey1, Ey2, E applied to c and 43d
By appropriately controlling x1 and Ex2, deflection correction for canceling the error of the irradiation position due to the rotation unevenness of the photoconductor drum 11 is performed, and the laser beam for deflecting the laser beam at a constant speed on the surface of the photoconductor drum 11 is performed. f-θ correction is performed.

Further, since the lines of electric force are continuously formed around the laser beam, a smooth electric field distribution can be obtained, and optical correction other than deflection correction and f-θ correction can be performed. .

FIGS. 8A and 8B are diagrams showing a third example of the shape of the electrodes of the liquid crystal lens. FIG. 8A is a side sectional view of the liquid crystal lens, and FIG. 8B is a view taken along line aa of FIG. FIG. 7C is a view taken along line bb in FIG. Electrodes 45a, 45b, 45c, and 45d serving as first electrodes are divided and arranged around the light beam. Also, the electrodes 45a, 45b, 4
5c and 45d are configured into four parts, each of which is arranged in a single plane orthogonal to the light beam.

In this example, as shown in FIGS. 8A and 8B, linear electrodes 4 are provided at four locations near the upper and lower ends and near the left and right edges of the inner surface of the flat glass 4a facing the optical lens 3.
8A, 5a, 45b, 45c and 45d are formed, and as shown in FIG.
An annular electrode 44 partially facing the electrodes 45a, 45b, 45c, 45d is formed on the inner side surface of b.

As shown in FIG. 8B, a vertical bias potential Ey1 is applied to the electrode 45a.
A vertical bias potential Ey2 is applied to 5b, a horizontal bias potential Ex1 is applied to the electrode 45c, and a horizontal bias potential Ex2 is applied to the electrode 45d.

As described above, the electrodes 45 formed at four equally spaced locations on the inner side surface of one flat glass 4a.
a, 45b, 45c, 45d by applying
Liquid crystal 4c filled between two flat glasses 4a and 4b
Inside, electrodes 45a, 45b, 45c, 45d and electrode 4
A three-dimensional electric field distribution is formed by the electric charge distribution in the space 4.

As a result, the electrodes 45a, 45b, 45
bias potentials Ey1, Ey2, E applied to c, 45d
By appropriately suppressing x1 and Ex2, deflection correction for canceling the error of the irradiation position due to the rotation unevenness of the photoconductor drum 11 is performed, and the laser beam is deflected on the surface of the photoconductor drum 11 at a constant speed. f-θ correction is performed.

Further, since the electrodes 44 are continuously formed in an annular shape, the electrodes 45a, 45b, 45c, 45d
The lines of electric force are formed continuously around the laser beam without forming an annular resistor electrically connected to the laser beam, and a substantially smooth electric field distribution can be obtained, and the manufacturing process can be simplified. .

Further, the electrodes 45a, 45b, 45c, 4
5d are formed at four equally-spaced portions orthogonal to each other on the inner surface of the flat glass 4a, so that mutual electrical interference is minimized, and the electrodes 45a, 45b, 45
The electric field distribution in the space between each of the electrodes c and 45d and the electrode 44 can be reliably formed.

In addition, the electrodes 45a, 45b, 45c, 4
Since 5d is formed on a single surface, the electrodes 45a and 45d
The process of extracting the bias voltage for b, 45c, and 45d can be easily performed.

[0116]

As described above, according to the exposure apparatus of the present invention, the optical correction of the image light to be distributed to the photoreceptor by the liquid crystal lens, particularly, the uniform velocity deflection on the surface of the photoreceptor and the photoreceptor The optical axis can be deflected in the sub-scanning direction according to the rotation unevenness, and by replacing a plurality of optical lenses with a single liquid crystal lens, it is possible to reduce the size and cost of the apparatus. it can.

Further, according to the present invention, in the electrophotographic image formation, a high-resolution and high-quality photoconductor can be achieved by using a detecting means for detecting a moving error of the photoconductor by ultrasonic waves to achieve high precision and low cost. Can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating the operation of a liquid crystal lens in an exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a configuration of a main part of an image forming apparatus having an exposure device according to an embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating an arrangement of a transmitter and a receiver of the ultrasonic sensor with respect to a photosensitive drum.

FIG. 4 is a time chart showing a transmission wave in a transmitter and a reception wave in a receiver.

FIG. 5 is an exploded perspective view showing a configuration of a liquid crystal lens provided in the exposure apparatus.

FIG. 6 is a diagram showing a first example of the shape of an electrode of a liquid crystal lens.

FIG. 7 is a diagram showing a second example of the shape of the electrode of the liquid crystal lens.

FIG. 8 is a diagram showing a third example of the shape of the electrode of the liquid crystal lens.

[Explanation of Symbols] 1 Exposure device 2 Semiconductor laser (light source) 3 Optical lens 4 Liquid crystal lens 4a, 4b Flat glass 4c Liquid crystal 5 Polygon mirror 6 Control circuit 7 Counting circuit 9 Ultrasonic sensor 10 Synchronous detector 11 Photoconductor drum 13 Gear 15 Reference Clock Pulse Generator 21 Drive Motor 22 Control Circuit 23 Waveform Shaping Circuit 24 Phase Difference Detection Circuit 41 Electrode 42 Resistor 41a, 41b Electrode 42a, 42b Electrode 43a, 43b, 43c, 43d Electrode 44 Electrode 45a, 45b, 45c, 45d electrode 46 first electrode 47 second electrode 48 electrode

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/04 G03G 15/04 120 15/043 21/00 372 21/14 (72) Inventor Mori Morita Osaka (22) Inventor, Keisuke Hara 22-22, Nagaike-cho, Abeno-ku, Osaka City, Osaka Inside Sharp Co., Ltd. (72) Inventor Akira Nakakuma, Osaka City, Osaka, Osaka 22-22 Nagaikecho, Abeno-ku, Sharp Corporation (72) Inventor Hiroshi Ishii 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka F-term (reference) 2C362 BA83 BA84 BA89 BB46 BB48 CB60 2H027 DA01 DA32 DE02 DE04 DE07 DE09 EB01 EC06 ED02 ED04 ED06 EE01 EE07 EF09 ZA07 2H045 AA01 CA01 CA02 CA61 DA02 2H076 AB05 AB12 AB16 AB18 AB22 AB32 AB67 AB68 DA41 EA14 2H087 KA19 LA27 NA01 RA2 1 RA28 RA45 UA09

Claims (14)

[Claims] 1. A three-dimensional electric field distribution according to an optical correction to apply an optical correction of a light beam emitted from a light source to a light beam in a liquid crystal lens by a liquid crystal lens disposed in an optical path from a light source to a photosensitive member. Forming a first electrode and a second electrode
An exposure apparatus that is provided by disposing the above-mentioned electrodes includes voltage control means for applying a voltage between the first electrode and the second electrode to deflect the irradiation direction of the light beam in the sub-scanning direction. The control means includes a detecting means for detecting a moving error of the photoconductor in the sub-scanning direction by ultrasonic waves, and controls a power supply to an electrode of a liquid crystal lens based on a detection result of the detecting means to move the surface of the photoconductor in the main scanning direction. An exposure apparatus for deflecting a light beam to be scanned in a sub-scanning direction. 2. A resistor in which one of the first electrode and the second electrode is continuously arranged around a light beam, and a plurality of bias connection portions electrically connected to the resistor. The exposure apparatus according to claim 1, further comprising: 3. The exposure apparatus according to claim 1, wherein one of the first electrode and the second electrode is divided and arranged around a light beam. 4. The method according to claim 3, wherein one of the first electrode and the second electrode is divided into four parts, each of which is arranged in a single plane orthogonal to the light beam. Exposure apparatus according to the above. 5. The exposure apparatus according to claim 1, wherein the liquid crystal lens is arranged in an optical path of the light beam together with an optical lens having a light beam condensing function. 6. The liquid crystal lens according to claim 6, wherein said voltage control means determines a deflection amount of the light beam in the sub-scanning direction based on a phase difference between a detection signal of the detection means and a reference signal. The exposure apparatus according to claim 1, wherein power supply to the exposure device is controlled. 7. An exposure apparatus according to claim 1, wherein said detecting means detects a phase of a reflected sound. 8. An exposure apparatus according to claim 1, wherein said detecting means detects a speed variation of the photoconductor from a phase variation of a reflected sound. 9. An exposure apparatus according to claim 1, wherein the transmission signal from said detection means is an intermittent pulse. 10. An exposure apparatus according to claim 1, wherein said detection means applies a window to the received signal. 11. The exposure apparatus according to claim 1, wherein the detection unit is installed at an angle with respect to a normal to the surface of the photoreceptor whose surface speed is detected. 12. An installation position of a transmission source and a reception source of the detection means, where n is an angle from a vertical direction of a tangent to a surface of the photoreceptor at a reflection position center of the photoreceptor; When the angle between the center tangent and the tangent at the center of the receiving source and the reflection position of the photosensitive member is θo, when n ≦ θs ≦ n + 90, n ≦ θo ≦ n + 90 or n + 90 ≦ When θs ≦ n + 180, n + 90 ≦ θo ≦
2. The same quadrant as n + 180.
3. The exposure apparatus according to claim 1. 13. The exposure apparatus according to claim 1, wherein the speed detection position of the photoconductor is a rough surface. 14. An exposure apparatus according to claim 1, wherein said detecting means serves as both a transmitting element and a receiving element.