JPH0695025A - Image exposure device - Google Patents

Abstract

(57) [Abstract] [Purpose] It is an object of the present invention to provide an image exposure apparatus capable of exposing a high-quality image without uneven exposure due to uneven rotation of a rotating drum. A speed detection device for detecting a moving speed of a photoconductor, a speed conversion circuit for converting a speed error of a detected speed into an error signal of a position of the photoconductor, and a speed conversion circuit arranged in an optical path of a light beam, It is composed of a mirror or the like whose reflection angle can be changed by an actuator driven by a position error signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image exposure apparatus,
More specifically, the present invention relates to an image exposure apparatus that reduces exposure unevenness due to speed unevenness in sub-scanning.

[0002]

2. Description of the Related Art Conventionally, in this type of image exposure apparatus, a modulated light beam is deflected and scanned by a rotating polygon mirror, and an image is formed by sequentially exposing a rotating drum around which photosensitive paper is wound.

[0003]

However, in the above-described exposure apparatus, the exposure amount of the light beam becomes uneven due to uneven rotation due to tooth contact of the reduction gear that drives the rotating drum, and the image to be output is uneven. Density unevenness occurred and the image quality was degraded. In particular, when forming a color image by superimposing the number of colors, there is a problem in that the color becomes uneven and it is very unsightly.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an image exposure apparatus capable of exposing a high quality image regardless of the uneven rotation of the rotary drum. I am trying.

[0005]

In order to achieve this object, an image exposure apparatus described in claim 1 deflects and scans a light beam modulated by an image signal, and sequentially exposes a moving photoconductor. As a result, in an image exposure device that exposes an image, a speed detection device that detects the moving speed of the photoconductor, a speed conversion circuit that converts a speed error of the detected speed into an error signal of the position of the photoconductor, and an optical And an optical path changing means arranged in the optical path of the beam for changing the optical path of the light beam based on the position error signal, and changing the reflection angle of the mirror by the position error signal output from the speed conversion circuit. Reduce uneven exposure due to uneven speed of the photosensitive member.

An image exposure apparatus according to a second aspect is an image exposure apparatus which exposes an image by deflecting and scanning a light beam modulated by an image signal and sequentially exposing the moving photoconductor. A position detection device that detects the position of the moving photoconductor, a position conversion circuit that converts the detected position into an error signal of the position of the photoconductor, and a position conversion circuit that is arranged in the optical path of the light beam and that is based on the position error signal. And an optical path changing means for changing the optical path of the light beam, and changes the optical path of the light beam according to the position error signal output from the position conversion circuit to reduce uneven exposure due to uneven speed of the photoconductor.

[0007]

The image exposure apparatus having the above construction operates as described below.

The light beam modulated by the image signal is deflected and scanned to sequentially expose the rotating photoconductor.

The speed detecting device detects the rotational speed of the photoconductor with high accuracy. The speed conversion circuit integrates the detected rotation speed, converts it into position information of the photoconductor, and further outputs the error signal in comparison with the position when rotating at a predetermined rotation speed.

The optical path changing means arranged in the optical path of the light beam is constructed so that the optical path of the light beam can be varied based on the error signal, and the exposure position of the light beam irradiated by the error signal varies in speed. Change according to.

Further, according to the image exposure apparatus having the above structure, the optical path of the light beam is changed on the basis of the signal from the position detecting device for detecting the position of the photoconductor to expose the photoconductor. To do.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing the configuration of the entire image exposure apparatus of this embodiment. The configuration will be described with reference to FIG.

The laser light device 1 generates a laser beam according to an image signal input from the outside, and is composed of a semiconductor laser, a drive circuit, a collimator lens and the like.

The scanning device 2 is composed of a rotary polygon mirror and a motor, and scans and deflects the laser beam generated by the laser light device 1.

The f-θ lens 3 is a lens for converting a laser beam scan into a constant velocity scan.

The motor device 4 is composed of a motor and a servo circuit, and the motor is configured to rotate at a predetermined constant speed by the servo circuit.

The speed reducer 5 is composed of a plurality of gears and reduces the rotation of the motor of the motor device 4.

The rotary drum 6 is connected to the speed reducer 5 and rotates at a predetermined constant speed in the direction of arrow A in the figure.

The photosensitive paper 7 is wound around the surface of the rotary drum 6 and is processed by irradiation with a laser beam to form an image. The photoconductor is constructed.

The speed generator 8 is connected to the rotary shaft of the rotary drum 6 and detects the speed of the rotary drum 6 with high accuracy.
Output as a speed signal.

The speed conversion circuit 9 is, as shown in FIG.
This is a circuit composed of a subtraction circuit 91 and an integration circuit 92, which subtracts the speed signal of the speed generator 8 from the reference voltage, then integrates it and converts it into an error signal of the position of the rotary drum 6.

The actuator 10 minutely displaces the angle in accordance with the signal from the speed conversion circuit 9. The reflection mirror 11 is arranged in the optical path of the laser beam and is connected to the actuator 10. The reflection angle of the reflection mirror 11 is controlled by the actuator 10. These constitute the optical path changing means of the present invention.

Next, the operation of the image exposure apparatus having the above structure will be described with reference to FIGS.

The laser beam device 1 generates a laser beam, for example, pulse width modulated according to an image signal input from the outside.

The scanning device 2 scans and deflects the laser beam. The deflected laser beam is converted into a constant-velocity scan by the f-θ lens 3 and, via the reflection mirror 11, the photosensitive paper 7 wound around the surface of the rotary drum 6 is repeatedly exposed.

On the other hand, the rotational output of the motor device 4 is decelerated by the speed reducer 5 to drive the rotary drum 6 to rotate. The rotary drum 6 is rotationally driven at a predetermined constant number of rotations, but due to the tooth contact of the gears forming the reduction gear 5, the rotary drum 6 rotates including a slight speed unevenness.

The speed generator 8 is connected to the rotary shaft of the rotary drum 6 and detects the speed of the rotary drum 6. Since the speed generator 8 is configured with sufficiently high accuracy, the rotation speed of the rotary drum 6 is detected including the minute speed unevenness described above.

The speed conversion circuit 9 converts the detected speed signal into a position error signal. That is, the subtraction circuit 91 converts the speed signal into a speed error signal, and the integration circuit 92 converts the speed error signal into a position error signal of the photosensitive drum 6. If the speed is fast, it is converted into a positive polarity position error signal, and if the speed is slow, it is converted into a negative polarity position error signal.

The actuator 10 changes the reflection angle of the reflection mirror 11 according to the position error signal of the speed conversion circuit 9. If the position error signal is positive, in the direction of arrow B in FIG.
If it is negative, the position of the reflection mirror 11 is changed in the direction of arrow C. The magnitude of the change is proportional to the magnitude of the position error signal.

FIG. 4 shows how the reflection angle of the reflection mirror 11 changes. That is, if the position error signal is positive and positive, the rotation of the rotary drum 6 is fast and the position to be exposed is on the right side. Therefore, the reflection mirror 11 is changed in the direction of arrow B to perform exposure, and the exposure position is adjusted. If the position error signal has a negative polarity, the rotation of the rotary drum 6 is slow and the position to be exposed is on the left side.
The exposure position is adjusted by changing the direction of exposure.

In the conventional image exposure apparatus, when the speed is uneven, the exposure is performed as shown in FIG. That is, when the rotation speed of the rotary drum 6 is high, a gap is formed in the exposure trajectory of the laser beam on the photosensitive paper 7 as shown in FIG. 3A, and conversely, when the rotation speed is low, FIG. As shown in (b), the exposure loci of the laser beams overlap.

According to the image exposure apparatus of this embodiment, the slow rotation speed of the rotary drum 6 is corrected by the reflection mirror 11 and the exposure is correctly performed as shown in FIG. 3 (c).

Further, since the reflection mirror 11 is located far away from the radius of the rotating drum 6 and the displacement amount is small, the degree of deformation of the laser beam is small,
It doesn't matter.

The present invention is not limited to the embodiments described in detail above, and various modifications and improvements are possible.

For example, the position of the reflection mirror may be between the laser beam device and the scanning device, not between the f-θ lens and the rotating drum. The configuration in this case is shown in FIG.
Further, FIG. 6 shows how the rotary drum is irradiated with the laser beam in this case.

In the embodiment described above, the position error is detected from the rotational speed in order to detect the position error of the moving photosensitive member. However, the position detecting device is provided to detect the position error of the moving photosensitive member. A position error may be detected from the rotational position. The position detecting device may be a device including a known rotary encoder, and the position error converting circuit converts the position of the rotary drum detected by the position detecting device into a position error signal, and controls the reflecting mirror 11 based on the signal. The position error conversion circuit is a circuit that detects the position error signal by comparing the phase of the pulse signal from the rotary encoder with the reference pulse signal.

[0038]

As is apparent from the above description, the image exposure apparatus of the present invention converts the rotational speed unevenness of the rotary drum detected by the speed detection apparatus into the position error signal by the conversion circuit, and the position error signal is converted. Since the reflection angle of the reflection mirror is changed and corrected by the actuator according to the signal, it is possible to provide an image exposure apparatus capable of high quality exposure without exposure unevenness.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of an image exposure apparatus of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a conversion circuit.

FIG. 3 is an explanatory diagram showing a state of exposure.

FIG. 4 is a cross-sectional view showing how the exposure position of a laser beam is corrected.

FIG. 5 is a configuration diagram showing another configuration of the image exposure apparatus of the present invention.

6 is a cross-sectional view showing how the exposure position of the laser beam is corrected in the configuration of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Laser device 2 Scanning device 3 f-theta lens 4 Motor device 5 Reduction gear device 6 Rotating drum 7 Photosensitive paper 8 Speed generator 9 Conversion circuit 10 Actuator 11 Reflection mirror

Claims (2)

[Claims] 1. A speed detecting device for detecting a moving speed of a photosensitive member in an image exposing device for deflecting and scanning a light beam modulated by an image signal to sequentially expose a moving photosensitive member to expose an image. A speed conversion circuit for converting the speed error of the detected speed into an error signal of the position of the photoconductor, and disposed in the optical path of the light beam,
An optical path changing means for changing the optical path of the light beam based on the position error signal, and changing the reflection angle of the mirror by the position error signal output by the speed conversion circuit to cause uneven exposure of the photosensitive member due to speed unevenness. An image exposure apparatus characterized by reducing 2. An image exposure apparatus that exposes an image by deflecting and scanning a light beam modulated by an image signal to sequentially expose a moving photoconductor, and a position detection device for detecting the position of the moving photoconductor. A position conversion circuit for converting the detected position into an error signal of the position of the photoconductor, and an optical path changing means arranged in the optical path of the light beam for changing the optical path of the light beam based on the position error signal. And an image exposure apparatus which reduces exposure unevenness due to speed unevenness of a photoconductor by changing an optical path of a light beam according to a position error signal output from a position conversion circuit.