JPH01180513A - Light beam recorder - Google Patents

Abstract

PURPOSE:To equalize a main scanning line pitch to a recording material by detecting a relative angle of a rotating body and a reflecting mirror, correcting the quantity of electricity to a piezoelectric element, based on said angle and correcting an angle error against a hysteresis of the piezoelectric element. CONSTITUTION:When a polygon mirror 22 becomes immediately before a start of a main scan, a reference light beam is radiated from a light source 60. The reference light beam is reflected by a reflection mirror 46, reaches a photodetecting sensor 62, and by a light receiving position of its sensor part 62A, a different correcting signal is supplied to a control part 16. In the control part 16, an inclination quantity of the reflection mirror 46 is calculated, based on said correcting signal, and in accordance with a resut of this calculation, a prescribed voltage is applied to the corresponding piezoelectric element 48. The piezoelectric element 48 to which the prescribed voltage has been applied inclines the reflection mirror 46, and by executing it at every reflection mirror 46, a deflection of a light beam caused by eccentricity of a rotation axis 52, etc., can be obviated. In such a way, a main scanning line pitch can be held uniformly.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a light beam recording device, and in particular, the present invention relates to a light beam recording device that records light beams by a rotating polygon mirror including a rotating body and a plurality of reflecting surfaces parallel to the rotation axis of the rotating body. The present invention relates to a light beam recording device that records an image on a recording medium using a light beam.

[Prior Art] Generally, in a light beam recording device, the direction of irradiation of the recording light beam from a laser is continuously deflected by a scanning optical system composed of a rotating polygon mirror, etc. . That is, the angle of incidence of the recording light beam on the polygon mirror is changed by the rotation of the polygon mirror, thereby deflecting the direction of reflection. The light beam reflected by the polygon mirror is irradiated onto a recording medium placed on a fixed recording stage, and an image is recorded.

This recording medium is one in which the recording layer of the irradiated area changes, for example, by melting or evaporating, and its transmittance changes.Like conventional silver halide photosensitive materials, an image is recorded and then developed. It is possible to confirm the recorded state at the same time as writing (light beam irradiation) without doing the above (see Japanese Patent Application Laid-Open No. 153025/1983).

However, in such a structure, the accuracy of the reflective surface of the polygon mirror is greatly affected by the main scanning line pitch, and if so-called surface tilt occurs, the pitch of the main scanning lines recorded on the recording material becomes uneven, and the image This will cause a disturbance. Furthermore, since the polygon mirror is mechanically rotated, the tilting of the reflecting surface due to dimensional errors in the rotation drive system or wear over time also causes the surface to tilt.

In order to solve this problem, it has been proposed to correct the light beam reflected by the reflecting surfaces using an optical system so that the trajectories of the scanning lines from each reflecting surface of the polygon mirror match (face tilt correction) -28666, Utility Model 53
(Refer to Publication No.-91845). In addition, when implementing the technology described in the above-mentioned publication, a short focal length lens that requires high quality and is difficult to manufacture is necessarily required. It is disclosed that a long focal length cylindrical lens can be used. According to these publications, an optical system is interposed between the polygon mirror and the recording material to eliminate the surface tilt.

[Problems to be Solved by the Invention] However, for the above-mentioned surface tilt correction, an optical system is interposed between the polygon mirror and the recording material, and high precision is required when installing this optical system. There are problems in that it is troublesome and requires a large number of parts, making the device itself large.

In consideration of the above facts, the present invention does not require an optical system for surface tilt correction, and can make the scanning trajectories of the light beams by each reflecting surface of the polygon mirror coincide with each other, thereby adjusting the main scanning line pitch to the recording material. It is an object of the present invention to obtain a light beam recording device that can make the light beam uniform.

[Means for Solving the Problems] A light beam recording device according to the present invention includes a piezoelectric element disposed between a rotating body and a plurality of reflecting mirrors attached to the circumferential surface of the rotating body, and Control that controls the amount of electricity supplied to the element, changes the relative angle between the rotating body and the reflecting mirror, and matches the main scanning trajectory of the image recording light beam sequentially reflected from each reflecting mirror according to the rotation of the rotating body. A light beam recording device comprising: an angle detection means for detecting a relative angle between the rotating body and the reflecting mirror; and an angle detection means for correcting the amount of electricity applied to the piezoelectric element based on the angle detected by the angle detection means. and a correction means for correcting an angular error due to hysteresis of the piezoelectric element.

[The action control means controls the amount of electricity supplied to the piezoelectric element to change the relative angle between the rotating body and the reflecting mirror, so that the image recording light beam is sequentially reflected from each reflecting mirror according to the rotation of the rotating body. Match the main scanning trajectories.

As a result, the reflecting mirror is positioned at a predetermined position, and main scanning is performed in this state. By positioning this reflecting mirror to a predetermined position every time immediately before the scanning of each reflecting mirror starts, the scanning trajectories of the plurality of reflecting mirrors are all matched, and for example, when the recording medium is moved at a constant speed in the sub-scanning direction, When an image is recorded using this light beam, the main scanning line pitch is uniform and no unevenness occurs in the image. Further, an optical system for correcting scanning line pitch deviation between the reflecting mirror and the recording medium is not required, and the number of parts is reduced.

By the way, as the material for the piezoelectric element, a group of piezoelectric substances that are resistant to mechanical operation, such as barium titanate and its similar PZT (lead titanium zirconate), can be applied, but the characteristics of these piezoelectric elements As such, it has quite a bit of hysteresis.

In the present invention, when positioning a reflecting mirror using piezoelectric elements, an angle detecting means is installed near each piezoelectric element, and the relative angle between the rotating body and the reflecting mirror is detected by this angle detecting means. The correction means corrects the hysteresis of the piezoelectric element based on this measurement angle. In other words, when the same amount of electricity is applied to the piezoelectric element, the position where the reflector is positioned when it changes direction from bottom to top is made to match the position where it is positioned when it changes direction from top to bottom. That's what I do. Thereby, the positioning of the reflecting mirror by the control means can be performed with high precision.

Embodiment FIG. 1 shows a schematic diagram of a light beam recording apparatus 10 according to this embodiment. In this embodiment, two lasers for light beam irradiation are provided, one of which is used as the writing laser 12 and the other as the reading laser 14. These lasers 12 and 14 are arranged in parallel, and are irradiated with a light beam (indicated by a dashed line in FIG. 1) in response to a signal from the control section 16. The writing light beam irradiated from the writing laser 12 is supplied to the optical modulator 18, passes through the gicroic mirror 20, and is irradiated onto the polygon mirror 22. On the other hand, the light beam for reading is mirror 2.
4, the light beam is reflected in the direction of the guichroic mirror 20, and the optical axis is made to coincide with the writing light beam by the guichroic mirror 20. Therefore, the polygon mirror 22 is irradiated with a composite light beam in which the writing light beam and the reading light beam are combined.

The polygon mirror 22 is composed of a rotating polygon mirror, and has the function of continuously changing the incident angle of the combined light beam incident within a predetermined angle range by rotating the polygon mirror 22. This polygon mirror 22 is controlled and rotated by a control signal from the control section 16.

The combined light beam reflected from the polygon mirror 22 is converged by a converging optical system 26.28, which together with the polygon mirror 22 constitutes a part of the scanning optical system, and the reading light beam is directed upstream of a recording medium 36, which will be described later. The pulse signal is detected by the arranged photodetection sensor 30 and supplied to the control section 16. The photodetection sensor 30 is disposed corresponding to a position immediately before the start of main scanning by the writing light beam, and is configured to obtain the timing at which irradiation of the writing light beam starts.

The control unit 16 includes a microcomputer (not shown), and starts irradiation of the writing light beam after a predetermined period of time in response to a pulse signal from the photodetection sensor 30, and controls image recording on the recording medium 36. I have to.

the writing light beam is coaxial with the reading light beam;
A roll-shaped recording medium 36 placed on the recording stage 40
Main scanning is performed by irradiating the recording surface onto the recording surface. The recording stage 40 is moved toward the back of the paper in FIG. is now sub-scanned.

In this embodiment, the recording medium 36 is a roll-shaped film, but it may be a so-called microfiche in which a plurality of images are recorded on the sheet-shaped recording medium 36.

FIG. 2 shows a perspective view of the polygon mirror 22, which is a feature of the present invention, and its related parts.

The polygon mirror 22 is composed of a polygonal rotating body 44 and a plurality of reflecting mirrors 46 arranged on the corner surfaces of the polygonal rotating body 44, and when the rotating body 440 rotates, the writing light beam and the reading light beam are reflected. Main scanning is performed by changing the incident angle to 46. This polygon mirror 22 is
It is rotated by the driving force of a motor (not shown).

By the way, in the polygon mirror 22 according to this embodiment, as shown in FIG. 3, piezoelectric elements 48 are interposed between the rotating body 44 and each reflecting mirror 46. These piezoelectric elements 48 are connected to lead wires 50A, 50B, respectively.
are electrically connected to rotation terminals 54A, 54B, . . . attached along the circumferential surface of the rotation shaft 52. A cap 56 is pivotally attached to the rotating shaft 52, and this cap 5
Fixed terminal (brush) penetrated from the outer circumference to the inner circumference of 6
58A, 58B... and the rotating terminals (rotating ring'>
54A, 54B, etc. are arranged in correspondence with each other. Each fixed chamber terminal 58A, 58B of the cap 56
A piezoelectric element activation signal is supplied from the control unit 16 to the piezoelectric elements 48, whereby a voltage is separately applied to the plurality of piezoelectric elements 48, and it is possible to make a predetermined slight movement. There is.

In the vicinity of the polygon mirror 22, a light source 60 is arranged which makes a reference light beam (two-dot chain line in FIG. 2) incident on the point of incidence of the writing light beam and the reading light beam on the reflecting mirror 46. Further, a photodetection sensor 62 is disposed corresponding to the light source 60, which receives the reference light beam irradiated from the light source 60 when the polygon mirror 22 comes to the position immediately before the start of the main scanning. Sensor section 62A of this light detection sensor 62
is divided into four parts, and a different correction signal is supplied to the control part 16 depending on the light received by each sensor part. Based on this correction signal, the control unit 16 controls the piezoelectric element 48 to direct the reflecting mirror 46 perpendicularly to the main scanning direction caused by the rotation of the rotating body 44 so that the reference beam irradiates the center point of the sensor unit 62A. It is designed so that it can be tilted in a certain direction.

That is, even if there is a wobble in the rotation due to eccentricity of the rotating shaft 52 of the rotating body 44, the scanning trajectories of the light beams reflected and scanned by each reflecting mirror 46 are made to match. Incidentally, the piezoelectric element 48 has hysteresis, and the reflecting mirror 46 may be positioned at different positions even if the voltage applied is constant depending on the moving direction of the reflecting mirror 46 by the piezoelectric element 48. In this embodiment, this hysteresis is corrected using a magnetic sensor 64, which will be described later.

The configuration for correcting the hysteresis of the piezoelectric element 48, which is a feature of the present invention, will be described in detail below.

As shown in FIG. 3, a magnetoresistive element 66 constituting a part of the magnetic sensor 64 is located in the gap between the rotating body 44 and the reflecting mirror 46 (on the side of the rotating body 44), corresponding to the piezoelectric element 48. installed.

Furthermore, a magnetic body 68 that constitutes a magnetic sensor 64 together with a magnetoresistive element 66 is attached to the reflecting mirror 46 side.

The magnetoresistive element 66 and the magnetic body 68 are arranged to face each other. An angle detector 70 is connected to the output side of the magnetoresistive element 66, and the relative angle between the rotating body 44 and the reflecting mirror 46 is detected according to the resistance value detected by the magnetoresistive element 66. . Further, a piezoelectric voltage correction circuit 72 is connected to the output side of the angle detector 70. The piezoelectric voltage correction circuit 72 stores the characteristics of the piezoelectric voltage and the angle corresponding thereto, and the angle detector 7
piezoelectric element 4 based on the actual angle detected by 0
It has the role of changing the voltage value applied to 8.

Here, as shown in FIG. 3(A), when the polygon mirror 22 is rotated without eccentricity, the gap size G1 between the magnetic body 68 and the magnetoresistive element 66 is all constant;
The resistance value of the magnetoresistive element 66 is not changed. Here, as shown in FIG. 3(B), if there is eccentricity of the polygon mirror 22, the piezoelectric element 48 causes the rotating body 44 and the reflecting mirror 4 to
A change occurs in the relative angle with 6, and the gap dimension G2 at this time
and G may be different from the dimension Gl.

This causes a change in the magnetic field, and the resistance value of the magnetoresistive element 66 is changed in accordance with this change in gap size, and the rotating body 4
4 and the reflecting mirror 46 are detected. The piezoelectric voltage correction circuit 72 changes the voltage applied to the piezoelectric element 48 based on the detected angle to correct for the hysteresis. Note that the current supplied from the control section 16 to the piezoelectric element 48 is always kept constant.

The operation of this embodiment will be explained below.

When irradiation of the reading light beam from the reading laser 14 is started, this reading light beam is transmitted to the mirror 24,
A polygon mirror 22 via a guichroic mirror 20
is incident on the The polygon mirror 22 is rotated at a constant speed by a signal from the control unit 16, so that the angle of incidence of the reading light beam is changed within a predetermined range, and the direction of the reflected light is changed accordingly. This reflected light reaches the light detection sensor 30 via the converging optical system 26,28. When the optical detection sensor 30 detects this reading light beam, it means that the polygon mirror 22 has come to the position immediately before starting main scanning, and a pulse signal is supplied to the control section 16. The control unit 16 determines that the image recording timing is after a predetermined period of time has elapsed since the input of this pulse signal.

Here, when the image recording timing comes (the position of the polygon mirror 22 becomes the main scanning start position), irradiation of the writing light beam from the writing laser 12 is started. After the writing light beam is modulated by the optical modulator 18, it passes through the guichroic mirror 20 and reaches the polygon mirror 22.
The reflected light is irradiated onto the recording medium 36.

Simultaneously with the start of irradiation with the writing light beam, the recording stage 40 is moved under the control of the control unit 16 to perform sub-scanning.
An image is recorded on the recording medium 36.

Here, the polygon mirror 22 is rotationally driven by a mechanical drive system. Therefore, it is conceivable that the direction in which the light beam is reflected differs depending on each reflecting mirror 46 due to problems with the eccentricity of the rotating shaft 52 and the accuracy of assembly. In other words, the main scanning line pitch is not uniform, causing unevenness in the image. However, in this embodiment, the reference light beam (see FIG.
A dot-dashed line) is irradiated, and each reflection and the inclination of the mirror 46 are corrected based on the direction of reflection of this reference light beam.

This will be explained in detail as follows.

When the polygon mirror 22 is about to start main scanning, a reference light beam is irradiated from the light source 60 (this reference light beam may be irradiated all the time). The reference light beam is reflected by the reflecting mirror 46 and reaches the photodetection sensor 62 . The light detection sensor 62 supplies different correction signals to the control section 16 depending on the light receiving position of the sensor section 62A. The control unit 16 calculates the amount of inclination of the reflecting mirror 46 based on this correction signal, and applies a predetermined voltage to the corresponding piezoelectric element 48 according to the calculation result. Here, for example, if the scanning line pitch deviates in the direction of decreasing (if the direction of reflection of the current light beam is deviated to the upper side of Figure 3 than the direction of reflection of the previous light beam), as shown in Figure 3. As shown, the piezoelectric element 48 to which a predetermined voltage is applied changes from the state shown in FIG.
In the state shown in B), the reflecting mirror 466 can be tilted downward in FIG. By performing this for each reflecting mirror 46, deflection of the light beam due to eccentricity of the rotating shaft 52, etc. is eliminated, and the main scanning line pitch can be kept uniform.

Here, the piezoelectric element 48 applied to this embodiment has hysteresis, and moves in the moving direction of the reflecting mirror 46, that is, from the downward direction in FIG. 3 to the upward direction. Even if the same voltage is applied, the position determined may differ depending on whether the object is moved from an upward direction to a downward direction. To correct this, the magnetic sensor 64 applied to this embodiment detects the relative angle between the reflecting mirror 46 and the rotating body 44, and corrects the voltage value applied to the piezoelectric element 48 to keep the angle constant. I try to do this.

That is, when the reflecting mirror 46 and the rotating body 44 move relative to each other, the magnetoresistive element 66 and the magnetic body 68 move according to the amount of movement.
(See dimensions G2 and G in FIG. 3(B)). When this gap dimension changes, the magnetoresistive element 6
6, the resistance value changes in response to changes in the magnetic field, and this resistance value is supplied to the angle detector 70. In the angle detector 70,
The relative angle between the rotating body 44 and the reflecting mirror 46 is detected based on this resistance value, and this detected value is supplied to the piezoelectric voltage correction circuit 72. The piezoelectric voltage correction circuit 72 stores the characteristics of the piezoelectric voltage and the angle in advance, and if there is a difference between the normal angle for the piezoelectric voltage and the detected angle, the initially supplied piezoelectric The piezoelectric voltage is corrected so that the angle corresponds to the voltage. Thereby, the relative angle between the reflecting mirror 46 and the rotating body 44 according to the piezoelectric voltage is always matched, and the direction of irradiation of the light beam can be changed accurately.

In this embodiment, the magnetic sensor 64 is used as means for detecting the deviation between the rotating body 44 and the reflecting mirror 46, which constitute a part of the angle detecting means, but the distance between the rotating body 44 and the reflecting mirror 46 is Other deviation detection means such as a gap sensor may also be used.

In addition, in this embodiment, a new light source 60 for emitting a reference light beam is added, but the sensor section of the photodetection sensor 30 that receives the reading light beam and obtains the main scanning start time may be divided into four parts as described above. For example, a reading light beam can be used as a reference light beam.

Furthermore, in this embodiment, the angle detector 70 and the piezoelectric voltage correction circuit 72 are embedded in the rotating body 44, but they are built into the control unit 16 and the sensor signal from the magnetoresistive element 66 is sent to the outside of the rotating body 44. You may take it out.

[Effects of the Invention] As explained above, the light beam recording device according to the present invention does not require an optical system for surface tilt correction, and it is possible to make the scanning trajectories of the light beams on the respective reflecting surfaces of the polygon mirror coincide with each other. This has the excellent effect of making the main scanning line pitch on the recording material uniform.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of a light beam recording device according to this embodiment, Fig. 2 is a perspective view of a polygon mirror, and Fig. 3 (A) and (B).
) is a sectional view showing how the rotating body and the reflecting mirror are attached. DESCRIPTION OF SYMBOLS 10... Light beam recording device, 12... Writing laser, 14... Reading laser, 16... Control unit, 36... Recording medium, 44... Rotating body, 46... Reflector, 48... Piezoelectric element, 60... Light source, 62... Light detection sensor, 62A... Sensor section, 64... Magnetic sensor, 66... Magnetoresistive element, 68... Magnetic material, 70...Angle detector, 72...Piezoelectric voltage correction circuit.

Claims (2)

[Claims] (1) A piezoelectric element is disposed between the rotating body and a plurality of reflecting mirrors attached to the circumferential surface of the rotating body, and the amount of electricity supplied to the piezoelectric element is controlled. A light beam recording device comprising a control means for changing the relative angle and matching the main scanning trajectory of an image recording light beam sequentially reflected from each reflecting mirror according to the rotation of a rotating body, the light beam recording device comprising: It has an angle detection means for detecting a relative angle with the mirror, and a correction means for correcting an angular error due to hysteresis of the piezoelectric element by correcting the amount of electricity to the piezoelectric element based on the angle detected by the angle detection means. Light beam recording device. (2) The angle detecting means includes a magnetic sensor which is arranged near the piezoelectric element and whose resistance value changes according to a change in the magnetic field, and a relative relationship between the rotating body and the reflecting mirror based on the resistance value obtained by the magnetic sensor. An angle detection means for detecting an angle;
Claim No. 1 is characterized in that it consists of (
1) The optical beam recording device described in item 1).