JPH0829715A - Mirror adjusting device - Google Patents

Abstract

PURPOSE:To easily and highly accurately perform the fine adjustment of a reflection mirror angle caused by the change or the like in ambient temperature by using a Peltier element at a mirror adjusting device. CONSTITUTION:The Peltier element 4 is held between two supporting members 2 and 3 which are flexible by heat, and both end parts of a mirror 1 abut on respective one end parts of the supporting members 2 and 3. When a current is made to flow through the Peltier element 4 in a specified direction, the contact part of the Peltier element 4 and one supporting member 2 is made to be in a high temperature state, and also the contact part of the Peltier element 4 and the other supporting member 3 is made to be in a low temperature state. Therefore, one supporting member 2 is stretched by thermal expansion, and the upper end part of the abutting mirror 1 on the supporting member 2 is pressed, so that the tilt angle of the mirror 1 is adjusted in a downward direction. On the other hand, when the current is made to flow through the Peltier element 4 in a reverse direction, the tilt angle of the mirror 1 is adjusted in an upward direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mirror adjusting device used in, for example, a laser scanning optical unit in an image forming apparatus and adjusting a reflection angle of a mirror for reflecting a laser beam.

[0002]

2. Description of the Related Art In a laser scanning optical unit of an image forming apparatus, a beam from a semiconductor laser as a light source is guided to a polygon mirror through a mirror unit having a collimating lens, a cylinder lens and a reflecting mirror, and the polygon After the beam is deflected by the mirror, the beam is guided to the surface of the photosensitive drum through a projection lens, a cylinder mirror (or a cylinder lens), and the like.

In the mirror unit of the optical unit, however, there is a problem in that the mounting angle of the reflection mirror is displaced due to the effect of thermal expansion due to the change in environmental temperature, which causes displacement of the printing position. For this reason, the mirror unit is usually provided with a mirror adjusting device for finely adjusting the reflection angle of the beam.
As an example of a conventional mirror adjustment device, one shown in FIG. 6 is known. In the adjusting device shown in FIG. 6, a supporting frame 51 having a substantially L-shaped cross section is fixed to a frame (not shown) of the optical unit, and the front surface of the supporting frame 51 is pressed by a leaf spring 52. A reflection mirror 53 is arranged. An adjusting screw 54 is screwed onto the upper portion of the supporting frame 51 so as to penetrate the supporting frame 51, and the tip of the adjusting screw 54 is brought into contact with the upper end of the rear surface of the reflecting mirror 53. With this configuration, when the knob of the adjusting screw 54 is manually rotated, the upper end of the reflecting mirror 53 is swung in the direction of arrow P against the biasing force of the leaf spring 52, which causes The reflection angle in the height direction of the reflection mirror 53 is adjusted.

[0004]

However, the conventional adjusting device as described above has a problem that the adjusting operation is extremely difficult because the reflection angle is adjusted manually. In addition, there is a problem that the adjustment with such an adjusting screw has a limitation in the pitch of the screw, which makes it difficult to perform fine adjustment, and there is a limit in the accuracy of the adjustment due to the presence of backlash.

The present invention has been made in order to solve such a problem, and provides a mirror adjusting device capable of easily and highly accurately performing fine adjustment of the angle of a reflecting mirror caused by a change in environmental temperature. It is intended to be provided.

[0006]

The present inventors have found that the Peltier device is used in this type of mirror adjusting device to solve the above-mentioned problems, and have completed the present invention. In short, the mirror adjusting device according to the present invention is a mirror adjusting device for adjusting the reflection angle of the mirror 1 for reflecting light, as shown in the principle diagram of FIG. The Peltier element 4 is sandwiched between the supporting members 2 and 3, and both ends of the mirror 1 are brought into contact with one end of each of the supporting members 2 and 3.

In the present invention, a deviation detecting means for detecting deviation of the reflected light by the mirror, and a current control means for controlling at least the polarity of the current flowing to the Peltier element based on the output signal from the deviation detecting means. Is preferably provided.

[0008]

In the present invention, since the Peltier element 4 is sandwiched between the two support members 2 and 3 which can be expanded and contracted by heat, when a current is passed through the Peltier element 4 in a predetermined direction, the Peltier element 4 4 and one of the supporting members 2 are brought into a high temperature state, and the Peltier element 4
The contact portion between the other support member 3 and the other support member 3 is brought to a low temperature state. Therefore, one support member 2 is expanded by thermal expansion, the upper end of the mirror 1 that is in contact with this support member 2 is pressed, and the tilt angle of the mirror 1 is adjusted downward. On the other hand, when an electric current is applied to the Peltier element 4 in the direction opposite to the predetermined direction, the Peltier element 4 and one supporting member 2
The contact portion between the Peltier element 4 and the other support member 3 is brought into a high temperature state while the contact portion with is brought into a low temperature state. Therefore, in this case, the other support member 3 is extended to adjust the tilt angle of the mirror 1 in the upward direction.

In the present invention, there are further provided a deviation detecting means for detecting deviation of the light reflected by the mirror, and a current control means for controlling at least the polarity of the current flowing to the Peltier element based on the output signal from the deviation detecting means. With this provision, the adjustment direction and the adjustment amount of the mirror are automatically detected and the adjustment of the mirror based on the detection is automatically performed, so that the mirror angle can be adjusted more easily.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, specific embodiments of the mirror adjusting device according to the present invention will be described with reference to the drawings.

This embodiment is applied to a laser scanning optical unit of an image forming apparatus. In the laser scanning optical unit 10 shown in FIG. 2, the laser beam from the light source 11 composed of a semiconductor laser is guided to a collimator lens 12 and made into parallel light, and the passing beam of this collimator lens 12 is a cylinder lens. After passing through 13, the light is guided to a polygon mirror 16 via a mirror unit 15 having a reflection mirror 14, and the cylinder lens 1
3 is used to narrow down on the polygon mirror 16 in the sub-scanning direction of the photosensitive drum 17 (direction orthogonal to the axis of the photosensitive drum 17). Then, the reflected beam of the polygon mirror 16 is guided to the photosensitive drum 17 via a plurality of projection lenses 18 and a cylinder mirror 19 (or a cylinder lens) and is imaged on the surface of the photosensitive drum 17. Thus, the laser beam scans the surface of the photosensitive drum 17 in the main scanning direction (the direction of arrow B) when the polygon mirror 16 rotates in the direction of arrow A, and the sub-scanning direction when the photosensitive drum 17 rotates about the axis. Scanning is performed in the direction of arrow C.

As shown in FIG. 3, the mirror unit 15 includes a rod-shaped lower support 22 fixed to the frame 20 of the optical unit 10 by two bolts 21 and 21.
And a rod-shaped upper support 23, which is also arranged substantially parallel to the lower support 22, and both support 22 and 23.
And a Peltier element 24 formed by sandwiching and sandwiching the contact surfaces between the support bodies 22 and 23 and adhering and fixing them. Then, the lower support 22 and the upper support 2
The lower end and the upper end of the back surface of the reflection mirror 14 are respectively brought into contact with one end surface of the reflection mirror 14, and the front surface of the reflection mirror 14 is pressed by two leaf springs 25 (only one is shown) fixed to the frame 20. It is attached. Here, the lower support 22 and the upper support 23 are made of a material having a high thermal expansion and contraction rate (the same material) such as a copper alloy or an aluminum alloy so as to have the same length.

Further, as shown in FIG. 2, an optical sensor 26 is provided between the projection lens 18 and the cylinder mirror 19 and near the end of the cylinder mirror 19. This optical sensor 26 is a polygon mirror 1.
6, which is for detecting the deviation of the laser beam (scanning light) reflected by 6 in the sub-scanning direction, and as shown in FIG. 4, the upper sensor portion 26a and the lower sensor portion 26b.
It is composed of a two-divided PIN photodiode consisting of Then, the respective output signals from the upper side sensor unit 26a and the lower side sensor unit 26b are input to the differential amplifier 28 via the upper side sensor amplifier 27a and the lower side sensor amplifier 27b, respectively. Peltier device 24 via Peltier driver 29
The direction and the current value of the current flowing through are controlled.

Next, the operation of adjusting the tilt angle of the reflecting mirror 14 when the mounting angle of the reflecting mirror 14 is deviated due to thermal expansion of the frame 20 of the optical unit 10 will be described with reference to FIGS. Will be described with reference to.

In the normal state, the reflected light from the reflection mirror 14 is applied to the central portion of the optical sensor 26 in the vertical direction, so that the optical sensor 26 cannot detect the deviation of the scanning light.
The Peltier driver 29 is not activated (see FIG. 5 (a)).

When the scanning light is directed downward, the amplitude of the output signal from the lower sensor amplifier 27b is the upper sensor amplifier 2b.
It becomes larger than the amplitude of the output signal from 7a. For this reason, the Peltier driver 29 is calculated by the differential amplifier 28.
Causes a current to flow through the Peltier element 24 so as to increase the temperature of the lower support 22 and decrease the temperature of the upper support 23. Thus, as shown in FIG. 5B, the lower support 22 is expanded by thermal expansion, and the tilt angle of the reflection mirror 14 is adjusted upward.

On the other hand, when the scanning light is directed upward, the amplitude of the output signal from the upper sensor amplifier 27a becomes larger than the amplitude of the output signal from the lower sensor amplifier 27b. For this reason, the Peltier driver 29 causes a current to flow through the Peltier element 24 so as to raise the temperature of the upper support 23 and lower the temperature of the lower support 22 by the operation of the differential amplifier 28. Thus, as shown in FIG. 5C, the upper support 23 is expanded by thermal expansion, and the reflection mirror 1
The tilt angle of 4 is adjusted downward. The angle adjustment of the reflection mirror 14 is executed until the amplitude of the output signal from the upper sensor amplifier 27a and the amplitude of the output signal from the lower sensor amplifier 27b become the same.

When the lower support 22 and the upper support 23 expand due to an increase in the ambient temperature of the mirror unit 15, both support 22 and 23 are expanded as shown in FIG. 5D. Since they both extend, the reflecting mirror 14 does not change its inclination angle only by moving in parallel.

In the above description, the lower support 22 or the upper support 23 is expanded and contracted by changing the direction of the current flowing to the Peltier element 24. However, in addition to the direction of this current, the deviation amount of the scanning light is also added. Accordingly, the tilt angle of the reflection mirror 14 can be finely adjusted by controlling the value of the current flowing to the Peltier element 24.

According to this embodiment, the tilt angle of the reflection mirror 14 can be automatically adjusted while the mirror unit 15 is mounted in the optical unit 10.

In this embodiment, the optical sensor 26 is provided between the projection lens 18 and the cylinder mirror 19, but the optical sensor 26 may be provided between the cylinder mirror 19 and the photosensitive drum 17. Is.

Also, in this embodiment, the lower support 2
2 and the contact surface between the upper support 23 and the Peltier element 24 is fixed by an adhesive.
The lower support 22 and the upper support 23 may be slidable with respect to the Peltier element 24 as long as the structure receives the heat conduction from the heat generating portion and the heat absorbing portion of No. 4. Further, as for the support structure of the reflection mirror 14 with respect to the lower support 22 and the upper support 23, instead of the structure in which the leaf springs 25 are pressed down as in the present embodiment, the lower support 22 and the upper support are provided. The contact surface between 23 and the reflection mirror 14 may be fixed with an adhesive.

The reflection mirror 14 in this embodiment is the mirror 1 in the present invention, the upper support 23 and the lower support 22 are support members 2 and 3, the Peltier element 24 is the Peltier element 4, and the optical sensor 26 ( Upper sensor portion 26a,
The lower sensor section 26b), the upper sensor amplifier 27a, the lower sensor amplifier 27b, and the differential amplifier 28 correspond to the deviation detecting means, and the Peltier driver 29 corresponds to the current controlling means.

[0024]

As described above, according to the present invention, the fine adjustment of the angle of the reflection mirror caused by the change of the environmental temperature can be easily and accurately performed, and the automatic control can be performed. The labor of the operator can be saved.

[Brief description of drawings]

FIG. 1 is a principle diagram of a mirror adjusting device according to the present invention.

FIG. 2 is a schematic diagram showing an overall configuration of a laser scanning optical unit.

FIG. 3 is a side view (a) and a rear view (b) of the mirror unit.

FIG. 4 is a system configuration diagram of a mirror adjusting device.

FIG. 5 is an explanatory view of the tilt angle adjusting operation of the reflection mirror.

FIG. 6 is a side view of a conventional mirror adjustment device.

[Explanation of symbols]

 1 Mirror 2, 3 Supporting Member 4 Peltier Element 10 Laser Scanning Optical Unit 14 Reflecting Mirror 15 Mirror Unit 22 Lower Support 23 Upper Support 24 Peltier Element 26 Optical Sensor 26a Upper Sensor 26b Lower Sensor 27a Upper Sensor Amplifier 27b Lower sensor amplifier 28 Differential amplifier 29 Peltier driver

Claims (2)

[Claims] 1. A mirror adjusting device for adjusting a reflection angle of a mirror for reflecting light, wherein a Peltier element is sandwiched between two supporting members which can be expanded and contracted by heat, and both ends of the mirror are supported by the Peltier element. A mirror adjusting device, which is brought into contact with one end of each member. 2. A shift detecting means for detecting a shift of reflected light by the mirror, and a current control means for controlling at least a polarity of a current flowing to the Peltier element based on an output signal from the shift detecting means. The mirror adjusting device according to claim 1, wherein: