JPH02210237A - Surface inclination measuring instrument for optical deflector - Google Patents

Abstract

PURPOSE:To realize high accuracy and size reduction by calculating the difference between the outputs of two beam position detectors and finding the quantity of surface inclination. CONSTITUTION:The laser beam L1 emitted by a light source 1 is split by a polarization beam splitter(BS) 2 into a horizontal and a vertical component. The vertical polarized laser beam L2 is made incident on the BS 4 as a beam L2a through the optical deflector 3. Further, the horizontal polarized laser light L3 is made incident on the BS 4 as a beam L3a through a mirror M1. Then the composite light L4 projected from the BS 4 is made incident on a BS 5 through mirrors M2 and M3. Then the vertical polarized light L5A transmitted through the BS 5 is made incident on a sensor 6 and the horizontal polarized light L5b which is reflected by the BS 5 is made incident on a sensor 7. Then the sensors 6 and 7 detects the positions of the laser beams and output electric signals A and B. Further, the signals A and B are inputted to a differential output circuit C and the difference between the signals A and B is outputted as a final surface inclination signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a surface inclination measuring device that measures the surface inclination angle of an optical deflector using positional deviation of a deflected light beam.

(Prior art) In conventional surface tilt measurement, as shown in FIG. I was measuring.

(Issues to be Solved by the Invention) However, in recent years, the density of scanning devices has increased, and as a result, higher accuracy has been required in measuring the surface inclination of an optical deflector.

Possible methods for increasing the accuracy of the surface tilt measuring device include increasing the accuracy of the beam position detection sensor and increasing the distance from the optical deflector to the sensor. Conventionally, this method has been used to improve accuracy because increasing the distance increases the amount of beam position deviation due to the surface tilt angle, making measurement easier.

However, as precision increases, the effects of vibrations, temperature changes, etc. become a problem, and as we have done in the past, increasing the distance further to achieve higher precision causes problems such as vibrations between the light source, optical deflector, and beam position detection sensor. The noise increases, making it impossible to achieve high accuracy. To solve this problem, it may be possible to use a mirror to return the light beam between the optical deflector and the beam position detection sensor, thereby reducing the distance between the light source, the optical deflector, and the beam position detection sensor, thereby reducing the influence of noise. However, if an error occurs in the midway folding mirror due to vibration, temperature change, etc., an error twice as large as the mirror error will occur in the output beam, making it difficult to ensure accuracy.

(Means for Solving the Problems) The present invention has been made to solve the above problems,
To explain using FIG. 1 corresponding to this embodiment, in the optical deflector surface tilt measurement device according to the present invention, light L1 emitted from a light source 1 enters a first polarizing beam splitter 2.

One of the split lights L2 enters the optical deflector 3, and the remaining light L3 is output from the optical deflector 3 by the second polarizing beam splitter 4 via the mirror M1 without going through the optical deflector 3. It is combined with the emitted light L2a again, and is passed through one or more mirrors M2. The light enters the third polarizing beam splitter 5 via M3, is split again, and each of the split lights L5a, L5
The beam b is incident on two beam position detection sensors 6 and 7, respectively, and the amount of surface tilt is determined by taking the difference between the outputs of the respective sensors.

(Operation) According to the present invention, the light L1 emitted from the light source 1 is split by the first polarizing beam splitter 2 into light L2 having a vertical polarization component and light L3 having a horizontal polarization component. One of the lights L2 enters the scanner 3 and is affected by the surface tilt.

The light L2a that exits the scanning device is light L that is not affected by surface tilt.
Combined with 3a and proceeding 0 When combined, two lights L2
Since the polarization directions of a and L3a are perpendicular to each other, they do not interfere with each other, and even though their optical paths coincide, the light affected by the surface tilt and the light not affected are clearly separated. This synthetic light L4
Immediately before entering the sensor 6, the light is split again by the polarizing beam splitter 5 into two beams with different polarization directions. If the polarization direction split by this polarization beam splitter 5 is the same as the polarization direction split by the first polarization beam splitter 2, light with and without a tilt component can be clearly separated. After that, each beam of light enters the beam position detection sensor 6.7, and the amount of positional deviation is measured, but at this time, the light with the tilt component is affected by the error of the mirror in the middle. , the other light is also being received, so by taking the difference in their respective outputs, it is possible to isolate only the influence of the surface tilt and perform highly accurate measurements.

(Example) FIG. 1 shows the configuration of a rotating polygon mirror surface tilt measurement device. A laser beam L1 emitted from a He Na laser of a light source 1 first enters a polarizing beam splitter 2. The polarization direction of the HeNe laser is 4 degrees from the horizontal direction.
The direction is tilted by 5 degrees, and the polarizing beam splitter 2 is installed so that it can be divided into a horizontal component and a vertical component, so the light L1 coming from the laser is split almost equally by the polarizing beam splitter 2. . The vertically polarized laser beam L2 is incident on the rotating polygon mirror, is scanned, and at the same time is affected by the surface inclination and is emitted as a beam L2a in the right direction in the figure. On the other hand, the horizontally polarized laser beam is emitted from the polarization beam splitter 2 as beam L3 in the right direction in the figure, and L3a is emitted in the right direction in the figure via the mirror M1, where it is combined with the vertically polarized light that has passed through the scanner. One combined light L4 is transmitted through mirror M2 and mirror M3,
The light is incident on the polarizing beam splitter 5. Here, too, the polarizing beam splitter 5 is installed so as to reflect only horizontally polarized light, so the vertically polarized light L5 has a tilt component of the scanner surface.
The light a passes through the polarizing beam splitter 5 and enters the sensor 6, and the horizontally polarized light L5b, which does not have a tilt component, is reflected by the polarizing beam splitter 5 and enters the sensor 7. Sensor 6 and sensor 7 detect the position of the laser beam,
Output as electrical signal A and electrical signal B. The output electrical signals A and B are input to a differential output circuit C, and the difference between the electrical signals A and B is output as a final signal. If the folding mirror M2 and the folding mirror M3 on the way have an error from the predetermined folding angle due to vibration or temperature change, the combined light will deviate from the predetermined position due to the error component, and the polarizing beam splitter 5, sensor 6, and sensor 7 is input. At this time, since the influence of the error on the composite light L4 is the same for both the horizontally polarized light and the vertically polarized light, the same amount of the influence of the error on the mirrors M2 and M3 is detected by both the sensors 6 and 7. However, since the differential output circuit then calculates the difference between the output signal A of sensor 6 and the output signal B of sensor 7, the error component of the same amount for both vertically polarized and horizontally polarized light generated by the mirror becomes 0. Instead, only the different components of vertically polarized light and horizontally polarized light are output. Errors in the folding mirrors M2 and M3 placed in the middle do not affect the output signal, so with this configuration, a highly accurate and compact surface tilt measuring device can be realized.

(Effects of the Invention) As described above in detail, according to the present invention, light emitted from the light source enters the first polarizing beam splitter.

One of the split lights enters the optical deflector, and the remaining light is combined with the output light from the optical deflector by a second polarizing beam splitter without going through the optical deflector, and is combined with the output light from the optical deflector into one or more beams. The beam enters a third polarizing beam splitter via a mirror, is split again, and each split beam enters two beam position detection sensors. Since the amount of tilt is determined, it is possible to construct a highly accurate and compact surface tilt measurement device that is not easily affected by noise. It also has the advantage of being applicable to other measurement systems that output laser beam position errors.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a surface inclination measuring device showing an embodiment of the present invention, and FIG. 2 is a configuration diagram of a surface inclination measuring device showing a conventional example. 1... Light source 2.4.5... Deflection beam splitter 3...
. . . Light deflector 6.7 . . . Sensors Ml, M2. M3...Mirror A, B...Electric signal C...Differential output circuit Ll, L2. L3. L2a, L3a, L4. L5a. L5b... Beam patent applicant Copal Electronics Co., Ltd. Figure 2

Claims (1)

[Claims] The light emitted from the light source enters the first polarizing beam splitter, one of the split lights enters the optical deflector, and the other light is optically deflected by the second polarizing beam splitter without going through the optical deflector. recombining with the light emitted from the device and entering the third polarizing beam splitter via one or more mirrors,
An optical deflector characterized in that the light is split again, each of the split lights is incident on two beam position detection sensors, and the amount of surface tilt is determined by taking the difference between the sensor outputs. A device for measuring surface inclination.