JP2009103592A - Collimation inspection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a collimation inspection device capable of carrying out collimation quickly and precisely. <P>SOLUTION: The collimation inspection device divides a wave front of a light beam to be inspected into two wave fronts having an optical path difference by a share plate, and forms an interference pattern image of both wave fronts on an interference pattern observing part, by superposing the two wave fronts to be projected, and a beam incident angle detecting part for detecting a beam incident angle into the share plate is provided integrally with the collimation inspection device. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a collimation inspection apparatus, and more particularly to a shear plate collimation inspection apparatus.

In the measurement using a beam, collimation is performed to make the beam a parallel light beam that does not diverge or converge in order to reach the beam farther, that is, to improve measurement accuracy.
In this collimation, a shear plate collimation inspection apparatus is generally used.
FIG. 5 shows a schematic configuration of a conventional typical shear plate collimation inspection apparatus 200.
The shear plate collimation inspection apparatus 200 includes a wedge-shaped optical flat 2 that receives an incident beam L0, and a transparent plate that includes a collimating reference line (not shown) that receives the beam L0 transmitted through the optical flat 2. A screen 3 is provided.
The wedge-shaped optical flat 2 is arranged so that the beam L0 is incident at an angle of 45 degrees. The optical flat 2 divides the wavefront of the beam L0 into two wavefronts (L1, L2) having an optical path difference by reflecting the beam L0 on the front and back surfaces with substantially the same intensity. The two wavefronts (L1, L2) are both reflected in the direction perpendicular to the optical axis of the beam L0 and are projected onto the screen 3 in a superimposed manner. On the screen 3, an interference pattern image 33 of two wave fronts (L1, L2) is displayed. The parallelism of the beam L0 can be evaluated from the state of the interference pattern.
Based on the parallelism of the interference fringes thus obtained, adjustment and inspection of the collimation of the beam can be performed (see, for example, Patent Document 1).
In the prior art, a technique is known in which the angle of interference fringes already projected on the observation surface is measured to determine the radius of curvature of the beam wavefront (see, for example, Patent Document 2). Japanese Patent Application Laid-Open No. 2004-228561 describes a mechanism that the angle of the interference fringes is inclined with respect to the collimating reference line.

JP-A-11-190679 JP-A-6-11388

In general, in collimation, measurement is performed after setting the beam to be incident substantially perpendicular to the incident surface of the collimation inspection apparatus. If an error occurs during the setting before the measurement, this error becomes an error in the angle between the interference fringe and the reference line.
Therefore, when it is desired to measure the angle between the interference fringe and the reference line with high accuracy, it is necessary to perform setting before measurement precisely.
However, in the conventional collimation inspection apparatus, setting before measurement is often performed visually, and it has been difficult to perform precisely. Further, when collimation inspection or measurement is performed in large quantities as in a production line or the like, there is a problem that it is time-consuming and time-consuming if settings before measurement are made visually for each product.

  An object of the present invention is to provide a collimation inspection apparatus that enables precise and rapid collimation.

  The first aspect of the present invention is to divide the wavefront of the light beam to be inspected into two wavefronts having an optical path difference by the shear plate and project the two wavefronts in an overlapping manner, thereby causing an interference pattern observation unit. A collimation inspection apparatus for projecting interference pattern images of both wavefronts, wherein a beam incident angle detector for detecting a beam incident angle on the shear plate is provided integrally with the collimation inspection apparatus. To do.

  According to a second aspect of the present invention, in the invention according to the first aspect, the beam incident angle detector includes a beam splitter for reflecting a transmitted beam from the shear plate, and a transmitted beam reflected by the beam splitter. And an image forming lens for image forming and a screen for displaying an image obtained by the image forming lens.

  According to a third aspect of the present invention, in the invention according to the second aspect, in the beam incident angle detector, an actual beam incident position displayed on the screen when the collimation inspection is actually performed, A beam incident deviation angle is obtained from a deviation distance from an ideal beam incident position displayed on the screen when a collimation inspection is performed as set.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the angle of the interference fringes is corrected and calculated from the value of the beam incident deviation angle.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the beam incident angle and an ideal interference fringe angle corresponding to the beam incident angle are actually projected. The relationship between the interference fringe angle and the interference fringe angle data is saved, and the ideal interference interference is automatically calculated by obtaining only the incident beam fringe angle and the projected interference fringe angle when the collimation inspection is actually performed. It is characterized in that the angle of the stripe is obtained.

  According to a sixth aspect of the present invention, in the invention according to any one of the first to fifth aspects, the shear plate has a wedge shape.

  According to the above configuration, the collimation inspection apparatus is provided with the beam incident angle detection unit, and the angle of incidence can be easily understood by extracting only the angle component in the incident beam, so that the position of the collimation inspection apparatus is not adjusted. Now, collimation inspection can be performed accurately and quickly.

  Hereinafter, a collimation inspection apparatus according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of a collimation inspection apparatus according to the present embodiment.
FIG. 2 is a diagram illustrating a schematic configuration of the collimation checker.
As shown in FIGS. 1 and 2, the collimation inspection apparatus 100 according to the present embodiment includes a collimation checker 1, an interference pattern observation unit 30, and a beam incident angle detection unit 40.

As shown in FIGS. 1 and 2, the collimation checker 1 has a shear plate 2 provided in a cubic box-shaped outer frame 7. A beam incident window 71 a is provided on the beam incident side surface 71 of the outer frame 7. On the surface 72 facing the beam incident side surface 71,
A transmitted beam exit window 72a is provided. A reflected beam exit window 73a is provided on a surface 73 on the left side in the direction orthogonal to the surfaces 71 and 72.

As shown in FIGS. 1 and 2, the shear plate 2 has a wedge shape having a thin, substantially trapezoidal hexahedral shape. The upper surface, the lower surface, and the left and right side surfaces are rectangular parallel surfaces, and the front and back surfaces form a predetermined angle. By making the front and back surfaces form a predetermined angle, interference fringes as described later can be obtained.
The shear plate 2 is placed on the shear plate placing surface 75 of the collimation checker 1 with the hexahedron-shaped lower surface.

In the shear plate 2, the beam L that enters the collimation checker 1 perpendicularly to the beam incident window 71 a from the beam incident window 71 a is incident on the incident surface 10 of the shear plate at an angle of 45 degrees. The transmitted beam L ′ from the reflecting surface 11 facing the incident surface 10 is transmitted perpendicularly to the transmitted beam exit window 72a, and the reflected beam L ″ from the incident surface 10 and the reflecting surface 11 is transmitted. It is installed so as to reflect perpendicularly to the reflected beam exit window 73a.
Further, a transparent plate 5 is provided inside the collimation checker 1 in the reflected beam exit window 73a. A collimating reference line 8 is provided in the center of the transparent plate 5 in the meridian direction.

Next, the interference pattern observation unit 30 will be described.
As shown in FIG. 1 or 2, the interference pattern observation unit 30 is connected to the collimation checker 1 and is located on the left side of the collimation checker 1 when viewed from the beam source 8.
The interference pattern observation unit 30 includes an imaging lens 4 and a screen 3. The interference pattern observation unit 30 may be entirely covered with an outer frame, like the outer frame 7 used in the collimation checker 1.

The operations of the collimation checker 1 and the interference pattern observation unit 30 are as follows.
The beam L emitted from the beam source 8 is incident from the beam incident window 71a of the collimation checker 1. The beam L is incident on the incident surface 10 of the wedge-shaped shear plate 2 arranged so that the beam L is incident at an angle of 45 degrees. The beam L is reflected in the direction perpendicular to the incident direction by the incident surface and the reflecting surface of the share plate 2. As a result, the reflected beam L ″ is transmitted through the transparent plate 5 on which the collimating reference line 8 is arranged. Then, the reflected beam L ″ transmitted through the transparent plate 5 is projected onto the screen 3 by the imaging lens 4. That is, with the above arrangement, interference fringes due to reflection from the entrance surface 10 and the reflection surface 11 of the wedge-shaped shear plate 2 are projected onto the screen 3.

  From FIG. 3 showing the interference fringes observed by the collimation inspection apparatus 100, the interference fringes projected onto the screen 3 as described above become an interference fringes having no inclination when the beam L is parallel light (FIG. 3 (c). )). On the other hand, when the beam L is divergent light or convergent light, it has an inclination and becomes a sharp interference fringe (FIGS. 3B and 3D). This is because the interference fringes have an inclination due to the influence of both the interference of the tilt that should occur in the horizontal direction due to the wedge of the shear plate 2 and the interference due to the shear that should occur in the vertical direction. Further, when the beam L becomes completely parallel light, there is no influence of the interference due to the shear, and only the influence of the interference due to the tilt exists, so that the interference fringes are in the horizontal direction without inclination. The beam L is diverging when the interference fringe is inclined to the right shoulder, and the beam L is converged when the interference fringe is inclined to the left shoulder.

Next, the beam incident angle detector 40 will be described.
The beam incident angle detector 40 is connected to the collimation checker 1, and the beam source 8
As viewed from behind the collimation checker 1.
Note that the beam incident angle detection unit 40 may be positioned other than the rear of the interference pattern observation unit 30 when viewed from the beam source 8 as long as the beam incident angle can be obtained. Even if the beam incident angle measuring unit 40, the collimation checker 1 and the interference pattern observing unit 30 are not directly connected, they need only be integrated as the collimation inspection apparatus 100.
The beam incident angle detector 40 includes a beam splitter 6, an imaging lens 4a, and a screen 3a. The beam splitter 6 reflects the incident beam in a direction perpendicular to the incident direction, and is arranged so that the incident beam is incident at an angle of 45 degrees. The beam splitter 6 may be a cube type beam splitter or a plane parallel plate as long as it can irradiate the screen 3a with a beam. The beam splitter 6 may reflect and transmit the beam like a half mirror, or may transmit most of the beam like a parallel plane plate. In the present embodiment, a plane parallel plate 6 is illustrated as the beam splitter 6.
Note that the beam incident angle detection unit 40 may be entirely covered with the outer frame, like the outer frame 7 used in the collimation checker 1.

The operation of the beam incident angle detector 40 is as follows.
The beam L ′ that has passed through the reflecting surface 11 of the share plate 2 passes through the transmitted beam exit window 72 a of the collimation checker 1. The transmitted beam L ′ is incident on the plane parallel plate 6. The incident transmitted beam L ′ is reflected by the parallel flat plate 6 in a direction perpendicular to the incident direction of the transmitted beam L ′. As a result, the reflected transmitted beam L ′ is projected onto the screen 3a by the imaging lens 4a. That is, with the above arrangement, the incident position of the beam L ′ that has passed through the wedge-shaped shear plate 2 on the screen 3 a is projected onto the measurement screen.

FIG. 4 is a diagram illustrating the function of the beam incident angle detection unit 40 of the present embodiment. In FIG. 4, the actual beam incident position (hereinafter also referred to as the actual beam position) is projected onto the measurement screen as described above, so that the measurement is performed when the beam L is incident on the shear plate 2 at the set incident angle. Based on the beam incident position on the screen 3a (hereinafter also referred to as an ideal beam position), how much the actual beam incident position is deviated from the ideal beam position is determined. By obtaining this deviation, the deviation of the incident angle of the beam is calculated.
The above calculation will be described below.

As shown in FIG. 4, the center of the position where the ideal beam as set passes through the imaging lens is O ′, and the center of the ideal beam position projected on the screen 3a is O. The center of the actual beam position is P, and the positional deviation distance between the ideal beam and the actual beam, that is, the distance between O and P is y. Also, let f be the focal length, that is, the distance between O and O ′. A beam incident deviation angle, which is a deviation in incident angle between the ideal beam and the actual beam, is defined as d.
At this time, the positional displacement distance y is expressed by the following formula (1).
y = f × tand (1)

From equation (1), the deviation angle d is d = tan ⁻¹ (y / f) (2)
Thus, the deviation angle d can be obtained.
Thereby, since the setting angle of the ideal beam is known, a numerical value in consideration of the deviation angle d with respect to this setting angle is an actual beam incident angle.

  As described above, by determining the actual beam incident angle, it is easy and precise to collimate by moving the beam source corresponding to all products without visually moving the position of the collimation device for each product. Inspection can be performed.

  Further, correction of the inclination angle of the interference fringes obtained in the interference pattern observation unit by the beam incidence angle obtained in the beam incident angle detection unit will be described below.

For example, a case where the radius of curvature of the beam is obtained will be given.
As shown in FIG. 3A, the angle due to the inclination of the interference fringes is θ, the lateral shift amount of the reflected light from the shear plate is S, the fringe interval of the interference fringes is t, the incident beam wavelength is λ, When the curvature radius is r, r is obtained by the following formula (3).
r = St / λsinθ (3)

From FIG. 1, when the collimation inspection apparatus is tilted with the beam axis of the reflected beam reflected from the shear plate as the rotation axis, the incident angle is deviated by d as described above. It is necessary to consider. In consideration of d, the equation (3) for obtaining the radius of curvature r becomes the following equation (4): r≈St / λsin (θ−d) (4)

  As shown in equation (4), the ideal interference fringe angle T (= θ−d) corresponding to the beam incident angle can be obtained by subtracting the deviation angle d from the angle θ due to the inclination of the interference fringes. . Thereby, a precise curvature radius can be calculated | required, without moving a collimation inspection apparatus for a correction | amendment. When the collimation inspection apparatus is tilted with the vertical axis as the rotation axis with respect to the top view of the collimation inspection apparatus in FIG. 1, no correction is necessary.

  In addition, when the relationship between the beam incident angle, the ideal interference fringe angle corresponding to the beam incident angle, and the actually projected interference fringe angle is saved, the collimation inspection is performed. The ideal interference fringe angle may be automatically obtained by obtaining only the beam incident deviation angle and the projected interference fringe angle. Thereby, the correction calculation for the collimation inspection can be omitted.

According to this embodiment, there are the following effects.
In the collimation inspection apparatus, since the interference pattern observation unit and the beam incident angle detection unit are integrally configured, the beam incident angle can be obtained before or simultaneously with the collimation inspection, and easy and precise collimation inspection setting can be performed. it can.
Further, if the angle of inclination of the interference fringe obtained in the interference pattern observation unit is corrected and calculated based on the beam incident angle obtained in the beam incident angle detection unit, not only the collimation inspection device but also the beam source and other devices can be moved. And collimation inspection can be performed. Therefore, it becomes possible to inspect at a high speed on a production line or the like.

It is a top view which shows schematic structure of the collimation inspection apparatus by this embodiment. It is a figure which shows schematic structure of a collimation checker. It is a figure which shows the interference fringe observed with a collimation inspection apparatus. It is explanatory drawing which shows the function of the beam incident angle detection part of this embodiment. It is sectional drawing and the front view which show schematic structure of the conventional collimation inspection apparatus.

Explanation of symbols

1 Collimation checker 2 Share plate (optical flat)
3 Screen 4 Imaging lens 5 Transparent plate 6 Parallel plane plate 7 Outer frame 8 Collimating reference line 9 Beam source 10 Incident surface 11 Reflecting surface 30 Interference pattern observation unit 33 Interference pattern image 40 Beam incident angle detection unit 100 Collimation inspection Device 200 Collimation inspection device L Beam L ′ Transmitted beam L ″ Reflected beam L0 Beam (before division)
L1, L2 beam (after splitting)
La beam (ideal)
Lb beam (actual)

Claims (6)

By dividing the wavefront of the light beam to be inspected into two wavefronts having an optical path difference by the share plate and projecting the two wavefronts in an overlapping manner, an interference pattern image of both wavefronts is projected at the interference pattern observation unit. A collimation inspection device to be produced,
A collimation inspection apparatus, wherein a beam incident angle detection unit for detecting a beam incident angle on the share plate is provided integrally with the collimation inspection apparatus. The beam incident angle detector is
A beam splitter for reflecting the transmitted beam from the shear plate;
An imaging lens for imaging the transmitted beam reflected by the beam splitter;
The collimation inspection apparatus according to claim 1, further comprising: a screen for projecting an image obtained by the imaging lens.   In the beam incident angle detection unit, the actual beam incident position displayed on the screen when the collimation inspection is actually performed, and the ideal beam incident displayed on the screen when the collimation inspection is performed as set. The collimation inspection apparatus according to claim 2, wherein a beam incident deviation angle is obtained from a deviation distance from the position.   4. The collimation inspection apparatus according to claim 1, wherein the angle of the interference fringes is corrected and calculated from the value of the beam incident deviation angle.   Data on the relationship between the beam incident angle, the ideal interference fringe angle corresponding to the beam incident angle, and the actually projected interference fringe angle is stored, and the beam when the collimation inspection is actually performed 5. The collimation inspection apparatus according to claim 1, wherein the ideal interference fringe angle is automatically obtained by obtaining only the incident deviation angle and the projected interference fringe angle. The collimation inspection apparatus according to claim 1, wherein the shear plate has a wedge shape.

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