JPH0252209B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is an inspection device for a parabolic mirror, in particular, the reflected light reflected from the parabolic mirror is further reflected on an output surface, and the reflected light is The present invention relates to a parabolic mirror inspection device that inspects the condition of the mirror surface of a parabolic mirror based on the pattern of interference fringes generated by light and newly emitted light.

(Prior Art) Conventionally, a device as shown in FIG. 5 has been used to determine the quality of the mirror surface of a parabolic mirror. That is, in FIG. 5, a parallel light beam obtained by a laser device or the like is made incident on the mirror surface of the parabolic mirror 21 to be inspected, and the reflected light is provided near the focal point of the parabolic mirror 21. Observe the spot diameter L of the focal point on the diffuser plate 22, such as ground glass, using the microscope 23 from the opposite side of the diffuser plate 22, and move the diffuser plate 22 left and right to the position where the spot diameter L is the minimum. The quality of the mirror surface of the parabolic mirror 21, that is, the distortion of the mirror surface, was determined from the size of the spot diameter.

(Problems to be Solved by the Invention) In the conventional method, the spot diameter L reflected on the diffuser plate 22 is observed using the microscope 23, which makes it difficult to see.
There is a drawback that the value of the spot diameter L varies depending on the observer, and also, from the spot diameter reflected on the diffuser plate 22, it is difficult to determine whether or not the parabolic mirror 21 is tilted with respect to the incident parallel rays. There was also a drawback that it was difficult to know how to correct the attitude of the parabolic mirror 21.

The present invention aims to solve the above-mentioned drawbacks, and the reflected light reflected from the parabolic mirror is further reflected on the output surface, and the reflected light and the newly emitted output light interfere with each other. The quality of the mirror surface of a parabolic mirror can be determined from the interference fringe pattern generated by this, and the direction in which the attitude of the parabolic mirror itself should be corrected can be obtained from the interference fringe pattern. The purpose is to provide inspection equipment.

(Means for Solving the Problem) Therefore, the parabolic mirror inspection device of the present invention emits a laser beam from the focal position of the parabolic mirror to the parabolic mirror, and generates a first parallel beam as reflected light. A means of generating
Means for reflecting the first parallel light by a plane mirror disposed perpendicularly to the first parallel light, causing it to enter the parabolic mirror again, and condensing the reflected light at the focal point of the parabolic mirror. Then, the laser beam reflected again from the parabolic mirror is reflected at an angle equal to the incident angle by a reflecting surface disposed perpendicular to the focused optical axis at the focal position and directed toward the plane mirror. a means for generating parallel light of said first parallel light and said second parallel light disposed between said parabolic mirror and said plane mirror, said means for blocking a part of the optical path between said two mirrors; It consists of a means for projecting interference fringes produced by interference with parallel light, and is characterized by inspecting distortion of the parabolic mirror from the pattern of the interference fringes.

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

(Example) Fig. 1 is a configuration diagram of an off-axis parabolic mirror as an embodiment of the parabolic mirror inspection device according to the present invention, Fig. 2 is an enlarged explanatory view of the light emitting part, and Fig. 3 4 shows an example of the pattern of interference fringes projected on the screen, and FIG. 4 shows another example of the structure of the light emitting section.

Here, "off-axis" means a mirror surface excluding the central axis of the parabolic mirror and its vicinity. In other words, it refers to the part that is off the central axis of the parabolic mirror.

In FIG. 1, reference numeral 1 denotes a light emitting section, into which a laser beam from a laser device 2 is incident. In front of the light emitting part 1, there is a curvature with a mirror finish,
That is, a parabolic mirror 3 whose distortion is inspected is installed. The focus of the parabolic mirror 3 is set on the optical axis of the light emitting section 1, and the parabolic mirror 3 is aligned so that the light emitted from the light emitting section 1 becomes a first parallel ray and at the focal position. The light emitting section 1 is arranged so that the light emitting surface thereof faces. Further, a plane mirror 4 that reflects the light incident from the parabolic mirror 3 is installed perpendicular to the parallel rays.
Therefore, for example, light emitted from the 0 point of the light emitting section 1, which may be regarded as a point light source, toward the point A of the parabolic mirror 3 is reflected at the point A of the parabolic mirror 3, and this reflection The light enters point B of the plane mirror 4, which is installed perpendicular to the light. The light incident on point B of the plane mirror 4 is reflected and returns to the zero point of the light emitting section 1 through the same path. Similarly, from the 0 point of the light emitting part 1 to the parabolic mirror 3
The light emitted toward point C is reflected at point C of the parabolic mirror 3 and enters point D of the plane mirror 4.
The light incident on the point D of the plane mirror 4 is reflected and returns to the zero point of the light emitting section 1 through the same path.

As is clear from the above explanation, the light emitting section 1 is equipped with a fine movement mechanism that moves in three axial directions (not shown) so that the optical path OAB and the optical path OCD have the same length. (not shown), and the parabolic mirror 3 is equipped with a rotation mechanism (not shown). Parallel light forms between the parabolic mirror 3 and the plane mirror 4, and all light at positions perpendicular to the parallel light has the same light phase. This parabolic mirror 3 and plane mirror 4
A screen 5, which also serves as a shielding plate for blocking about half of the parallel light, is provided between the two.

FIG. 2 is an enlarged explanatory diagram of the light emitting section, and shows an example in which the light emitting section 1 uses an optical fiber. The optical fiber 7 consists of a core 8 and a cladding 9, and the laser light incident from the laser device 2 passes through the core 8 and is emitted from the end face of the optical fiber 7 as a point light source. The light emitted from the end face of the optical fiber 7, that is, the core 8, is indicated by a solid line in FIG. The end face of the optical fiber 7, especially the output face of the core 8, is smoothed.

As already explained in FIG. 1, the light emitted from the O point of the light emitting part 1 is reflected at each point, A point of the parabolic mirror 3 and B point of the plane mirror 4, and the light is emitted through the same path. Return to point O in part 1. Now, if this reciprocating light is represented by a solid line and a dashed-dotted line in FIG. 2, the reciprocating light enters the end face of the optical fiber 7, that is, the core 8, a part of which causes Fresnel reflection, and the reflected light is This occurs on the smooth surface of the core 8 and is indicated by the two-dot chain line in FIG. On the other hand, the light from the laser device 2 that is incident on the optical fiber 8 is emitted from the core 8 as shown by the solid line in FIG. The emitted light shown by the solid line interferes with each other. The above description applies to all the reciprocating light that is not blocked by the screen 5 provided between the parabolic mirror 3 and the plane mirror 4. The reflected light of the reciprocating light shown by the two-dot chain line in the above explanation is reflected by the parabolic mirror 3 and becomes a second parallel light, which interferes with the first parallel light generated by the output light shown by the solid line. Since the combined light is irradiated onto the screen 5, the screen 5 is also irradiated with interfering light from other reciprocating lights. Moreover, all the reciprocating lights that cause these interferences have the same phase. Therefore, a pattern of interference fringes having a semicircular outer diameter as shown in FIG. 3 is projected on the screen 5. If the mirror surface of the parabolic mirror 3 were a perfect parabolic surface, there would be no shift in phase difference due to the mirror surface of the parabolic mirror 3, and the phase of the reflected light returning from the plane mirror 4 would also change. Since there is no shift, the interference fringes projected on the screen 5 have uniform density over the entire semicircular area. This density changes by uniformly becoming thinner or darker by performing an operation such as moving the light emitting section 1 closer to or farther away from the parabolic mirror 3 using a triaxial fine movement mechanism (not shown).

If there is a distortion in the finish of the mirror surface of the parabolic mirror 3, that is, if the mirror surface of the parabolic mirror 4 has a distortion in its curvature as a paraboloid, the light will be incident on the end face of the optical fiber 8 described above. A phase shift occurs between the reciprocating lights, and the interference light between the two-dot chain line and the solid line shown in FIG. The density is no longer uniform. Therefore, a pattern of interference fringes is generated on the screen 5 depending on the degree of distortion of the mirror surface. By observing the pattern of interference fringes projected on the screen 5, the quality of the mirror surface of the parabolic mirror 3 can be inspected. If the pattern of interference fringes projected on the screen 5 has a special aspect, for example, an interference pattern of vertical stripes, the parabolic mirror 3 will not be distorted, and the rotation mechanism (not shown) provided on the parabolic mirror 3 will not be distorted. By vertically rotating the parabolic mirror 3 using a mirror (not shown), the installation posture of the parabolic mirror 3 can be corrected, and the interference pattern of the vertical stripes can be made into a single density. If the pattern of interference fringes projected on the screen 5 is, for example, horizontal stripes, the parabolic mirror may be rotated horizontally using a rotation mechanism (not shown) provided on the parabolic mirror 3. Accordingly, the installation posture of the parabolic mirror 3 can also be corrected. Based on observing the pattern of interference fringes projected on the screen 5 in this way, it is possible to determine the quality of the mirror surface of the parabolic mirror 3, that is, the distortion of the mirror surface, and also to determine the installation orientation of the parabolic mirror 3 itself. can also be modified. Note that if there is distortion on the mirror surface of the parabolic mirror 3, the interference fringes cannot be erased, so it is possible to confirm that distortion exists at the position of the parabolic mirror 3 corresponding to the point where the interference fringes remain. It shows.

FIG. 4 shows another example of the configuration of the light emitting section,
10 is a transparent medium such as glass, and the glass 1
0 has a lens 11 fixed to one side by a frame 12 that converges the laser beam emitted from the laser device 2. The parallel laser light incident on the lens 11 is converged and emitted as a point light source from the output end face of the glass 10, as shown in FIG.
The exit surface of the glass 10 is processed to be a smooth surface so that the reciprocating light indicated by the dashed-dotted line shown in FIG. 2 is reflected.

(Effects of the Invention) As explained above, according to the present invention, the roughness of the mirror surface of a parabolic mirror can be easily inspected by observing the pattern of interference fringes projected on the screen. . In addition to determining the quality of the mirror surface of the parabolic mirror, it is also possible to correct the installation posture of the parabolic mirror itself based on how the pattern of interference fringes appears, as well as to know the location of mirror distortion of the parabolic mirror. be able to.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an off-axis parabolic mirror as an embodiment of the parabolic mirror inspection device according to the present invention, Fig. 2 is an enlarged explanatory diagram of the light emitting part, and Fig. 3 is a diagram showing the structure of the off-axis parabolic mirror as an embodiment of the parabolic mirror inspection device according to the present invention. FIG. 4 shows an example of a pattern of interference fringes, FIG. 4 shows another example of the configuration of the light emitting section, and FIG. 5 shows an explanatory diagram of an inspection apparatus illustrating a conventional parabolic mirror inspection apparatus. In the figure, 1 is a light emitting part, 2 is a laser device, 3 is a parabolic mirror, 4 is a plane mirror, 5 is a screen, 7 is an optical fiber, 8 is a core, 9 is a cladding, 10 is a glass, 11 is a lens, 12 is a frame body, 21 is a parabolic mirror, 22 is a diffuser plate, and 23 is a microscope.

Claims (1)

[Claims] 1 A parabolic mirror inspection device for inspecting the distortion of the mirror surface of a parabolic mirror, which emits a laser beam from the focal position of the parabolic mirror to the parabolic mirror and generates a first parallel beam as reflected light. means for generating light, and a plane mirror disposed perpendicular to the first parallel light to reflect the first parallel light and make it enter the parabolic mirror again, and transmit the reflected light to the parabolic mirror. means for condensing the light at a focal position; and a reflecting surface disposed at the focal position perpendicular to the condensed optical axis to reflect the laser beam reflected again from the parabolic mirror at an angle equal to the incident angle. a means for generating a second parallel beam toward the plane mirror; a means disposed between the parabolic mirror and the plane mirror, the means for blocking a part of the light path between the two mirrors; A parabolic mirror inspection device comprising means for projecting interference fringes produced by interference between parallel light and the second parallel light, and inspecting distortion of the parabolic mirror from the pattern of the interference fringes. .