JPS61272607A - Shearing interferometer - Google Patents

Abstract

PURPOSE:To measure a three-dimensional surface shape with high accuracy by turning an optical element which performs shearing operation in two orthogonal direction by rotating mechanisms. CONSTITUTION:Two rotating mechanisms 70 each consisting of a cylindrical spindle holder 72 having a internal screw 71 at part of the inner peripheral surface, a spindle 74 having an external screw 73 engaging the internal screw, etc., are arranged for a total reflecting element. When the object surface is measured, the mirror 59 is rotated around a Z axis by a desired angle to shift the optical axis of reflected light from a beam splitter laterally and interference fringes are observed. Then, the mirror 59 is rotated around a Y axis to make a lateral shift and interference fringes are observed. Then, the residual aberrations are removed from data on those both interference fringes and a fringe analysis is taken to compute the three-dimensional shape of the object surface. Thus, the shear direction is known easily and accurately by turning the mirror in the two directions and the angle of turning of the mirror 59, i.e. shear quantity is know easily and accurately from the movement extent of the spindle 74.

Description

Detailed Description of the Invention - [Field of Industrial Application] The present invention relates to a shearing interference needle for measuring the surface shape of optical components such as lenses and mirrors, especially spherical and aspherical surfaces with high precision IIc. This ensures orthogonality in the (shift) direction and allows the amount of share to be easily determined.

[Conventional technology]

Schurling Interference Needle Co., Ltd., without using a standard reference surface.

Various types of interference needles have been proposed in the past, which divide the measured/constant wave surface into two, provide horizontal slenderness, and cause interference on their own. Examples are #! It is shown in Figure 6. This is a Matsuhachi-Zehnder type shearing interference needle that uses a fringe scanning method jointly developed by the Supervising Chemical Research Institute and V Co., Ltd. (presented at the Impaction Symposium on November 19th, 1982), and is emitted from a laser light source 11. The beam expander 12. The test surface 16 is irradiated through the beam splitters 13, 14 and the condenser lens 15. The reflected light from the test surface 16 is partially transmitted by the beam splitter 14 and partially reflected. Among them, the reflected light is given a phase change by a reference mirror 19 driven by a driving device such as a piezo element 18, and is laterally shifted by a parallel plane plate 20, and then transmitted through a beam splitter 14 and reflected by a beam splitter 13. The beam splitter 11 superimposes the beams again, causing interference. The superimposed lights are then imaged onto the imaging probe 22 by the imaging lens 21 to form interference fringes.

In this way, since the shearing interferometer uses itself as a reference plane, it is an interferometric measurement method that does not require a reference plane. In this case, the measurement result corresponds to the lateral aberration, which is the differential of the surface 16 to be measured. In addition, the number of interference fringes obtained can be adjusted by changing the shear amount (lateral shift - 1ift).
If the shear amount is kept small, the intervals between interference fringes will not become crowded and measurement will not be possible. Therefore, it is said to be advantageous for measuring optical components with a relatively large amount of aberration, especially the aspherical surface 5.

Note that when scanning the fringe by moving the total reflection g819 back and forth in steps of a fraction of a wavelength, the phases of the reference light and the test light are different from that of the total reflection mirror 1.
Since it changes according to the amount of movement of 9, it is possible to obtain an accuracy of 8 degrees per hundredth wavelength and improve reading accuracy.

[Problem that the invention seeks to solve]

Shearing interferometry observes the cross-sectional shape of the surface under test parallel to the shear direction regardless of the shear direction. Since the shape cannot be known accurately, it is necessary to perform shearing in at least two directions. It is also necessary to accurately know the share direction and share amount. However, the shearing method has not yet been sufficiently established, and therefore, it is necessary to measure the shearing direction and shearing direction each time, which is disadvantageous in that it takes time and effort to measure.

[Means for solving problems]

The sharing interference side according to the present invention was made to solve the above-mentioned problems, and includes a light source, an optical element that splits the reflected light from the test surface into two light beams, and a light source that splits the reflected light from the test surface into two light beams. an optical element that imparts transverse alignment to one of the two beams, an optical element that superimposes both of these light beams to form interference fringes, an imaging element that observes the interference fringes, and an optical element that imparts transverse alignment to one of the two light beams; The optical element is provided with a rotary IJJ mechanism that rotates the optical element in two orthogonal directions.

[Effect]

In the present invention, since the optical element that performs sharing is rotated in two orthogonal directions by a rotation mechanism, it is possible to easily measure a three-dimensional surface shape with high precision.
Also, the share direction and share amount can be easily known.

〔Example〕

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

FIG. 1 is a diagram showing an optical system of an embodiment of a shearing interference needle according to the present invention. In the figure, 50 is a laser light source, 51U light 1' adjuster, 52 total reflection mirror, 53 is a diverging lens, 54 is a beam splitter, 55 is a collimator, 56 is a condensing lens, 51 is a surface to be inspected, 58 59 is a beam splitter, 60 is a total reflection mirror, and 61 is a drive device such as a piezo element that moves the total reflection mirror 60 in the optical axis direction.
62 is a relay lens, 63 is a total reflection mirror, 64 is an imaging lens, 65 is an imaging probe, 66 is an A/'D converter, and 67 is a computer for performing fringe analysis.

In order to perform sharing, the total reflection mirror 59 is configured to rotate in two orthogonal directions due to geometry, and Figure 2 shows a state where it is tilted by an angle θ in the plane of the paper. This gives a share amount S. Similarly, the plane perpendicular to the plane of the VC paper is also tilted.

In the shearing interference needle with such a configuration,
The luminous flux emitted from the laser light source 50 is 1 kV of light! The light is reflected by the p-total reflection mirror 52 through the 4 rectifier 51, and is converted into diverging light by the diverging lens 53.

This diverging light is reflected by the beam splitter 54,
After the beam is converted into a semi-linear beam by a collimator 55, it passes through a condensing lens 56 and irradiates a surface to be inspected 57. The reflected light from the test surface 51 is collected by a condenser lens 56. The light passes through the collimator 55 and the beam splitter 54, and is partially transmitted and partially reflected by the beam splitter 58. The transmitted light is reflected by a total reflection mirror 60 driven by a drive device 61 such as a piezo element, and returns to the beam splitter 58 again. Also,
The reflected light reflected by the beam splitter 5BVC is laterally shifted by the social reflector 59, returns to the beam splitter 58 again, and is superimposed with the reflected light from the total reflector 60, causing interference. This superimposed light flux passes through the relay lens 62, is reflected by the total reflection mirror 63, and is imaged onto the image sensor 65 by the imaging lens 64, forming interference fringes. The interference fringes are formed by the image sensor 65.
fCaA/ is converted into an electrical signal as image information by
It is converted into a p-digital signal by a D converter 66 and sent to a computer 67. The computer 67 removes residual aberrations specific to the interferometer from the image information and performs fringe analysis to calculate the surface shape of the test surface 51. This residual aberration is unique to the interferometer and is added to the measured value instead of requiring a standard reference surface in the shearing interference needle.By removing this residual aberration, measurement accuracy is improved. .

In addition, in order to measure surface shapes such as spherical and aspherical surfaces, it is necessary to use shear data in two orthogonal directions, and in order to eliminate residual aberrations, it is necessary to share data without changing the optical system of the interference needle. There is.

Figure 3 shows a total reflection mirror 59 to perform such sharing.
FIG. 3 is a cross-sectional view showing an example of a rotation mechanism arranged in the same manner as in FIG. This rotating device 1170 is a spindle holder 1 that is formed in a cylindrical shape and has a female thread 11 formed on a part of its inner peripheral surface.
2, and a spindle 74 which is inserted into this spindle holder 12 and has a male thread 13 formed on a part of its outer periphery to be screwed into the female thread 11. It is configured to press one side edge and rotate about its rotation center 0. Therefore, depending on the amount of movement of the spindle 14, total reflection *59
The rotation angle, in other words, the share amount can be easily determined.

In this case, a plurality of grooves 15 that are long in the monopole direction are formed on the inner circumferential surface of the spindle holder 72 at predetermined intervals in the circumferential direction, and steel balls 11 are correspondingly arranged on the spindle 74. Good too. The steel balls 17 are disposed in four parts 16 formed on the outer periphery of the spindle 14 so as to be freely retractable, and are prevented from coming off.
By being biased in the protruding direction by the cover spring 7B, a part of the p is protruded to the outside and fitted into one of the #175, thereby giving a click feeling when the spindle 14 moves back and forth. I have to. It is clear that in such a configuration, the total reflection f#59 can be rotated stepwise by a constant angle. In yet another embodiment, the spindle 74 may be moved forward and backward by a cam 80, as shown in FIG.

The rotation direction of the total reflection mirror 590 is y as shown in diagram M5.
It is rotated by a minute angle around the two axes. Therefore, the rotation mechanism γ0 described above for the total reflection mirror 59 is 2
One is provided. When measuring the surface to be measured 57, first, the total reflection mirror 59 is rotated by a desired angle around two axes to horizontally shift the optical axis of the reflected light from the beam splitter 58 (Fig. 1), and interference fringes are observed. do. At this time, a cross-sectional shape parallel to the y-axis of the surface to be inspected 57 is obtained. Next, the total reflection mirror 59 is rotated about the y-axis and shifted laterally.

Observe interference fringes. Then, the convex three-dimensional shape of the test surface 51 is calculated by removing the aforementioned residual aberration from the data of these two interference fringes and performing fringe analysis.

Thus, according to the shearing interferometer having such a configuration, since the total reflection mirror 59 is rotated in two orthogonal directions (r and z directions), the shearing direction is determined by the direction of rotation. This can be easily and accurately determined, and the rotation angle of the total reflection mirror 590, in other words, the shear sensitivity can be easily and accurately determined based on the amount of movement of the spindle 14. In addition, by rotating the total reflection mirror 59 around the y-axis and two axes, orthogonality in the shear direction is guaranteed, so the surface to be inspected 5
7 can be measured with high precision.

Note that the present invention is not specified in any way by the above embodiments;
The optical system 1 rotation mechanism 10 of the interferometer can be changed as appropriate.

〔Effect of the invention〕

As explained above, the shearing interference needle according to the present invention is configured to rotate in two orthogonal directions by the full rotation mechanism of the base rope that performs shearing, so the three-dimensional surface shape can be formed with high precision. Since it can be measured and the rotation direction is specified, the shear direction can be easily known1, and the amount of shear air can also be easily determined based on the rotation angle.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the optical system of an embodiment of the present invention, Fig. 2 is a diagram showing the shear density due to the rotation of the total reflection mirror, Fig. 3 is a sectional view of the rotation mechanism, and Fig. 4 is a diagram showing the rotation of the total reflection mirror. FIG. 5 is a side view showing another embodiment of the mechanism; FIG. 5 is a perspective view showing the direction of rotation of the total reflection mirror; FIG.
The figure shows the optical system of a conventional Matsuha-Zehnder type shearing interferometer. 50...Laser light source, 54.58...Beam splitter, 55...@Φ collimator, 56...Condensing lens, 51...Test surface, 59.60... Total reflection mirror, 70... Rotating mechanism.

Claims (1)

[Claims] A light source, an optical element that splits the reflected light from the test surface into two beams, an optical element that applies a lateral shift to one of these two beams, and an optical element that superimposes both beams to form interference fringes. an image sensor that observes the interference fringes;
A shearing interferometer characterized by comprising: a rotation mechanism for rotating the optical element in two orthogonal directions for imparting a lateral shift to one of the two light beams.