JPH037254B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hologram shearing interferometer for measuring lateral aberration of a lens using hologram shearing interferometry. The present inventor previously developed a hologram shearing interferometer that measures the lateral aberration of a lens using two three-beam holograms. This holographic shearing interferometer is shown in FIG. This first
In the hologram shearing interferometer 1 shown in the figure, it is first necessary to prepare holograms H1 and H2.
Figure 1a shows an optical system for creating a hologram, and the hologram H1 in the figure is a parallel beam fH2, fH
+△) was recorded by double exposure using the reference beam fH1 as the object beam. Hologram H2 is reproduced by parallel light fH2, fH illuminated by fH1 on hologram H1.
Using (2+△) as a reference beam, parallel object beam
It was created by double exposure recording fH3. A hologram shearing interferometer 1 is completed by adding an optical system as shown in FIG. 1b to the holograms H1 and H2 thus produced.

Hologram shearing interferometer 1 with such a configuration
When inspecting the lens LT to be tested, as shown in FIG. 1b, the hologram H1 is illuminated with substantially parallel light (deviated from parallel light by the amount of aberration) from the lens LT to be tested. Two lights are reproduced from the hologram H1, and these reproduced lights reach the hologram H2. The reproduction light is light in which fH2 and fH(2+Δ) are distorted by the aberration of the lens LT to be tested.
Furthermore, these lights illuminate the hologram H2 to obtain reproduction light. These reproduced beams have fH3 of the tested lens.
They are distorted by the aberration of LT, and are laterally shifted from each other. The shearing interference fringes caused by the reproduction light of this hologram H2 are observed on the screen Sc to obtain the shearing interference fringes of the lens to be tested LT.

However, to find the amount of transverse aberration of a lens from such shearing interference fringes, the optical path difference is the difference in wavefront aberration with the shear amount d as the step difference, so it is necessary to find the wavefront aberration sequentially by representing numerical values. However, each time the lens to be tested changes, it takes a lot of effort and time to read, calculate, and plot the interference fringes.

This invention was made in view of the above circumstances, and in order to obtain the aberration curve of a lens,
To provide a hologram shearing interferometer for measuring lens lateral aberration, in which the shearing interference fringes themselves directly give an aberration curve, and therefore, the lens lateral aberration can be immediately determined without requiring complicated processing or calculation. The purpose is to In response to this purpose, the hologram shearing interferometer for measuring lens lateral aberration of the present invention records interference fringes between two parallel beams fH2 and fH (2+△) and a reference beam fH1 illuminated through a collimator lens by double exposure. the first hologram H1 that has been
Parallel light fH2 and reference light fH3 of and fH(2+△)
Interference fringes between the parallel light fH (2+△) and another reference light fH (3+△) obtained by rotating the reference light fH3 around an axis parallel to the shearing direction. A test lens, which is an object to be measured, is placed at the position of the collimator lens, and the hologram H2 is illuminated through the test lens, and the hologram H2 is illuminated with the reproduction light of the hologram H2. illuminate the
It is characterized in that it is configured to observe interference fringes formed by the reproduction light of the hologram H2.

The details of this invention will be explained below with reference to the drawings showing one embodiment.

In FIG. 2, reference numeral 11 denotes a hologram shearing interferometer for measuring lens lateral aberration, and the hologram shearing interferometer 11 for measuring lens lateral aberration includes a hologram H1 and a hologram H2. First, the production of these two holograms H1 and H2 will be explained.

In FIG. 3, 12 is a hologram H1, H2
This is an optical system for manufacturing. The optical system 12
He-Ne laser light source Ls, mirrors M1 to M6, beam splitters BS1 and BS2, microscope objective lenses MO1 to MO3, collimator lenses L1 to L
2, L5 to L7, and a spatial frequency filter STP1.

When creating a hologram H1, the object beam fH2
is exposed and recorded on the hologram H1 with the reference beam fH1, and the object beam fH(2+Δ) is exposed and recorded with the reference beam fH1, and then developed. Object light fH (2
+Δ) is obtained by changing fH2 slightly by slightly rotating the mirror M3 to slightly change the incident angle of the hologram H1.

The object beam fH2 is obtained by splitting the laser beam from the He-Ne laser light source Ls by the beam splitter BS1, and then splitting the laser beam from the He-Ne laser light source Ls into the microscope objective lens MO1 and collimator lens L5.
The parallel light is made into parallel light and reflected by mirrors M4 and M3. On the other hand, the reference light fH1 is a laser beam from the He-Ne laser light source Ls, which is passed through the microscope objective lens MO2, the mirror M2, and the collimator lens L6.
It is made into parallel light.

When creating hologram H2, when hologram H1 is illuminated with reference beam fH1, object beams fH2 and fH
(2+△) is reproduced, so the object beam fH3 is exposed and recorded on the hologram H2 using the reproduction beam fH2 as a reference beam, and the object beam fH(3+△) is reproduced using the reproduction beam fH(2+△) as a reference beam. is recorded on the hologram H2 by double exposure. The reproduced beams fH2 and fH (2+△) are configured to pass through an optical system including collimator lenses L1 and L2, and the spatial frequency filter (pinhole) STP1 is placed at the focal point of the lens L1. Move this horizontally and reproduce the light fH2
It is possible to pass only the reproduced light fH (2+△). This will be convenient when producing the hologram H2 by double exposure recording. On the other hand, the reference beam fH3 is He−Ne
After the laser light from the laser light source Ls is split by the beam splitter BS2, it is sent to the microscope objective lens.
It is made into parallel light by MO3 and collimator lens L7, reflected by mirrors M6 and M5, and then illuminates hologram H2, and reference light fH
(3+Δ) is the case where the incident angle of the hologram H2 is slightly different by rotating fH3 around an axis parallel to the direction that slightly shears the mirror M5.

Holograms H1 and H2 produced in this way
are arranged as shown in FIG. 2 to complete the interferometer 11. That is, the He-Ne laser light source Ls, mirror M1, microscope objective lens MO2, mirror M2, hologram H1, and collimator lens have the same configuration and position as in the optical system shown in FIG. 3 when producing holograms H1 and H2. L1, spatial frequency filter STP1, collimator lens L2
and a hologram H2, and a hologram H2
A collimator lens L3, a spatial frequency filter STP2, a collimator lens L4, and a screen Sc are provided behind the.

In the hologram shearing interferometer 11 for lens lateral aberration measurement with such a configuration, the test lens TL
When trying to measure the lateral aberration of
Collimator lens L6 when creating parallel light of fH1
Instead, the test lens TL is placed and the hologram H1 is illuminated. As a result, object beams fH2 and fH(2+△) are reproduced from the hologram H1, and when these beams further reach the hologram H2, fH3,
Regenerate light of fH (3+△). However, fH2, fH
(2+Δ), fH3, and fH(3+Δ) at this time differ from the parallel light by the aberration of the lens TL to be tested.
When observing the interference fringes formed by the light of fH3 and fH (3+△) on the screen Sc, as shown in Figure 4, interference fringes between the normal shear and the tailed wavefront due to the rotation of mirror M5 are observed. Ru. This corresponds to measuring the phase difference due to shear by the lateral shift of the tailed interference fringes, and the interference fringes passing through the center of the field of view become the lateral aberration curve shown in FIG. The scale of the coordinates in this case is determined by calculation in order to match the aberration curve.

As is clear from the above explanation, in the hologram shearing interferometer for measuring lens lateral aberration of the present invention, the shearing interference fringes are made to directly form the aberration curve by utilizing the lateral shift of the interference fringes caused by tailing, so that the shearing interference fringes directly become the aberration curve. No complicated operations or calculations are required to determine the lateral aberration of a lens from interference fringes. Also, since two holograms are used,
It is possible to correct aberrations in optical systems such as lenses and mirrors used in interferometers. Furthermore, by using a hologram, it is possible to correct aberrations of a lens with a small F number. In addition, it is easy to observe interference fringes, the field of view is large, and the hologram can be moved to change the amount of shear to adjust accuracy, and the hologram can be subjected to multiple exposure to achieve another set of shearing interference. By doing so, it is also possible to create an interferometer that simultaneously observes shear in two directions perpendicular to each other.

[Brief explanation of drawings]

Figure 1 is a configuration diagram showing a conventional hologram shearing interferometer for measuring lens lateral aberration, Figure 2
Figure 3 is a configuration diagram showing a hologram shearing interferometer for measuring lens lateral aberration of the present invention, Figure 3 is a configuration diagram of an optical system for producing a hologram, Figure 4 is an explanatory diagram showing interference fringes, and Figure 5 is a diagram showing lateral aberration. It is a graph showing a curve. 11...Hologram shearing interferometer for lens lateral aberration measurement, 12...Optical system, H1, H2...Hologram, Ls...He-Ne laser beam, M1-M6...Mirror, BS1-BS2...Beam splitter, MO
1 to MO3...Microscope objective lens, L1 to L7...Collimator lens, STP1 to STP2...Spatial frequency filter, Sc...Screen, LT...Test lens.

Claims (1)

[Claims] 1. A first hologram H1 in which interference fringes between two parallel beams fH2 and fH(2+△) and a reference beam fH1 illuminated through a collimator lens are recorded by double exposure;
The reference light for the first hologram H1
Parallel light of the two parallel lights fH2 and fH (2+△) reproduced by illumination light from the direction of fH1
Interference fringes between fH2 and reference light fH3 and the parallel light fH
(2+△) and another reference light obtained by rotating the reference light fH3 around an axis parallel to the direction of shearing.
The second double exposure recording of interference fringes with fH(3+△)
A test lens, which is an object to be measured, is placed at the position of the collimator lens, and the hologram H1 is passed through the test lens.
A hologram shearing interference for measuring lateral aberration of a lens, characterized in that the hologram H2 is illuminated with the reproduction light of the hologram H1, and interference fringes formed by the reproduction light of the hologram H2 are observed. Total.