JPH0356419B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring the transmitted wavefront aberration of a Toric lens, and particularly to a method for measuring the transmitted wavefront aberration of a lens having a rotationally curved surface such as a cylindrical lens or a toroidal lens.

Conventionally, various interferometers such as a Fizeau interferometer and a Twyman interferometer have been used to measure the transmitted wavefront aberration of a lens.

Interferometers are generally used to measure the transmitted wavefront aberration of a lens made of a plane or spherical surface that is symmetrical about the optical axis, and the object to be measured has a surface whose generating line and sagittal line have different curvatures, such as a rotating curved surface. There are significant restrictions on measurements of cylindrical lenses and toroidal lenses. For example, FIG. 1 shows a conventional method of measuring transmitted wavefront aberration of a cylindrical lens using a Fizeau interferometer.

The laser beam emitted from the laser 1, which is a light source, becomes diverging light by the beam expander 2,
The light enters the collimator lens 4 via the half mirror 3, and after exiting the collimator lens 4, becomes parallel light and enters the reference standard 5 having a highly accurate reference plane 5-a. A portion of the light incident on the reference prototype 5 is reflected by the reference plane 5-a, returns to the original path, passes through the half mirror 3, and reaches the observation section 11, and most of the remaining light is reflected by the reference plane 5-a. -a and enters the cylindrical lens 6. The incident light becomes a convergent light 8 due to the lens action in the cross section 6-1 that includes the sagittal line of the cylindrical lens 6, and becomes a parallel light 9 in the cross section 6-2 that includes the generatrix because there is no lens action, and the focal line 7 Form. When a concave mirror 10 having a highly accurate concave shape whose center of curvature is the intersection of the focal line 7 and the collimator optical axis is arranged, a part of the light forming the focal line 7 is reflected by the concave mirror 10 and returns to the original optical path. The light returns to the observation section 11 via the half mirror 3, and interferes with the reflected light from the reference surface 5-a, forming interference fringes. The interference fringes obtained at this time indicate the transmitted wavefront aberration of one cross section in the sagittal direction of the cylindrical lens 6. In order to measure the transmitted wavefront aberration in the entire cross section, the cylindrical lens 6 or the concave mirror 10 must be It is necessary to sequentially measure the lens 6 while moving it along the generatrix direction. However, when the object is moved, the optical path length between the reference plane 5-a and the test object becomes unrelated to the previous measurement point. Even if they are combined, only interference fringes with discontinuous phase can be obtained as shown in Figure 2, and it is difficult to measure the transmitted wavefront aberration of a cylindrical lens. Things are complicated and time-consuming.

In addition, it is possible to know the transmitted wavefront aberration by continuously measuring the meridian cross section while moving, but this method requires that the optical path length difference between the reference plane and the object to be measured be within a range sufficiently smaller than the wavelength of the light. It must be held constant, and the mechanism for moving it is precise and expensive.

Another method is to use a concave cylindrical mirror instead of a concave mirror for the reflective surface, but this method has various drawbacks, such as the difficulty of machining a concave cylindrical surface with high surface accuracy. Ta.

Therefore, the present invention has been made to eliminate the above-mentioned drawbacks, and the focal line of the specimen is set to be the same as the reflected optical path for the light in the generatrix direction cross section of the specimen, and the light in the sagittal direction cross section is The reflective surface has a shape such as a flat surface or a convex spherical surface that has the effect of making the reflected optical path and the incident optical path symmetrical with respect to the normal line of the reflective surface, and can be easily manufactured with high precision. In this method, the transmitted wavefront aberration of the test object is measured from interference fringes generated by the light reflected from the reflective surface and the reference surface after the light passes through the test object.

In order to achieve the above objectives, the transmitted wavefront aberration measurement method of a Torytsu lens according to the present invention divides the light emitted from a coherent light source into two, and divides one of the two halves of the light into two different curvature surfaces in two orthogonal directions. The light after passing through the Tory lens is arranged on the focal line of the Tory lens, and the incident optical path and the reflected optical path are arranged with respect to the curvature of the Tory lens in one direction. The light is reflected so that it follows the same optical path, and for a surface of curvature in the other direction orthogonal to the one direction, it is reflected by a reflecting surface so that the incident optical path and the reflected optical path are symmetrical with respect to the normal line of the reflecting surface. , the other bisected light is reflected by a reference surface, and interference fringes are generated by guiding the test reflected light from the reflecting surface and the reference light from the reference surface to an interference pattern generation optical path; The method is characterized in that information on the transmitted wavefront aberration of the Toric lens, which is the object to be tested, is obtained.

Hereinafter, the present invention will be explained in detail based on one embodiment.

FIG. 3 shows an example of measuring the transmitted wavefront aberration of a cylindrical lens using the present invention. still,
The same numerals as in FIG. 1, which is a conventional example, represent the same parts, and the points that are different from the conventional example will be explained here. A plane mirror 12 having a plane with high surface accuracy is disposed on the focal line of the cylindrical lens 6. In the sagittal cross section 6-1 of the cylindrical lens 6, the light incident on the plane mirror 12 is reflected in a direction symmetrical to the normal to the reflecting surface, retraces its original path, and passes through the half mirror to the observation unit 11. leading to.
On the other hand, the light in the generatrix direction 6-2 is reflected by the plane mirror 12, and the reflected light follows its original path to the observation section without changing its incident direction and reflection direction. The reflected light in the generatrix direction and the sagittal direction that reaches the observation unit 11 described above is light that contains all the information of the transmitted wavefront aberration of the cylindrical lens 6, and the reflected light and the reference plane 5-
The interference fringes with the reflected light from a are the interference patterns of the transmitted wavefront aberration of the cylindrical lens 6, and since the measurement was not performed by moving the object, as shown in Fig. 4, it is a smoothly connected continuous pattern. This results in an interference pattern with characteristics.

Further, FIG. 5 shows an example in which the transmitted wavefront aberration of a toroidal lens is measured using the present invention.
13 is a toroidal lens which is a test object; 13-
1 represents a cross section of the toroidal lens 13 in the sagittal direction, and 13-2 represents a cross section in the generatrix direction. 14
is a convex spherical mirror, and the convex spherical mirror 14 has a converging point 1 of the light after passing through the toroidal lens 13 in the generatrix direction.
It has a spherical surface whose center of curvature is 5, and is arranged so that the light convergence point 16 coincides with the spherical surface in the sagittal direction.

Now, the sagittal cross section 13-1 of the toroidal lens 13
Then, the light incident on the convex spherical mirror 14 is reflected in a direction symmetrical with respect to the normal to the reflecting surface, follows the original path, and reaches the observation section via the half mirror. On the other hand, the light at the cross section 13-2 in the generatrix direction is reflected by the reflecting surface of the convex spherical mirror 14, and the reflected light follows the original path without changing the incident direction and the reflection direction and returns to the observation unit 11.
leading to. Here, the reflected light from the sagittal and generatrix directions, which includes all the information about the transmitted wavefront aberration of the toroidal lens 13, interferes with the reflected light from the reference plane 5-a, and an interference pattern of the transmitted wavefront aberration is observed. . Of course, the test object (toroidal lens 13)
Needless to say, since the interference fringes are not moved, smoothly connected and continuous interference fringes can be observed as in Fig. 4.

Note that the interference pattern of the transmitted wavefront aberration of the cylindrical lens and toroidal lens described above is
By tailing the reference wavefront of the reference light in the meridian direction and the generatrix direction relative to the reflected wavefront of the reflected light from the test object, it is possible to independently measure the transmitted wavefront aberration in the generatrix direction and the meridian direction, respectively. can.

As described above, by using the present invention, it is possible to obtain interference fringes that are smoothly connected and continuous without using special prototypes, precise moving mechanisms, or vibration-proofing mechanisms. It becomes possible to easily measure wavefront aberration.

[Brief explanation of drawings]

Figure 1 shows a method of measuring the transmitted wavefront aberration of a cylindrical lens using a conventional Fizeau type interferometer, and Figure 2 shows the transmitted wavefront aberration of each cross section obtained by conventional measurement, which has phase discontinuity. FIG. 3 is a diagram showing an example of measuring the transmitted wavefront aberration of a cylindrical lens using the present invention; FIG. 4 is a diagram showing the interference pattern of the transmitted wavefront aberration measured by the present invention; FIG. 5 is a diagram showing an example of measuring transmitted wavefront aberration of a toroidal lens using the present invention. 1...Laser, 2...Beam expander, 3
...Half mirror, 4...Collimator lens, 5
... Reference prototype, 5-a ... Reference plane, 6 ... Cylindrical lens, 6-1 ... Sagittal direction cross section, 6
-2... Cross section in the generatrix direction, 7... Focal line, 10... Concave mirror, 11... Observation section, 12... Plane mirror, 13...
...Toroidal lens, 14... Convex spherical mirror.

Claims (1)

[Scope of Claims] 1. Light emitted from a coherent light source is divided into two, and one of the two halves is irradiated onto a Toritsu lens, which is an object to be inspected, which has surfaces of curvature different in two orthogonal directions, and the Toritsu lens is The transmitted light is placed on the focal line of the toric lens, and is reflected so that the incident optical path and the reflected optical path are the same optical path for the curvature of the toric lens in one direction, and the optical path is orthogonal to the one direction. With respect to the curvature surface in the direction, the incident light path and the reflected light path are reflected by a reflecting surface such that they are symmetrical with respect to the normal line of the reflecting surface, and the other bisected light is reflected by a reference surface. By guiding the test reflected light from the reflective surface and the reference light from the reference surface to an interference pattern generation optical path, interference fringes are generated, and with these interference fringes, information on the transmitted wavefront aberration of the Toric lens, which is the test object, is obtained. A method for measuring the transmitted wavefront aberration of a Torritsu lens, which is characterized by the following: 2. The transmitted wavefront aberration measurement method according to claim 1, wherein the toric lens is a cylindrical lens, and the reflective surface is a flat surface. 3. The transmitted wavefront aberration measuring method according to claim 1, wherein the Toric lens is a toroidal lens, and the reflecting surface is a convex spherical plane. 4 A tilt is given in the generatrix direction and the meridian direction between the reference wavefront reflected from the reference surface and the test wavefront that passes through the toric lens, is reflected by the reflection surface, and returns again, and 2. The transmitted wavefront aberration measuring method according to claim 1, wherein the transmitted wavefront aberration of each of the transmitted wavefront aberrations is independently measured.