JPS61275637A - Inspecting device for optical system - Google Patents

Abstract

PURPOSE:To improve measurement precision by arranging a linear slit so that the direction of the groove coincides with the direction of a grating, and emitting impulsive illumination light periodically while moving the slit on the surface of the grating at an equal speed at right angles to the groove. CONSTITUTION:The rays of light from a spot light source 1 are passed through a chopper 7 and collimated by a collimator lens 2 into parallel light to illuminate a lens 3 to be inspected and the rays of light passed through this lens 3 are projected on a screen 4 through the slit 4. Then, the slit is shifted in position by (d) and the light passed through the slit 4 is projected on the screen 5 similarly. The chopper 7 is driven with a synchronizing signal from a slit moving device so as to cut off the light in the middle of the movement of the slit 4. This operation is repeated at every time the slit 4 is shifted in position by (d) to obtain a Ronchi-gram equivalent to that obtained by using a Ronchi grating which has grating intervals (d) and 1/(VT) fringes per unit length, thereby improving measurement precision.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an optical system inspection device using the Ronchi method.

[Conventional technology]

Fig. 3 is a diagram of the configuration of the optical system used to inspect lens aberrations using conventional inspection equipment. , collimating lens for making light, (31a test lens, (
4) is a Ronchi lattice, (5) is a screen, and (6) is a Ronchi duram.

As is well known, Ronchi-Dalam (6) exhibits a unique shape depending on the spacing and number of Ronchi gratings (4), the installation position, and the aberration of the lens to be tested (3), so it is necessary to analyze Ronchi-Dalam (6). From K, test lens (3)
The aberration can be found.

[Problem that the invention seeks to solve]

As mentioned above, conventional devices use Ronchi lattices to obtain Ronchi durams. A Ronchi lattice is a grid of straight slits arranged in parallel at equal intervals. In order to easily maintain the linearity of each slit at 8 intervals and the flatness of the entire grating, it is often constructed using black paint or aluminum vapor deposition on a glass plate. In addition to the need for preparation, there was a drawback that precise measurements were affected by the glass plate.

This invention was made to solve these problems, and it is an object to obtain an optical system inspection device equivalent to the case using an ideal Ronchi grating in which the grating interval is variable and the influence of glass is eliminated. With the goal.

[Means for solving problems]

In the optical system inspection device according to the present invention, a precise linear slit is placed in the Ronchi grating edge 5 at the position where the Ronchi grating is placed so that the direction of the groove coincides with the direction of the grating. While moving the slit at a constant speed, the pulsed illumination light is turned on periodically.9.

[Effect]

In this invention, the moving speed of the slit? I#V.

If the slit width is d and the lighting period of the illumination light is T, then the grating interval d is equal to the unit length! 71Ayfr) is equivalent to using a Ronchi lattice. Since a single linear slit can be easily made with high precision, the resulting isometric Ronchi lattice has high precision and can eliminate the effects of glass.

〔Example〕

FIG. 1 is a configuration diagram of an optical inspection apparatus showing an embodiment of the present invention, in which (1> is a point light source, (2) is a collimating lens, (3) is a test lens, (4) is a point light source, (2) is a collimating lens, (3) is a test lens, ii Misrit (5) is screen, (6) is Ronchigram, (7)
is a chopper, and (8) is a slit moving device.

Figure 2 is an enlarged view of the slit (4) of this invention (9
) is a base with a hole in the center, αG is a knife; αD is a fixing fitting for attaching the two knife blades to the base (9) while maintaining a constant interval.

Next, the operation will be explained. In FIG.

The light emitted from the point light source (1) passes through the chopper (7) and is converted into parallel light by the collimating lens (2) and sent to the test lens (
3), and the light that has passed through the test lens (3) is projected onto the screen (4) through the slit (4). Next, move the slit by [(L) and similarly project the light passing through the slit (4) onto the screen (4).The slit (
4) drives the chopper (7) by a synchronizing signal from the slit moving device (8) so that the chopper (7) cuts off the light during the movement. By repeating this operation while shifting the position of the slit (4) by d, a Ronchigram equivalent to that obtained when a Ronchi lattice with a lattice spacing of d is used is obtained. However, the width of the slit must be less than or equal to Ha; if it is -, it will be equivalent to a Ron-Imaichi lattice with the same width for black and white. When the moving speed of the slit (41) is V, and the rotational frequency of the chopper (7) is D, the slit (41)
) can irradiate light every time the position fl (l) moves.

Incidentally, in the above description, the case where the illumination light is blinked using a mechanical chopper has been described, but it goes without saying that other methods may be used to blink the illumination light.

〔Effect of the invention〕

As described above, the present invention uses glass for the transmitting portion, and a slit with a sharp edge can be used, so a clear Ronchigram can be obtained, and measurement accuracy is improved. Furthermore, since the grating spacing can be changed arbitrarily, there is no need to provide several types of Ronchi gratings in order to select a grating spacing suitable for measuring the aberration of the lens to be tested. In addition, in the case of a normal Ronchi grating, the light passing through each slit is mutually coherent, but in the case of the device according to the present invention, the light is incoherent, and calculation when obtaining a Ronchi gram using nine-wave optics is easy.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an optical system inspection apparatus showing an embodiment of the present invention, FIG. 2 is an enlarged view of a slit of the present invention, and FIG. 3 is a block diagram of a conventional inspection apparatus. In the figure, (1) is a point light source, (2) is a collimating lens, (31 is a test lens, (4) is a slit or Ronchi grating, (5) t; E screen, (6)
T! (7) is a chopper, (8) is a slit moving device, (9) is a base, a is a knife, and (D is a fixing metal fitting.) In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] In an optical system inspection device using the Ronchi method, instead of the Ronchi grating, a linear slit with a variable width is placed so that the direction of the groove matches the direction of the grating, and the grooves are formed in the grating plane. The illumination light is turned on periodically while moving the slit in the direction perpendicular to
, where the moving speed of the slit is v and the time period of illumination light lighting is T, the Ronchigram is equivalent to using a Ronchi grating with a grating spacing of d and the number of lines per unit length being 1/(vT). An optical system inspection device characterized in that: