JPH02238338A - Lens inspecting apparatus - Google Patents

Abstract

PURPOSE:To expand the measuring range of aberration in a Hartmann type lens inspecting apparatus by making the output light-ray group from a Hartmann plate pass through a screening plate which is moved up and down and right and left, and making the input and output lights correspond in the vicinity of a focal point. CONSTITUTION:Laser light from an oscillator 1 becomes parallel luminous flux through a collimate lens 4 and reaches a separating plate (Hartmann plate) 5 having many pinholes. The light reaches a screening plate 6 through the pinhole part. The plate 6 has a mechanism which can move the plate up and down and left and right. The mechanism is controlled with a control circuit and a computer 10. The light which is not shielded with the plate 6 reaches an image sensing plane 8 of a MOS camera through a lens 7 to be measured. At this time, the position of the light point of each pinhole of the separating plate 5 is made to correspond to the position of the light point on the image sensor plane 8. Thus, the position of the light ray can be recognized even for the light-ray group which crosses in the vicinity of the focal point. Therefore, the aberration of any lens can be measured.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an aberration measuring device for an imaging system that experimentally performs ray tracing, and is particularly useful for determining pass/fail of lenses with large aberrations. This article relates to an automatic lens inspection device. [Prior art] Regarding the conventional Hartmann type lens inspection device, the method described in Obteil Shop Testing (1978) No. 323
Page to page 349 (Optical ShopTest
ing (1978) PP 323-349).

[Problems to be Solved by the Invention] The above conventional technology measures the distance from the optical axis at two points near the focal point of the light beam that has passed through the test lens, and then calculates the aberration. No consideration was given to the correspondence of the light beam positions, and there was a problem in identifying the light beam positions when the light beams crossed.

The present invention aims to recognize the position of a light ray, and further aims to enable easy and high-speed measurement of aberrations and lens performance using a simple device.

[Means to solve the problem]

In order to achieve the above objective, a shielding plate with a moving mechanism is provided, and the shielding plate can be moved in two directions, up and down and left and right, so that the position of the incident light near the focal point corresponds to the position of the outgoing light. It is also equipped with a MOS camera with a moving mechanism to measure the position of the light beam. Furthermore, it is equipped with an arithmetic processing unit to perform arithmetic processing on the imaging signal. [Function] In the present invention, the shielding plate moves in two directions, up and down, left and right, and the partition plate (
It is possible to recognize which rays of light rays emitted from the Hartmann plate pass through which position near the focal point. As a result, the position of the rays can be recognized even in a group of rays that cross near the focal point, 81! The aberrations can be measured for any lens.

[Example] A practical example of the present invention will be explained below with reference to FIG. First, I will explain the overall configuration. 1 is a laser oscillator that emits a laser beam; 2 is a microscope objective lens that focuses and diverges the laser beam from the laser oscillator 1; 3 is a pinhole that is placed at the focal point of the condenser lens 2 to remove noise due to diffraction; 4
is a collimating lens that converts diverging light into parallel light; 5 is a diaphragm (Hartmann plate) with many pinholes arranged perpendicularly in the parallel beam; 6 is a mechanism that can move in two directions, up and down and left and right, from the diaphragm. A shielding plate that scans the emitted laser light,
7 is a lens to be measured, 8 is an imaging surface of a MOS camera whose position irradiated by a large number of light beams generated by a partition plate can be identified in pixel units, 9 is a moving mechanism for moving the imaging surface, and 10 is a shielding plate 6 and an imaging surface. A control circuit for controlling the movement of 9 and a computer for arithmetic processing of the measurement results, 11 a plotter for plotting the arithmetic processing results, and 12 a printer for printing out the measurement data and calculation contents.

Next, the operation of the above-mentioned overall configuration will be explained.

Laser light emitted from a laser oscillator 1 is converged and diverged by a microscope objective lens 2. A pinhole 3 is placed at the focal point (focus point) of the objective lens 2 to remove noise light components caused by diffraction. The light converged and diverged by objective lens 2 is
The collimating lens 4, which has no aberration, converts the light into a parallel beam, which reaches the partition plate 5, which has a large number of pinholes 5', and passes through the pinholes. A large number of light beams passing through the pinhole reach a shielding plate 6, the details of which will be described later. Although not shown in the drawings, the shielding plate has a mechanism that allows it to move in two directions, up and down and left and right, and is controlled by a control circuit and computer 10. As the shielding plate 6 moves, the light rays that are not blocked by the shielding plate 6 reach the lens 7 to be measured, and if the lens 7 to be measured is a convex lens, it becomes convergent light as shown in the figure, and the MOS
It reaches the imaging plane 8 of the camera. When the lens 7 to be measured is a concave lens, the transmitted light becomes diverging light, but this is converted into convergent light by an aberration-free condensing lens and similarly reaches the imaging surface 8. Next, the imaging surface 8 is moved from point A to point B by a moving mechanism 9 controlled by control signals from a computer and a control circuit 10. Let the imaging plane at point B be 8'. The height from the optical fiber of the light spot to be measured on the imaging surface 8 at point A is hz
, B is the height from the optical axis of the light spot to be measured on the imaging surface 8' at point B. Distance Ω and hz from the intersection point F of the optical axis and the ray to be measured to the imaging surface 8 at point A
, h2 is expressed by the following equation.

h + h 2 L: A more detailed explanation of the distance between points A and B will be given with reference to FIG. 4(a), which shows only the focal point. Intersection point P with the optical axis at a certain point A on the imaging surface 8
If we take z as the origin, the Q axis along the optical axis, and the h axis perpendicular to it, the ray crosses points C and D, so PzC=
ht, PzD=hz is measured as the light spot position on the imaging surface 8. The intersection point F between the ray and the optical axis is PzF=fl (
1) It can be obtained using the formula. Furthermore, considering the best focal position (circle of least confusion or Gaussian image point) Fo, if the distance from P1 is Lo, then the distance ΔQ between Fo and F is an amount called longitudinal aberration, which is expressed by equation (2). .

Δn = Q − Lo
(2) The distance Δh from Fo to the light beam in the h-axis direction is an amount called lateral aberration, and is expressed by equation (3).

Δ Ω Ah=-h ・
...(3)Q As shown in Figure 3(a), there are many pinholes lined up in the diameter direction, and the aberrations are calculated for a line of rays with different h, and the vertical axis is h and the horizontal axis is h. 2 or Δa, an aberration curve Q (h) can be obtained. These series of arithmetic processing are performed by the computer 10, and the results are sent to the plotter 1.
1. Output to printer 12. A typical measurement example of spherical aberration is shown in Figure 4(b). An example of a mechanism for moving the shielding plate 6 in two directions, up and down and left and right, will be explained with reference to FIG. First, I will explain the overall configuration. 1
3, 14, 15, 16 are shafts for guiding the movement of the shielding plates, 13', 14', 15', 16' are pole sliders, 6 is the shielding plate, 17 is the housing, 18.19 are the shafts 13, 14 , 15, and 6, and 20.21 is a motor that is a driving source of the moving mechanism. A movement control signal from the control circuit 10 is transmitted to the motors 20 and 21.
When input to , the motors 20 and 21 rotate, and the shielding plate 6 is moved by a mechanism 18, 19 having a screw shaft (not shown) that is directly connected to the motor and rotates together with the motor shaft.

Next, the shape of the partition plate (Hartmann plate) 5 will be explained with reference to FIGS. 3 and 5. The diaphragm shown in FIG. 3(a) is a diaphragm for measuring four diameters in the radial direction.

If you want to measure the position at each point of the pinhole, you can use a shielding plate with one hole slightly larger than the pinhole in the center as shown in Figure 3(b). The shielding plate is scanned radially at each pinhole pitch. Another method is to use the shielding plate shown in Fig. 5, move the shielding plate vertically and horizontally as shown in Fig. 7, and memorize the position of the light spot in each row when moving in the vertical direction. Then, by ANDing with the light spot position data for each column when moving in the left-right direction, the positions of each light spot of the pinhole in the partition plate 5 and the time when each light ray emitted from the pinhole reaches the imaging surface 8 are calculated. The positions of are associated with each other. In the explanation so far, aberrations are measured from two light ray positions before and after the focal point of the lens to be measured, but in a lens inspection device that determines pass/fail by determining the difference from the designed ray tracing data, the diaphragm 5 It suffices to measure one point near the focal point where all the light rays passing through the pinhole reach the entire surface of the imaging surface 8.

Next, the arithmetic processing of the measurement data, which will be described in a configuration in which distortion due to spherical aberration of the surface shape of the lens to be measured is measured, is the same as that for the transmitted light aberration. FIG. 6 shows a configuration in which the surface of the lens 7 to be measured is a concave surface. The laser beam emitted from the laser oscillator 1 becomes convergent and divergent light by the objective lens 2, passes through the pinhole 3 that removes the noise component of the diffracted light, and becomes parallel light by the collet lens 4. After passing through the plate, it becomes a group of light rays,
The light is converged by the condenser lens 7', reflected by the mirror 22 and half mirror 23, reflected by the surface of the lens 7 to be measured, transmitted through the beam splitter 23, and reaches the imaging surface 8. By moving the shielding plate 6 in two directions, up and down and left and right, the pinhole position of the partition plate 5 is associated with the light spot position on the imaging surface 8, and the aberration caused by the surface shape of the lens 7 to be measured is calculated by the computer 1o. Can be measured. FIG. 8 shows a configuration in which the surface of the lens 7 to be measured is a convex surface. Laser oscillator 1
The emitted laser light is converged and diverged by the objective lens 2.

Noise light components due to diffraction are removed by the pinhole 3 and converted into a parallel light beam by the collimating lens 4, which reaches the diaphragm 5. The partition plate 5 has a large number of equally spaced pinholes.
The group of light rays that have passed through the pinhole are transmitted through the half mirror 25 and reach the surface of the lens 7 to be measured by the aberration-free condensing lens 7'. The group of light rays reflected on the surface of the lens 7 to be measured is reflected on the half mirror 25 and focused on the imaging surface 8 by the condensing lens 24.
reach. The shielding plate 6 is moved in two directions, up and down, right and left, and the pinhole position of the partition plate 5 is correlated with the position of the light beam on the imaging surface 8, and the aberration caused by the surface shape of the lens 7 to be processed and measured is measured by the computer 1o. ．． [Effects of the Invention] According to the present invention, in ray tracing using the Hartmann method, the pinhole position of the diaphragm and the light spot position on the imaging surface are correlated, so that a lens with large aberrations that causes rays to cross can be avoided. This has the effect of widening the measurement range.

Furthermore, since the arithmetic processing is facilitated by associating the light beam positions, the measurement time can be shortened.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an embodiment of the present invention, Fig. 2 is an explanatory diagram, Fig. 5 is a diagram showing an example of a partition plate, and Fig. 6 is an illustration of an embodiment in which the surface to be measured is a concave surface. FIG. 7 is a flowchart for explaining arithmetic processing for calculating aberrations, and FIG. 8 is a configuration diagram of an embodiment in which the surface to be measured is a convex surface. 1... Laser oscillator, 2... Objective lens, 3...
Pinhole, 4... Collimating lens, 5... Partition plate (Hartmann plate), 6... Shielding plate, 7... Lens to be measured, 8... Imaging surface, 9... Moving mechanism, 10...
・Control circuit and computer.

Claims (1)

[Claims] 1. An illumination means that serves as a point light source for irradiating light onto a single lens, which is an object to be inspected; a collimating lens for converting the diverging light emitted from the illumination means into a parallel light beam; A shielding plate having a diaphragm (Hartmann plate) having pinholes arranged at equal intervals in a parallel beam of light emitted from the diaphragm, and a moving mechanism for identifying the position of a group of light rays emitted from the diaphragm, the shielding plate A group of light rays whose positions have been determined are transmitted through a single lens, which is an object to be inspected, and an imaging means having a moving mechanism for recognizing the position of converging and diverging light, and processing the signals of the imaging means. A lens inspection device characterized by comprising a calculation processing means for performing calculations and a means for outputting the calculation processing results and drawing an image.