JP2899127B2 - Lens inspection apparatus and lens manufacturing method using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens inspection apparatus for inspecting the performance of a lens and a method of manufacturing a lens using the same.

[0002]

2. Description of the Related Art As a conventional lens inspection apparatus, there is a back projection type apparatus using a projector. In this method, a chart, a condenser lens, and a light source are arranged on the image plane side of a test lens, and an image of the chart is projected on a screen in front of the test lens.

This method has the advantage that the inspector can inspect the chart image of the entire screen on the screen at one time, but it is necessary to darken the entire room, which places a burden on the inspector's eyes. When the focal length of the test lens is long, at least two examiners are required on the screen side and the test lens side.
Further, a large dark room is required in terms of space, which hinders labor saving and cost reduction.

[0004]

SUMMARY OF THE INVENTION The present invention provides an apparatus for inspecting a lens which can be used in a normal living room in a factory, and further provides an apparatus which is comparable in performance to a conventional inspection apparatus. Things.

[0005]

A test chart arranged on the image plane side of a test lens, an illuminating means for illuminating the chart, and a television imaging means for imaging an on-axis position of the chart through the test lens. , A television imaging unit for imaging the off-axis position (around) of the chart, and a television monitor for observing an output image of each television imaging unit.

When focusing on the performance aspect, a chart is arranged on the image plane side of the test lens, and a light beam back-projected using a light source on the chart is imaged using an imaging lens. And a device for observing the chart image on the image sensor with a television monitor. The image forming position of the back-projected light beam is between infinity and 20f (f: focal length of the test lens). Maximum number of stripes for inspection (1
where N is the number of pixels per mm and black and white), M is the number of pixels per mm of the image sensor, and F is the focal length of the imaging lens. 3 (2N / M)> F / f> 0 .9 (2N / M), and at least an imaging lens for the chart around the optical axis of the test lens and an imaging lens for the chart around the lens.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the specific structure of the embodiment, matters related to the above-described equations will be described.

First, the image forming position of the back-projected light beam may be at infinity, but since the object distance of the best performance of the test lens is usually a finite distance, it is better to set it near the finite distance. However, it is better to be far from 20f. In this case, since a light beam in a converging state is incident on the imaging lens, the focusing of the imaging lens may be adjusted to a super infinite state.

The relationship among the maximum number of stripes on the chart, the number of pixels of the image sensor, the focal length of the test lens, and the focal length of the imaging lens must satisfy the above equation. That is, this expression is a conditional expression for efficiently resolving the stripes on the chart on the television screen. Above the upper limit, the maximum number of stripes on the chart will be resolved, but the magnification will be unnecessarily large and only a part of the chart will fit on the TV screen. Below the lower limit, the maximum number of the stripes will be resolved on the television screen. Further, the angle between the principal ray of the light beam emitted from the peripheral chart and the chart surface is θ
And when

[0010]

[Outside 1] In addition, the performance test of the test lens usually involves looking at the center and the periphery. Therefore, a minimum inspection is performed on two places (about 70% of the image sensor) at the center and the representative position (about 70% of the image sensor). At this time, it is better to make the size of the chart on the center and peripheral TV screens and the resolution state the same, so that it is better to make the focal length of the imaging lens the same.

Next, when the inspector inspects while watching the television monitor, when the performance of the test lens is poor, the chart is not resolved and a large amount of flare occurs. Here, a bad state can be determined even with a black-and-white monitor. However, when a color monitor is used, flare is colored and it is possible to determine with higher accuracy.

FIGS. 1 and 2 show the structure of the apparatus. A is a test lens. Reference numeral 1 denotes a chart for testing the resolution and the like, reference numeral 2 denotes a diffusion plate, and reference numeral 3 denotes a light source. The light source 3 and the diffusion plate 2 constitute an illumination system. A Koehler illumination system may be provided by providing a condenser lens instead of the diffusion plate 2.

Reference numeral 4a denotes an imaging lens for imaging, which receives a back-projected light beam from a chart position on the optical axis of the test lens 4 and forms an image. Reference numerals 4b to 4e denote imaging lenses that receive back-projected light beams from off-axis (peripheral) positions of the chart. Reference numerals 5a to 5e denote color solid-state imaging elements which sequentially receive images from the imaging lenses 4a to 4e. 6a to 6e
Denotes a television monitor (television receiver), which is sequentially coupled to the imaging devices 5a to 5e via a signal processing device (not shown). The imaging lenses have the same focal length, and all the imaging elements are adjusted to an equivalent distance from the chart.

The position 1 near the optical axis of the light beam from the chart 1 illuminated by the illumination light from the light source 3 via the diffusion plate 2
The light beam from a is subjected to a converging action by the test lens A, and is further imaged on the image sensor 5a by the imaging lens 4a. Next, the image is projected on the television monitor 6a and observed by the inspector.

Light beams from peripheral positions such as 1b are also imaged on the imaging device 5b and the like by the imaging lens 4b and the like, projected on the screen of the television monitor 4b and observed by the inspector, and It is used for comprehensive judgment of the inspector including the image on the monitor 6a.

FIG. 3 shows another embodiment in which a large number of TV cameras or TV monitors are arranged to improve the space requirement.

In the drawing, components having the same functions as those in FIG. 1 are denoted by the same reference numerals, and a newly added member 7 rotates the test lens A intermittently or continuously around the optical axis. A jig that supports as much as possible.

Reference numerals 8a and 8b denote mirrors for bending the optical path, which guide the on-axis inspection light beam to the imaging lens 4a arranged at a position deviated from the optical axis extension. 9a and 9b are also optical path bending mirrors. In particular, the mirror 9a is set at an angle suitable for receiving an off-axis back-projected light beam. Light beams sequentially reflected by the mirrors 9a and 9b enter the imaging lens 4b. In the case of this example, it is only possible to observe the projection chart image at one peripheral position, but by rotating the test lens A, it is possible to sequentially inspect, for example, the four corners of the imaging screen.

Instead of rotating the test lens A, a unit composed of the mirrors 9a and 9b may be rotated. In this case, the optical axis of the imaging lens 4b is arranged on the optical axis extension of the test lens A. And

FIG. 4 shows still another embodiment, in which the test lens B
Is for dealing with the case of a variable focus lens.

Although not shown, the imaging lenses 4b to 4d
The angle .theta. Directed to the periphery of the chart is changed by a mechanism for simultaneously moving the lens barrel in which the image pickup devices 5b to 5d are sequentially combined along the double-headed arrows EP10b to 10d in the radial direction and by the same amount.

Although not shown, the operation becomes more convenient if a mechanism for changing the angle θ is added in conjunction with the operation of changing the test lens B. It is preferable that the focal length of the imaging lens is also changed so as to satisfy the above-mentioned expression. FIG. 5 shows a modification of FIG. 4 replacing the form of FIG.

An oscillating mirror 9c is provided in addition to the configuration shown in FIG. 3, and this mirror 9c is provided at a position suitable for receiving back-projected light when the test lens B is set at the telephoto end. Position and retreat to the solid line position when not in use.

The first mirror 9a is provided at a position suitable for receiving back projection light when the test lens B is set at the wide end.

At the time of inspection, test lens B or unit 10
Shall be rotated.

It should be noted that if the number of oscillating mirrors is increased, inspection can be performed at many angles of view.

As described in the above embodiment, when inspecting the performance of the periphery of the test lens, the imaging lens and the image pickup device are provided at each of four places around the representative one, and five places at the same time are put together with the center. There are inspection methods. In this case, the five television monitors may be grouped in an easily viewable position. The five imaging lenses are arranged at a certain distance from the test lens so as not to interfere with each other.

Next, there is also a method in which the test lens is rotated by rotating the test lens only at one place without having four places around the periphery. In other words, only two TV monitors, the center and the periphery, may be used, but the periphery may be viewed in order with a slight shift in time. As another method, the peripheral inspection is performed by using two mirrors between the test lens and the imaging lens and rotating the mirror to inspect the peripheral periphery.

Further, when the test lens is a zoom lens, the imaging lens is also a zoom lens having a focal length range satisfying the above expression. Next, a combination of the above mirrors is prepared by the number of focal lengths to be inspected, and a mirror combination may be rotated while maintaining a certain combination of the focal length and the mirror, and the peripheral performance may be inspected.

[0030]

By using such an apparatus, it is possible to first install the apparatus in a normal bright room. Further, the test lens and the television monitor can be arranged near the examiner regardless of the focal length of the test lens. Therefore, an inspection that could only be performed in a dark room in the past can now be performed in a normal bright room, and the burden on the eyes of the inspector is eliminated. Further, the inspection can be performed by one person regardless of the focal length of the test lens.

[Brief description of the drawings]

FIG. 1 is an optical sectional view of a first embodiment.

FIG. 2 is a perspective view of the first embodiment.

FIG. 3 is an optical sectional view of a second embodiment.

FIG. 4 is a perspective view of a third embodiment.

FIG. 5 is an optical sectional view of a fourth embodiment.

[Explanation of symbols]

 A / B Test lens 1 Chart 4a-4e Imaging lens 5a-5e Solid-state image sensor 6a-6e TV monitor

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01M 11/02

Claims (7)

(57) [Claims] 1. A test chart arranged on an image plane side of a test lens, illumination means for illuminating the chart, television imaging means for imaging an axial position of the chart through the test lens, and television imaging A lens inspection having an optical path inclined with respect to an optical path of the means, a television imaging means for imaging an off-axis position of the chart, and a television monitor for observing an output image of each television imaging means. apparatus. 2. The optical path of the television imaging means for imaging the off-axis position of the chart can change the inclination angle with respect to the optical path of the television imaging means for imaging the on-axis position of the chart. 1. Lens inspection device. 3. The lens inspection apparatus according to claim 1, wherein each television imaging means is for color imaging. 4. A chart is arranged on the image plane side of the test lens,
A device for illuminating this and forming an image of the back-projected light beam using an imaging lens, arranging an image sensor on the image forming surface, and observing a chart image on the image sensor on a television monitor, The imaging position of the projected light beam is 20f from infinity
(F: focal length of the test lens), the maximum number of stripes for inspection on the chart (one per black and white per 1 mm) is N, and the number of pixels per 1 mm of the image sensor is M When the focal length of the imaging lens is F, the relationship of 3 (2N / M)> F / f> 0.9 (2N / M) is satisfied, and the imaging lens with respect to the chart of the optical axis center of the test lens A lens inspection apparatus comprising at least an imaging lens for a peripheral chart and an optical performance of a test lens. 5. The lens inspection apparatus according to claim 4, wherein the focal length of the imaging lens with respect to the chart around the optical axis and the focal length of the imaging lens with respect to the peripheral chart are the same. 6. The lens inspection apparatus according to claim 4, wherein the imaging device and the television monitor use color-compatible devices. 7. A method for manufacturing a lens, comprising manufacturing a lens using the lens inspection apparatus according to claim 1.