JP2002005853A - Lens inspecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inspect an object to be inspected quickly without moving it. SOLUTION: A laser light from a laser light source 1 is scanned two- dimensionally and is made incident on a lens L to be inspected. A turning rotary diffusion plate 12 is irradiated with a luminous flux emitted from the lens L. A transmission image from the lens L, projected onto the rotary diffusion plate 12, is formed on a one-dimensional CCD sensor 16 via an image rotation element 14. The angle of rotation of the image rotating element 14 is monitored by a rotation sensor 18 and the resulting information is sent to a computer 20. With the rotation of the image rotating element 14, the signal of the one- dimensional CCD sensor 16 scans the image projected on the rotary diffusion plate 12 being rotated about the optical axis, to obtain an image in the so-called rθ coordinate system. The image thus obtained undergoes image processing by an image processor 19, and defect information is transmitted to the computer 20. The propriety of the lens L is made from the defect information obtained by the computer 20.

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 optically determining defects of optical components such as glass and lenses.

[0002]

2. Description of the Related Art Conventionally, a transparent object such as a lens is often inspected by visual inspection of a human in many cases. In recent years, an automatic inspection apparatus has been developed which uses a reflected light inspection, a transmitted light inspection, or the like optically according to the state of a defect.

There are roughly two flows of an optical automatic inspection apparatus. One is to irradiate the light to be inspected with the light emitted from the light source and measure the transmitted light as an image to determine the defect. The other is to measure the reflected light from the object to be imaged. This is a defect determination method. In any case, the devices used are various, and there are many combinations. For example, there is a method of detecting a surface defect by detecting particularly a scattered component of the reflected light by a laser beam as disclosed in Japanese Patent Application Laid-Open No. Hei 5-322694, Optical inspection may be performed.

[0004] Further, unevenness of the intensity distribution of the illumination light is also a major problem. Conventionally, unevenness is reduced by reducing the illuminance distribution of the light source itself, or by dividing a light beam into wavefronts and superimposing them on an image plane. Also, Japanese Patent Application Laid-Open No. 5-189
In Japanese Patent Publication No. 00, a light beam is incident on a defect inside the lens from a direction perpendicular to the optical axis, and the presence or absence of an internal defect is inspected from the scattered light.

[0005]

However, in the above-mentioned prior art, when laser light is used for detecting transmitted light, an interference pattern called speckle noise occurs due to the coherence of the laser light. Since this speckle noise is an interference pattern caused by irregularities on the order of the wavelength of an object, it is common to remove the noise by integrating images having different interference patterns a plurality of times to smooth the interference pattern. is there.

In an inspection using a two-dimensional CCD, the accumulation time is relatively long, 30 msec, and it is possible to integrate images by various methods. For example, there is a technique of moving illumination light to smooth noise by background light using various illumination patterns, or smoothing by adding and averaging independent background lights obtained from a plurality of light sources. But,
When a one-dimensional CCD is used for speeding up, the accumulation time is shortened to 0.05 to 2 msec, and the method for integration is limited.

In many cases, a plurality of minute lenses are collectively placed in a dedicated tool called a pallet. The inspector visually inspects all at once, but does not look at each one by hand. This also has the purpose of preventing scratches from occurring during handling. In other words, the inspection object does not take out the inspection object from the pallet
Furthermore, it is necessary to inspect without moving the pallet itself.

When the light source is divided into wavefronts and overlapped to reduce the illuminance distribution of the illumination light, a plurality of light source images exist. In the method of detecting a shadow caused by a defect, signals generated by the respective light sources are integrated on a screen to be detected. However, since the angles are different, the contrast of the defect signal may be degraded. In particular, in the case of a defect having a small size, diffracted light of the defect itself is generated, and when they overlap, the defect contrast is further deteriorated. For this reason, the signal detection is deteriorated, and a defect is overlooked.

An object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a lens inspection apparatus capable of quickly inspecting an object without moving the object.

[0010]

According to a first aspect of the present invention, there is provided an illumination optical system for illuminating an object to be inspected, wherein two deflectors are provided to transmit light from the object to be inspected. A lens inspection apparatus characterized in that an image rotation element for rotating an image is provided in an image forming optical system for forming light on an image pickup element.

According to a second aspect of the present invention, the two deflectors include a one-dimensional deflector for scanning an incident light beam in a one-dimensional direction and a circumferential deflector for scanning in a circumferential direction around an optical axis. A lens inspection device according to claim 1.

According to a third aspect of the present invention, the two deflectors include a first deflector and a second deflector, and the two deflectors are gathered near the reflecting surface of the first deflector by an incident optical system of the first deflector. A light spot is formed, and a condensing point near the reflection surface of the first deflector is adjusted by a lens system having a positive power provided between the first deflector and the second deflector. 2. The lens inspection apparatus according to claim 1, wherein an image is re-formed near the reflection surface.

The invention according to claim 4 is the lens inspection apparatus according to claim 2, wherein the reflecting surface of the circumferential deflector is not orthogonal to the rotation axis of the circumferential deflector.

According to a fifth aspect of the present invention, an optical system for capturing an image of a screen which reflects transmitted light transmitted from the object to be inspected is constituted by an infinite optical system comprising two lens groups. The lens inspection apparatus according to claim 1, wherein the image rotation element that rotates an image around an optical axis is provided between two lens groups.

The invention according to claim 6 is the lens inspection apparatus according to claim 5, wherein a diaphragm of a lens system constituted by the two lens groups is provided inside the image rotation element.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail based on the illustrated embodiment. FIG. 1 is a configuration diagram of the present embodiment. In the emission direction of the laser light source 1, a shutter 2 for turning on / off the laser light source 1, an ND filter 3 for adjusting the amount of light, a polarizing filter 4, a beam expander 5 for expanding a beam, a reflection mirror 6, and a condenser A lens 7, a movable deflecting mirror 8 for deflecting a light beam, a convex lens 9, a rotating / reflecting mirror 10 for rotating a reflected light beam, an aperture mask 11, a lens L to be inspected, a rotatable rotating diffusion plate 12,
An image forming lens 13, an image rotating element 14, an image forming lens 15, and a one-dimensional CC for forming an image reflected on the rotating diffusion plate 12.
D sensors 16 are arranged.

The rotation reflecting mirror 10 is provided with a rotation sensor 17 for monitoring its rotation, and the image rotation element 14 is provided with a rotation sensor 18 for monitoring its rotation. The output of the one-dimensional CCD sensor 16 is connected to a computer 20 via an image processing device 19, and the computer 20 has a shutter 2 and a rotation sensor 1
7, 18 are connected.

The light beam emitted from the laser light source 1 passes through the shutter 2 while maintaining a state parallel to the optical axis, and then enters the ND filter 3 and the polarization filter 4. The examiner watches the signal of the one-dimensional CCD sensor 16 and
ND with appropriate transmittance characteristics so that the
The filter 3 is selected. In the present embodiment, the ND filter 3 is an absorption type filter.

The polarization filter 4 selects an appropriate one by judging the state of the defect. In the case of a dirt or foreign matter defect, there is a polarization dependence depending on the target object. In such a defect, the polarization of the laser light source 1 used may not be detected by signal processing unless a signal appears better for the defect. Conceivable. For this reason, it is considered preferable that the illumination light be circularly polarized light and have no dependency on defects.

Alternatively, when the detection conditions for the defect are confirmed, if there is no difference in the polarization dependence between the various types of defects, detection may be performed under the condition of the best linearly polarized light. The polarizing filter 4 is appropriately selected by performing such a defect determination check.

The light beam emitted from the polarizing filter 4 is expanded by a beam expander 5 and reflected by a mirror 6 before reaching a condenser lens 7. The focal length of the condenser lens 7 is determined by the angle of the light beam illuminating the lens L to be measured and the magnification determined by the imaging relationship of the convex lens 9.

In the present embodiment, the movable deflection mirror 8 is a galvanometer mirror, and the light beam is deflected in one-dimensional direction by the operation of the movable deflection mirror 8. However, since the condensing point of the condensing lens 7 is near the reflecting surface near the center axis of rotation of the movable deflecting mirror 8, the deflected light beam is as if it were a light beam emitted from a point light source. The convex lens 9 relays a focal point formed near the reflecting surface of the movable deflection mirror 8 to near the reflecting surface of the rotating mirror 10. When this relationship is established, the light beam reflected by the rotating mirror 10 appears to be emitted from the point light source.

The rotating mirror 10 is formed by depositing a reflective material on a prism inclined surface having a certain angle so that a light beam can be reflected. The normal direction and the optical axis of the reflecting surface of the rotating mirror 10 are 45
Unlike ゜, the light reflected by the rotating mirror 10 is no longer a light beam symmetric about the optical axis. This shift amount is determined in consideration of the size of the test lens L, the single radiation angle of the reflected light, the luminance distribution, and the like so that the distribution illuminating the test lens L is uniform. The rotation axis of the rotation mirror 10 rotates around an axis perpendicular to the back surface, which is the back side of the reflection surface. The reflection surface and the back surface have an angle to shift the reflected light beam,
Not necessarily parallel.

In this state, when the rotating mirror 10 is rotated about an axis perpendicular to the back surface, the light beam reflected by the reflecting surface of the rotating mirror 10 becomes a new optical axis in which the optical axis of the incident light beam is bent by 90 °. The luminous flux rotates around while maintaining the shift amount. The reflecting surface of the movable deflecting mirror 8 moves so as to scan the reflected light beam in a one-dimensional direction.

Considering this effect together, the rotating mirror 1
The light beam reflected from 0 rotates while maintaining the shift amount with respect to the new optical axis, and the light beam is simultaneously scanned. The rotation of the rotating mirror 10 is monitored by a rotation sensor 17 and used for synchronizing with another control system.

Here, the magnification caused by the convex lens 9 is m, the focal length of the condenser lens 7 is fl, the magnitude of the light beam incident on the condenser lens 7 is w, the deflection angle of the movable deflection mirror 8 is a, and the rotating mirror is Assuming that the distance from the center of 10 to the aperture mask 11 is s, the illumination range on the aperture mask 11 is R, and the illumination scan width (movement amount of the illumination center of gravity) on the aperture mask 11 is b, the relationship is as follows. It is expressed by the following expression. Note that m '
Is the absolute value of the magnification m.

R = (w · s) / (m ′ · f1) b = (2 · s · a) / m ′

Actually, since the laser light source 1 has an intensity distribution, the illumination range,
The illumination scanning width will be appropriately selected.

The light beam reflected from the rotating mirror 10 passes through the aperture mask 11 and enters the lens L to be measured. The aperture mask 11 limits a light beam emitted from the non-inspection range of the lens L to be inspected. The light beam emitted from the test lens L is applied to the rotating diffusion plate 12. The rotating diffusion plate 12 is rotatable around the optical axis, and is always rotating at the time of inspection. Glass is used as the material of the rotary diffusion plate 12 and is
It is used on a sand surface in the range of No. 000, and its rotation speed is about 600 rnm. Extremely high rotation speed (1-
Unless 10 rpm) is small, there is no significant change in the obtained image. The position of the rotary diffusion plate 12 on the optical axis is located closer to the lens L than the image forming point generated by the lens L. The transmitted image from the test lens L projected on the rotating diffusion plate 12 is converted into one-dimensional CC by the imaging lenses 13 and 15.
An image is formed on the D sensor 16.

The imaging lenses 13 and 15 constitute an imaging system of an infinite circular focus system, and are designed so as to have a stop surface inside the image rotation element 14. The image rotation element 14 transmits an image by an odd number of light beam reflections. In this embodiment, a roof prism is used.
As the whole 4 rotates around the optical axis, the transmitted image rotates around the optical axis.

The rotation angle of the image rotation element 14 is monitored by a rotation sensor 18, and information is sent to a computer 20. When the image rotation element 14 rotates, the signal of the one-dimensional CCD sensor 16 rotates and scans the image reflected on the rotary diffusion plate 12 around the optical axis, and an image in a so-called rθ coordinate system is obtained. In this system, the reading cycle of the image rotation element 14, the rotating diffusion plate 12, and the one-dimensional CCD sensor 16 is related. The rotation cycle of the image rotation element 14 is t14, the rotation cycle of the rotating diffusion plate 12 is t12, and the one-dimensional CCD sensor 16
It is necessary that the following relationship be satisfied when the read cycle of is set to t16.

T14 = t16 / n (n: integer) t12 = t16 / m (m: integer)

The obtained image is subjected to signal processing by the image processing device 19, and the defect information is transmitted to the computer 20. The computer 20 controls on / off of the shutter 2 for controlling the laser light source 1, information on the rotation sensor 17 of the rotation mirror 10, information on the rotation sensor 18 of the image rotation element 14, and the like, while controlling defect information from the image processing device 19. By
The quality of the test lens L is also determined.

The laser light source 1 and the shutter 2 can be replaced with a laser light source capable of controlling modulation or oscillation from the outside. The movable deflecting mirror 8 and the rotating mirror 10 are interchanged with each other on the optical path. Is also good.

[0035]

As described above, the lens inspection apparatus according to the first aspect can perform inspection by uniform illumination without moving or rotating the object to be inspected.

According to the lens inspection apparatus of the second aspect, it is possible to realize optimal illumination for the test object having a circular opening.

In the lens inspection apparatus according to the third aspect, in the illumination system, the object to be inspected is two-dimensionally scanned, and at the same time, the condensing point is arranged so as to be substantially regarded as a point light source. Can be improved.

The lens inspection apparatus according to the fourth aspect can scan the incident light beam in the circumferential direction.

The lens inspection apparatus according to the fifth aspect can inspect an object having a circular opening without moving.

In the lens inspection apparatus according to the sixth aspect, the image can be rotated by the detection optical system.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laser light source 2 shutter 3 ND filter 4 polarizing filter 5 beam expander 8 movable deflection mirror 10 rotating reflection mirror 11, 12 aperture mask 12 rotating diffusion plate 13, 15 imaging lens 14 image rotating element 16 one-dimensional CCD sensor 17, 18 Rotation sensor 19 Image processing device 20 Computer L Object to be inspected

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F065 AA49 AA60 AA65 BB05 BB22 CC22 FF42 GG04 JJ03 JJ26 LL09 LL13 LL24 LL30 LL32 LL49 LL62 MM16 QQ17 2G051 AA90 AB06 BA10 BC06 BC07 CA04 CB02 A062

Claims (6)

[Claims] An illumination optical system for illuminating an object to be inspected is provided with two deflectors, and an image is formed in an imaging optical system for imaging transmitted light from the object to be imaged on an image sensor. A lens inspection device comprising a rotating image rotating element. 2. The deflector according to claim 1, wherein the two deflectors comprise a one-dimensional deflector for scanning an incident light beam in a one-dimensional direction and a circumferential deflector for scanning in a circumferential direction around an optical axis. Lens inspection device. 3. The two deflectors include a first deflector and a second deflector, and a focusing point is formed near a reflection surface of the first deflector by an incident optical system of the first deflector. The first
A focusing system near the reflecting surface of the first deflector is re-imaged near the reflecting surface of the second deflector by a lens system having a positive power provided between the deflector and the second deflector. The lens inspection device according to claim 1, wherein 4. The lens inspection apparatus according to claim 2, wherein a reflection surface of the circumferential deflector is not orthogonal to a rotation axis of the circumferential deflector. 5. An optical system for picking up an image of a screen that reflects transmitted light transmitted from the object to be inspected is constituted by an infinity optical system including two lens groups, and is provided between the two lens groups. The lens inspection device according to claim 1, further comprising the image rotation element that rotates an image around an optical axis. 6. The lens inspection apparatus according to claim 5, wherein a diaphragm of a lens system constituted by said two lens groups is provided inside said image rotation element.