JP3231592B2 - Optical member inspection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical member inspection apparatus for detecting an optical defect such as a refractive index abnormality of an optical member such as a lens, and more particularly, to a centering of an optical member set as an inspection object. The present invention relates to an optical member inspection device that can be automatically performed.

[0002]

2. Description of the Related Art Optical members such as lenses and prisms are designed such that an incident light beam is regularly refracted and travels in parallel, or converges or diverges at one point or linearly. However, if the refractive power is irregularly changed due to abnormal molding of the optical member, or if dust or scratches are generated on the surface of the optical member due to human handling after the formation, the incident light beam is disturbed. Desired performance cannot be obtained. In particular, in an optical member such as a lens or a prism formed by injecting a resin into a mold and performing injection molding, sinking (a depression generated when the resin is separated from the surface of the mold) and jetting (optical member) due to molding abnormality. In this case, it is easy to generate a flow mark (a portion where the resin density is partially changed) and a flow mark (a W-shaped wrinkle generated on the surface of the optical member due to the shrinkage of the resin). Is needed.

For this reason, the present inventor has filed an application for an optical member inspection apparatus capable of automatically detecting an optical defect of an optical member set as Japanese Patent Application No. 7-229242. The optical member inspection apparatus captures light transmitted through the optical member, a knife edge rotatably disposed at a focal position of the optical member, a diffuser disposed behind the knife edge to emit illuminating light. And an imaging device for performing the operation. According to the optical member inspection apparatus having such a configuration, a portion having an abnormal refractive power (refractive power) on the surface or inside of the optical member is observed as a portion where the light and dark density changes rapidly.

[0004] In order to sufficiently obtain the above-described effect that the above-described optical member inspecting apparatus is capable of observing an abnormal refractive power (refractive power) portion as a portion where the light and dark density changes rapidly, it is necessary to rotate the edge of the knife edge. The center must coincide with the optical axis of the optical member to be inspected.

[0005]

However, it takes a long time for an operator to manually adjust the optical axis of the optical member to the center of rotation of the edge of the knife edge (hereinafter referred to as "centering of the optical member"). And the centering accuracy varies depending on the skill of the operator. If the alignment accuracy varies as described above, the degree of light and shade in the measurement image obtained as a measurement result also varies, so that it becomes impossible to detect the degree of defect based on the measurement image.

[0006] The present invention has been made based on the above awareness of problems, and it is an object of the present invention to provide an optical member inspection apparatus capable of automatically centering an optical member to be inspected.

[0007]

The invention described in each claim is
It has been made to solve the above problems. The invention according to claim 1 is an optical member inspection apparatus that detects an optical defect of an optical member, wherein the diffuser plate is illuminated by illumination light, and the optical member inspection device is disposed at a focal position of an optical system including the optical member, A light-shielding unit that is in contact with the diffusion plate so as to partially transmit and partially shield light diffused by the diffusion plate, and partially shields a part of the light-shielding unit that partially transmits the light. Rotating means for rotating the light shielding means about a rotation axis which is in contact with a boundary line with a part to be imaged, image capturing means for capturing light transmitted through the optical system, and the optical member in an image captured by the image capturing means Image center specifying means for specifying the center of the image, rotation axis position specifying means for specifying the position of the rotation axis in an image captured by the imaging means, and the optical member in the image As the position of the center and the rotational axis of the image coincides, characterized in that a moving means for moving the optical axis of the optical system.

The optical member includes a convex lens and a concave lens, a prism, a concave mirror and a convex mirror, and a plane-parallel plate. Further, it includes an optical member made of glass and an optical member formed by resin molding. The optical defect of the optical member refers to a partial abnormality of the refractive index or the refractive power, a defect on the surface of the optical member, or the like.
Examples of abnormalities in the refractive index and the refractive power include sink marks, jetting, and flow marks in resin-molded optical members, and poor surface processing in optical members made of glass. The surface defects of the optical member include surface scratches, dirt, dust, and the like.

The diffusion plate may be a translucent member illuminated from behind or a reflective member illuminated from the front side. The light-shielding means may be a light-shielding pattern directly printed on the surface of the diffusion plate, a plate-shaped opaque member may be appropriately cut out and attached to the diffusion plate, or may be separate from the diffusion plate. The light shielding pattern may be printed on the surface of the transparent member. It is desirable that a boundary line between a portion that partially transmits light and a portion that blocks light in the light shielding unit is linear. In addition, as long as the boundary line is in contact with the rotation axis of the light shielding means, only one boundary line or a plurality of stripe lines may be provided.

The "optical system including an optical member" is an optical member itself which is a convex lens or a positive lens group including an optical member which is a concave lens. Each member is adjusted such that the focal position of the entire optical system coincides with the position of the light shielding means.

The rotating means may rotate the light shielding means integrally with the diffusion plate, or may rotate only the light shielding means with the diffusion plate fixed. The imaging means may be one that captures an image using a solid-state imaging device or one that captures an image using an imaging tube.

When the front shape of the optical member is rotationally symmetric, the image center specifying means may specify the center of gravity of a figure having the same shape as the image of the optical member as the center of the image. If the front shape of the member is not rotationally symmetric, the center of the fillet diameter of the image of the optical member may be specified as the center of the image.

[0013] The rotation axis position specifying means, while rotating the boundary line of the light shielding means by the rotation means, captures an image of the boundary line by the imaging means and specifies the center of rotation. In this case, an image of the boundary line may be captured at at least two rotation positions, and the intersection may be specified as the position of the rotation axis.

The moving means may determine the distance between the center of the image of the optical member and the position of the rotation axis, and move the optical member based on this distance. In this case, the movement amount is calculated by multiplying the obtained distance by a constant. In addition,
In a situation where a shift between the center of the image of the optical member and the position of the rotation axis can occur in any direction, it is necessary to consider the direction of the shift. Therefore, the components of the movement amounts in the two orthogonal directions in the plane in which the optical member moves may be calculated respectively, and the optical member may be moved based on the calculated components of the movement amounts in each direction.

An optical member inspection apparatus according to a second aspect is characterized in that the optical system according to the first aspect is a convex lens. According to a third aspect of the present invention, there is provided an optical member inspection apparatus, wherein the optical system according to the first aspect includes the optical member that is a concave lens and the correction lens that is a convex lens.

According to a fourth aspect of the present invention, the image center identifying means extracts the outer edge of the optical member in the image and determines the position of the center of gravity of the figure having the outer edge in the image of the optical member. Is specified by specifying it as the center of the

According to a fifth aspect of the present invention, there is provided an optical member inspection apparatus, wherein the image center specifying means extracts the outer shape of the optical member in the image and sets the center of the fillet diameter of the figure having the outer edge to the optical member. Is specified by specifying it as the center of the image.

In the optical member inspection apparatus according to the sixth aspect, the rotation axis position specifying means of the first aspect specifies the intersection of the image of the boundary line at a plurality of rotation positions as the position of the rotation axis. Things.

According to a seventh aspect of the present invention, the moving means of the first aspect calculates a shift amount between the center of the image of the optical member in the image and the position of the rotation axis, and corresponds to the shift amount. The movement amount of the optical member to be calculated is calculated, and the optical member is moved according to the movement amount, thereby specifying the optical member.

According to an eighth aspect of the present invention, the optical member inspection apparatus is characterized in that the moving means of the seventh aspect calculates the moving amount by dividing the moving amount into two orthogonal components in a plane orthogonal to the rotation axis. It is.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

[0022]

First Embodiment <Overall Configuration of Optical Member Inspection Apparatus> FIGS. 1 and 2 are optical configuration diagrams showing a first embodiment of an optical member inspection apparatus according to the present invention. As shown in FIGS. 1 and 2, the illumination unit 4 and the imaging device 7 that constitute the optical member inspection device are
They are arranged facing each other on the same optical axis (hereinafter referred to as “device optical axis”) l.

An image pickup device 7 as an image pickup means includes an image pickup lens 8 which is a positive lens system as a whole, and an image pickup device 9 comprising a CCD area sensor for picking up an image formed by light converged by the image pickup lens 8. It is configured. The image data captured by the image sensor 9 is
It is input to the display device 10 and the image processing unit 14.

The display device 10 is an image monitor device used at the time of initial adjustment of the optical member inspection device (ie, at the time of adjusting the position of the illumination unit 4 described later). Image processing unit 1
Reference numeral 4 denotes a processor that performs a process of determining whether the inspection target optical member is a good product or a defective product, performs predetermined image processing on image data input from the imaging element 9, and performs processing of the inspection target optical member. Quantify the degree of optical defects and compare this number to a certain criterion value (tolerance)
It is determined whether this numerical value falls within or exceeds the determination reference value. In order to perform this determination process, the image processing unit 14 has a first memory 14a and a second memory 14b. In addition, the image processing unit 14 instructs the knife edge rotation control unit 15 to rotate the motor 13 along with performing this determination process.

The image processing apparatus 14 further includes an XY
By controlling the moving stage control unit 17, the optical members A and B to be inspected are centered. Also when performing the centering, the image processing device 14 instructs the knife edge rotation control unit 15 to rotate the motor 13 and performs predetermined rotation on the image data captured by the imaging device 9 of the imaging device 7. Perform image processing. Then, the image processing device 14 detects the optical axis position of the inspection target optical members A and B as an image center specifying unit, a rotation axis position specifying unit, and a moving unit, and stores the data in the data storage unit 1.
With reference to 6, a movement amount for adjusting the optical axis position to the apparatus optical axis l is calculated. Then, an operation instruction is issued to the XY moving stage control unit 17.

The XY moving stage control section 17 moves the optical members A and B to be inspected in a plane perpendicular to the optical axis l of the apparatus to perform centering. And outputs a driving pulse to.

The XY moving stage 18 is a Y stage 18a that slides in a Y direction (a direction perpendicular to the optical axis 1 in the plane of FIG. 1 and FIG. 2) with respect to a fixed portion in the apparatus, and An X stage 18b is slid with respect to the Y stage 18a in the X direction (a direction perpendicular to the plane of FIG. 1 and FIG. 2). The Y stage 18a is provided with a Y direction pulse motor 20 for receiving a driving pulse from the XY moving stage control unit 17 and slidingly driving the Y stage 18a in the Y direction. Similarly, the X stage 18b receives a drive pulse from the XY moving stage control unit 17 and
An X-direction pulse motor 21 for slidingly driving the stage 18b in the X-direction is attached. further,
A runner 19 extending integrally from the optical members A and B to be inspected is provided on the upper surface (upper surface in the drawing) of the X stage 18b.
Is provided with a holding portion 22 for holding the front end of the head.
With the above configuration, the XY moving stage 18 is
Since the optical members A and B to be inspected are moved in a plane orthogonal to the optical axis l of the device in response to the drive pulse from the moving stage control unit 17, the optical axes can be matched with the optical axis l of the device. is there. That is, the image processing unit 14, the XY moving stage control unit 17, the XY moving stage 18, and the holding unit 22 constitute a moving unit.

A knife edge rotation control unit 15 connected to the image processing unit 14 rotates the light shielding member 6 by 22.5 degrees at the time of inspection and 90 degrees at the time of centering according to a rotation instruction from the image processing unit 14. Motor 1 so that it rotates
Rotate 3

On the other hand, the illumination unit 4 can move forward and backward on the apparatus optical axis 1 toward the image pickup apparatus 7 as a whole. Inside the illumination unit 4, a disk-shaped diffuser plate 5 whose center is coaxial with the device optical axis 1 is held rotatably about the device optical axis 1 in a plane orthogonal to the device optical axis l. ing. On the surface of the diffusion plate 5 on the imaging device 7 side,
A light shielding plate 6 as light shielding means is integrally attached. As shown in FIG. 3, which is a top view,
It is a semicircular plate made of an opaque member. A radial straight line passing through the center of the diffusion plate 5 and in contact with the apparatus optical axis l is defined as a chord (knife edge) 6a, and has an arc having the same radius as the diffusion plate 5. are doing. As a result of having such a configuration, the light diffused by the diffusion plate 5 is partially shielded by the light shielding plate 6 and partially transmitted by a portion not covered by the light shielding plate 6. That is, the knife edge 6a
Corresponds to a boundary line between a part that partially transmits light and a part that partially blocks light in the light shielding unit.

An annular gear 11 coaxial with the diffusion plate 5 is fixed to the periphery of the diffusion plate 5. This annular gear 11
Are engaged with a pinion gear 12, and the pinion gear 12 is connected to the motor 1 fixed in the lighting unit 4.
3 is attached to the rotating shaft. Therefore, the motor 13
When is rotated by the knife edge rotation control unit 15, the light shielding plate 6 and the diffusion plate 5 are rotationally driven via both gears 12 and 11, and are orthogonal to the apparatus optical axis l as shown in FIG. It is rotationally driven in the plane. Note that the rotation direction in this case is clockwise as viewed from the imaging device 7, as shown in FIG. As a result of this rotation, the knife edge (chord) 6a of the light shielding plate 6 also rotates about the device optical axis l. That is, the image processing unit 14, the knife edge rotation control unit 15, the motor 13, and the gears 11 and 12
A rotating means is configured.

On the back surface side of the diffusion plate 5, the front end 3a of the optical fiber bundle 3 is fixed to the illumination unit 4. A light source device including a white lamp 1 and a condenser lens 2 is arranged at a base end 3 b of the optical fiber bundle 3. Then, the white light emitted from the white lamp 1 is condensed by the condensing lens 2 and enters the optical fiber bundle 3 from the base end 3b. This white light is transmitted through the optical fiber bundle 3, and the diffuser 5
Irradiated toward That is, the knife edge 6 of the light shielding plate 6
a is illuminated from behind. Note that the length of the optical fiber bundle 3 is set sufficiently longer than the movable distance of the illumination unit 4. Therefore, even if the illumination unit 4 moves, the optical fiber bundle 3 follows and can always illuminate the knife edge 6a of the light shielding plate 6.

The optical members A and B to be inspected are disposed between the imaging device 7 and the illumination unit 4 with the tip of the runner 19 extending integrally from the peripheral surface thereof being held by the holding portion 22. More specifically, when the optical member to be inspected is a convex lens A as shown in FIG. 1, the convex lens A is arranged at a position where the focal position of the convex lens A coincides with the surface of the diffusion plate 5. When the optical member to be inspected is a concave lens B as shown in FIG. 2, a power (absolute value) larger than the power (absolute value) of the concave lens B is applied between the concave lens B and the illumination unit 4. A correction lens C, which is a convex lens, is disposed. The concave lens B and the correction lens C
Is a positive lens group as a whole, and these concave lens B and correction lens C are arranged so that the combined focal position of the lens group coincides with the surface of the diffusion plate 5. That is,
The focal position of the optical system including the optical member to be inspected is matched with the position of the light shielding means. <Principle of Optical Defect Display> When the inspected optical members A and B (and the correction lens C) are arranged as described above, light emitted from the inspected optical member A
As long as B is a good product, it becomes a parallel light. Therefore, when viewed from the imaging device 7 side, this is equivalent to the knife edge 6a of the light shielding plate 6 being located at infinity.

Incidentally, if the focal position of the optical member A to be inspected (combined focal position of the optical system including the optical member B to be inspected and the correction lens C) is shifted toward the imaging device 7 from the position of the knife edge 6a. An inverted image (real image) of the knife edge 6a is formed in a space between the inspection target optical member A (the inspection target optical member B) and the imaging lens 8 of the imaging device 7. The inverted image (real image) of the knife edge 6a is relayed by the imaging lens 8, and an upright image (real image) of the knife edge 6a is formed in a space on the imaging element 9 side of the imaging lens 8. Conversely, when the focal position of the optical member A to be inspected (the combined focal position of the lens group including the optical member B to be inspected and the correction lens C) is shifted toward the optical fiber bundle 3 from the position of the knife edge 6a, the light shielding plate 6 An erect image (virtual image) of the knife edge 6a is formed in the space on the optical fiber bundle 8 side. The upright image (virtual image) of the knife edge 6a is relayed by the imaging lens 8, and an inverted image (real image) of the knife edge 6a is formed in a space on the imaging element 9 side of the imaging lens 8. That is, the focal position of the inspection target optical member A (the composite focal position of the optical system including the inspection target optical member B and the correction lens C) is the object (knife edge 6) existing at this position.
The image a) is a boundary point where the image is formed as an erect image or an inverted image in the space on the imaging element 9 side of the imaging lens 8, and at a position where it is in an optically unstable state. is there.

The distance between the optical member to be inspected and the imaging lens 8 is such that the focal position of the optical member A to be inspected (the combined focal position of the optical system including the optical member B to be inspected and the correction lens C) is the knife edge 6a. Even if it is slightly shifted to the image pickup device 7 side from the position, the inverted image (real image) of the knife edge 6a is formed between them (more precisely, between the two focal positions). , As long as possible.
Further, the image pickup element 9 and the image formation position (average position) of the upright image and the upright image are formed so that these images can be captured to some extent clearly even if an upright image is formed or an inverted image is formed by the imaging lens 8. It is arranged at an intermediate point with the formation position (average position). This position is a position optically equivalent to the surface of the inspection target optical members A and B with respect to the imaging lens 8.

Therefore, a real image (inverted image) α of the outer edge of the optical member to be inspected is always formed on the image pickup device 9 and an inspection image is formed around the real image α of the outer edge of the optical member to be inspected. The real image (inverted image) of the knife edge 6a directly seen without passing through the target optical member is slightly blurred (FIG. 5).
(See (a) to (e)).

The focal position of the optical member A to be inspected (the combined focal position of the optical system composed of the optical member B to be inspected and the correction lens C) is located inside the real image α of the outer edges of the optical members A and B to be inspected. ) Is shifted toward the imaging device 7 from the position of the knife edge 6a, the real image (erect image) of the knife edge 6a is formed with a slight blur (FIG. 5D,
FIG. 5E). The actual image (erect image) of the knife edge 6a becomes larger as the shift amount of the focal position decreases (see FIG. 5D), and becomes clearer as the shift amount increases. (See FIG. 5 (e)).

On the contrary, the focal position of the optical member A to be inspected (the combined focal position of the optical system including the optical member B to be inspected and the correction lens C) is closer to the optical fiber bundle 3 than the position of the knife edge 6a. In the case of deviation, the real image (inverted image) of the knife edge 6a is slightly blurred inside the real image α of the outer edge of the inspection target optical member (FIG. 5).
(B) and FIG. 5 (a)). The real image (inverted image) of the knife edge 6a becomes larger as the shift amount of the focal position decreases (see FIG. 5B), and becomes clearer as the shift amount increases, as the blur amount decreases. FIG. 5 (a)).

When the focal position of the optical member A to be inspected (combined focal position of the optical system including the optical member B to be inspected and the correction lens C) coincides with the position of the knife edge 6a,
The amount of blur inside the real image α of the outer edge of the optical member to be inspected is maximized, and light rays are emitted with uniform brightness throughout (see FIG. 5C).

In the image data input to the display device 10 and the image processing unit 14, the outer edge α of the optical member to be inspected is
When the focal position of the optical member A to be inspected (combined focal position of the lens group including the optical member B to be inspected and the correction lens C) coincides with the position on the surface of the diffusion plate 5,
Unless the optical members A and B to be inspected have optical defects, the black portion of the knife edge 6a (the portion where white light is blocked)
And a white portion (a portion through which white light is transmitted) are completely mixed and displayed as a gray plane having a uniform density (in the case of a spherical lens). When an aspherical lens is inspected as the optical members A and B to be inspected, since the focal position changes not only at one point but slowly, an image having a very gentle luminance change is obtained.

On the other hand, if there is a portion in the optical members A and B to be inspected having an abnormal refractive index or a portion having an abnormal refractive power due to a shape defect on its surface, only the abnormal portion is detected. , Has a focal length different from that of the normal part. Therefore, as shown in FIG. 6, an image γ of the knife edge appears only in the abnormal portion. The degree of the refractive index (refractive power) abnormality (focal length shift amount) of the abnormal portion is reflected in the appearance of the knife edge image γ. That is, the more clearly the shading of the image of the knife edge appears, the greater the degree of the refractive index (refractive power) abnormality (deviation of the focal length) becomes.

When dust or dirt is attached to the surface of the optical member A to be inspected or is scratched, the dust or dirt is attached to the inner portion of the outer edge α of the optical member to be inspected in the image data. Or the image of the flaw is taken by the imaging lens 8
Formed by That is, when light is blocked by dust or dirt, a shadow darker than the surroundings is formed, and when light diverges due to scratches, a bright spot is formed. <Principle of Automatic Centering> Next, the principle of automatic centering will be described.

In the present embodiment, the lens as the optical member to be inspected has its front surface (incident side or exit side).
It is assumed that the peripheral surface is processed so that the optical axis is located at the center position as viewed from the side. here,
The “center position” means the center position of the fillet diameter in the front shape of the inspection target optical member. That is, when the front shape of the optical member to be inspected is arranged on the XY coordinate, the position where the center of the maximum width in the X direction and the center of the maximum width in the Y direction intersect is referred to as the “center position”. It is.

Therefore, when the front shapes of the optical members A and B to be inspected are rotationally symmetrical with respect to the optical axis position, the center of gravity in the front shape of the optical member to be inspected is the center position. Therefore, if the XY moving table 18 is driven and moved so that the position of the center of gravity is overlapped with the center of rotation of the knife edge 6a, the optical axes of the optical members A and B to be inspected become the center of rotation of the knife edge 6a ( It coincides with the device optical axis l).

For example, even if the front shape is a rectangular lens as shown in FIG. 6, for example, a part of the lens may be partially cut off for the sake of assembling the optical device. In such a case, the position of the center of gravity in the front shape of the lens will be shifted from the center position that matches the optical axis position. Therefore, in that case,
The captured image of the optical member to be inspected is mapped on coordinates to determine the center position of the fillet diameter. Then, by driving the XY moving table 18 to move the center position of the fillet diameter so as to overlap the rotation center of the knife edge 6a, the optical axes of the optical members A and B to be inspected are moved to the knife edge 6a.
(The optical axis l of the device). <Preparation Processing> Next, basic data necessary for performing automatic centering (a coordinate center position indicating the rotation center of the knife edge 6a in the image data, and an object corresponding to one dot of a pixel constituting the image data) The preparation processing (corresponding to the rotation axis position specifying means) executed by the image processing unit 14 to obtain the length on the side is shown in the flowchart of FIG.
Note that it is assumed that the inspection target optical members A and B and the holder 22 have been removed from the optical axis l of the apparatus as a prerequisite for performing this preparation processing.

The flow chart of FIG.
The process is started when a preparation start button (not shown) connected to No. 4 is pressed, and an origin return command is issued to the knife edge rotation control unit 15 in the first step S001. Upon receiving the origin return command, the knife edge rotation control unit 15 drives the motor 13 to return the rotational position of the knife edge 6a to the origin. This origin is defined as 0 shown in FIG.
1 and 2, as shown in FIGS. 1 and 2, the light shielding plate 6 itself is located on the left side of the drawing with its knife edge 6a oriented in a direction (X direction) perpendicular to the paper surface. is there.

In the next step S002, the luminance of each pixel constituting the image data input from the image pickup device 9 is converted into numerical information of 256 gradations, and each of them is converted into the first memory 14a.
Write to.

In the next step S003, the numerical information written in the memory 14a is sequentially scanned to perform a differentiation process.
That is, the numerical value of each pixel is checked in order from the upper left pixel to the lower right pixel in the image. Then, the numerical value of the check target pixel is compared with the numerical value of the pixel on the left side thereof and the numerical value of the pixel adjacent on the upper side, and the absolute value of the difference between these numerical values is calculated as the differential value [0 to 255] of the check target pixel. And In the image data converted into the differential value obtained in this way, only the edge of the knife edge 6a is an image that appears as a line with high density.

In the next S004, an image synthesizing process is executed. That is, each differential value obtained in S003 is written in the second memory 14b. At this time, S in the previous loop processing
As a result of 004, the differential value of the previous image is stored in the second memory 1
4b, the respective differential values already written in the second memory 14b are taken out, and after adding the respective differential values obtained in S003 in the current loop processing, the respective differential values are stored in the second memory 14b. Overwrite.

In the next step S005, it is checked whether or not the knife edge 6a has made one rotation after starting the processing. If it has not yet been rotated once, in S006, a command is issued to the knife edge rotation control unit 15 to rotate the knife edge 6a by 90 degrees. Upon receiving this instruction, the knife edge rotation control unit 15 rotates the knife edge 6a 90 degrees clockwise. If the rotated image data is input from the image sensor 9, the process returns to S002, and the process for the new image data is executed.

When the knife edge makes one rotation as a result of repeating the loop processing as described above (that is, the knife edge 6a
Is repeated four times), the process exits this loop process from S006, and the process proceeds to S007. FIG. 8 shows the image data written in the second memory 14b at this time. In FIG. 8, the line indicated by the reference sign “x” corresponds to the knife edge 6 a at the rotation position rotated by 180 degrees from the origin, and the line indicated by the reference sign “y” is 90 degrees from the origin. And 27
This corresponds to the knife edge 6a rotated by 0 degrees.

In S007, the center coordinates of the image data written in the second memory 14b are obtained. That is, since the intersection “0” between the line “x” and the line “y” in the image data shown in FIG. 8 is the center of rotation of the knife edge 6a, the position in the image data corresponding to this intersection “0” ( Pixel) is defined as “center coordinates”. Further, the line “x” is defined as an x coordinate, and the line “y” is defined as a y coordinate.

In the next S008, the XY moving stage 1
A reference object (a non-defective lens having a known diameter) is set at 8 and placed in the optical axis l of the apparatus.

In the next S009, the XY moving stage 1
Based on the diameter (known value) of the reference object set to 8 and the number of pixels corresponding to the diameter of this reference object in the image data, the length per pixel (optical members A and B)
Is calculated at a position where is disposed in a plane perpendicular to the optical axis l).

In the next S010, information indicating the coordinate center position in the image data obtained in S007, and
Information indicating the length per dot obtained in 009 is
The data is stored in the data storage unit 16. Thus, the preparation processing ends. <Inspection Processing> Next, the contents of the control processing executed in the image processing section 14 for automatic centering and optical member inspection will be described with reference to the flowcharts of FIGS. It is assumed that the optical members A and B to be inspected are set on the XY moving stage 18 as a premise for executing this processing.

The main routine of the control process shown in FIG.
The operation is started by turning on the power to the optical member inspection apparatus. Then, in the first step S101 after the start, it is determined whether or not to execute the automatic centering processing. This determination is made based on whether or not an automatic centering start button (not shown) connected to the image processing unit 14 has been pressed. Then, when an automatic centering start button (not shown) is pressed, an automatic centering process is executed in S102.

FIG. 10 is a flowchart showing an automatic centering processing subroutine executed in S102. S201 to S executed first after entering this subroutine
In the loop processing of 205, S002 to S in FIG.
The same processing as the loop processing of 006 is executed. In this case, in S202, the image α of the outer edge of the optical members A and B set on the XY moving stage 18 and the image of the portion having the optical defect are extracted.

When the knife edge 6a makes one rotation, S
In S206, which is executed after exiting the loop process from 204, a binarization process is performed. This binarization process means that if the numerical information corresponding to each pixel of the image data in the second memory exceeds a predetermined threshold, the numerical information is replaced with 255 (white), and if not, 0 (black) ). This threshold value is set to a value such that the outer edge α of the inspection target optical member can be left as a white (255) closed curve without interruption. FIG. 12A shows image data obtained as a result of this binarization processing. In FIG. 12A, δ is an image of a gate for resin injection formed at the boundary between the runner 19 and the optical member, ε is an image of a pattern on the gate, and η is a refractive index such as jetting. Abnormal part,
σ is an image of dust adhering to the optical member surface. In FIG. 12, for convenience of drawing, white / black are reversed.

In the next step S207, a closed area extraction process is executed. This closed region extraction process is a process of extracting only a region surrounded by a closed white line. Specifically, among the black pixels [0] constituting the image data binarized in S301, those surrounded by white pixels [255] are regarded as pixels in the closed region. Then, the numerical values of all the pixels considered to be within this closed area are 2
55, and the numerical values of all other pixels are set to 0. The image data obtained as a result of the closed region extraction processing is shown in FIG.
Shown in As shown in FIG. 12B, as a result of the closed region extraction processing, the line δ having an open end is deleted, but only the white / black inversion occurs within the outer edge α of the optical member which is a closed curve. Therefore, the internal closed curve η and the point σ remain.

In the next step S208, a filling process is executed. This filling process is a process for erasing black pixels [0] left in white pixels [255]. Specifically, among the black pixels [0] constituting the image data obtained in S207, the numerical value of a pixel surrounded by white pixels [255] is set to 255. FIG. 12C shows image data obtained as a result of the filling processing. As shown in FIG. 12C, as a result of the filling process, the closed curve η and the point σ within the outer edge α of the optical member are deleted,
Only large and small areas α and ε remain.

In the next S209, an area selection process is executed. The region selection process is a process for validating only a region originally required and deleting other closed regions extracted based on a part of a gate or the like. Specifically, of the closed regions included in the image data obtained in S208, the closed region located at the center of the screen is left as it is, and the numerical values of all the pixels forming the other completely closed regions are set to 0. FIG. 12D shows image data obtained as a result of this area selection processing. As shown in FIG. 12D, the area of the white pixel [255] in this image corresponds to the area of the front image of the inspection target optical member.
This image is hereinafter referred to as a “mask image”.

In the next step S210, the position of the center of gravity of the region selected in step S209 (the center position of the fillet diameter when the shape of the region is not a point symmetric shape) is obtained (corresponding to the image center specifying means).

In the next step S211, information indicating the coordinate center position stored in the data storage unit 16 is read. Then, the deviation amount between the coordinate center position on the image data and the center of gravity position (the center position of the fillet diameter) obtained in S210 is calculated as
It is determined separately for the number of dots in the x direction and the number of dots in the y direction.

In the next S212, information indicating the length per dot stored in the data storage section 16 is read. Then, the number of dots in the x direction and the number of dots in the y direction obtained in S211 are multiplied by the read length to convert them into a movement amount in the x direction (ΔX) and a movement amount in the y direction (ΔY).

In the next step S213, the XY movement stage controller 17 is instructed to move the optical members A and B to be inspected by ΔX in the X direction and by ΔY in the Y direction (moving means). Corresponding to). When the XY moving stage 18 is driven according to this command, the optical members A and B set on the XY moving stage 18 are centered. When this step is completed, this subroutine ends and the process returns to the main routine of FIG. At the end of this subroutine,
The data stored in the first memory 14a and the second memory 14b is cleared.

In the main routine of FIG. 9, once the automatic centering process of S102 is completed, the process is returned to S101 once. On the other hand, if it is determined in S101 that the automatic centering start button (not shown) has not been pressed, the process proceeds to S10
In 3, it is checked whether or not the inspection of the optical member is to be executed. This check is performed based on whether or not a not-shown inspection start button connected to the image processing unit 14 has been pressed. Then, when the inspection start button (not shown) is pressed, the loop processing of S104 to S107 and S111 is executed.

S104 to S1 in this loop processing
The process of 07 is exactly the same as the processes of S002 to S005 in FIG. However, in S111, the knife edge 6a is
Command to rotate 2.5 degrees. In this case, in S105, an image α of the outer edge of the optical members A and B set on the holder 22 and an image of a portion having an optical defect are extracted. As described above, the knife edge 6a is rotated by a small amount (S111), and the obtained image data is accumulated (S10).
6) The reason is as follows. That is, when the linear knife edge 6a is inserted into the optical path, the knife edge 6a
The abnormal component in the direction parallel to the direction a can be detected best, but the abnormal component in the direction orthogonal to the direction of the knife edge 6a is not so well detected. for that reason,
The knife edge 6a itself is rotated in a plane orthogonal to the optical axis l of the apparatus, and all abnormal components in all directions are detected and synthesized on the same image. As a result, the following effects can be obtained. That is, in the image in the case where the knife edge 6a is stopped, as shown in FIG. 6, in addition to the edge of the optically defective portion (the arc portion in the center of FIG. 6), the edge of the knife edge 6a (the left and right in the center of FIG. 6). Extending black and white border)
Is also projected as a place where the shading changes rapidly. Since the edge of the knife edge 6a is not the edge of the optically defective portion originally required to be detected, it is desirable that the edge is not detected. Thus, when the knife edge 6a is rotated, the edge of the knife edge 6a rotates while the position of the edge of the optically defective portion does not move. Therefore, the edge of the optically defective portion is increasingly emphasized in the image synthesizing process, whereas the edge of the knife edge 6a is planar in the closed region (the portion surrounded by the edge) of the optically defective portion. Are not recognized as a boundary line.

As a result of repeating the loop processing as described above, the knife edge makes one rotation (ie, knife edge 6a).
(When the rotation of 22.5 degrees is repeated 16 times), S10
Then, the process exits from the loop process from S7 and proceeds to S108.

FIG. 11 is a flowchart showing the contents of the inspection target area extraction processing subroutine executed in S108. The first S after entering this subroutine
The processing from 301 to S304 is performed in S2 in FIG.
The processing is exactly the same as the processing from 06 to S209.

In S305, which is executed after the "mask image" is obtained by the processing from S301 to S304, the values (8-bit parallel digital values) of each pixel constituting the mask image are written to the second memory 14b. And the value of each pixel (8-bit parallel digital value)
Perform ND operation. As a result of the AND operation, only the portion of the image data written in the second memory 14b corresponding to the area of the white pixel [255] of the mask image is left as it is, and the values of the pixels of the other portions are all 0 Becomes

As described above, image data used for determining a good or defective product is obtained. Thus, this subroutine is terminated, and the process returns to the main routine of FIG. In S109 executed after S108 in FIG. 9, S10
Numerical values (255: white or 0: black) are compared by comparing the numerical value of each pixel constituting the image data extracted as a result of step 8 with a threshold value set to a level at which the eye noise is not extracted. That is, if the numerical value of each pixel forming the image data is larger than the threshold value (if it is bright), the numerical value is replaced with 255, and if the numerical value of each pixel making up the image data is smaller than the threshold value (if it is dark), the numerical value is changed. Replace with 0. Then, the graphic features of the binarized image (the area of the white part,
Calculate the maximum width, center of gravity, fillet diameter, etc.). For example, the number of white [255] pixels is counted and defined as the area amount.

In the next step S110, a pass / fail judgment process is executed. That is, each graphic feature amount calculated in S109 is compared with each preset pass / fail judgment reference value.
If there is at least one graphical feature that exceeds the corresponding pass / fail determination reference value, it is determined to be rejected (defective), but all of the graphical features are within the corresponding pass / fail determination reference value. If it is within the range, it is judged as a pass (good product). In addition,
Which of the graphic feature amounts used for the determination is used for the pass / fail determination depends on the type of the optical member to be inspected.
Upon completion of the pass / fail determination processing, the image processing ends. <Inspection Procedure by Optical Member Inspection Apparatus> When inspecting the optical members A and B by the optical member inspection apparatus according to the present embodiment, the optical members A and B are previously moved to the XY moving stage 18.
Remove from The inspection target optical member is a concave lens B.
, The inspection target optical member B and the illumination unit 4
And the correction lens C is inserted. As described above, in the present embodiment, by mounting the correction lens C composed of a convex lens, it is possible to inspect the optical member to be inspected even with the concave lens B.

Then, the examiner presses a preparation start button (not shown). Then, the preparation processing shown in FIG. 7 is executed, and information indicating the coordinate center position in the image data and information indicating the length per dot are stored in the data storage unit 16. Note that the coordinate center position in the image data is obtained based only on the rotation center of the knife edge 6a, regardless of the imaging optical axis position of the imaging device 7. Therefore, even if the imaging optical axis of the provisional imaging device 7 is deviated from the rotation center of the knife edge 6a, the coordinate center position can be accurately obtained.

Next, the inspector sets the non-defective optical members A and B prepared in advance on the XY moving stage 18 and arranges them in the optical axis l of the apparatus. The inspector then proceeds to the white lamp 1
Is turned on to illuminate the knife edge 6a of the light shielding plate 6. Then, an image captured by the image sensor 9 is displayed on the display device 10. Then, the inspector manually centers the optical members A and B set as described above.

The examiner moves the lighting unit 4 while watching the image displayed on the display device 10. And
As shown in FIG. 5A or 5B, when the knife edge γ is seen inside the outer edge α of the inspection target optical member in the same direction as the knife edge β seen outside the outer edge α of the inspection target optical member, the illumination is performed. Since the unit 4 is too close to the optical member to be inspected, the illumination unit 4 is moved away from the optical member to be inspected. Conversely, as shown in FIG. 5D or 5E, inside the outer edge α of the inspection target optical member, the knife edge γ is formed in a direction opposite to the knife edge β visible outside the outer edge α of the inspection target optical member. When it is visible, the illumination unit 4 is too far from the optical member to be inspected, so the illumination unit 4 is brought closer to the optical member to be inspected. FIG. 5C shows the result of performing the forward / backward adjustment of the lighting unit 4.
Is the outer edge α of the optical member to be inspected.
When most of the lights disappear, it means that the lighting unit 4 is at the proper position, and the adjustment is stopped. As described above, in the present embodiment, since the illumination unit 4 is movable in the direction of the optical axis l of the device, it is possible to inspect a plurality of types of optical members having different focal lengths.

Next, the inspector removes the non-defective optical member from the holder 22 and places the optical members A and B to be inspected on the holder 22.
Set to. Then, an automatic centering start button (not shown) is pressed. Then, the automatic centering process of FIG. 10 is executed (S102). That is, the knife edge 6a is rotated once (S204, S205), and a differential composite image is created (S203). In this state, the optical members A and B are not centered, but by rotating the knife edge 6a once, the peripheral edges of the optical members A and B are extracted over the entire circumference. Therefore, a mask image indicating the front shape of the inspection target optical members A and B is extracted based on the differential composite image (S209). This mask image shows the positions of the optical members A and B in a plane orthogonal to the device optical axis l. Therefore, the center of gravity of this mask image (the center of the fillet diameter)
Is determined, the optical axis positions of the optical members A and B are determined (210). Then, based on the shift between the optical axis position and the center coordinate position in the image data, the X-direction movement amount ΔX and the Y-direction movement amount ΔY canceling out the difference amount.
Is obtained (S212). Then, these movement amounts Δ
The holder 22 is moved according to Y and ΔX (S213),
The centering of the optical members A and B is performed.

Next, the examiner presses an inspection start button (not shown) to start image processing from S104 onward in FIG. Then, the knife edge 6a is driven to rotate by 22.5 degrees at a time by the knife edge rotation control unit 15 (S111), and an image formed by light passing through the inspection target optical elements A and B at each rotation position is captured. An image is captured by the device 7 (S104). Image processing unit 1
No. 4 emphasizes the density change portion of each captured image by differential processing (S105), and adds over one rotation (S107, S111). As a result, with respect to the defect component (refractive index [refractive power] abnormality, surface defect) in any direction of the inspection target optical member, a region having the defect component is extracted and collected into one image data. That is, this image data is an image in which a portion having a defect is raised in white, regardless of the direction of the defect. The image data obtained in this manner includes data on a portion other than the portion that originally functions as an optical member, but the data on the portion is extracted by the inspection target region extraction processing in S108. Deleted. Then, the area, the maximum width, and the like of the abnormal portion are quantified and compared with a predetermined criterion value. Based on the result of the comparison, it is objectively determined whether the product is good or defective.

[0077]

According to the optical member inspection apparatus of the present invention configured as described above, the optical member to be inspected can be automatically centered.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an optical member inspection apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram when the optical member inspection device of FIG. 1 is applied to a concave lens;

FIG. 3 is a front view of a light shielding plate in FIG. 1;

FIG. 4 is a perspective view showing a rotating state of a light shielding plate.

FIG. 5 is a diagram showing an image on the display device when the movement of the lighting unit in FIG. 1 is adjusted.

FIG. 6 is a diagram showing an image on a display device when an optical member having a sink is inspected.

FIG. 7 is a flowchart showing the contents of a preparation process executed in the image processing unit of FIGS. 1 and 2;

8 is an explanatory diagram of a coordinate center position in coordinate data obtained as a result of FIG. 7;

FIG. 9 is a flowchart showing the contents of a control process executed in the image processing unit of FIGS. 1 and 2;

FIG. 10 is a flowchart showing an automatic centering processing subroutine executed in S102 of FIG. 9;

11 is a flowchart showing an inspection target area extraction processing subroutine executed in S108 of FIG. 9;

FIG. 12 is an explanatory diagram of the inspection target area extraction processing in FIG. 11;

[Explanation of symbols]

 Reference Signs List 4 illumination unit 5 diffusion plate 6 light shielding plate 7 imaging device 8 imaging lens 9 imaging device 13 motor 14 image processing unit 15 knife edge rotation control unit 16 data storage unit 17 XY moving stage control unit 18 XY moving stage A convex lens B concave lens C correction lens

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Atsushi Kida 2-36-9 Maenocho, Itabashi-ku, Tokyo Asahi Kogaku Kogyo Co., Ltd. (56) References JP-A-9-72823 (JP, A) JP-A-9-61292 (JP, A) JP-A-6-174583 (JP, A) JP-A-9-96585 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01M 11 / 00-11/08 G01N 21/84-21/958

Claims (9)

(57) [Claims] 1. An optical member inspection apparatus for detecting an optical defect of an optical member, comprising: a diffuser illuminated by illumination light; and a diffuser disposed at a focal position of an optical system including the optical member. A light-shielding unit that is in contact with the diffusion plate so as to partially transmit and partially shield the diffused light; and a part of the light-shielding unit that partially transmits the light and a part that partially shields the light. A rotation unit that rotates the light blocking unit about a rotation axis that is in contact with a boundary line of the image capturing unit; an imaging unit that captures light transmitted through the optical system; and an image of the optical member in an image captured by the imaging unit. Image center specifying means for specifying a center; rotating axis position specifying means for specifying a position of the rotary axis in an image captured by the image capturing means; and an image of the optical member in the image. An optical member inspection apparatus, comprising: moving means for moving an optical axis of the optical system so that a center and a position of the rotation axis coincide with each other. 2. The optical member inspection apparatus according to claim 1, wherein said optical system comprises only said optical member which is a convex lens. 3. The optical member inspection apparatus according to claim 1, wherein said optical system comprises said optical member which is a concave lens and a correction lens which is a convex lens, and is a positive lens system as a whole. 4. The image center specifying means extracts an outer edge of the optical member in the image, and specifies a center of gravity of a figure having the outer edge as a center of the image of the optical member. The optical member inspection device according to claim 1. 5. The image center specifying means extracts an outer shape of the optical member in the image, and specifies a center of a fillet diameter of a figure having an outer edge as a center of an image of the optical member. The optical member inspection apparatus according to claim 1, wherein 6. An optical member inspection apparatus according to claim 1, wherein said rotation axis position specifying means specifies an intersection of said boundary line images at a plurality of rotation positions as a position of said rotation axis. 7. The moving means calculates a shift amount between the center of the image of the optical member in the image and the position of the rotation axis, and calculates a shift amount of the optical member corresponding to the shift amount. The optical member inspection apparatus according to claim 1, wherein the optical member is moved according to the amount of movement. 8. The optical member inspection apparatus according to claim 7, wherein the moving means calculates the moving amount by dividing the moving amount into two orthogonal components in a plane orthogonal to the rotation axis. 9. An optical member inspection apparatus for detecting an optical defect of an optical member, comprising: a diffusing plate illuminated by illumination light; a diffusing plate disposed at a focal position of an optical system including the optical member; A light-shielding unit that is in contact with the diffusion plate so as to partially transmit and partially shield the diffused light; and a part of the light-shielding unit that partially transmits the light and a part that partially shields the light. A rotation unit that rotates the light blocking unit about a rotation axis that is in contact with a boundary line of the image capturing unit; an imaging unit that captures light transmitted through the optical system; and an image of the optical member in an image captured by the imaging unit. An optical member inspection apparatus, comprising: moving means for moving an optical axis of the optical system so that a center and a position of the rotation axis coincide with each other.