JP2014062862A - Product inspection system, product inspection method and product inspection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a product inspection system, a product inspection method and a product inspection that can surely and accurately detect a part different in a material when an inside of a hole of a product is inspected, a surface of the product is rough or the like, in a product made of more than two different materials.SOLUTION: A product inspection system 1 is configured to include: a light emission part 5 that irradiates a work with a rotary polarization; a linear polarizer 6 that converts light reflected by the work to a linear polarizer; and a phase setting mechanism 9 for setting a relative phase relation between the light emission part 5 and the linear polarizer 6 centering around an optical axis. The relative phase relation is adjusted by using the phase setting mechanism 9, so that the product inspection system 1 is configured to enable, out of light passing through the linear polarizer 6, light from a first surface and light from a second surface to be made different in a color.

Description

  The present invention relates to a product inspection system, a product inspection method, and a product inspection apparatus using polarized light.

  Conventionally, when different parts of the product surface material, for example, a metal part and a resin part are detected, for example, as described in Patent Document 1, linearly polarized light is irradiated on the product, and the reflected light from the product is applied to the part. A method of converting to linearly polarized light that is substantially orthogonal to the linearly polarized light is used.

  In this type of inspection method, the reflected light from the metal part is reflected in a state where the polarization is preserved, and the reflected light from the resin part is reflected in a state where the polarization is not preserved. .

  However, when the inside of a product hole is inspected, there is a case where both cannot be sufficiently detected.

  FIG. 12 is a captured image using a conventional surface inspection method. The image captures the bottom surface of the hole provided in the product, but the metal portion and the resin portion cannot be distinguished and detected.

  On the other hand, in the field of biopsy, for example, as described in Patent Document 2, the surface of the living body is irradiated with, for example, circularly polarized light, and the circularly polarized light reflected from the surface of the living body is converted into linearly polarized light and received. A method of detecting normal cells and abnormal cells using the property of circular dichroism is known. Circular dichroism is observed by irradiating a material having light-transmitting properties (for example, protein) with circularly polarized light, and either clockwise or counterclockwise circularly polarized light is absorbed by the material. The color is different.

  However, since metals and resins detected in product inspection do not have light-emitting properties in the first place, even if the method described in Patent Document 2 is used as it is, it can detect different parts of the product surface material. I can't.

  Therefore, as a result of extensive research conducted by the inventor of the present application, even in a product made of two or more different materials that do not have light application properties, by using rotationally polarized light, the different parts of the material can be distinguished and detected. I got the idea that Note that the rotationally polarized light refers to polarized light whose plane of polarization rotates as it passes through the medium. The circularly polarized light is referred to as circularly polarized light, and the elliptically polarized light is referred to as elliptically polarized light.

JP 2009-99788 A JP 2012-10663 A

  The present invention has been made based on the above idea, and in a product made of two or more different materials, even when the inside of a product hole is inspected, it is possible to reliably detect portions of different materials. A product inspection system, a product inspection method, and a product inspection device are provided.

  A product inspection system according to the present invention includes a light emitting unit that irradiates a workpiece having at least two types of surfaces in different states with rotationally polarized light, a linear polarizer that converts light reflected by the workpiece into linearly polarized light, and A phase setting mechanism for setting a relative phase relationship centered on the optical axis of the light emitting part and the linear polarizer, and adjusting the relative phase relationship using the phase setting mechanism, Of the light that has passed through the linear polarizer, the light from the first surface and the light from the second surface can be made different in color.

  According to such a system, by adjusting the relative phase relationship between the light emitting portion and the linear polarizer, it is possible to color only the reflected light from the surface that preserves the polarization of the light that has passed through the linear polarizer. It is possible to distinguish and detect at least two types of surfaces in different states.

Here, when inspecting the inside of a hole of a product, if an inspection method that blocks a specific polarization direction out of the linearly polarized light reflected from the product by irradiating the product with linearly polarized light as inspection light, The reflected light from the surface that preserves the polarization may cause irregular reflection in a polarization direction different from that of the incident light, and the polarization itself may be released while repeating irregular reflection in the hole.
However, the inventor of the present application utilizes the property that rotational polarization is easier to preserve the polarization state than linearly polarized light, and by using rotational polarization as inspection light, even when inspecting the inside of a hole in a product, the state differs at least. Two types of surfaces can be distinguished and detected.
Therefore, this system can be used particularly suitably when inspecting the inside of a product hole.

  In the case of the above-described configuration, it is preferable that the light emitting unit includes an LED and a rotating polarizing member that converts the light emitted from the LED into rotating polarization.

  As a modified example of the product inspection system according to the present invention, a light emitting unit for irradiating a workpiece having at least two types of surfaces in different states with linearly polarized light, and a rotating polarizer for converting light reflected by the workpiece into rotating polarized light And a phase setting mechanism for setting a relative phase relationship about the optical axis between the light emitting portion and the rotating polarizer, and setting the relative phase relationship using the phase setting mechanism. Thus, the light that has passed through the rotating polarizer can be configured such that the light from the first surface and the light from the second surface can have different colors.

  Even with such a system, by adjusting the phase relationship between the light emitting portion and the rotating polarizer, it is possible to color only the reflected light from the surface that preserves the polarization of the light that has passed through the rotating polarizer.

  In the case of the configuration described above, it is preferable that the light emitting unit includes an LED and a linearly polarizing member that linearly polarizes light emitted from the LED.

  In order to automatically discriminate between two types of materials using image processing technology, a light receiving unit that receives light passing through the linear polarizer as an electrical signal, and a first signal based on the electrical signal received by the light receiving unit. It is preferable to further include a color discriminating unit for discriminating colors of the light from the second material and the light from the second material.

  If this is the case, the light that has passed through the linear polarizer is received as an electrical signal, and the obtained data can be subjected to filter processing, binarization processing, and the like in the color identification unit. The light from the first material and the light from the second material of the workpiece can be selected.

  As a product inspection method according to the present invention, a work having at least two types of surfaces in different states is irradiated with rotationally polarized light, light reflected by the work is converted into linearly polarized light, and the rotationally polarized light and linearly polarized light are converted. And the light from the first surface and the light from the second surface in the linearly polarized light are made different in color from each other. 2 can be used.

  As a modification of the product inspection method according to the present invention, a linearly polarized light is irradiated to a workpiece having at least two types of surfaces in different states, and the light reflected by the workpiece is converted into a rotationally polarized light. By setting a relative phase relationship around the optical axis between the first polarized light and the rotationally polarized light, the light from the first surface and the light from the second surface in the rotationally polarized light are made different in color. The thing which discriminate | determines a surface and said 2nd surface can be mentioned.

  As a specific light emitting device for realizing the product inspection system and method according to the present invention in a compact configuration, the light source main body having a ring shape and the light emitting surface formed on the bottom surface matches the central axis. A rotating polarizer having a ring shape attached to the light emitting surface of the light source body, a linear polarizer attached so as to close a central hole of the light source body, and between the light source body and the rotating polarizer, or It is preferable to include a phase setting mechanism that is formed between the light source body and the linear polarizer and holds the rotating polarizer or the linear polarizer in a rotatable manner on the light source body.

  More specifically, the light source body is preferably composed of a casing and an LED attached to the bottom of the casing.

  According to the present invention, in a product made of at least two or more different materials, even when the inside of a product hole is inspected, it is possible to accurately detect portions of different materials using rotationally polarized light.

It is sectional drawing of the product inspection system in 1st Embodiment of this invention. It is a top view of the light emission apparatus in 1st Embodiment of this invention. It is the picked-up image which passed through the image processing apparatus of the test | inspection system of this invention. It is a picked-up image using the product inspection system of this invention. It is a picked-up image using the product inspection system of this invention. It is a schematic diagram explaining circularly polarized light and elliptically polarized light of the present invention. It is sectional drawing which shows the light emission apparatus in 2nd Embodiment of this invention. It is sectional drawing which shows the light emission apparatus in 3rd Embodiment of this invention. It is a schematic diagram which shows the optical path of the product inspection system in other embodiment of this invention. It is a schematic diagram which shows the optical path of the product inspection system in other embodiment of this invention. It is a schematic diagram which shows the optical path of the product inspection system in other embodiment of this invention. It is a picked-up image using the conventional product inspection system.

  The product inspection system of the present invention is for inspecting the product surface in a product composed of at least two different materials such as a metal whose surface preserves polarized light and a resin whose surface does not preserve polarization, such as a resin. It is. In particular, when a bottom surface in a hole formed in a product is detected, a resin is attached to the bottom surface, and the resin is detected separately from surrounding metal parts. In addition, it can be used suitably also when the product surface is rough.

  A first embodiment of this product inspection system will be described below with reference to the drawings.

  As shown in FIG. 1, the product inspection system 1 in the first embodiment includes a light emitting device 2 that emits light to a workpiece that is a product, and light that is emitted from the light emitting device 2 and reflected by the workpiece as image data. As a light receiving unit 3 and an image processing device 4 that performs image processing on data obtained from the light receiving unit 3.

  The light emitting device 2 includes a light emitting unit 5 that emits rotationally polarized light onto a work, and a linear polarizer 6 that directly converts light emitted from the light emitting unit 5 and reflected by the work into polarized light.

  The light emitting unit 5 is formed between the light source body 7 that emits light, the rotating polarization member 8 that converts the light emitted from the light source body 7 into rotating polarized light, and the light source body 7 and the rotating polarizing member 8. And a phase setting mechanism 9 that rotatably supports the rotating polarization member 8 on the light source body 7.

  The light source body 7 has, for example, a ring shape having a center hole H1, and a casing 7a in which a recess for accommodating the LED 7b is formed on the bottom surface on the work side, and a concentric circle centering on the axis C of the casing 7a in the recess. It is comprised with several LED7b arrange | positioned. In this embodiment, the LED 7b uses a bullet type, but may be a chip type or the like. And by arrange | positioning LED7b in the recessed part of the casing 7a, the bottom face of the casing 7a becomes a light emission surface which inject | emits light.

  The rotating polarizing member 8 is configured by combining, for example, a linear polarizing plate and a phase difference plate, and has a disk shape having a center hole H 2, and the axis C thereof is the axis C of the light source body 7. And is attached so as to cover the bottom surface of the casing 7a. The rotating polarizing member 8 has a function of converting light in a certain wavelength region into circularly polarized light out of light emitted from the light source body 7, and converting light in other wavelength regions into elliptically polarized light, Although it is the same as the rotating polarizer 13 described later, in order to avoid confusion, a different word is used here.

  As shown in FIG. 2, the linear polarizer 6 is, for example, a substantially rectangular (square) plate member attached to the casing 7 a so as to close the central hole H <b> 1 of the casing 7 a disposed on the light receiving unit 3 side.

  The phase setting mechanism 9 includes, for example, a rotating collar or groove provided on the casing 7a side, and an engaging portion of a rotating ridge provided on the rotating polarizing member 8 side and slidably engaged with the collar or groove. In addition, it further includes a rotation restricting mechanism for restricting rotation using a set screw or the like provided at an appropriate place. And this phase setting mechanism 9 has the outer peripheral surface of the rotating polarizing member 8, for example, and is comprised so that an operator can rotate.

  In the present embodiment, the phase setting mechanism 9 is provided between the casing 7a and the rotating polarizing member 8, but this is provided between the casing 7a and the linear polarizer 6, and the linear polarizer 6 is provided. You may comprise so that rotation with respect to the light source main body 7 may be carried out, and you may comprise both the rotation polarizing member 8 and the linear polarizer 6 so that rotation with respect to the light source main body 7 is possible.

  In the above configuration, the relative phase relationship between the rotating polarizing member and the linear polarizer is set at the time of workpiece inspection, but the relative phase relationship between the rotating polarizing member and the linear polarizer is previously set at the time of manufacturing the product inspection system. You can set it. In this case, the phase setting mechanism includes a structure for fixing the rotating polarizing member to the casing at a preset position, for example, a positioning mechanism formed between the casing and the rotating polarizing member, or a fixing member such as a screw or an adhesive. It is done.

  In the above configuration, the rotating polarizing member and the linear polarizer are fixed to the casing and held as a single unit, but the linear polarizing member or the rotating polarizing member is configured as a separate body without being fixed to the casing, At the time of inspection, for example, it may be attached to and held on a support member provided on an inspection table or the like. In this case, the phase setting mechanism includes a rotating mechanism that is formed between the supporting member and the rotating polarizing member or between the supporting member and the linear polarizer, and holds the rotating polarizing member or the linear polarizer rotatably with respect to the optical axis. Can be mentioned.

  The phase setting mechanism is not limited to the above configuration, and any configuration may be used as long as it is for setting the relative phase relationship around the optical axis between the rotating polarizing member and the linear polarizer.

  The light receiving unit 3 is an imaging device such as a CCD or CMOS type color camera. In the present embodiment, the linear polarizer 6 is provided in the light emitting device 2, but the linear polarizer 6 may be provided in the light receiving unit 3.

  The image processing apparatus 4 is configured by a digital or analog electric circuit having a CPU, a memory, or the like, or a part or all of a general-purpose computer such as a personal computer is used. Then, a predetermined program is stored in the memory, and the function as the color identification unit 40 is exhibited by operating the CPU or the like in cooperation with the program.

  Specifically, the color identification unit 40 performs a binarization process on the data obtained by the filter processing unit 40a that performs filter processing such as RGB separation on the image data obtained by the light receiving unit 3, and the filter processing unit 40a. And a binarization processing unit 40b to be performed.

  An example of the operation will be described. First, the filter processing unit 40a generates image data representing the light intensity of each portion divided for each of the three primary colors of RGB.

  Thereafter, by subtracting the light intensity of each image data obtained from the filter processing unit 40a by the binarization processing unit 40b, the image data in which a specific color (for example, red) has a stronger difference than the other colors is obtained. Extract. This is a binarization process, and FIG. 5 shows a captured image that has passed through the image processing apparatus 4. As shown in FIG. 5, the metal portion colored in a specific color is black because image data is extracted, and the resin portion not colored is white. This makes it possible to automatically distinguish a metal portion colored in a specific color (for example, red) from the resin portion.

In the product inspection system 1 according to the present embodiment, the light emitted from the light emitting unit 5 is converted into the rotationally polarized light by the rotating polarizing member 8 and irradiated onto the work, and the reflected light from the work is the central hole of the rotating polarizing member 8. The light passes through H2 and the central hole H1 provided in the casing 7a of the light emitting portion 5, and is converted into linearly polarized light by the linear polarizer 6.
At this time, when the light emitted from the light emitting part 5 is reflected by the work, the reflected light from the metal part causing specular reflection is in a state of maintaining the polarization, whereas from the resin part causing the diffuse reflection. The reflected light is in a state where the polarization is not preserved.
Then, one or both of the rotating polarizing member 8 and the linear polarizer 6 is rotated with respect to the light source body 7 to set a relative phase relationship around the optical axis between the rotating polarizing member 8 and the linear polarizer 6. Thereby, only the reflected light can be colored into the light of a specific wavelength region from the metal part which preserve | saves polarized light among the light which passed through the linear polarizer 6. FIG. As described above, when the relative phase relationship between the rotating polarizing member and the linear polarizer is set at the time of inspection, the inspection can be performed according to various works.
If the relative phase relationship between the rotating polarizing member and the linear polarizer is set in advance during the manufacture of the product inspection system, the polarized light out of the light that has passed through the linear polarizer is stored without any operation. Only the reflected light from the metal portion to be colored can be colored into light of a specific wavelength range. Thus, when the relative phase relationship between the rotating polarizing member and the linear polarizer is set in advance, the inspection can be easily performed without any operation.
The reason why the reflected light from the metal part that preserves the polarization is colored will be described later.

  3 and 4 are images obtained by imaging the inside of a hole provided in a product made of different materials such as metal and resin, using the product inspection system 1 according to the present embodiment. As shown in FIGS. 3 and 4, the metal portion is colored with light of a specific wavelength range of red or blue because the polarization state is preserved, but the resin portion is colored because the polarization state is not preserved. Has not been made.

  As described above, the product inspection system 1 of the present embodiment has a configuration for automatically determining this, but the operator may determine with the naked eye.

The reason why the metal part of the workpiece is colored will be described.
The light transmitted through the rotating polarization member 8 is converted into light having a specific wavelength region (for example, green light in the vicinity of 550 nm) into circularly polarized light, and the phase difference of light in other wavelength regions changes due to the difference in refractive index depending on the wavelength. Is converted into elliptically polarized light. The elliptically polarized light in the red wavelength region (for example, around 630 nm) and the elliptically polarized light in the blue wavelength region (for example, near 470 nm) are, as shown in FIG. The opposite direction.
Here, by rotating one or both of the rotating polarizing member 8 and the linear polarizer 6 with respect to the light source body 7, for example, as shown in FIG. 6B, the vibration direction of the light transmitted by the linear polarizer 6 and When the relative phase relationship between the rotating polarizing member 8 and the linear polarizer 6 is set so that the major axis direction of the elliptically polarized light in the red wavelength region coincides, the elliptically polarized light in the red wavelength region becomes elliptically polarized in the blue wavelength region. Since the amount of light transmitted through the linear polarizer 6 is larger than that of circularly polarized light in the green wavelength region, the light reflected from the metal portion that has passed through the linear polarizer 6 is predominately colored in the red wavelength region. . The major axis direction of the elliptically polarized light in the blue wavelength region may be set so that the vibration direction of the light transmitted by the linear polarizer 6 matches. In this case, the reflected light from the metal part is colored blue.

  According to such a system, the linear polarizer can be adjusted by adjusting the phase relationship between the light emitting portion 5 and the linear polarizer 6 even if it is in the hole of the product or the surface of the product is rough. Only the reflected light from the metal part that preserves the polarization of the light having passed through 6 can be colored, and two types of surfaces with different states of the metal part that preserves the polarization of the product and the resin part that does not preserve the polarization are distinguished. It can be detected separately.

The system is also considered particularly suitable for inspecting the inside of product holes. The reason is as follows.
When inspecting the hole in the product, if linearly polarized light with a constant polarization direction is used as the incident light to the product, the shape of the hole in a plan view is a perfect circle or a side perpendicular to the polarization direction of the incident light If the shape of the hole is other than that, the reflected light is reflected by the incident light when the reflected light from the metal portion preserves the polarization direction of the incident light. This causes irregular reflection with a different polarization direction, and the polarization of the reflected light itself may be canceled while the irregular reflection is repeated many times in the hole.
However, this system uses rotationally polarized light whose polarization direction is not constant for the incident light on the product. Therefore, compared to linearly polarized light, irregular reflection is prevented regardless of the shape of the hole, and the reflected light from the metal part is incident light. The polarization direction can be preserved.
For this reason, this system can detect the surface that preserves polarized light and the surface that does not preserve polarized light by detecting the inside of the hole of the product because of the difference in the polarization state of the reflected light. Can be used particularly suitably for the inspection.

  Next, a second embodiment of the product inspection system will be described below with reference to the drawings.

  As shown in FIG. 7, the product inspection system according to the second embodiment is a modification of the configuration of the light emitting device 2 described above, in which the positional relationship between the rotating polarizing member 8 and the linear polarizer 6 is reversed. It is. The rotating polarizing member 8, the rotating polarizer 13 and the linear polarizer 6 described later, and the linear polarizing member 12 described later are equivalent.

  As shown in FIG. 7, the light emitting device 10 includes a linearly polarizing member 12 in a light emitting unit 11 that emits linearly polarized light to a workpiece, and rotationally polarizations light emitted from the light emitting unit 11 and reflected by a product. Rotating polarizer 13 for converting to The linearly polarizing member 12 has a function of converting light emitted from the light source body 7 into linearly polarized light having a specific polarization direction, and is equivalent to the linear polarizer 6 described above, but avoids confusion. For this reason, the terminology used here is different.

  In the present embodiment, the phase setting mechanism 14 is formed between the casing 7 a and the linearly polarizing member 12 and rotatably supports the linearly polarizing member 12, but between the casing 7 a and the rotating polarizer 13. The rotary polarizer 13 formed may be configured to be rotatable, or both the linearly polarizing member 12 and the rotary polarizer 13 may be configured to be rotatable on the light source body 7. That is, as described in paragraphs [0036] to [0038], the phase setting mechanism 14 may have any configuration as long as it is for setting the relative phase relationship between the linearly polarizing member 12 and the rotating polarizer 13. I do not care.

  Even in such a system, only the reflected light from the metal portion of the light passing through the rotating polarizer 13 can be colored, and the metal portion and the resin portion of the product can be distinguished and detected.

  Next, a third embodiment of the product inspection system will be described.

  As shown in FIG. 8, the product inspection system according to the third embodiment includes a linear polarizer 15 that converts light that has passed through the rotating polarizer 13 into linearly polarized light in the light emitting device 10 according to the second embodiment. Is attached to the light receiving unit 3 side.

  In the case of this embodiment, although not shown, either the rotating polarizer 13 or the linear polarizer 15 may be rotatably supported by the phase setting mechanism 14, or the rotating polarizer 13 and the linearly polarized light may be supported. Both of the children 15 may be rotatably supported by the phase setting mechanism 14.

  Even in such a system, only the reflected light from the metal part of the light passing through the linear polarizer 15 can be colored, and the metal part and the resin part of the product can be distinguished and detected.

  Other embodiments include the following.

  In each of the above embodiments, the rotating polarizing member 8 and the linear polarizer 6 are arranged so that the light emitted from the light emitting device 2 and the light reflected by the workpiece and received by the light receiving unit 3 are coaxial. However, as shown in FIG. 9, the rotating polarization member 8 and the linear polarizer 6 may be arranged on the optical path between the light emitting unit 5 and the light receiving unit 3 instead of being coaxial.

  Similarly, as shown in FIG. 10 or FIG. 11, the linearly polarizing member 12 and the rotating polarizer 13 (and the linear polarizer 15) may be disposed on the optical path between the light emitting unit 11 and the light receiving unit 3. .

  In each of the above-described embodiments, the white light emitting LED 7b is used for the light source body 7. However, if the surface color that does not preserve the polarization of the product and the color of the light emission wavelength region are not similar, a single color light emitting LED is used. You can also. As a specific example, when the surface color that does not preserve polarized light is a color in the blue light emission wavelength region, a red light emitting LED is used for the light source body 7. Accordingly, at least two surfaces having different materials can be distinguished and detected from the difference in light color at low cost.

  Further, in each of the above-described embodiments, the light of the specific wavelength region converted into the circularly polarized light by the rotating polarization member 8 is the light of the green wavelength region, but the light of the red or blue wavelength region is the circularly polarized light, The light in the wavelength region may be converted into elliptically polarized light.

  Note that the present invention is not limited to the above-described embodiment and the modified examples of the present embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Product inspection system 2, 10 ... Light emission apparatus 3 ... Light-receiving part 4 ... Color identification part 5, 11 ... Light emission part 6, 12 ... Linear polarizer (linearly polarized light) Element)
7 ... Light source body 7a ... Casing 7b ... LED
8, 13 ... Rotating polarizing member (rotating polarizer)
9, 14 ... Phase setting mechanism

Claims (10)

A light emitting section for irradiating a work having at least two types of surfaces in different states with rotationally polarized light;
A linear polarizer that converts light reflected by the workpiece into linearly polarized light;
A phase setting mechanism for setting a relative phase relationship around the optical axis of the light emitting unit and the linear polarizer;
By adjusting the relative phase relationship using the phase setting mechanism, the color of the light from the first surface and the light from the second surface among the light that has passed through the linear polarizer can be made different. Product inspection system configured to be able to. A light emitting unit that irradiates a workpiece with at least two types of surfaces in different states with linearly polarized light;
A rotating polarizer that converts light reflected by the workpiece into rotating polarized light;
A phase setting mechanism for setting a relative phase relationship around the optical axis of the light emitting unit and the rotating polarizer;
By adjusting the relative phase relationship using the phase setting mechanism, the color of the light from the first surface and the light from the second surface among the light that has passed through the rotating polarizer can be made different. Product inspection system configured to be able to. The first surface preserves polarized light;
3. The product inspection system according to claim 1, wherein the second surface does not preserve polarized light.   The product inspection system according to claim 1, wherein the light emitting unit includes an LED and a rotating polarization member that rotates the light emitted from the LED into rotationally polarized light.   The product inspection system according to claim 2, wherein the light emitting unit includes an LED and a linearly polarizing member that linearly polarizes light emitted from the LED. A light receiving unit that receives light passing through the linear polarizer as an electrical signal;
The color identification part which identifies the color of the light from the 1st material and the light from the 2nd material based on the electric signal received in the said light-receiving part is further provided. Product inspection system as described. Rotating polarized light is applied to a workpiece having at least two types of surfaces in different states,
While converting the light reflected by the workpiece into linearly polarized light,
Set a relative phase relationship around the optical axis of the rotationally polarized light and the linearly polarized light,
A product inspection method for discriminating between the first surface and the second surface by differentiating colors of light from the first surface and light from the second surface in the linearly polarized light. Irradiate a workpiece with at least two types of surfaces in different states with linearly polarized light,
While converting the light reflected by the workpiece into rotationally polarized light,
Set a relative phase relationship around the optical axis of the linearly polarized light and the rotationally polarized light,
A product inspection method for discriminating between the first surface and the second surface by differentiating light from the first surface and light from the second surface in the rotationally polarized light. A light source body having a ring shape and a light emitting surface formed on the bottom surface;
A rotating polarizer in the form of a ring attached to the light emitting surface of the light source body so that the central axis matches,
A linear polarizer attached to block the central hole of the light source body;
A phase setting mechanism that is formed between the light source body and the rotating polarizer or between the light source body and the linear polarizer, and rotatably holds the rotating polarizer or the linear polarizer on the light source body. A light emitting device comprising:   The light emitting device according to claim 9, wherein the light source body includes a casing and an LED attached to a bottom portion of the casing.