JP6940552B2 - Article inspection equipment and article inspection method - Google Patents

Description

The present invention relates to an article inspection device and an article inspection method, and more particularly to an article inspection apparatus and an article inspection method for inspecting a birefringent object to be inspected such as a transparent film or a film package.

Various techniques have been studied for the purpose of measuring the distribution of the birefringence phase difference of a measurement object having birefringence (see, for example, Patent Documents 1 to 3).

Patent Document 1 discloses an apparatus that measures the polarization state of a light flux transmitted or reflected from a measurement object at three or more types of analyzer angles and calculates the double refraction phase difference of the measurement object from each analyzer output. Has been done.

In Patent Document 2, a plurality of polarizers having different optical axes are formed in an array, and the intensity of light transmitted through them is collectively measured by a light receiving element array, and the optical axis azimuth angle and the light receiving intensity of the polarizer are measured. A device that performs ellipsometry from information and obtains the phase difference and principal axis orientation from the change from the polarization state of incident light is disclosed.

Patent Document 3 describes a luminous flux irradiating means for irradiating a measurement object with a luminous flux in a predetermined polarized state, an imaging optical system for forming an image of a light beam transmitted through the measurement object on the imaging means, and an imaging optical system. The object to be measured is transmitted based on a polarizing diffraction grating that is arranged in the middle of the image and causes at least one diffracted light of a plurality of diffracted lights to enter the imaging means, and a light-dark signal regarding the brightness of the image generated by the imaging means. A device including an output means for outputting information on a phase difference in a diffracted luminous flux is disclosed.

Japanese Unexamined Patent Publication No. 2006-71458 Japanese Patent No. 5118311 International Publication No. 2016/031567

However, in the apparatus disclosed in Patent Document 1, it is not necessary to rotate the detector, but the double refraction phase difference of the object to be measured is calculated from the output of each detector measured at three or more types of detector angles. , There is a problem that the calculation takes time. Further, the apparatus disclosed in Patent Document 2 does not need to rotate the polarizer, but has a problem that it takes time to calculate the polarization because the polarization analysis is performed from the information of the light receiving intensity measured by a plurality of different polarizers. be. Further, the apparatus disclosed in Patent Document 3 does not require a rotation mechanism of a polarizer and does not require time for calculation, but has a problem that it requires an expensive and special polarizing diffraction grating. That is, the conventional device for measuring the distribution of the birefringence phase difference of the object to be inspected having birefringence as disclosed in Patent Documents 1 to 3 requires time for measurement and can be realized at low cost. There wasn't.

The present invention has been made to solve such a conventional problem, and has a simple and inexpensive configuration using a general-purpose optical component without a rotation mechanism, and has a birefringence of a plurality of objects to be inspected. It is an object of the present invention to provide an article inspection apparatus and an article inspection method capable of inspecting the distribution of refraction phase difference at high speed.

In order to solve the above problems, the article inspection apparatus according to the present invention includes a transport unit that transports the object to be inspected to the inspection region, a light irradiation unit that outputs a linearly polarized light beam, and 1 / of the linearly polarized light beam. A first 1/4 wave plate that imparts a phase difference of four wavelengths to convert it into a circularly polarized light beam, and an irradiation optical system that irradiates the object to be inspected transported to the inspection region with the circularly polarized light beam. A second 1/4 wave plate that imparts a phase difference of 1/4 wavelength to the light beam that has passed through the object to be inspected, and a predetermined polarization component of the light beam that has passed through the second 1/4 wave plate. A first image sensor including an analyzer that passes through the detector, and a plurality of light receiving elements that output intensity signals according to the amount of light emitted from the light beam passing through the detector, the object to be inspected and the first imager conveyed to the inspection region. An image formed between the 2 1/4 wave plate and the light beam transmitted through the object to be inspected on the 1st image sensor via the 2nd 1/4 wave plate and the analyzer. A double-polarization phase difference distribution calculation unit that calculates the distribution of the double-reflecting phase difference of the object to be inspected from the optical system and the intensity signals output from each of the light receiving elements of the first image sensor, and the double-reflecting phase difference. A configuration including a determination unit for determining the quality of the object to be inspected based on a comparison between the distribution of the compound refraction phase difference calculated by the distribution calculation unit and a predetermined distribution of the desired compound refraction phase difference. Is.

With this configuration, the article inspection device according to the present invention has a configuration in which a second 1/4 wave plate is provided between the object to be inspected and the analyzer, and therefore, a general-purpose optical component having no rotating mechanism is used. With a simple and inexpensive configuration, the distribution of the birefringence phase difference of the object to be inspected having birefringence can be inspected at high speed. Further, the article inspection apparatus according to the present invention compares the distribution of the birefringence retardation calculated by the birefringence retardation distribution calculation unit with a predetermined distribution of the desired birefringence retardation to be inspected. Can be judged as good or bad.

Further, the article inspection apparatus according to the present invention is arranged between the imaging optical system and the second 1/4 wavelength plate, and has an optical branching device for branching a light flux from the imaging optical system and an input. From the second image sensor including a plurality of light receiving elements that output intensity signals according to the amount of light of the light beam and the intensity signals output from each of the light receiving elements of the second image sensor, the appearance of the object to be inspected The imaging optical system further includes an image generating unit for generating an image, and the imaging optical system transmits one light flux branched by the optical branching device via the second 1/4 wavelength plate and the analyzer. One image sensor is imaged, and the other light flux branched by the optical branching device is imaged on the second image sensor, and the determination unit is generated in advance with the image generated by the image generation unit. The quality of the inspected object may be determined based on the comparison with the image of the good sample of the inspected object.

With this configuration, the article inspection device according to the present invention includes a second 1/4 wave plate and a second image sensor that receives a light flux from the imaging optical system without using an analyzer. In addition to the inspection of the birefringence of the object to be inspected based on the intensity signal from the image sensor, the appearance of the object to be inspected can be inspected based on the intensity signal from the second image sensor.

Further, in the article inspection device according to the present invention, the light irradiation unit may have a laser diode that outputs a linearly polarized light beam.

With this configuration, the article inspection apparatus according to the present invention can output the linearly polarized light flux to the first 1/4 wave plate without using a polarizer for generating the linearly polarized light beam.

Further, the article inspection method according to the present invention includes a step of transporting the object to be inspected to the inspection region, a step of outputting a linearly polarized light beam, and 1/4 of the linearly polarized light beam by a first 1/4 wave plate. A step of imparting a phase difference of four wavelengths to convert the light beam into circularly polarized light, a step of irradiating the object to be inspected transported to the inspection region with the light beam of circularly polarized light, and a step of transmitting the object to be inspected. A step of imparting a phase difference of 1/4 wavelength to the light beam by a second 1/4 wave plate and a step of passing a predetermined polarization component of the light beam passing through the second 1/4 wave plate by an analyzer. And the light beam transmitted through the object to be inspected by the imaging optical system arranged between the object to be inspected and the second 1/4 wave plate conveyed to the inspection area. A step of forming an image on the first image sensor via the / 4 wave plate and the detector, and an intensity signal corresponding to the amount of light emitted from the light beam passing through the detector from the first image sensor including a plurality of light receiving elements. A step of calculating the distribution of the double-polarization phase difference of the object to be inspected from the output step and the intensity signal output from each of the light-receiving elements of the first image sensor, a double-reflecting phase difference distribution calculation step, and the double-reflecting position. A configuration including a step of determining the quality of the object to be inspected based on a comparison between the distribution of the double-polarized light retardation calculated by the phase difference distribution calculation step and a predetermined distribution of the desired double-polarized light phase difference. Is.

With this configuration, the article inspection method according to the present invention uses a general-purpose optical component without a rotating mechanism because a second 1/4 wave plate is provided between the object to be inspected and the analyzer. With a simple and inexpensive configuration, the distribution of the birefringence phase difference of the object to be inspected having birefringence can be inspected at high speed. Further, in the article inspection method according to the present invention, the object to be inspected is compared with the distribution of the birefringence retardation calculated by the birefringence retardation distribution calculation unit and a predetermined distribution of the desired birefringence retardation. Can be judged as good or bad.

The present invention is an article inspection device and an article capable of inspecting the distribution of the birefringence phase difference of an object to be inspected having birefringence at high speed with a simple and inexpensive configuration using general-purpose optical components without a rotation mechanism. It provides an inspection method.

It is a block diagram of the article inspection apparatus which concerns on 1st Embodiment of this invention. It is a block diagram which shows the structural example of the light irradiation part in the article inspection apparatus which concerns on 1st Embodiment of this invention. It is a figure for demonstrating the polarization state of a light wave. In the article inspection apparatus according to the first embodiment of the present invention, the slow axis and the fast axis of the first 1/4 wave plate, the slow axis and the fast axis of the object to be inspected, and the second 1/4 wave plate. It is a figure which shows the direction of the slow axis and the fast axis of, and the transmission axis of an analyzer. It is a figure for demonstrating the change of the polarization state of the circularly polarized light flux incident on an object to be inspected. It is a figure which shows the Poincare sphere for demonstrating the polarization state of the light flux propagated in the article inspection apparatus which concerns on 1st Embodiment of this invention. It is a graph for demonstrating the light intensity indicated by the intensity signal output from the 1st image sensor in the article inspection apparatus which concerns on 1st Embodiment of this invention. It is a block diagram which shows the structure of the processing part in the article inspection apparatus which concerns on 1st Embodiment of this invention. It is a flowchart for demonstrating the process of the article inspection method using the article inspection apparatus which concerns on 1st Embodiment of this invention. It is a block diagram of the article inspection apparatus which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the structure of the processing part in the article inspection apparatus which concerns on 2nd Embodiment of this invention.

Hereinafter, embodiments of the article inspection apparatus and the article inspection method according to the present invention will be described with reference to the drawings. The article inspection device and the article inspection method according to the present invention are for inspecting the distribution of the birefringence phase difference of an object to be inspected having birefringence such as a transparent film or a film package.

(First Embodiment)
As shown in FIG. 1, the article inspection device 1 according to the first embodiment of the present invention includes a light irradiation unit 10, a first 1/4 wave plate 11, an irradiation optical system 12, and an imaging optical system. 13, the second 1/4 wave plate 14, the analyzer 15, the first image sensor 16, the first light intensity detection unit 17, the transport unit 30, the control unit 40, the display unit 50, and so on. It includes an operation unit 60. The first 1/4 wave plate 11, the irradiation optical system 12, the imaging optical system 13, the second 1/4 wave plate 14, and the analyzer 15 are optical paths from the light irradiation unit 10 to the first image sensor 16. They are arranged in this order.

The light irradiation unit 10 outputs a linearly polarized light flux, and includes a light source 10a and a collimating lens 10b that collimates the light flux from the light source 10a. The light source 10a is, for example, a laser diode (LD) that outputs a linearly polarized laser luminous flux.

Alternatively, as shown in FIGS. 2A and 2B, a Super Luminescent Diode (SLD) 10c or a Light Emitting Diode (LED) is used as the light source of the light irradiation unit 10 instead of the LD10a. 10d may be used. In this case, in the light irradiation unit 10, a polarizer 10e that converts the luminous flux from the SLD 10c or the LED 10d into a linearly polarized luminous flux is further provided after the collimating lens 10b.

The first 1/4 wave plate 11 imparts a phase difference of 1/4 wavelength to the linearly polarized light flux output from the light irradiation unit 10 and converts it into a circularly polarized light flux. The first 1/4 wave plate 11 is arranged so that its slow axis forms an angle of 45 ° (or −45 °) with respect to the vibration direction of the linearly polarized light beam output from the light irradiation unit 10. NS.

The irradiation optical system 12 irradiates the object to be inspected W conveyed to the inspection region R with a circularly polarized light flux output from the first 1/4 wave plate 11. The irradiation optical system 12 has, for example, two or more lenses in order to expand the circularly polarized light flux according to the size of the object W to be inspected.

The imaging optical system 13 is arranged between the object W to be inspected and the second 1/4 wave plate 14 conveyed to the inspection area R, and the light flux transmitted through the object W to be inspected is transmitted to the second 1/4. An image is formed on the first image sensor 16 via the wave plate 14 and the analyzer 15.

The second 1/4 wave plate 14 imparts a phase difference of 1/4 wavelength to the light flux transmitted through the object W to be inspected and the imaging optical system 13.

The analyzer 15 passes a predetermined polarization component of the luminous flux that has passed through the second quarter wave plate 14. The detector 15 is arranged so that its transmission axis forms an angle of 45 ° (or −45 °) with respect to the slow axis of the second 1/4 wave plate 14. Examples of the analyzer 15 and the polarizer 10e include Wollaston Prism, Rochon Prism, Glan-Taylor Prism, Glan-Laser Prism, and Gran. A crystal polarizer such as Glan-Thompson Prism can be preferably used.

The first image sensor 16 includes a plurality of light receiving elements that output an intensity signal according to the amount of light of a light beam passing through the analyzer 15. That is, this intensity signal is a signal corresponding to the brightness of the image formed by the imaging optical system 13.

The first light intensity detection unit 17 detects the light intensity from the intensity signals output from each light receiving element of the first image sensor 16.

The transport unit 30 is, for example, a belt conveyor that transports the object W to be inspected to the inspection area R at predetermined intervals along a predetermined transport direction (x direction). In the transport unit 30, for example, an endless transport belt 31 is wound around the transport rollers 32a and 32b, and a plurality of objects W to be inspected are set in the inspection region R in the transport path 30a formed by the transport belt 31. It is designed to be transported in sequence. Further, the transport unit 30 is provided with a motor 34 for rotating the transport belt 31 at one end in the axial direction of the transport roller 32b. The motor 34 is driven and controlled by the control unit 40. The transport belt 31 is made of, for example, a light transmitting belt.

Hereinafter, the polarized state of the light wave propagating in the article inspection device 1 according to the present embodiment will be described. As shown in FIG. 3A, when the traveling direction of the light wave is the z-axis and the axes orthogonal to each other on the plane perpendicular to the z-axis are the x-axis and the y-axis, the electric vector of the light wave (monochromatic light) is drawn. The locus is represented by the following equation (1).

ここで、光波の水平方向（ｘ方向）成分の初期位相をδ_ｘ、光波の垂直方向（ｙ方向）成分の初期位相をδ_ｙ、これらの位相差δをδ_ｙ−δ_ｘとすると、光波の電気ベクトルの軌跡は、位相差δに応じて図３（ｂ）に示すように変化する。

Here, if the initial phase of the horizontal (x-direction) component of _{the light wave is δ x} , the initial phase of the vertical (y-direction) component of the light wave is δ _y , and the phase difference δ of these is δ _{y −} δ _x , the light wave The locus of the electric vector of is changed as shown in FIG. 3B according to the phase difference δ.

FIG. 4 shows the directions of the slow and fast axes of the first 1/4 wave plate 11, the directions of the slow and fast axes of the object W to be inspected, and the slow and fast axes of the second 1/4 wave plate 14. It is a figure which shows the direction of the speed axis, and the direction of the transmission axis of an analyzer 15. Hereinafter, the polarization state of the luminous flux passing through each optical component will be described using a Jones vector and a Jones matrix.

In FIG. 4, it is assumed that the vibration direction of the electric field of the linearly polarized light flux output from the light irradiation unit 10 is parallel to the x-axis. Therefore, the polarization state _EL0 is represented by the following equation (2).

As shown in FIG. 4, in the first 1/4 wave plate 11 and the second 1/4 wave plate 14, the slow axis s is parallel to the x'axis and the speed axis f is parallel to the y'axis. Suppose that Here, the x'axis is tilted by −45 ° with respect to the x axis. The Jones matrix of the first 1/4 wave plate 11 and the second 1/4 wave plate 14 is represented by the following equation (3) in the x'y'coordinate system.

Therefore, when the linearly polarized light beam from the light irradiation unit 10 whose vibration direction is parallel to the x-axis passes through the first 1/4 wave plate 11 whose slow axis s is parallel to the x'axis, the x'y'coordinates. In the system, the polarized state represented by the following equation (4) is obtained.

式（４）は右回り円偏光を示している。

Equation (4) shows clockwise circularly polarized light.

The Jones matrix of the inspected object W uses the phase difference δ applied to the luminous flux transmitted through the inspected object W, that is, the birefringence retardation δ of the inspected object W in the sf coordinate system of the inspected object W. It is represented by the following equation (5).

Therefore, as shown in FIG. 4, when the slow axis s of the inspected object W forms an angle θ with respect to the x'axis, the polarization state of the light flux transmitted through the inspected object W is the polarization state of the inspected object W. It is represented by the following equation (6) in the sf coordinate system. The angle θ of the slow axis s with respect to the x'axis may be two-dimensionally distributed in the object W to be inspected.

Next, when the luminous flux transmitted through the object W to be inspected passes through the second 1/4 wave plate 14 whose slow axis s is parallel to the x'axis, the following equation (7) is used in the x'y' coordinate system. The represented polarization state is obtained.

As shown in FIG. 4, the transmission axis of the analyzer 15 is parallel to the x-axis. Therefore, the Jones matrix of the detector 15 is represented by the following equation (8) in the xy coordinate system.

Therefore, as shown in FIG. 4, when the transmission axis of the detector 15 is parallel to the x-axis (that is, an angle of 45 ° with respect to the x'axis), the polarized state of the light beam passing through the detector 15 is polarized. Is represented by the following equation (9) in the xy coordinate system.

Therefore, assuming that the light intensity of the linearly polarized light flux output from the light irradiation unit 10 is I ₀ , the light intensity of the light beam transmitted through the object W to be inspected and the linearly polarized light component in the horizontal direction is extracted by the analyzer 15 is , It is represented by the following equation (10). The light intensity I given by the formula (10) corresponds to the light intensity detected by the first light intensity detection unit 17.

From the result of the equation (10), if the configuration shown in FIG. 4 is used, the distribution of the magnitude of the birefringence phase difference δ in the inspected object W can be obtained regardless of the distribution in the direction of the slow axis s in the inspected object W. It can be seen that it can be detected as a distribution of light intensity. In the equation (10), the minimum value 0 is taken when the birefringence phase difference δ is ₀ , and the maximum value I 0 is taken when the birefringence phase difference δ is π.

The transmission axis of the analyzer 15 may form an angle of −45 ° with respect to the x'axis (that is, an angle of 0 ° with respect to the y-axis). In this case, the polarization state of the light flux passing through the analyzer 15 is represented by the following equation (11) in the xy coordinate system.

Therefore, assuming that the light intensity of the linearly polarized light flux output from the light irradiation unit 10 is I ₀ , the light intensity of the light beam transmitted through the object W to be inspected and the linearly polarized light component in the vertical direction is extracted by the analyzer 15 is , It is represented by the following equation (12). The light intensity I given by the formula (12) corresponds to the light intensity detected by the first light intensity detection unit 17.

From the result of the equation (12), even if the transmission axis of the analyzer 15 is parallel to the y-axis, birefringence in the object W to be inspected regardless of the distribution in the direction of the slow axis s in the object W to be inspected. It can be seen that the distribution of the magnitude of the phase difference δ can be detected as the distribution of light intensity. In the equation (12), the maximum value I ₀ is taken when the birefringence phase difference δ is 0, and the minimum value 0 is taken when the birefringence phase difference δ is π.

Note that the birefringent phase difference [delta], using the wavelength λ of the light beam of the linearly polarized light output from the light irradiation unit 10, a birefringence _{Δn (= n e -n o)} , the thickness d of the object W, It is expressed as in equation (13). Here, n _o is the ordinary refractive index, n _e is the extraordinary refractive index.

Therefore, when the thickness d of the inspected object W is constant, the distribution of the birefringence phase difference δ shows the distribution of the birefringence Δn in the inspected object W. On the other hand, when the birefringence Δn of the object W to be inspected is constant, the distribution of the birefringence phase difference δ shows the distribution of the thickness d in the object W to be inspected.

Here, with respect to the configuration in which the second 1/4 wave plate 14 is omitted from the configuration of FIG. 4, the polarization state of the light flux passing through each optical component will be described using a Jones vector and a Jones matrix. That is, the polarization of the luminous flux when the luminous flux in the polarized state given by the equation (6) is directly incident on the analyzer 15 whose transmission axis is parallel to the x-axis (that is, an angle of 45 ° with respect to the x'axis). The state is represented by the following equation (14) in the xy coordinate system.

From equation (14), it can be seen that when θ is 135 ° or 315 °, information on the birefringence phase difference δ cannot be obtained. Further, the luminous flux in the polarized state given by the equation (6) is directly incident on the analyzer 15 whose transmission axis is perpendicular to the x-axis (that is, an angle of −45 ° with respect to the x'axis). The polarized state is represented by the following equation (15) in the xy coordinate system.

From equation (15), it can be seen that when θ is 45 ° or 225 °, information on the birefringence phase difference δ cannot be obtained. Therefore, in order to obtain the distribution of the magnitude of the birefringence phase difference δ in the inspected object W regardless of the distribution in the direction of the slow axis s in the inspected object W, the second 1/4 wave plate 14 is used. The configurations of FIGS. 1 and 4 provided between the object W to be inspected and the analyzer 15 are desirable.

Hereinafter, the polarized state of the light flux passing through each optical component in the article inspection device 1 according to the present embodiment will be described using a Poincare sphere.

When a circularly polarized light beam is incident on the birefringent object W from the first 1/4 wave plate 11, for example, as shown in FIGS. 5A to 5E, the object W to be inspected is delayed. The polarization state changes according to the amount of the axis (or speed axis) orientation and the birefringence phase difference δ. These polarized states are represented on the Poincare sphere shown in FIG. In the Poincare sphere, the main axis direction of elliptical polarization is represented by longitude, and the elliptical ratio of elliptical polarization is represented by latitude. The linearly polarized light is arranged on the equator of the Poincare sphere.

For example, in the region where the lagging directions of the object W to be inspected are 0 °, -90 °, and -180 ° with respect to the horizontal direction, the birefringence position is as shown in FIGS. 5A, 5C, and 5E. by rotation about S ₁ axis of the Poincare sphere depending on the amount of phase difference [delta], it changes the polarization state of the right-handed circularly polarized light incident on the inspection object W. Further, in the region where the angles of the slow axis with respect to the horizontal direction are −45 ° and −135 ° in the object W to be inspected, as shown in FIGS. by rotation about S ₂ axis of the Poincare sphere Te, a change in the polarization state of the right-handed circularly polarized light incident on the inspection object W.

Then, when the polarization state of the light beam transmitted through the object W is elliptically polarized light or circularly polarized light, by the conversion of the polarization state of the around S ₂ axis by the second quarter-wave plate 14, the polarization state In addition to the ellipticity, the main axis orientation changes. For example, to convert the horizontal linearly polarized light circularly polarized in the second quarter wavelength plate 14, about the S ₂ axis, a phase difference a quarter wave length, that is, be rotated 90 °.

As described above, the polarization state of the luminous flux before conversion by the second 1/4 wave plate 14 becomes a state in which the principal axis orientation has changed after the conversion of the polarization state of the luminous flux by the second 1/4 wave plate 14. .. When the luminous flux whose principal axis direction has changed passes through the analyzer 15, the birefringence phase difference δ is converted into a change in light intensity, and the birefringence phase difference distribution can be observed from the intensity signal of the first image sensor 16. become.

FIG. 7 is a graph for explaining the light intensity indicated by the intensity signal output from the first image sensor 16. The solid line shows that when the circularly polarized light flux is output from the object W to be inspected, the polarization direction of the linearly polarized light flux output from the second 1/4 wave plate 14 and the transmission axis of the analyzer 15 are orthogonal to each other. The light intensity of the intensity signal in the configuration (see FIG. 4) is shown. In this configuration, as shown in the equation (10), the light intensity in the region where the birefringence phase difference δ did not occur in the inspected object W was the lowest, and the birefringence phase difference δ in the inspected object W was the lowest. The light intensity in the region of 180 ° is the highest. Further, the light intensity of the object W to be inspected increases monotonically as the birefringence phase difference δ increases.

Further, in FIG. 7, the broken line indicates the polarization direction of the linearly polarized light flux output from the second 1/4 wave plate 14 when the circularly polarized light beam is output from the object W to be inspected, and the polarization direction of the analyzer 15. It shows the light intensity of the intensity signal in a configuration in which the transmission axis is parallel to the transmission axis. In this configuration, as shown in the equation (12), the light intensity in the region where the birefringence phase difference δ did not occur in the inspected object W was the highest, and the birefringence phase difference δ in the inspected object W was the highest. The light intensity in the 180 ° region is the lowest. Further, the light intensity of the object W to be inspected decreases monotonically as the birefringence phase difference δ increases.

The control unit 40 is composed of, for example, a microcomputer including a CPU, ROM, RAM, HDD, or the like, a personal computer, or the like, and controls the operation of each of the above-mentioned units constituting the article inspection device 1. Further, the control unit 40 can configure the processing unit 41 by software by transferring a predetermined program stored in the ROM or the like to the RAM and executing the program. The processing unit 41 can also be configured by a digital circuit such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). Alternatively, the processing unit 41 can be configured by appropriately combining hardware processing by a digital circuit and software processing by a predetermined program.

As shown in FIG. 8, the processing unit 41 includes a first image generation unit 42, a birefringence phase difference distribution calculation unit 43, and a determination unit 44.

The first image generation unit 42 is adapted to generate an image composed of pixels having pixel values corresponding to the light intensity detected for each light receiving element by the first light intensity detection unit 17. As shown in the lower part of FIG. 7, the image generated by the first image generation unit 42 is a bright / dark image having a birefringence phase difference δ in the object W to be inspected.

The birefringence phase difference distribution calculation unit 43 determines the birefringence phase difference δ of the object W to be inspected from the light intensity detected for each light receiving element by the first light intensity detection unit 17 according to the formula (10) or the formula (12). The distribution of is calculated.

The determination unit 44 determines that the object W to be inspected is based on a comparison between the distribution of the birefringence phase difference δ calculated by the birefringence phase difference distribution calculation unit 43 and a predetermined distribution of the desired birefringence phase difference. It is designed to judge the quality. Here, the predetermined desired distribution of birefringence retardation is, for example, the distribution of birefringence retardation obtained from a non-defective sample of the object W to be inspected.

For example, in the determination unit 44, the absolute value of the difference between the birefringence phase difference δ calculated for each light receiving element by the birefringence phase difference distribution calculation unit 43 and a predetermined desired birefringence phase difference is set to a predetermined value. If it exceeds, it is determined that the object W to be inspected has an abnormality. Alternatively, the determination unit 44 determines the absolute difference between each pixel value of the image generated by the first image generation unit 42 and each pixel value of the bright / dark image corresponding to a predetermined distribution of the desired birefringence phase difference. When the value exceeds a predetermined value, it is determined that the object W to be inspected has an abnormality.

The display unit 50 is composed of a display device such as an LCD or a CRT, and according to a control signal output from the control unit 40, the determination unit 44 determines whether the object W is good or bad, and the first image generation unit. Various display contents such as an image generated by 42 are displayed. Further, the display unit 50 displays an operation target such as a button for setting various conditions, a soft key, a pull-down menu, and a text box.

The operation unit 60 is for receiving an operation input by the user, and is composed of, for example, a touch panel provided on the display unit 50. Alternatively, the operating unit 60 may be configured to include an input device such as a keyboard or mouse. Further, the operation unit 60 may be configured by an external control device that performs remote control by a remote command or the like. The operation input to the operation unit 60 is detected by the control unit 40. For example, the operation unit 60 allows the user to arbitrarily specify the start and stop of transportation of the object W to be inspected by the transportation unit 30.

Hereinafter, an example of the processing of the article inspection method using the article inspection device 1 according to the present embodiment will be described with reference to the flowchart of FIG.

First, the transport unit 30 transports the object W to be inspected to the inspection region R (step S1).

Next, the light irradiation unit 10 outputs a linearly polarized light flux (step S2).

Next, the first 1/4 wave plate 11 imparts a phase difference of 1/4 wavelength to the linearly polarized light flux output from the light irradiation unit 10 and converts it into a circularly polarized light flux (step S3). ..

Next, the irradiation optical system 12 irradiates the object W to be inspected transported to the inspection region R with a circularly polarized light flux output from the first 1/4 wave plate 11 (step S4).

Next, the second 1/4 wave plate 14 imparts a phase difference of 1/4 wavelength to the luminous flux transmitted through the object W to be inspected (step S5).

Next, the analyzer 15 passes a predetermined polarization component of the luminous flux that has passed through the second 1/4 wave plate 14 (step S6).

Next, the imaging optical system 13 forms an image of the luminous flux transmitted through the object W to be inspected on the first image sensor 16 via the second 1/4 wave plate 14 and the analyzer 15 (step S7).

Next, the first image sensor 16 outputs an intensity signal according to the amount of light of the luminous flux passing through the analyzer 15 (step S8).

Next, the birefringence phase difference distribution calculation unit 43 calculates the distribution of the birefringence phase difference δ of the object W to be inspected from the intensity signals output from each light receiving element of the first image sensor 16 (birefringence phase difference). Distribution calculation step S9).

Next, the determination unit 44 is inspected based on a comparison between the distribution of the birefringence phase difference δ calculated in the birefringence phase difference distribution calculation step S9 and a predetermined distribution of the desired birefringence phase difference. The quality of the object W is determined (step S10).

Next, the control unit 40 determines whether or not all the objects W to be inspected have been conveyed to the inspection area R (step S11). When all the objects W to be inspected are conveyed to the inspection area R, the control unit 40 ends the process. On the other hand, when all the objects W to be inspected are not conveyed to the inspection area R, the control unit 40 again executes the processes after step S1.

As described above, the article inspection device 1 according to the present embodiment has a second quarter between the object W to be inspected and the analyzer 15 in the optical path from the light irradiation unit 10 to the first image sensor 16. Since the configuration is provided with the wave plate 14, the distribution of the birefringence phase difference δ of the object to be inspected having birefringence can be inspected at high speed with a simple and inexpensive configuration using general-purpose optical components without a rotation mechanism. be able to. Further, the article inspection device 1 according to the present embodiment compares the distribution of the birefringence phase difference δ calculated by the birefringence phase difference distribution calculation unit 43 with a predetermined distribution of the desired birefringence phase difference. , It is possible to judge the quality of the object W to be inspected.

Further, in the article inspection device 1 according to the present embodiment, when the light irradiation unit 10 has the LD10a that outputs a linearly polarized light flux, the linearly polarized light is linearly polarized light without using a polarizer for generating the linearly polarized light flux. The luminous flux can be output to the first 1/4 wave plate 11.

(Second Embodiment)
Subsequently, the article inspection apparatus according to the second embodiment of the present invention will be described with reference to the drawings. The same components as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted as appropriate. Further, the description of the same operation as that of the first embodiment will be omitted as appropriate.

As shown in FIG. 10, in addition to the configuration of the article inspection device 1 of the first embodiment, the article inspection device 2 of the present embodiment includes an optical turnout 18, a second image sensor 19, and a second light intensity. A detection unit 20 is provided.

The optical turnout 18 is arranged between the imaging optical system 13 and the second 1/4 wave plate 14 in the optical path from the light irradiation unit 10 to the first image sensor 16, and is derived from the imaging optical system 13. The light beam is branched.

The imaging optical system 13 forms an image of one of the light fluxes branched by the optical turnout 18 on the first image sensor 16 via the second 1/4 wave plate 14 and the analyzer 15, and the optical turnout 18 The other light flux branched in is formed on the second image sensor 19.

The second image sensor 19 includes a plurality of light receiving elements that output an intensity signal corresponding to the amount of light of a luminous flux input from the imaging optical system 13 via the optical turnout 18.

The second light intensity detection unit 20 detects the light intensity from the intensity signals output from each light receiving element of the second image sensor 19.

Further, as shown in FIG. 11, the processing unit 41'in the article inspection device 2 of the present embodiment has a second image generation unit 45 in addition to the configuration of the processing unit 41 of the article inspection device 1 of the first embodiment. including.

The second image generation unit 45 has come to generate an image of the appearance of the object W to be inspected, which is composed of pixels having pixel values corresponding to the light intensity detected for each light receiving element by the second light intensity detection unit 20. There is.

In the present embodiment, the determination unit 44 determines the quality of the inspected object W based on the comparison between the image generated by the second image generation unit 45 and the image of the non-defective sample of the inspected object W generated in advance. It is designed to judge. For example, when the absolute value of the difference between each pixel value of the image generated by the second image generation unit 45 and each pixel value of the image of the non-defective sample of the inspected object W exceeds a predetermined value, the inspected object is inspected. It is determined that there is an abnormality in W.

Further, the determination unit 44 is based on the distribution of the birefringence phase difference δ calculated by the birefringence phase difference distribution calculation unit 43 and the image generated by the first image generation unit 42, as in the first embodiment. Therefore, the quality of the object W to be inspected is judged.

In the present embodiment, the display unit 50 is generated by the second image generation unit 45 in addition to the judgment result of the quality of the object W to be inspected by the determination unit 44 and the image generated by the first image generation unit 42. Images are also displayed.

As described above, the article inspection device 2 according to the present embodiment is a second image sensor 19 that receives a light beam from the imaging optical system 13 without passing through the second 1/4 wave plate 14 and the analyzer 15. In addition to the inspection of the birefringence of the object W to be inspected based on the intensity signal from the first image sensor 16, the inspection of the appearance of the object W to be inspected based on the intensity signal from the second image sensor 19 It can be performed.

1, 2 Article inspection device 10 Light irradiation unit 10a LD
10b collimating lens 10c SLD
10d LED
10e Polarizer 11 1st 1/4 wave plate 12 Irradiation optical system 13 Imaging optical system 14 2nd 1/4 wave plate 15 Detector 16 1st image sensor 17 1st light intensity detector 18 Optical branching device 19 2nd image sensor 20 2nd light intensity detection unit 30 Transport unit 41, 41'Processing unit 42 1st image generation unit 43 Birefringence phase difference distribution calculation unit 44 Judgment unit 45 2nd image generation unit W Inspected object

Claims (4)

A transport unit (30) that transports the object to be inspected to the inspection area,
A light irradiation unit (10) that outputs a linearly polarized luminous flux, and
A first 1/4 wave plate (11) that imparts a phase difference of 1/4 wavelength to the linearly polarized light flux and converts it into a circularly polarized light flux.
An irradiation optical system (12) that irradiates the object to be inspected transported to the inspection area with the circularly polarized light flux.
A second 1/4 wave plate (14) that imparts a phase difference of 1/4 wavelength to the luminous flux transmitted through the object to be inspected.
An detector (15) that passes a predetermined polarization component of a luminous flux that has passed through the second quarter wave plate, and a detector (15).
A first image sensor (16) including a plurality of light receiving elements that output an intensity signal according to the amount of light flux passing through the analyzer, and a first image sensor (16).
A light beam that is arranged between the object to be inspected and the second 1/4 wave plate conveyed to the inspection area and transmitted through the object to be inspected is transmitted to the second 1/4 wave plate and the analyzer. An imaging optical system (13) that forms an image on the first image sensor via
A birefringence phase difference distribution calculation unit (43) that calculates the distribution of the birefringence phase difference of the object to be inspected from the intensity signals output from each of the light receiving elements of the first image sensor.
A determination unit that determines the quality of the object to be inspected based on a comparison between the distribution of the birefringence phase difference calculated by the birefringence phase difference distribution calculation unit and a predetermined distribution of the desired birefringence phase difference. (44), an article inspection device comprising. An optical turnout (18) arranged between the imaging optical system and the second quarter wave plate and for branching a light flux from the imaging optical system,
A second image sensor (19) including a plurality of light receiving elements that output an intensity signal according to the amount of light of the input luminous flux, and
An image generation unit (45) that generates an image of the appearance of the object to be inspected from the intensity signal output from each light receiving element of the second image sensor is further provided.
The imaging optical system forms an image of one of the light fluxes branched by the optical branching device on the first image sensor via the second 1/4 wave plate and the analyzer, and the optical branching device. The other luminous flux branched in is imaged on the second image sensor.
The determination unit is characterized in that it determines the quality of the inspected object based on the comparison between the image generated by the image generation unit and the image of the non-defective sample of the inspected object generated in advance. The article inspection device according to claim 1. The article inspection apparatus according to claim 1 or 2, wherein the light irradiation unit includes a laser diode (10a) that outputs a linearly polarized light beam. The step (S1) of transporting the object to be inspected to the inspection area and
The step (S2) of outputting a linearly polarized luminous flux and
A step (S3) of imparting a phase difference of 1/4 wavelength to the linearly polarized light flux by the first 1/4 wave plate (11) and converting the linearly polarized light flux into a circularly polarized light flux.
In the step (S4) of irradiating the object to be inspected transported to the inspection area with the circularly polarized light flux,
The step (S5) of imparting a phase difference of 1/4 wavelength to the luminous flux transmitted through the object to be inspected by the second 1/4 wave plate (14).
A step (S6) of passing a predetermined polarization component of the luminous flux that has passed through the second 1/4 wave plate by the analyzer (15).
The luminous flux transmitted through the object to be inspected is transmitted by the imaging optical system (13) arranged between the object to be inspected and the second quarter wave plate conveyed to the inspection area. In the step (S7) of forming an image on the first image sensor (16) via the 1/4 wave plate and the analyzer,
A step (S8) of outputting an intensity signal according to the amount of light flux passing through the analyzer from the first image sensor including a plurality of light receiving elements.
A birefringence phase difference distribution calculation step (S9) for calculating the distribution of the birefringence phase difference of the object to be inspected from the intensity signals output from each of the light receiving elements of the first image sensor.
A step of determining the quality of the object to be inspected based on a comparison between the distribution of the birefringence phase difference calculated by the step of calculating the birefringence phase difference distribution and a predetermined distribution of the desired birefringence phase difference ( An article inspection method comprising S10) and.

Images