JP3556324B2 - Hologram inspection apparatus and method - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a hologram inspection apparatus and method used for inspection at the time of photographing or manufacturing a hologram, inspection after shipment, and verification of a hologram.
[0002]
[Prior art]
Heretofore, during inspection of the hologram and during the manufacturing process, an image reproduced by a light source for reproduction has been visually inspected. Alternatively, a reproduced image is captured as a two-dimensional image using an imaging device such as a CCD camera, and an optical inspection method using image analysis has been performed. A method of inspecting a stereoscopic image as a plurality of two-dimensional images by further changing the observation position by this method is also known. As a special case, a method of inspecting a hologram or the like made on the premise of being read by an optical sensor such as a machine-readable hologram using a reader is known. Known techniques relating to this are, for example, Japanese Patent Application Laid-Open Nos. Hei 3-211096 and Hei 6-76365.
[0003]
[Problems to be solved by the invention]
In visual inspection at the time of hologram photographing or in the duplication process, the variation in the quality of finished products due to individual differences among inspectors is large, and it is difficult to apply a numerical management method. For this reason, even though measures are taken, the inspection standards are not clear, making it difficult to effectively increase the overall quality. In addition, when conducting a follow-up survey of quality after shipping, there is no standard for comparison with the state at the time of shipping, so only the memory of the inspector is relied on, and it is extremely difficult to conduct a sufficient analytical survey. It is. In addition, as with post-shipment inspections, the authenticity of holograms used for security is not limited to clear judgment criteria, and most of the users are amateurs. There is a possibility that false judgments will be made. In addition, even in the case of a machine-readable hologram, there is a problem that the price of the reader becomes expensive.
[0004]
The present invention solves the above problems, and replaces the conventional inspection method for visually or optically reproduced images of a hologram with a fine diffraction grating that forms a hologram by an electric means instead of an inspection method. It is an object of the present invention to provide a hologram inspection apparatus and method which can quantitatively determine the structure with high precision, improve the inspection quality and the quality of a hologram product based on the inspection, and have a simple, compact structure and can be implemented at low cost. And
[0005]
[Means for Solving the Problems]
The present invention provides a light source unit that emits a light beam containing a predetermined white wavelength component, an optical sensor having sensitivity to the wavelength component, and the light source unit for a hologram to be inspected. A hologram inspection apparatus comprising: a holding unit for arranging an optical sensor; and arithmetic means for calculating an inspection characteristic value of a diffraction grating pattern forming the hologram based on an output of the optical sensor. There is arranged to illuminate a desired two-dimensional region of the hologram, the light sensor is positioned to receive light diffracted by the diffraction grating pattern included in the desired two-dimensional region of the hologram, The calculating means determines at least the grating pitch, grating direction and diffraction efficiency of the diffraction grating pattern from the diffraction angle and intensity of the diffracted light based on the output of the optical sensor. It constitutes a hologram inspection apparatus characterized by computing a test characteristic values representing any one. More specifically, the light source unit may be a light source that emits an emission line spectrum such as a laser, a light emitting diode, a mercury lamp, or a combination of a light source having the emission line spectrum or a white light source having a continuous spectrum and an optical element having wavelength selectivity. It is characterized by becoming. Further, an adjustment optical system for adjusting a wavefront of a light beam emitted from the light source according to conditions at the time of manufacturing the hologram to be inspected is provided on the light source unit side, and the optical system includes a lens and a mirror. Alternatively, it is characterized by comprising a diffraction grating. The optical sensor is characterized in that it has sensitivity in a wavelength range with respect to the spectral characteristics of the light source unit and has a resolution required for detecting diffracted light. The holding unit is formed so that the light source unit and the optical sensor can be moved to desired rotation positions and coordinate positions. Further, a light beam containing a predetermined white wavelength component is irradiated from the light source unit directly or through an adjustment optical system, and the incident direction is adjusted to irradiate the two-dimensional area of the hologram to be inspected, and the diffracted light from the hologram is irradiated. The light is incident on an optical sensor having sensitivity to the wavelength component and having a resolution necessary for detecting the diffracted light, and an inspection characteristic value of a diffraction grating pattern constituting the hologram is calculated based on an output of the optical sensor to calculate the inspection characteristic value of the hologram. An inspection method for performing quality inspection, wherein the inspection characteristic value is at least one of a grating pitch, a grating direction, and a diffraction efficiency of a diffraction grating pattern calculated from a diffraction angle and an intensity of the diffracted light detected by the optical sensor. It is characterized by representing one.
[0006]
[Action]
In this device, by maintaining the relative positional relationship between the light source and the hologram, the grating pitch of the diffraction grating pattern is specified from the exit angle of the diffracted light included in the area irradiated with the light beam and reflected from the diffraction grating pattern. It is possible to do. That is, by making the diffracted light incident on an optical sensor whose position in the space relative to the inspection region of the hologram is known, the grating pitch of the diffraction grating pattern and the grating direction are calculated by calculation. You can ask. Further, the intensity of the diffracted light, that is, the diffraction efficiency, can be known from the intensity of the electric signal output from the optical sensor and the like. As described above, it is possible to perform a very accurate measurement which is quantified. In an article composed of an aggregate of minute diffraction grating patterns represented by a hologram, diffracted light by a plurality of diffraction grating patterns is emitted depending on the spot diameter of a light beam incident on the hologram. Since the light distribution can be regarded as a light receiving intensity distribution on the optical sensor surface, the grating pitch and the grating direction of the diffraction grating pattern included in the irradiation area can be calculated from the distribution. In addition, the hologram inspection device is configured so that the light source unit and the optical sensor can relatively move with respect to the hologram, so that measurement at a plurality of points on the hologram surface can be arbitrarily performed.
[0007]
【Example】
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram illustrating an embodiment of the present invention, FIG. 2 is a schematic diagram illustrating an outline of an inspection method according to the embodiment, and FIG. 3 is a diagram illustrating an analysis method for obtaining a fine structure of a diffraction grating pattern. It is a drawing.
[0008]
As shown in FIG. 1, the hologram inspection apparatus 1 according to the present embodiment includes a light source unit 2, an adjustment optical system 3 attached to the light source unit 2, an optical sensor 4, an arithmetic unit 5, and a light source unit 2. It comprises an optical sensor 4 and a holder 6 for supporting a hologram 7 to be inspected in a rotatable and movable manner.
[0009]
The light source unit 2 emits a light beam containing a white wavelength component necessary for inspection of the hologram 7. For example, a solid-state laser represented by a semiconductor laser, a gas laser such as a He-Ne laser, a light-emitting diode, a mercury lamp, and the like. It is composed of a single light source having a bright line spectrum, or a combination of a light source having the bright line spectrum, a white light source such as an incandescent lamp, and an optical element having a wavelength selectivity (for example, a dichroic mirror or a dichroic filter). In addition, the light source unit 2 is supported by the holding unit 6 so as to rotate or move in position so as to irradiate a measurement point (desired area) of the hologram 7 to be inspected with a light beam having an incident angle θ ₀ (support structure is omitted). . On the other hand, the adjusting optical system 3 adjusts, for example, a light beam irradiated on the hologram 7 to a conjugate condition with the reference light used at the time of manufacturing the hologram 7, adjusts the wavefront of the light, and improves the measurement accuracy of the hologram 7. belongs to. For example, an optical element such as a convex lens, a concave lens, a mirror or a diffraction grating is used.
[0010]
The optical sensor 4 is a sensor having sensitivity to the wavelength component, and includes a line sensor 8 and a CCD 9 in which a plurality of light receiving elements 8a, 8b, 8c, 8d and the like are arranged in a line as shown in FIG. It comprises an area sensor 11 and the like in which countless light receiving elements are two-dimensionally arranged on a plane. The optical sensor 4 is supported by the holder 6 so that the mounting position is movable so that the optical sensor 4 can receive the diffracted light from the hologram 7. Actually, the line sensor 8 and the area sensor 11 may be appropriately selected according to the inspection content and the like and incorporated into the inspection device.
[0011]
The calculating means 5 is composed of a microcomputer or the like, is connected to the optical sensor 4, and calculates an inspection characteristic value of a diffraction grating pattern included in the hologram 7 based on a signal output according to a detection result of the diffracted light by the optical sensor 4. It is. The inspection characteristic values include the grating pitch of the diffraction grating pattern, the grating direction, the diffraction efficiency, the fine structure of the diffraction grating, and the like.
[0012]
The holding section 6 supports the light source section 2 and the optical sensor 4 so as to be able to rotate or move as described above. Further, as shown in FIG. 1, the hologram 7 is also supported so as to be movable along the arrow direction.
[0013]
Next, a method of inspecting the hologram 7 according to the present embodiment will be described. In general, the following equation holds between the grating pitch p of the diffraction grating pattern and the output angle of the diffracted light, that is, the diffraction angle θ.
p = λ / (sin θ ₀ + sin θ) (1)
In the equation (1), λ is the wavelength of the light beam emitted from the light source unit 2, and θ ₀ is the incident angle of the light beam. Therefore, the grating pitch p can be theoretically obtained by detecting the output angle θ of the diffracted light by the optical sensor 4.
[0014]
As shown in the schematic diagram of FIG. 2, when a light beam having a light intensity distribution of a glass distribution having a wavelength λ at an incident angle θ ₀ from a light source unit 2 irradiates a diffraction grating pattern included in a predetermined two-dimensional region 12 of a hologram 7. Diffracted light having a glass distribution is emitted from the diffraction grating pattern. This diffracted light is received by the line sensor 8 or the area sensor 11. In an optical configuration in which the incident light and the diffracted light are arranged on the same plane, the diffracted light can be received using, for example, the line sensor 8. As shown in the graph, the detected output is a received light intensity distribution along the one-dimensional direction (X direction) of the line sensor 8. The diffraction angle θ is determined by reading the peak position of this intensity distribution, and the above equation (1) is calculated using this and the known values of the incident angle θ ₀ and the wavelength λ. Pitch is required. Further, the diffraction efficiency of the diffraction grating pattern is obtained based on the peak level of the received light intensity distribution. On the other hand, when the diffracted light is distributed in the two-dimensional directions (x and y directions), the area sensor 11 receives the diffracted light to obtain a two-dimensional light receiving intensity distribution. In this case, the grating direction can be detected in addition to the grating pitch and the diffraction efficiency. That is, the lattice direction (lattice orientation) and the two-dimensional position of the peak are correlated with each other. Next, by appropriately moving the hologram 7, the inspection of the diffraction grating pattern in a place other than the two-dimensional area 12 is performed by the same method as described above.
[0015]
As shown in FIG. 3A, when the diffraction grating pattern of the hologram 7 is viewed in an enlarged manner, the hologram 7 is formed of convex and concave portions having a pitch p. This basic diffraction grating shape is similar to the shape of a carrier wave when compared to a radio wave, and is tentatively called a carrier diffraction grating 13. On the other hand, the diffraction grating pattern formed on the hologram 7 includes a plurality of fine diffraction gratings overlapping with the carrier diffraction grating 13 in addition to the carrier diffraction grating 13 in a complicated manner. This fine diffraction grating is likened to a modulated wave on a carrier wave and is called a modulated wave diffraction grating 14. When the diffracted light reflected from these diffraction gratings is detected by the optical sensor 4, a received light intensity distribution having several peaks corresponding to the carrier diffraction grating 13 and the modulation wave diffraction grating 14 is obtained as shown in FIG. . By analyzing this peak, the fine structure of the diffraction grating pattern can be grasped.
[0016]
【The invention's effect】
The present invention enables simultaneous measurement of all or a part of the grating pitch, grating direction, and diffraction efficiency in a minute diffraction grating unit constituting a hologram, so that a highly accurate numerical value is obtained. Good hologram inspection can be performed. By recording this numerical information, it becomes possible to apply a numerical management method, and it is possible to effectively improve the overall quality. In the inspection after shipment, sufficient numerical inspection can be performed because the reference numerical data remains. Also, by integrating the device, anyone can perform accurate measurement, so that the variation of the measurement by the measurer can be suppressed, and the structure can be simplified, so that the size can be easily reduced and the number of failures can be reduced. Have. Furthermore, since parts having various specifications can be used for the light source and the optical sensor, not only can inexpensive parts be used, but also the parts constituting the inspection apparatus can be easily standardized, so that the cost can be reduced easily.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an embodiment of the present invention.
FIG. 2 is a schematic diagram for explaining the outline of the inspection method according to the embodiment.
FIG. 3 is a schematic diagram for explaining an inspection method for obtaining a fine structure of a diffraction grating.
[Explanation of symbols]
Reference Signs List 1 hologram inspection device 2 light source unit 3 adjustment optical system 4 optical sensor 5 calculation unit 6 holding unit 7 hologram 8 line sensor 9 CCD
Reference Signs List 11 Area sensor 12 Two-dimensional area 13 Carrier diffraction grating 14 Modulated wave diffraction grating

Claims (6)

A light source unit that emits a light beam containing a predetermined white wavelength component, an optical sensor having sensitivity to the wavelength component, a holding unit that arranges the light source unit and the optical sensor with respect to a hologram to be inspected, Operating means for calculating an inspection characteristic value of the diffraction grating pattern constituting the hologram based on the output, wherein the light source unit irradiates a desired two-dimensional area of the hologram with the light beam. And the optical sensor is arranged to receive the diffracted light diffracted by a diffraction grating pattern included in a desired two-dimensional area of the hologram, and the arithmetic means is configured to output the diffracted light based on an output of the optical sensor. Calculates inspection characteristic values representing at least one of the grating pitch, grating direction, and diffraction efficiency of the diffraction grating pattern from the diffraction angle and intensity of Hologram inspection apparatus according to claim Rukoto. 2. The light source unit according to claim 1, wherein the light source unit is a light source that emits an emission line spectrum such as a laser, a light emitting diode, or a mercury lamp, or a combination of a light source having the emission line spectrum or a white light source having a continuous spectrum and an optical element having wavelength selectivity. Hologram inspection device. An adjusting optical system for adjusting the wavefront of a light beam emitted from the light source to the condition at the time of manufacturing the hologram to be inspected is provided on the light source unit side, and the optical system includes a lens, a mirror, or a diffraction optical system. 2. The hologram inspection device according to claim 1, wherein the hologram inspection device comprises a grating. The hologram inspection apparatus according to claim 1, wherein the optical sensor has sensitivity in a wavelength range with respect to a spectral characteristic of the light source unit and has a resolution necessary for detecting diffracted light. 2. The hologram inspection apparatus according to claim 1, wherein the holding unit is formed so as to move the light source unit and the optical sensor to desired rotation positions and coordinate positions. A light beam containing a predetermined white wavelength component is emitted from the light source unit directly or through an adjustment optical system, and the incident direction is adjusted to irradiate a two-dimensional area of the hologram to be inspected, and the diffracted light from the hologram is converted to the wavelength. The light is incident on an optical sensor having sensitivity to the component and having a resolution necessary for detecting the diffracted light, and an inspection characteristic value of a diffraction grating pattern constituting the hologram is calculated based on an output of the optical sensor to inspect the quality of the hologram. Wherein the inspection characteristic value is calculated from a diffraction angle and an intensity of the diffracted light detected by the optical sensor, at least one of a grating pitch, a grating direction, and a diffraction efficiency of a diffraction grating pattern. A hologram inspection method characterized by representing:

Images