JPH095209A - Apparatus and method for inspecting hologram - Google Patents

Abstract

PURPOSE: To provide low-cost apparatus and method for inspecting a hologram capable of numerically accurately determining the shape and structure of a diffraction grating pattern included in the hologram to be inspected by electric means, improving the inspecting quality, conducting a quality control, and simply inspecting a manufacturing line or after delivery. CONSTITUTION: The method for inspecting a hologram comprises the steps of projecting light having a wavelength component capable of inspecting a diffraction grating pattern included in the hologram 7 from a light source 2, detecting the diffracted light reflected from the hologram 7 by an optical sensor 4, measuring its diffraction angle and intensity, and numerically determining the grating pitch, direction and efficiency of the grating pattern from the values by calculating means 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram inspection apparatus and method used for inspecting holograms at the time of photographing or manufacturing, and for inspecting after shipment and verifying holograms.

[0002]

2. Description of the Related Art Hitherto, visual inspection of an image reproduced by a reproducing light source has been performed in inspections during photographing of holograms and in manufacturing processes. Alternatively, an optical inspection method has been performed in which a reproduced image is captured as a two-dimensional image using an image pickup device such as a CCD camera and image analysis is used. 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. Also,
As a special case, for holograms and the like created on the premise that they are read by an optical sensor such as holograms for machine reading, a method of performing inspection using the reader is known. Known techniques related to these are, for example, JP-A-3-211096 and JP-A-6-76365.

[0003]

In visual inspection during hologram recording or in the duplication process, variations in the quality of the finished product due to individual differences among inspectors become large, making it difficult to apply a numerical control method. Therefore, even if measures are taken, the inspection standard is not clarified, and it is difficult to effectively improve the overall quality. In addition, when conducting a quality follow-up survey after shipping, there is no standard for comparing with the state at the time of shipping, so only the memory of the inspector is relied on, and it is very difficult to carry out a sufficient analytical survey. Is. In addition, as for the authenticity determination of holograms used for security, as with post-shipment inspection, there are no clear criteria for determination, and most of the users are amateurs.
There is a possibility that the authenticity judgment may be erroneous even for a bad counterfeit product. In addition, in the case of a hologram for machine reading, the price of the reader becomes expensive.

The present invention solves the above-mentioned problems, and instead of the conventional inspection method for a reproduced image of a visual or optical hologram, a fine diffraction grating that constitutes a hologram by electrical means is used. Provide a hologram inspection apparatus and method that can quantitatively and accurately obtain the shape and structure of the above, improve the inspection quality and the quality of the hologram product based on the inspection, and have a simple and small structure and can be implemented at low cost. The purpose is to

[0005]

In order to achieve the above object, the present invention provides a light source section that emits a light beam containing a predetermined wavelength component, an optical sensor having sensitivity to the wavelength component, and an inspection target. A hologram inspection apparatus comprising: a holder for arranging the light source unit and an optical sensor for the hologram of 1 .; and an operation unit for operating an inspection characteristic value of a diffraction grating pattern forming the hologram based on the output of the optical sensor. The light source unit is arranged so that its light beam irradiates a desired region of the hologram, and the optical sensor is arranged to receive diffracted light diffracted by a diffraction grating pattern included in the desired region of the hologram. Based on the output of the optical sensor, the calculating means determines the diffraction angle and intensity of the diffracted light to determine the grating pitch, the grating direction and the diffraction efficiency of the diffraction grating pattern. Even without those constituting the hologram inspection apparatus for calculating an inspection characteristic value representing any one. More specifically, the light source unit comprises a light source emitting a bright line spectrum such as a laser, a light emitting diode, a mercury lamp, or a combination of a light source having the bright line spectrum or a white light source having a continuous spectrum and an optical element having wavelength selectivity. Is characterized by. Further, on the light source section side, an adjusting optical system for adjusting the wavefront of the light beam emitted from the light source in accordance with the conditions at the time of manufacturing the hologram to be inspected is attached, and the optical system includes a lens and a mirror. Alternatively, it is characterized by comprising a diffraction grating. Further, the optical sensor is characterized in that it has sensitivity in a wavelength range with respect to the spectral characteristic of the light source section and has a resolution necessary for detecting diffracted light. It is characterized in that the holding part is formed so that the light source part and the optical sensor can be moved to desired rotational positions and coordinate positions. Further, a light beam containing a predetermined wavelength component is irradiated from a light source unit directly or through an adjusting optical system, and its incident direction is adjusted to irradiate the hologram to be inspected, and diffracted light from the hologram is applied to the wavelength component. An inspection which is made incident on an optical sensor having sensitivity and resolution necessary for detecting diffracted light, and an inspection characteristic value of a diffraction grating pattern forming the hologram is calculated based on an output of the optical sensor to perform quality inspection of the hologram. A method, wherein the inspection characteristic value represents 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 intensity of the diffracted light detected by the optical sensor. It is characterized by an inspection method.

[0006]

In this device, by maintaining the relative positional relationship between the light source and the hologram, the diffraction pattern of the diffraction grating pattern is extracted from the emission angle of the diffracted light that is included in the area irradiated with the light rays and reflected from the diffraction grating pattern. It becomes possible to specify the pitch. That is, the diffracted light is made incident on an optical sensor whose position in the space relative to the inspection area of the hologram is known, whereby the grating pitch of the diffraction grating pattern and the grating direction in addition to this are calculated. 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. As described above, it is possible to perform digitized and highly accurate measurement. In an article composed of a collection of minute diffraction grating patterns such as a hologram, diffracted light by a plurality of diffraction grating patterns is emitted depending on the spot diameter of the light beam entering the hologram. Since the light distribution can be grasped as the received light intensity distribution on the photosensor surface, the grating pitch and the grating direction of the diffraction grating pattern included in the irradiation region can be calculated from the distribution. Further, since the hologram inspection apparatus is configured so that the light source unit and the optical sensor can move relative to the hologram, it is possible to arbitrarily perform measurement at a plurality of points on the hologram surface.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention, FIG. 2 is a schematic diagram illustrating an outline of an inspection method of the present embodiment, and FIG. 3 is an explanatory method for obtaining a fine structure of a diffraction grating pattern. It is a drawing.

As shown in FIG. 1, the hologram inspection apparatus 1 of this embodiment includes a light source unit 2, an adjusting optical system 3 attached to the light source unit 2, an optical sensor 4, an arithmetic unit 5, and a light source. Part 2
And a holding unit 6 for rotatably and movably supporting the optical sensor 4 and the hologram 7 to be inspected.

The light source unit 2 is configured to emit a light beam containing a wavelength component necessary for inspecting the hologram 7. For example, a solid-state laser represented by a semiconductor laser, a gas laser such as He-Ne laser, a light-emitting diode, a mercury lamp. A single light source having a bright line spectrum such as, 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 wavelength selectivity (for example, a dichroic mirror or a dichroic filter). Further, the light source unit 2 is a measurement location (desired area) of the hologram 7 to be inspected.
Is rotatably or movably supported by the holding portion 6 in order to irradiate a light beam having an entrance angle of θ ₀ (a support structure is omitted). On the other hand, the adjustment optical system 3 adjusts, for example, the light beam applied to the hologram 7 to the conjugate condition with the reference light used when the hologram 7 is manufactured, and adjusts the wavefront of the light to improve 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.

The optical sensor 4 is composed of a sensor having sensitivity to the wavelength component, and as shown in FIG. 1, a line sensor 8 and a CCD 9 in which a plurality of light receiving elements 8a, 8b, 8c, 8d etc. are temporarily arranged. An area sensor 11 and the like in which innumerable light receiving elements made up of two or more elements are two-dimensionally arranged on a plane. The optical sensor 4 is movably supported by the holding portion 6 so that the diffracted light from the hologram 7 can be received. 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 apparatus.

The computing means 5 is composed of a microcomputer or the like and is connected to the optical sensor 4, and based on the signal output according to the detection result of the diffracted light by the optical sensor 4, the inspection characteristic value of the diffraction grating pattern included in the hologram 7 is obtained. It is something to calculate. The inspection characteristic values include the grating pitch of the diffraction grating pattern, the grating direction, the diffraction efficiency and the fine structure of the diffraction grating.

The holding section 6 supports the light source section 2 and the optical sensor 4 so as to be rotatable or movable, as described above.
Further, as shown in FIG. 1, the hologram 7 is also supported so as to be movable along the arrow direction.

Next, a method of inspecting the hologram 7 according to this embodiment will be described. Generally, the following equation is established between the grating pitch p of the diffraction grating pattern and the outgoing angle of the diffracted light, that is, the diffraction angle θ. p = λ / (sin θ ₀ + sin θ) (1) In the formula (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 outgoing angle θ of the diffracted light with the optical sensor 4.

As shown in the schematic diagram of FIG. 2, a light beam having a light intensity distribution of a glass distribution of an incident angle θ ₀ and a wavelength λ from a light source unit 2 is applied to a diffraction grating pattern included in a predetermined region 12 of the hologram 7. Then, diffracted light having a glass distribution is emitted from the diffraction grating pattern. The diffracted light is received by the line sensor 8 or the area sensor 11. In the optical configuration in which the incident light and the diffracted light are arranged on the same plane, the diffracted light can be received by using, for example, the line sensor 8. The detection output is, as shown in the graph, one-dimensional direction (X
Direction) along with the received light intensity distribution. The diffraction angle θ is obtained by reading the peak position of this intensity distribution, and the equation (1) is calculated by using this and the values of the known incident angle θ ₀ and wavelength λ, and the grating of the diffraction grating pattern included in the irradiation region is obtained. 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, the diffracted light has two-dimensional directions (x and y).
Direction), diffracted light is received using the area sensor 11 to obtain a two-dimensional received light 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, the hologram 7 is appropriately moved to inspect the diffraction grating pattern in a place other than the region 12 by the same method as described above.

As shown in FIG. 3A, when the diffraction grating pattern of the hologram 7 is magnified, it 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 temporarily called a carrier wave diffraction grating 13. On the other hand, in the diffraction grating pattern formed on the hologram 7, in addition to the carrier diffraction grating 13 described above, a plurality of fine diffraction gratings to be superimposed thereon are complicatedly included. This fine diffraction grating is likened to a modulated wave on a carrier 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 modulated wave diffraction grating 14 is obtained as shown in FIG. 3B. . By analyzing this peak, the fine structure of the diffraction grating pattern can be understood.

[0016]

INDUSTRIAL APPLICABILITY The present invention can quantify all or a part of the grating pitch, the grating direction, and the diffraction efficiency in a minute diffraction grating unit which constitutes a hologram, and therefore can be digitized. It is possible to perform very accurate hologram inspection. By recording this numerical information, it becomes possible to adapt the numerical management method,
It is possible to effectively improve the overall quality. Even in the inspection after shipping, since the reference numerical data remains, sufficient inspection can be performed. In addition, since the device is integrated, anyone can perform accurate measurements, and it is possible to suppress variations in measurement by the operator, and because the structure can be simplified, it is easy to downsize and there are advantages that failures can be reduced. Have. Further, since it is possible to use parts having various specifications for the light source and the optical sensor, not only inexpensive parts can be used, but also the parts constituting the inspection device can be easily standardized, so that the cost can be easily reduced.

[Brief description of 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 of the present embodiment.

FIG. 3 is a schematic diagram for explaining an inspection method for obtaining a fine structure of a diffraction grating.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hologram inspection device 2 Light source part 3 Adjustment optical system 4 Optical sensor 5 Computing means 6 Holding part 7 Hologram 8 Line sensor 9 CCD 11 Area sensor 12 Area 13 Carrier wave diffraction grating 14 Modulated wave diffraction grating

Claims (6)

[Claims] 1. A light source unit that emits a light beam including a predetermined wavelength component, and an optical sensor that is sensitive to the wavelength component.
A hologram inspecting apparatus comprising: a holding unit for arranging the light source unit and an optical sensor for a hologram to be inspected; and an operation unit for calculating an inspection characteristic value of a diffraction grating pattern forming the hologram based on an output of the optical sensor. Then, the light source unit is arranged so that the light beam irradiates a desired region of the hologram, and the optical sensor receives the diffracted light diffracted by the diffraction grating pattern included in the desired region of the hologram. And calculating the inspection characteristic value representing at least one of the grating pitch, the grating direction and the 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. A hologram inspection apparatus characterized by the following. 2. The light source unit is a light source that emits a bright line spectrum such as a laser, a light emitting diode, or a mercury lamp, or a light source that is a combination of a light source having the bright line spectrum or a white light source having a continuous spectrum and an optical element having wavelength selectivity. The hologram inspection apparatus according to claim 1, wherein 3. An adjusting optical system for adjusting the wavefront of a light beam emitted from the light source in accordance with the conditions at the time of manufacturing the hologram to be inspected is attached to the light source section side, and the optical system comprises: The hologram inspection apparatus according to claim 1, comprising a lens, a mirror, or a diffraction grating. 4. The hologram inspection apparatus according to claim 1, wherein the optical sensor has sensitivity in a wavelength range with respect to the spectral characteristic of the light source unit and has a resolution necessary for detecting diffracted light. 5. The hologram inspection apparatus according to claim 1, wherein the holding section is formed so as to move the light source section and the optical sensor to desired rotational positions and coordinate positions. 6. A hologram to be inspected is irradiated with a light beam containing a predetermined wavelength component from a light source section directly or through an adjusting optical system and with its incident direction adjusted, and diffracted light from the hologram is irradiated with the wavelength. It is made incident on an optical sensor having sensitivity to the component and having a resolution necessary for detecting diffracted light, and the inspection characteristic value of the diffraction grating pattern forming the hologram is calculated based on the output of the optical sensor to inspect the quality of the hologram. At least one of a grating pitch, a grating direction and a diffraction efficiency of a diffraction grating pattern in which the inspection characteristic value is calculated from the diffraction angle and intensity of the diffracted light detected by the optical sensor. And a hologram inspection method characterized by: