JP2011107512A - Argument image pickup device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an argument image pickup device which can be miniaturized and can acquire many argument images of an optical variable element as easily as possible. <P>SOLUTION: The argument image pickup device 1 includes: a plurality of white light sources 11 radiating white light to the optical variable element 20a; an objective lens 13 arranged at a position separate from the optical variable element 20a by length nearly equal to focal length, and changing light from the optical variable element 20a to parallel beams; an optical lens array 14 constituted by arranging a plurality of optical lenses for condensing the light from the objective lens 13 on the same plane; and a solid-state imaging element 15 imaging ommatidium images respectively formed by the optical lenses. When a direction around the axial of an axis AX, nearly parallel with the parallel beams and passing through an almost focal position of the objective lens 13, is defined as a rotating direction, the plurality of white light sources 11 are respectively arranged in the rotating direction at a plurality of positions where an incident angle of the white light on the optical variable element 20a is different. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an apparatus that captures a declination image of an optical change element whose appearance changes depending on an illumination direction or an observation direction. In the present specification, the declination image refers to an image obtained by changing measurement geometric conditions such as an illumination direction and an observation direction.

  Conventionally, for paper sheets such as banknotes and securities, and cards such as credit cards and prepaid cards, an optical variable element (OVD: Optically Variable Device) whose appearance changes depending on an illumination direction or an observation direction to prevent forgery. ) Is often attached. For example, a credit card may be provided with a hologram sticker, and an image based on a specific diffraction pattern is formed on the sticker (see, for example, Patent Document 1). In addition to the hologram described above, the optically variable element includes, for example, an optically variable ink (OVI) typified by pearl ink or the like.

  When authenticity determination is performed using an optical change element such as a hologram, visual determination or determination using a spectrophotometer is conventionally performed. However, it is difficult to determine the illumination direction and the observation direction strictly by visual discrimination. For example, it is difficult to read a minute change in a diffraction grating period (diffraction grating interval) in a hologram. Also, in the discrimination using a spectrophotometer, it is possible to determine the illumination direction etc. and perform an accurate measurement. However, if a large amount of information is acquired in order to accurately determine the authenticity, the apparatus becomes large. Inconveniences such as being easy to convert, and inconveniences that measurement is likely to be complicated.

  In this regard, if an imaging apparatus having a compound-eye optical system proposed in Non-Patent Document 1 is used, it is possible to perform accurate measurement by determining the illumination direction and the like, and a plurality of optical change elements in a single image. Since a declination image can be obtained, it is possible to perform true / false discrimination efficiently. However, the imaging apparatus having a compound eye optical system proposed in Non-Patent Document 1 has a problem that if an image having a high resolution is obtained in a wide observation range, the imaging unit becomes very large. The imaging unit referred to here is an optical lens array in which a plurality of minute optical lenses are arranged vertically and horizontally, and a solid-state imaging device that captures a single-eye image of a subject formed by each optical lens of the optical lens array, , Is a part configured by using.

JP 2006-284364 A

2005 (Spring 2005) Abstracts of the 52nd Joint Conference on Applied Physics, p. 1149 (2005.3.30, Saitama)

  In view of the above points, an object of the present invention is to provide a declination image pickup apparatus that can be miniaturized and that can easily acquire as many declination images of an optical change element as possible.

  In order to achieve the above object, a declination image capturing apparatus according to the present invention is a declination image capturing apparatus that captures a declination image of an optical change element, and a white light source that irradiates the optical change element with white light. And an objective lens that is arranged at a position that is approximately a focal length away from the optical change element and that collimates the light from the optical change element, and an optical lens that condenses the light from the objective lens A plurality of optical lens arrays arranged on the same plane; and a solid-state imaging device that picks up a single-eye image formed by each of the optical lenses, and is substantially parallel to the parallel light and substantially the same as the objective lens. When the direction around the axis passing through the focal point is set as the rotational direction, the white light can be applied to the optical change element at a plurality of incident angles, and the optical light is applied to each of the plurality of incident angles. Change element From a plurality of positions of the rotation direction with reference, it is characterized that it is possible to irradiate toward the white light to the optical variable device.

  In the declination image pickup apparatus of this configuration, the optical change element is irradiated with white light, the light from the optical change element is collimated, and the image pickup unit configured using the optical lens array and the solid-state image pickup element is used. By making it enter, a plurality of declination images can be acquired by one shooting. On the other hand, it is possible to irradiate the optical change element with white light at a plurality of incident angles, and optically change white light from a plurality of positions in the rotation direction with respect to the optical change element for each of the plurality of incident angles. Irradiation is possible toward the element. For this reason, it is possible to obtain many declination images efficiently by performing a simple operation of switching the irradiation direction of white light to the optical change element. In this configuration, since the irradiation direction of white light can be switched, a considerable amount of declination images can be acquired even if the number of compound-eye optical systems (the number of optical lenses included in the optical lens array) is reduced. Therefore, it is possible to reduce the size of the apparatus by reducing the imaging unit.

  In the declination image capturing apparatus having the above-described configuration, a plurality of the white light sources may be arranged in the rotation direction at each of a plurality of positions where the incident angles of the white light to the optical change element are different. Further, as another configuration, the white light source is one, and white that enables movement to change an incident angle of white light to the optical change element and movement to change a position in the rotation direction is possible. A light source moving mechanism may be further provided.

  According to the former, it is possible to acquire a large number of declination images of the optical change element by a simple operation of sequentially turning on a plurality of white light sources without using a drive source such as a motor. Further, according to the latter, it is possible to easily obtain a large number of declination images of the optical change element by reducing the number of white light sources. The latter case has an advantage that the position of the white light source can be set to an arbitrary position.

  The declination image pickup apparatus having the above configuration preferably further includes parallel light converting means for converting white light emitted from the white light source into parallel light and causing the parallel light to enter the optical change element. According to this configuration, it is possible to suppress a situation in which white light incident on the optical change element from the white light source diverges and light that deviates from the target incident angle enters the optical change element. That is, according to this configuration, it is easy to obtain more accurate information using the declination image captured by the declination image capturing apparatus. The parallel light conversion means can be, for example, a collimating lens or a concave mirror, but a collimating lens is preferable from the viewpoint that the apparatus can be easily downsized.

  In the declination image pickup apparatus having the above configuration, the optical lenses may be two-dimensionally arranged in two rows and two columns. As a result, it is possible to obtain a small-deflection image pickup device that can acquire as many declination images of the optically variable element as easily as possible.

  In the declination image pickup apparatus having the above-described configuration, it is preferable that the white light source is a light emitting diode. By using a light emitting diode, it is easy to reduce the size and power consumption of a white light source.

  According to the present invention, it is possible to provide a declination image capturing apparatus that can be miniaturized and that can easily acquire as many declination images of an optical change element as possible.

Schematic diagram showing the configuration of the declination image pickup apparatus of the first embodiment The schematic plan view for demonstrating the structure of the several white light source with which the declination imaging device of 1st Embodiment is provided. 1 is a schematic perspective view for explaining a configuration of an optical lens array and a solid-state imaging device included in a declination image capturing apparatus of the first embodiment. FIG. 6 is a schematic diagram for explaining the operation of the declination image pickup apparatus of the first embodiment, and is a diagram when white light is incident on the optical change element at an incident angle of 45 °. FIG. 6 is a schematic diagram for explaining the operation of the declination image pickup apparatus of the first embodiment, and is a diagram when white light is incident on the optical change element at an incident angle of 55 °. FIG. 6 is a schematic diagram for explaining the operation of the declination image pickup apparatus of the first embodiment, and is a diagram when white light is incident on the optical change element at an incident angle of 35 °. The figure for demonstrating the method of estimating the wavelength of diffracted light from a single eye image using rg chromaticity coordinate The schematic diagram for demonstrating the structure of the declination image pick-up device of 2nd Embodiment. Schematic which shows the structural example of the white light source moving mechanism with which the declination image pickup apparatus of 2nd Embodiment is provided.

  Hereinafter, an embodiment of a declination image capturing apparatus of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic diagram illustrating a configuration of a declination image capturing apparatus according to the first embodiment. FIG. 2 is a schematic plan view for explaining the configuration of a plurality of white light sources provided in the declination image capturing apparatus of the first embodiment. FIG. 3 is a schematic perspective view for explaining the configuration of the optical lens array and the solid-state imaging device included in the declination image capturing apparatus of the first embodiment. FIG. 3 is a view of the optical lens array and the solid-state imaging device as viewed from obliquely below in FIG. The configuration of the declination image capturing apparatus 1 of the first embodiment will be described with reference to FIGS. 1 to 3.

  As shown in FIG. 1, the declination image capturing apparatus 1 of the first embodiment includes a sample stage 10, a plurality of white light sources 11, a plurality of collimating lenses 12, an objective lens 13, an optical lens array 14, A solid-state imaging device 15.

  The sample table 10 is a table on which a sample 20 such as a credit card or securities having an optical change element 20a such as a hologram provided on the surface thereof is placed. The sample stage 10 may be a fixed type that does not move itself, or may be a movable type such as a conveyor belt.

  For each of the plurality of white light sources 11, for example, a white LED (Light Emitting Diode) is used. As the white light source in the declination image pickup apparatus 1, it is preferable to use an LED in consideration of the point that the space for arranging the light source can be reduced, the power consumption can be kept low, the directivity, and the like. It is not limited. For example, a halogen lamp, a xenon lamp, an ultrahigh pressure mercury lamp, a white laser light source, or the like may be used as the white light source.

  The plurality of white light sources 11 are arranged so as to irradiate the optical change element 20a with white light at a plurality of incident angles. Further, the plurality of white light sources 11 are arranged so that white light can be emitted toward the optical change element 20a from a plurality of positions in the rotation direction with respect to the optical change element 20a for each of the plurality of incident angles. Yes. Note that the rotation direction here refers to the direction around the axis AX that is substantially parallel to the parallel light emitted from the objective lens 13 and passes through the substantially focal position of the objective lens 13.

  Specifically, as shown in FIGS. 1 and 2, 45 ° in the rotation direction at each of the three positions where the incident angle of the white light to the optical change element 20a is 35 °, 45 °, and 55 °. White light sources are arranged at a pitch. That is, eight white light sources 111a to 111h are located at an incident angle of 35 °, eight white light sources 112a to 112h are located at an incident angle of 45 °, and eight white light sources 113a to 113h are located at an incident angle of 55 °. 113h is arranged.

  In the declination image pickup apparatus 1, the distances of the white light emitted from each of the 24 light sources arranged in total to the optical change element 20a are arranged so as to be almost equal. .

  As shown in FIGS. 1 and 2, the plurality of collimating lenses 12 are arranged one by one in the optical path between each of the plurality of white light sources 11 and the optical change element 20 a. That is, in the white light sources 111a to 111h arranged at the incident angle of 35 °, the collimating lens 121a corresponding to the white light source 111a, the collimating lens 121b corresponding to the white light source 111b, and so on. Collimating lenses 121a to 121h are arranged one by one corresponding to the light sources 111a to 111h. Similarly, for each of the white light sources 112a to 112h arranged at an incident angle of 45 °, one collimator lens 122a to 122h is arranged corresponding to each of the white light sources 112a to 112h, and arranged at a position of an incident angle of 55 °. Also for the white light sources 113a to 113h, one collimate lens 123a to 123h is arranged corresponding to each.

  The plurality of collimating lenses 12 in the declination image pickup apparatus 1 is an embodiment of parallel light converting means that converts white light emitted from the white light source in the present invention into parallel light and makes it incident on an optical change element. In this case, white light emitted from each of the plurality of white light sources 11 is incident on the optical change element 20a while being diverged. For this reason, the white light incident on the optical change element 20a contains a large amount of components incident from a target incident angle. In this regard, in the configuration in which the plurality of collimating lenses 12 are arranged as in the present embodiment, generation of components deviating from the above-described target incident angle can be suppressed as much as possible.

  The objective lens 13 is composed of a convex lens, and is disposed at a position separated from the optical change element 20a by a substantially focal length. For this reason, the reflected light that is reflected by the optical change element 20 a and incident on the objective lens 13 is emitted as parallel light from the objective lens 13.

  The optical lens array 14 includes four optical lenses 141, 142, 143, 144 that are two-dimensionally arranged in two rows and two columns, and a lens holder 145 that holds these optical lenses 141-144 (see FIG. 3). The optical lenses 141 to 144 held by the lens holder 145 may be fine lenses, and the focal length can be shortened and the thickness of the lens itself can be reduced. For this reason, it is possible to reduce the thickness of the imaging unit including the optical lens array 14 and the solid-state imaging device 15. Moreover, since the number of optical lenses provided in the optical lens array 14 is as small as four, the declination image pickup apparatus 1 can be reduced in size.

  As the solid-state imaging device 15, for example, a two-dimensional image sensor such as a charge coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS) image sensor is used. The solid-state imaging device 15 includes a substrate 151 and a sensor unit 152 that is arranged in a two-dimensional matrix on the substrate 151 and photoelectrically converts incident light. On the sensor unit 152, for example, a color filter in which three colors of RGB are Bayer arranged is arranged. By transmitting a signal output from the solid-state imaging device 15 to an image display device such as a liquid crystal display, images (single-eye images) formed by the optical lenses 141 to 144 can be displayed as images.

  In addition, since the optical lens array 14 is made small in order to reduce the size of the declination image pickup device 1, light from adjacent lenses may enter and cause interference. Therefore, a configuration in which a partition layer for preventing interference is provided between the optical lens array 14 and the solid-state imaging device 15 may be employed.

  Next, the operation of the declination image pickup apparatus 1 configured as described above will be described with reference to FIGS. 4 to 6 are schematic diagrams for explaining the operation of the declination image capturing apparatus of the first embodiment, and FIG. 4 is a diagram when white light is incident on the optical change element at an incident angle of 45 °. FIG. 5 is a diagram when white light is incident on the optical change element at an incident angle of 55 °, and FIG. 6 is a diagram when white light is incident on the optical change element at an incident angle of 35 °.

  Here, a case where the optical change element 20a picked up by the declination image pickup apparatus 1 is a hologram will be described as an example. Further, the operation of the declination image pickup apparatus 1 will be described on the assumption that the diffraction grating array of the hologram 20a formed on the surface of the sample 20 is in the horizontal direction of FIGS.

  As shown in FIG. 4, the white light emitted from the white light source 112a is collimated by the collimator lens 112a and enters the hologram 20a at an incident angle of 45 °. The white light incident on the hologram 20a is reflected by the hologram 20a (assuming that the hologram is a reflection type hologram), but the reflected light is dispersed by the diffraction action of the hologram 20a. Then, the reflected light (spread light in a certain wavelength range) having a spread in the range indicated by the alternate long and short dash line in FIG. 4 enters the objective lens 13.

  The light having each wavelength separated by the objective lens 13 is converted into parallel light. Among them, light having wavelengths λ1 and λ2 emitted from the hologram 20a at a predetermined emission angle is incident on the optical lenses 141 to 144. Thus, a single eye image is formed (that is, four declination images are obtained). More specifically, light having a wavelength λ1 is incident on the optical lenses 141 and 143 to form a single-eye image, and light having a wavelength λ2 is incident on the optical lenses 142 and 144 to obtain a single-eye image. Form. The light of wavelengths λ1 and λ2 is not completely light of a single wavelength but has a certain extent of wavelength, and the wavelengths λ1 and λ2 indicate the main wavelengths (main wavelengths).

  Here, when the incident angle of the white light emitted from the white light source 112a is changed as shown in FIG. 5 (incident angle 55 °) or FIG. 6 (incident angle 35 °), the emission angle of each wavelength dispersed by the hologram 20a. However, this is different from the case of FIG. For this reason, the spread of light incident on the objective lens 13 under the conditions of FIG. 4 (spread indicated by the alternate long and short dash line) is shifted to the right from the case of FIG. In this case, the phenomenon of shifting from the case of FIG. 4 to the left side occurs. That is, by changing the incident angle incident on the hologram 20a, the wavelength of the light incident on the optical lenses 141 to 144 also changes, and it becomes possible to obtain different single-eye images.

  Here, the case where the arrangement of the diffraction gratings of the hologram 20a is in the horizontal direction of FIGS. 4 to 6 has been described as an example. However, actually, there are cases where a plurality of types of diffraction gratings are formed in the hologram and the diffraction directions are arranged in a plurality of directions. Further, depending on how the sample 20 is placed, the arrangement direction of the diffraction direction changes even with the same hologram 20a. In this regard, in the polarization image capturing apparatus 1 of the present embodiment, it is possible to irradiate white light from a plurality of positions in the rotation direction (direction around the axis AX) at each incident angle. For this reason, it is also possible to acquire information indicating that the diffraction directions are arranged in any direction from a plurality of declination images acquired by sequentially turning on the plurality of white light sources 12.

  As described above, according to the declination image capturing apparatus 1 of the present embodiment, a plurality of (four) declination images can be obtained by turning on one white light source. The plurality of white light sources 11 are arranged in the rotational direction (eight) at each of a plurality of positions (three positions) where the incident angle of the white light to the optical change element 20a is different. For this reason, by turning on each of the plurality of (24) white light sources 11 in sequence, a very large number of declination images can be acquired with a simple operation. Furthermore, in this configuration, since the imaging unit constituted by the optical lens array 14 and the solid-state imaging device 15 can be made small, an advantage that a device capable of acquiring a very large number of declination images with a simple operation can be made compact. Also have.

  The declination image capturing apparatus 1 of the present embodiment is suitable, for example, for performing authenticity determination of a hologram formed on a credit card or the like. That is, for example, a declination image relating to a real hologram is captured in advance by the declination image capturing apparatus 1, and the data is stored. Then, a hologram to be discriminated whether or not it is a fake is imaged by the declination image capturing apparatus 1, and the obtained declination image is compared with a real declination image previously stored as data. Since the declination image capturing apparatus 1 can efficiently acquire a large number of declination images, it is possible to perform accurate true / false discrimination efficiently.

In addition, in order to know the arrangement direction of the diffraction gratings formed on the hologram from the declination image of the declination image pickup apparatus 1, it is possible to further determine true / false by specifying the diffraction grating period d (diffraction grating interval). Is possible. In a diffraction grating, the angle between the incident light and the diffraction grating normal (incident angle) is α, the angle between the diffracted light and the diffraction grating normal (exit angle) is β, the order of the diffracted light is n, When the wavelength is λ, the following formula (1) is established.
d × sin α + d × sin β = nλ (1)

  In the declination imaging apparatus 1, among the conditions for obtaining each single-eye image, the incident angle α, the outgoing angle β, and the order n of the diffracted light are determined by the optical design. For this reason, by estimating the wavelength λ of the diffracted light from the single eye image, the diffraction grating period d can be obtained by the above equation (1), and authenticity determination can be performed.

  As a method for estimating the wavelength λ of diffracted light from a single-eye image, for example, non-patent literature (Japan Optical Society Annual Academic Lecture Optics Japan 2005 Preliminary Proceedings, p. 576 (2005. 11.25, Tokyo)) Techniques can be used. Hereinafter, a method for estimating the wavelength λ of diffracted light from a single-eye image will be briefly described with reference to FIG. FIG. 7 is a diagram for explaining a method for estimating the wavelength of diffracted light from a single-eye image using rg chromaticity coordinates.

In estimating the wavelength λ of diffracted light from a single-eye image, the following rg chromaticity coordinates are used. The pixel values Vi (i = r, g, b) of the RGB sensors of the solid-state image sensor 15 are the spectral distribution H (λ) of the diffracted light and the spectral response characteristics Si (λ) (i = r, g, b) and can be expressed as the following formula (2). In addition, k in Formula (2) is a coefficient.

The chromaticity coordinates (r, g) are obtained as follows using the pixel values Vr, Vg, Vb of the RGB sensors.
r = Vr / (Vr + Vg + Vb)
g = Vg / (Vr + Vg + Vb)

  In the rg plane shown in FIG. 7, white circles are chromaticity coordinates obtained when light of each wavelength (single wavelength light) enters the solid-state imaging device 15. Here, the chromaticity coordinates are obtained by calculation from a data sheet that gives the characteristics of the solid-state imaging device 15. In the rg plane shown in FIG. 7, black circles (equal energy white point) are chromaticity coordinates when light (equal energy white light) having the same power for each wavelength component is incident on the solid-state imaging device 15. It is obtained by calculation.

  In the declination image pickup apparatus 1, a single-eye image obtained by irradiating light from the direction in which the diffraction gratings are arranged is ideally that single-wavelength light (diffracted light) is incident on each of the optical lenses 141 to 144. Should be formed. However, in actuality, it is considered that white light that has not contributed to diffraction in addition to single-wavelength light (diffracted light) is incident on the optical lenses 141 to 144 to form a single-eye image. For this reason, it is considered that the actually measured chromaticity coordinates acquired from each individual eye image are present on a line connecting the point on the spectrum locus obtained by connecting the white circles in FIG. .

  Therefore, the measured chromaticity coordinates (points marked with X in FIG. 7) are acquired from the single eye image, and the extension line of the line connecting the coordinates and the equal energy white point W intersects the spectrum locus (intersection point). ), The wavelength λ of the diffracted light (λ in the above formula (1)) can be estimated.

(Second Embodiment)
Next, a declination image capturing apparatus according to the second embodiment will be described. 8A and 8B are schematic diagrams for explaining the configuration of the declination image capturing apparatus of the second embodiment. FIG. 8A is a cross-sectional view, and FIG. 8B is a plan view. FIG. 8B is a diagram showing only the relationship between the white light source and the collimating lens and the sample on which the optical change element is formed.

  The declination image capturing apparatus 2 of the second embodiment is the same as the declination image capturing apparatus 1 of the first embodiment except that the number of white light sources 21 and the number of collimating lenses 22 is one each. It has a configuration. Hereinafter, this different configuration will be described. In addition, portions that overlap with the declination image capturing apparatus 1 of the first embodiment are denoted by the same reference numerals, and the description thereof is omitted unless particularly necessary.

  The white light source 21 and the collimating lens 22 included in the declination image pickup apparatus 2 of the second embodiment move to change the incident angle α of white light to the optical change element 20a, as indicated by arrows in FIG. The movement for changing the position in the rotation direction (direction around the axis AX) is made possible. The axis AX is an axis that is substantially parallel to the parallel light emitted from the objective lens 13 and passes through the substantially focal position of the objective lens 13, and is the same as in the first embodiment.

  The white light source 21 and the collimating lens 22 can be moved by, for example, a white light source moving mechanism 40 shown in FIG. 9 is a schematic diagram illustrating a configuration example of a white light source moving mechanism included in the declination image capturing apparatus of the second embodiment, and FIG. 9A is a diagram of the white light source moving mechanism as viewed from above. (B) is the figure which looked at the white light source moving mechanism from the side.

  The white light source 21 and the collimating lens 22 are held by a holding member to constitute a light source unit 31. The white light source moving mechanism 40 is configured to move the light source unit 31, and includes a disk part 41, a first drive source 42, a second drive source 43, and an arm part 44. .

  The disc part 41 is rotatably arranged on the lower side of the sample stage 10 supported in a fixed state by the sample stage support part 10a. The first drive source 42 disposed on the lower side of the disc portion 41 is constituted by, for example, a stepping motor, and is disposed such that its output shaft 42a substantially coincides with the axis AX. The output shaft 42a of the first drive source 42 is fixed to the center of the disc portion 41, and the disc portion 41 is rotated clockwise and counterclockwise by driving the first drive source 42 (this direction is shown in FIG. 9). It can be rotated to any one of the expressions (when (a) is referred to).

  The second drive source 43 and the arm portion 44 are both mounted on the disc portion 31 and rotate with the rotation of the disc portion 41. The second drive source 43 fixedly arranged on the disc portion 41 is constituted by, for example, a stepping motor, and is arranged so that the extending direction of the output shaft 43a is substantially orthogonal to the axis AX on the almost surface of the optical change element 20a. Has been.

  The arm portion 44 is formed in a substantially L shape, and one end thereof is fixed to the output shaft 43 a of the second drive source 43. For this reason, the arm part 44 rotates with the drive of the 2nd drive source 43a. The light source unit 31 is attached to the other end of the arm portion 44. The light source unit 31 attached to the arm portion 44 is adjusted so that the optical axis X intersects the axis AX on the almost surface of the optical change element 20a even when the arm portion 44 rotates.

  With this white light source moving mechanism 40, in the declination image pickup apparatus 2, white light emitted from the white light source 21 is transmitted to the optical change element 20 a at a plurality of incident angles regardless of the number of the white light sources 21. Can be irradiated. And about each of several incident angles, white light can be irradiated to the optical change element 20a from the several position of a rotation direction on the basis of the optical change element 20a. Therefore, in the declination image pickup apparatus 2 of the second embodiment, the light source unit 31 is moved to a desired position and the white light source 21 is turned on at each location, as in the case of the first embodiment. A large number of declination images can be acquired with a simple operation. Further, as in the case of the first embodiment, there is an advantage that a device capable of acquiring a very large number of declination images with a simple operation can be reduced in size.

(Other)
The embodiment described above is an exemplification of a declination image capturing apparatus to which the present invention is applied, and the scope to which the present invention is applied is not limited to the configuration described above.

  For example, the arrangement of the plurality of white light sources 11 shown in the first embodiment may be changed as appropriate. That is, for example, the size and number of incident angles at which white light is incident on the optical change element 20a, the arrangement interval in the rotation direction (the direction around the axis AX), and the like may be appropriately changed.

  Further, in the declination image capturing apparatus 1 of the first embodiment, the distances of the white light emitted from each of the 24 white light sources arranged in total to the optical change element 20a are almost equal. It was decided to be placed in. However, the present invention is not limited to this configuration. For example, when a plurality of collimating lenses 12 are provided as in the declination image capturing apparatus 1 of the first embodiment, the distance from each white light source to the optical change element 20a is different from each other. Is also possible.

  Moreover, although the number of optical lenses included in the optical lens array 14 in the declination image pickup devices of the first and second embodiments is four, the number is not necessarily limited to this number, and the number may be changed as appropriate. .

  In addition, it is possible to irradiate the optical change element 20a with white light at a plurality of incident angles, and for each of the plurality of incident angles, optically emit white light from a plurality of positions in the rotation direction with reference to the optical change element 20a. For example, a declination image capturing apparatus having a configuration that can irradiate the target changing element 20a may be realized by the following configuration. That is, the configuration that can irradiate the optical change element 20a with white light at a plurality of incident angles is the same as the configuration of the first embodiment (configuration using a plurality of white light sources) or the configuration of the second embodiment (white light source is used). This is realized by the same method as in the configuration using a white light source moving mechanism. For each of the plurality of incident angles, the optical change element 20a has a configuration capable of irradiating white light toward the optical change element 20a from a plurality of positions in the rotation direction with reference to the optical change element 20a. It implement | achieves by the structure which enables rotation of the sample stand 10 which mounts the sample 20 formed. Even with such a configuration, it is possible to provide a declination image capturing apparatus that can be miniaturized and that can acquire as many declination images of the optically variable element as easily as possible.

  In the embodiment described above, the description has been made on the assumption that the optically variable element is of a reflective type, but the present invention is naturally applicable to a transmissive optically variable element.

  The present invention is suitable, for example, as an apparatus for capturing a declination image of an optically changing element such as a hologram, and is useful as an apparatus for determining authenticity of credit cards, securities, and the like.

DESCRIPTION OF SYMBOLS 1, 2 Declination imaging device 111a-111h, 112a-112h, 113a-113h, 21 White light source 121a-121h, 122a-122h, 123a-123h, 22 Collimating lens (parallel light conversion means)
DESCRIPTION OF SYMBOLS 13 Objective lens 14 Optical lens array 15 Solid-state image sensor 20a Optical change element 141-144 Optical lens 40 White light source moving mechanism

Claims (6)

A declination image capturing apparatus for capturing a declination image of an optically variable element,
A white light source for irradiating the optically variable element with white light;
An objective lens that is arranged at a position that is approximately a focal length away from the optical change element, and that makes the light from the optical change element parallel light;
An optical lens array in which a plurality of optical lenses for condensing light from the objective lens are arranged on the same plane;
A solid-state image pickup device that picks up a single-eye image formed by each of the optical lenses;
With
When the direction around the axis that is substantially parallel to the parallel light and passes through the substantially focal position of the objective lens is the rotation direction,
Irradiating the optically variable element with the white light at a plurality of incident angles;
Each of the plurality of incident angles is capable of irradiating the white light toward the optical change element from a plurality of positions in the rotation direction with respect to the optical change element. Imaging device.   2. The declination image pickup according to claim 1, wherein a plurality of the white light sources are arranged in the rotation direction at each of a plurality of positions at which the incident angle of the white light to the optical change element is different. apparatus. The white light source is one,
2. The white light source moving mechanism according to claim 1, further comprising a white light source moving mechanism that enables movement to change an incident angle of white light to the optical change element and movement to change a position in the rotation direction. Declination imaging device.   4. The declination image according to claim 1, further comprising parallel light conversion means for converting white light emitted from the white light source into parallel light and causing the light to enter the optical change element. 5. Imaging device.   5. The declination image capturing apparatus according to claim 1, wherein the optical lenses are two-dimensionally arranged in two rows and two columns.   6. The declination imaging apparatus according to claim 1, wherein the white light source is a light emitting diode.

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