JP2000214045A - Hologram inspecting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain color holograms with small variations in luminosity and color reproducibility by taking luminosity obtained from the diffraction efficiency distribution of regenerated light from each hologram as a parameter and determining quality on the basis of whether the parameter lies within a reference range or not. SOLUTION: A white color distribution at the constant spectral luminous efficacy reflectance is hardly changed when the peak value of diffraction efficiency and its half width fluctuate. Therefore, by maintaining spectral luminous efficacy reflectance approximately constant in the case of color hologram, it is possible to obtain holograms with preferable color reproducibility and to maintain their luminosity approximately constant. Therefore, in the case of reproducing volume holograms by an optical system for full-color hologram reproduction through the use of a photosensitive material 20, a hologram original plate 21, etc., luminosity especially spectral luminous efficacy reflectance obtained from the profile of diffraction efficiency is used as a parameter. Then by determining a hologram as a non-defective if the parameter lies within a preset reference range (i.e., 5.4-9) and excluding it as a defective if the parameter lies outside the range, it is possible to obtain holograms with small variations in luminosity and color reproducibility.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hologram inspection method, and more particularly to a hologram inspection method for obtaining a color hologram having a small variation in brightness and color reproducibility when it is manufactured by photographing or copying.

[0002]

2. Description of the Related Art Conventionally, a full-color hologram composed of R (red), G (green), and B (blue) is photographed by an optical system as shown in FIG. In this example, a full-color Lippmann hologram (reflection hologram) is photographed, and a photosensitive material 20 such as a photopolymer is used.
As a light source, an R laser 1 (for example, a Kr laser (64
7 nm)), a G laser 2 (for example, an Ar laser excited dye laser (553 nm)), and a B laser 3 (for example, an Ar laser (458 nm)), and in order to synthesize laser light from these into one optical path, A total reflection mirror 4 and dichroic mirrors 5 and 6 are used. In the case of the arrangement shown, the dichroic mirror 5 is a red narrow-band mirror having a non-reflection coating on the back surface, and the dichroic mirror 6 is a wavelength 500 nm having a non-reflection coating on the back surface.
Although the mirror selectively reflects only the above light, the arrangement of the lasers 1 to 3 is not limited to the illustrated one and can be changed. In this case, the arrangement of the total reflection mirror 4, the dichroic mirrors 5 and 6, and The reflection band needs to be changed.

[0003] A laser 1 of three colors RGB combined via a total reflection mirror 4 and dichroic mirrors 5 and 6
3 are split into two light beams by a half mirror 7, and one light passes through a mirror 8 and a lens 9 to form a pinhole 1.
The divergent light emitted from the pinhole 10 after being converged to 0 is obliquely incident from one side of the photosensitive material 20. The other split light is condensed on the pinhole 14 via the mirrors 11 and 12 and the lens 13, and the divergent light emitted from the pinhole 14 is incident on the other side of the photosensitive material 20,
Both divergent light beams interfere in the photosensitive material 20, in which a hologram of an object illuminated with, for example, divergent light emitted from the pinhole 14 is recorded.

In order to duplicate a similar hologram from a full-color hologram master consisting of three primary colors of RGB, an optical system as shown in FIG. 2 is used, for example. This example is an example in which a full-color Lippmann hologram (reflection type hologram) is duplicated.
R laser 1, G laser 2, B laser 3
The laser light from these is used as a total reflection mirror 4
The light is combined into one optical path by the dichroic mirrors 5 and 6. Synthesized RGB three color lasers 1-3
The divergent light emitted from the pinhole 10 passes through the lens 9 and the divergent light emitted from the pinhole 10 is brought into close contact with the hologram master 21 via the refractive index matching liquid.
0, and the incident light and the diffracted light from the hologram master 21 interfere with each other in the closely adhered photosensitive material 20, whereby a color hologram having the same characteristics as the hologram master 21 is copied.

[0005]

When a volume hologram is photographed or copied in the arrangement shown in FIGS. 1 and 2, contact of an exposed photosensitive material with an adhesive or the like, vibration during photographing, Due to the mode hop of the light source or the like, a distribution occurs in the peak value of the diffraction efficiency and its half-value width in the hologram for each shot (each photographing).

As described above, when a distribution occurs in the peak value of diffraction efficiency and its half-value width for each shot, and particularly when such a distribution occurs in a color volume hologram, any sample is regarded as a non-defective product and any sample is regarded as non-defective. Conventionally, as a criterion for determining a good product, a visual inspection or a peak value of diffraction efficiency has been used.

However, as will be described later, it has been found that, particularly in the case of a color hologram, to obtain a hologram with good color reproducibility, the luminous reflectance should be made substantially constant.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a hologram inspection method for obtaining a color hologram having a small variation in brightness and color reproducibility.

[0009]

A hologram inspection method according to the present invention which achieves the above object is a method for inspecting a plurality of holograms obtained by photographing the same subject or a plurality of holograms duplicated from the same master. The method is characterized in that brightness obtained from the diffraction efficiency distribution is used as a parameter, and when the parameter is within a preset reference range, it is judged as good, and when it is outside the reference range, it is excluded as defective.

In this case, when the hologram is a color volume hologram, it is desirable to use luminous reflectance as a parameter thereof.

In addition, a predetermined reference range has a lower limit, and if the reference range falls below at least the lower limit, it can be excluded as a defective product.

It is desirable that the luminous reflectance be obtained by calculation from a diffraction efficiency distribution obtained by actually measuring the luminous reflectance.

The diffraction efficiency distribution can be measured using a spectrophotometer.

In the present invention, the brightness obtained from the diffraction efficiency distribution of the reproduction light from each hologram, in particular, the luminous reflectance is used as a parameter, and when the parameter is within a predetermined reference range, it is determined to be non-defective. Since the holograms other than the holograms are excluded as defectives, holograms having small variations in brightness and color reproducibility can be easily selected based on a certain objective criterion.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The principle of the present invention will be described below based on embodiments. R region of volume type color hologram,
Assuming that the diffraction efficiency profiles (diffraction efficiency distributions) in the G region and the B region are η _r , η _g , and η _b , respectively, the diffraction efficiency distribution η _all (λ) of the entire hologram, where λ is the wavelength.
Η _all (λ) = η _r + η _g + η _b − (η _r η _g + η _g η _b + η _b η _r ) (1) Assuming that the spectral distribution of the illumination light is P _s (λ), the spectral distribution P (λ) of the light diffracted from the hologram is P (λ) = P _s (λ) η _all (λ) (2) Becomes The tristimulus values X, Y, and Z in the CIE display system are as follows.

X = 100 × ΔP (λ) x ′ (λ) dλ / ΔP _s (λ) y ′ (λ) dλ Y = 100 × ΔP (λ) y ′ (λ) dλ / ΔP _s (Λ) y ′ (λ) dλ Z = 100 × ΔP (λ) z ′ (λ) dλ / ΔP _s (λ) y ′ (λ) dλ (3) where x ′ (λ ), Y ′ (λ) and z ′ (λ) are spectral tristimulus values.

The chromaticity coordinates (x, y) represented by the CIE display system are obtained by the following equation: x = X / (X + Y + Z), y = Y / (X + Y + Z) (4)

The luminous reflectance of the hologram is 3
It is equal to Y in the stimulus values X, Y, Z. FIG. 3 shows the relationship between the half value width of the diffraction efficiency and the peak value of the diffraction efficiency when the luminous reflectance is constant, and FIG. 4 shows the white position on the xy chromaticity diagram at that time. Here, the diffraction efficiency profiles (diffraction efficiency distributions) of the holograms of R, G, and B each have a peak value of the diffraction efficiency of 50 as shown in FIG.
%, And the half width is based on 15 nm.

As can be seen from FIG. 4, the distribution of white color when the luminous reflectance is constant hardly changes even if the peak value of diffraction efficiency and its half-value width fluctuate. From this, it can be seen that in the case of a color hologram, a hologram with good color reproducibility can be obtained if the luminous reflectance is kept substantially constant.
When the luminous reflectance is kept substantially constant, the brightness of the hologram can be kept substantially constant according to the definition.

From the above results, in the present invention, FIG.
And when photographing or copying a large number of volume holograms in the arrangement as shown in FIG. 2, in order to obtain a hologram with small variations in brightness and color reproducibility, the brightness obtained from the diffraction efficiency profile, particularly the luminous reflectance Is used as a parameter, and when the parameter is within a preset reference range, it is determined as a non-defective product, and when the parameter is outside the range, especially when the parameter falls below a lower limit value, it is removed as a defective product.

Since the hologram to be used for graphic arts is relatively insensitive in terms of color reproducibility and brightness variations, for example, holograms whose parameters fall within a range of ± 25% with respect to a preset reference value are acceptable. And those outside the range are regarded as defective.
Further, in the case of a hologram optical element such as a white scattering plate, the variation in color reproducibility and brightness is severe, and for example, those whose parameters fall within a range of ± 5% with respect to a preset reference value are regarded as good products. And those outside the range are regarded as defective.

One specific example will be described. 2, the photosensitive material 20 is HRF800X001 manufactured by DuPont.
Using a Kr laser (wavelength 647 nm) as the R laser 1, an Ar laser excited dye laser (wavelength 553 nm) as the G laser 2, and an Ar laser (wavelength 458 nm) as the B laser 3, the volume of the white scattering plate The hologram was duplicated. The peak wavelength, the diffraction efficiency, and the half width of the duplicate hologram as a reference are as follows. FIG. 6 shows the diffraction efficiency distribution in that case. However, FIG. 6 is obtained by simply inverting the spectral transmittance distribution measured using a spectrophotometer to the diffraction efficiency distribution, and does not match the value of the diffraction efficiency at the following peak wavelength.

Peak wavelength Diffraction efficiency Half-width 441.5 nm 43.77% 9.5 nm 537.5 nm 47.07% 12.5 nm 630.5 nm 28.96% 22.5 nm Obtain the luminous reflectance of this reference hologram. It is 7.2 when calculated from the obtained data. As mentioned above, if the target hologram is for graphic arts,
This 7.2 ± 25%, that is, the luminous reflectance is 5.4.
A product in the range of ~ 9 is regarded as a good product, and a product outside the range is regarded as a defective product. In the case of a hologram optical element, 7.2 ± 5%, that is, the luminous reflectance is 6.84.
Goods in the range of 7.56 to 7.56 are considered good, and those out of the range are bad.

Although the hologram inspection method of the present invention has been described based on its principle and embodiments, the present invention is not limited to these embodiments and can be variously modified. In addition,
In the present invention, the diffraction efficiency distribution of each hologram used when calculating the luminous reflectance can be objectively measured using a spectrophotometer or the like.

[0025]

As is apparent from the above description, according to the hologram inspection method of the present invention, the diffraction efficiency distribution of reproduction light from each of a plurality of holograms photographing the same subject or a plurality of holograms duplicated from the same master is used. Using the obtained brightness, especially the luminous reflectance as a parameter,
If the parameter is within a preset reference range, it is regarded as a non-defective product, and if the parameter is outside the range, it is rejected as a defective product. Therefore, holograms with small variations in brightness and color reproducibility can be easily selected based on a constant objective standard. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a full-color hologram imaging optical system to which the present invention can be applied.

FIG. 2 is a diagram showing a configuration of a full-color hologram duplication optical system to which the present invention can be applied.

FIG. 3 is a diagram showing the relationship between the half value width of diffraction efficiency and the peak value of diffraction efficiency when the luminous reflectance is constant.

FIG. 4 is a diagram showing a white position on an xy chromaticity diagram when the luminous reflectance is constant.

FIG. 5 is a diagram showing a profile of diffraction efficiency of a reference hologram in the case of FIGS. 3 and 4;

FIG. 6 is a diagram showing a diffraction efficiency distribution of a reference hologram according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... R laser 2 ... G laser 3 ... B laser 4 ... Total reflection mirror 5, 6 ... Dichroic mirror 7 ... Half mirror 8, 11, 12 ... Mirror 9, 13 ... Lens 10, 14 ... Pinhole 20 ... Photosensitive material 21 … Hologram master

Claims (5)

[Claims] In a method for inspecting a plurality of holograms photographing the same subject or a plurality of holograms duplicated from the same master, brightness obtained from a diffraction efficiency distribution of reproduction light from each hologram is used as a parameter. A hologram inspection method, wherein a hologram inspection method is characterized in that when the hologram is within a predetermined reference range, it is regarded as a non-defective product, and when it is out of the reference range, it is excluded as a defective product. 2. The hologram inspection method according to claim 1, wherein the hologram is a color volume hologram, and the parameter is a luminous reflectance. 3. The hologram inspection method according to claim 1, wherein the preset reference range has a lower limit, and if the reference range falls below at least the lower limit, the hologram inspection method is excluded. 4. The hologram inspection method according to claim 2, wherein the luminous reflectance is calculated from a diffraction efficiency distribution obtained by actually measuring the luminous reflectance. 5. The hologram inspection method according to claim 4, wherein the diffraction efficiency distribution is measured using a spectrophotometer.