JPH02228686A - Apparatus for producing hologram by thermoplastic resin - Google Patents

Abstract

PURPOSE:To produce the hologram by arresting the point of the time when diffraction efficiency is high by stopping the heating of a thermoplastic resin upon detection that the intensity of the frost scattered light obtd. by a photodetector attains the max. CONSTITUTION:At least either of photodiodes 50, 52 as the photodetectors is disposed alongside a thermoplastic dry plate 10. The photodiode 50 detects the transmitted and scattered light scattered through the thermoplastic dry plate 10 and the photodiode 52 detects the reflected and scattered light from the surfaced of the frost. Reference light 26 is used for the light source of the scattered light detected by the photodiode 50. The heating of the thermoplastic resin is stopped on detection that the intensity of the frost scattered light obtd. by the photodiodes 50, 52 attains the max. The hologram having high accuracy is produced by arresting the point of the time when the diffraction efficiency is high in this way without requiring operator's skill.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a technology for producing holograms that are photographed to measure minute vibrations and deformations of objects. Regarding production equipment.

[Conventional technology]

The structure of a thermoplastic dry plate using a thermoplastic resin (thermoplastic) as a dry plate for producing a hologram is shown in FIG. 5. This thermoplastic dry plate 10 has a transparent conductive film (NESA film) layer on a glass substrate 12. 14. Optical semiconductor layer 16. Thermoplastic resin layers 18 are sequentially applied, and electrodes 20 are provided at both ends of the Nesa membrane layer 14.

To produce a hologram using such a dry plate IO, the object to be photographed is irradiated with a laser beam, and the object light reflected from the object is made to interfere with the reference light that is directly irradiated onto the dry plate IO at an appropriate angle. I will do it.

An outline of the process of manufacturing a hologram will be explained with reference to FIG. Note that the process shown in FIG. 6 is of a method called a sequential method. As shown in FIG. 5A, the corotron 22 is scanned over the thermoplastic resin layer 18 to charge the thermoplastic resin layer 18 with a positive charge and the Nesa membrane layer 14 with a negative charge. Object light 24 and reference light 26 are irradiated onto this dry plate 10 and caused to interfere with each other, as shown in FIG. 2(b). When the dry plate 10 is irradiated with this interference light, the part of the photosemiconductor layer 16 that is irradiated with the dazzling light becomes conductive, and as shown in FIG. A latent image is created.

Then, as shown in FIG. 5(c), the corotron 22 scans and charges again, and then, as shown in FIG. 2(d), electricity is applied to the Nesa film layer 14. This energization causes the Nesa membrane layer 14 to generate heat, thereby heating the thermoplastic resin layer 18. As described above, negative charges exist in the portion of the optical semiconductor layer 16 that is irradiated with light, and positive charges and negative charges are located between the thermoplastic resin layer 18. Therefore, these charges attract each other, and this attractive force causes the figure (
As shown in d), an uneven pattern is formed on the surface of the thermoplastic resin layer 18 to form a hologram.

In order to have a good hologram, it is desirable that the hologram has a high diffraction efficiency, but the diffraction efficiency has a predetermined relationship with the amount of unevenness (heat development amount) on the thermoplastic surface, and even if the heat development amount is small, it is also high. However, the diffraction efficiency will be low.

If the heating temperature of the thermoplastic resin 18 is low, sufficient unevenness on the surface of the thermoplastic cannot be obtained, and if it is too high, the thermoplastic becomes too soft and the unevenness decreases again due to surface tension. Since the temperature depends on the magnitude of the current flowing through the Nesa membrane layer 14 and the duration of the current,
It is necessary to stop the current supply when the diffraction efficiency reaches high.

Conventionally, a method as shown in FIG. 7 has been used to capture the point of good diffraction efficiency. In this method, the operator visually recognizes the object 28 as the subject.

An operator visually observes the diffracted light 2 of the reference light 26 irradiated onto the thermoplastic dry plate 10, and stops the energization when the diffracted light 2 becomes the brightest.

[Problem that the invention seeks to solve]

However, with the conventional visual inspection method, it is extremely difficult to detect the point in time when the diffracted light 2 becomes the brightest, and requires skill in five operations.

Therefore, it takes a considerable amount of time to manufacture a hologram, and the manufactured holograms tend to vary.

Furthermore, since the operator visually observes the diffracted light 2 while checking the object 28, the operator is positioned on a straight line passing through the object 28 and the dry plate 10, as shown in FIG.

It would be desirable to install a television camera or the like on this straight line to photograph the object 28 and then produce a logogram, but it is impossible to install a television camera or the like because the operator is located there.

By the way, it is known that a cloudy mist-like solid substance called frost or frost noise is generated on the thermoplastic dry plate 10 when producing a hologram. It is also known that the intensity of this frost and the peak of the diffraction efficiency described above almost completely match.

Therefore, this invention focuses on the occurrence of the above-mentioned frost, and provides a hologram production device using thermoplastic resin that can capture the point of high diffraction efficiency and produce high-precision and good holograms without requiring operator skill. is intended to provide.

[Means for solving problems]

In order to achieve the above object, a hologram manufacturing apparatus according to the present invention irradiates an object beam and a reference beam to interfere with each other by irradiating a dry plate using a thermoplastic resin as a photosensitive material, and heats the thermoplastic resin. In a hologram production device that produces unevenness on the surface of the thermoplastic resin by irradiating the hologram during the production process with an appropriate light source, the light emitted from the light source due to the frost generated during the production process is used. A light-receiving element for detecting the scattered light is provided near the dry plate, and heating of the thermoplastic resin is stopped when the intensity of the frost-scattered light obtained by the light-receiving element has reached a maximum. It is characterized by

[For production]

As mentioned above, the time when the frost intensity reaches its maximum and the time when the diffraction efficiency reaches its maximum almost completely coincide. When the intensity of the frost reaches its maximum, the frost scattered light of the light emitted from the light source becomes the brightest, so if the heating of the thermoplastic resin is stopped by the output of the light receiving element, the diffraction efficiency becomes almost the highest. Holograms can be created.

Note that the reference light used for producing a hologram may be used as the light source, or the light source may be provided separately.

〔Example〕

Hereinafter, based on the embodiments shown in FIGS. 1 to 4,
The hologram manufacturing apparatus according to the present invention will be specifically explained.

FIG. 2 schematically shows an optical system for producing a hologram, in which a first reflecting mirror 34 is provided on the optical path 32 of the laser beam emitted from the laser device 30. The optical path 32 is bent by this. A half mirror 36 is provided on this bent optical path 32, and the laser beam is reflected by this half mirror 36 and proceeds along a first optical path 38.
The light beam passes through the light beam and travels along the second optical path 40.

The first optical path 38 is reflected by a reflector 42.44 and passes through a diverging lens 46. The laser beam that has passed through this diverging lens 46 is appropriately diverged and becomes a reference beam 26 that directly irradiates the thermoplastic dry plate 10 .

A spherical mirror 48 is provided on the second optical path 40.
The laser beam traveling along the optical path 40 is reflected and diverged by this spherical mirror 48 and illuminates the object 28 which is the subject.

The light reflected by this object 28 and directed toward the thermoplastic dry plate 10 becomes object light 24.

As shown in FIGS. 1 and 2, at least one of photodiodes 50 and 52 as light receiving elements is disposed on the side of the thermoplastic dry plate 10. As shown in FIGS. The photodiode 50 is for detecting transmitted and scattered light transmitted through the thermoplastic dry plate 10 and scattered, and the photodiode 52 is for detecting reflected and scattered light from the surface of the frost. In addition, photodiode 5
The light source of the scattered light detected by the reference light 26 is
is used.

FIG. 1 schematically shows a circuit for measuring the brightness of scattered light detected by a photodiode 50, and an A/D converter 5 is connected to the photodiode 50 via an amplifier 54.
6 is connected, and its output is input to the CPU 58. One of the electrodes 20 that conduct electricity to the Nesa film layer 14 of the thermoplastic dry plate 10 is connected to an AC power source 60, and the other is connected to the AC power source 60 via a main switch 62. The output port of the CPU 58 is connected to the main switch 62, and the main switch 62 is turned on and off by the output signal.

As described above, frost occurs when a hologram is manufactured, and the scattered light detected by the photodiode 50 is the reference light 26 scattered by this frost. The relationship between this frost scattered light and diffraction efficiency is
It is generally known that the relationship shown in FIG. 4 exists. In this figure, the horizontal axis represents the heating temperature of the Nesa film layer 14, and the vertical axis represents the light intensity. The solid line represents the light intensity of the frost scattered light, and the broken line represents the light intensity of the first-order diffracted light. There is.

The optimal temperature on the horizontal axis is the temperature at which the Nesa film M14 is heated in order to obtain the aforementioned maximum unevenness pattern on the thermoplastic surface at which the light intensity of the first-order diffracted light becomes the highest. The light intensity becomes the highest, and the intensity (brightness) of the frost scattered light also becomes the highest. Comparing the changes in light intensity of frost scattered light and first-order diffracted light due to temperature.

It can be seen that the change in the intensity of the frost scattered light is more rapid until it reaches the maximum intensity, and the change in the light intensity of the −-order diffracted light is gentler. Focus on this phenomenon.

In this example, the light intensity of frost scattered light is measured.

The operation of the hologram manufacturing apparatus according to the present invention configured as described above will be explained according to the flowchart shown in FIG. Note that the hologram is manufactured by the sequential method described above. Further, as described above, preheating is performed to a temperature close to the optimum temperature at which the intensity of the frost scattered light is maximum, so that the hologram can be manufactured in as short a time as possible.

In step 301, the room temperature is measured in order to measure the environment in which the hologram is manufactured. In addition, the number of the thermoplastic dry plate 10 is input by operating keys provided in the hologram production room (step 302).
The number of the dry plate 10 is, for example, a serial number indicating the serial number, etc., and the number of the dry plate 10 used for development is
0 has been registered in advance on a floppy disk or the like, and by inputting this serial number, the resistance value of the dry plate 10, etc. is read out (step 303).
), and the Nesa film layer 14 for appropriately heating the thermoplastic resin layer 18 based on the room temperature and the resistance value of the dry plate 10.
Calculate the approximate time for energizing (step 304
), and if the shutter of the laser device is open, it is closed to prevent the object beam 24 and the reference beam 26 from irradiating the thermoplastic dry plate 10 (step 305).

Then, in step 306, a latent image is created.

This is done by initially charging the thermoplastic dry plate 10 by scanning the corotron 22 as described above (see Fig. 6(a).
)), the closed shutter is opened to irradiate the object 28, which is the subject, with a laser beam to obtain the object light 24, and the object light 24 and the reference light 26 are irradiated onto the thermoplastic dry plate 10 for exposure. (Figure 6 (
b)) Furthermore, when the exposure is completed, the shutter is closed, and then the corotron 22 is scanned again for post-charging, as shown in FIG. 6(c).

Once the latent image is formed in this manner, the Nesa film layer 14 is energized for a time corresponding to the energization time obtained in step 304, thereby preheating the thermoplastic resin layer 18 (step 307). As a result of this preheating, an uneven pattern begins to be formed on the surface of the thermoplastic resin layer 18, and the preheating ends before the frost scattered light reaches its maximum. That is, in the graph of FIG. 4, the preheating is finished at a temperature about 1 degree lower than the optimum temperature.

Next, in step 308, a shutter for the reference light 26 (not shown) is opened, and the thermoplastic dry plate 10 is irradiated with the reference light 26. This shutter for the reference light 26 is configured by, for example, being attached to the diverging lens 46 in FIG. 2. After setting the initial value L0 of the scattered light intensity (step 309), the process proceeds to step 310. This initial value is set by selecting an appropriate value smaller than the value at which the intensity of the frost scattered light becomes maximum do.

Then, the intensity L of the frost scattered light obtained by irradiating the reference light 26 is detected by the photodiode 50 (step 310), and the above initial value is compared with the scattered light intensity L1 (step 310). 31
1) If the initial value L0 is sufficiently small, the determination in step 311 will be No, so step 3
12 is the initial value, and is replaced by the scattered light intensity obtained above. and.

After heating the thermoplastic dry plate 10 for 0.1 seconds by applying electricity to the Nesa film layer 14, the process returns to step 310 and the scattered light intensity L is measured, and the scattered light intensity L1 is replaced with the above-mentioned step 312. The magnitude of the scattered light intensity is compared with the scattered light intensity (step 311).

If this determination is No, steps 312 and 313 are performed again to measure the scattered light intensity L1, which is compared with the previously measured scattered light intensity L0. If the determination result in step 311 is YES, this means that the scattered light intensity L0 measured after heating the thermoplastic dry plate 10 for 0.1 seconds is equal to or lower than the scattered light intensity L0 measured before heating. . In other words, it is the result of measuring the intensity of scattered light.

This means that the scattered light intensity, which has been gradually increasing, has started to fall, and as shown in FIG. 4, the scattered light intensity has slightly passed the point where it reaches its maximum. Therefore, the thermoplastic dry plate 10 has been heated to a temperature at which a good hologram can be obtained, and the production of the hologram is ended in step 314 without further heating.

As a result, an uneven pattern is formed on the surface of the thermoplastic resin layer 18, and a hologram is completed.

In the embodiments described above, reference light 26 is used as a light source for measuring the intensity of frost scattered light, but a light source that generates frost scattered light is provided separately from reference light 26. Furthermore, as described above, the measurement of frost scattered light may be performed using either transmitted scattered light or reflected scattered light.

〔Effect of the invention〕

As explained above, according to the hologram manufacturing apparatus according to the present invention, the intensity of the frost scattered light is detected by a light receiving element such as a photodiode, and when the intensity reaches the maximum, the current supply to the Nesa film layer is stopped and the heat is removed. Since the heating of the plastic resin is stopped, a hologram can be produced by capturing the point in time when the diffraction efficiency is high.

In addition, since the brightness of the frost scattered light is electrically detected by the light receiving element, it is possible to produce good holograms without variations without requiring the operator to be skilled as in the case of visual inspection.

Furthermore, since the frost scattered light with a rapid change in diffraction efficiency is detected, it is easier to detect the point in time when the diffraction efficiency becomes high, compared to conventional methods that detect diffracted light.

In addition, since there is no need to place a light-receiving element on a straight line passing through the object to be photographed and the thermoplastic dry plate, a hologram can be produced while monitoring by installing a television camera or the like on the straight line.

[Brief explanation of the drawing]

The drawings show a preferred embodiment of the present invention, and FIG. 1 is a schematic circuit diagram of this hologram manufacturing apparatus. Second
The figure is a principle diagram for explaining the optical system for producing a hologram. FIG. 3 is a flowchart for explaining the hologram manufacturing procedure. FIG. 4 is a graph showing the relationship between frost scattered light and diffraction efficiency. FIG. 5 is a structural diagram of a thermoplastic dry plate. FIG. 6 is a process diagram for explaining the process of manufacturing a hologram by a sequential method using a thermoplastic dry plate. FIG. 7 is a diagram illustrating the principle for capturing a point of high first diffraction efficiency in conventional hologram production. 10...Thermoplastic dry plate 12...Glass substrate 14...NESA film layer 16
... Optical semiconductor chamber 18 ... Thermoplastic resin layer (Thermoplastic N) 2
0... Electrode 24... Object light 26...
・Reference light (light source) 28...Object 50.52...Photodiode 58...CPU 60...AC power supply 62...Main switch 1 Figure 11 +1a +2 □ 11゜gPJ Mouth (C) Ward map

Claims (1)

[Claims] A dry plate using a thermoplastic resin as a photosensitive material is irradiated with an object beam and a reference beam to cause interference, and the thermoplastic resin is heated to form an uneven pattern on the surface of the thermoplastic resin. In a hologram production device that forms and produces a hologram, a suitable light source illuminates the hologram during the production process, and a light receiving element is placed near the dry plate to detect scattered light from the light source due to frost generated during the production process. A hologram manufacturing apparatus using a thermoplastic resin, characterized in that the heating of the thermoplastic resin is stopped upon detecting that the intensity of the frost scattered light obtained by the light receiving element has reached a maximum.