WO1997015871A1

WO1997015871A1 - Hologram recording method and apparatus

Info

Publication number: WO1997015871A1
Application number: PCT/JP1996/003024
Authority: WO
Inventors: Hideyuki Wakai
Original assignee: Komatsu Ltd.
Priority date: 1995-10-27
Filing date: 1996-10-18
Publication date: 1997-05-01
Also published as: TW312757B; JPH09127855A

Abstract

A high-quality hologram in which substantially no noise light occurs during the reproduction and permeation thereof is put on the market. The intensity of reference light during the recording of a hologram and a ratio r of the intensity of the reference light to that of object light are determined so that an interference fringe formed by the object light and reference light constitutes a suitable first intensity SR within the latitude of a hologram; a ratio N/SR of a second intensity of an interference fringe formed by a plurality of wave fronts of the object light to the first intensity becomes not higher than a predetermined level Nc; and a ratio N/SR of a third intensity of an interference fringe formed by the secondary light, which is reproduced by the interference fringe formed by a plurality of wave fronts of the object light, and reference light to the first intensity becomes not higher than the predetermined level Nc.

Description

Hologram recording method and recording apparatus

The present invention provides a method for recording a plurality of objects by recording interference fringes between a plurality of object beams and reference beams.

TECHNICAL FIELD The present invention relates to a hologram recording method and a hologram recording apparatus for recording a wavefront of an object beam on a hologram.

Background art

The hologram records the wavefronts of the plurality of object lights by recording interference fringes between the plurality of object lights and the reference light.

Here, as the material of the hologram, a silver salt photosensitive material, a photosensitive polymer, or the like is usually used, and the above-described interference fringes are recorded. The photosensitive latitude (exposure range) is determined for each photosensitive material. I have. For this reason, strong fringes or weak fringes have characteristics that cannot be recorded because they are out of latitude.

Therefore, when recording on a hologram, the light intensity ratio between the object light and the reference light is usually set between 1: 1 and 1: 4 so that the object light will interfere with the reference light on average. .

As an example of the use of a photogram in which the wavefronts of multiple object beams are recorded by interference with a reference beam, see Japanese Patent Application No. 7-2 4 7 6 5 No. 4).

FIG. 6 is a schematic diagram showing a three-dimensional shape measuring apparatus to which a confocal optical system is applied.

In this device, the hologram 3 functions as a point light source array of an optical system and an optical component that transmits received light.

That is, the hologram 3 is used as a point light source generating means, When the reference light from the laser oscillator 9 as a light source is incident, the light is reproduced as if the light were emitted from each of the pinholes pl to pn of the pinhole array PH.

Thus, the hologram 3 reproduces the object light by the reference light. The object light is a plurality of wavefronts emitted from each of the pinholes p1 to pn of the pinhole array PH. In this embodiment, a plurality of parallel lights converted by the lens 4 are assumed.

The reconstructed multiple object lights are focused on the inspection surface of the measured object 7 by the lens 5, and the light reflected by the object 7 is converted into a pinhole array through the lens 5, hologram 3, and lens 4. Detected by photodetector array 8 behind PH.

The output of each photodetector of the photodetector array 8 is input to a three-dimensional measuring unit (not shown). In the three-dimensional measuring unit, the movement of the moving stage 6 in the Z direction is controlled by a moving control unit (not shown). The output of each detector of the photodetector array 8 is sequentially sampled along with the movement of the object, and the position in the Z direction when each output becomes maximum is detected as the surface position of the measured object 7.

FIG. 1 shows an apparatus configuration for exposing a hologram 3 used in the apparatus of FIG.

As shown in FIG. 1, the light having the characteristic of linearly polarized light emitted from the laser oscillator 9 has its polarization direction rotated by the 12-wavelength plate 12, and is incident on the polarization half mirror 14.

Therefore, by adjusting the rotational position of the 12-wavelength plate 12, it is possible to adjust the splitting ratio of the light split in two directions in the polarization half mirror 14 to a desired value. That is, the intensity ratio between the object light and the reference light can be adjusted.

The light used as the object light split by the polarization half mirror 14 is adjusted to light having the same polarization direction as the reference light by the 12-wave plate 13. Note that a similar wave plate may be inserted on the reference light side to adjust the polarization direction of the reference light according to the object light, or it may be inserted in both sides and adjusted so that the polarization directions of both become the same. You may. In short, as long as the polarization directions of the reference light and the object light match, such a configuration may be adopted. The object light is incident on the hologram 3 via the mirrors 15 and 16, the lenses 17 and 18, the pinholes pl to _{pn of} the pinhole array PH, and the lens 4, and as object light having different angles. Be recorded. In the above-mentioned Japanese Patent Application No. Hei 7-246758 (Japanese Patent Application No. Hei 6-237804), the hologram 3 is arranged at the positions indicated by * 1 and 2 in FIG. Although optical systems are also disclosed, they are all equivalent in that a plurality of non-parallel light wavefronts are recorded on the hologram 3. Further, at the time of hologram exposure, it is not necessary to arrange components used only for three-dimensional measurement, such as the lens 5, the object to be measured 7, the moving stage 6, and the like.

By the way, in the hologram 3 exposed in this manner, if the intensity ratio of the object light and the reference light at the time of recording is set to the normal value as described above, the fringes due to the interference between the object light and the reference light are simultaneously generated. The fringes due to the interference between the plurality of wavefronts are also recorded. Here, the interference fringes between a plurality of wavefronts of the object light are, for example, assuming that two wavefronts, A and B, are assumed as the object light, as shown in Fig. 4, the wavefronts of A and B interfere with each other. A possible stripe C. In FIG. 4, the reference light is shown by a broken line and is omitted for the sake of simplicity.

Here, due to interference fringes C recorded on the hologram 3 by the object lights A and B, the hologram 3 has characteristics as shown in FIGS. 5 (a) to 5 (c).

In other words, although there is one interference fringe C recorded on the hologram 3, the interference fringe C has the property of reproducing the object light B with the object light A at the same time as reproducing the object light B with the object light A. So

(a) In addition to the reproduction of the object light B due to the incidence of the object light A, the object light A is incident on the interference fringe that has the characteristic of reproducing the object light A by the object light B. Thus, the secondary light (dashed line) is also regenerated (see Fig. 5 (a)). Also,

(b) In addition to the reproduction of the object light A due to the incidence of the object light B, the object light B is incident on the interference fringe that has the characteristic of reproducing the object light B by the object light A. As a result, the double-order light (dashed line) is also reproduced (see Fig. 5 (b)). Also,

(c) Due to the simultaneous incidence of the object beams A and B, the total of the object beam B and the secondary beam (dashed line) where the object beam A is diffracted, and the object beam A and the secondary beam (dashed line) where the object beam B is diffracted Four lights Is reproduced (see Fig. 5 (c)).

As the number of object beams A and B decreases, such secondary light explosively increases. In FIGS. 5 (a) to 5 (c), the transmitted lights of the object lights A and B are omitted for simplicity.

Even during the recording of the hologram 3, such a secondary light is gradually reproduced by the object light as the interference fringes c between a plurality of wavefronts of the object light are recorded. It is recorded by the reference light. That is, fringes due to interference between the secondary light (dashed line) and the reference light are also recorded.

As a result, the following three types of interference fringes are recorded in the hologram 3 within the latitude ude of the hologram material.

(α) Interference fringes caused by object light and reference light (reflection hologram)

(β) Interference fringes caused by multiple wavefronts of object light (transmission hologram)

(y) Interference fringes due to multiple-order light and reference light reproduced by interference fringes due to multiple wavefronts of object light (reflection hologram)

Here, when the hologram 3 is reproduced by the reference light, the interference fringe ( _α ) reproduces the object light, but the interference fringes () and (y) reproduce the light different from the object light. I will. For this reason,

(1) Part of the reference light is diffracted and observed as noise light with respect to the reproduction object light.

(2) Since a part of the reference light is diffracted as noise light, the diffraction efficiency of the reproduction object light decreases.

There was a problem.

The light transmitted through the hologram 3 is caused by interference fringes (/ 3) recorded by a plurality of wavefronts of the object light.

(3) Part of the transmitted light is diffracted and observed as noise light for the transmitted light. And, by the interference fringes (/ 3) and (y),

(4) Since a part of the transmitted light is diffracted as noise light, the transmittance of the transmitted light is reduced.

There was a problem. Disclosure of the invention

An object of the present invention is to solve the above problems (1) to (4).

Therefore, in the main invention of the present invention,

A method of recording a mouthgram that records the wavefronts of the plurality of object lights on a hologram by recording interference fringes between the plurality of object lights and the reference light,

Interference fringes caused by the object light and the reference light have an appropriate first intensity within the latitude of the hologram; and

The ratio of the second intensity of the interference fringes due to the plurality of wavefronts of the object light to the first intensity is equal to or less than a predetermined value, and

E, so that the ratio of the third intensity of the interference fringes due to the secondary light and the reference light reproduced by the interference fringes between the plurality of wavefronts of the object light to the first intensity is equal to or less than a predetermined value. The intensity of the reference light and the ratio of the intensity of the reference light to the intensity of the object light at the time of recording the oral gram are determined.

According to this configuration, at the time of hologram recording, by adjusting the intensity of the reference light and the ratio of the intensity of the reference light to the intensity of the object light to an appropriate value, the hologram has the above-mentioned (α) Only the interference fringes due to the object light and the reference light are recorded, and are reproduced by the interference fringes between the plurality of wavefronts of the object light (β) and the interference fringes between the plurality of wavefronts of the object light ( _γ ) above. The interference fringes due to the secondary light and the reference light have low intensity and cannot be recorded.

For this reason, a high-quality hologram with little noise light can be provided on the market during reproduction and transmission. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a diagram showing a configuration example of an optical system used for implementing a hologram recording method and a recording apparatus according to the present invention.

FIG. 2 is a flowchart showing a processing procedure for determining the ratio of the intensity of the reference light and the intensity of the object light incident on the hologram to the intensity of the reference light in the apparatus of FIG. It is.

FIG. 3 is a graph showing the ratio of the intensity of the object light to the intensity of the reference light on the horizontal axis, and the ratio of the intensity of the noise light to the intensity of the reproduced object light on the vertical axis.

FIG. 4 is a diagram illustrating interference fringes recorded on a hologram.

FIGS. 5 (a), (b), and (c) are diagrams illustrating the secondary light reproduced by the interference fringes shown in FIG.

FIG. 6 is a diagram showing a configuration of a confocal optical device that performs three-dimensional shape measurement using a hologram. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of a hologram recording apparatus and recording method according to the present invention will be described with reference to the drawings.

The apparatus configuration for exposing the hologram 3 is as shown in FIG. 1 described above.

That is, as shown in FIG. 1, the light emitted from the laser oscillator 9 passes through the polarizing half mirror 14 through the 12-wavelength plate 12 and further passes through the lenses 10 and 11 as the reference light. To the hologram 3. Further, the light emitted from the laser oscillator 9 is reflected by the polarization half mirror 14 via the one-two-wave plate 12, and further reflected by the 1 Z two-wave plate 13, the mirrors 15, 16, and the lens 1. 7, 18 and incident on the hologram 3 as object light via the pinholes pl to pn and the lens 4 of the pinhole array PH.

Therefore, the intensity (light amount) R of the reference light can be adjusted by adjusting the oscillation output of the laser oscillator 9.

The adjustment of the oscillation output of the laser oscillator 9 may be controlled by adjusting the oscillation intensity of the laser oscillator 9 itself, or by disposing a filter having a variable transmittance at the emission port of the laser oscillator 9. You can control it.

The ratio r of the intensity of the object light to the intensity of the reference light is obtained by adjusting the rotation position of the half-wave plate 12 and adjusting the splitting ratio of the light split in two directions in the polarizing half mirror 14. , Can be adjusted. The adjustment of the intensity R and the intensity ratio r of the reference light may be automatically performed by a controller that controls the laser oscillator 9 and the 1Z two-wavelength plate 12, or may be performed manually.

Next, conditions for determining the strength R and the strength ratio r will be described.

As described above, the three types of interference fringes recorded on hologram 3,

The intensity of such stripes changes according to the intensity of the reference light and the object light during recording.

Now, assuming that the average intensity of one object light is s, the number of object lights is m, and the total intensity of the object light is S,

¾ = ∑ s == m s (1)

S = r R… (2)

Holds. Here, the order of the relative intensity of the above three types of interference fringes is

(a) SR (3)

(β) s 2… (4)

(y) a s 2 R… (5)

Becomes Here, a is the diffraction efficiency of the secondary light reproduced by the interference fringe of (/ 3) during exposure, and is a small value of 1 or less. In the above equations (3) to (5), the above (1),

Substituting equation (2),

(a) r R 2… (6)

(β) r 2 R 2 / m 2… (7)

(7) a r 2 R 3/2… (8)

Get. Here, assuming that the intensity R of the reference light is constant and the intensity ratio r is a number equal to or less than 1, as r becomes smaller,

(7) Equation (6) Equation-rZm2

(8) Equation Z (6) Equation = ar R / m 2 Decreases monotonically, and

Equation (6)> Equation (7)> Equation (8)

Therefore, the ratio of the intensity of the interference fringes of (3) to the intensity of the interference fringes of ( _h ), and the ratio of the intensity of the interference fringes of ( _γ ) to the intensity of the ( _α ) interference fringes are small. I will continue.

Therefore, the intensity R of the reference light is selected to be an appropriate value so that the intensity of the interference pattern (α) to be originally recorded on the hologram 3 is within the latitude of the hologram material, and the intensity ratio r is set. By selecting an appropriate value less than or equal to 1 and satisfying Equations (6), (7), and (8), only the interference pattern (α) is recorded on the hologram material, The interference fringes () and (y), which cause light, are not recorded because of their low intensity.

That is,

(α) r R 2 is the appropriate strength within the latitude of the hologram material,

(β) r 2 R 2 / m 2 force; smaller than the above r R 2, the strength of the hologram material is out of the lateral (under),

) A r 2 R 3 / m 2 force; smaller than the above r R 2, strength outside the latitude of the hologram material (under)

By adjusting the intensity R of the reference light and the intensity ratio r so that the hologram 3 is recorded, noise light can be reduced when the hologram 3 is reproduced and transmitted. That is, a high-quality hologram 3 can be manufactured.

Next, a more detailed embodiment will be described.

The device configuration when exposing the hologram 3 is assumed to be that in FIG. 1 described above.

Here, it is assumed that the adjustment of the intensity R and the intensity ratio r of the reference light is automatically performed by a controller that controls the laser oscillator 9 and the 1Z two-wave plate 12. Note that the one-two-wavelength plate 13 may also be automatically controlled so that the polarization directions of the reference light and the object light match.

The controller stores the relationship as shown in FIG. 3, and executes the processing as shown in FIG. In other words, Fig. 3 shows that, when the intensity R of the reference light is constant, the intensity ratio r of the object light to the reference light is changed by a small value of 1 or less (see the horizontal axis) and recorded on the hologram 3 and recorded. This shows the intensity ratio NZS R (vertical axis) of the intensity N of the noise light to the intensity SR of the reproduced object light when. However, the scale on the horizontal axis is an example value.

Here, the intensity SR is the intensity of light reproduced by the ( _α ) interference fringes that should be originally recorded on the hologram 3, and the intensity Ν is the cause of noise light (/ 3), (y ) Is the intensity of light reproduced by the interference fringes.

As shown in Fig. 3, as the intensity ratio r is reduced, the intensity ratio NZS R of the noise light N to the reproduction object light SR becomes smaller than the force critical value rc. (A) r The intensity of R2 becomes the intensity outside (under) the latitude of the hologram material, so that it is impossible to record the ( _α ) interference fringes to be recorded.

Therefore, the intensity ratio of the noise light intensity に対する to the reproduction object light intensity SR can be reduced to a predetermined value Nc or less (the intensity of the interference fringes of (β) and (ν) is lower than the latitude of the hologram material). (A) It is necessary to determine the intensity ratio r such that ( _a ) r R 2 has an appropriate intensity within the latitude of the hologram material and is within the range of r opt. .

Therefore, as shown in FIG. 2, the intensity R of the reference light is set to a predetermined value (step 101), and the intensity ratio r is changed within r opt, and (a) r R 2 is the hologram material. (Steps 102, 103, 105).

Here, even if the intensity ratio r is changed within the range of r opt, (a) if the intensity does not become appropriate within the latitude of the r R 2 force hologram 3 (determination YES in step 105), The process returns to step 101 again, and the same processing is repeated after resetting the intensity R of the reference light.

Therefore, if the intensity ratio r falls within the range of r opt, and (a) r R 2 force; becomes an appropriate intensity within the latitude of the hologram 3, (determination YE in step 103) S), the intensity ratio r at that time and the intensity R of the reference light finally set in step 101 are determined as final values (step 104).

Note that the method of resetting the reference light intensity R in step 101 is as follows. When ( _α ) r R 2 is an intensity that exceeds the latitude of the hologram 3, the reset value R is reduced and the value is set lower. In the case of strength, it is conceivable to increase the reset value R.

In this way, the controller sets the laser oscillator 9 and the one- and two-wavelength plate 12 so that the intensity ratio r determined in step 104 and the intensity R of the reference light finally set in step 101 are obtained. Control.

In the above description, the reference light is assumed to be parallel light, but may be diffuse light.

Also, the hologram 3 may be arranged at the positions indicated by * 1 and * 2 in FIG. Further, the plurality of object lights are not limited to parallel light, diffused light, or light emitted from a pinhole. For example, a plurality of slit lights, a plurality of spot lights by a lens array, and others may be used. Industrial applicability

INDUSTRIAL APPLICABILITY The present invention can be applied not only to a three-dimensional shape measuring apparatus to which a confocal optical system is applied, but also to optical apparatuses using holograms.

Claims

The scope of the claims

1. In a hologram recording method for recording the wavefronts of a plurality of object lights on a hologram by recording interference fringes between the plurality of object lights and the reference light, the interference fringes due to the object light and the reference light may include: A suitable first strength within the latitude, and

At the time of Holodaram recording, the ratio of the third intensity of the interference fringe due to the secondary light and the reference light reproduced by the interference fringes of the plurality of wavefronts of the object light to the first intensity is equal to or less than a predetermined value. The ratio of the intensity of the reference light and the intensity of the reference light to the intensity of the object light at, is determined.

Hologram recording method.

2. A hologram recording method for recording the wavefronts of a plurality of object lights on a hologram by recording interference fringes between the plurality of object lights and the reference light, wherein the intensity of the reference light is R, Where r is the ratio of the intensity of the reference light to the intensity of the reference light, m is the number of object lights, and a is the diffraction efficiency of the secondary light reproduced by the interference fringes due to the multiple wavefronts of the object light.

The intensity of the interference fringes due to the object light and the reference light r R 2 force; the first intensity within the latitude of the hologram is appropriate; and

The second intensity r 2 R 2 / m 2 of the interference fringes due to the plurality of wavefronts of the object light is smaller than the first intensity, the intensity is outside the latitude of the hologram, and the plurality of wavefronts of the object light are The third intensity ar 2 R 3 / m 2 force of the interference fringe due to the secondary light and the reference light reproduced by the interference fringe of the above is smaller than the first intensity and becomes an intensity outside the latitude of the hologram. To

The intensity R of the reference light during hologram recording and the ratio r of the intensity of the object light to the intensity of the reference light are determined.

Hologram recording method

3. A hologram recording apparatus that records the wavefronts of the plurality of object lights on the hologram by recording the interference between the plurality of object lights and the reference light,

Adjusting means for adjusting the intensity of the reference light and the ratio of the intensity of the reference light to the intensity of the object light; and an interference fringe formed by the object light and the reference light, having an appropriate first intensity within the latitude of the hologram, and ,

At the time of hologram recording, the ratio of the third intensity of the interference fringes due to the secondary light and the reference light reproduced by the interference fringes of the plurality of wavefronts of the object light to the first intensity is equal to or less than a predetermined value. A means for controlling the adjusting means;

Hologram recording device equipped with

4. The light emitted from the laser oscillator is branched in two directions, and a light branching ratio adjusting means for adjusting the branching ratio is provided. Light is incident as reference light, and the other light of the same branch is incident as object light,

By adjusting the light splitting ratio by the light splitting ratio adjusting means, the ratio between the intensity of the reference light and the intensity of the object light is adjusted,

By adjusting the oscillation output by the laser oscillator, the intensity of the reference light is adjusted,

The hologram recording device according to claim 3