JPS60165601A - Holography device - Google Patents

Abstract

PURPOSE:To permit easy manufacture of a phase shifter and to reduce the cost of a device by using a film having the columnar structure formed by sputtering or vapor deposition directly on a transparent substrate as the phase shifter. CONSTITUTION:A vapor deposition film 11 formed by direct sputtering or vapor deposition using ZnO as a transparent dielectric on the surface of a grass substrate is used for a phase shifter. The film 11 has the columnar structure in which the C-axis is oriented perpendicularly to the substrate 10 and the random ruggedness thereof acts effectively as a phase shifter in random phase sampling method. The film 11 is etched and the average depth DELTAD of the ruggedness is increased by adjusting the time for etching, by which a satisfactory image is obtd. If the etching is continued for further longer time, an island structure 11' is obtd. and the device is effective for random phase shifter method.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a holography device using a random phase sampling method or an analog random phase shifter method.

(Prior art and its problems) In Fourier transform holography, which is used for high-density recording of image information, so-called spike noise occurs due to the finite dynamic range of the recording medium or self-interference between light beams from a coherence light source. ,
Speckle noise is likely to occur, and both of these are factors that reduce the image quality of both raw images.

Therefore, by performing spatial sampling at appropriate intervals determined depending on the size of information to be recorded and performing recording and reproducing with spatial frequency spectral band compression, speckle noise etc. can be reduced and there is no problem in practical use. A method for obtaining quality images has been proposed. This is called the random phase sampling method, which has been further modified and improved to become the analog random phase shifter method.

Random phase sampling method or analog
A holography device using the random phase shifter method is described in the Journal of the Institute of Electronics and Communication Engineers Vol. 1, published in May 1970. 56-ONo, 5 or Tokko Sho 51
-44824 publication etc. are detailed.

By the way, conventionally, as a phase shifter used in this type of holography device, cerium oxide is deposited on a glass substrate through a special mask.

They used vapor-deposited transparent dielectrics such as zinc sulfide and magnesium fluoride.

To explain this in detail, in the case of a phase shifter used in the random phase sampling method, a pattern mask is created separately that matches the hole spacing of the sampling mesh to be used and the expression selection is randomized, and this mask is It is created by depositing a transparent dielectric in several stages over a substrate.

In addition, in the case of a phase shifter used in the analog random phase shifter method, a mask similar to that described above is used, and after supporting this at a certain distance from the substrate, the mask is passed through and the same process is performed. A transparent dielectric material is deposited to give the deposited end face a gentle tapered shape.

However, to create any phase shifter, conventionally, a vapor deposition mask with a predetermined random pattern formed thereon is required separately, and the vapor deposition process is also quite complicated, making the overall phase shifter creation process cumbersome. This led to an increase in the cost of the device.

(Objective of the Invention) An object of the present invention is to facilitate the manufacture of a phase shifter in this type of holography device and to reduce the cost of the device.

(Structure of the Invention) In order to achieve the above object, the present invention provides a phase shifter in which a columnar structure film is directly formed on a transparent substrate such as a glass plate by sputtering or vapor deposition, or a columnar structure film is further formed by chemically depositing the columnar structure film on a transparent substrate such as a glass plate. It is characterized in that it is formed by etching.

(Description of Embodiment) FIG. 1 is a schematic diagram showing the basic configuration of a fore-edge imaging device using a random phase sampling method for explaining an embodiment of the present invention.

In the figure, information illumination light 1 is reflected by a lens 2, passes through a phase shifter 3 according to the present invention, a sampling mesh 4, and an image 5, and then becomes information light 6 on the surface of an image recording medium 7. At the same time, the reference beam 8 is also irradiated here, and a hologram recording layer 9 is formed on the recording medium 7 due to the cracking.

Here, the recording medium 7 is a photographic film.

A magneto-optical recording medium is used.

Next, the phase shifter 3 according to the present invention will be explained in detail. This phase shifter 3 uses a transparent dielectric material, here zinc oxide (2no) having a hexagonal wurtzite crystal structure, on the surface of the glass substrate 10, but this zinc oxide is not passed through any mask. A thin film formed directly by sputtering or vapor deposition is used.

This sputtered or vapor-deposited zinc oxide film 11 is a polycrystalline thin film having a columnar structure in which its C axis is oriented perpendicularly to the underlying glass substrate 10.
As shown in the cross-sectional shape in a), the average thickness Da = 1 μm to several tens of μm, average concave depth ΔD = 100 μm to 800 nm, and the average uneven pitch Pa = o, iμm to several tens of μn+. ing. It has been confirmed that the random irregularities of the columnar structure film 11 function extremely effectively as the phase shifter 3 in the random phase sampling method.

By changing the various conditions during the sputtering or vapor deposition, the columnar structure film 11 can have its film thickness, surface unevenness, etc. changed as appropriate, and thus the phase shifter 3
It is possible to change the characteristics of the material in various ways. For example, the diameter of each crystal pillar can be controlled by varying the substrate concentration during fabrication.

As a method for more actively controlling the characteristics of the phase shifter 3, there is a method of chemically etching the columnar structure film 11 with acid or the like.

That is, in this columnar structure [1111], the boundary between each crystal column is a grain boundary, and when this columnar structure [1111] is etched with an acid such as hydrofluoric acid, it gradually melts from the grain boundary structure on the film surface. By adjusting the etching time, the shape of each crystal pillar can be changed considerably. For example, if etching is performed within a predetermined period of time, the longer the period of time is, the more the average depth of unevenness ΔD can be increased. It is extremely easy to form a shape in the range of 800 n1ll.

Note that the columnar structure of the film 11 and changes in its state such as the average unevenness depth ΔD can be easily confirmed by direct observation using an electron microscope or SEMIII.

Furthermore, if the columnar structure film 11 shown in FIG. 2(a) is continued to be etched for a longer period of time, it will finally be etched as shown in FIG. 2(b).
As shown in the cross-sectional shape, it takes on a shape in which transparent dielectric columns are scattered like islands.

The surface of each island-like columnar structure in this state is an extremely gentle and continuous tapered surface, and if the size and density of this island are adjusted, these island-like columnar structure films 1
1 was confirmed to be sufficiently effective as a phase shifter used in the analog random phase shifter method described above.

The configuration of holography ti@ that uses the analog random phase shifter method is the same as the device configuration shown in FIG. 1 with the sampling mesh 4 omitted, but in this method,
Since the sampling mesh 4 is not used, it is necessary to prevent the light beam from being concentrated by the phase shifter 3 as much as possible. By the way, when this method is applied to the columnar structure film 11 as shown in FIG. 2(a), the boundary change of the surface unevenness is still too steep, and the light beam is likely to be concentrated at this steep change part.
This was a problem, but the island-shaped rod structure Ti1I as shown in Figure 2 (0)! According to No. 11', the gentle taper exhibited by the surface can disperse the light beam continuously and randomly without causing any concentration of the light beam.
According to the inventor's experimental results, it was possible to obtain a reproduced image of extremely high resolution and relatively high quality with little speckle noise.

In any of the above examples, the phase shifter made of this columnar structure film uses a magneto-optical recording medium, which has high light transmittance and phase shift effect of the film itself, and has low sensitivity as a holographic recording medium. In some cases, extremely high quality image recording and reproduction has been achieved.

Further, in the above embodiments, an example was shown in which zinc oxide was used as a sputtering or vapor deposition material, but the present invention is not limited to this, and various materials can be applied as long as they form a columnar structure film. It is possible.

(Effects of the Invention) As described above, since the holography device of the present invention uses a columnar structure film formed directly on a transparent substrate by sputtering or vapor deposition as a phase shift, it is possible to create a phase shifter as in the conventional method. Although this columnar structure film does not require special masks and the process is simplified, making it easy to manufacture phase shifters and reducing costs, this columnar structure film cannot be produced using only the random phase sampling method. In addition, it is also possible to apply it to the analog random phase shifter method, and in any case, it has sufficient high performance for practical use. A small amount of high quality material can be obtained, and its practical effects are extremely large.

In addition, it is easy to control the characteristics as a phase shifter.
Characteristically, the light transmittance and phase shift effect are large, so that even when a low-sensitivity magneto-optical recording medium is used, sufficiently good image recording and reproduction can be achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the basic configuration of a holography device according to the present invention, and FIGS. 2(a) and 2(b) are sectional views showing the state of a columnar structure film constituting the phase shifter of the present invention. FIG. 2(a) is a diagram showing a columnar structure film almost immediately after sputtering or vapor deposition, and FIG. 2(b) is a diagram showing an island-shaped columnar structure formed by etching. 1... Information illumination light 2... Lens 3... Phase shifter 4... Sampling mesh 10- 5... Image 6...・
・・・・・・・・・・・・ Information light 7・・・・・・
・・・・・・・・・・・・Recording medium 8・・・・・・・・・
・・・・・・・・・Reference light 9・・・・・・・・・・・・
......Hologram recording layer 10...
...Glass substrate 11.11"...Zinc oxide sputtered film Patent applicant Nippon Gakki Manufacturing Co., Ltd. 11- Figure 1

Claims (1)

[Claims] Random phase sampling method or analog
A holography device using a random phase shifter method, characterized in that a columnar structure film formed directly on a transparent substrate by sputtering or vapor deposition is used as a phase shifter.