DE1772756C3 - Transmission hologram reconstructable with white ight - Google Patents

Description

45

The invention relates to a device that can be reconstructed with white light Transmission hologram and a method for its manufacture.

When recording a hologram, the radiation field is made through an interferometric process registered both in terms of amplitude and phase. The registration must be in such a Form take place that in the subsequent reconstruction process a corresponding modulation of the for Reconstruction used radiation can take place. Corresponding to the two possibilities of amplitude modulation and phase modulation are known as absorption and phase holograms.

Absorption holograms are also simply called Schwh'rzuniisholotiramme. S.ic have the advantage of being relatively easy to manufacture. can be as it layer by exposure of a Si I berhalogenidemuKions and subsequent photographic processing f> s obtained. The information-carrying structure consists of metallic silver. The disadvantage of absorption hologramnios lies in the extremely low utilization of the light in the reconstruction. Theoretically, the diffraction efficiency of absorption holograms is only a few percent under ideal conditions.

The second type of holograms, the ones mentioned above Phase holograms are, with regard to the utilization of the light in the reconstruction Absorption holograms are considerably superior. However, they are only of the required quality difficult to manufacture. Phase holograms are obtained e.g. B. by bleaching photographic absorption holograms. The informalion-bearing structure then consists, for. B. in a different layer thickness the photographic layer. The phase hologram produced in this way is without special Aids not visible.

With a phase hologram, the phase of the reconstructing radiation is modulated by changing the optical path length \ 'nds; herein means the index of refraction 11, the ds Wegclement in the layer. A phase modulation is possible in two different ways: I. By changing the wave length. 2. by changing the refractive index.

Another classification of the holograms is based on whether the object and reference wave during manufacture hit the photographic layer from the same side or from opposite ropes.

In the first case one speaks of transmission holograms. These can be used within certain limits determined by the grid equation can be reconstructed at any wavelength. A clear picture is therefore obtained during the reconstruction only if the light used for the reconstruction is only sufficient wavelengths from one contains narrow spectral range. In order to also carry out a reconstruction with white light you have to go to the type of holograms mentioned in the second place above, the so-called Bragg holograms (reflection holograms), pass over, when they are recorded, object and reference waves hit the photo plate from opposite sides and create a three-dimensional interference structure in the photographic layer. The reconstructed image of Bragg holograms is monochrome, although white light was used, since the well-known Bragg relationship is used for the reconstruction is decisive, the color of the reconstructed image being dependent on the angle of incidence. Such Bragg holograms, however, require photographic materials with very high resolution and correspondingly low sensitivity, the quality of which is not yet satisfactory at the moment.

The theory of Bragg holograms is e.g. B. in the work of E. N. Leith, Applied Optics, 5, pp. 1303-1311 (1966). On pages 1308 and 1309 are also experimental Results discussed. The above-mentioned dependence on the angle of incidence v is confirmed (see explanations to Fig. 9 and diagrams a, b, c on p. 1309).

The invention is based on the object of transmission holograms to develop that can be reconstructed with white light. The color of the reconstructed image does not depend on the angle of incidence. The transmission holograms should also recorded with the usual photographic materials can be.

This task is carried out with a transmission

hologram according to the invention in that the The information-carrying structure consists of a color stem. that within the visible wave length range has only one absorption band lying in a narrow spectral range. Under -FärbstolT- is here both a homogeneous dye and a mixture of several Tarbstoll compounds Roger that.

The informatimisiranende orders advantageously Structure made from a color streak. whose refractive index is a possible-.! high dispersion / property.

A further development of the invention exists in that the difference in the expansion indices of the dye and the binder in which the Faibsiolf is fogged. Möilicnst is big.

The white light reconstruction is improved if the dispersion curve of the dye has a maximum or minimum as narrow as possible in the visible range having. Likewise, the dye should have an absorption maximum with steepest flanks as possible and have narrow width.

The production of the transmission according to the invention successful in a known manner by imagewise exposure of a light-sensitive photographic layer with that reflected from the object coherent radiation and equal / urgent uniform exposure with the coherent radiation and subsequent photographic processing of the exposed silver halide emulsion layer. It will then according to the invention the colored hologram by 3 " a lumbar fold is produced.

For this purpose, in principle, all are color photographic Procedure useful. Such photographic layers are preferably used as light-sensitive Substance contain silver halides. the exposed layers then according to the usual color photographic development processes are processed The required color couplers can either be applied in the layer or in the coloring agent according to the known development process Developer be available.

Because it doesn't matter in holographic processes. whether the information-bearing structure is positive or is negative. Both negative and positive processes can be used for production or positive / positive processes such as the known silver dye bleaching process can be used.

Such methods can of course also be used to produce the colored hologram for which no silver halide is required as a photosensitive substance, e.g. B. electrophotographic processes. Process in which dyes present in the layer imagewise be bleached, or others. In principle, any method can be used to produce colored pictures leads. Those processes which lead to images of high resolution are preferred.

When using conventional photographic processes according to the principle of color development of silver halide emulsion layers, it is also possible using multilayer materials with selective sensitization 'he / a layer in a material lying on top of each other Manufacture holograms in different carbs. This makes the ilologram reconstruction also of colored objects in natural colors by means of inventive holograms possible.

The advantages of the invention are to be seen in it, i.e. the length selection in the hologram itself occurs if the reconstruction shows a white loan is used. During the reconstruction with white light, only the area of the light is then effective mad. which lies in the absorption area of the dye The other wavelengths change. if one of the disregards the dispersion effects described below, unbuilt through such a hologram, so do not contribute anything to the reconstructed image. When reconstructing such a hologram «, With white light it is therefore not necessary to use a special spectral filter.

Because dyes have the effect of the abnormal dispersion of the li '/ htes. d. H. a jump in de> Ze ^ en refractive index in the absorption range. can this dispersion in the preferred form of agitation can be used to reconstruct the hologram for phase modulation. This is for a typical example is shown in FIG. On the The abscissa is the wavelength:!, On the ordinate for the curve 1 the Absoipnon Ivw. for curve 2 tier refractive index applied.

On the short-wave side of the absorption band If there is a minimum of the refractive index, within the band it increases with increasing wavelength (anomalous dispersion), and after reaching a maximum on the long-wave side of the absorption band he falls off again. These differences in the refraction index can be converted into a wavelength-dependent one Take advantage of phase modulation.

Here one has the great advantage of phase modulation: significantly higher diffraction effect L'rad (this is the percentage of the incident light that is used for the reconstruction) of the phase hologram versus absorption holograms. At the same time there is a spectral selectivity, as they have previously shown phase holograms only as so-called Bragg holograms: but these are Due to the high spatial frequencies required, this has only been possible to date in a very poor quality. In addition comes that the refractive index difference in the maxima and minima of the dispersion curve at appropriate Dyes is so large that even with relatively small volume concentrations of the color component can achieve an effective degree of modulation. Both molecularly disperse dyes can be used as dyes as well as finely divided pigment dyes. They are chosen so that the Refractive index in the maxima or minima of the dispersion curve of the refractive index of the layer material, z. B. the gelatin, deviates as far as possible. But it is also possible to change the refractive index of the To change the layer material by inert additives to a suitable value. You can also use dyes use whose dispersion curve has such a course. that z. B. only the maximum or the minimum of the refractive index in the visible area is used.

According to the course of the absorption curve of the dye, there can be very different types of dispersion curve occur e.g. B. those with only a minimum or a maximum, several minima oiler maxima. By choosing suitable dyes can be so diverse wavelength selective Achieve effects for the phase modulation.

Compared to known holographic methods, this results in particular for the recording

17th

of colored objects and reconstruction in natural colors, significant advantages:

1. One will achieve greater light intensity in the reconstructed image here;

a) towards the (Bragg) absorption holograms, in which, in principle, the diffraction efficiency of phase holograms cannot be achieved;

b) compared to the Bragg phase holograms. because the materials suitable for this so far are still far from the theoretically possible efficiency.

2. The wavelength selective phase modulation offers for the first time the possibility of transmission phase holograms Reconstruct colored images with white light.

example 1

A photographic material consisting of a silver bromide iodide gelatin layer is used with 3.8 mol percent iodide content and an average grain size of 0.05 µm and a narrow grain size distribution.

The mean square spread of the size distribution is ~ 0.03 | im. The packing density is above 0.3 g of silver per cml. The layer is sensitized in panchromatic.

On this high resolution fine grain silver halide layer becomes the hologram structure by interference of one coming from the object and one direct beam generated; both beams must be coherent with one another and therefore expediently generated from an Hc-Ne laser (/. = 632.8 nm) by beam splitting.

The processing procedure described below makes this possible through the hologram exposure The generated latent image is transformed into a negative blue-green color image of the hologram.

1. Development for 12 minutes at 20 ° C in the following bath:

Ν, Ν-diethyl-p-phenylenediamine-

sulfate 2.75 g

Sodium hexametaphosphate 2 g

Hydroxylamine sulfate 1.2 g

Sodium sulfite 2 g

Potash 75 g

Potassium bromide 2.5 g

2,6-dibromo-1,5-dihydroxy

naphthalene Ig

2. Splash for 5 minutes.

3. Bleach 5 minutes in the following bath:

Potassium ferricyanide 42 g Potassium bromide 12g Disodium phosphate 6 g Sodium hexametaphosphate 6 g Monopotassium Phosphate 16g

7bb

4. Soaking for 5 minutes.

5. Fixation for 5 minutes in the following bath:

Ammonium thiosilicate 1 50 g

Sodium content 10 g

6. Soaking 10 minutes.

7. Drying.

ίο (All quantities refer to I liters.)

The absorption curve of the in the color ground The development of the dye obtained is indicated by curve 4 of FIG. 2 reproduced.

If the blue-green hologram structure obtained is illuminated with white light and the measured The proportion of the light diffracted in the first order of diffraction as a function of the wavelength is obtained that in curve 3 of FIG. 2 result shown. for

This curve represents the ordinate in the diagram in FIG. 2, the diffraction efficiency. This is expressed by the intensity of the diffracted light / intensity of the incident light. It can be seen that the diffraction efficiency of the HoIogram is strongly dependent on the wavelength. In a hologram that z. B. consists of silver, in contrast to this, it would be practically constant over the examined length range. The curve also shows that the maximum of the diffraction efficiency - it is about 5.4 ¹ Vn - is in the tail of the absorption band at about 440 nm. This finding, which is used in the present invention, cannot be attributed to the absorption and can be explained by the fact that there is an optimum of the absorption at which the absorption losses are not yet too great, but sufficient modulation is present. This is contradicted by the fact that approximately the same absorption is present at around 520 nm, but the diffraction efficiency there is less than 0.4 "υ.

It must also be taken into account that a diffraction efficiency of 5.4 "U is above the theoretically maximum possible value of 3.7%, which also requires ideal conditions (pure sine modulation, modulation transfer function = 1), which certainly not here Thus, these results demonstrate the real effectiveness of the phase modulation.

B e i s ρ i e 1 2

A photographic material is used, consisting of a silver bromide iodide gelatin layer with 6.3 mole percent iodide content and a mean grain size of 0.05 (im and a narrow grain size distribution. The mean square spread "of the size distribution is ~ 0.03 μm. The packing density is above 0.3 g of silver per cm ». The layer is panchromatically sensitized and contains 20 g of 1- (4-phemoxy-3-sulfo-phenyl) -3-hepta decyl-pyrazolone-5 per kg of emulsion as a purple coupler.

On this high-resolution, fine-grained, color-coupler-containing silver halide layer, the Hologram structure exposed as in Example 1.

Through the following processing step there will be: Latent B produced by the hologram exposure (in a negative purple dye image dtes HoIo gramms transformed.

2.75 g

2g 1.2 c

1. Development 8 minutes at 2O ⁰ C in the following bath:

N.N-diethyl-p-phenylcndiamine-

sulfate

Sodium hexametaphosphate

Hydroxylamine sulfate

Sodium sulfite 2 g

Potash 75 g

Potassium bromide 2.5 g

2. Soaking for 5 minutes.

3. Bleach 5 minutes in the following bath:

Potassium ferricyanate 42 g ¹ p

Potassium bromide 12g

Disodium phosphate fig

Sodium hexametaphosphate 6 g

Monopotassium Phosphate 16g

4. Soaking for 5 minutes.

5. Fixation for 5 minutes in the following bath:

Ammonium thiosulfate 150 g

Sodium solution for 10 g

6. Soaking 10 minutes.

7. Drying.

(All quantities refer to 1 liter.)

Example 3

A photographic material is used, consisting of a silver bromide iodide gelatin layer with 5 mol percent iodide content and an average grain size of 0.05 μm and a narrow grain size distribution. The mean square spread of the size distribution is ~ 0.03 | im. The packing density is above 0.3 g of silver per cm ^{: 1} . The layer is orthochromatically sensitized.

On this high-resolution, fine-grain silver halide layer the hologram structure is exposed as in Example 1.

The processing procedure described below makes this possible through the hologram exposure The latent image generated is first transformed into a silver image, the remaining halogen silver into a Transferred the color image and then removed the silver image. This way it becomes a positive generated purple color image of the hologram. The difference from Examples 1 and 2 is here however worked with an argon laser.

1. First development 18 minutes at 20 ° C in the following bath:

Sodium hecametaphosphate 2 g

p-methylaminophenol 3 g

Sodium sulfite 50 g

Hydroquinone 6 g

Sodium carbonate 40 g

Potassium rhodanide (50% solution) .. 5 ml

Potassium bromide 2 g

Potassium iodide (0.1% solution) 6 ml

2nd stop bath 4 minutes:

Sodium acetate with glacial acetic acid

pH 5.2 brought 30 g

3. Soaking 10 minutes.

4. Second exposure 3000 lux 2 minutes.

5. Color development for 14 minutes at 20 ° C in the following bath:

Sodium hexametaphosphate 2 g

Sodium sulfite 5 g

N.N-diethyl-p-phenylene diamine sulfate 5 g

Hydroxylamine sulfate 1.2 g

Potash 75 g

Potassium bromide 2 g

Ethylenediamine (50 °, .ig) 16 ml

2-cyanoacetyl coumarone Ig

6. Soaking for 20 minutes.

7. Bleach 5 minutes in the following bath:

Potassium ferricyanide 100 g

Potassium bromide 20 g

Disodium Phosphate (set to

pH 5.2)! "12 g

8. Soaking for 5 minutes.

9. Fixation for 5 minutes in the following bath:

Sodium hexametaphosphate Ig

Borax 15g

Sodium sulfite 10g

Sodium thiosulfate 200 c

10. Soaking for 15 minutes.

11. Drying.

Example 4

A photographic material consisting of a silver bromide iodide gelatin layer with 9 mol percent iodide content and an average grain size of 0.05 μm and a narrow grain size distribution is used. The mean square spread of the size distribution is ~ 0.03 μτη. The packing density of the layer is above 0.3 {silver per cm ³ . The layer is sensitized to blue light and contains 20 g of 4-stearoylamidobenzoxyacet-3.5-carboxyanilide per kg of emulsion as a yellow coupler.

It is exposed as described in Example 3 effect is here the blue line of the argon laser, the latent image formed by the Hologrammbelichtuni is first converts ver to a silver image by the hereinafter described processing operation, converted the residual silver halide in eil color image and the silver image anschließenc removed. This way it becomes a positive yellow

Color image of the hologram generated

1. First development 18 minutes at 20 ⁰ C in the fol lowing bath

Sodium hexametaphosphate 2 g

p-methylaminophenol 3 g

Sodium sulfite 50 g Hydroquinone 6 g

609 641/73

Sodium carbonate 40 g

Potassium rhodanide (50% solution) .. 5 ml

Potassium bromide 2 g

Potassium iodide (0.1% solution) .... 6 ml

2nd stop bath 4 minutes:

Sodium acetate with glacial acetic acid

pH 5.2 brought 30 g

3. Soaking 10 minutes.

4. Second exposure 3000 lux 2 minutes.

5. Color development for 14 minutes at 20 ° C in the following bath:

Sodium hexametaphosphate 2 g

Ν, Ν-diethyl p-phenylenediamine sulfate 5 g

Hydroxylamine sulfate 1.2 g

Potash 75 g

Potassium bromide 2 g

Ethylenediamine (50%) 16 ml

6. Soaking for 20 minutes.

7. Bleach 5 minutes in the following bath:

Potassium ferricyanide 100 g

Potassium bromide 20 g

Disodium Phosphate (set to

pH 5.2) 12 g

8. Soaking for 5 minutes.

9. Fixation for 5 minutes in the following bath:

Sodium hexametaphosphate Ig

Borax 15g

Sodium sulfite 10g

Sodium thiosulfate 200 g

10. Soaking for 15 minutes.

11. Drying.

For this purpose 2 sheets of drawings

Claims (6)

Patent claims: 1. Transmission hologram reconstructable with white light, characterized, that the information-carrying structure consists of a dye that is within of the visible wavelength range an absorption band lying in a narrow spectral range having. 2. Hologram according to claim 1, characterized in that that the information-carrying structure consists of a dye, its Refractive index shows the highest possible dispersion. 3. Hologram according to claim 1, characterized in that the difference in the refractive indices of the dye and de .. binder, in in which the dye is embedded. if possible is great. 4. Hologram according to claim 1, characterized in that that the dispersion curve of the dye odor as narrow as possible a maximum Has a minimum in the visible area. 5. Hologram according to claim 1, characterized in that that the dye has an absorption maximum with the steepest possible flanks and lower Width owns. 6. Process for the production of transmission holograms according to one of the 3 " Proverbs 1 to 5 by imagewise exposure of a light-sensitive photographic silver halide emulsion layer with the coherent radiation reflected from the object and simultaneous uniform exposure with the coherent Radiation and subsequent photographic processing of the exposed photographic Layer, characterized in that the colored photographic hologram by a t'arbende Development is generated.