US2136303A - Colored screen for stereoscopic projections - Google Patents

Description

L. LUMIRE COLORED SCREEN FOR STEREOSCOPIC PROJECTIONS Filed DeC. 17, 1935 Nov. 8, 1938.

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Patented Nov. 8, 1938 iSATENT OFFICE COLORED SCREEN nonis'rismioscorlo` raomcrlons Louis Lumire, Neuilly-sur-Seine, France Application December 17, 1935,l Serial No. 54,928 In France November 22, 1932 Claims.

Among the various solutions that have been proposed to the problem of producing stereoscopic images by projection on a screen, only one seems to have been put into practice to a certain 5 extent. This solution, which was exposed by dAlmeida in a paper dated 1858 (C. R. ac. des Sciences, t. XLVII, p. 337) and which was then claimed to have been disclosed five years earlier by Rollmann (Poggendorif Annalen IXC, 1853,

p. 185) consists in making use of red and green rays for projecting two respective images of a stereoscopic couple and also for impressing these images on the two eyes respectively (for instance by means of screens). But this method has the very serious drawback that it produces an intolerable fatigue of the eyes, due to the action on each of them of diierent rays which exert very different actions thereon.

It has indeed been proposed to employ other couples of complementary colored screens, but

none of these solutions of the problem ensures the equality of the amounts of luminousenergy received by the two eyes respectively.

The object of the present invention is to provide a couple of screens for use according to the method above referred to which obviate the y drawbacks above mentioned.

To this effect, the screens according to my invention are so colored that both of them allow red and green rays to pass therethrough but with different wave lengths so as to equalize the amounts of luminous energy received by the two eyes respectively whilev performing the desired discriminating action.

Examples of my invention will be hereinafter described with reference to the accompanying drawing, given merely by way of example and in which:

Fig. 1 shows a curve, which will be hereinafter called curve of sensations, serving to graphically illustrate an essential feature of the present invention.

Fig. 2 is a diagrammatic view of the screens according to the present invention, as mounted on spectacles;

Fig. 3 is a diagrammatic sectional view of a screen according to the present invention;

Fig. 4 is a similar view of a composite screen accordingto the present invention;

Fig. 5 is a sectional view on the line 5-5 of Fig. 2, with the screen shown in elevation.

In the curve of sensations, as shown by Fig. 1, the wave-lengths have been plotted in abscissas, while the ordinates correspond to the s ratio of the visual effect and of the caloriflc eect of the rays. 'I'his curve, which is well known in photometry, is based on the works of Gibson and Tyndall, and it reproduces the speciiic curve given in No. 475 of the Scientic papers of the Bureau of Standards in 1923, and 5 adopted by the International Commission on Illumination, in 1924.

According to my invention, in order to do away with the fatigue resulting from the perception by the eyes of colored rays as diierent l0 as red and green rays respectively, the screens placed in front of the eyes of a spectator (in the form of spectacles or eye-glasses) and which will be respectively the same as those placed across the path of travel of the light rays that l5 project the two images of the stereoscopic couple must comply with the .following requirements:

(a) both of them must allow red and green rays to pass therethrough but with diiferent "20 wave lengths, and

(b) their respective regions of transparency must correspond to approximately equal portions of the area limited between the curve of sensations and the axis of abscissas. 25

In order to comply with these conditions, one of the screens should have a transparency as great as possible for the region npp'n ranging betweent }.=550mp. and A=640m and the other one should permit the passage of both rays cor- 30 responding to the region mun' ranging between A=640mp and the extreme visible red on the one hand and rays corresponding to the region pqp' ranging between )\=550mp and the extreme visible violet lon the other hand. 35

It results from this choice that the whole luminous energy received by each of the eyes is the same and that, notwithstanding the apparent colors of the screens are diierent, nevertheless both of them will allow red and green i0 rays (which are those which have the most different and marked action on the eyes) to pass therethrough.

In Fig. 2, I have shown, by way of example, spectacles tted with screens r and Z according to the present invention.

I will for instance employ for the screen intended for the left projecting light beam and for the left eye a gelatinized glass in which the gelatin 50 is colored with a mixture of naphtol green, eosin and tartrazin, the concentrations of the solutions and the periods of time for which they are allowed to act being so chosen that the absorption spectrum above stated may be obtaned. In Fig. 3,

I have shown such a screen, 3 being the glass support and 4 the layer of colored gelatin.

In a likewise manner, the screen for the right projecting light beam and the right eye will be similarly obtained, but by superposing for instance a gelatinized glass in which the gelatin ls colored with a solution of cyanol blue upon a second glass colored by means of a solution of saccharein of diethylmetamidophenol (because,

as one of these coloring matters is an acid and the other one is a base, they combine with each other and form a precipitate when they are mixed together) and by adjusting, as for the screen corresponding to the left eye, the concentrationsof the solutions and the periods of time for which they are allowed to act in such manner that the optical absorption of the whole of the two glasses `may be complementary to that of the screen corresponding to that -of said left eye. In Fig. 4, I have shown such a composite screen, 3' and 3" being the glass supports and 4' and 4" the layers of colored gelatin.

' The gelatinized glasses that form the screens according to the present invention can be prepared in the well known manner which consists in placing these glasses, after cleaning them :as

perfectly as possible, on a plate of marble the surface of which is perfectly horizontal, -and in .pouring on said glasses a gelatin solution in water of 8 or 10%, at the rate of 10 cubic centimeters per square decimeter. The gelatin that is employed may be of any kind whatever, provided.

that it is free from fatty matters, such as being easily found on the market.

The glasses thus covered with gelatin are caused to dry as soon as the gelatin has taken a jelly-like consistency, care being taken that dust cannot reach them.

In order to obtain dyes complying with the requirements above mentioned, I may, for instance, pour onto the dried gelatinized surfaces of glasses treated as above explained the coloring solutions the formulas of which are hereinafter given, and after a suitable duration of contact, these surfaces are wiped with a very line piece of linen, and finally they are allowed to dry.

The following formulas,.given' merely by way of example, permit of obtaining the desired result.

First glass.-So1ution consisting of the following mixture:

Solution of tartrazine of 2% cm.3 20

gelatin Solution of eosin of 2% cm.3 14 Solution of naphtol green of 5%, cm.3 16.

the duration of impregnationanging between Third `Masa- Solution of saccharein of diethyl-V -metamidophenol of 5%; duration of contact: about 30 seconds.

In order to obtain the rst of thel two nished screens, I superimpose upon Ithe first glass a colorless transparent glass 3a (Fig. 3) which is glued by means lof Canada balsam in such manner as to protect the layer of colored gelatin, thus enclosed between two glasses.

The second screen will be obtained by gluing the second and third glasses against each other, gelatin against gelatin, by' means of Canada balsam.

Screens made as just above explained comply with the conditions above stated, one of them allowing only the rays ofv a wave length ranging between 550 and 640 microns to pass therethrough and the other screen absorbing these rays and allowing the remainder of the spectrum to pass therethrough. l

In a modification, the two complementary screens are obtained by spreading upon the dry gelatinized surfaces of glasses treated as above explained, the following coloring compositions:

First screen-Solution of 2% of bright blue for wools FFR of the I. G. Farbenindustrie. This coloring matter, which should preferably be employed in the pure state, was discovered recently and is not described in Schultz Tables.

Second scream-Solution containing simultaneously 2% of pure naphtol green (No. 5 of Schultz Table of 1931) and 3% of Poirier E Orange (No. 189 of the 1931 Schultz Table). This last solution is relatively weak so as to avoid crystallizations when it is being used. If a single application is notJ sufficient, two successive applications should be made.

The solvent that is used for preparing these two coloring solutions is preferably a mordant for gelatin and it may, for instance, consist of a mixture of equal amounts of acetic acid, water and alcohol.

The coloring matters above stated have been indicated merely by way of example and it does not matter if the screens are inversed, provided that each eye is provided with a screen of the same color as that interposed across the light beam which serves to project the image that said eye must alone see.

The limits above stated for the regions of the spectrum that are to be absorbed can be slightly varied according to the coloring matters that are employed, the limits of absorption of which are always more or less blurredand also according to the composition of the light that is employed for the projection.

'I'he conditions above stated, which characterize the present invention, can also be applied in the case of anaglyphs (Ducos duHauron, United States Patent No. 544,666) that isv to say in the case in which the images of the stereoscopic couple are projected one on the other by means of white light, the images being themselves colored as are the screens in the case above explained, said images being looked at through screens placed before the eyes and having the same regions of transparencey, but respectively complementary, that is to say inversed for each of the eyes as far as the chromatic absorption is concerned.

The couples of chromatic screens that have been described above may also be applied to the projection of cinematographic lms the surface of which is corrugated.

Said films are projected by means of the same optical system that has been used for recording the pictures, but by providing it with the screens above described. s

When devising spectacles provided with complementary screens as above described, it is necessary to protect as much as possible the eyes of the spectators against reflection by the frame of the spectacles of the light rays from the image that is projected. For this purpose, it is advantageous to make use, for the spectacle, of black and matt frames avoiding these detrimental reflections and, furthermore, to provide these frames with anges or projections capable of stopping the light rays. In Fig. 5, which is a section on the line V-V of Fig. 2 with the screen r shown in elevation, frame I, which is of dark shade andprefaiseos erably ci a matt material, is provided, on its external part, with a protecting iiange 2.

The present application is a continuation in part of my copending application iiled October 26, 1933, Ser. No. 695,364.

What I claim is:-

i. A pair of complementary color screens for use in filtering the two images of a stereoscopic couple, one of said screens having a transparency restricted to a hand of wave lengths of the spectrum ranging from approximately 550 to 640 `nillimicrons; andthe other of said screens having a transparency restricted to two bands of wave lengths of the spectrum, one band ranging approximately from 400 to 550 millimicrons, and the other bandv ranging approximately from 640 to 700 millimicrons, and means for supporting said screens with their axes laterally spaced for passing the light of the first mentioned band to oneV selected position and the light ofthe other two bands to another selected position.

2. A pair of complementary color screens for use in illtering the two images of a stereoscopic couple, one of said screens having a transparency restricted to a band of wave lengths beginning with a' portion of the green-yellow of the spectrum at one edge and continuing throughy a portion of the orange-red at the other edge; and

the other of said screens having a transparency restricted to two distinct bands of wave lengths, the one vband extending from the extreme visible violet and continuing through the Wave lengths of green-yellow not passed by said rst; mentioned screen, the other band extending from the extreme visible red and continuing through the wave lengths of orange-red not passed by said first mentioned band, and means for supporting said screens with their axes laterally spaced for passing the light of the rst mentioned band to one selected position and the light of the other two bands to another selected position.

3. A pair of complementary color screens according to claim 2 in which one screen consists of a plate of a transparent material having a color composed of a mixture of a ve percent solution of naphthol green, a two percent solution of eosin and a two percent solution or tartrazine; and in which the other oi said screens consists of a pair oi superposed plates of trans-v parent material, one plate having a color composed of a one percent solution of cyanol blue and the other plate having a color composed of a ve perecent solution of saccharein of diethylmetamidophenol.

Li. A pair of complementary color screens according to claim 2 in which one screen consists of a plate of a transparent material having a color composed of a two percent solution of bright blue for wools FFR of the I. G. Farbenindustrie, and the other of said screens consisting of a plate of transparent material having a color composed of a solution containing two percent pure naphthol green and three percent Poirer II orange.

5. A device for use in connection with stereoscopic projections which comprises, in combination, a couple of transparent `screens each colored to allow both red and green rays to pass therethrough1 but with diierent Wave lengths, the respective absorptions of said screens corresponding to equal portions of the area limited between the curve of sensations and the axis of abscissae of said curve, and means for holding said screens across the respective paths Aof the light beams corresponding to the images on the projection screen, said lastmentoned means consisting of a spectacle frame for holding said first mentioned screens, said frame being made of a dark and matt material and forming a ange extending frontwardly around each of said rst mentioned screens.

LoUIs LUMIERE.

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