US1887872A - Lensic screen - Google Patents

Description

Nov. 15, 1932. v C, ERNST 1,887,872

LENSIC SCREEN Filed June 18. 1927 2 Sheets-.Sheet 1 v. c. ERNST 1,887,872

LENS IC SCREEN Filed June 18. 1927 2`sneets-sheet 2 Patented Nov. l5,

UNITED STATES PATENT; 'OFFICE vrcron c. maar, or LAxEwoon, omo, assIoNon 'ro FULL-TONE rnocEss comm,

' or CLEVELAND, omo

LENSIC SCREEN Application nled June 18, 1927. Serial No. 199,842.

` My invention pertains to a lensic screen and more particularly to` an integral association of a plurality of microscopic lenses regularly arranged in partially intersecting relationship within predetermined limits.

The disclosure herein constitutes an advanta eous development of the lensic screen, descri ed and claimed in my Pat. No. 1,849,036, issued March 8, 1932.

I have discovered that in order to obtain an adequately true tonal reproduction of what I term a high light object, an overlapping recordation of black dots on the negative should be achieved or conversely, those microscopic areas which are to appear White on the negative and therefore black on the print from a zinc or copper plate should comprehend areas which, even though microscopic, 'are quite small as possible. I have achieved that imroving result by arranging the arcuate sur- Paces of the lens elements so as apparently to intersect to a predetermined extent. It is not desired thus to eliminate more of an individual lens curvature than is necessary to cause recordation of lapped dot areas. Actually, each lens is characterized by a plurality of truncations which as a developed plan are segmental. Exempliiedly, planoconvex lensic units of spherical contour are employed for convergent refraction. Such a. lensic screen is universally adapted for use with or without adjustment for size of the aperture to the lens of the camera.

One form of my invention is a regularly repeated quadruple rectangular formation with the four lens centers demarking corners of a square. Each lens unit has four circumferentially arranged and equi-spaced truncations, the truncation defining planes of one lens being juxtaposed, indeed, coinciding with as many similar iiat planes on four other surrounding lenses. As so arranged, each group of four lenses encloses a quadrilateral recess of which the bottom is fiat and of which the four sides coincide with opposed portions of distinct spherical surfaces. Such recessed bottoms will allow light rays to pass parallelly therethrough.

No plano-convex or plano-concave lens of a as geometrically' lensic screen canbe effective to record dots of its full size, because the thickness of the lensjoining stock necessaril spaces any sensitized surface, which is to per orm its function in association therewith, from the ilat surfaces of the group of lenses. That is to say, the required thickness of the transparent lensjoining material so far displaces the sensitized surface as to effect light ra convergence and to record distinct dots, ut the dots cannot possibly-be the same size, (have the same diameterkas the lenses. However, the unifying stock between lens conformations theoretically means some undesirable parallel rays therethrough and that my arrangement minimizes. During actual printing the transparent areas are so minute that the corresponding unetched part of the metal plate either does not receive or does not retain an ink coating, therefore, prints uncertainly or negligibly. By proper exposure, I can infallibly eliminate black printing in reproducing pure white areas or so called high high lights.

The individual lenses may be brought even more closely together by an arrangement of groups of three, which enclose triangular recesses of correspondingly smaller area because the centers of three lenses, which slightly intersect or functionally lap in a circular progression, may be brought more closely'together so as actually to define the corners of a triangle in some given plane.

The method of use consists in first obtaining a photographic continuous-tone negative of the object or picture which it is desired to reproduce. To realize an economy of manufacture and convenience, the sensitized emulsion may be deposited on the flat side of the lensic screen and the continuous-tone negative of the obj ect or photograph becomes preserved on the emulsion coating of the screen.l

If a negative is already had it is placed in contactual juxtaposition to one side of a lensic screen. Then, in contact printing, light rays are projected toward the plate and intercepted by the lens conformations of the screen to be refracted thereby through the negative image which is at the opposite side of the lensic screen, or, in projection printing (enlarging or reducing) the light rays are allowed first to pass through the negative photographic image and then through the lensic screen to the light-sensitized surface.

During enlarging or reducing projection as distinguished from contact printing, the operation may be accomplished without altering dot sizes by separating the screen and placing it ahead of the recording surface for the varisized'image.

.It is to be realized that the scope of my invention comprehends many equivalent methods and constructions. The showing of the drawings and the particular description are merely specific exempliiications of a plurality of successful mechanical embodiments, arrangements and performances.

Figure 1 is a fragmentary plan View,

' (greatly enlarged), of a half-tone lensic screen embodying the principles of my invention and showing individual lens elements, groups of four of which have their centers define a square figure.

Figure 2 is a cross-section on line 2-2 of Figure 1.

Figure 3 is a cross-section on line 3-3 of Figure 1.

Figure 4 is a correspondingly enlarged diagrammatic representation of the result obtained by light projection from a half-tone object through my lensic screen to reproduce the half-tone object on a sensitized emulsion by rojection of half-tone dots.

`igure 5 is a plan view showing the spaced relation of the half-tone dots.

Figure 6 is a view like Figure 4 showing the reproduction of a shadow object resulting in shadow dots.

Figure 7 is a plan view showing the smaller shadow dots.

Figure 8 is a view like Figures 4 and 6 showing the reproduction of a White or high light object to result in negative dots of maximum size.

Figure 9 is a plan view of a negative in consequence of exposure according to Figure 8.

Figures 10 and 11 are a plan and a sectional vievs1 respectively of a complementary screen forming die.

Figure 12 is a diagrammatic illustration of the final projection of lightrays through my lensic screen, thence through the negative image to the emulsion coatingY on a metal plate.

Figure 13 is a greatly enlarged fragmentary plan view of a modified arrangement of lens elements.

Figure 14 is a section on line 14.--14 of Figure 13.

Figure l5 is a diagrammatic representation shoWng projecton from a half-tone object through my modified form of lensic screen to an emulsion surface.

Figure 16 is a plan view'of the negative 0btained according to Figure 15.

Figure 17 is a view corresponding to Figure 15 disclosing the result of light pro'ection from a white or high light object through a lensic screen also having the design shown in Figure 13.

Figure 18 is a. plan view of the negative obtained according to Figure y17.

A flexible lensic screen 1 has embossed thereon a multitude of plano-convex lens elements 2 of microscopic size. As shown on sheet 1 the lenses have substantially parallel optical axes and groups of four are rectangularlyl arranged. i'

A distinguishin feature is that each lens 2 is truncated, in act, has its edge fashioned with four circumferentially equi-spaced truncations, the truncation-determining planes of which are segments as appears in a developed plan View. Moreover, the convex spherical surfaces of the lenses 2 intersect, each with similar surfaces of four surrounding lenses, so that each pair of adjacent lenses in each of two relatively transverse directions have their truncation-defining planes coinciding at 3. By this arrangement, regularly spaced intervening recesses 4 are provided. T he bottoms of the recesses 4 will be substantially fiat, as shown in Figure 3, Whereas the four sides of the recesses will be defined by as many portions of the spherical surfaces of four distinct enveloping lenses. It is to be understood, that the lensic screen in its entirety is integral, bein molded, or embossed by a complementary gie. The rectangular spacing of the lenses determines the quadrilateral mutilation or truncation, because it is preferable to have the lens centers uniformly as close as possible without excess or needless truncation.

Figures 4 and 5 show the result obtained in reproducing a half-tone object 5, which may also be considered as an intermediary color tone, for instance, gray. The light rays from the object 5 are projected through the lenses 2 to a film or plate 6 having its receiving side coated with an appropriate light sensitive emulsion 7 (which may be a coating supplied to the smooth side of the screen 1) to produce black circular dots 8 of a predetermined size, but smaller in diameter than the diameter of the lenses 2. Regularly interspersed with relation to the dots 8 are other fainter quadrilateral dots 9, which are the result of the passage of parallel rays of light through the recesses 4. The dots 9 are, in fact, defined by equi-sized concave sides. Attention is directed to the fact that four of the dots 8 enclose a centrally located dot 9 and that such a pattern of five dots, of which annular intersecting areas 10 are the determinants, is repeated according to the size of the lensic screen.

It is interpolated that the bottom of the recesses 4 might be coated with an opaque substance, (as and for the reason disclosed in my earlier application), in which event the relatively lighter half-tone four sided areas 9 would notv appear. Also, the recesses 4 in the lensic screen 1 c orres ond to islands or rojections in a forming ie and finally to ess pronounced dots on the zinc or copper plate, in consequence of projection of light from any but a totally black object or surface.

Figures 6 and 7 correspond to Figures 4 and 5 except in showing the difference in rojected result from a shadow or black object 11, which results in the recordation on the emulsion 7 a pattern of only four much smaller circular dots 12 having, however, the same spacing of centers as in the case of the dotsr 8. In projecting from a shadow or black object 11 there will be no recordation of fainter dots equivalent to the quadrilateral dots 9, because the light rays are not intense enough to record on dispersed passage parallelly through the recesses 4, wherefore the entire remaining area 13 will be substantially unaffected by exposure to light.

Figures 8 and 9 illustrate the projection performance from a white or high light ob- A ject 14, which will result in each lens 2 recording a circular dot 15 of maximum size and yet of smaller diameter than the complete diameter of each lens and smaller to such an extent as is indicated by the converging lines 16 in Figure 8 and by the White and senarated arcuate sections 17 in Figure 9. The arcuate sections 17 merge in groups of four to enclose and define the fainter quadrilateral dots 18. Comparative scrutiny of Figure 9 with Figures 5 and 7 will reveal the attainment according to my invention of very much smaller white areas, composed of the arcuate sections 17, than are the unified white areas 10 and 13 in Figures 5 and 7 respectively. Since Figures 5, 7 and 9 are negative images it will be evident that positive prints obtained therefrom will disclose black areas corresponding to the white areas 10, 13 and 17. Evidently also, my discovery permits of attainment of what I term high light dots of minimum feasible area. In fact, each high light dot, as finally printed, will comprise only four of the arcuate sections 17 and thereafter be so insignificant, even when discernible under a magnifying glass, as to be of negligible effect and therefore insure the attainment of approximately absolute high lights in the printed impression from a metal plate.

As disclosed in my parent application, earlier identified, my lensic screen may be manufactured in numerous Wavs, perhaps most conveniently by embossing by means of a complementary die. disclosed in Figures 10 and 11, from inspection of which it may be observed that the die is fashioned with ypart spherical surfaced recesses'19. which are complementary to the convex surfaces on the lens 2 and likewise fashioned with projections 20, which are complementary to the recesses 4. A fter obtaining, say, the negative 21, (see Figure 12), disclosed in Figure 9, supposedly on the rear side of the lensic screen 1, the emulsion s urface 22 on a metal late 23 is placed against the negative 21 andp light pro- .jected through the screen 1, through the image 21 truly to record the latter with patterns including those found in Figures 5, 7 and 9 accordin to the infinite number of color tones which may be present in the image. It should also be understood thaft my lensic screen is adapted for projection use with an enlarging and reducing camera in which case the negative would be mounted in the camera and its image projected thereby.

In Figures 13 and 14 a modified arrangement of. individual lens elements 24 is illustrated, there being three instead of four around any particular central point and six around, so as contiguously t0 enclose, any particular lens element. This modified arrangement establishes each group or repeated pattern of three lenses with centers as the determinants of a triangle. The lenses 24 are each fashioned with six truncations 25 coinciding with a corresponding truncation of an adjacent lens, and the closer relationship of the lenses 24 permits still smaller intervening recesses 26, the bottoms of which are of triangular shape.

Figures 15 and 16 show the result obtained in reproducing a half-tone object 27, from which light rays are projected through the lenses 24 to a iilm or plate 28 having its near side supplied with an emulsion 29 to produce separated dots 30. Around each of the dots 30 are fainter three sided dots 31, caused by the passage of parallel light rays through the bottoms of the recesses 26. In fact, the dots 31 are defined by three concave sides of equal dimension. That portion 32 of the emulsion coating, which is not effected by light, appears white in Figure 16.

Figures 17 and 18 correspond to the two preceding figures, but show the different projected result from a high light object 33 to involve the record ation of circular dots 34 of the greatest possible size with consideration of the thickness of the unifying lensic screen material below the lens elements proper and in consequence of the convergence represented by the dotted-line 35, or by the white arcuate sections 36, which merge so that three thereof enclose one of thefaintei dots 37. It will be apparent from inspection of Figure 18 that the white areas 36 are exceedingly small and because they are white on the negative they will be black on the positive print image ultimately reproduced on the zinc or copper plate. Therefore, the black areas on the print theoretically will be so extremely minute even microscopically as to be ahnost negligible. In practice they may be entirely eliminated, as heretofore explained, and permit realization of what is known in the trade as high high lights.

I claim:

1. A lensic screen of transparent material comprising plano-convex lenses of microscopic size each of said lenses being fashioned with a series of separated edge truncatlons of which pairs on adjacent lenses coincide whereby to eliminate possibility of any parallel rays passing between said truncated coinciding edges.

2. A screen comprising a sheet of transparent material the front side of which is provided with microscopic convex lenses having equi-spaced,. truncated ed es, the truncations of adjacent lenses abutting each other to form regularly-spaced, fiat-bottomed, intervening recesses; whereby, collimated light striking the front side of the sheet would appear at the opposite side of the sheet as overlapping beams of light.

3. A new article of manufacture-comprising a sheet of transparent material formed on one side with a plurality of integral lenses having convex surfaces with pairs of separated portions intersecting each with a pair of other convex surfaces whereby to enclose a small plane figure defined by the bottom lines of the portions of said convex surfaces which are alternately between their pairs of intersecting portions respectively.

4. As a new article of manufacture, a lensic screen of transparent material comprising a plurality of integral lenses each fashioned with a plurality of truncations the deining planes of which coincide in pairs including one of an adjacent lens, said lenses being arranged about a central point with reference to their axes and which point lies in a flat intervening recess.

5. As a new article of manufacture for use in the art of producing half-tones, a lensic screen of transparent material comprising plano-convex lenses of microscopic size, each of said lenses being fashioned with a predetermined number of equi-spaced truncated edges which are ditined by plane geometric figures, said plane geometric truncation tigures being alike and each defined by curved and straight lines coinciding in pairs with corresponding lines of an adjacent lens, said lenses being of such size and with their centers so spaced as to provide Hat-bottomed intervening recesses defined by convex lens surfaces of a surrounding group of lenses.

6. A lensic screen of transparent material comprising plano-convex lenses circularly arranged, each of said lenses being bordered by alternately arranged spherical surfaces and axially parallel truncations, truncation planes of adjacent pairs of said lenses coinciding.

Signed by me, this 14 day of June, 1927.

VICTOR C. ERNST.

Images