FI63118B - LAOGBLAENDANDE SAMLINGSLINS FOER EN OH-PROJEKTOR - Google Patents

Description

Γβΐ ADVERTISING PUBLICATION.

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Patent * OCh registerstyrelten 7 AntMcan uttagd oeh utLskrtftM published 31.12.82

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03.03.75 USA (US) U99138, 55UU17 (71) Minnesota Mining and Manufacturing Company, 3M Center, Saint Paul,

Minnesota 55101, USA (72) Raymond Harry Anderson, Saint Paul, Minnesota, Gregory Scott Lever, Stillwater, Minnesota, Terrence Michael Conder, Saint Paul, Minnesota, Donald John Newman, Saint Paul, Minnesota, USA (US) ( 7U) Oy Kolster Ab (5U) Overhead low-gloss condenser lens - Lägbländande sam-lingslins för en OH-projektor

One particularly useful overhead projector, outlined in U.S. Patent No. 3,126,786, comprises an optically aligned transparent, horizontal table on which transparencies are placed, an intense light source below it, a stepped lens structure, and a stepped lens structure comprising two annular steps. a projection lens located above the table. The tiered lens structure acts as a condenser lens and the projection lens acts to provide an image of the table and the film placed on it on the display plane. The person using the projector usually stands next to or behind the projector so that he or she can easily change transparencies, point to points of interest, or mark them.

One problem with overhead projectors of the type described is that the user sees a centered glare area when looking at a film or exposed table. This glare arises because a small portion of the light passing through the stepped 2 63118 lens structure is not directed. Figure 1 of the accompanying drawing (showing a schematic cross-sectional view of an annular, stepped lens structure along a plane extending through the lens including the optical axis of the lens) shows the path of the directed and non-directed light beams. Each annular step or ridge 13 of the annular, stepped lenses comprises a partially conical descending surface 14, an ascending surface 15 and an outer and inner edges 16 and 17, at which the descending surface and the adjacent ascending surface are connected. If the light beam 18 is not reflected and does not strike the rising surface, it is said to be guided, and the descending surfaces are shaped so as to refract all the directed light beams towards a substantially common focal point and through the projection lenses.

In the plane shown in Figure 1, examples of non-directed light beams as light beams 20, 21 and 22 have been identified. The light beams 20 and 21 are not guided because they are reflected and do not refract at the interface between the air and the lens material. The light beam 22 is not guided because it bends at the edge 17. Because the overhead projector uses a relatively small illumination source, all non-directional (as well as directed) light beams are nearly flush with the optical axis of the stepped lenses 11 and 12 in readable planes extending radially from the optical axis. The non-directed light rays are thus located in planes extending radially in all directions from the optical axis of the lenses 11 and 12.

When the projector user looks at the projector table 24 or the film on top of it, his eye "E" receives a dazzling light emanating from the propeller-shaped area 28. No matter where the user stands next to the table, his eye is level with the optical axis and he sees the uncontrolled light glare.

The low-glare, staggered focusing lens of the overhead projector according to the present invention, comprising a plurality of straight, staggered lenses having a cylindrical lens effect, the cylindrical axes of the pairs of lenses being oblique or perpendicular to each other, is characterized in that the staggered so that the cylindrical axis of each lens forms an angle of 55 to 65 ° with the cylindrical axis of the other two lenses.

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Figures 3 and 4 show how mitigation of disturbing glare is achieved. Figure 3 shows a schematic view of a single, linear staggered lens 29 with parallel, rectilinear ridges and grooves instead of the annular ridges and grooves previously used in Fresnel lenses of overhead projectors, and having a cylindrical axis 30 extending parallel to the center of the ridge 30 through. The lens 29 is capable of concentrating the light from the point source 31 into a "focal line" 32. If the plane 33 were positioned parallel to the lens, non-directed light rays, e.g., a light beam 34, emanating from the surface of the lens 29 would form a light strip 35 along the plane. The width of the strip 35 would be the same as the length of the focal line 32 and would extend laterally on either side of the focal line 32.

Figure 4 shows two rectangularly oriented, rectilinear, stepped lenses 37 and 38 positioned parallel to and aligned with a light source 39 to concentrate light collected from the source at a focal point 40, which is an image of the light source 39.

If the plane 41 were placed parallel to the lenses, the viewer would see two bright bands 42 and 43 formed by the non-directed light. Each of the bands 42 and 43 is provided by a different lens 37 and 38, and the band provided by each lens narrows because the other lens acts to focus uncontrolled beams. Each strip corresponds approximately in width to the size of the focal point 40 on the paper plane 41. Some of the unguided light falls inside the quadrants between the lanes 42 and 43, but this light is not so intense as to disturb the user viewing the lens or projector table from the normal position E. In the preferred overhead projector of the invention, the lane width is about 4 cm on the focal plane or paper plane 41. As long as the user is on a normal salary and looking at the table from a point between the symmetry of the lenses or the cylindrical shafts, such as between shafts 44 and 45, and not in a direction perpendicular to the lens portion axis, he receives significantly less glare from the tiered lens structure.

The stepped condenser lens of the invention preferably includes at least four different rectilinear, stepped lenses, each of which comprises a smooth, flat surface and a surface with parallel ridges and grooves. The four lenses are generally oriented in pairs so that the axis of the second lens of the pair is substantially toward the axis of the second lens of the pair, and each pair is oriented so that the axes of the other pair are at an angle of 5-45 ° to the nearest axis of the other pair. . However, according to the invention, rectilinear, stepped lenses can also be arranged in other ways, e.g. as triple lenses, in which the axis of each lens forms an angle of about 60 ° with the axes of the other lenses.

(It is known that the use of crossed cylindrical lenses achieves the effect of a substantially spherical or spherical lens; see I. Pitman * in, London, Technical Optics, Louis E. Martin, p. 312 et seq. have previously used crossed, rectilinear, stepped lenses, see U.S. Patent No. 3,580,661 to Cooper, issued May 25, 1971, and also U.S. Patent No. 2,726,573 to Maloff, issued December 13, 1971. .1955 describing rear projection planes).

(However, none of these prior patents have proposed to alleviate the glare problem associated with annular, assembled lenses in overhead projectors by using cross-aligned, straight, staggered lenses. or other means of overcoming the glare problem, which are more expensive and reduce the amount of light passing through the condenser lens structure).

Other figures of the drawings may be summarized as follows: Figure 5 is a perspective view of a plotter according to the invention; Fig. 6 is a sectional view of the overhead projector of Fig. 5 taken along line 6-6 thereof; Fig. 7 is a fragmentary perspective view, partly in cross-section, of the overhead projector table and lens structure of Fig. 5; Fig. 8 is a top schematic view of two rectilinear, stepped lenses; Figures 9 and 10 are top schematic views of a structure comprising four rectilinear, stepped lenses; Fig. 11 is a top schematic view of a projector table in which the lens structure is formed by a three-part, rectilinear, stepped lens structure; 631 1 8 5 Fig. 12 is an enlarged, schematic perspective view of a section of the table and lens structure of Fig. 11 exploded; Figures 13 and 15 show top schematic views of different lens structures containing six lens parts? Fig. 14 shows an enlarged, schematic perspective view in cross-section of an alternative lens structure scattered in parts with six straight, stepped lens surfaces? Fig. 16 shows an enlarged, schematic cross-sectional view of another embodiment of a lens structure according to the invention; and Figures 17 and 18 show, respectively, a schematic view and an exploded view of the manufacture of glass lens laminates that can be used in the invention.

The overhead projector 45 of the invention shown in Figure 5 includes a base 46 and a projection lens 47 supported on the base by a rod 48. According to Figure 6, the base 46 includes side walls 50, a bottom wall 51, a projection lamp 52, a transparencies support surface or table 53 and a rectilinear stepped lens structure 54. Figure 6 also shows that the projection lens 47, commonly known as a "projection head", includes a pair of similar, simple, positive meniscus lenses 55,56 and a mirror 57.

The rectilinear, stepped lens structure 54, best seen in Figure 7, includes rectilinear, stepped lenses 59 and 60 supported between the flanges 62 and 63 of the frame portion 61. The frame part 61 also supports a table 53 on the flange 64. The rectilinear, stepped lenses are attached together in an airtight sealed structure so that no dust can penetrate between the lenses. The individual stepped lenses are often provided with flat areas along their edges and these areas are joined together, e.g., by solvent sealing, heat melting, or other suitable methods. Although each lens 59 and 60 has a rectangular outline, the cylindrical shafts of the lenses need not be parallel to the edges of the lenses.

The structure shown in Figure 7 is a useful, but preferred, rectilinear, assembled lens structure including more than two rectilinear, stepped lenses to reduce aberration problems associated with cross-positioned cylindrical lenses having a relatively large aperture. Figures 8 and 9 show the deflection effect of the crossed cylinders 63118 and the improvement achieved by using the four lenses. Fig. 8 is a top view of the dual lens structure 54 of Fig. 7 having cylindrical shafts 74 and 75. The light passing through the lens structure 54 within an area generally bounded by a curve 72 with four protrusions becomes centered within a relatively small area within a circular plane 73 (focal plane). located at a suitable distance above the lens structure). The light passing through the corners of the lens structure outside the curve 72 bends somewhat too much, so that it is reflected outside the circle 73 but inside the curve 76, which has four protrusions. For example, a beam of light passing through the lens structure at point 77 intersects the image plane at point 78. If corrective action is not taken, the image generally constrained by curve 76 may be too large to pass freely through the projection lens, causing some parts of the table projection to appear colored or dark.

Figure 9 shows the use of an alternative lens structure that includes two pairs of crossed, rectilinear, staggered lenses positioned to alleviate the deflection of the crossed cylinders. The cylindrical axis in each lens of the pair - 80 and 81, 82 and 83, respectively - is at a substantially right angle to the other axis of the pair. But the cylindrical axes of the lenses of the second pair form a theta angle (Θ) with the nearest axes of the lenses of the second pair, thus causing the regions of relatively high refraction to be located above the regions of relatively low refractive power. The light rays obtained by such an arrangement to a substantially common focal point pass through the lens structure within a curve which may be represented by curve 84. Curve 84 surrounds a larger area than curve 72 in Figure 8, has less deep projections and thus provides greater usable assembly area 85 for similar lenses. .

The angle Θ is preferably at least 5 ° to reduce the Moir6 patterns and at least 10 ° to obtain a much larger usable area 85. The best angle to enlarge the usable area 85 and reduce the Moir6 patterns would be 45 °. However, the 45 ° angle has one disadvantage in that the areas of low glare are smaller than would be desirable. The best value for the angle Θ can be selected so as to provide an acceptable range according to Fig. 10, which shows a view from above, as well as Fig. 9, of a four-part, rectilinear, stepped lens structure. A small light source (not shown) is located under the structure. From the source, light passes through the lens structure and is directed to a focal point within the area indicated by circle 86 at a spaced plane 87. Undirected light impinges on plane 87 within four bands 88,89,90 and 91 that vary slightly in width but are approximately as wide as the image circle 86.

Since the user's eyes are generally above the lens structure at a height approximately corresponding to the position of the image plane 87 and the image circle 86, the angles gamma (V) and oraeega (00) form areas hereinafter referred to as low glare areas within which the user's eyes are not in a significant amount of undirected light.

The best value for the angle Θ is between 25 ° and 35 ° to obtain a large enough useful area for the lens structure, to reduce Moird images, and to obtain small enough glare areas. The orientation of the cylindrical shafts of the lenses with respect to the outer contour of the lens structure can be changed without changing Θ in order to obtain a suitable orientation of the low glare areas.

Figures 11 and 12 show a three-lens condenser lens according to the invention. The three cylinder shafts 96,97 and 98 are positioned to intersect at substantially 60 ° angles when viewed from above, as shown in Figure 11. According to the exploded cross-sectional view of Figure 12, the lens structure comprises a cover plate 99 which can be used as a table and made of glass, polymethyl methacrylate or polycarbonate. It is attached at its edges to the edge region of the upper lens 100, the lens axis 96 of which is oriented perpendicular to the front and rear edges of the projector table. The lens 101 has an edge region and is sealed between the lens 100 and the third lens 102. The respective cylindrical shafts 97 and 98 of the lenses 101 and 102 are rotated relative to each other and to the shaft 96. It has been found that this triple lens is capable of providing a similar focal effect as annular, stepped lenses.

Figures 13 and 14 show a lens structure that can be used in an invention with two triple lenses. Six ridged surfaces are made, for five plates 110, 111, 112, 113 and 114; the plate 112 has linear ridges on both surfaces and both sides of the plate are referred to herein as a lens. Such a structure reduces the number of refractive surfaces in the lenses and thus reduces the losses caused by reflection on the 8 631 1 8 dividing surfaces. The surface with six ridges has cylindrical shafts 104,105,106, 107,108 and 109. The shafts 104,105 and 106 of the second three-lens are at an angle of 60 ° to each other; the axes 107, 108 and 109 of the second triple lens are at an angle of 60 ° to each other; and the axes of the two triple lenses are separated by a beta angle of about 10 ° (/ 3). This gives 50 ° low glare areas at the front corners of the table. In the lens structure of Figures 13 and 14, the smooth, flat top surface of the lens 110 can be utilized as a projector table. To protect the polymeric material from which the lens portion 110 can be made, a transparent and hard coating material 115 can be applied to the smooth top surface of the lens 110. This hard coating material may be, e.g., a fluoropolymer based on silicone, such as that sold by E.I. dePont deNemöurs, Wilmington, Delaware under the trade name "Abcite".

Figure 15 shows a six-lens lens structure suitable for use in the invention with three pairs of straight, stepped lenses. In each pair, the cylindrical shafts of the lenses are perpendicular to each other. The axes 117 and 118 of one pair are at an angle of 10-15 ° to the axes 121 and 122 of the other pair. The shafts 119 and 120 of the third pair are at an angle of 10-15 ° to the shafts 121 and 122 of the second pair. When the lens pairs are oriented as described, the angle range of the projector's low glare areas is 60-70 °.

Figure 16 shows a preferred embodiment of a condenser lens structure according to the invention. This structure uses two pairs of straight, stepped lenses combined to provide a similar cylindrical axis orientation to the orientation shown in Figure 10. However, in this construction, the upper lens 125 is provided with ridges and grooves in the central recess 126, thereby forming a cavity between these parts with a compatible lens 127 having a similar recess 128. Thin lenses 129 and 130, which form the other two lenses in the structure, can be placed in this cavity formed after the edge regions of the lenses 125 and 127 are joined together. The lenses are preferably formed with ridges and grooves so that the lenses 125 and 129 form an optical structure of the lens structure and the lenses 127 and 130 form a second optical pair. In this structure, the stepped surface with the ridges of the upper pair of lenses 125 and 129 is positioned toward the light source, and the stepped surfaces of the lenses 127 and 130 are on the sides away from the source of the plates.

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The lens structures used in the present invention have some of the preferred orientations of the lenses relative to each other and to the light source. However, this trend is not the only possible one, but the placement of the four-part lens structure can be changed. For example, if a four-lens structure has lenses 1,2,3 and 4, where 1 and form a second pair of rectangular lenses and 3 and 4 form a second pair, the lenses can be stacked in different orders, such as 1,2,3,4 or 1,3,2, 4. However, the position of the cylinder shaft does not change when the order of the lenses is changed.

As a practical embodiment of the invention, a usable projector was fabricated that included a condenser lens structure with four 4 mm thick polymethyl methacrylate plates, each with ridged, straight, stepped lens inserts on one surface. The cylindrical shafts of the four lenses were arranged substantially as shown in Fig. 10, so that the magnitude of the angle Θ was 30 ° and the angles A and B on each side of the center line of the table were 15 °. The lenses were similar to each other and approximately similar to the F 1.1 planar convex standard cylinder lens. The frequency of the ridges was 40 / cm. In the lower lenses the ridges were above away from the light source and in the two upper lenses the surfaces with the ridges were towards the light source, i. face down, and the top surface of the top lens acted as a table, eliminating the need for a separate sheet of material to act as a table.

Straight, stepped lenses are generally made by forcing, compressing, or molding in a mold from an artificial polymeric material, such as polymethyl methacrylate. Other useful polymeric materials include cellulose acetate butyrate and polycarbonate.

A rigid protective coating or sheet on the smooth top surface of the top is very important in a structure where the lenses are made of polymethylmethacrylastic. As shown in Figure 16, the lens structure may also include a plate 131 of glass or an optically clear polymeric material, such as clear polycarbonate, attached to the smooth top surface of the lens 125. This plate 131 forms a rigid support for the lens structure and a hard surface on which transparencies can be placed without the risk of surface damage or scratching. * 10 6311 8 It has hitherto been generally believed that the very large differences in the thermal expansion of methacrylics and inorganic glass prevent the two from being directly, asymmetrically joined, at least over the relatively large areas required in the overhead projector. With a linear thermal expansion coefficient of -6 ™ 6, 80 x 10 and 8.7 x 10, respectively, is the difference between panels of these two materials with an initial dimension of 25 cm, with a temperature change of almost 2 mm at 100 ° C. Temperature differences of this magnitude often occur in the transport and use of overhead projectors. The requirements of a growing lens surface also cause problems. Although glass sheets have long been successfully joined together, e.g. in the manufacture of safety glass, no attempt has been made in the past, to our knowledge, to attach glass sheets to plastic, expandable lenses in large, asymmetrical areas.

It has now been found that it is possible to join together in large areas organic plastic lenses, such as Fresnel lenses, which are a methyl methacrylate polymer, and panels, which are inorganic glass, i. with an area of more than 100 cm and preferably even at least

A

800 cm, as a combined structure capable of withstanding temperature fluctuations of at least 100 ° C without distortion or tearing. In addition, it has been found that it is possible to incorporate additional plastic, expandable lenses into a unitary structure to provide a closed, temperature-stable, efficient table and collector lens system for a space-consuming overhead projector.

Figure 17 shows the fabrication of a simple lens and table structure. A compression plate 133, a glass panel 134, a bonding film 135, and a plastic panel 136 are placed in a press between a smooth-faced molding plate 137 and a molding plate 138 having a negative, increasingly grooved surface 139 and corner surfaces 140. First, the combination is heated to soften plastic parts. Then the pressure is switched in accordance with the direction of the arrow 141, while supplying the cooling water flow through the muovauslaattojen. The clamp is then opened and the lens-table combination is removed.

The second structure shown in Figure 18 combines a combination 142 of a table 134, a film 135, and a lens 136 'with a lens 143 and, if desired, a pair of lenses 144 to form an assembled combination of lens and table. A rubber seal 145 is connected between the smooth edges of the plastic lens 136 'of the assembly 142 and the lens 143 to hold the two together while leaving space for the Lins sip 144.

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Multiple portions can be positioned precisely because the three corners of the lens 136 'have alignment pins 146 formed in the apertures 140 of the molding plate 138 and projecting from the flat corner edges, and because the opposing rods 147 are similarly formed on the lens 143. These opposing rods fit strictly to the radially extending, oval apertures 148 of the angular inserts 149, or alternatively to similar apertures made in the elongated corner edges of an equivalent pair of inner lenses, not shown. Angle guards are used to position and hold the two outer lenses precisely optically aligned. In addition, they can position the inner pair 144 in the correct orientation by engaging the truncated edges of the lens pair 144. The same operation can be accomplished by forming perforated angles in the inner pair of lenses 144 corresponding to the inserts 149. The lenses 150,151 of the second pair of lenses 144 are connected to one of the corners in a permanently aligned manner. (Lenses 136 'and 143 could have a circular, incremental lens shape, e.g., as described in U.S. Patent No. 3,334,958, in which case the inner pair of lenses 144 may be omitted and alignment provided by angular inserts 149).

In a particular embodiment, the glass panel 134 is double "flot" glass having a side length of 25 cm and a thickness of 3.07 mm. The binding film 135 has a thickness of 0.75 mm and consists of 100 parts by weight of polyvinyl butyral and 37 1/2 parts of an inert plasticizer, e.g. dibutyl sebacate. The plastic panel 136 has the same thickness and consists of a methyl methacrylate polymer.

It is covered on the surface adjacent to the binding film with a minimal, smooth, uniform coating of an inert resin base that promotes adhesion to the binding film. One suitable base material is "Plexigum 2045" available from Rohm & Haas Co.

The combination is preheated to 150 ° C and then compressed to a pressure of 25 kg / cm 2. Cooling is started at the moment the pressure is switched on and the temperature in the center of the combination is reduced to 38 ° C in about 1/2 minute. The press is then opened and the combination is removed.

However, small unevenness in the pressure between the molding plates, which could be destructive, is smoothed by means of a press plate 133 consisting of a 1.6 mm layer of high temperature resistant 12 63118 silicone rubber with a profitable, thin copper sheet.

It has been found that the table-lens structure thus manufactured is able to withstand temperature fluctuations in the range of -35 ° C to + 75 ° C, which may well occur when moving from a loading latitude in northern latitudes in winter to a closed car parked in the sun in midsummer without any signs of damage.

Some deviations are allowed in certain parts. For example, the thickness of the binding layer can be reduced to 0.5 mm and the thickness of the plastic panel can be about 0.6-0.9 mm. These values may be changed when the thickness of the glass plate is also changed, provided that the change is not too great and that the same proportions are maintained. Glass plates less than 2 mm thick cannot withstand the pressures sometimes applied to projector tables; if the plate is more than 4 mm, the structure is unnecessarily large and heavy and prone to heat shocks. The relative thicknesses of the glass sheet, the bonding film and the plastic panel are generally about 10: 1.5 to 2.5: 2.0 to 3.0, respectively.

When plastic panels are considerably thicker, the stresses caused by large thermal fluctuations are large enough to cause the glass to bend and break. Thinner plastic panels, on the other hand, become stretched and pulled apart. Sharp changes in the thickness of the binding film also cause damage, mainly due to the breakage of the glass panel or the detachment of flakes from its surface.

Excellent bonding between the binding film and the clear glass is achieved by the heat and pressure used. Direct bonding between the film and the plastic lens is less effective, but by using a transparent resin base, a completely satisfactory bonding is achieved.

Although it would be likely that very large temperature changes could cause distortion of both the binding film and the plastic lens, as well as bending of the entire panel, it has been found that such effects are so small that they do not significantly differentiate the structure as an optical table and lens. In addition, the uniform structure eliminates the interfaces between glass and air and plastic and air that are otherwise present in the table and lens combination, which improves optical efficiency.

The following are some examples:

A 0.5 mm thick cellulose acetate butyrate panel is bar coated with a dissolved terpolymer obtained from ethyl 13 6311 8 acrylate, N-vinylpyrrolidone and t-butyl acrylamide and dried under a forced stream of air at 60 ° C. A 0.38 mm thick polyvinyl butyral sheet, softened with 31% triethylene glycolide (2-ethylbutyrate), is then placed in surface contact between the cellulose acetate butyrate coating and the double "float" glass. for five seconds and then compressed at a pressure of about 100 kg / cm using a cylinder with a diameter of 18 cm for 15 seconds.During the application of pressure, the temperature is reduced to 40 ° C before the press is opened.

In a different example, an extruded polymethyl methacrylate sheet having a thickness of 0.75 mm is rod-coated with a poly (hydroxyphenyl ether) resin (Phonexy PKHH, manufactured by Union Carbide) 2 to give a dry weight of 15 g / m 2 and then coated with a polyvinyl butyral resin. m to get the weight dry. A polyvinyl butyral sheet softened with 31% triethylene glycolide (2-ethyl butyrate) is then placed between the polyvinyl butyral coating and the double float glass. In a molding plate press, the combination is heated to 160 ° C for 5 seconds, after which a pressure of 91 kg / cm is applied using a cylinder with a diameter of 18 cm for 25 seconds. The temperature is reduced to 40 ° C before the press is opened.

The high surface area optical components of the invention can be used in many other ways than in an overhead projector, e.g. as a condenser lens in traffic lights where an external non-scratch glass surface is required, as well as in certain display devices.

Claims (10)

14 631 1 8 A low-glare, staggered focusing lens of an overhead projector comprising a plurality of linear, staggered lenses having a cylindrical lens effect, the cylindrical axes of the pairs of lenses being oblique or perpendicular to each other, characterized in that the staggered focusing lens 102 comprises three linear, stepped ), which are oriented relative to each other so that the cylindrical axis (96, 97, 98) of each lens forms an angle of 55 to 65 ° with the cylindrical axis of the other two lenses. 2. A low-glare, staggered focusing lens of an overhead projector, comprising a plurality of linear, staggered focusing lenses having a cylindrical lens effect and whose cylindrical shafts intersect at an angle of more than 0 °, characterized in that the stepped focusing lens comprises four linear, staggered lenses 127, 129, 130) oriented in two pairs so that the cylindrical axis of one lens of one pair is located at an angle of 85 to 90 ° to the cylindrical axis of the other lens of the pair, and the pairs are oriented relative to each other such that ao of any two lenses The minimum angle between the axes is 5 ... 45 °. A low-glare, staggered condenser lens according to claim 1, characterized in that the staggered stencil lens comprises six linear, staggered lenses oriented in pairs so that the cylindrical axis (117, 118, 119, 120, 121, 122) of one pair is located At an angle of 85 to 90 ° to the cylindrical axis of the second lens of the pair, the pairs being oriented relative to each other so that the smallest angles of the cylindrical axes of each lens of one pair with respect to the cylindrical axes of the lens of the other pairs are 5 to 20 °. 4. A low-glare, staggered focusing lens of an overhead projector comprising a plurality of linear, staggered focusing lenses having the effect of a cylindrical lens and having a cylindrical axis forming an angle of about 90 °, characterized in that the staggered focusing lens comprises six linear, stepped lenses. , 111 ', 112', 112 ", 113 ', 114') which are oriented in triplicate so that the cylindrical axis (104, 105, 106, 107, 108, 109) of any of the three triangles is located At an angle of 55 ... 65 ° to the cylindrical axes of the other lenses of the triangle and the cylindrical axes of each lens of the second triangle are rotated 5 ... 10 °. Stepped collector lens according to one of Claims 2 to 4, characterized in that two of the stepped lenses (143, 144) form part of a one-piece plate (112), the steps of one stepped lens (143) being located on one surface of the plate (112) and the other the steps of the stepped lens (144) are located on the opposite surface of the plate (112). A stepped condenser lens according to any one of claims 2 to 4, having a surface (115, 131) on which the transparencies are placed, characterized in that half of the stepped lenses (143, 145, 146; 127, 130) are oriented so that their the stepped surfaces are located towards said surface (115, 131), and the halves (141, 142, 144; 125, 129) are oriented so that their stepped surfaces are located away from said surface. A stepped condenser lens according to claim 6, characterized in that half of the lenses (143, 145, 146; 127, 130) oriented so that their stepped surfaces are located towards said surface (115, 131) are located furthest from the surface (118). , 131). A graduated condenser lens according to claim 2, characterized in that the minimum angle between the axes of any two lenses of the two pairs of lenses is 25 to 35 °. Tiered condenser lens according to one of Claims 2 to 4, characterized in that a plate (115, 131) of glass or clear polymeric material is attached to the non-tiered surface of one tiered lens (125, 141). A graduated condenser lens according to any one of claims 2 to 4, characterized in that the non-staggered surface of the stepped lens (125, 141) furthest from the light source is turned away from said source and acts as a surface (115, 131) on which the transparencies are placed for projection. for. 631 1 8 16