DE1808532A1 - Floor projector with anti-glare screen - Google Patents

Description

M 2523

ΡΑ7Έ; .ANWALTt Dr.- !; . '■■■■■ . ·, U DHKE

Minnesota Mining and Manufacturing Company, Saint Paul

Minnesota 55101 (VoSt.VoA.)

Stand projector with anti-glare screen

Me invention relates to optical devices and im special focus on an improvement in stand projectors as well as on a glare protection screen, which is used in such projectors can be used.

A stand projector that has been widely used in classrooms, such as ζ _β Β _β the projector described in US Pat. No. 3 126 786, has as
intense light source a condenser lens in the form of a Fresnel lens, a flat picture table and a projection head. If desired, means can be used to reduce the effects of heating

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are provided »When using the device, a slide image is placed on the image table and the image is projected onto a screen. The user of the device stands at the On the side or in the back corner of the projector, facing the audience, and can look on during the presentation point out or mark important parts of the slide, so that the notices or markings on the screen are visible to the viewer. Here is the slide Fully accessible to the user. However, the intensity of the light emerging from the projector is so strong that that it is difficult for the user to observe both the slide and the audience. The user will either temporarily blinded by the emerging light so that he cannot see the audience or the user is wearing it to protect his eyes glasses with dark (colored) glasses, which he must take off to see the audience, or he deems it necessary to reduce the intensity of the light from the light source, with the projected image for the listener is less visible.

The effect of the external light as a result of the internal reflection on the condenser lenses is generally annoying and particularly annoying for the user when projectors with a flat IPresnal condenser lens are used. The structure of such lenses leads naturally to a concentration of the light longitudinally of that diameter of the lens is visible, which lies with the operator in a line ,, This effect has been called "propeller effect ^M due to the shape of the propeller of the visible district of high intensity Light and because of the movement of the light beam as the viewer walks around the projector.

The invention is intended to eliminate these deficiencies and difficulties so that the slide remains fully visible to the user while keeping the eye of the user the external light or the reflection that can be reached is greatly reduced or essentially completely eliminated ”. Simultaneously will not dip intensity of the projected image

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accordingly prevents but remains strong enough. Of the The presenter can therefore briefly take a look at the slide to mark a certain point and then turn his gaze back to the audience without this a momentary glare occurs while the projected Image remains visible to the viewer.

These stated objects of the invention are achieved, preferably, but not necessarily, between the Condenser lens and the transparent slide table, a shield that reduces reflection or a light control plate is arranged, which allows the passage of light from the condenser lens to the projection optics, but the side Scattering of external light in the direction of the user is prevented or minimized. The control member can therefore between the condenser lens and the image table, can be arranged on the outside of the image table, or it can be used as an image table itself to serve. On the other hand, the control plate can also be combined with a Fresnel condenser lens, or the condenser lens, the control plate and the image table can be connected to one another to form a unit, or the slide can also form a unit with the control plate.

The invention will now be described in detail in the accompanying drawings Drawings is the

I? Ig.1 a diagrammatic representation of a conventional Execution of a stand projector according to the invention has been modified,

Pig, 2 is a vertical section along the line 2-2 in FIG by an embodiment of the invention, while Fig.2a shows a Draüläicht on the glare-reducing Shielding element shows while the

Figo3-7 cross sections of further embodiments of the glare show diminishing shields or controls.

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The projector 10 shown in the figure has a housing 11 with a lamp and a reflector, which is accessible through a door 12 and by means of a switch 13 and a supply cord and a plug 14 can be connected to a power source · For the purpose of cooling is in the housing a fan is provided. Forms the upper part of the case one arranged in a frame 23. Slide table 15, the is held in place by the wedge-shaped fastening members 26 and the screws 28. A stand 17 carries a projection head 16 above the center of the slide table, which by means of a button 18 and the associated Gear for focusing the projected image vertically can be adjusted;

As can be seen from the detailed illustration in FIG _e 2, the projector includes a Fresnel condensing lens 19, the top of a in the present case and a lower lens 20, 21 is that lenses in the frame 23 by a fastening member 27 and a Screw 29 must be held at each corner · Directly below the slide table 15 and away from the lenses 19, a glare protection screen 22 is arranged in the frame 23, which arrangement is currently preferred. As shown, the anti-glare screen 22 consists of a transparent flat matrix in the form of a series of transparent straight-line segments 24 which are separated from one another by very thin, opaque cover films 25. At each corner of the square slide table 15, small triangular segments are removed from the shield 22 to make room for the fastening members 26 and the screws 28.

An anti-glare screen of the embodiment shown in Figures 2 and 2a can be made by peeling off (cutting or scraping) a thin plate made from a solid block of superimposed thermoplastic and transparent films, which films have a thin layer on one side a black lacquer are provided, such as ζ · Β _β in the American patent

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No. _e 2 053 173. The plate can generally have a thickness of 0.9 mm, so that the height of the black bands is also 0.9 mm, while the bands are spaced approximately 0.3 mm apart, so that the ratio of band height to band distance is 3 (Aspect ratio), where an aspect ratio between approximately 2 and approximately 4 in the case of upright projectors of the embodiment shown in the figure has the highest degree of effectiveness, as has been determined. The outer flat sides of the plate are made optically clear and transparent, for example by polishing or _e presses against heated polished plates. If the plate is arranged below the Diapositivtisches 15 at the position as shown in FIG _e 2 of the glare protection shield 22, the Jj opaque strips or covers 25 to the side edges of the table 15 (parallel to the vertical plane of the projection axis of the head 16 from run, glare is effectively prevented on both sides of the projector

In most cases, a right-handed operator will stand near the corner R (3? Ig, 1) at a distance just enough to be able to reach the slide table with his hand while keeping his shoulder out of the projection beam. If desired, the plate 22 can be oriented so that the masking tapes are perpendicular to this position, in which case the aspect ratio can be reduced somewhat. "

The glare protection plate can simply be removed and repositioned be oriented differently, or the plate can be designed circular and in a circular frame inside of the frame 23 are rotatably mounted, so that the cover strips can be brought into the most favorable position for each particular location of the operator, to achieve For the best results, the masking tapes should run across the plate and at right angles to the diameter directed at the operator. In most

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In some cases, however, the plate provides adequate protection against glare if it comes from the design described consists and is arranged as shown in Figures 1 and 2, with the masking tapes parallel to the sides of the Frame and cross said diameter at an angle of no less than about 45 °.

It is also possible to arrange the masking tapes inclined, as shown in FIG. 3 for the masking tapes 35 in the plate 32, ZoB ₀ in such a way that the peeling off from the block of colored films lying on top of one another according to the American patent Ur. 2,053,173 at a suitable angle. Combinations are provided by angles B z _{0 e} by Abschälem along suitable curves or plane by curving the first plate. An even more effective structure can be obtained in that an initially flat plate, such as the plate 22 according to FIG. 1, is deformed into a flat bowl which fits into the space between the slide table 15 and the lens 19. In this way, plates can be produced whose cover strips run vertically in the middle and, when approaching the side edges of the plate more and more obliquely or inclined, the rays of the projection light from the condenser lens 19 are only very little obstructed, while the glare from the assumed position of the operator from seen, is still severely restricted. In another embodiment of the glare shield, which is more difficult to manufacture, the opaque cover strips are arranged in concentric rings that run vertically in the center, but form increasingly inclined frustoconical segments at the outer edges, each segment of which is parallel to the light rays from the Condenser lens runs in the place of the cover tape.

In the structure according to Figure 3, the plate is covered on both outer sides with a layer of a translucent material 36 ZoB ₀ made of glass or a plastic, which itself as

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Table for which slides can be used. The glare masking plate can also be connected to the Fresnel lens to form a unit .

To make the anti-glare plate, sheets are first used made of cellulose acetate butyrate folded into a block with the required dimensions, which sheets or foils to are provided on one side with a coating of carbon black in a solution of the same polymer. Under the action of Heat and pressure solidify the block into a unit and cut it into thin, transparent, flat plates. On every Side of the plate becomes a thin film of plasticized polyvinyl butyral A sheet of glass is then placed on this film, after which the whole thing is pressed together at an elevated temperature to form a unit that resembles the 3 has shown cross-section, however, the masking tapes run perpendicular to the surface of the plate, as shown in FIG. The procedure described is the same essentially the process that is used in the manufacture of safety glass.

The opaque strips or bands 25 ii- er glare Protective plates absorb a small part of the usable light from the condenser lens, so that the intensity dee projected Image is diminished a little. This effect can be weakened by using the lowest possible number of masking tapes is provided, which are made as thin as possible and as parallel as possible to the light rays can be arranged from the condenser lens 19, as already stated.

The loss of the projection light in the anti-glare plate can also be kept low with the aid of the designs shown in FIGS. 4-6.

Fig. 4 shows a glare protection plate 42, which consists of two with Plates 44, 47 provided with longitudinal grooves, which longitudinal grooves have a V-shaped cross-section and each other so

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oppose that an air space 43 is formed. Such an arrangement is described in the American patent specification No. 3 255 665. The angles which the sides of the grooves form with the vertical are chosen so that the side surfaces 45 are mainly parallel to the usable light rays which fall from the condenser lens 19 through the critical area. The lower plate is on the corresponding surfaces Silver-plated or mirror-coated, as shown in FIG. 4 by the more drawn-out lines 48. The other surfaces 46 run at an angle where the usable light rays are thrown through the plate on the projection head, while the rays causing the glare shine deep Totally reflected are "Me eggs and hips on the surfaces 45 and 46 cross the icy diameter of the lens" which lies in a line with the assumed position of the user's _{ines 5} which in most cases means that the Hillen run diagonally over the Biapositii ^ table 15, with the Bemitser .des @ © rät®s cn -eksg ¹ Safe © ¹¹ H · '. The grooves can also be sm koaseateiselasH Ί & ο & βφώ. or to a continuous spiral ang © o: s? fe @ -u -7GMqSo

Me in dei Mg 5 shown ρ Hc Dt ¹ IC "s iuu 'of narrow, gciielcfccsi w> r \ ocvoP 1 ι ι Φ ^Λ , ν-» ^r " with not reile ^v tlcT · iicVn larUkL ^ £ or with Grlasprüvcr t""^" * ¹¹ ^ ηIrI ic Πα J ^ g ι each other »j ι ι - ^. ^ ^ ^rfi i γ · μι & _c ^ 1 ( ¹ O_ ~ ± _ IiichtstraliJ, J ^ u <-jucZ ^^ ric oe 1. Jl ^ u tu ζ '"·-> ■ ί - ^ ^ ¹ -" = ³ aera: ¹ ,. ~> den Pj: "^ izeli at ^ r ^ jr, c '< ^{| r} "' ^ = is scattered, hamlet τ * ν m L LcIi Is br ,, "ilr ^ ι / sf * ¹ ^^ i, ^ "_ ^ the projection olsOi ·! ^ Eiii ^v l» cc wii <· -u lorczri ¹ ^ "I ^c double rc fell tier« 7JbV u. ^ Ebwt "cctcus ^ d. J ^ ic ^ J 2 exits to the line of conspicuousness «

The Figes showing further another iaisfiilariag protective plate 62, the two mutually ame gegeiail stationary with A ^ s'SqM Hatten 63 and 64 feestelits wsleii © mats ai ^s j 'v Lelen prismatic. Eippen provided siad ₉ with a

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Air gap 65 are separated from each other, mad in the longitudinal direction should be aligned to the location of the user and not run at right angles to this, as with the off guides according to Figures 4 and 5 «The from below and in one generally perpendicular to the vertices of the hip Light rays incident in plane pass through the plate through, while the light rays incident at a considerable angle to the said plane at the prism-air interface are totally reflected and cannot escape as blinding rays.

The particular angular and spatial relationships of the various surfaces in the arrangements shown in Figures 3-6 are of course different for the different materials and depend on the refractive index and other properties of the used special materials.

The]? Ig.7 shows a currently preferred embodiment with a second frame member 70, which is placed on the frame 23 of the projector according to FIGS. 1 and 2 o the slide table 15 is secured in the frame 70 by means of the fastening members 26 and the screws 28 '. The two side edges of one Anti-glare plate 22 rest on strips 71 provided on the frame, and the slide table rests on the edges the anti-glare plate. The frame is provided at both ends with narrow strips 72 which form the corresponding edges the anti-glare plate press against the lower bar 73 of the original frame 23, so that the protective plate a rounded outline. As a result, the anti-glare plate 22 is given the shape of a bowl with a flat bottom and with the upwardly curving side edges, the cross-section being similar to the cross-section of a flat bowl. the Masking tapes 25 * protect the user against the clipping that is generated by the surfaces of the Fresnel lens. The shape of the edges reduces or eliminates secondary glare, which can be caused by a reflection on the surface of the anti-glare plate itself. The entire top

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Unit sits directly on the original frame of the protector and serves as an easily attachable accessory or as a replacement for the original slide table 15 _f although equivalent results can also be achieved if the combination of the two frames 25 and 70 is replaced by a correspondingly designed single frame will",

Patent claims

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Claims (1)

Claims 1. Stand projector with a light source, with a slide table, with a projection head and with a condenser lens that directs the light from the light source through the Throws slide table onto the projection head, whereby the slide is projected onto a viewing screen, characterized in that a glare protection screen is arranged between the condenser lens and the slide that attenuates the intense glare at the assumed location of a user of the projector, but without to bring about a corresponding reduction in the intensity of the projection beam. 2 »Stand projector according to claim 1, characterized in that that the condenser lens consists of a Fresnel lens, and that a glare protection screen is a series of opaque lenses thin Afcdeckbänder has »e between the condenser lens and the slide are arranged tuid cross that diameter of the lens that in sighting sum specified assumed location runs. 3 · Stand projector according to claim 2, characterized in that uLaas the ^ emannt masking tapes an aspect ratio between 2 and 4 have. 4 · Stand pro;) ector according to claim 3, characterized in that that said cover tapes are arranged in a transparent matrix. 3. Stand projector according to claim 4, characterized in that said matrix is flat, and that the masking tapes are equally spaced, parallel to each other and perpendicular to the plane of the matrix. 909832/0876 6 · Stand projector according to claim 4 »characterized in that each cover band is generally parallel to the projection light rays runs from said lens at the location of the masking tape. 7. Stand projector according to Anspruoh 5 »characterized in that the anti-glare screen, on the underside of the slide table and is separated from the Fresnel lens when the projector is in the upright position. 8. Anti-glare s china for one with a condenser lens equipped stand projector to dampen the intense Glare light rays along the diameter of the lens that corresponds to the assumed location of the user, runs without correspondingly reducing the intensity of the projection beam, characterized by a transparent matrix, which are parallel to each other at small distances. light impermeability and thin masking tape, contains, which have an aspect ratio in the approximate range of 2-4. 9 · Anti-glare screen according to claim 8 in the form of a general square flat plate with cut corners, characterized in that the masking tapes are perpendicular run to the plane of the plate. 1Oo anti-glare screen according to claim 8, characterized in that that the anti-glare screen has the cross-section of a flat shell and directly above said Lens is arranged, and that the masking tapes essentially j borrowed parallel to the projection rays from the genannj th lens in the projector. 11. Anti-glare screen according to claim 10, characterized by means of an open square frame, which on two opposite sides with narrow, the protective screen supporting strips and at the two opposite ends with narrow, inner and protective screens 909832/0876 ι is provided with pressing strips at the bottom, which are named ^: strips cause the anti-glare screen to have the cross-section mentioned, » 12. Methods for improving the effectiveness of a stand-; projector, which is equipped with a condenser lens below the slide table, thereby marked ^; net that a glare-reducing screen is arranged between said lens and the point of the projection image, which screen eliminates the intense glare along the diameter of the lens that runs in the direction of the assumed location of a user, without, however, correspondingly reducing the intensity of the projected light beam . 13 · Anti-glare screen, which is used in the method according to claim 12, characterized in that the anti-glare screen has a number of opaque, thin masking tapes " 14 ·· Glare protection screen, which in the method according to claim 12 is used, characterized in that the glare protection screen essentially consists of two opposing and provided with longitudinal ribs and longitudinal grooves Plates, with the sides of the grooves forming an angle useful for causing internal reflection the glare rays are sufficient, while the essentially light rays running perpendicular to the protective screen are allowed to pass through. 15 «Anti-glare screen for use in the procedure according to claim 12, characterized in that the anti-glare protection screen consists essentially of a transparent thin plate that is effective within the whole Area and along the glare path a series of regularly spaced pairs of parallel 909832/0876 -H- and planar light reflecting closer together Contains surfaces that occupy a certain inclination with respect to the plane of the plate that at least one of said faces is transparent, and that a non-reflective layer covers the faces of each pair of separates each other. 16o anti-glare screen according to claim 15, characterized in that that the same one surface of each pair of surfaces is mirrored and reflects. 17 ° anti-glare screen according to claim 16, characterized? that the top of each of the said Pairs of surfaces is translucent that the transparent plate has a relatively high refractive index, and that each of the surfaces of the said pairs of surfaces is essentially completely with a lower refractive index having material is in contact 909832/0876