Abstract: A device of the invention is associated with a projector including a horizontal platform on which document sheets are placed one after the other in order to project images thereof on a screen. The device includes two removable cassettes each fitted with levers carried by respective shafts actuated by respective electromagnets. Above the leading edge of each cassette there are two transverse shafts carrying return pulleys over which belts pass for driving the top document from a stack of documents in the cassette. The device includes a horizontal plate which is positioned in alignment with the platform of the projector. An application lies in projecting images during a lecture.

Abstract: A highlighter module, adaptable to an overhead viewer is disclosed. The highlighter, when placed on top of an overhead viewer, will highlight a segment of the displayed information by moving a curtain to the desired location. This curtain, attached to tension cables, forms a continuous movement in either direction. The highlighter can be used with or without a cable remote control.

Abstract: A hand-held calculator has a transparent window carrying a liquid crystal display as well as transparent number and function key locations such that when placed on an overhead projector, the calculator can be used to demonstrate to a classroom of students all operations performed in a sequence of mathematical operations. The plastic casing of the calculator has one or more small holes passing through the casing at corners. Another feature of the calculator is an improved keyboard of relatively small domain size for each key, with a spacer grid on the back surface of the keyboard membrane panel overlay element, effective to provide pressure isolation of an active key from adjacent keys and also to prevent other pressures on the keyboard from causing mistaken entries. A further feature of the calculator is a protrusion or foot at each corner of the back of the calculator casing.

Abstract: Projector comprising a housing, a support frame formed with a carrying surface for carrying a flexible file sheet in which transparent materials are arranged in the form of a matrix longitudinally and transversely, light source device arranged in the housing at one side of the support frame, projecting lens device arranged at the other side of the support frame, the support frame being mounted on the housing for a reciprocating movement in a first direction, the support frame being provided with guide rails for movably carrying the file sheet in a second direction perpendicular to the first direction. The projector further comprises retaining device for retaining the file sheet onto the carrying surface. The retaining device is mounted on the support frame for slidable or rotatable movement relative to the file sheet so that the transparent material can be easily changed in the file sheet without focus readjustment.

Abstract: A portable, hand-held display and control apparatus for operatively demountably receiving an interactive electronic video game module includes a housing formed of a central body and a pair side-mounted, outwardly-extending arms by which the housing is grasped by a user. Illuminating elements within the housing project images from a substantially transparent screen of the video game module onto a remote viewing and display surface. A plurality of switches and like control elements on the housing arms are user-actuatable for interactive control of the video game.

Abstract: Educational apparatus for use with an overhead projector has a transparent grid with horizontal and vertical indices for projecting a grid onto a wall screen. A plurality of removable cover pieces, keyed to the grid, cover up grid segments whereby when the transparent grid has pictorial material a student, or player, may project a particular grid segment by picking up the cover piece on that segment.

Abstract: An overhead projector comprises, a main body, a light source disposed in the main body for emitting a light, a Fresnel lens disposed on an upper surface of the main body, an internal mirror for reflecting the emitted light toward the Fresnel lens, disposed rotatably in the main body such that a portion of the internal mirror is protruded from a bottom of the main body to an outside of the main body upon a use of the projector and is accommodated in the main body upon a non-use of the projector, an arm connected with the main body at one longitudinal end thereof, a projection lens held by the other longitudinal end of the arm for focusing the reflected light which has passed through the Fresnel lens and an original for a projection placed on the Fresnel lens, and a projection mirror for directing the focused light from the projection lens toward a screen.

Abstract: An interactive image projection apparatus for the projection of computer generated images on a projection surface in cooperation with a light source and projection optics for projecting a beam of light from the light source onto the projection surface. The apparatus includes a substantially transparent image display device disposed in the beam of light and including means for receiving image-defining signals from a computer and producing an image based on the image-defining signals that is projected onto the projection surface in the beam of light. A touch screen, at least a portion of which is substantially transparent, is disposed in the beam of light between the image display device and the projection surface and includes means for generating a signal when touched for use as input information at the computer. Preferably, the touch screen is supported directly over the image display device.

Abstract: A cassette web transport mechanism is placed upon an overhead image projector. Multiple overhead projector slides are conveniently secured in a roll of the web. The web is moved in forward or reverse direction by remote control in order to display the desired slide through the projector.

Abstract: A variable power reflectory type overhead projector for forming a projected luminous beam by lighting a reflecting mirror from the projecting lens side. A transparent film-to-be-projected support is provided between a regular position of the film to be projected and the projecting lens, and an auxiliary lens is included for focusing the projecting lens on the support.

Abstract: A liquid crystal display device for an overhead projector has a light-transmissive liquid crystal display cell sandwiched between protective plates both from above and below. At least one of these protective plates is separated from the cell surface to form an air passage provided with a fan such that air can be caused to flow therethrough and come into direct contact with the cell. The cell can thus be cooled efficiently and the light of the projector can be increased for projecting a clearer image.

Abstract: An overhead projector comprises a housing the upper side of which is closed by a transparent writing plate under which there is a Fresnel lens. A lamp in the housing is provided with a cold light reflector and a condenser lens for directing light upwardly through the Fresnel lens and writing plate. A projection head mounted above the writing plate on a support arm extending up from the rear side of the housing and comprising an objective lens and a deflection mirror directs the light received from the lamp through the Fresnel lens and writing plate onto a projection screen. A liquid crystal display in a frame hingedly mounted on the rear side of the housing can be swung between an operative position overlying, but spaced from the writing plate and an idle position up against the support arm where it is held by a magnet.

Abstract: An overhead projector having scanning device for scanning an original image thereby generating electric signals corresponding to the original image, selecting device for selecting one of a thermochromic film and a thermographic paper, a first heating device for heating the film thereby erasing an image formed formerly in the film, a second heating device for heating the film in accordance with the electric signals transmitted from the scanning device to form an image corresponding to the original image in the film when the film is selected by the selecting device and for jheating the thermographic paper in accordance with the electric signals transmitted from the scanning device to print an image corresponding to the original image in the thermographic paper when the thermographic paper is selected by the selecting device, andprojecting device for projecting the image formed in the film on a given screen.

Abstract: An overhead projector which has a stage for supporting an original thereon comprises an optical system for collecting light to the entrance pupil of a projection lens and a movable mirror for directing light from an illumination light source to an optical system.The movable mirror is movable with the movement of the projection lens parallel to the plane of the stage for placing an original thereon so that trapezoidal distortion and loss of focus which occur when the projection lens projects an image at an oblique angle are avoided. The position for the collection of the illumination light by the optical system is changed according to the movement of the projection lens, and illumination light is always collected at the position of the entrance pupil of the projection lens.

Abstract: Apparatus for demonstrating the use of a computer terminal comprises a projection module supported on a standard overhead projector. The projection module includes a frame which is adapted to rest on an illumination window of the overhead projector. A transmissive liquid crystal display is mounted in the frame parallel to the illumination window such that an image on said liquid crystal display is projected by the projector. A transparent touch screen is also mounted in the frame overlaying the liquid crystal display. By means of a stylus, a user touches the touch screen and thereby designates desired text and/or images for subsequent display. Coupled to the decoder is a computer which retrieves the desired text and/or images which are then transmitted to a display driver. The aforesaid apparatus is most suited to demonstrate a computer terminal which has a touch screen for selecting text and/or images for display.

Abstract: A color overhead projector including a thermochromic film, a color filter, erasing means for erasing an image formed on the film, reading means for reading a color image to be projected, writing means for writing the color image to be projected into the film, and projecting means for projecting the color image written into the film onto a screen by illumining the film via the color filter.

Abstract: Projector apparatus including a light source, a projection head and a projection stage aperture for an object, the image of which is to be produced. The aperture is situated in the ray path between the light source and the projection head. An ellipsoidal mirror is situated in the light path between the light source and the aperture. One focal point of the ellipsoidal mirror substantially coincides with the light source and the other focal point of the mirror substantially coincides with the projection head. The projection head includes a deflection means. The projection head is situated substantially in a plane constituting a normal plane to the aperture plane and containing the front edge line of the aperture, as observed in the generally horizontal projection direction.

Abstract: A hand-held calculator for use in conducting classroom demonstrations of the operation thereof, including use of the operation instruction key means. The calculator comprises a frame, a keyboard section, data processing means and a display section and where both the keyboard and display sections are transparent to permit images thereof to be projected on a screen for teaching purposes.

Abstract: A portable overhead projector has a top surface which slopes downwardly from the rear wall to the front wall and includes stops on the top surface adjacent to the front wall for preventing a transparency from sliding off the top surface during use and to preset the distance of the leading edge of the transparency from the bottom edge of the protecting wall.

Abstract: A transmissive overhead projector includes a Fresnel lens assembly which has an f-number of about 0.25 and is capable of dioptrically focusing light at an incident angle of at least 60.degree. with respect to a perpendicular to the Fresnel lens assembly. This refractive power of the Fresnel lens assembly allows the overhead projector light source to be positioned very close to the Fresnel lens assembly and consequently allows a significant reduction in the base height of the overhead projector.

Abstract: In an overhead projector comprising a writing plate, and under this arranged Fresnel lens, a light source and an objective carried by a carrying arm, the problem to be solved is to overcome the disadvantages of the state of the art and to provide a possibility for a lecturer to make information retrieved from an electronic information source, for example, a computer or an electronic game, accessible to a large viewer and listener circle. The invention solves this problem thereby, that between the Fresnel lens and the writing plate there are arranged a layer of liquid crystals which are aligned in an electric field and transparent electrodes on both sides thereof, whereby two of the plates or films traversed by the light beam have light polarizing properties.

Abstract: A portable overhead projector comprises a rectangular box-like housing having an open top and four side walls, a projecting lamp disposed in the housing and a planar fresnel lens. The fresnel lens is mounted in the housing for pivotal movement from a storage position wherein the fresnel lens is adjacent the open top of the housing to an operative position wherein the fresnel lens is spaced above the open top of the housing and the projecting lamp. A projecting head assembly is mounted to the housing when the fresnel lens is in the operative position to dispose the projecting head assembly thereabove and a cover is connectable to the housing for covering the fresnel lens when in the storage position.

Abstract: An overhead projector is provided which is able to project a uniformly focused image of a transparency onto a vertical surface at an oblique angle above the horizontal plane without introducing keystone distortion by offsetting a projection lens and its associated mirror from the center of a transparency stage of the projector in the direction of projection and directing light through the transparency and to the projection lens at an angle which is equal to the oblique angle above the horizontal plane at which the image is projected. Light is directed to the projection lens by offsetting the upper lens of a two-element circular Fresnel condensing lens system in the direction of displacement of the projection lens.

Abstract: An overhead projector which projects a distortion-free image onto a vertical screen at an oblique angle above the horizontal plane. In a first embodiment of the invention, a projection lens and mirror are displaced from the center of a transparency stage in the direction of projection and a thin, linear, incrementally-grooved prismatic sheet is positioned parallel to the stage and between the stage and a lighting means to redirect light transmitted through the stage and the transparency to the projection lens. In a second embodiment of the invention, the grooved prism is formed as an integral part of the lighting means.

Abstract: An over head projector has a standard projection lens for projecting the whole view of an original image and a partial projection lens for projecting a part of the original image in enlarged scale. One of the projection lenses is selectively brought to a projection position for projecting the original image onto a projection screen. A stage for supporting the original image is vertically movable and is moved up and down when the projection lens is changed. The selection of the projection lens and the vertical movement of the stage are associated with each other so that the original image is always at a proper position with respect to the focal length of the selected projection lens.

Abstract: A disclosed projector includes a condenser lens, a plurality of light source means having different focal lengths and disposed around the condenser lens, a projecting lens with an adjustable distance from the condenser lens, and a stage glass located between the condenser and projecting lens for carrying a transparent positive thereon. Depending on the size of the transparent positive, one of the light source means is selected and the distance between the condenser and projecting lens is adjusted, so as to project an image of substantially fixed magnitude with a constant brightness regardless of said size of the transparent positive.

Abstract: A system for previewing and projecting slides that are stored in spaced, co-planar relation in a planar holder is disclosed. The slides are previewed, either individually or in a group, in their natural orientation without removing the slides from the holder. Projection of the slides to form a naturally oriented image also is accomplished without removing the slides from the holder. In the preferred embodiment, means are provided for moving the planar slide holder orthogonally with respect to the optical axis of the projection system. A slide indexing system is provided to allow the projectionist to select a particular slide for projection. The slide indexing system utilizes cooperative means on the slide holder and projector to achieve indexing and, if desired, other control functions. In an alternative embodiment, the projected image plane is vertical and can be rotated about a vertical axis at the projector without moving the base of the projector.

Abstract: An apparatus for projecting images simulating the phenomenon of combustion on a display media is provided with a control means for quickly positioning, expanding, and diminishing the images. Light from a light source is passed through orange and grey translucent filter segments, a light dispersal means, and an animating means to project animated orange and grey light images upon the media, the orange light representing the flame component of combustion and the grey light representing the smoke component. The control means comprises a transparent tray situated between the dispersal means and the display media which is overlaid with opaque or translucent particulate material which may be cleared by the finger of an operator or the like from a small area at a selected position on the tray surface to project an image at a corresponding position on the media, the dimensions of the projected image corresponding to the dimensions of the cleared area.

Abstract: An overhead projector that uses as a condensing lens a linear echelon lens structure comprising a combination of linear echelon lens elements between the light source and stage of the projector to minimize glare emanating from the condensing lens.

Abstract: In an over-head projector or a slide projector, a positive or negative lens is provided immediately in front of a transparency in the projector. The lens is normally perpendicular to the optical axis of the projection lens, and is inclined to an oblique angle with respect to the optical axis when the image projected on a projection screen is distorted owing to oblique projection of the image on the screen.

Abstract: An overhead projection system which includes a planar lens assembly having two concentrically-oriented condensing lenses. The outer lens has a greater focal length than the inner lens to receive light reflected from the system's reflector while the inner condensing lens receives direct lighting from the system's light source. Accordingly, the inner lens images the light source at the projection lens of the system and the outer lens images the virtual image of the light source.

Abstract: In a system of overhead projection there is provided a horizontal stage on which is to be placed an object to be imaged. Means for illuminating the object is mounted below the stage at an angle thereto, while a projection lens system is installed above the stage and parallel thereto, in such a position that the axis of the light from the illumination means passes at an angle through its center. A mirror mounted above the lens system projects the undistorted image of the object onto a vertical screen. In another system of overhead projection based on the same principles, the stage and the projection lens system are inclined relative to the illumination means while themselves kept parallel to each other. The axis of the light from the illumination means in this instance extends vertically upwardly and passes at an angle through the center of the lens system. There are further disclosed herein some overhead projectors constructed in accordance with these systems of the invention.