U.S. Philips Corporation

Other

Adrianus J De Vaan

Theodorus L Welzen

Antonie W Damen

Dirk Jan Broer

Hendrik Adrianus Van Sprang

Martinus V Stroomer

Jorg Brambring

Jacobus H Neijzen

Adrianus H Van Den Brandt

Paulus Bj Schaareman

The invention relates to an image projection module (1) comprising, in this order, an illumination system (3) and an image display system (13) having at least one display panel (15) for modulating an illumination beam to be supplied by the illumination system (3) with image information. The illumination system (3) comprises an integrator system (19) having an exit surface which is located in an exit plane. First reflecting means (33; 43) are present in the exit plane of the integrator system (19) and the module (1) further comprises second, selectively reflecting means (39). An optical system (31) for at least partly imaging the exit surface via the second reflecting means on the first reflecting means is arranged between the first and the second reflecting means.

Image projection module and image projection device provided with such a

The invention relates to an illumination system (1) comprising, in this order, a radiation source (5) and an integrator system (11). First reflecting means are present in the exit plane (25) of the integrator system (11) and second reflecting means in the form of a reflective polarizer (29) are further present in the illumination system (1). An optical system (23) for at least partly imaging the exit surface of the integrator system (11) via the second reflecting means on the first reflecting means is present between the first reflecting means and the second reflecting means. Moreover, polarization-converting means are present between the first and the second reflecting means. The invention also relates to an image projection device and to a presentation system provided with such an illumination system.

Illumination system and image projection device provided with such an

The illumination system (21) includes two radiation sources (23, 25) and an optical system for concentrating the radiation into beams, a common polarizing system (11) for splitting the beams (b.sub.I, b.sub.II) into linearly polarized sub-beams, and at least one polarization-rotating element (35). The polarizing system includes at least one optically transparent plate (11) having a refractive index n.sub.0 and a first face and a second face. At least one of these faces is provided with an optically thin layer having a refractive index n.sub.1 which is larger than n.sub.0. The light path of the sub-beams whose directions of polarizations are not to be converted incorporates a reflector (41, 43) for reflecting the sub-beams into the same direction of propagation as that of the other sub-beams. The chief ray of these beams and the normal on the plate (11) enclose an angle which is substantially equal to the Brewster angle which holds for the interface between the optically thin layer and a medium surrounding the polarizing element (11).

Illumination system for an image projection device

A projection beam supplied by a projector is incident on a beam splitter in the form of a cholesteric filter. The cholesteric filter reflects circularly polarized radiation having a wavelength which corresponds to the pitch of the molecular helix and having a direction of rotation which corresponds to the direction of the molecular helix to a reflector. The circular direction of polarization reflected by the cholesteric filter is inverted on the reflector so that the beam is subsequently passed to the screen by the cholesteric filter.

Image projection system

Picture display device (1) comprising an illumination system (3) provided with a light source (5) for generating a light beam. The device (1) also comprises a picture display panel (9) having a matrix of pixels (10) for modulating said light beam in conformity with picture information to be displayed. A first microlens array (13) having a plurality of first lenses (15) and a pitch .DELTA.w.sub.1 is present between the illumination system (3) and the picture display panel 9. A second microlens array (17) having a plurality of second lenses (19) and a pitch .DELTA.w.sub.2 is present between the first microlens array (13) and the picture display panel (9). The focal planes of the two microlens arrays coincide and .DELTA.w.sub.1 =.DELTA.w.sub.2 =.DELTA..sub.w applies to the pitches. The first lenses (15) have dimensions which are substantially equal to the dimensions of the second lenses (19). The illumination system (3) is adapted in such a way that the illumination system, when being in operation, supplies a plurality of sub-beams which are incident on the first microlens array at different, well-defined angles.

Picture display device with two microlens arrays

A picture display device is disclosed having an illumination system and a picture display panel which is provided with a matrix of n panels and has a pitch p.sub.p. The device further has a projection lens system for projecting light modulated by the picture display panel to form an image. The illumination side of the picture display panel is provided with a microlens array having m microlenses and a pitch p.sub.m. The illumination system includes N illumination elements which are arranged in an array and have pitch p.sub.1. The illumination elements generate light simultaneously. Moreover, N&lt;&lt;m,n and p.sub.1 &gt;&gt;p.sub.m, p.sub.p.

Picture display device

An illumination system comprising a reflector, a cholesteric filter and a depolarizer. The cholesteric filter is arranged between a radiation source and, in a display device, a display panel, and is selected to transmit radiation having a selected state of polarization in a selected wavelength range, while reflecting otherwise polarized radiation in that wavelength range. The depolarizer is disposed between the reflector and the cholesteric filter. Radiation reflected by the cholesteric filter is re-reflected to the filter by the reflector and, having been depolarized in the depolarizer, is transmitted to the extent it has the selected state of polarization in the selected wavelength.

Illumination system and display device including such a system

A compact and efficient image projection system is described. The projection beam supplied by a projector is incident on a beam splitter in the form of a cholesteric filter. The cholesteric filter reflects circularly polarized radiation having a wavelength which corresponds to the pitch of the molecular helix and having a direction of rotation which corresponds to the direction of the molecular helix to a reflector. The circular direction of polarization reflected by the cholesteric filter is inverted on the reflector so that the beam is subsequently passed to the screen by the cholesteric filter.

A reflecting image projection screen (1) is described, as well as an image projection system (17) in which such a projection screen (1) is used. Viewed from the front side (3) of the projection screen (1), the image projection screen comprises, in this order, a linear polarizer (9), a .lambda./4 plate (11), a reflecting polarizer (13) in the form of a cholesteric filter and a reflecting layer (15) which is also active as a depolarizing diffuser layer. By combining a cholesteric filter (13) with a depolarizing reflecting layer (15), an image projection screen is obtained which is highly reflective to the direction of polarization supplied by the image projector (19) and substantially absorbs the other direction of polarization.

Reflecting image projection screen and image projection system

An image projection arrangement is disclosed, comprising a radiation source (1), an image display system having at least one image display panel (10) in which the polarisation direction of an incident beam is modulated with the image information, and a polarisation-sensitive beam splitter (2), arranged between the source and the image display system, for forming two mutually perpendicularly polarised sub-beams (b.sub.1, b.sub.2). By having the two sub-beams be modulated by the same image display system (10) and by thereafter combining these sub-beams again a very efficient use can be made of the available light without the necessity of a significant more complex design of the arrangement.

Image projection arrangement

An image projection apparatus is described, which comprises an illumination system (100, 101, 54, 57, 62) having a first, round lens plate (54) and a second, half-round lens plate (57). A combination of a special polarization-sensitive beam splitter (20) and a polarization rotator (31) is arranged in the path of the beam supplied by this system and converts the beam into two sub-beams having the same state of polarization which jointly illuminate a display panel (1) in a uniform manner and optimally fill the surface area of this panel and a subsequent projection lens system (C).

Image projection apparatus

In a polarization-sensitive beam splitter 10 having a polarization-separating layer 13 interposed between two transparent elements 11, 12, the two transparent elements consist of non-birefringent material and the polarization-separating layer is a polarizing birefringent oriented polymer adhesive layer. The polarization-separating layer is manufactured from a curable synthetic resin composition comprising liquid-crystalline monomers or oligomers, the molecules in the curable synthetic resin composition being oriented uniaxially after which the synthetic resin composition is cured.

Polarization-sensitive beam splitter having a polarizing birefringent

The light output of a color LCD (10) is considerably increased by arranging dichroic mirrors (31, 32, 33) register with the pixels (20), which mirrors pass the color suitable for the pixel and reflect the other colors so that they can be reflected back again by a reflective surface (45) and be used in the display.

Electro-optical color display device and projection apparatus

A liquid crystal display device which comprises two supporting plates spaced a distance d from each other the which a pattern of line and column electrodes, respectively, is provided on the facing surfaces and form a matrix of display cells. A mixture of a nematic liquid crystal with a cholesteric addition is present between the supporting plates. The mixture has a positive dielectric anisotropy and a natural pitch p such that the ratio d/p has a value between 0.5 and 1. The cell support surfaces comprise an orientation layer which gives the director over the layer thickness d a rotation between .pi. and 2.pi. radians with, the director at one surface enclosing an angle of tilt between 0.degree. and 70.degree. and at the other surface an angle of tilt between 5.degree. and 70.degree.. Data voltages are applied to the column electrodes and line selection pulses are applied to the line electrodes. The line selection voltage, the data voltage and the frame time are chosen to provide a display cell in the stationary 'on' condition during the frame time show a transmission which is formed by the superposition of a background level T.sub.b1 and a peak response with peak height T.sub.1, while a display cell in the stationary 'off' condition during the frame time shows a transmission which is formed by the superposition of a background level T.sub.b2 and a peak response having peak height T.sub.2, and a display cell which is switched from the stationary 'off' condition to the stationary 'on' condition to reach the 'on' condition via a transmission-response curve which is formed by the superposition of a background level and a peak response having final values T.sub.b1 and T.sub.1, respectively, T.sub.1 being larger than or equal to 0.5 (T.sub.b1 -T.sub.b2). The display device shows fast switching times with a large multiplex ratio and has a contrast with a small dependence on the viewing angle.

Liquid crystal display device

In a low drive voltage display device having a matrix structure, the number of rows to be addressed is selected to be smaller than is possible on the ground of threshold steepness. The required selection voltages can then be selected to be considerably lower than the voltages in accordance with the Alt & Pleshko addressing scheme.

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Eindhoven, Netherlands

Adrianus J De Vaan