GB2462280A

GB2462280A - Digital image projector

Info

Publication number: GB2462280A
Application number: GB0813957A
Authority: GB
Inventors: Kevin Michael Jarvis; Terrence Michael Burns
Original assignee: EQUIPE ELECTRONICS Ltd
Current assignee: EQUIPE ELECTRONICS Ltd
Priority date: 2008-07-31
Filing date: 2008-07-31
Publication date: 2010-02-03
Also published as: GB0813957D0

Abstract

A digital image projector system, optically combining coloured images from two or more image modulating panel arrays of pixel elements to provides a single image of increased resolution. The two components of the resulting image may be either adjacent or partially overlapped. The technique is particularly but not exclusively applicable to sequential colour operation.

Description

DIGITAL IMAGE PROJECTOR

This invention relates to enhancing the resolution of projected digital images by means of combining multiple modulating elements. The resultant image resolution is thus greater than that of the individual modulating elements.

Digital projection of images by means of various optoelectronic matrix panels capable of modulating the intensity of light either reflected or transmitted by picture elements, often named as pixels", is well known. One such panel design employs an array of microscopic mirrors that are individually electrically activated to either reflect a light source into a lens system and thus illuminate a small area of a projected image, or to beam the light away so as to leave a dark area.

Other panel designs employ liquid crystals to switch the pixels on and off by polarisation of the light in combination with polarising filters. In order to produce a coloured image, one such technique known as colour-sequential, employs a rotating coloured filter disk between a focussed light source and a modulating reflective panel in order to provide the perception of colour when the disc is rotated at sufficient speed to be synchronised with the switching of light in each pixel.

Other forms of image formation that could be used in this invention include those where light is transmitted through a matrix panel, which may also provide means to colour modulate within the panel itself and a type of matrix panel where individual elements or pixels are self illuminating with one or more colours. Another technique is known to provide multiple paths of different coloured light reflected from multiple panels and combined together optically prior to projection from a common lens. This method relies on the different image colour elements being combined by filter techniques that cannot be used in this invention as the two images to combine each contain multiple colours.

The projected image resolution is a measure of the number of picture elements or pixels contained withm the image that may he individually varied in intensity. The projection techniques described above provide images with a resolution determined by the total number of pixels present in the modulating panel. The physical size of a modulating panel is constrained by the projector size and optical performance and is therefore limited by space and cost constraints in many applications.

For a given panel size, the number of pixels is limited by production technology as with other electronic digital components. The resolution achievable from a particular panel type therefore is always a limiting factor in the overall resolution of a particular projector. In order to increase image resolution without change to the panel it is therefore normally necessary to employ multiple projection systems with resultant increase in cost and complexity of the resulting total display system.

According to the present invention, there is provided a means to display two or more times the number of pixels from one projector as are contained within a single panel. This is particularly applicable to the single panel projector arrangements using the colour-sequential method or any other single panel method of achieving coloured images. The relative position of two or more panels, supplied with colour sequential illumination, when presented to an optical combining device, allows two full colour modulated images to be either tiled together to form an image exactly twice the single panel size, and therefore containing twice the number of pixels, or in an alternative arrangement, the relative positions may be overlapped to a degree that allows blending to take place between two or more images.

A method of combining two images avoiding undue light loss and providing a variable degree of overlap is achieved using a system of relay optics and a combining "roof-prism". This prism has two sides of a sharp right angled ridge coated in a high reflective coating. An optical relay replicates an image in a displaced position using a set of lens elements in a well-known arrangement. The relayed images from two panels are then reflected by two faces of the roof-prism to form a single image beyond the ridge of the prism. The overlapped images are smoothly graded in intensity according to the distance of the image from the prism ridge. Coincidence with the ridge provides a sharply butted join with no overlap. As this distance is increased, the focus of each edge softens the linear blend with increasing overlap. The resulting combined image is then placed in the focal plane of a single exit lens to project the image beyond the projector onto a final image screen.

An embodiment of the invention is now described by way of example with reference to the accompanying drawing showing the main functional blocks in which:-Figure 1 illustrates the basic components of a digital projector using two coloured image sources combined to fom a single continuous projected image.

Figure 2 illustrates the known concept of colour-sequential projection.

Figure 3 illustrates a method of image combination using relay optics.

Referring to the drawing, Figure 1, Two lamps 2 and 12, are focussed by means of reflectors 1 and 11, and condensing and shaping optics 3 and 13, through two synchronised rotating colour filter disks 4 and 14, towards two reflective modulating image panels 5 and 15. Light reflected from image panel 5 together with light from image panel 15 is applied to an optical combiner unit 6 to provide a combination of the two images side-by-side when projected through a lens 7.

The electronic image source, on entering the projector unit, is divided electronically into two portions, each corresponding to the relevant panel position as seen on the final combined image.

A further modification to Figure 1 is envisaged whereby a light source such as provided by components 1,2,3&4 is divided nito two paths and applied to colour discs 4 and 14 in parallel, thereby saving the cost of one illumination system.

The known method for sequential-colour projection is shown in Figure 2. Light from lamp 22 is focussed by reflector 21 and condenser 23 through the rotating colour filter disc 24 onto reflecting image modulator panel 25. Light transmitted by the panel is directed through an optical projection lens system 26. The panel may modulate the light by either absorption of the dark parts of the image into the panel or by dynamic reflection of light in the darker parts of the image away from the collecting lens.

Figure 3. illustrates a method of image combination using relay optics. Within an optical combiner unit 6, as ao indicated in Figure 1, two optical relays 31 and 34 re-create the images formed on reflecting image modulator panels 5 and 15 respectively into a combined juxtaposed virtual image 36, first via the simple mirror reflecting surfaces 32 and 35 and secondly reflecting from the sides of roof prism 33. Reflecting mirror surfaces 32 and 35 are not essential to the image combination concept but rather provide a means of keeping the modulation panels physically close to each other within a projection device. The combined image is formed a small distance beyond the roof prism ridge in order to achieve a blended overlap between the two image sources. The projector exit lens 7 then projects combined virtual image 36 in the same manner as if this lens were focussed on one of the image panels 5 or 15.

Claims

CLAIMS1. A digital projector system comprising lamps, colour system, reflective modulation matrix panels, optical combiner and exit projection lens, whereby images from two or more panels are joined to display a greater number of picture elements in a projected colour image than can be provided by a single panel.
2. A digital projector system as in claim 1, where an optical combiner comprises two optical relay lenses and reflecting surfaces that combine images formed on the modulation matrix panels into a single image plane.
3. A digital projector system as in claim 1 and 2 that employs a roof-prism to combine two relayed images into a single image plane.
4. A digital projector system as in claim 1, allowing a degree of overlap of the two relative positions such that a blend may be achieved resulting in a seamless joining of the images formed by the two panels
5. A digital projector system as in claim 1, including an electronic means of dividing a single digital image signal into two overlapping parts.
6. A digital projector system as in claim 1, using a modified lamp system that makes use of a single lamp only by dividing the focussed light into two paths.
7. A digital projector system as in claim 1 or 2, whereby the modulation matrix transmits light through itself.
8. A digital projector system as in claim 1 or 2, whereby the modulation matrix is self illummating.
9. A digital projector system as in claim 7 or 8, whereby the modulation matrix is capable of colour modulation.
10. A digital projector system as in chum 1 or 2, providing more than two different images to be employed thus increasing resolution by multiple times.