GB2273812A

GB2273812A - Image enhancement device

Info

Publication number: GB2273812A
Application number: GB9226990A
Authority: GB
Inventors: Anthony David Newton
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 1992-12-24
Filing date: 1992-12-24
Publication date: 1994-06-29
Anticipated expiration: 2012-12-24
Also published as: GB2273812B; GB9226990D0

Abstract

An image enhancement device 10 in which light emitted from a source 8 passes through a set of colour filters 21, 31, 41 and falls upon a set of photocathodes 22. Electrons emitted by the photocathodes are accelerated by an electric field before impacting a set of phosphors 23. Light generated by the phosphors then falls upon a further set of photocathodes 24. The process is then repeated until the enhanced image 9 is emitted by the final set of phosphors 27. The filters may chosen such that the first and final images have the same colour characteristic. Alternatively, if the first image is a photographic colour negative, the filters are chosen such that the final image has normal colour. <IMAGE>

Description

IMAGE ENHANCEMENT DEVICE AND ENHANCED IMAGE DISPLAY DEVICE FIELD OF THE INVENTION This invention relates generally to optical image enhancement.

BACKGROUND OF THE INVENTION Optical image displays, such as those used in many electronic user devices, typically have an arrangement of screen addressing in the form of a grid composed of horizontally and vertically aligned wires.

This arrangement is very suitable for small displays, where the number of wires is relatively small.

However a problem exists in that larger displays require a significantly larger number of wires which creates a difficulty in addressing. To overcome this, displays have been made which use a small screen which is then magnified to the size of display required. A problem with this arrangement is that conventional magnification results in a loss of luminance or brightness, thus restricting clarity and reception of the optical display by the user.

This invention seeks to provide an image enhancement device that will mitigate the above mentioned disadvantages.

SUMMARY OF THE INVENTION An image enhancement device comprises at least one series of photosensitive-electroemissive elements is arranged to receive the first image from an image source, for producing electrons in response to the first image.

At least one series of electrosensitive-photoemissive elements is arranged to receive the electrons in response to emission by the photosensitive-electroemissive elements, for providing a second image, the electrosensitive-photoemissive elements and the photosensitive-electroemissive elements being arranged such that the electrons are accelerated therebetween; In this way the second image produced by the electrosensitive-photoemissive elements has greater luminance than the first image.

A series of colour filters are coupled between the image source and the series of electrosensitive-photoemissive elements, such that the series of filters and the series of electrosensitive-photoemissive elements are arranged into matched groups of colours, wherein colour characteristics of the first image are repeated in the second image.

Alternatively, the electrosensitive-photoemissive elements may be mismatched with the filters, such that the colour characteristics of the first image are changed in the second image.

Preferably the colours of the colour filters and colour emitting elements are the primary colour pigments of red, green and blue, the electrosensitive-photoemissive elements are phosphors and the photosensitive-electroemissive elements are photocathodes.

BRIEF DESCRIPTION OF THE DRAWINGS An exemplary embodiment of the invention will now be described with reference to the drawing of FIG.1 which shows a preferred embodiment of an image enhancement device in accordance with the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring to FIG.1, there is shown an image enhancement device 10. A first screen 11 of the device 10 is coupled to receive first light signals from an image source 8. A series of colour filters (21,31,41 and others) are coupled to the first screen 11 for providing filtered light signals in response to the first light signals from the image source 8.

A first series of photocathodes (22 and others) is coupled to the first screen 11 for receiving the filtered light signals from the series of filters and for providing emitted electrons in response to the filtered light signals. A first input voltage terminal 19 is coupled to the first series of photocathodes for maintaining a first voltage thereat.

A second screen 13 contains a first series of phosphors (23 and others) coupled to receive the emitted electrons from the series of photocathodes for providing second light signals in response to the electrons. A second input voltage terminal 20 is coupled to the first series of phosphors for maintaining a second voltage thereat.

A second series of photocathodes (24 and others) is coupled to the second screen 13 for receiving the second light signals from the first series of phosphors and for providing emitted electrons in response to the second light signals.

The first input voltage terminal 19 is coupled to the second series of photocathodes for maintaining a first voltage thereat.

A third screen 15 contains a second series of phosphors (25 and others) coupled to receive the emitted electrons from the second series of photocathodes for providing third light signals in response to the electrons. The second input voltage terminal 20 is coupled to the second series of phosphors for maintaining a second voltage thereat.

The first and second voltages of the terminals 19 and 20 respectively provide an electric field between the second series of photocathodes and the second series of phosphors.

A third series of photocathodes (26 and others) is coupled to the third screen 15 for receiving the third light signals from the second series of phosphors and for providing emitted electrons in response to the third light signals. The first input voltage terminal 19 is coupled to the third series of photocathodes for maintaining a first voltage thereat.

A fourth screen 17 contains a third series of phosphors (27 and others) coupled to receive the emitted electrons from the third series of photocathodes for providing fourth light signals 9 in response to the electrons. The second input voltage terminal 20 is coupled to the third series of phosphors for maintaining a second voltage thereat.

The third series of phosphors are colour matched to the colour filters, such that each of the phosphors produces fourth light signals 9 which are of the same colour as the filtered light signals from each of the filters The device 10 is evacuated such that a suitably hard vacuum exists, allowing a higher accelerating voltage than would be supported by a normal atmosphere within the device 10.

In operation, and with reference to a red region within each of the series of elements described above, a red filter 21 of the first screen 11 receives a first light signal from an image source 8 and produces a filtered light signal within the first screen 11 which is indicative of the red portion of the first light signal.

The filtered light signal travels through the screen and is received by a photocathode 22 coupled to the screen, producing thereat an emission of electrons in response to the filtered light signal. The emitted electrons are accelerated through the electric field provided by the first and second voltages of the first and second voltage terminals 19 and 20, each electron gaining energy according to the energy equation: (E2-E1) =e (V2-V1) where: e = charge on an electron; (V2-Vl) = difference in voltage; (E2-E1) = difference in energy.

Hence, an electron with initial energy E, accelerating with a voltage of 100 Volts, increases in energy by 100eV.

A phosphor element 23 of the second screen 13 receives the electrons which have increased in energy. The element 23, produces a second light signal in response to the electrons from the photocathode element 22. This second light signal has greater luminance than the filtered light signal.

In a similar way, photocathode 24 and phosphors 25 provide a subsequent third light signal which has a greater luminance than the second light signal.

Similarly, photocathode 26, and phosphor 27 provide a subsequent fourth light signal which has a greater luminance than the third light signal.

The fourth light signal produced by the phosphor element 27 of the fourth screen 17 is a red light signal. This red light, being derived from the third and second light signals respectively is therefore indicative of the filtered light from the red filter 21, but has greater luminance than the filtered light.

With reference to the other regions, similar processes as that described above for the red region are provided by a blue region and a green region. A blue filter 31 and a green filter 41, both coupled to the screen 11 provide light signals indicative of the blue and green portions of the first light signal 8 respectively. A blue phosphor and a green phosphor both coupled to the screen 12 provide blue and green light signals respectively in a similar fashion to the red light provided by the red phosphor 27.

In this way a group of three regions divides the first light signal 8 into the three primary colours, each of which separately undergoes enhancement in the form of increased luminance, resulting in a combined output light signal 9 substantially the same as but having greater luminance than the first light signal 8.

A series of spacers 13, are placed between regions to prevent light signal interference between elements of the same series and to enhance the structural integrity which might otherwise be compromised by the hard vacuum employed.

The first and second phosphors of each region are the phosphors of the two other colours not pertaining to the region, arranged such that each region has an equal number of each colour of phosphor, wherein any difference in emissive output level between different coloured phosphors does not result in a colour imbalance in the output light signal 9.

A suitable number of subsequent groups of red, green and blue regions similar to the group hereinbefore described are arranged to provide a two dimensional grid network of groups.

In this way a two dimensional image provided by the first light signal 8 may be processed by the device 10, resulting in an output light signal 9.

It will be appreciated that alternate embodiments to the one described may be used wherein, for example, the regions may contain alternative colours to the red, green and blue primary colours.

It will also be appreciated that the series of filters on the screen 11 and the series of colour phosphors 17 may be deliberately mismatched such that the light signal 9 is colour changed with respect to the input light signal 8.

Also, a low pressure gas may be substituted for the hard vacuum of the device 10. The presence of the gas causing electron multiplication and emission of ultraviolet light, thus enhancing the excitation of the phosphor.

Additionally, it will be appreciated that the number of pairs of photocathode and phosphor element series may be different than the three pairs herein described above: for example, in its simplest form a single pair of photocathode and phosphor element series could be used, or alternatively four or more pairs could be used.

Claims

1. An image enhancement device comprising; at least one series of photosensitive-electroemissive elements arranged to receive a first image from an image source for producing electrons in response to the first image; at least one series of electrosensitive-photoemissive elements arranged to receive electrons in response to emission by the photosensitive-electroemissive elements, for providing a second image, the electrosensitive-photoemissive elements and the photosensitive-electroemissive elements being arranged such that the electrons are accelerated therebetween; wherein the second image produced by the electrosensitivephotoemissive elements has greater luminance than the first image.

2. The device of claim 1 wherein a series of colour filters are coupled between the image source and the series of electrosensitive-photoemissive elements such that the series of filters and the series of electrosensitive-photoemissive elements are arranged into matched groups of colours, wherein colour characteristics of the first image are repeated in the second image.

3. The device of claim 1 wherein a series of colour filters are coupled between the image source and the series of electrosensitive-photoemissive elements such that the series of filters and the series of electrosensitive-photoemissive elements are arranged into mismatched groups of colours, wherein colour characteristics of the first image are scrambled in the second image.

4. The device of claim 3 wherein the mismatch of colours is arranged such that if the first image is a photographic colour negative, then the arrangement of colours of the second image will be as the normal colours of the photographic image corresponding to the negative.

5. The device of any of the claims 2 to 4 wherein the colours of the colour filters and colour emitting elements are the primary colours of red, green and blue.

6. The device of any preceding claim wherein the device includes at least one additional series of photosensitiveelectroemissive elements and one additional series of electrosensitive-photoemissive elements, such that at least two stages of electron excitation exist.

7. The device of claim 6 wherein the number of additional series of elements is at least two and wherein the colours of the electrosensitive-photoemissive elements of the additional series are arranged such that each region has an equal number of each colour of electrosensitive-photoemissive element.

8. The device of any preceding claim wherein the photosensitive-electroemissive elements are photocathodes.

9. The device of any preceding claim wherein the electrosensitive-photoemissive elements are phosphors.

10. An enhanced image display device comprising an image producing screen and an enhancement device according to any preceding claim.

11. An image enhancement device as substantially herebefore described and with reference to the accompanying drawing.