GB1604375A

GB1604375A - Electro-optical scaninning apparatus

Info

Publication number: GB1604375A
Application number: GB2292277A
Authority: GB
Original assignee: British Aerospace PLC
Current assignee: BAE Systems PLC
Priority date: 1978-05-30
Filing date: 1978-05-30
Publication date: 1981-12-09

Description

(54) ELECTRO-OPTICAL SCANNING APPARATUS (71) We, BRITISH AEROSPACB PUBLIC LIMITED COMPANY, a British Company, organised under British Aerospace (Nominated Company) Order 1980 and British Aerospace (Appointed Day) Order 1980, of 100 Pall Mall, London, SW17 5HR, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to electro-optical scanning apparatus for converting between a picture and an electrical picture signal of which respective portions are representative of respective elements of the picture.

According to the present invention, there is provided electro-optical scanning apparatus for converting between a picture and an electrical picture signal of which respective portions are representative of corresponding elements of said picture, the apparatus comprising a lens, a liquid crystal plate and electro-optical transducer means arranged at conjugate points of said lens, and electrical control means for sequentially rendering a series of linearly extending regions of said plate transmissive of respective linearly extending sets of said elements and for causing said transducer means to be operable for each said set for converting in turn between respective ones of the elements in the said set and the cor responding portions of said signal.

The apparatus may be operable for producing a picture from a received picture signal or for forming a picture signal representative of a viewed picture.

Two preferred embodiments of the inven tion will now be described, by way of ex ample only, with reference to the accompanying drawings. In the drawings, Figure 1 illustrates diagrammatically electro-optical apparatus according to the invention for scanning an image, Figure 2 shows the image split into lines as achieved by the liquid crystal device, Figure 3 shows the image split into segments as achieved by the light sensitive scanning means together with the liquid crystal device, and, Figure 4 shows a typical scan pattern.

Referring now to Figure 1, electrooptical apparatus for scanning an image or "picture" comprises a planar liquid crystal device 1, on the rear surface of which the image to be scanned (the primary image) is formed. A lens 2 is positioned a suitable distance from the liquid crystal device so as to form a real image of the device, and a charge-coupled linear image sensor array 3 is positioned so that a secondary image of the image to be scanned may be formed at the charge-coupled device. Thus, devices 1 and 3 are located at conjugate points of the lens 2. A linear array of photodiodes may be used in place of the chargecoupled device. A light guide 4 may be included so that a simple lens e.g. planoconvex may be employed. Alternatively a cylindrical lens may be used having its optical axis perpendicular to that plane of the liquid crystal device.

The liquid crystal device 1 is of the type having the property of varying transmission and absorption of light. It is constructed so that a series of linearly extending regions 5 of the device may be activated in sequence, to become transparent or translucent. As each region 5 is activated in sequence by suitable electrical control means (not shown), the image to be scanned is revealed in a series of lines as shown in Figure 2.

Only one line of the liquid crystal device 1 is activated at any one time and an image of each line is formed on the sensitive area of the linear charge-coupled device. This device is also connected to control means (not shown) which causes it to scan the line image along its length, dividing each line up into a series of picture elements 6. Thus the charge-coupled device will in turn scan each line of the primary image, until the entire image has been scanned or until one frame has been completed, as shown in Figure 3. A typical scan pattern is shown in Figure 4. For purposes of illustration the image area is shown as being split into eight lines with seven picture elements to each line, giving fifty-six picture element for the whole area. It will be understood however that both the number of lines and the number of elements per line may be increased to provide a higher degree of resolution.

In another embodiment according to the invention the electro-qptical apparatus may be used for producing an image. In such an embodiment the charge-coupled device 3 is replaced by a linear array of light emitting diodes each of the diodes being individually addressable. The optical output of each diode may be varied so that the image formed may be intensity modulated.

In operation, one line of the liquid crystal device 1 is activated, becoming transparent, then as each of the light emitting diodes is addressed in sequence along the length of the array an image of the emitted light is formed on the liquid crystal. The line is then de-activated, and the next is addressed and so on until the entire image has been formed.

WHAT WE CLAIM IS: 1. Electro-optical scanning apparatus for converting between a picture and an electrical picture signal of which respective portions are representative of corresponding elements of said picture, the apparatus comprising a lens, a liquid crystal plate and electro-optical transducer means arranged at conjugate points of said lens, and electrical control means for sequentially rendering a series of linearly extending regions of said plate transmissive of respective linearly extending sets of said elements and for causing said transducer means to be operable for each said set for converting in turn between respective ones of the elements in the said set and the corresponding portions of said signal.

2. Apparatus according to claim 1, wherein said transducer means is optical radiation sensitive and the apparatus is operable for forming an electrical picture signal representative of a viewed picture.

3. Apparatus according to claim 2, wherein the transducer means comprises a charge-coupled linear image sensing array.

4. Apparatus according to claim 2, wherein the transducer means comprises a linearly extending array of photodiodes.

5. Apparatus according to claim 1, wherein the transducer means emits optical radiation and the apparatus is operable for producing a picture representative of a received electrical picture signal.

6. Apparatus according to claim 5, wherein the transducer means comprises a linearly extending array of light-emitting diodes.

7. Apparatus according to any preceding claim wherein the lens means comprises a cylindrical lens.

8. Apparatus according to any of claims 1 to 6 wherein the lens means comprises a plano convex lens and a light guide positioned adjacent the linear scanning means.

9. Electro-optical scanning apparatus substantially as herein described with reference to Figure 1 of the accompanying drawings.

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Claims

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whole area. It will be understood however that both the number of lines and the number of elements per line may be increased to provide a higher degree of resolution.

In another embodiment according to the invention the electro-qptical apparatus may be used for producing an image. In such an embodiment the charge-coupled device 3 is replaced by a linear array of light emitting diodes each of the diodes being individually addressable. The optical output of each diode may be varied so that the image formed may be intensity modulated.

In operation, one line of the liquid crystal device 1 is activated, becoming transparent, then as each of the light emitting diodes is addressed in sequence along the length of the array an image of the emitted light is formed on the liquid crystal. The line is then de-activated, and the next is addressed and so on until the entire image has been formed.

WHAT WE CLAIM IS: 1. Electro-optical scanning apparatus for converting between a picture and an electrical picture signal of which respective portions are representative of corresponding elements of said picture, the apparatus comprising a lens, a liquid crystal plate and electro-optical transducer means arranged at conjugate points of said lens, and electrical control means for sequentially rendering a series of linearly extending regions of said plate transmissive of respective linearly extending sets of said elements and for causing said transducer means to be operable for each said set for converting in turn between respective ones of the elements in the said set and the corresponding portions of said signal.
2. Apparatus according to claim 1, wherein said transducer means is optical radiation sensitive and the apparatus is operable for forming an electrical picture signal representative of a viewed picture.
3. Apparatus according to claim 2, wherein the transducer means comprises a charge-coupled linear image sensing array.
4. Apparatus according to claim 2, wherein the transducer means comprises a linearly extending array of photodiodes.
5. Apparatus according to claim 1, wherein the transducer means emits optical radiation and the apparatus is operable for producing a picture representative of a received electrical picture signal.
6. Apparatus according to claim 5, wherein the transducer means comprises a linearly extending array of light-emitting diodes.
7. Apparatus according to any preceding claim wherein the lens means comprises a cylindrical lens.
8. Apparatus according to any of claims 1 to 6 wherein the lens means comprises a plano convex lens and a light guide positioned adjacent the linear scanning means.
9. Electro-optical scanning apparatus substantially as herein described with reference to Figure 1 of the accompanying drawings.