Television – Camera – system and detail – Combined image signal generator and general image signal...
Patent
1992-08-17
1997-06-10
Faile, Andrew
Television
Camera, system and detail
Combined image signal generator and general image signal...
348297, H04N 5235
Patent
active
056381190
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention concerns a device for increasing the dynamic range of a camera so that it is tolerant of large differences in brightness between the points of the scene of which an image is viewed.
2. Discussion of the Background
Its applications are mainly in shooting under uncontrolled light conditions outdoors, in endoscopy and in welding robots.
Known tube or CCD type cameras are very intolerant of smearing and blooming and have a very low dynamic range (ratio of brightest to least bright areas viewed correctly and simultaneously) in the order of 100.
They are also insufficiently sensitive for shooting at night.
Other devices have an image sensor and one or more passive screens disposed optically in front of the image sensor and controlled by it which have a greater dynamic range but provide a highly unstable image. They provide closed loop matrix optical control and suffer from either oscillation of the output signal and the image transmitted or a response time very much greater than that of the image sensor.
SUMMARY OF THE INVENTION
The present invention intends to remedy these drawbacks by producing a stable image and a wide dynamic range, possibly exceeding 100 000. Also, the image produced may embody very high sensitivity.
To achieve this the device in accordance with the present invention is a device for increasing the dynamic range of a camera comprising an electronic primary image sensor operating in a spectral band and supplying image data for a range of brightness values impinging on it with a first dynamic range, said dynamic range representing the ratio of the greatest brightness value to the least brightness value of this range, and a lens forming an image of a scene on said primary image sensor characterized in that it comprises a second image data source, said image data coming from at least one image of said scene shot through said lens in the same spectral band as that of said primary image sensor and an image processing electronic circuit combining the data from the primary image sensor and the data from the second image data source and supplying image data representing the scene viewed with a ratio of the greatest brightness value to the least brightness value of areas of said scene represented by said output image data, said ratio being greater than the dynamic range of the primary image sensor.
The second image data source may comprise a secondary image sensor sensing the same image as the primary image sensor but with a different sensitivity.
The second image data source may also comprise an image store. Image data stored in said image store may represent an image sensed previously by the primary image sensor, an image resulting from processing an image previously sensed by the primary image sensor, or an image obtained from a plurality of views taken previously by the primary image sensor, combined or added together.
Other electronic circuits and additional functions are described. In particular, various image data processing systems can be adapted to suit these various embodiments. They are concerned in particular with controlling the sensitivity of the primary image sensor over all of its surface or in areas thereof by means of a matrix flat screen disposed optically in front of the primary image sensor. Other additional systems concern the output of a signal representing an image having a monotonous response (in the mathematical sense) according to the brightness of points in the scene viewed by the primary image sensor.
The following description given with regard to the appended drawings by way of non-limiting example only will provide a better understanding of the advantages, objects and features of the invention.
The dynamic range of an image sensor on which light rays impinge is the ratio of the highest to the lowest brightness areas viewed correctly and simultaneously. Between these two values the sensor outputs image data representing the brightness. The lowest value is equal to the sensitivity. Above the hi
REFERENCES:
patent: 5157499 (1992-10-01), Oguma et al.
patent: 5247366 (1993-09-01), Ginosar
patent: 5264940 (1993-11-01), Komiya et al.
P. Lecturcq and G. Rey; Dunod, Paris; pp. 145-150.
Faile Andrew
Ho Tuan V.
Scanera S.C.
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