INFRA-RED VIDICON
United States Patent 3675071
An infrared vidicon utilizing a photo-emissive cathode from which the target of the vidicon is scanned to detect infrared radiation in the intermediate infrared region.
US Patent References:
INFRARED DETECTION AND IMAGING APPARATUS EMPLOYING QUENCHABLE LUMINESCENT PHOSPHORS
Robillard - July 1971 - 3596097
Thermal image converter
Garbuny et al. - September 1962 - 3056062
/2929868.html
Leiter - March 1960 - 2929868
Apparatus for generating picture signals
Mayo - October 1963 - 3106605
INFRARED DETECTION AND IMAGING APPARATUS EMPLOYING QUENCHABLE LUMINESCENT PHOSPHORS
Robillard - July 1971 - 3596097
Thermal image converter
Garbuny et al. - September 1962 - 3056062
/2929868.html
Leiter - March 1960 - 2929868
Apparatus for generating picture signals
Mayo - October 1963 - 3106605
Application Number:
04/871399
Publication Date:
07/04/1972
Filing Date:
10/10/1969
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
250/330, 250/397, 250/333
International Classes:
H01J31/49; H01J31/08; H01J31/26; H01J39/00
Field of Search:
250/71.5S,83.31R,83.3H,83.3HP 313/65A,101,94 178/7.2 315/10
Primary Examiner:
Borchelt, Benjamin A.
Assistant Examiner:
Birmiel H. A.
Claims:
The invention claimed is
1. A vidicon comprising:
2. The vidicon of claim 1 and further including:
1. A vidicon comprising:
2. The vidicon of claim 1 and further including:
Description:
BACKGROUND OF THE INVENTION
The present invention relates to an infrared vidicon and more particularly to an infrared vidicon utilizing a photo-emissive cathode as a target-scanning source.
Prior art infrared vidicons for detecting the intermediate infrared region; i.e., 1.5 microns to 20 microns, have been plagued by the necessity of shielding the electron source and target from ambient infrared radiation, such as would be experienced with a normal thermionic emissive cathode. This has resulted in many complex implementations, such as that disclosed in an article by R. W. Redington and P. J. Van Heerden, entitled: "Doped Silicon and Germanium Photoconductors as Targets for Infrared Television Camera Tubes" in the Journal of the Optical Society of America, Volume 49, Number 10, Pages 997-1001. At best, these efforts have resulted in cumbersome, expensive and inefficient implementations in an attempt to solve the problem of detection in this infrared region.
According to the invention, a vidicon is provided having a photo-emissive cathode insensitive to infrared radiation in operable proximity to a target which is sensitive to infrared radiation. A scanning means is provided to scan the target with electrons from the photo-emissive cathode in a periodic raster. Optical means are also provided for projecting an infrared image on the target simultaneously with the electron beam raster scan.
An object of the present invention is the provision of an infrared vidicon for the detection of infrared radiation in the intermediate infrared region.
Another object is the provision of an infrared vidicon which is extremely sensitive.
A further object of the present invention is the provision of an infrared vidicon which does not require infrared shielding between its emitter and its target.
Still another object of the invention is the provision of an infrared vidicon which is inexpensive to manufacture and extremely efficient.
Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing in which the sole FIGURE is a schematic representation of the preferred embodiment of the invention.
DETAILED DESCRIPTION OF THE DRAWING
Referring to the drawing, a vidicon tube is shown generally at 11 having an envelope 12, one end of which is in proximity to a target 13. Photo-emissive cathode 14 is mounted in proximity to another end of envelope 12 of vidicon 11. An aluminum reflecting surface 16 surrounds photo cathode 14.
A scanning cathode ray tube 17 having a blue scanning spot emits a blue light which is focused by a lens 18 through a blue transmitting infrared rejection filter 19 to photo-emissive cathode 14.
Target 13 is coupled to a load 21 which, in turn, is coupled to an output terminal 22. Load 21 is located in a coolant reservoir 23 which has an intake line 24 and an exhaust line 26. An infrared image is transmitted through a visible rejection filter 27 to the reflecting surface 16 from which it is reflected onto target 13. A focusing magnet 28 focuses the electrons emitted from photo-emissive cathode 14 onto target 13.
OPERATION
In operation, cathode ray tube 17 is scanned with a raster which is focused onto photo-emissive cathode 14 by lens 18. Infrared rejection filter 19 prevents any heat from impinging upon photo-emissive cathode 14. Photo-emissive cathode 14 will, in turn, emit a raster-type scan which is focused by focusing magnet 28 onto target 13. In the absence of any infrared radiation impinging upon target 13, the output from target 13 will be a steady d.c. through load 21 which will be seen at the output terminal 22.
When an infrared image is passed through visible rejection filter 27 and reflected onto target 12 by reflecting surface 16, the output from target 13, as it is scanned, will vary in proportion to the infrared image since the electrical resistance of the target 13 will vary with this image. A video output can then be taken at output terminal 22 and reproduced with an indicator having a raster synchronous with the original raster of cathode ray tube 17.
A coolant fed in through intake line 24 to coolant reservoir 23 and out through coolant exhaust 26 will prevent target 13 from seeing any ambient temperature variations.
It can be seen that an extremely sensitive infrared vidicon has been provided by eliminating a thermionic emissive source and further by reducing the effects of ambient infrared radiation.
It should be understood, of course, that the foregoing disclosure relates to only a preferred embodiment of the invention and that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purposes of the disclosure which do not constitute departures from the spirit and scope of the invention.
The present invention relates to an infrared vidicon and more particularly to an infrared vidicon utilizing a photo-emissive cathode as a target-scanning source.
Prior art infrared vidicons for detecting the intermediate infrared region; i.e., 1.5 microns to 20 microns, have been plagued by the necessity of shielding the electron source and target from ambient infrared radiation, such as would be experienced with a normal thermionic emissive cathode. This has resulted in many complex implementations, such as that disclosed in an article by R. W. Redington and P. J. Van Heerden, entitled: "Doped Silicon and Germanium Photoconductors as Targets for Infrared Television Camera Tubes" in the Journal of the Optical Society of America, Volume 49, Number 10, Pages 997-1001. At best, these efforts have resulted in cumbersome, expensive and inefficient implementations in an attempt to solve the problem of detection in this infrared region.
According to the invention, a vidicon is provided having a photo-emissive cathode insensitive to infrared radiation in operable proximity to a target which is sensitive to infrared radiation. A scanning means is provided to scan the target with electrons from the photo-emissive cathode in a periodic raster. Optical means are also provided for projecting an infrared image on the target simultaneously with the electron beam raster scan.
An object of the present invention is the provision of an infrared vidicon for the detection of infrared radiation in the intermediate infrared region.
Another object is the provision of an infrared vidicon which is extremely sensitive.
A further object of the present invention is the provision of an infrared vidicon which does not require infrared shielding between its emitter and its target.
Still another object of the invention is the provision of an infrared vidicon which is inexpensive to manufacture and extremely efficient.
Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing in which the sole FIGURE is a schematic representation of the preferred embodiment of the invention.
DETAILED DESCRIPTION OF THE DRAWING
Referring to the drawing, a vidicon tube is shown generally at 11 having an envelope 12, one end of which is in proximity to a target 13. Photo-emissive cathode 14 is mounted in proximity to another end of envelope 12 of vidicon 11. An aluminum reflecting surface 16 surrounds photo cathode 14.
A scanning cathode ray tube 17 having a blue scanning spot emits a blue light which is focused by a lens 18 through a blue transmitting infrared rejection filter 19 to photo-emissive cathode 14.
Target 13 is coupled to a load 21 which, in turn, is coupled to an output terminal 22. Load 21 is located in a coolant reservoir 23 which has an intake line 24 and an exhaust line 26. An infrared image is transmitted through a visible rejection filter 27 to the reflecting surface 16 from which it is reflected onto target 13. A focusing magnet 28 focuses the electrons emitted from photo-emissive cathode 14 onto target 13.
OPERATION
In operation, cathode ray tube 17 is scanned with a raster which is focused onto photo-emissive cathode 14 by lens 18. Infrared rejection filter 19 prevents any heat from impinging upon photo-emissive cathode 14. Photo-emissive cathode 14 will, in turn, emit a raster-type scan which is focused by focusing magnet 28 onto target 13. In the absence of any infrared radiation impinging upon target 13, the output from target 13 will be a steady d.c. through load 21 which will be seen at the output terminal 22.
When an infrared image is passed through visible rejection filter 27 and reflected onto target 12 by reflecting surface 16, the output from target 13, as it is scanned, will vary in proportion to the infrared image since the electrical resistance of the target 13 will vary with this image. A video output can then be taken at output terminal 22 and reproduced with an indicator having a raster synchronous with the original raster of cathode ray tube 17.
A coolant fed in through intake line 24 to coolant reservoir 23 and out through coolant exhaust 26 will prevent target 13 from seeing any ambient temperature variations.
It can be seen that an extremely sensitive infrared vidicon has been provided by eliminating a thermionic emissive source and further by reducing the effects of ambient infrared radiation.
It should be understood, of course, that the foregoing disclosure relates to only a preferred embodiment of the invention and that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purposes of the disclosure which do not constitute departures from the spirit and scope of the invention.