Television – Mechanical optical scanning – Moving reflector
Patent
1995-09-27
1997-07-08
Burgess, Glenton B.
Television
Mechanical optical scanning
Moving reflector
348205, 348335, 348744, 348759, 348764, 2502081, H04N 104, H04N 308
Patent
active
056466838
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates generally to the field of imaging systems.
BACKGROUND AND SUMMARY OF THE INVENTION
Currently, electronic imaging cameras use two-dimensional arrays of light sensitive elements, sometimes of the type known as CCD (i.e., charged coupled devices) photodetectors, that convert light into electronic charges. There are many relatively low-priced color and black & white array CCD detectors available for video imaging, but they produce low quality images as measured by their low pixel (i.e., picture element) count and dynamic range. Array CCD photodetectors that produce images having a quality comparable to conventional 35 mm chemical photography must have a resolution of approximately 3000 by 2000 pixels . These arrays are expensive because they have low manufacturing yields.
Linear photodetectors cost much less than array detectors because they are much smaller and have higher manufacturing yields. The problem with linear photodetectors is that they* resolve only one line of pixels at a time and must scan the entire image, line by line, within the exposure time of the camera. The exposure time of hand held cameras must be less than 1/15 of a second because users cannot hold cameras still for longer than this. Ideally, the exposure time is much shorter, such as 1/125 of a second.
Previously known hand held cameras cannot use linear photodetectors because they cannot scan the linear detector across the entire image within their exposure time and because the linear photodetectors do not capture sufficient photons to produce a high quality image. If a previously known hand held camera were able to scan the linear detector across the entire image within its exposure time, the linear photodetector would be traveling at such high velocities and accelerations that it would jerk the camera out of the hands of the user.
Previously known stationary imaging systems, such as copiers and photographic scanners can improve their image quality by increasing the amount of ambient light and/or the exposure time. These techniques do not work for hand held cameras because of their short exposure time and their need to operate in a variety of light conditions.
For the reasons previously discussed, it would be advantageous to have an image capture system that scans an image across a detector very quickly without requiring the detector to move at prohibitively large velocities or accelerations. Also, it would be advantageous to have an image capture system that can increase the number of photons captured during a scan.
This invention is a system for capturing an image that has a lens to form an image on an image plane, a detector mounted to preclude translational motion, a mirror for deflecting the image to the plane of the detector, and a mechanism that moves the mirror to scan the image across the detector. The plane of the mirror "bisects" (i.e., divides into two equal parts) at 90.degree., an imaginary line between a cell on the detector that captured a portion of the image called here a "bundle of light" and a corresponding focal point on the image plane (i.e., the bundle of light that focuses on the cell of the detector has another focal point on the image plane called the corresponding focal point). If the detector has a width greater than one cell, then the detector rotates synchronously with the mirror. The image capture system can capture "images" produced by electromagnetic waves of any frequency and it is adaptable to many different devices, for example: photocopiers, hand-held still cameras, motion picture cameras, film scanners, scanners connected to printers to form copiers, fax machines, scanners connected to memory for storing images, scanners connected to computers for altering images, microscopes, telescopes, coherent optics systems, and many other systems.
This image capture system has the advantage that the motion of the detector and the motion of the mirror are minimized; and it can use inexpensive linear photodetectors, such as linear CCD photodetectors, to capture
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Burgess Glenton B.
Hewlett--Packard Company
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