Television – Camera – system and detail – Optics
Reexamination Certificate
1999-07-08
2004-07-20
Christensen, Andrew (Department: 2615)
Television
Camera, system and detail
Optics
Reexamination Certificate
active
06765617
ABSTRACT:
The present invention concerns an optoelectronic camera comprising an optical objective system for imaging a scene recorded by the camera as an optical image substantially in an image plane of the objective system, an optoelectronic detector device substantially provided in the image plane for detecting the optical image and on basis of the detection outputting output signals, a processor device connected with the detector device for converting and processing the output signals of the detector device in order to reproduce the detected image in digital form and possibly for displaying this in real time on a display device optionally provided in the camera and connected with the processor device, and a memory device connected with the processor device for storing the digital image for displaying on the optional display device which also may be connected with the memory device, or for storing, displaying or possible additional processing on external devices adapted for these purposes and whereto the camera temporarily or permanently is connected.
The present invention also concerns an optoelectronic camera, particularly for recording colour images and even more particularly for recording colour images in an RGB system, comprising an optical objective system for imaging a scene recorded by the camera as an optical image substantially in an image plane of the objective system, an optoelectronic detector device substantially provided in the image plane for detecting the optical image and on basis of the detection outputting output signals, a processor device connected with the detector device for converting and processing the output signals of the detector device in order to reproduce the detected image in digital form and possibly for displaying this in real time on a display device optionally provided in the camera and connected with the processor device, and a memory device connected with the processor device for storing the digital image for displaying on the optional display device which also may be connected with the memory device, or for storing, displaying or possible additional processing on external devices adapted for these purposes and whereto the camera temporarily or permanently is connected. Finally, the present invention concerns a method for digital electronic formatting of a recorded full-format optical image in an optoelectronic camera according to any of the claims
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32
or any of the claims
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37
, wherein the recorded optical image is stored as a digital image in a memory in a processor device provided in the camera and may be displayed on a display device connected to the processor device.
Very generally the invention concerns optoelectronic cameras which are suited for recording of still images as well as cinematographic images. including video images. The optoelectronic cameras according to the invention are realized such that they can be made as cheap miniature cameras with an extremely flat form factor.
After the launch of charge-coupled components (CCD), electronic photography is being applied in almost all fields in the imaging technology from the most demanding scientific applications such as in astronomical photography with recording of still images under extremely low light intensities and to applications for mass markets such as home video and area surveillance. Up to recently optoelectronic camera devices almost without exception have been based on the use of charge-coupled components (CCD), while other types, for instance charge-injected components (CID) have gained a certain use in particular applications, mostly of scientific nature. The basis for use of CCD for detection and implementation of optoelectronic cameras is extensively discussed in scientific and commercial literature and shall in the following hence be regarded as well-known to persons skilled in the art.
Even if it has been a great success, the CCD technology in optoelectronic cameras causes a number of disadvantages which has a negative effect on the possible use of CCD and miniaturized cheap battery-driven optoelectronic cameras. The silicon-based CCD chip is relatively costly to fabricate, it requires several different drive voltages and consumes relatively much current. In the course of the last years a new class of components called active pixel sensors (APS) has appeared to be strong competitors to the CCD technology, particularly in applications which do not require the absolute maximum image quality. The APS-based optoelectronic detectors can be made with low cost by means of standard CMOS technology and permits integration of a number of functions such as light detection, signal conditioning, power supply and interfacing on the same chip. In addition to the possibility of a very low cost, low power consumption and compact physical realization, the APS detectors may be realized such that processing of the image information is obtained directly on the detector chip, including for instance thresholding, contour determination etc. For certain types of applications APS detectors may give fast random access to the selected pixels or groups of pixels, in contrast with CCD-based detectors which require serial readout of whole rows of pixels at one time.
Commercial applications of APS-based miniature device have emerged within a number of areas, either supplanting other technologies or generating wholly new products. An instance of the first is the use in surveillance cameras, an instance of the latter is the use in toys. Due to the particular properties of the APS detectors recent development has led to optoelectronic cameras with very small dimensions. Such so-called “on chip”-cameras may be obtained commercially from a number of companies, for instance VLSI Vision, Scotland, firms in Sweden and Photobit, U.S.A. A camera which may be accomodated in fountain pen format was recently demonstrated by CSEM, Switzerland.
A common denominator for all optoelectronic camera types is an optical system which creates an acceptable optical image on the light-sensitive detector surface. This poses a problem when it is desired to miniaturize optoelectronic cameras regardless of the type of optoelectronic sensor (CCD, CID, APS, diode array . . . ) to be used. The problem becomes particularly accentuated if the available axial length (the distance along the optical axis from the front of the camera lens and therethrough to the back of the detector chip) of the camera is restricted, i.e. when it is desirable to manufacture a flat camera, as the contribution from the imaging system to this distance is the sum of the lens thickness and the back focal length (BFL), something which indicates that a lenslet or microlens with a very short axial dimension and very short focal length might be used to provide a flat camera solution. However, up to now really flat miniaturized optoelectronic cameras based on this principle have not emerged.
As is to be discussed in the following, the main reason for this substantially is not to be found in the optics used and which generates the optical image. Even if the resolution in the last instance is limited by diffraction, there is another delimiting factor which to a much larger extent finds expression in the present context, namely the restricted spatial resolution which may be obtained in the image plane, particularly with optoelectronic detector arrays. In order to better illuminate the logical step in the development which has led to the present invention, there shall in the following be given a simple basic analysis of the drawbacks of the prior art.
The quality of the optical image will depend on the lens construction and is, as mentioned, in the last instance, limited by diffraction. In order to simplify the analysis it shall be supposed that light is monochromatic green, for instance with a wavelength of 555 nm, and that the lens is very thin and diffraction-limited. The spatial resolution in the image plane is then given by
w=
0.61
&lgr;/N
A
(1)
wherein &lgr; is the light's wavelength and the numerical aperture N
A
defined as
Gudesen Hans Gude
Leistad Geirr I.
Nordal Per-Erik
Tangen Reidar E.
Birch Stewart Kolasch & Birch, LLP.
Christensen Andrew
Harris Tia M.
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