Television – Camera – system and detail – With single image scanning device supplying plural color...
Patent
1994-07-18
1996-09-17
Metjahic, Safet
Television
Camera, system and detail
With single image scanning device supplying plural color...
348273, 348280, 348166, 348 33, H04N 904, H04N 533
Patent
active
055573266
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to the methods for producing false color images. The invention also relates to apparatuses applying the said methods for producing false color images.
2. Description of the Related Art
Semiconductor video cameras include a number of semiconductor detectors, generally silicon-based detectors, which are arranged in line form or in matrix form. In addition, these detectors are generally coupled as CCD-detectors. Such CCD-detectors are sensitive for both visible light and near infrared radiation, as is illustrated in FIG. 1. In color video cameras based on semiconductors, there are generally two or three arrays of CCD-detectors, the first array whereof is used for detecting blue color B, and the second for detecting combined green G and red R, or alternatively only green color G, in which case red color R is detected by means of the third array. The spectrum ranges of different colors with respect to wavelength are illustrated in FIG. 1.
In ordinary video cameras, the access of near infrared radiation to the detectors is prevented by placing a filter cutting off near infrared radiation in front of the said detectors. The colors of the drawing, i.e. blue, green and red, are separated by means of another set of filters provided in front of the different detector arrays.
From the Finnish patent publication FI 79,641, there is known a method and apparatus for producing a false color image. In the invention described in the said patent publication, the false color image is created so that from two channels, i.e. detector arrays, the effect of near infrared radiation was electrically reduced, whereafter the signals R, G, B representing various colors were coded, and a video image resembling a false color image was created.
A drawback with the known method and apparatus is, that the video signal is electrically processed for several times, which weakens the image quality. Another drawback of the invention is that this kind of electrical arrangement for producing a false color image uses a relatively high amount of electric power, which is an obvious disadvantage for instance while surveying the surroundings with a false color camera from an aeroplane.
SUMMARY OF THE INVENTION
The object of the invention is to introduce a new method for producing false color images, which method makes use of semiconductor cameras known as such. By means of the method and apparatus of the invention; the drawbacks of the known false color imaging method can be avoided, and the scanning can be realized in a remarkably simpler fashion than before. This is achieved by the characteristic features of the invention.
In the first method of the invention, there is utilized a video camera provided with two arrays of semiconductor detectors, the sensitivity range whereof in relation to wavelength extends from the range of visible light to the near infrared range, and where the radiation obtained in the semiconductor detectors is filtered. According to the invention, the radiation obtained in the first semiconductor detector array is filtered so, that only near infrared radiation is given access to the detector array; the radiation obtained in the second semiconductor detector array is filtered so, that among the radiation of the visible spectrum range, green and red light are given access to the detector array; and the signals obtained from the first and second semiconductor detector arrays and representing the strength of near infrared radiation and the strength of the radiation of the green and red spectrum ranges, are decoded by changing the order of the signals in order to achieve the desired combined false color signal in the camera output.
In another method of the invention, there is utilized a video camera provided with three arrays of semiconductor detectors with a sensitivity range in relation to wavelength extends from the range of visible light to the near infrared range, and where the radiation obtained in the semiconductor detectors is filtered. According
REFERENCES:
patent: 4170987 (1979-10-01), Anselmo et al.
patent: 4751571 (1988-06-01), Lillquist
Hame Tuomas
Rantasuo Markku
Hsia Sherrie
Metjahic Safet
Valtion teknillinen tutkimuskeskus
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