Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1982-12-06
1986-03-11
Coles, Sr., Edward L.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358169, H04N 514
Patent
active
045757585
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for displaying on a viewing screen the output signals from a detector sensitive to radiation.
BACKGROUND
Many methods exist for displaying on a viewing screen an image which has been picked up on a radiation-sensitive detector, e.g., an infrared (IR) detector. The screen is usually of the kind on which is produced an image housing adjacent lines or a raster similar to that used for displaying television pictures.
A video system is known, e.g., from U.S. Pat. No. 3,975,586, in which the output signal from a radiation-sensitive detector is converted to a video signal used for producing an image of the scene in front of the radiation detector. In order to present the loss of small details in the image, which are reproduced by high-frequency components in the video signal, in highlighted portions of the image, which are reproduced by low-frequency components in the video signal with high amplitude, it is proposed according to the above patent that the image contrast shall be improved such that the amplitude of the low-frequency components is limited, while the high-frequency components are left unchanged.
A drawback with the proposed amplitude limitation is that the difference in image intensity which would have been interesting to display cannot be displayed if the intensity falls outside the limitation. For example, if an image contains both sky and ground, and both have high intensity, no difference between these will be visible in the image, and thus the horizon can be invisible, which is detrimental in some cases.
SUMMARY OF INVENTION
It is an object of the invention to provide an improved method for displaying the output of a radiation-sensitive detector.
The invention contemplates that the image intensity will never be over-modulated to black or white without some room being left over for displaying small superposed details in the image, which are reproduced by the high frequency parts of the video signal.
The selected low and high signal levels which are to be paired together with the maximum and minimum output signal of the radiation detector are determined by statistic parameters for the signal values. The distribution curve of the signals are calculated continuously and from it there is selected percentiles, e.g., the 10 percentile and 90 percentile, and the amplification is adjusted such that these correspond to predetermined image intensities. Other points in the distribution curve may also be utilized for adjusting the image intensity. With the method selected, the change in image intensity will be proportional to the change in the output signal of the radiation detector.
When the image contrast in respect of details has been improved according to the above, only noise in the detector output signal should limit enabling the discovery of small weakly contrasting details with the aid of the image.
The method can be extended so that more than two statistic parameters, inter alia medium value, mean value, variance, percentile values, are selected to correspond to certain image intensities, although the relationship between image intensity and the signal it represents will then no longer be proportional.
BRIEF DESCRIPTION OF DRAWINGS
An embodiment of a method in accordance with the invention is next described with reference in to the appended drawings, in which:
FIG. 1 illustrates the relationship between signal value and image intensity in a first case,
FIG. 2 illustrates the relationship between image signal frequency and amplification in the first case,
FIG. 3 illustrates the relationship between signal value and image intensity in a second case,
FIG. 4 illustrates the relationship between image signal frequency and amplification in the second case, and
FIG. 5 is a block diagram of the apparatus for carrying out the method of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION
In one example of a method in accordance with the invention it is assumed that the video signals from a scanning IR de
REFERENCES:
patent: 3975586 (1976-08-01), Chow et al.
patent: 4030125 (1977-06-01), Bedell et al.
patent: 4220972 (1980-09-01), Geokezas et al.
patent: 4262304 (1981-04-01), Faroudja
patent: 4263616 (1981-04-01), Lee
patent: 4414564 (1983-11-01), Hitchcock
Egerod Eskel
Yngvesson Lars Y. A.
Coles Sr. Edward L.
Telefonaktiebolaget LM Ericsson
LandOfFree
Method of displaying on a viewing screen the output signals from does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of displaying on a viewing screen the output signals from, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of displaying on a viewing screen the output signals from will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2193767