Television – Image signal processing circuitry specific to television – Brightness control
Reexamination Certificate
1998-05-28
2001-03-13
Peng, John K. (Department: 2714)
Television
Image signal processing circuitry specific to television
Brightness control
C348S663000, C348S552000, C348S712000, C348S673000
Reexamination Certificate
active
06201583
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an image signal input apparatus for inputting to a processing unit an image signal formed by superimposing a brightness signal on a color subcarrier wave having a generally sine waveform.
2. Description of Related Art
Conventional image signals, such as video signals, television signals and the like, are formed by superimposing a brightness signal on a color subcarrier wave that indicates the color of each pixel; the brightness signal varies in strength with the brightness of each pixel. These video signal may be produced by a digital camera. A conventional apparatus for inputting these image signals to a processing unit, such as a computer or the like, converts the image signal into digital data by sampling the image signal at a frequency that is 4 or 8 times the frequency (fsc) of the color subcarrier wave (i.e., a frequency of 4 fsc or 8 fsc). The conventional apparatus then inputs all the data obtained by sampling to the computer or the like.
The data obtained by sampling at a frequency of 4 fsc or 8 fsc can easily be demodulated into an original image signal. Therefore, a processing unit, such as a computer, extracts a brightness signal from the demodulated image signal, performs a preview operation of displaying a corresponding image in a monochrome view and, when a capture key is operated during the preview operation, performs a capture operation of storing in a memory the image signal available at the time of the operation of capture key.
However, the quantity of data obtained by sampling at a frequency of 4 fsc or 8 fsc is large. Therefore, a long processing time is required to input the data to the computer, perform the preview operation based on the data, and optionally perform the capture operation. Therefore, the progression of the preview operation is slower than the progression of the image signal unless the number of frames displayed during preview is considerably reduced. In addition, the displayed monochrome images are displayed after a significant delay time because of the unequal progression of the preview operation and the image signal. Consequently, it is very difficult, if not impossible to precisely input an instruction to perform image signal capture at a desired time by operating a capture key. Further, during processing, operations other than the preview and capture operations are performed on the image signal. Therefore, the problem of a long processing time is compounded. Thus, a reduction in such processing time is needed.
SUMMARY OF THE INVENTION
Accordingly, it is an aspect of the present invention to enable fast input processing of an image signal. Particularly, the present invention provides fast input processing of a brightness signal component of an image signal input to a processing unit which may or may not be a separate unit.
According to the present invention, there is provided an image signal input apparatus for inputting to a processing unit an image signal formed by superimposing a brightness signal on a color subcarrier wave. The processing unit may or may not be separated from the image signal input apparatus. The subcarrier wave has a generally sine waveform. The image signal input apparatus includes a sampling unit that samples the image signal at a predetermined interval and a brightness signal extracting unit that extracts the brightness signal from the image signal based on the image signal obtained by sampling performed by the sampling unit. The image signal input apparatus also includes an input unit which inputs the brightness signal extracted by the brightness signal extracting unit to the processing unit.
In the image signal input apparatus of the invention, an image signal is sampled at a predetermined interval by the sampling unit. The brightness signal extracting unit extracts the brightness signal from the image signal obtained by sampling. The extracted brightness signal is input to the processing unit by the input unit. As a result, the data input to the processing unit does not contain data regarding the color subcarrier wave. Therefore, the quantity of data is reduced. Consequently, it is possible to input only that portion of the image signal relating to the brightness signal to the processing unit. Furthermore, since the image signal input to the processing unit is processed into a state where the brightness signal is already extracted, operation of the processing unit requires less time. Thus, according to the invention, it is possible to quickly process the brightness signal and accurately perform other operations, for example, a preview operation.
The image signal input apparatus of the invention may have the further following features. The color subcarrier wave may be superimposed on the brightness signal using a quadrature two-phase modulation method, an amplitude modulation method or a phase modulation method. Additionally, the sampling unit may sample the image signal at a frequency that is n times the frequency of the color subcarrier wave, where n is a natural number greater than 1. The brightness signal extracting unit may extract the brightness signal by determining a mean of the n number of values of the image signal which are consecutively obtained by sampling performed by the sampling unit.
If values of a sine wave signal at various points in time are sampled at a frequency that is n times the frequency of the sine wave signal, where n is a natural number greater than 2, the mean of the n number of values obtained consecutively by sampling becomes “0”. In other words, the mean becomes equal to the value of the oscillation center of the sine wave signal. Since the color subcarrier wave is generally a sine waveform, the locus of the oscillation centers coincides with the brightness signal. Therefore, the brightness signal is extracted by sampling the image signal at a frequency that is n times the frequency of the image signal and determining the mean of the n number of values of the consecutively sampled image signal. Thus, the brightness signal can be extracted from the image signal by a simple operation of obtaining a finite number of sample data and determining a mean thereof. The amount of data to be input to the processing unit is reduced to a fraction of one nth the amount of data that would be input without performing the averaging operation described above. Therefore, these features of the invention achieve the advantage of a further increase in input processing speed of the brightness signal and further improvement of the accuracy and speed of various processing operations.
The natural number n may be 4 or 8. If the sampling of the video signal is performed at a frequency that is 4 times or 8 times the frequency of the color subcarrier wave (fsc), i.e., a frequency of 4 fsc or 8 fsc, the data obtained by sampling can easily be demodulated into the original image signal. This sampling method has been used conventionally.
The image signal input apparatus may include an input unit capable of selectively inputting either the brightness signal extracted by the brightness signal extracting unit or the image signal obtained by sampling by the sampling unit to the processing unit in accordance with a selection instruction.
In this embodiment, the input unit selectively inputs either the brightness signal extracted by the brightness signal extracting unit or the image signal obtained by sampling performed by the sampling unit, to the processing unit in accordance with a selection instruction. Therefore, the input processing of the brightness signal can be performed quickly and the image signal carrying data specifying colors of the pixels can also be input to the processing unit in accordance with the selection instruction. Thus, this embodiment advantageously enables the input of the image signal carrying data regarding colors of the pixels to the processing unit as well. If the sampling is performed at a frequency of 4 fsc or 8 fsc in this embodiment, the demodulation of the sampled image signal into the original im
Brother Kogyo Kabushiki Kaisha
Desir Jean W.
Oliff & Berridg,e PLC
Peng John K.
LandOfFree
Image signal input apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image signal input apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image signal input apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2483352