JP3639370B2 - Video camera - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a video camera, and more particularly to a video camera which is applied to, for example, a digital video camera and which processes a digital video signal corresponding to an optical image given to an image sensor through an optical lens by a signal processing means.
[0002]
[Prior art]
This type of digital video camera is generally expensive. One way to solve this is to use an inexpensive optical lens.
[0003]
[Problems to be solved by the invention]
However, in an inexpensive lens, there is a problem that the amount of incident light and the amount of transmitted light are uneven depending on the position through which the optical image is transmitted, that is, the light amount characteristic is deteriorated, thereby deteriorating the luminance characteristic.
Therefore, a main object of the present invention is to provide a video camera capable of improving the luminance characteristics of a video signal even when an inexpensive lens is used.
[0004]
[Means for Solving the Problems]
The video camera according to the present invention is compatible with an imaging device that generates charges corresponding to an optical image incident through an optical lens, an output unit that outputs video data corresponding to the charges generated by the imaging device, and a light quantity characteristic of the optical lens. A lookup table in which multiplier data to be stored is stored corresponding to each pixel position of the image sensor, reading means for reading out the multiplier data from the lookup table corresponding to the pixel position of each charge output from the image sensor, and output means First multiplication means for multiplying the output video data by the multiplier data read by the reading means, and signal processing for performing predetermined processing on the video data multiplied by the multiplier data by the first multiplication means and outputting luminance data Means for extracting edge components of luminance data output from the signal processing means, and extracted by the extracting means. Second multiplying means for multiplying the edge component multiplied by the multiplier data read by the reading means, and adding means for adding the edge component obtained by multiplying the multiplier data by the second multiplying means to the luminance data output from the signal processing means Is provided.
[0005]
[Action]
The image sensor generates a charge corresponding to the optical image incident through the optical lens. Video data corresponding to the electric charge generated by the image sensor is output from the output means. The look-up table stores multiplier data corresponding to the light quantity characteristics of the optical lens corresponding to each pixel position of the image sensor, and the reading means looks up corresponding to the pixel position of each charge output from the image sensor. Read multiplier data from the table.
The first multiplication unit multiplies the multiplier data read by the reading unit by the video data output from the output unit, and the signal processing unit performs predetermined processing on the video data multiplied by the multiplier data by the first multiplication unit. To output luminance data. The edge component of the output luminance data is extracted by the extracting means. The extracted edge component is multiplied by the multiplier data read by the reading means by the second multiplying means. The edge component multiplied by the multiplier data by the second multiplication means is added to the luminance data output from the signal processing means by the addition means.
[0006]
【The invention's effect】
According to the present invention, since so as to correct the luminance characteristic of the image data by multiplying the multiplier data into video data, thereby improving the brightness characteristics of the video data, even when using an inexpensive optical lens.
If the extraction means and the second multiplication means are further provided, the amplitude characteristic of the edge component is also corrected, so that the resolution can be enhanced.
[0007]
The above object, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.
[0008]
【Example】
Referring to FIG. 1, a digital still camera 10 of this embodiment includes an optical lens 12, and an optical image of a subject captured thereby is received in a light receiving unit 16 of a CCD (Charge Coupled Device) 14 of 640 pixels × 480 pixels. Irradiated. When viewed from the irradiation direction of the optical image, the optical lens 12 and the light receiving unit 14 have a positional relationship as shown in FIG. Further, the light quantity characteristic and OTF (Optical Transfer Function) characteristic of the optical lens 12 when a uniform white plane is imaged are expressed as shown in FIGS. That is, if the ratio of the transmitted light amount to the incident light amount at the center of the optical lens 12 is 100%, the ratio decreases toward the periphery, and the ratio at the position of the radius of 3 mm is 40%. Further, the ratio of OTF at the center is 88%, and the ratio gradually decreases toward the periphery.
[0009]
The CCD 14 is supplied with the CCD control signal output from the timing generator / signal generator (TG / SG) 16, whereby the charges accumulated in the light receiving unit 16 are transferred in the vertical direction and in the horizontal direction. The electric charge is read out one scanning line at a time. The read charges are subjected to correlated double sampling in a CDS (Correlation Double Sumpling) / AGC (Automatic Gain Controll) circuit 20 and the gain is automatically adjusted to generate an analog video signal. The analog video signal is converted into a digital video signal by the A / D converter 22 and supplied to the multiplier 24.
[0010]
On the other hand, the look-up table 26 has the same number of pixels as the CCD 14, that is, 640 × 480 addresses, and multiplier data corresponding to the light quantity characteristics of the optical lens 12 is written at addresses corresponding to the respective pixel positions. Yes. The TG / SG circuit 18 reads out the charge from the CCD 14 and at the same time supplies the lookup table 26 with a horizontal address signal and a vertical address signal corresponding to the pixel position where the charge has been stored. Accordingly, multiplier data corresponding to the horizontal address signal and the vertical address signal is read from the look-up table 26, and this data is multiplied by the digital video signal by the multiplier 24.
[0011]
The data characteristics written in the lookup table 26 are shown in FIG. Thus, (horizontal address, vertical address) = (320, 240), that is, the data value at the center address is “64”, and the data value increases toward the periphery, and addresses (0, 0), (0 , 640), (480, 0) and (480, 640) have data values of “160”. 2 and FIG. 3, when the data value “64” means a gain of 1.0 times, the data value “160” corresponding to the four corners of the CCD 14 means a gain of 2.5 times. The multiplier data characteristic of the lookup table 26 is opposite to the light quantity characteristic of the optical lens 12. Accordingly, the multiplier 24 outputs a digital video signal with improved luminance characteristics.
[0012]
The digital video signal is separated into a luminance signal and a chrominance signal by the signal processing block 28, and the chrominance signal is output as it is, but the luminance signal is given to the adder 30 and the aperture filter 32 having the characteristics shown in FIG. In the aperture filter 32, an edge component is extracted from the luminance signal, and this is multiplied by output data from the lookup table 26 by the multiplier 34. Since the amplitude characteristic of the edge component output from the aperture filter 32 is proportional to the OTF characteristic shown in FIG. 4, the edge data deteriorated around the optical lens 12 by multiplying the edge component by the multiplier data of the lookup table 26. The amplitude of the component is corrected, thereby improving the sense of resolution around the optical lens 12. At this time, the edge component around the lens is overcorrected by using the data of the look-up table 26 having the characteristics shown in FIG. The feeling of resolution is improved as compared with the case where correction is not performed. The edge component corrected by the multiplier 34 is added to the luminance signal by the adder 30 and output.
[0013]
According to this embodiment, a digital video signal whose luminance and resolution are deteriorated around the optical lens is multiplied by the multiplier data read from the lookup table 26, and the edge data of the luminance signal is multiplied by the same data. Therefore, even when an inexpensive optical lens is used, it is possible to improve the luminance characteristics and resolution of the digital video signal.
[0014]
In this embodiment, the digital still camera has been described. However, the present invention can be applied to a normal digital video camera.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of the present invention.
FIG. 2 is an illustrative view showing a positional relationship between an optical lens and a CCD light receiving unit.
FIG. 3 is a graph showing light quantity characteristics of an optical lens.
FIG. 4 is a graph showing OTF characteristics of an optical lens.
FIG. 5 is a graph showing data characteristics written in a lookup table.
FIG. 6 is a graph showing frequency characteristics of an aperture filter.
[Explanation of symbols]
10 ... Digital still camera 12 ... Optical lens 14 ... CCD
18 ... TG / SG
24, 34 ... Multiplier 26 ... Look-up table 32 ... Aperture filter

Claims (1)

An image sensor that generates an electric charge corresponding to an optical image incident through an optical lens;
Output means for outputting video data corresponding to the charge generated by the image sensor;
A look-up table in which multiplier data corresponding to the light quantity characteristic of the optical lens is stored corresponding to each pixel position of the image sensor ;
Reading means for reading out the multiplier data from the lookup table corresponding to the pixel position of each charge output from the imaging device;
First multiplication means for multiplying video data output from the output means by multiplier data read by the reading means;
Signal processing means for performing predetermined processing on the video data multiplied by the multiplier data by the first multiplication means and outputting luminance data;
Extraction means for extracting an edge component of luminance data output from the signal processing means;
A second multiplying unit for multiplying the edge component extracted by the extracting unit by the multiplier data read by the reading unit; and the luminance data output from the signal processing unit is converted into the multiplier data by the second multiplying unit. A video camera comprising adding means for adding multiplied edge components.

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