JPS6339144B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention applies to television video signals.
It relates to an image gradation conversion device that converts the gradation of an image represented by a television video signal by performing signal processing such as PCM conversion, weight control, and resynthesis. The gradation of the image can be controlled by simple operations and converted to any desired gradation. Generally, when producing a television program, it may be necessary to adjust the tone of the color image represented by each color image signal in order to unify the tone of each image material. Furthermore, when producing a drama program or the like, there are cases where it is desired to pseudo-convert the gradation of an image photographed in the daytime to a gradation representing a night view. In such a case,
If the gradation of an original image could be arbitrarily converted to a desired gradation without degrading the quality of the image, it would be extremely advantageous in program production. However, in the past, it has been considered extremely difficult to arbitrarily convert the gradation of an image represented by a composite color image signal. For example, so-called color correctors configured with analog circuits have been developed; has only a function of correcting part of the gradation, and cannot satisfy the above-mentioned program production requirements. In other words, conventional color correctors extract only color signal components from an input color image signal, change the linearity of the color signal components using an analog circuit to form a correction signal, and convert the original input color image signal into a corrected signal. By adding or subtracting and superimposing,
Although attempts have been made to change the gradation of color image signals within a small range, the following serious functional deficiencies have been pointed out in order to provide a desired image gradation conversion device. That is, (a) the adjustable range of gradation is limited to a narrow range centered on the gradation of the original image. (b) It is impossible to convert an original image into an image whose gradation is significantly different from the original image, which has a different sense of time, weather, or season. (c) It is impossible to convert the gradation of an image taken during the day to make it equivalent to an image taken at night. In addition to these serious functional deficiencies, there were also the following functional deficiencies. In other words, (d) since the correction signal was formed by representing the image signal level with three elements of "gain", "gamma", and "pedestal level", it was difficult to determine the gradation level when specifying the desired gradation level. Level resolution is extremely poor. (e) When one of the three elements mentioned above, for example "gamma" is changed, the other two elements are also affected, causing a change in the overall gradation. (f) The gradation conversion characteristics are continuous, and it is not possible to make the gradation characteristics significantly different by using discontinuous conversion characteristics. (g) The gradation conversion characteristic has a negative region, making it impossible to perform gradation conversion, such as converting a high-level blue sky that forms the background into a low-level night sky. On the other hand, attempts have been made to use digital technology to provide functions lacking in conventional color correctors as described above. for example,
As shown in Figure 1, the image signal is converted to a PCM image signal by analog-to-digital conversion, and then
There is a system in which a PCM image signal is used as an address signal to access data of a desired value written in advance in a random access memory, and weight conversion of the image signal level is performed using a digital system. In the digital color correction circuit shown in FIG. Read out the data as a new signal and
In order for the A converter 4 to reconvert the image signal into an analog format output image signal and take it out, the digital memory address (DMA) control circuit 5 switches the switch 2 to the address signal side from the microcomputer 6 during the vertical retrace period, for example. The new data set by the input/output (I-O) interface circuit 7 is written to the address of the RAM 3 by the DMA control circuit 5 and the microcomputer 6 to create data with desired conversion characteristics. During the subsequent image scanning period, the input PCM
It is accessed by the image signal and read out as a converted output PCM image signal. However, the functions of this digital color correction circuit are actually not much different from those of the above-mentioned analog color corrector, and the following problems arise in achieving a desired image gradation conversion device. That is, (a) As for the gradation conversion characteristic, only a polygonal line approximation set in advance by the microcomputer 6 can be obtained, and it is difficult to obtain any desired conversion characteristic. (b) Random access memory 3 for gradation correction amount
Writing is performed only during the vertical retrace period, but it takes time to calculate the conversion characteristics of the three elements of "gain", "gamma" and "pedestal level" by the microcomputer 6, and the I
There is a time delay of about 30 milliseconds between when the correction amount is set by the -O interface circuit 7 and when the correction amount is actually written into the random access memory 3. (C) A correction amount that provides a resolution of 10 steps or more for each of the three elements of "gain,""gamma," and "pedestal level" to the amount of correction for gradation, and provides smooth correction between each step. If the response time of the microcomputer 6 is calculated, the response time of the microcomputer 6 increases dramatically, making it difficult to perform high-precision conversion of gradation. (D) Since color correction is mainly used, the correction signal is added to and subtracted from the input image signal and superimposed as described above for the analog color corrector, and therefore, significant gradation conversion is required. Equally difficult. Furthermore, a device has been developed in which any desired conversion characteristics can be obtained by setting the gradation conversion characteristics using a light pen method, but the device configuration is complicated and expensive, and it is difficult to operate. Due to its nature, it was also impractical. An object of the present invention is to eliminate the above-mentioned conventional drawbacks, convert a television video signal into a PCM image signal, and then change the gradation of the image represented by the image signal to any desired gradation by a simple operation. An object of the present invention is to provide an image gradation converting device having a relatively simple configuration and capable of converting image gradation. That is, the image gradation conversion device of the present invention is based on a new principle and has a wide range of gradation conversion functions, and converts an analog television video signal into an n-bit, preferably 8-bit configuration.
Convert it to a PCM image signal, form 2 ⁿ types of image level identification signals independent from the PCM image signal, apply independent variable weighting to each of these 2 ⁿ types of image level identification signals, and convert it into an analog format. In the process of reconverting to an image signal, the gradation of the original image can be directly converted to the desired gradation by setting the degree of weighting independently to suit the desired gradation. An analog-to-digital converter for converting an input image signal into an n-bit PCM image signal;
2 ^{n types of level identification signals are formed, each corresponding to the 2 n levels} of image signal levels to be included in the PCM image signal, and a value suitable for the desired gradation is assigned to each of the 2 ⁿ types of level identification signals. a gradation conversion unit comprising a gradation processor that performs respective calculations with the 2 ⁿ types of process control signals;
2 ⁿ types of process control signals. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings, with reference to embodiments of a gradation conversion unit and a process control unit for arbitrary image gradation conversion. First, a configuration example centered on the analog control type gradation conversion section of the image gradation conversion device of the present invention will be explained in the second section.
As shown in the figure. In the configuration shown in the figure, an input image signal is supplied to an A-D converter 1 in the same way as in the conventional case to convert it into an n-bit, for example, 8-bit PCM image signal, and the input image signal is sent to a conversion instruction pulse generator 8. We also supply In the conversion instruction pulse generator 8, each signal processing process of decomposition, weight conversion, and resynthesis for the PCM image signal requires:
Repetition frequency f _cpov phase-locked to PCM image signal
(MHz) conversion instruction pulse is generated, and the above-mentioned A
The conversion instruction pulse is applied to the gradation conversion section consisting of the -D converter 1 and the subsequent decoding/demultiplexer 9 and gradation processor 4' to control the respective signal processing. Next, the n-bit PCM image signal from the A-D converter 1 is supplied to the decoding/demultiplexer 9, and the entire level range of the analog image signal obtained by decoding the PCM image signal is decoded.
PCM image signals of sample values corresponding to each level step divided equally into 2 ⁿ stages, for example 2 ⁸ = 256 stages, are decoded and output from 2 ⁿ , for example 256 output terminals provided for each level step. , 2 ⁿ types of high level “1” digital signals indicating that the image signals of each level step have arrived,
For example, extract it as 256 types of level identification signals,
These 2 ⁿ types of level identification signals are supplied to the next gradation processor 4' in parallel for each level step. In the gradation processor 4', under the control of the process control signal set in the processor controller 10, each time 2 ⁿ types of level identification signals are received, they are assigned and set to the respective level identification signals. Analog image signals of respective predetermined signal levels each having a desired weight specified by the analog type process control signal are sequentially output at the timing of the conversion instruction pulse. The timing component of the conversion instruction pulse is waved and removed from these sequential analog image signals, and an analog image signal having a desired new gradation is obtained. Next, arbitrary conversion of image gradation by the apparatus having the configuration shown in FIG. 2 will be explained. First, as mentioned above, the input image signal is A-D
In converter 1, under the control of a conversion instruction pulse with a repetition frequency f _cpov (MHz), an n-bit configuration
The n-bit PCM signal is converted to a PCM image signal.
The image signal sequentially includes 2 ⁿ types of level identification signals corresponding to 2 ⁿ levels of image signal levels for each sample in accordance with the image content. For convenience of explanation, the image signal is converted to an 8-bit PCM image signal that is considered to be optimal for digitization, and n = 8, and for simplicity, the level range of only the image signal portion of the input image signal is expressed only for the video portion. Taking as an example the case in which signal processing is performed with the input analog image signal being limited to 0% to 100%, the 8-bit PCM image signal obtained as the conversion output of the A-D converter 1 has a difference between it and the input analog image signal. The correspondence shown in Table 1 is obtained. As can be seen from this table, the input analog image signal is converted into an 8-bit PCM image signal with a resolution of 100/2 ⁿ =100/2 ⁸ ≈0.4% IRE. Note that "%IRE" mentioned above is the image signal level in % when only the level range of the image signal is taken as 0 to 100% of the signal level range from the tip of the synchronization pulse to the white peak in the television video signal. This corresponds to the unit ``IRE'' expressed in .

【table】

Claims (1)

[Scope of Claims] 1. An analog-to-digital converter that converts an input image signal into an n-bit PCM image signal, 2 ⁿ levels each corresponding to 2 ⁿ stages of image signal levels to be included in the n-bit PCM image signal a decoding demultiplexer that forms different types of level identification signals; and a gradation system that multiplies each of the 2 ⁿ types of level identification signals and 2 ⁿ types of process control signals each having a value matching a desired gradation level. An image gradation conversion device comprising: a gradation conversion unit including a processor; and a process control unit that forms the 2 ⁿ types of process control signals. 2. An operation unit having a plurality of potentiometers arranged in parallel to set a desired image gradation conversion characteristic; 2. The image gradation conversion apparatus according to claim 1, wherein said process control section includes an interpolation section that forms a process control signal. 3. A memory device in which a plurality of 2 ⁿ types of process control signal groups are written in advance, each corresponding to the 2 n levels of image signal levels to be included in the output image signal, and a memory device in which a plurality of 2 ⁿ types of process control signal groups are written in advance, each corresponding to the 2 n stages of image signal levels to be included in the output image signal, and 2. The image gradation conversion apparatus according to claim 1, wherein the process control section is provided with a selector that arbitrarily selects and reads out the suitable process control signal group. 4 Writing data of a plurality of types of conversion patterns each representing a plurality of different types of image gradation conversion characteristics, and reading the process control signal from the memory device using a conversion pattern selector capable of selecting a desired conversion pattern. 2. The image gradation conversion device according to claim 1, wherein the image gradation conversion device is configured to output an image. 5. In the image gradation conversion device according to claim 1, a plurality of the image gradation conversion units are arranged in parallel, and the plurality of image gradation conversion units are arranged in parallel, and the plurality of image gradation conversion units are Image gradation conversion of the input composite color image signal is performed by performing desired image gradation conversion in each image gradation conversion unit and then synthesizing the plurality of types of component image signals. An image gradation conversion device characterized by: