JP2001008216A - Image processing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing unit that can obtain a proper exposure image with superior compositing accuracy in dark and bright areas of an object. SOLUTION: The image processing unit is provided with a lens 1, an aperture and mechanism shutter 2, an optical low-pass filter 3, a CCD 4, an A/D converter circuit 5, a color picture/color separation circuit 6, luminance memories 7, 8, chrominance memories 9, 10, a luminance system histogram processing circuit 11, a chrominance system histogram processing circuit 12, an image compositing parameter circuit 13, an image compositing circuit 14, a gradation parameter circuit 15, and a gradation correction circuit 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus for synthesizing a plurality of image data shot by a digital camera or the like to obtain one wide dynamic range image and performing gradation correction.

[0002]

2. Description of the Related Art Digital cameras and video cameras have a solid-state imaging device such as a CCD for generating a video signal representing a captured subject image. The dynamic range of a solid-state imaging device is narrow, and when the brightness difference between a bright portion and a dark portion included in the visual field is large, it is difficult to photograph both portions with proper exposure. For example, if exposure is adjusted to a dark portion, a bright portion will fly white, and if exposure is adjusted to a bright portion, the dark portion will be blackened.

In order to solve such a problem, for example, Japanese Patent Application Laid-Open No. Hei 5-176233, "Image Input Method and Apparatus"
As shown in the figure, a first image in which a dark region of a subject is properly exposed and a second image in which a bright region of the subject is properly exposed are photographed, and a brighter region in the first image is taken. A dynamic range enlargement camera has been proposed which replaces image data belonging to the second image data with a second image data to create a composite image and obtains an appropriate image for a subject having a large difference in brightness between a bright region and a dark region. I have.

[0004]

However, in the conventional image processing apparatus, there are a first image in which a dark area of a subject is properly exposed and a second image in which a bright area is properly exposed. Since the combination of two images is switched by judging only the saturation level of the luminance, there is a problem that the combination accuracy is poor and the image becomes unnatural. As described above, the conventional image processing apparatus is required to improve the accuracy of the composite image.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image processing apparatus capable of obtaining an appropriate exposure image with good synthesis accuracy for dark and bright areas of a subject.

[0006]

To solve this problem, an image processing apparatus according to the present invention samples a video signal input through a lens, an aperture and a mechanical shutter, an optical low-pass filter, a CCD, and converts an analog signal into a digital signal. An A / D converter for converting the signal into a signal, a color processing / color separation circuit for separating the digital video signal into a luminance signal and a color signal, and a short-exposure luminance for storing the luminance signal photographed in the first exposure time A memory, a short-exposure color memory for storing a color signal, a long-exposure luminance memory for storing a luminance signal photographed in the second exposure time, a long-exposure color memory for storing a color signal, and a luminance signal. A luminance system histogram processing circuit that performs frequency analysis and luminance level analysis from the components, a color system histogram processing circuit that performs lightness, saturation, hue analysis and visual characteristic detection from the color signal components, An image synthesis parameter circuit that determines an image synthesis parameter based on information from the degree-based histogram processing circuit and the color-based histogram processing circuit, and an image synthesis circuit that selects and synthesizes an optimal exposure image from long and short exposure images, It is configured to include a gradation parameter circuit that determines a gradation parameter from information from a color histogram processing circuit, and a gradation correction circuit that performs gradation correction using the gradation parameter.

[0007] According to this configuration, it is possible to realize an image processing apparatus capable of obtaining an appropriate exposure image with good synthesis accuracy for a dark region and a bright region of a subject.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 is a lens,
Aperture and mechanical shutter, optical low-pass filter, C
An A / D converter that samples a video signal input through a CD and converts an analog signal into a digital signal;
A color processing / color separation circuit for separating the digital video signal into a luminance signal and a color signal; a short-exposure luminance memory for storing the luminance signal photographed during the first exposure time; A color memory, a long-exposure luminance memory for storing a luminance signal captured during the second exposure time, a long-exposure color memory for storing a color signal, and a luminance system for performing frequency analysis and luminance level analysis from the luminance signal component. A histogram processing circuit;
A color system histogram processing circuit that performs brightness, saturation, hue analysis and visual characteristic detection from color signal components, and an image synthesis that determines image synthesis parameters based on information from the luminance system histogram processing circuit and the color system histogram processing circuit A parameter circuit, an image synthesizing circuit for selecting and synthesizing the optimal exposure image from the long and short exposure images, a gray scale parameter circuit for determining a gray scale parameter from information from the color histogram processing circuit, And a gradation correction circuit for performing gradation correction, so that an appropriate exposure image with good synthesis accuracy can be obtained.

According to a second aspect of the present invention, in the image processing apparatus of the first aspect, an aperture control circuit for performing aperture control;
A luminance memory storing a luminance signal photographed with a first aperture exposure time, a luminance memory storing a luminance signal photographed with a second aperture exposure time, and a frequency component of the luminance memory are compared. A luminance system histogram processing circuit having a distance information analysis unit for detecting a blur component of an edge portion of a human subject and a background to calculate a distance information parameter and improving the accuracy of an image synthesis parameter is provided. And improve the accuracy of the image synthesis parameters.

[0010] The third aspect of the present invention is the first or second aspect.
The image processing apparatus according to claim 1, further comprising a pseudo contour correction circuit that detects an edge portion of a human subject and a background at the time of image synthesis and performs pseudo contour correction on the edge portion. The unnaturalness of the part can be eliminated.

(Embodiment 1) FIG. 1 is a block diagram showing an image processing apparatus according to Embodiment 1 of the present invention, FIG. 2 is a block diagram showing the same histogram processing unit, and FIG. 3 is a block diagram showing the same histogram processing. It is.

In FIG. 1, a lens 1 for capturing an object, an aperture and a mechanical shutter 2, an optical low-pass filter 3, a CCD 4, an A / D circuit 5 for converting a signal converted into an electric signal from an analog signal to a digital signal, A color processing / color separation circuit 6 for separating the digital video signal into a luminance signal and a color signal, a luminance memory (short exposure) 7 for storing a luminance signal photographed in the first exposure time, and a color memory for storing a color signal (Short exposure) 9, a luminance memory (long exposure) 8 for storing luminance signals photographed in the second exposure time, a color memory (long exposure) 10 for storing color signals, frequency analysis and luminance level from luminance signal components A luminance system histogram processing circuit 11 for analyzing, a color system histogram processing circuit 12 for performing brightness, saturation, hue analysis and visual characteristic detection from color signal components, a luminance system histogram process An image synthesizing parameter circuit 13 for determining an image synthesizing parameter based on information from the path 11 and the color system histogram processing circuit 12, an image synthesizing circuit 14 for selecting and synthesizing an optimum exposure image from long and short exposure images, a color system It has a gradation parameter circuit 15 for determining a gradation parameter from information from the histogram processing unit, and a gradation correction circuit 16 for performing gradation correction using the gradation parameter.

The operation of the image processing apparatus configured as described above will be described. First, a subject image passes through a lens 1, an aperture and a mechanical shutter 2, and an optical low-pass filter 3, and is formed on an imaging surface of a CCD 4. The aperture and the exposure time (electronic shutter speed) of the mechanical shutter 2 and the CCD 4 are controlled so as to obtain an appropriate exposure.
Image data imaged on the CCD 4 at the first exposure time is separated into a luminance signal and a color signal by a color processing / color separation circuit 6, and the luminance signal is stored in a luminance signal memory (short exposure) 7. Is done. The color signal is stored in the color signal memory (short exposure).
9 is stored.

Next, the image data photographed during the second exposure time is separated into a luminance signal and a color signal by a color processing / color separation circuit 6, and the luminance signal is stored in a luminance signal memory (long exposure) 8. . The color signals are stored in a color signal memory (long exposure) 10. Here, as shown in FIG. 2, a luminance signal memory (long exposure) 7, a luminance signal memory (short exposure) 8, a color signal memory (long exposure) 9, and a color signal memory (short exposure) 1
0 indicates that the data of the X * Y pixels are accumulated, and i
The image data is divided into blocks of * j pixels, and a histogram process is performed for each block as shown in FIG. 3A shows a histogram of the frequency analysis circuit of the luminance system histogram processing circuit 11, FIG. 3B shows a histogram of the luminance level analysis circuit of the luminance system histogram processing circuit 11, and FIG. 3 shows a histogram of the brightness / saturation / hue detection circuit of FIG. Based on the data, an image composition parameter is created by an image composition parameter circuit 13.

Here, the luminance system frequency component parameter Kf
(X), luminance system luminance level component parameter KY (x),
Assuming that the color system component parameter Kc (x) is used, the calculation formula of the image synthesis parameter K (x) is as follows.

Kf (x) = (Pf1 + 2Pf2 + 3Pf3 +... + NPfn) / (i * j) Ky (x) = (Py1 + 2Py2 + 3Py3 +... + NPyn) / (i * j) Kc (x) = 0.3R + 0.59G + 0.11BR = (Pcr1 + 2Pcr2 + 3Pcr3 +... + NPcrn) / (i * j) G = (Pcg1 + 2Pcg2 + 3Pcg3 +... + NPcgn) / (i * j) B = (Pcb1 + 2Pcb2 + 3Pcb3 +. x) = Kf (x) * Ky (x) * Kc (x) Here, since two types of parameters for short exposure and long exposure are calculated, the image synthesis parameter for short exposure is KS (x ), The image synthesis parameter for long exposure is KL
(X) Assuming that the threshold level for judging proper exposure or abnormal exposure is A, the one closer to the threshold level is judged as proper exposure and selected as follows.

If A ≦ KS (x) ≦ KL (x), select a short-exposure memory. If KS (x) ≦ KL (x) ≦ A, select a long-exposure memory. The image data selected at 14 is synthesized.

Also, each component parameter Kf
Although (x), KY (x), and Kc (x) are calculated from the average value of the histogram, it is also possible to calculate the parameters by converting them into a minimum value, a maximum value, a deviation coefficient and the like. And
The block size of i * j pixels can also be changed, and the edge size of an image or the like can be reduced in block size to increase the synthesis accuracy.

The color histogram processing circuit 12 also performs brightness / saturation / hue analysis and visual characteristic detection. This utilizes the RGB axis (or IQ axis) of the color signal and human visual characteristics. For example, if the color signal is flesh color, the resolution of the human eye is generally high for this color, and an image looks unnatural if the dynamic range of this hue and lightness is narrow. Therefore, when a signal having a specific hue equal to or higher than a certain luminance level is input, it is detected by the above-described color component parameter Kc (x), and the gradation parameter correction circuit 15 calculates the gradation correction coefficient of the luminance for the color. It is generated and corrected by the gradation correction circuit 16.

The first embodiment is according to the first aspect of the present invention, and it is possible to obtain an appropriate exposure image with good synthesis accuracy.

(Embodiment 2) FIG. 4 is a block diagram showing an image processing apparatus according to Embodiment 2 of the present invention. In FIG. 4, components other than the aperture control circuit 17 and the luminance system histogram processing circuit 18 are the same as those of the image processing apparatus according to the first embodiment, and a description thereof will be omitted. In the image processing apparatus according to the first embodiment, the diaphragm and the diaphragm F2.
Aperture control circuit 17 for controlling from 8 to F11; luminance memories 7 and 8 for storing image data captured by different apertures; luminance histogram for comparing image data with different aperture values to obtain distance information of a subject or the like It has a processing circuit 18.

The operation of the image processing apparatus configured as described above will be described. First, in the first embodiment, the aperture and the mechanical shutter 2 are fixed, and the exposure time is variable by the electronic shutter speed.
In, the exposure time is varied by the electronic shutter speed, the aperture, and the mechanical shutter 2. The aperture control is performed by an aperture control circuit 17, and control is possible from F2.8 to F11. The luminance signal photographed during the first exposure time is stored in the luminance memory 7, the color signal is stored in the color memory 9, the luminance signal photographed during the second exposure time is stored in the luminance memory 8,
The color signal is stored in the color memory 10. Here, the image data of the luminance memory 7 and the luminance memory 8 are data of, for example, F2.8 and F11 having different aperture values, and the luminance system frequency analysis is performed by the luminance system histogram processing circuit 20 as in the first embodiment. * Performed in units of j blocks. Here, comparing image data with different aperture values, there is no difference in the frequency component of the subject due to the difference in subject depth, but the background (distant view) is out of focus if the aperture value is small. The frequency component decreases and the frequency component increases as the aperture value increases. Therefore, comparing these two types of frequency component parameters, a short-range image such as a subject and a long-range image such as a background are i *
It can be distinguished as distance information in units of j blocks. Therefore,
This distance information parameter can be added to the image synthesis parameter.

The second embodiment relates to the second aspect of the present invention, in which the luminance system histogram processing circuit 18 also has distance information of a subject or the like, so that an appropriate exposure image with even higher synthesis accuracy can be obtained. .

(Embodiment 3) FIG. 5 is a block diagram showing an image processing apparatus according to Embodiment 3 of the present invention. The configuration other than the false contour correction circuit 19 is the same as that of the image processing apparatus described in the first and second embodiments, and thus the description is omitted. The image processing apparatuses according to the first and second embodiments include a pseudo contour correction circuit 19 that performs contour correction on the edge portions of the human subject and the background. The operation of the image processing apparatus configured as described above will be described. First, distance information between a human subject and a background is known in units of i * j blocks by comparing first and second image data shot with different aperture values in the second embodiment. On the other hand, the contour correction of the edge portion of the person subject or the like is performed by the pseudo contour correction circuit 19.

The third embodiment relates to the third aspect of the present invention, and by having the pseudo contour correction circuit 19 together, it is possible to eliminate the unnaturalness of the edge portion of the synthesized image such as a human subject.

[0026]

As described above, according to the present invention, it is possible to obtain an image having a wide dynamic range with good synthesizing accuracy even when the contrast of the image is large. Can be eliminated. Further, it is possible to realize gradation correction in accordance with human visual characteristics.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating an image processing apparatus according to a first embodiment of the present invention;

FIG. 2 is a block diagram showing a histogram processing unit according to the first embodiment of the present invention;

FIG. 3 is a block diagram showing histogram processing according to the first embodiment of the present invention;

FIG. 4 is a block diagram illustrating an image processing apparatus according to a second embodiment of the present invention;

FIG. 5 is a block diagram showing an image processing apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 lens 2 diaphragm and mechanical shutter 3 optical low-pass filter 4 CCD 5 A / D circuit 6 color processing / color separation circuit 7 luminance memory (short exposure) 8 luminance memory (long exposure) 9 color memory (short exposure) 10 color memory ( 11) luminance system histogram processing circuit 12 color system histogram processing circuit 13 image composition parameter circuit 14 image composition circuit 15 gradation parameter circuit 16 gradation correction circuit 17 aperture control circuit 18 luminance system histogram processing circuit 19 pseudo contour correction circuit

Continued on the front page F term (reference) 5C022 AA13 AB12 AB17 AC42 AC52 AC54 AC56 5C065 AA01 AA03 BB48 CC01 CC02 CC08 CC09 DD02 EE12 EE18 GG18 GG21 GG30 5C066 AA01 AA11 BA13 CA07 CA08 DD07 EA07 EA11 EC02 GA01 KA00 KE03 KE07 KE19 KL13 KM02

Claims (3)

[Claims] An A / D converter that samples a video signal input through a lens, an aperture and a mechanical shutter, an optical low-pass filter, a CCD, and converts an analog signal into a digital signal, and converts the digital video signal into a luminance signal. A color processing / color separation circuit for separating into color signals, a short exposure luminance memory for storing a luminance signal photographed in a first exposure time, a short exposure color memory for storing a color signal, and a second exposure A long-exposure luminance memory for storing a luminance signal photographed in time, a long-exposure color memory for storing a color signal, a luminance histogram processing circuit for performing frequency analysis and luminance level analysis from the luminance signal component, and a color signal component From the color system histogram processing circuit that performs brightness, saturation, hue analysis and visual characteristic detection, and information from the luminance system histogram processing circuit and the color system histogram processing circuit. An image synthesizing parameter circuit for determining an image synthesizing parameter, an image synthesizing circuit for selecting and synthesizing an optimal exposure image from long and short exposure images, and a floor for determining a tone parameter from information from a color histogram processing circuit. An image processing apparatus comprising: a tone parameter circuit; and a tone correction circuit that performs tone correction using the tone parameter. 2. An aperture control circuit for controlling the aperture, a luminance memory for storing a luminance signal obtained by photographing the aperture with a first aperture exposure time, and a luminance signal obtained by photographing the aperture with a second aperture exposure time. A distance information analysis unit for comparing the frequency components of the luminance memory and the frequency components of the luminance memory to detect the blur component of the edge portion of the human subject and the background, calculate the distance information parameter, and improve the accuracy of the image synthesis parameter. The image processing apparatus according to claim 1, further comprising a luminance system histogram processing circuit. 3. A pseudo contour correction circuit for detecting an edge portion of a human subject and a background at the time of image synthesis and performing pseudo contour correction on the edge portion.
An image processing apparatus as described in the above.