JPH0738801A - Image pickup device - Google Patents

Abstract

PURPOSE:To easily confirm whether or not the exposure of the image pickup device of an electronic still camera, a camcorder, etc., is proper. CONSTITUTION:The image pickup device is equipped with an optical system 10 and an image pickup system 20 and the video signal from the image pickup element of the image pickup system 20 is recorded on a recording medium. Further, the device is provided with a histogram calculating circuit 40 which calculates the distribution state of the luminance level of the video signal from the image pickup element in a specific section and a display means 60 which displays the calculated distribution state of the luminance level in the form of a graph.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus for recording a picked-up video signal on a recording medium such as a magnetic tape or a semiconductor memory.

[0002]

2. Description of the Related Art An electronic still camera is known in which information obtained from a solid-state image pickup device such as a two-dimensional CCD image sensor is electrically processed and recorded as a still image on a magnetic floppy disk or a solid-state memory. Has been.

The electronic still camera basically uses the same diaphragm and shutter as those of a photographic camera using a silver salt film, and an automatic exposure mechanism (automatic exposure mechanism) for automatically adjusting the diaphragm and the shutter based on the light quantity of the image pickup light ( Appropriate exposure is performed by the AE or the program AE (see, for example, Journal of the Television Society, Vol. 39, No. 9).

[0004]

By the way, in the case of imaging with a video camera in a studio such as a broadcasting station, the camera exposure can be determined by observing a video output signal (so-called EE image) from the camera on a waveform monitor. It is possible to easily confirm whether it is appropriate.

However, in the case of outdoor shooting with a video camera, the waveform monitor cannot be used easily, and it is not possible to easily confirm whether or not the exposure is appropriate at the time of shooting.

In some of the electronic still cameras described above, the video output signal cannot be derived, and in such a case, the waveform monitor cannot be used. With this type of camera, even if the above-mentioned automatic exposure mechanism is used, the suitability of the exposure is confirmed after the shooting, so it is inevitable that a still image with a defective exposure is obtained. It was

Further, the dynamic range of the image sensor, that is, the exposure permissible range (latitude) is narrower than that of a silver salt film, and correction is difficult. Therefore, even if automatic exposure adjustment is performed, a subject that is out of the AE pattern is detected. Then, the proper exposure may not always be obtained.

In this case, there is a problem in that details of a highlight portion or a shadow portion of a subject are not reproduced due to overexposure or underexposure, that is, so-called white blur or black blur occurs, and the quality of a reproduced image deteriorates.

An object of the present invention is to provide an image pickup apparatus capable of easily confirming properness of exposure during image pickup.

[0010]

In order to solve the above-mentioned problems, an image pickup apparatus according to a first aspect of the present invention comprises an optical system 10 and an image pickup system 20 in correspondence with the reference numerals of the embodiments described later. In the image pickup apparatus for recording the video signal from the image pickup device 21 of this image pickup system in the recording medium, the calculating means 40 for calculating the distribution state of the luminance level in the predetermined section of the video signal from the image pickup device 21, and this calculation. Means 40
The display means 60 or 26 for displaying the distribution status of the brightness levels calculated by the above is provided.

[0011]

According to the present invention having the above-mentioned structure, the distribution state of the brightness level of the picked-up image, which is effective for determining whether or not the exposure is appropriate, is displayed on the display means. Therefore, the user can grasp the situation of white blur or black blur from the distribution of the brightness level of the display means, and can judge the appropriateness of the exposure.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment in which the image pickup apparatus according to the present invention is applied to an electronic still camera will be described below with reference to FIGS.

FIG. 1 shows the overall construction of an embodiment of the present invention, and FIGS. 2 and 3 show the construction of the essential parts thereof.
In FIG. 1, 10 is an optical system, 20 is an imaging system, and 30 is a system control circuit (microcomputer).

The optical system 10 includes a lens 11 and a diaphragm mechanism 1.
2. The optical shutter 13 is provided, and the aperture mechanism 12 and the optical shutter 13 are accompanied by the control mechanisms 14 and 15 represented as motors, respectively, and the exposure amount of the imaging light passing through the lens 11 is controlled.

The image pickup system 20 includes a CCD solid-state image pickup device 21.
Will be installed. The output of the image pickup device 21 is supplied to the analog signal processing circuit 22 and subjected to predetermined signal processing,
In the A / D converter 23, for example, one pixel sample is 8
It is converted into a bit digital signal and supplied to the digital signal processing circuit 24. Then, the digital video signals (luminance signal Sdy, color signal Sdc) for one screen from the digital signal processing circuit 24 are stored in the frame memory 25.

Then, the digital video signal S25 read from the frame memory 25 is recorded in a recording medium, which is the semiconductor memory 1 in this example.

Although not shown, the still image recorded in the semiconductor memory 1 is electronically reproduced by a still video player or reproduced as a hard copy by a still video printer.

The system control circuit 30 includes a diaphragm mechanism 12
An exposure setting key 31 for setting the aperture value and the speed of the shutter 13 and a shutter release key 32 are connected. Then, the system control circuit 30 sends an exposure control signal Sex to the aperture control mechanism 14 and the optical shutter control mechanism 15.
And the read control signal Srd is supplied to the frame memory 25.

In this embodiment, a histogram calculation circuit 40, a display circuit 50, and a liquid crystal display device 60 are further provided. The histogram calculation circuit 40 is supplied with the digital luminance signal Sdy of the digital video signal from the signal processing circuit 24. The histogram calculation circuit 24 calculates the distribution status of the luminance level of each pixel in a certain section of an image for one screen, for example, one frame or a specific partial section thereof.

That is, in the case of 8-bit pixel data, its digital level is any one of "0" to "255", so that there are a number of pixels having 256 levels. Or calculate.

FIG. 2 shows an embodiment of the histogram calculation circuit 40. That is, in this example, the histogram calculation circuit 40 includes a decoder 41 and a plurality of counters 42.
a to 42n. In the case of 8-bit pixel data, when calculating how many pixels each having 256 levels are present, the number of counters is 256, and the counter 42a counts pixel data of level "0". Then, the counter 42b counts the pixel data of level "1", ..., And the counter 42n counts the pixel data of level "255".

Further, for example, when displaying the distribution status of the brightness level in a histogram having a 16-step bar graph, the decoder 41 truncates the lower 4 bits of the digital brightness signal Sdy from the signal processing circuit 24. , The number of counters 42a to 42n is 16.

The count value outputs of the counters 42a to 42n of the histogram calculation circuit 40 are supplied to the display circuit 50. Then, the display circuit 50 displays the count value of each counter on the liquid crystal display device 60 as a bar graph.

Next, the histogram display operation of the embodiment shown in FIG. 1 will be described with reference to FIG. In the case of this example, in the photometric state in which the two-stage shutter release key 32 is depressed by one stage, the optical shutter 13 is appropriately opened and closed by the control signal from the system control circuit 30, and the aperture mechanism 12 is opened by the AE. The aperture value is set to an appropriate value according to the control, the image pickup device 21 is exposed to a predetermined amount, and reading from the frame memory 25 is prohibited.

In the histogram calculation circuit 40, each of the counters 42a to 42n is started at the start of the frame period of the video signal.
Is cleared, and the video signal is input to the decoder 41 pixel by pixel in the frame section or a fixed section of the frame section. In this example, all pixels in one frame section are input to the decoder 41. Then, a specific output terminal of the decoder 41 is selected in accordance with the brightness level of each pixel in the section, and the output from this terminal is supplied to the corresponding counter 42i, and the counter 42i (i = a to n) outputs. The value is incremented by 1.

The above operation is repeated during one frame period, and when the one frame period ends,
The count values of the counters 42a to 42n are transferred to the display circuit 50.

In the display circuit 50, each counter 42
The count value of a to 42n is read, the count value is written in the display memory in the form of a bar graph display, and the liquid crystal display element 6 is formed as a bar graph as shown in FIG.
Display at 0.

When the exposure is proper, the digital luminance signal S
Since the number of pixels in which the level of dy is "0" and its vicinity and "255" and its vicinity is small, the lengths of the bars at both ends are short as shown in FIG. 3A.

On the other hand, when overexposure or underexposure causes white or black blurring, as shown in FIGS. 3B and 3C, level "255" and its vicinity, and level "0" and The bar graph portions corresponding to the levels in the vicinity become significantly long.

By observing the shape of the bar graph on the liquid crystal display element 60, the photographer can easily grasp the situation regarding the brightness of the screen of the picked-up image, and easily determine the appropriateness of the exposure. You can Therefore, the photographer can manually correct the exposure to obtain a proper exposure if necessary.

Further, as shown by the broken line in FIG. 1, by supplying the output signal of the histogram calculation circuit 40 to the microcomputer 30 as a light amount detection signal,
The diaphragm mechanism 12 may be automatically corrected. That is, for example, the exposure may be corrected so that the pixels of the level “0” or the level “255” are eliminated or become minute.

In the embodiment shown in FIG. 1, the luminance histogram is displayed on the liquid crystal display element 60. However, by using the light emitting diodes arranged in a plurality of columns, the luminance histogram as shown in FIG. You may make it display a histogram.

Next, another embodiment in which the image pickup apparatus according to the present invention is applied to a video camera will be described with reference to FIGS. FIG. 4 shows the overall construction of another embodiment of the present invention, and FIG. 5 shows the construction of the essential parts thereof. In both of these figures, parts corresponding to those in the above-mentioned FIG.

In the embodiment shown in FIG. 4, a display signal forming circuit 50A and a matrix circuit 70 are provided in addition to the histogram calculating circuit 40. Reference numeral 26 is an electronic viewfinder, which is composed of, for example, a liquid crystal display element.

In this example, the display signal forming circuit 50A displays a display signal Shg displayed as a line graph on the display screen from the distribution status of the brightness levels of the pixels in one frame section calculated by the histogram calculation circuit 40. Is formed. The display signal Shg and the digital luminance signal Sdy are supplied to the matrix circuit 70, and either one of them is selectively taken out or appropriately mixed, and so-called superimposing is performed. The key signal Sky for this superimposing is also formed in the forming circuit 50A and supplied to the matrix circuit 70 as a control signal.

The output of this matrix circuit 70 is the D / A
It is converted into an analog video signal by the converter 27 and supplied to the viewfinder 26. This viewfinder 2
As shown in FIG. 7, which will be described later, an image and a line graph are superimposed and displayed on the screen 6.

In this embodiment, the histogram calculation circuit 4
The number of 0 counters 42a to 42n (see FIG. 2) is, for example, 256, and the 8-bit digital luminance signal Sdy from the signal processing circuit 24 is processed without rounding down the lower bits.

As shown in FIG. 5, the display signal forming circuit 50A is composed of a CPU 51, a display control circuit 52, and a pair of VRAMs 53 and 54. The rest of the configuration is similar to that of the example shown in FIG.

Next, the histogram display operation will be described with reference to FIGS. 6 and 7. In the photometric state for setting the exposure, a predetermined exposure is performed on the image sensor 21 and reading from the frame memory 25 is prohibited by a control signal from the system control circuit 30.

In the histogram calculation circuit 40, similarly to the above, in the frame section of the video signal, the distribution frequency of the brightness level of each pixel for one screen is counted by the counters 42a-4a.
2n is counted, and the count value is transferred to the display signal forming circuit 50A.

In the display signal forming circuit 50A, CP
The U51 reads the count value of each of the counters 42a to 42n, forms a display signal Shg in the form of a broken line graph display from this count value, and writes this display signal Shg to the VRAM 53 through the display control circuit 52. Display control circuit 5
Reference numeral 2 reads out the display signal Shg from the VRAM 53 and supplies it to the matrix circuit 70, forms a key signal Sky for superimposing display, and supplies this signal Sky to the matrix circuit 70.

In the matrix circuit 70, being controlled by the key signal Sky, the digital luminance signal Sdy from the signal processing circuit 24 and the display signal Shg from the display signal forming circuit 50A are appropriately switched and mixed to each other. Imposed.

Therefore, on the screen 26D of the electronic viewfinder 26, as shown in FIG.
S and the line graph HS of the histogram are superimposed and displayed. Therefore, the photographer can simultaneously confirm the composition for photographing and the suitability of exposure.

When the exposure is proper, the digital luminance signal S
Since the number of pixels having a dy level of “0” or “255” is small, the values at both ends are small as shown in FIG. 6A.

On the other hand, when the exposure is excessive or insufficient, white blur or black blur occurs, and as shown in FIGS.
Peaks occur at one end or the other end, corresponding to levels of 55 "to" 0 ", respectively.

Therefore, the photographer can easily determine the appropriateness of the exposure by observing the shape of the line graph on the viewfinder 26, and if necessary, manually set the appropriate exposure. Can be corrected.

Also in this example, as shown by the broken line in the figure, the diaphragm mechanism 12 is automatically corrected by supplying the output signal of the histogram calculation circuit 40 to the microcomputer 30 as a light amount detection signal. You may do it.

Further, in the example of FIG. 4, the monochrome electronic viewfinder is used. However, the color electronic viewfinder is used to display the line graph as a histogram in a specific color so as to be superimposed on the captured image. Good.

Further, although the present invention is applied to the electronic still camera having the electronic viewfinder in the above-mentioned embodiments, the recording medium is a magnetic tape, and the video signal is recorded on the magnetic tape by the rotary head. The present invention can also be applied to a camera-integrated VTR that records as an oblique track.

[0050]

As described above, according to the present invention, the histogram of the luminance level of the pixel is calculated for a certain section of the captured image and the histogram is displayed as a bar graph, or the electronic viewfinder is used. Since it is displayed so as to be superimposed on the captured image and the distribution state of the brightness level of the captured image is displayed in a graph, it is possible to easily confirm whether or not the exposure is appropriate at the time of capturing the image.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of an image pickup apparatus according to the present invention.

FIG. 2 is a block diagram showing a configuration of a main part of an embodiment of the present invention.

FIG. 3 is a diagram for explaining the operation of the embodiment of the present invention.

FIG. 4 is a block diagram showing the configuration of another embodiment of the present invention.

FIG. 5 is a block diagram showing a partial configuration of another embodiment of the present invention.

FIG. 6 is a diagram for explaining the operation of another embodiment of the present invention.

FIG. 7 is a diagram for explaining the operation of another embodiment of the present invention.

[Explanation of symbols]

 10 Optical system 12 Aperture 20 Imaging system 21 Imaging device 26 Electronic viewfinder 40 Histogram calculation circuit 50 Display circuit 50A Display signal forming circuit 60 Liquid crystal display device 70 Matrix circuit

Claims (5)

[Claims] 1. An image pickup apparatus comprising an optical system and an image pickup system, wherein the image signal from the image pickup element of the image pickup system is recorded on a recording medium, wherein the luminance of the image signal from the image pickup element in a predetermined section. An image pickup apparatus comprising: a calculating unit that calculates a level distribution condition; and a display unit that displays the brightness level distribution condition calculated by the calculating unit. 2. The image pickup apparatus according to claim 1, further comprising a video display element for displaying a video signal from the image pickup element of the image pickup system, and at a predetermined section of the video signal from the image pickup element. Display control means is provided for superimposing the distribution status of the brightness level calculated by the calculation means for calculating the distribution status of the brightness level on the video signal from the image sensor of the imaging system and displaying the superimposed signal on the video display element. An imaging device characterized by the above. 3. The image pickup apparatus according to claim 1, wherein the diaphragm of the optical system is adjusted according to the distribution state of the brightness level. 4. A memory for storing at least one screen of video signal is provided, and a still image composed of one field or one frame of video signal stored in the memory is provided on the recording medium according to an operation input. The image pickup apparatus according to claim 1 or 2, which is recorded as. 5. The image pickup apparatus according to claim 1, wherein the recording medium is a magnetic tape, and the video signal is recorded as an oblique track on the magnetic tape by a rotary head.