JP2001008104A - Wide dynamic range image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wide dynamic range image pickup device capable of realizing the high connection of highlight gradation by post processing after photographing and minimizing the uselessness of circuit constitution. SOLUTION: The wide dynamic rage image pickup device quantizes a high sensitive video signal 12 expressing an image generated by a solid state image pickup device 10 by 10-bit resolution through an analog/digital(A/D) conversion circuit 16 and quantizes a low sensitive video signal 14 by 8-bit resolution through an A/D conversion circuit 18. The quantized high sensitive video signal data 20 are recorded in a recording medium 26 so as to correspond to low sensitive video signal data 22. A synthetic circuit 52 forms a wide dynamic range video signal 56 by additionally synthesizing both the data 20, 22. Consequently the wide dynamic range video signal 56 is obtained by simple circuit constitution and a complete image with high completeness equal to a silver salt photographic system can be obtained by executing exposure correction and gradation compression in post processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wide dynamic range image pickup apparatus for outputting a video signal output from a solid-state image pickup device in a wide dynamic range, and particularly to an image pickup apparatus such as an electronic camera, a digital camera, a video camera, and an image scanner. It is about.

[0002]

2. Description of the Related Art In a photographing system for obtaining a photographic print from a silver halide photographic negative film, as shown in FIG. 10, image information of such a wide exposure region is utilized as shown in FIG. After once recording on a negative film, post-processing cuts out the image information of the proper print reproduction area from the recording exposure area, so that a large exposure correction other than a proper completed image, that is, fine adjustment is required. It is possible to obtain an image in a state of not performing. This feature has an effect that, for example, even if exposure fails on the camera side during photographing, an appropriate print can be obtained by correction in post-processing. Also, for example, the main gradation area can maintain the same gradation, and the high luminance area and the low luminance area on both sides of the main gradation can be subjected to gradation compression so that the entire area can be accommodated in the print reproduction area. Therefore, for example, it is possible to avoid the reproduction of an image in which a portion of a picture such as a cheek of a person is overexposed.

In an imaging apparatus having a solid-state imaging device such as an electronic still camera, correction processing such as exposure correction and gradation compression is performed in post-processing because the dynamic range of the solid-state imaging device is narrower than that of a silver halide photographic negative film. It was difficult. As can be seen from FIG. 11, the solid-state imaging device captures only a small portion of the wide range of subject brightness. This has the disadvantage that failure due to improper exposure during photographing is difficult to correct in post-processing, and the connection of highlight gradations is poor.

In order to avoid this drawback, a solid-state imaging device having a wide dynamic range has been proposed. For example, Japanese Patent Publication No. 8-34558 discloses a solid-state imaging device such as a charge-coupled device (CCD) in which low-sensitivity light-receiving cells and high-sensitivity light-receiving cells are alternately arranged. The video signals obtained from the two types of light receiving cells having different sensitivities are read from the imaging device independently of each other, and are later combined to form a video signal having a wide dynamic range. Another publication, JP-A-9-181979 and JP-A-9-191099, discloses that the charge accumulation times of the odd-numbered photosensors and the even-numbered photosensors are electrically different from each other by an electronic shutter. A solid-state imaging device in which the ratio of apparent sensitivities is made variable is disclosed, and a video signal having a wide dynamic range is formed by synthesizing such video signals having different sensitivities.

[0005]

The above-mentioned Japanese Patent Application Laid-Open No. 9-181979.
In Japanese Patent Application Laid-Open Publication No. H10-209, video signals of two fields having different sensitivities output from an imaging device are converted into digital signals. As described above, in a silver halide photographic system having excellent reproduction characteristics as a photographic system, image information of a high luminance portion is subjected to gradation compression, so that an image having a preferable gradation can be obtained. This means that in the completed image, the number of gradations assigned to the high-luminance portion whose gradation is compressed is small. Therefore, in the case of a digital image signal, the bit resolution of a signal to be gradation-compressed in a high luminance region may be low. However, none of the above-mentioned prior arts takes into account such a difference in bit resolution between the high luminance region and the low luminance region. Therefore, there is no use in the circuit configuration of the functional part that converts the video signal from the imaging device into a digital signal.

The present invention solves such disadvantages of the prior art, and realizes a wide dynamic range image pickup apparatus capable of realizing good connection of highlight gradations by post-processing after photographing and minimizing waste of circuit configuration. The purpose is to provide.

[0007]

According to the present invention, there are provided input means for receiving a high-sensitivity video signal and a low-sensitivity video signal representing one image generated by a solid-state imaging device, and a high-sensitivity video signal. First signal converting means for quantizing a signal at a first quantization resolution and outputting corresponding high-sensitivity video signal data; and a second quantization means for converting a low-sensitivity video signal to a lower quantization resolution than the first quantization resolution. And a second signal conversion means for outputting corresponding low-sensitivity video signal data by quantizing at a quantization resolution.

According to the present invention, such a signal conversion device may be configured to further include output means for outputting high-sensitivity video signal data and low-sensitivity video signal data in association with each other.

A wide dynamic range image pickup apparatus according to the present invention includes an image pickup means for picking up an image of a field and generating a high-sensitivity video signal and a low-sensitivity video signal representing the field, and a high-sensitivity video signal. First signal conversion means for quantizing at a quantization resolution of 1 and outputting corresponding high-sensitivity video signal data; and a low-sensitivity video signal at a second quantization resolution lower than the first quantization resolution. Second signal conversion means for quantizing and outputting corresponding low-sensitivity video signal data, and output means for outputting high-sensitivity video signal data and low-sensitivity video signal data in association with each other.

The image pickup apparatus further comprises a signal synthesizing means for adding and synthesizing high-sensitivity video signal data output from the output means and corresponding low-sensitivity video signal data to form a video signal having a wide dynamic range. May be included.

The wide dynamic range image pickup apparatus according to the present invention also includes an image pickup means for picking up an image of a field and alternately generating a high-sensitivity video signal and a low-sensitivity video signal representing the field, and the generated image signal. A signal conversion unit that quantizes the video signal and outputs corresponding video signal data; and a signal separation unit that separates high-sensitivity video signal data and low-sensitivity video signal data from the video signal data. The means outputs the separated low-sensitivity video signal data at a lower resolution than the separated high-sensitivity video signal data, and the imaging apparatus further outputs the high-sensitivity video signal data and the low-sensitivity video signal data. You may comprise so that the output means which outputs in association with it may be included.

In the present specification, an imaging device having both a high-sensitivity imaging cell and a low-sensitivity imaging cell is referred to as a wide dynamic range imaging device for convenience.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a wide dynamic range imaging apparatus according to the present invention. Referring to FIG. 1, an embodiment of a wide dynamic range imaging apparatus according to the present invention includes a solid-state imaging device 10 such as a charge-coupled device (CCD) having a wide dynamic range, and outputs a high-sensitivity video signal 12 and Converts low-sensitivity video signal 14 into analog and digital
(A / D) A digital circuit which converts two digital video signals 20 and 22 having different bit resolutions from each other by conversion circuits 16 and 18 and records them on a video signal recording medium 26 such as a memory card by a recording circuit 24. An image capturing device such as a still camera. The present invention is not limited to such specific embodiments, but may be effectively applied to other forms, such as electronic cameras, video cameras, image scanners, and the like.

In the present embodiment, the solid-state imaging device 10
This is a line-reading single-plate charge-coupled device. More specifically, as illustrated in FIG.
High-sensitivity (H) imaging cells 30 forming each horizontal line
H and low-sensitivity (L) imaging cells 30L are alternately positioned on each horizontal line, and are half of the horizontal and vertical cell pitch.
This is an imaging device having a so-called honeycomb structure in which the cells 30H and 30L are arranged to be shifted by a length corresponding to.
Although only a small number of imaging cells are shown in FIG. 2 in order to avoid complication, the imaging cell array is actually
Needless to say, a large number of imaging cells are arranged two-dimensionally in 32.

The high-sensitivity imaging cell 30H and the low-sensitivity imaging cell 30L include, for example, on-chip microlenses and / or on-chip filters (neither shown) formed on the surface of the imaging cell array 32. The light transmittance of the former is designed high for the former and low for the latter, or the optical aperture is wide for the former,
By designing the latter narrower,
Can be formed. Or high sensitivity imaging cell 30H
Is equipped with a microlens to condense light, and a low-sensitivity imaging cell
It may be configured so that the microlens is not provided in 30L. Alternatively, for the high-sensitivity imaging cell 30H, the charge sweeping time from the high-sensitivity imaging cell 30H may be shortened, while the low-sensitivity imaging cell 30L may be configured to take a long time.

The charge-coupled device 10 of the embodiment has two horizontal transfer paths 34L and 34H, which are arranged at the ends of the image pickup cell array 32 in the vertical transfer direction, that is, at the bottom edge in FIG. It is arranged. A vertical transfer path 36H for transferring charges in the vertical direction is provided on the horizontal charge sweeping side from the high-sensitivity imaging cell 30H, and a horizontal charge sweeping side from the low-sensitivity imaging cell 30L. Is provided with a vertical transfer path 36L that also transfers electric charges in the vertical direction.

In response to the incident light from the field to the high-sensitivity imaging cells 30H, the electric charges accumulated in these cells 30H respond to a horizontal transfer pulse supplied from a control line 126, which will be described later. The data is transferred to the vertical transfer path 36H as shown by 38H. Similarly, for the low-sensitivity imaging cell 30L, the electric charge accumulated in the low-sensitivity imaging cell 30L in response to the incident light responds to the horizontal transfer pulse, and the vertical transfer path thereof as indicated by the arrow 38L. Transferred to 36L. The electric charges transferred to these two vertical transfer paths 36H and 36L are simultaneously transferred in the horizontal line and sequentially in the vertical direction in response to a vertical transfer pulse also supplied from the control line 126. First, it is transferred to one horizontal transfer path 34L. More specifically, after the accumulated charge of one line corresponding to the high-sensitivity cell 30H reaches one horizontal transfer path 34L, it is simultaneously transferred to the other horizontal transfer path 34H. Next, the charge stored in one line corresponding to the low-sensitivity cell 30L following this is transferred to one horizontal transfer path 34L. Thus, the electric charges of a pair of horizontal lines that arrive at the pair of horizontal transfer paths 34H and 34L in a time-shifted state, that is, two lines corresponding to the high-sensitivity imaging cell 30H and the low-sensitivity imaging cell 30L, respectively. The accumulated charges are simultaneously transferred to the horizontal transfer path 34, respectively.
H and 34L are output one pixel at a time. This video signal
The states of 12 and 14 are schematically shown in FIG. 1 by “H” and “L”, respectively, which are surrounded by rectangles. In this manner, the high-sensitivity video signal and the low-sensitivity video signal are simultaneously output from the outputs 12 and 14 of the solid-state imaging device 10, respectively, in a dot-sequential manner.

Returning to FIG. 1, the two outputs 12 and 14 of the solid state imaging device 10 are connected to two analog / digital conversion circuits 16 and 18, respectively. The one analog-digital conversion circuit 16 connected to the high-sensitivity video signal output 12 has a quantization resolution of 10 bits in this embodiment, and converts the high-sensitivity video signal arriving at the input 12 to a level of 0 to 1023.
Is a signal conversion circuit that converts the digital signal data into digital signal data and outputs the digital signal data from an output 20 thereof. Similarly, the other analog-to-digital conversion circuit 18 connected to the low-sensitivity video signal output 14 has a quantization resolution of 8 bits in this embodiment,
The signal conversion circuit converts the low-sensitivity video signal of the input 14 into digital signal data of levels 0 to 255 and outputs the digital signal data to the output 22 thereof. These outputs 20 and 22 are connected to the inputs of the recording circuit 24.

In the present embodiment, the recording circuit 24 is a data recording device that records the high-sensitivity video signal data 20 and the low-sensitivity video signal data 22 for one image in a video signal recording medium 26 such as a memory card. is there. In a preferred embodiment, low sensitivity video signal data
Reference numeral 22 is recorded in a header part for managing a storage area in which the high-sensitivity video signal data 20 is recorded. In the present embodiment, since the bit resolution of the low-sensitivity video signal data 22 is lower than that of the high-sensitivity video signal data 20, there is an advantage that the required storage area in the recording medium 26 can be small. Such correspondence recording of the high-sensitivity video signal data 20 and the low-sensitivity video signal data 22 is conceptually indicated by an arrow 40 in FIG.

The image pickup apparatus according to the embodiment has a control circuit 124. The control circuit 124 includes a solid-state imaging device
10, connected to the analog-to-digital conversion circuits 16 and 18 and the recording circuit 24 via control lines 126, 128 and 130, respectively, and controlling these circuits to control the solid-state imaging device.
This is an overall control function unit that performs an operation of recording the video signal output from 10 on the recording medium 26. The control circuit 124
A drive signal such as a horizontal and vertical transfer pulse is sent to the imaging device 10 through the control line 126, a video signal is read from the imaging device 10, and the analog / digital conversion circuits 16 and 18 and the recording circuit 24 are operated in synchronization with the video signal. Thus, the two digital video signal data 20 and 22 having different bit resolutions are recorded on the video signal recording medium 26.

In this embodiment, when the analog video signals 12 and 14 are converted into the corresponding digital data, the video signal data 20 with the higher sensitivity is converted into the bit of the video signal data 22 with the lower sensitivity. It is configured to perform A / D conversion at a bit resolution higher than the resolution. This is because, in general, the highlight gradation characteristic in the completed image is soft, does not require a high bit resolution, and the low-sensitivity video signal data 22 contains information about the highlight portion of the picture pattern, that is, the highlight. This is because a lot of information is included. In this embodiment, one of the analog-to-digital conversion circuits 16 has a resolution of 10 bits and the other analog-to-digital conversion circuit 18 has a resolution of 8 bits. It is not limited to a specific value.

A pair of video signals recorded on the video signal recording medium 26 in this manner, ie, high-sensitivity video signal data
20 and the low-sensitivity video signal data 22 are reproduced as a visible image by an image reproducing device 50 as exemplified in FIG. The video signal recording medium 26 such as a memory card is a composite circuit.
Connected to 52. The synthesizing circuit 52 reads a pair of high-sensitivity video signal data 20 and low-sensitivity video signal data 22 for one image from the recording medium 26 to its input 54, adds and synthesizes the two, and generates a video signal having a wide dynamic range. This is a signal synthesis circuit to be formed. The combined output is output 56
The output 56 is used by a utilization circuit 58 such as a printer.
It is connected to the. As an example of the utilization circuit 58, there is a hard copy device such as a printer that prints an image represented by a synthesized video signal on an image recording medium (not shown) such as recording paper. On behalf of or in addition to a printer,
A transmission medium such as a soft copy device such as a liquid crystal display device or a communication line (both not shown) may be connected to the output 56 of the synthesis circuit 52 as the use circuit 58.

The synthesizing circuit 52 synthesizes the high-sensitivity video signal data 20 and the low-sensitivity video signal data 22 for one image obtained at the input 54 as follows. The high-sensitivity imaging cell 30H of the solid-state imaging device 10 is
It has K times the sensitivity of L. Here, K is a positive number greater than one. Referring to FIG. 4, the imaging cell array 32
At step 100, the level value H of the high-sensitivity video signal 22H of a pixel of interest is compared with the synthesis threshold T (step 100). The composite threshold T is the maximum conversion level of the high-sensitivity video signal analog-to-digital conversion circuit 16, that is, “102” in this embodiment.
3 "is fine. The threshold value T does not necessarily have to be the maximum conversion level “1023” of the analog-to-digital conversion circuit 16 for a high-sensitivity video signal, and may be a lower value in consideration of various characteristics such as signal variation and linearity. For example, "100
It may be set to about “0”. That is, it is advantageous to set the value near the value at which the high-sensitivity video signal is substantially saturated.

The fact that the level value H of the high-sensitivity video signal 22H of the target pixel is smaller than "1023" means that the subject corresponding to that pixel has been captured within the dynamic range of the high-sensitivity video signal data 20. . The synthesizing circuit 52 then determines the level value H of such high-sensitivity video signal data 20.
Is output from the output 56 as the output value C as it is (step 101).

In step 100, when the level value H of the high-sensitivity video signal 22H of the target pixel is equal to "1023",
This means that the high-sensitivity video signal data 20 was saturated in the subject portion of the pixel and could not be captured within the dynamic range. Therefore, the synthesizing circuit 52 uses the level value L of the low-sensitivity video signal data 22L of the pixel, and
High sensitivity imaging cell 30H for sensitivity of low sensitivity imaging cell 30L
Multiplied by the ratio of the number of quantization levels of the analog-to-digital conversion circuit 16 for the high-sensitivity video signal to the number of quantization levels of the analog-to-digital conversion circuit 18 for the low-sensitivity video signal, and 2 ^10-8 The value L · K · 2 ^10-8 is output to the output 56 as an output value C (step 103).

This will be described with reference to FIG. 5. The horizontal axis represents subject brightness, and the left vertical axis represents high-sensitivity video signal data.
Taking the levels 0 to 1023 of 20 and the levels 0 to 255 of the low-sensitivity video signal data 22 on the right vertical axis, the level value H of the high-sensitivity video signal 22H of the pixel of interest is plotted as a line 60, The level value L of the low-sensitivity video signal data 22L is represented by a line 62.
Is plotted as Combining both level values H and L as described above in steps 100, 101 and 103 gives
The resulting signal is as shown by dotted line 64. Synthesis circuit
By performing such a synthesizing operation, 52 is compared with a case where only the high-sensitivity video signal 12 is used for reproduction.
Outputs video signal C having double dynamic range
56 can be obtained.

The synthesized signal 56 is input to a utilization circuit 58 such as a printer, and is converted into a print form and used. The utilization circuit 58 may include an image processing circuit that performs exposure correction and gradation correction. In such an application example, the use circuit 58 can cut out a required luminance area of the composite signal C and reproduce it as a completed image.

Incidentally, the solid-state imaging device 10 may of course be a charge-coupled device in which imaging cells are arranged in a square lattice. An example is shown in FIG. In the following description, elements similar to those in the above description are denoted by the same reference numerals. The charge-coupled device 10 of this embodiment has 1
The high-sensitivity imaging cells 70H and the low-sensitivity imaging cells 70L are alternately positioned on the horizontal line, and the imaging cell array 72 in which the imaging cells 70H or 70L having the same sensitivity are arranged at pixel positions in the vertical direction. A vertical transfer path 74H for transferring charges in the vertical direction is provided on the horizontal charge sweeping side from the high-sensitivity imaging cell 70H.
A vertical transfer path 74L for transferring charges in the vertical direction is also provided on the horizontal charge sweeping side from 70L.
In this case, the vertical columns of the high-sensitivity imaging cells 70H and the vertical columns of the low-sensitivity imaging cells 70L have vertical transfer paths 74H and 74H, respectively.
CCD electrodes (not shown) are arranged so that the readout time of the stored charge to the 74L, that is, the readout time of the pixel charge is different between adjacent vertical columns, and finally a pair of horizontal transfer paths 34 are arranged.
These charges are configured to reach H and 34L at the same time.

The electric charge accumulated in the high-sensitivity imaging cell 70H in response to the incident light from the object scene is transferred to the vertical transfer path 74H as indicated by an arrow 76H in response to the horizontal transfer pulse. Similarly, for the low-sensitivity imaging cell 70L, the electric charge accumulated in the low-sensitivity imaging cell 70L in response to the incident light moves to the vertical transfer path 74L as indicated by an arrow 76L in response to the horizontal transfer pulse. Will be transferred. The electric charges transferred to these two vertical transfer paths 74H and 74L are simultaneously transferred in the horizontal line and sequentially in the vertical direction in response to the vertical transfer pulse to form a pair of corresponding horizontal transfer paths. Transferred to 34H and 34L. In this manner, the electric charges of the pair of horizontal lines that have reached the pair of horizontal transfer paths 34H and 34L, that is, the accumulated charges of the two lines corresponding to the high-sensitivity imaging cell 70H and the low-sensitivity imaging cell 70L, are simultaneously transferred to the horizontal transfer paths, respectively. The pixels are output one by one from the paths 34H and 34L.

In the operating state, a video signal representing the scene captured by the solid-state imaging device 10 is supplied to the control circuit 124.
Under the control of, the high-sensitivity video signal data 20 and the low-sensitivity video signal data 22 are input from the outputs 12 and 14 to the corresponding analog / digital conversion circuits 16 and 18, respectively. The analog-to-digital conversion circuit 16 converts the high-sensitivity video signal 12 to a quantization level of any of 0 to 1023 with a resolution of 10 bits and outputs it to its output 20. The other analog / digital conversion circuit 18 converts the low-sensitivity video signal 14 to a quantization level of any of 0 to 255 with 8-bit resolution, and outputs it to an output 22 thereof. The recording circuit 24 records these video signals 20 and 22 on the video signal recording medium 26 in association with each other as a data file of one image.

The digital video signals 20 and 22 recorded on the video signal recording medium 26 are read by the reproducing device 50. The high-sensitivity video signal data 20 read from the recording medium 26 to the synthesizing circuit 52 is added and synthesized in the synthesizing circuit 52 with the corresponding low-sensitivity video signal data 22. That is, FIG.
As described above, the synthesizing circuit 52 adds and synthesizes the video signals one pixel at a time, and when the level value H of the high-sensitivity video signal 22H is smaller than “1023”,
The level value H of 20 is output as it is from the output 56 as the output value C. When the level value H of the high-sensitivity video signal 22H of the pixel is equal to “1023”, the level value L of the low-sensitivity video signal data 22L of the pixel is checked, and this value L is calculated by K ·
2 ^10-8 times the value L · K · 2 ^10-8 as output value C and output 56
Output from The resulting signal 56 thus synthesized
Is input to the utilization circuit 58 and reproduced and used as a visible image such as a print.

In this embodiment, the present invention is applied to a digital still camera that records image data on a video signal recording medium 26 such as a memory card. However, in an application example such as an image scanner, a solid-state imaging device is used. Ten
May be a one-dimensional imaging device, and may be configured to connect the outputs 20 and 22 of the analog / digital conversion circuits 16 and 18 directly to the input of the synthesis circuit 52 instead of the recording circuit 24 and the recording medium 26. .

Incidentally, the solid-state imaging device 10 may be of a type that alternately outputs the high-sensitivity video signal H and the low-sensitivity video signal L in a dot-sequential manner. FIG. 7 shows an embodiment of an imaging apparatus including such a one-line readout solid-state imaging device 80. The solid-state imaging device 80 has a single video signal output 82, and the high-sensitivity video signal H and the low-sensitivity video signal L that are alternately output from the output 82 in a dot-sequential manner are connected to the input of a signal separation circuit 84. You. This solid-state imaging device 80 has an imaging cell array 86 as shown in FIG. 8, and a single horizontal transfer path 34 is provided at the lower edge in the same figure. In this example, a vertical column of high sensitivity imaging cells 70H and a low sensitivity imaging cell
The vertical column of 70L may be at the same position where the stored charge is read out to the vertical transfer paths 74H and 74L, that is, the read time of the pixel charge may be the same between adjacent vertical columns. The charge of the video signal L is configured to reach the single horizontal transfer path simultaneously.

In response to the control signal 132 from the control circuit 124, the signal separation circuit 84 converts the high-sensitivity video signal H and the low-sensitivity video signal L of the analog signals alternately arriving at the input 80 into
This is a signal separation circuit that separates in synchronization with signal reading from the solid-state imaging device 10 and outputs the signals to two corresponding outputs 88 and 90, respectively. The pair of outputs 88 and 90 are respectively connected to the corresponding analog-to-digital conversion circuits 16 and
Connected to 18. The embodiment shown in FIG. 7 is the embodiment described with reference to FIG. 1 except that the solid-state imaging device 80 has a single signal output 82 and a signal separation circuit 84 is provided correspondingly. May be the same as

Referring to FIG. 9, another embodiment of the present invention is shown, in which a single analog-to-digital conversion circuit 92 replaces a pair of analog-to-digital conversion circuits 16 and 18. This embodiment is the same as the embodiment described with reference to FIG. 7, except that this is provided before the signal separation circuit 94. Single analog-to-digital conversion circuit 92
Is a signal conversion circuit for converting a video signal obtained at the output 82 of the solid-state imaging device 80 into corresponding digital data. In the present embodiment, the analog / digital conversion circuit 92
The input signal 82 is quantized with a 10-bit quantization resolution. As in the embodiment shown in FIG. 7, the high-sensitivity video signal H and the low-sensitivity video signal L arrive at the input 82 alternately in a dot-sequential manner, so that both signals are quantized to a 10-bit quantization level. You. The analog-to-digital conversion circuit 92 has an output 96 connected to the input of the signal separation circuit 94.

The signal separating circuit 94 has the same signal separating function as the signal separating circuit 84 in the embodiment shown in FIG.
The difference from the signal separation circuit 84 is that the signal to be handled is digital data and has a function of reducing the bit resolution of the low-sensitivity video signal L as described later. The signal separation circuit 94 controls the control signal 1 from the control circuit 124.
The high-sensitivity video signal H and the low-sensitivity video signal L, which are alternately input to the input 96 in a dot-sequential manner in response to the signal 32, are separated from each other and output to the corresponding two outputs 120 and 122, respectively. It is a processing circuit. At this time, the signal separation circuit 94 removes the lower bits of the low-sensitivity video signal L, that is, two digits in this embodiment, to
The bit resolution of the low-sensitivity video signal L is reduced to 8 bits. The high-sensitivity video signal 120 and the low-sensitivity video signal 122 thus separated by the digital database are recorded on the recording medium 26 by the recording circuit 24 in association with one image.

Although a specific embodiment of the wide dynamic range imaging device according to the present invention has been described, the present invention is not limited to the details of this embodiment, but includes modifications that can be made by those skilled in the art within the scope of the appended claims. For example, in the above embodiment,
Although the sensitivity of the video signal obtained by imaging and synthesized is two types, the sensitivity of the video signal may be three or more types. For example, a charge-coupled device having a structure in which imaging cells having three kinds of sensitivities are arranged for each line and video signals having the respective sensitivities can be simultaneously read may be used. Alternatively, a signal separation circuit that separates three types of video signals read by one line into individual types of signals may be used. These three types of video signals are employed in a completed image as, for example, a video signal in a middle luminance region and video signals in a shadow region and a highlight region on both sides thereof.

The present invention can be applied not only to a solid-state imaging device having an imaging cell having two kinds of sensitivities as in the above-described embodiment, but also to an imaging cell for each of odd and even columns for two interlaced fields. The present invention is also effectively applied to an imaging method in which high-sensitivity and low-sensitivity video signals are obtained by changing the charge accumulation time.

[0039]

As described above, according to the present invention, a video signal having a wide dynamic range can be obtained with a simple circuit configuration by quantizing a plurality of types of sensitivity video signals generated from a solid-state imaging device with different bit resolutions. A signal can be obtained. When such a video signal is recorded on a recording medium, the required storage area is small. Further, by performing exposure correction and gradation compression in post-processing of a video signal having a wide dynamic range, a completed image having a high degree of perfection comparable to that of a silver halide photographic system can be obtained.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an embodiment in which a wide dynamic range imaging device according to the present invention is applied to a digital still camera.

FIG. 2 is an explanatory plan view showing an example of an imaging cell array of the solid-state imaging device in the embodiment shown in FIG.

FIG. 3 is a functional block diagram showing an embodiment of the image reproducing apparatus applied to the embodiment.

FIG. 4 is an operation flowchart for explaining the operation of the combining circuit in the embodiment shown in FIG. 3;

FIG. 5 is a graph for explaining a signal synthesizing operation of the synthesizing circuit shown in FIG. 3;

FIG. 6 is a plan view similar to FIG. 2, showing another example of the imaging cell array of the solid-state imaging device in the embodiment shown in FIG. 1;

FIG. 7 shows another embodiment in which the wide dynamic range imaging device according to the present invention is applied to a digital still camera.
FIG. 2 is a functional block diagram similar to FIG. 1.

FIG. 8 is a plan view similar to FIG. 2, showing an example of an imaging cell array of the solid-state imaging device in the embodiment shown in FIG. 7;

FIG. 9 is a functional block diagram similar to FIG. 1, showing another embodiment of a wide dynamic range imaging device according to the present invention.

FIG. 10 is a graph for explaining a reproduction range of a negative film and a print in a conventional silver halide photographic system.

FIG. 11 is a graph similar to FIG. 10 for explaining a relationship between a subject luminance region and a photographing luminance region by a solid-state imaging device.

[Explanation of symbols]

 10 Solid-state imaging device 16, 18, 92 Analog / digital conversion circuit 24 Recording circuit 32 Imaging cell array 30H, 30L Imaging cell 34, 34H, 34L Horizontal transfer path 52 Synthesis circuit 84, 94 Signal separation circuit

Claims (14)

[Claims] An imaging unit configured to capture an object field and generate a high-sensitivity video signal and a low-sensitivity video signal representing the object field, and convert the high-sensitivity video signal with a first quantization resolution. First signal conversion means for quantizing and outputting corresponding high-sensitivity video signal data; and quantizing the low-sensitivity video signal with a second quantization resolution lower than the first quantization resolution. And a second signal converter for outputting low-sensitivity video signal data. 2. An image pickup means for picking up an image of a field to generate a high-sensitivity video signal and a low-sensitivity video signal representing the field, and converting the high-sensitivity video signal with a first quantization resolution. First signal conversion means for quantizing and outputting corresponding high-sensitivity video signal data; and quantizing the low-sensitivity video signal with a second quantization resolution lower than the first quantization resolution. Signal conversion means for outputting low-sensitivity video signal data, and output means for outputting the high-sensitivity video signal data and the low-sensitivity video signal data in association with each other. Range imaging device. 3. The apparatus according to claim 2, wherein said output means includes recording means for recording said high-sensitivity video signal data and low-sensitivity video signal data on a recording medium in association with each other. Wide dynamic range imaging device. 4. The apparatus according to claim 2, further comprising: combining the high-sensitivity video signal data output from the output means and the corresponding low-sensitivity video signal data to generate a wide dynamic range. An image pickup apparatus comprising a signal synthesizing means for forming a video signal of a range. 5. The apparatus according to claim 4, wherein said signal synthesizing means outputs, when said high-sensitivity video signal is substantially saturated, said low-sensitivity video signal to a second resolution with respect to a second resolution. Multiplying the ratio of the resolution of 1 and the ratio of the sensitivity of the high-sensitivity video signal to the sensitivity of the low-sensitivity video signal to obtain the wide dynamic range video signal, and when the high sensitivity video signal is not substantially saturated Wherein the high-sensitivity video signal is used as the wide dynamic range video signal. 6. The solid-state imaging device according to claim 2, wherein the imaging unit outputs the high-sensitivity video signal and the low-sensitivity video signal to first and second signal conversion units, respectively. An imaging device characterized by including: 7. The apparatus according to claim 2, wherein the imaging means includes a solid-state imaging device that alternately outputs the high-sensitivity video signal and the low-sensitivity video signal. An image pickup apparatus, comprising: a signal separating unit that separates the output high-sensitivity video signal and low-sensitivity video signal from each other and supplies the separated high-sensitivity video signal to the first and second signal conversion units. 8. An image pickup means for picking up an image of an object field and alternately generating a high-sensitivity video signal and a low-sensitivity image signal representing the object field, and quantizing the generated image signal, Signal conversion means for outputting video signal data to be converted, and signal separation means for separating high-sensitivity video signal data and low-sensitivity video signal data from the video signal data. And outputs the low-sensitivity video signal data at a lower resolution than the separated high-sensitivity video signal data. The apparatus further outputs the high-sensitivity video signal data and the low-sensitivity video signal data in association with each other. A wide dynamic range imaging device comprising output means. 9. The apparatus according to claim 8, wherein said output means includes recording means for recording said high-sensitivity video signal data and low-sensitivity video signal data on a recording medium in association with each other. Imaging device. 10. An input means to which a high-sensitivity video signal and a low-sensitivity video signal representing one image generated by a solid-state imaging device are input, and wherein said high-sensitivity video signal is input at a first quantization resolution. First signal conversion means for quantizing and outputting corresponding high-sensitivity video signal data; and quantizing the low-sensitivity video signal with a second quantization resolution lower than the first quantization resolution. Signal conversion means for outputting low-sensitivity video signal data, and output means for outputting the high-sensitivity video signal data and the low-sensitivity video signal data in association with each other. apparatus. 11. The apparatus according to claim 10, further comprising adding and synthesizing the high-sensitivity video signal data output from the output means and the corresponding low-sensitivity video signal data to obtain a wide dynamic range. A signal converter comprising a signal synthesizing means for forming a video signal of a range. 12. The apparatus according to claim 11, wherein said signal synthesizing means outputs, when said high-sensitivity video signal is substantially saturated, said low-sensitivity video signal to a second resolution with respect to a second resolution. Multiplying the ratio of the resolution of 1 and the ratio of the sensitivity of the high-sensitivity video signal to the sensitivity of the low-sensitivity video signal to obtain the wide dynamic range video signal, and when the high sensitivity video signal is not substantially saturated Wherein the high-sensitivity video signal is used as the wide dynamic range video signal. 13. A step of preparing a high-sensitivity video signal and a low-sensitivity video signal representing one image generated by a solid-state imaging device, and quantizing the high-sensitivity video signal with a first quantization resolution. Converting the low-sensitivity video signal into a corresponding high-sensitivity video signal data with a second quantization resolution lower than the first quantization resolution, and converting the low-sensitivity video signal into a corresponding low-sensitivity video signal data. Converting the high-sensitivity video signal data and the low-sensitivity video signal data; and adding and combining the high-sensitivity video signal data and the corresponding low-sensitivity video signal data to obtain a wide dynamic range. Forming a video signal of a range. 14. The method of claim 13, wherein forming the wide dynamic range video signal comprises:
When the high-sensitivity video signal is substantially saturated, the low-sensitivity video signal includes a ratio of a first resolution to a second resolution and a ratio of the high-sensitivity video signal to the low-sensitivity video signal. Multiplying the high sensitivity video signal by the sensitivity ratio to obtain the wide dynamic range video signal, and when the high sensitivity video signal is not substantially saturated, the high sensitivity video signal is used as the wide dynamic range video signal. Characteristic signal conversion method.