JP2001024953A - Solid-state imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically which the linear transforming operation from/to logarithmic transforming operation of an electric signal against the incident light of an area sensor corresponding to the luminance of an object to pick up an image. SOLUTION: When the luminance of an object detected by a luminance signal sent from an area sensor 3 is higher than a certain fixed value (700 cd/m2, for example), a switching discriminating circuit 4 discriminates that the area sensor 3 is to perform the logarithmic transforming operation. Corresponding to the discrimination of this switching discriminating circuit 4, a switching signal is sent from a switching signal generating circuit 5, and the area sensor 3 performs the logarithmic transforming operation. When the luminance of the object detected by the luminance signal sent from the area sensor 3 is lower than a certain fixed value (700 cd/m2, for example), the switching discriminating circuit 4 discriminates that the area sensor 3 is to perform the linear transforming operation. Corresponding to the discrimination of this switching discriminating circuit 4, a switching signal is sent from the switching signal generating circuit 5, and the area sensor 3 performs the linear transforming operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device having an area sensor capable of performing linear conversion and logarithmic conversion of an electric signal with respect to incident light, and more particularly to a single area sensor which performs a linear conversion operation and a logarithmic conversion operation. The present invention relates to a solid-state imaging device that can perform switching.

[0002]

2. Description of the Related Art Conventionally, an area sensor in which photosensitive elements such as photodiodes are arranged in a matrix outputs a signal obtained by linearly converting the luminance of light incident on the photosensitive element. An area sensor that performs linear conversion in this manner (hereinafter, referred to as a “linear sensor”) is, for example,
By adjusting the aperture of the lens, the adjustment is performed so that the photosensitive element that captures the brightest part (highlight part) of the subject can output an electric signal having a level of about 90% of the maximum level. By using such a linear sensor, the minimum value in the luminance distribution of the subject is Lmin [cd / m ² ] and the maximum value is Lmax
[Cd / m ² ], the luminance range of the subject Lmax /
If Lmin is a narrow range of two digits or less, information on the subject can be captured with rich gradation.

On the other hand, the present applicant has proposed a photosensitive element for generating a current corresponding to the amount of incident light, a MOS transistor for inputting the current, and a bias for biasing the MOS transistor to a state where a subthreshold current can flow. And an area sensor (hereinafter, referred to as a “LOG sensor”) that converts the current from the photosensitive element into a logarithm (see Japanese Patent Application Laid-Open No. 3-192664). When such a LOG sensor is adjusted so that a photosensitive element that captures an image of the brightest part (highlight part) of a subject can output an electric signal having a level of about 90% of the maximum level, the luminance range Lmax /
It is possible to capture information of a subject whose Lmin is in a wide range of 5 to 6 digits.

[0004]

In the above linear sensor, the brightness range in which an image can be captured is as narrow as about two digits, so that the brightness of the subject becomes bright due to factors such as direct sunlight on the subject.
When the bright portion exceeds the level that can be handled by the photosensitive element and overflows, information on the bright portion exceeding this level cannot be captured, and a phenomenon called overexposure occurs. In order to avoid this overexposure, if the luminance range that can be captured is shifted to the bright part side so that the information of the bright part can be captured, the information of the dark part cannot be captured. Occur.

On the other hand, the output characteristic of the LOG sensor shows a logarithmic function as shown in FIG. Therefore, when this LOG sensor is used, gradation in a high-luminance part tends to be poor. For example, for a bright subject, it is possible to capture both information of a dark part and a bright part. For a subject, there is a problem that the gradation of a bright part is poor.

[0006] In view of the above problems, an object of the present invention is to provide a solid-state imaging device that can always perform good imaging regardless of the state of brightness of a subject. Another object of the present invention is to provide a solid-state imaging device that can automatically switch between a linear conversion operation and a logarithmic conversion operation of an electric signal with respect to incident light of an area sensor. It is another object of the present invention to provide a solid-state imaging device in which one area sensor performs the linear conversion operation and the logarithmic conversion operation. Still another object of the present invention is to provide a solid-state imaging device having a simple configuration.

[0007]

According to a first aspect of the present invention, there is provided a solid-state imaging device which generates an electric signal corresponding to the amount of light incident on pixels arranged in a matrix. A sensor for outputting an electric signal serving as image information of a first field from pixels of odd-numbered rows of the area sensor, and then outputting an electric signal serving as image information of a second field from pixels of even-numbered rows of the area sensor In the solid-state imaging device that performs imaging by repeating the operation of performing the operation, the operation state of each pixel in the area sensor is changed into a first state in which the electric signal is linearly converted with respect to an incident light amount and output, and a first state. Second logarithmically converted and output
State, and when the image information of the first field is output from the pixels arranged in the odd-numbered rows of the area sensor, the image information is output from the pixels arranged in the even-numbered rows of the area sensor. Based on the electrical signal
Further, when the image information of the second field is output from pixels arranged on even-numbered rows of the area sensor, the image information is output based on electric signals output from pixels arranged on odd-numbered rows of the area sensor. The operation state of each pixel which outputs an electric signal serving as image information of the next field in the area sensor is switched.

The solid-state imaging device according to the second aspect has an area sensor that generates an electric signal according to the amount of light incident on the pixels arranged in a matrix, and serves as image information of a first field. In a solid-state imaging device that performs imaging by repeating an operation of outputting an electric signal from pixels in an odd-numbered row of the area sensor and then outputting an electric signal serving as image information of a second field from pixels in an even-numbered row of the area sensor. The operation state of each pixel in the area sensor includes a first state in which the electric signal is linearly converted with respect to an incident light amount and output, and a second state in which natural logarithmically converts and outputs the electric signal. And when the image information of the first field is output from the pixels arranged in odd rows of the area sensor, the image information is arranged in even rows of the area sensor. Obtaining the luminance information of the object from the electric signal output from the element, and when the image information of the second field is output from the pixels arranged on the even rows of the area sensor, Obtain the luminance information of the subject from the electric signal output from the arranged pixels, and according to the luminance information, determine the operation state of each pixel that outputs an electric signal serving as image information of the next field in the area sensor. It is characterized by switching.

According to such a solid-state imaging device, as described in claim 3, when it is determined from the luminance information that the luminance of the subject is low, an electric signal serving as image information of the next field in the area sensor is provided. The operation state of each pixel that outputs a signal is set to the first state, and when it is determined that the luminance of the subject is bright based on the luminance information, an electric signal serving as image information of the next field in the area sensor is output. By providing switching means for setting the operation state of each pixel to the second state, in a dark state where the luminance range of the entire subject is narrow, a high-quality image with rich gradation is bright and the luminance range of the entire subject is wide. In this state, it is possible to capture a high-definition image with a depth without whiteouts or blackouts.

According to a fourth aspect of the present invention, there is provided the solid-state imaging device according to the third aspect, wherein the switching means includes a switch.
A switching signal serving as a voltage signal of a value is generated, and the operating state of each pixel in the area sensor is switched by the switching signal. In this manner, the operation state of each pixel can be switched by changing the bias of the element provided for each pixel in the area sensor.

According to a fifth aspect of the present invention, there is provided a solid-state imaging device having an area sensor for generating an electric signal according to the amount of light incident on pixels arranged in a matrix, and an electric signal serving as image information of a first field. After outputting from the pixels of the odd-numbered rows of the area sensor, the solid-state imaging device performs imaging by repeating an operation of outputting an electric signal serving as image information of the second field from the pixels of the even-numbered rows of the area sensor. The operation state of each pixel in the area sensor is switched between a first state in which the electric signal is linearly converted with respect to the amount of incident light and output, and a second state in which the natural signal is converted into a natural logarithm and output. When the image information of the first field is output from the pixels arranged in the odd-numbered rows of the area sensor, the pixels arranged in the even-numbered rows of the area sensor are enabled. Ri detects the luminance range of the subject than the luminance information of the object obtained from the electrical signal output, also
When the image information of the second field is output from the pixels arranged on the even rows of the area sensor, the luminance information of the subject obtained from the electric signals output from the pixels arranged on the odd rows of the area sensor is used. A brightness range detection unit for detecting a brightness range of a subject is provided, and an operation state of each pixel that outputs an electric signal serving as image information of a next field in the area sensor is switched according to the brightness range of the subject. Features.

According to the solid-state imaging device having such a configuration,
It is possible to switch between the first state with good gradation and the second state in which an image of a subject having a wide luminance range can be captured according to the luminance range of the subject. Further, when the luminance range of the subject is narrow, the operation state of each pixel that outputs an electric signal serving as image information of the next field in the area sensor is set to the first state, and When the luminance range is wide, the operation state of each pixel that outputs an electric signal serving as image information of the next field in the area sensor is set to the second state, so that the gradation characteristic is obtained when the luminance range of the entire subject is narrow. , And a high-quality image with a depth that is free from overexposure or black spots in a state where the luminance range of the entire subject is wide.

According to a seventh aspect of the present invention, in the solid-state imaging device according to the fifth or sixth aspect, the brightness range detecting means sequentially changes the level of the electric signal sent from the area sensor. The maximum value and the minimum value are detected by comparison, and the operation state of the pixel in the area sensor is set to the first state or the second state according to the difference between the maximum value and the minimum value of the level of the electric signal. Switching determining means for determining whether or not a switching signal for switching an operation state of a pixel which outputs an electric signal serving as image information of a next field in the area sensor is generated in accordance with a result determined by the switching determining means. Signal generating means.

In such a solid-state imaging device, the value of the bias voltage applied to the element in each pixel is changed by making the switching signal a binary voltage signal. Thereby, the operation of each pixel can be switched to the first state or the second state.

According to a ninth aspect of the present invention, in the solid-state imaging device according to any one of the first to eighth aspects, a pixel for outputting an electric signal serving as the luminance information in the area sensor is provided. It is characterized by operating in the second state. By operating in the second state in which the electric signal is converted into a natural logarithm with respect to the amount of incident light and output, luminance information can be favorably obtained from a subject in a wide luminance range.

According to a tenth aspect of the present invention, in the solid-state imaging device according to any one of the first to ninth aspects, each pixel provided in the area sensor has a DC voltage applied to a first electrode. A transistor including an applied photosensitive element, a first electrode, a second electrode, and a control electrode, wherein the first electrode and the control electrode are connected to a second electrode of the photosensitive element, and an output current from the photosensitive element flows into the transistor. The operation of each pixel is switched between a first state and a second state by changing a potential difference between a first electrode and a second electrode of the transistor.

According to an eleventh aspect of the present invention, in the solid-state imaging device according to any one of the first to ninth aspects, each pixel provided in the area sensor has a DC voltage applied to a first electrode. An applied photosensitive element, a first electrode, a second electrode, and a control electrode, wherein the first electrode is connected to a second electrode of the photosensitive element, an output current from the photosensitive element flows in, and a second electrode And a transistor to which a control electrode is connected, and by changing a potential difference between a first electrode and a second electrode of the transistor, the operation of each pixel is switched between a first state and a second state. It is characterized by switching.

According to a twelfth aspect of the present invention, in the solid-state imaging device according to any one of the first to ninth aspects, each pixel provided in the area sensor has a DC voltage applied to a first electrode. An applied photosensitive element, a first electrode, a second electrode, and a control electrode; a DC voltage is applied to the control electrode; the first electrode is connected to a second electrode of the photosensitive element; And a transistor into which an output current flows from the first and second transistors. The operation of each pixel is switched between a first state and a second state by changing a potential difference between a first electrode and a second electrode of the transistor. It is characterized by.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS <First Embodiment> An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of a main part of a solid-state imaging device used in the present embodiment. FIGS. 2 and 4 are block diagrams showing an example of the structure of the area sensor provided in the solid-state imaging device of the present invention. FIG. 3 is a circuit diagram showing an example of a configuration of a pixel in the area sensor shown in FIG. FIG. 6 is a circuit diagram showing an example of a configuration of a pixel in the area sensor shown in FIG.

A solid-state imaging device 1 shown in FIG. 1 includes an objective lens 2, an area sensor 3 for outputting an electrical signal that has been subjected to logarithmic conversion or linear conversion according to light incident through the objective lens 2, An electric signal output from the sensor 3 is input, and based on the electric signal, the luminance of the subject is detected to determine whether to perform the logarithmic conversion operation or the linear conversion of the area sensor 3 and to generate a switching determination circuit 4. A switching signal generating circuit 5 for transmitting a switching signal for switching between the logarithmic conversion operation and the linear conversion operation of the area sensor 3 to the area sensor 3 according to the determination signal; and an electric signal transmitted from the area sensor 3 And a processing unit 6.

The signal processed by the processing unit 6 is output from the output terminal 91 to the outside of the solid-state imaging device 1 and is used for various purposes such as recording on a recording medium and outputting to a display device.
In addition, it is also supplied from the output terminal 92 to the finder 21. The electric signal transmitted from the area sensor 3 to the processing unit 6 is hereinafter referred to as “image data”.
The electric signal sent to the switching determination circuit 4 from
This is called a “luminance signal”.

An example of the configuration of the area sensor 3 provided in the solid-state imaging device having such a configuration will be described with reference to FIG. In the figure, Ga11 to Gamn and Gb11
Gbmn indicate pixels arranged in a matrix by being arranged in odd rows and even rows, respectively. Reference numeral 7 denotes a vertical scanning circuit, and odd-numbered rows 9-1 and 9-
2, ..., 9-n, even rows 10-1, 10-2, ...
・ 10-n is sequentially scanned.

Reference numeral 8 denotes a horizontal scanning circuit, which includes pixels Ga11 to G11.
amn to output signal lines 11-1, 11-2,..., 11
-M are sequentially derived to the final signal line 14, and the photoelectric conversion signals derived from the pixels Gb11 to Gbmn to the output signal lines 12-1, 12-2,..., 12-m. The converted signals are sequentially derived to the final signal line 15.
13 is a power supply line. Also, the signal line 14 and the signal line 1
5 is provided with a connection switching unit 16 for switching the connection to a luminance signal line 17 connected to the switching determination circuit 4 (FIG. 1) and an image data line 18 connected to the processing unit 6 (FIG. 1).

For each pixel, the odd rows 9-1 and 9-
2, ..., 9-n, even rows 10-1, 10-2, ...
.., 10-n, output signal lines 11-1, 11-2,.
, 11-m, output signal lines 12-1, 12-2,.
, 12-m and the power supply line 13 as well as other lines (for example, a clock line and a bias supply line) are connected, but these are omitted in FIG.

The output signal lines 11-1, 11-2,...
N-channel MOS transistor Qa every 11-m
, Qam, and the output signal line 12-
M of N channels every 1, 12-2,..., 12-m
The OS transistors Qb1, Qb2,.
One is provided as shown in the figure. Transistor Qa
, Qam are connected to output signal lines 11-1, 11-2, ..., 11-m, respectively, the source is connected to the final signal line 14, and the gate is connected to the final signal line 14. It is connected to a horizontal scanning circuit 8. The drains of the transistors Qb1, Qb2,..., Qbm are connected to output signal lines 12-1, 12-2,. , And the gate are connected to the horizontal scanning circuit 8.

As described later, an N-channel fourth MOS transistor T4 for switching is provided in each pixel. Here, the transistor T4 selects a row, and the transistors Qa1 to Qam and the transistors Qb1 to Qbm select a column.

In the area sensor 3 having such a configuration, the pixels Ga11 to Gamn are scanned by the vertical scanning circuit 7 via the odd rows 9-1 to 9-n, and the transistors Qa1 to Qam are sequentially scanned by the horizontal scanning circuit 8. Turn ON and output signal line 1
The electric signal derived from 1-1 to 11-m is derived to the signal line 14. If the signal line 14 is connected to the image data line 18 by the connection switching unit 16, an electric signal for one field output from the signal line 14 is sent to the processing unit 6 (FIG. 1) as image data. .

At this time, the pixels Gb11 to Gbmn are simultaneously scanned by the vertical scanning circuit 7 via the even rows 10-1 to 10-n, and the transistors Qb1
To Qbm are sequentially turned on to output signal lines 12-1 to 12-12.
The electric signal led to −m is led to the signal line 15.
Now, since the signal line 14 is connected to the image data line 18 by the connection switching unit 16, the signal line 15 is connected to the luminance signal line 1.
7 is connected. Therefore, the electric signal led out to the signal line 15 is sent to the switching determination circuit 4 (FIG. 1) as a luminance signal.

As described above, the image data for one field from the pixels Ga11 to Gamn is sent to the processing unit 6, and the luminance signals from the pixels Gb11 to Gbmn are sent to the switching determination circuit 4. The signal line 14 is connected to the luminance signal line 17 and the signal line 15 is connected to the image data line 1 by the unit 16.
8 is connected. When the connection of the signal lines 14 and 15 is switched by the connection switching unit 16, one of the pixels Gb11 to Gbmn is reset.
The image data for the field is sent to the processing unit 6, and the luminance signals from the pixels Ga11 to Gamn are sent to the switching determination circuit 4.

As described above, the area sensor 3 includes the pixels Ga11 to Gamn arranged in odd rows and the pixels Gb11 arranged in even rows.
To Gbmn are used as an interlaced system in which the electric signals are alternately output as image data for each field. However, in this area sensor, all pixels are read every field.
The connection is switched so that the electric signal of each pixel in the row that outputs image data is output to the image data line 18 as image data, and the electric signal of each pixel in the row that does not output image data is output to the luminance signal line 17 as a luminance signal. The output is switched by the section 16.

Further, the configuration of the pixels Ga11 to Gamn and the pixels Gb11 to Gbmn in the area sensor 3 will be described with reference to FIG. In FIG. 3, a pn photodiode PD forms a photosensitive section (photoelectric conversion section). The anode of the photodiode PD is a first MOS
The drain and gate of the transistor T1, the gate of the second MOS transistor T2, and the third MOS transistor T
3 is connected to the drain. The source of the transistor T2 is connected to the drain of the fourth MOS transistor T4 for row selection. The source of the transistor T4 is an output signal line 11 (this output signal line 11
1-2, ..., 11-m, or 12-1, 12-2,
.., Corresponding to 12-m). still,
Each of the transistors T1, T2, T3, and T4 is an N-channel MOS transistor and has a back gate grounded.

The DC voltage VPD is applied to the cathode of the photodiode PD. On the other hand, the signal φVPS is applied to the source of the transistor T1, and one end of the capacitor C is connected to the source of the transistor T2. The other end of capacitor C is supplied with signal φVPS. A DC voltage V RB is applied to the source of the transistor T3, and a signal φVRS is input to its gate. Signal φD is input to the drain of transistor T2. The signal φV is input to the gate of the transistor T4. In this embodiment, the signal φVPS is 2
The voltage for operating the transistors T1 and T2 in the subthreshold region is set to a low level, and a voltage substantially equal to the DC voltage VPD is set to a high level.

In the pixel having such a configuration, the signal φV
By switching the voltage value of the PS to change the bias of the transistor T1, an electric signal (hereinafter, referred to as a "photocurrent") that the photodiode PD outputs an output signal led to the output signal line 11 according to incident light. Can be realized by natural logarithm conversion and by linear conversion. Hereinafter, each of these cases will be briefly described.

(1) A case where a photocurrent is converted into a natural logarithm and output. First, the operation when the signal φVPS is at the low level and the transistors T1 and T2 are biased to operate in the subthreshold region will be described. At this time, since the signal φVRS applied to the gate of the transistor T3 is at a low level, the transistor T3 is turned off, which is equivalent to substantially not being present. The signal φD applied to the transistor T2
Is a high level (a potential equal to or close to the DC voltage VPD).

In the circuit shown in FIG.
When light enters D, a photocurrent is generated, and a voltage having a value obtained by natural logarithmically converting the photocurrent is generated at the gates of the transistors T1 and T2 due to the subthreshold characteristic of the transistor. Due to this voltage, a current flows through the transistor T2, and a charge equivalent to a value obtained by natural logarithmically converting the integrated value of the photocurrent is accumulated in the capacitor C. That is,
At the connection node a between the capacitor C and the source of the transistor T2, a voltage proportional to the natural logarithmically converted value of the photocurrent is generated. However, at this time, it is assumed that the transistor T4 is in an OFF state.

Next, a pulse signal φV is applied to the gate of the transistor T4 to turn on the transistor T4.
The charge stored in the capacitor C is led out to the output signal line 11 as an output current. The current led out to the output signal line 11 is a value obtained by natural logarithmically converting the integrated value of the photocurrent. In this manner, a signal (output current) proportional to the logarithmic value of the incident light amount can be read. After reading the signal, the transistor T4 is turned off and the signal φD is set to a low level (potential lower than the signal φVPS) to discharge the electric charge accumulated in the capacitor C to the line of the signal φD through the transistor T2. The potentials of C and the connection node a are initialized. By repeating such an operation at predetermined time intervals, a subject image that changes every moment can be continuously captured in a wide dynamic range. When the incident light amount is converted into a natural logarithm, the signal φVRS is always kept at the low level, and the transistor T3 is in the OFF state.

(2) A case where a photocurrent is linearly converted and output. Next, an operation when the signal φVPS is set to the high level will be described. At this time, the potential on the source side of the transistor T1 increases. Therefore, the transistor T1 is substantially turned off, and the transistor T1
Current does not flow between the source and drain of the transistor. Also, the signal φVRS given to the gate of the transistor T3 is kept at low level, and the transistor T3 is turned off.

Then, first, the transistor T4 is turned off.
At the same time, when the signal φD is set to a low level (a potential lower than the signal φVPS), the charge of the capacitor C is discharged to the line of the signal φD through the transistor T2, thereby resetting the capacitor C and setting the potential of the connection node a to, for example, DC. Initialize to a potential lower than the voltage VPD. This potential is held by the capacitor C. Thereafter, φD is returned to a high level (a potential equal to or close to the DC voltage VPD). In such a state, when light enters the photodiode PD, a photocurrent is generated. At this time, since a capacitor is formed between the back gate and the gate of the transistor T1, the junction capacitance of the photodiode PD, and the like, the charge due to the photocurrent is mainly stored in the gates of the transistors T1 and T2. Therefore, the gate voltage of the transistors T1 and T2 becomes a value proportional to the value obtained by integrating the photocurrent.

Now, since the potential of the connection node a is lower than the DC voltage VPD by the initialization, the transistor T2 is turned on, and a drain current corresponding to the gate voltage of the transistor T2 flows through the transistor T2. An amount of charge proportional to the gate voltage is stored in the capacitor C. Therefore, the potential of the connection node a becomes a value proportional to the value obtained by integrating the photocurrent. Next, when a pulse signal φV is applied to the gate of the transistor T4 to turn on the transistor T4, the electric charge accumulated in the capacitor C is led out to the output signal line 11 as an output current. This output current is a value obtained by linearly converting the integrated value of the photocurrent.

In this way, a signal (output current) proportional to the amount of incident light can be read. Thereafter, the transistor T4 is turned off and the signal φD is set to low level to discharge the signal φD to the line of the signal φD through the transistor T2, thereby initializing the potential of the capacitor C and the connection node a. Thereafter, the transistor T3
A high-level signal φVRS is applied to the gate of the transistor PD3 to turn on the transistor T3, thereby turning the photodiode PD
The drain voltage of the transistor T1 and the transistor T
1, the gate voltage of T2 is initialized. By repeating such an operation at predetermined time intervals, a subject image that changes every moment can be continuously captured with a good S / N ratio.

As described above, the pixels shown in FIG. 3 can switch the photoelectric conversion output characteristics of the same pixel by a simple potential operation. When switching from a state in which the signal is logarithmically converted and output to a state in which the signal is linearly converted and output, the output is first switched by adjusting the potential of φVPS, and then the transistor T3 is reset by the transistor T3. Is preferred. On the other hand, when switching from a state in which the signal is linearly converted and output to a state in which the signal is logarithmically converted and output, resetting of the transistor T1 by the transistor T3 is not particularly necessary. This is because the carriers accumulated in the transistor T1 due to the fact that the transistor T1 is not in the complete OFF state are erased by carriers of the opposite polarity.

Another example of the configuration of the area sensor 3 will be described with reference to FIG. In FIG.
Gamn and Gb11 to Gbmn indicate pixels arranged in a matrix (matrix arrangement) by being arranged in odd rows and even rows, respectively. Reference numeral 7 denotes a vertical scanning circuit, which includes odd rows 9-1, 9-2,..., 9-n, and even rows 10-1,
.., 10-n are sequentially scanned.

Reference numeral 8 denotes a horizontal scanning circuit, which includes pixels Ga11 to G11.
amn to output signal lines 11-1, 11-2,..., 11
-M are sequentially derived to the final signal line 14, and the photoelectric conversion signals derived from the pixels Gb11 to Gbmn to the output signal lines 12-1, 12-2,..., 12-m. The converted signals are sequentially derived to the final signal line 15.
13 is a power supply line. Also, the signal line 14 and the signal line 1
5 is provided with a connection switching unit 16 for switching the connection to a luminance signal line 17 connected to the switching determination circuit 4 (FIG. 1) and an image data line 18 connected to the processing unit 6 (FIG. 1).

For each pixel, the odd rows 9-1, 9-
2, ..., 9-n, even rows 10-1, 10-2, ...
.., 10-n, output signal lines 11-1, 11-2,.
, 11-m, output signal lines 12-1, 12-2,.
, 12-m and the power supply line 13 as well as other lines (for example, a clock line and a bias supply line) are connected, but these are omitted in FIG.

The output signal lines 11-1, 11-2,...
N-channel MOS transistor Qa every 11-m
, Qam, and N-channel MOS transistors Qc1, Qc2,..., Qcm, and N-channel MOS transistors for each output signal line 12-1, 12-2,. MOS transistors Qb1, Qb2,.
., Qbm and N-channel MOS transistor Qd
1, Qd2,..., Qdm are provided one by one as shown.

The transistors Qa1, Qa2,..., Q
am drains the output signal lines 11-1, 11
,..., 11-m, the source is connected to the final signal line 14, and the gate is connected to the horizontal scanning circuit 8. Also, transistors Qb1, Qb2,.
., Qbm are connected to the output signal line 12-, respectively.
, 12-m, the source is connected to the final signal line 15, and the gate is connected to the horizontal scanning circuit 8. On the other hand, transistors Qc1 and Qc
, Qcm are connected to the DC voltage line 19, and the drains are output signal lines 11-1, 11-, respectively.
,..., 11-m, and the source is a DC voltage V
It is connected to the line 20 of PS '. Further, the gates of the transistors Qd1, Qd2,..., Qdm are connected to the DC voltage line 19, and the drains are connected to the output signal line 12-.
, 12-m, and the source is connected to the line 20 of the DC voltage VPS '.

As will be described later, an N-channel fifth MOS transistor T5 for outputting a signal based on the photocharge generated in each pixel is provided in each pixel.
Transistor T5 and transistor Q1 (this transistor Q1 is the transistor Qc1 to Qcm, Qd1
~ Qdm. 5) is as shown in FIG. Here, the relationship between the DC voltage VPS 'connected to the source of the transistor Q1 and the DC voltage VPD' connected to the drain of the transistor T5 is VPD '>VPS', and the DC voltage VPS 'is, for example, a ground voltage ( Ground). In this circuit configuration, a signal is input to the gate of the upper transistor T5, and the DC voltage DC is constantly applied to the gate of the lower transistor Q1. Therefore, the lower transistor Q1 is equivalent to a resistor or a constant current source.
The circuit (a) is a source follower-type amplifier circuit. In this case, what is amplified and output from the transistor T5 may be a current.

Transistor Q2 (this transistor Q2
Are the transistors Qa1 to Qam and Qb1 to Qb in FIG.
m. ) Is controlled by the horizontal scanning circuit 8,
It operates as a switch element. As described later, FIG.
A switching N-channel fourth MOS transistor T4 is also provided in the pixel. This transistor T4
5A, the circuit of FIG.
(B). That is, the transistor T4 is inserted between the transistor Q1 and the transistor T5. Here, the transistor T4 is for selecting a row, and the transistor Q2 is for selecting a column.

With the configuration as shown in FIG. 5, a large signal gain can be output. Therefore, when the pixel converts the photocurrent generated from the photosensitive element in a natural logarithmic manner to expand the dynamic range, the output signal is small as it is, but is amplified to a sufficiently large signal by the present amplifier circuit. Therefore, processing in a subsequent signal processing circuit (not shown) becomes easy. Further, the transistor Q1 constituting the load resistance portion of the amplifier circuit is not provided in the pixel, and the output signal line 1 to which a plurality of pixels arranged in the column direction are connected is connected.
, 11-m, and the signal lines 12-1, 12-2,..., 12-m, the number of load resistors or the number of constant current sources is increased. And the area occupied by the amplifier circuit on the semiconductor chip can be reduced.

An example of each pixel of the area sensor 3 having the configuration shown in FIG. 4 will be described with reference to FIG. FIG.
Elements, signal lines, and the like used for the same purpose as the pixel shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The pixel shown in FIG. 6 is different from the pixel shown in FIG. 3 in that the fifth MOS transistor T5 has a gate connected to the connection node a and performs current amplification according to the voltage applied to the connection node a.
A fourth MOS transistor T4 for row selection in which the drain is connected to the source of the transistor T5, and a sixth MOS transistor T6 in which the drain is connected to the connection node a and initializes the potential of the capacitor C and the connection node a.
Are added. The source of the transistor T4 is an output signal line 11 (this output signal line 11
1, 11-2,..., 11-m, or 12-1, 12
,..., 12-m). Note that the transistors T4 to T6 are also the transistors T1
Similarly to T3, an N-channel MOS transistor has a back gate grounded.

The DC voltage VPD is applied to the drains of the transistors T2 and T5, and the signal φV is input to the gate of the transistor T4. The DC voltage V RB2 is applied to the source of the transistor T6, and the signal φVRS2 is input to the gate of the transistor T6. Note that, in the present embodiment, the transistors T1 to T3 and the capacitor C
The same operation as each element in the pixel shown in FIG.
Changing the bias value of the transistor T1 by switching the voltage value of VPS to convert the output signal led to the output signal line 11 into a natural logarithm with respect to the photocurrent;
And a case of linear conversion. The operation in each of these cases will be described below.

(1) A case where a photocurrent is converted into a natural logarithm and output. First, the operation when the signal φVPS is at the low level and the transistors T1 and T2 are biased to operate in the subthreshold region will be described. At this time, the gate of the transistor T3 is
Since the low-level signal φVRS is supplied in the same manner as in the pixel No. 1, the transistor T3 is turned off, which is equivalent to the fact that the transistor T3 does not substantially exist.

When light enters the photodiode PD, a photocurrent is generated, and a voltage having a value obtained by natural logarithmically converting the photocurrent is generated at the gates of the transistors T1 and T2 due to the subthreshold characteristic of the transistor. Due to this voltage, a current flows through the transistor T2 and the capacitor C
Accumulates a charge equivalent to a value obtained by natural logarithmically converting the integrated value of the photocurrent. That is, a voltage proportional to a value obtained by natural logarithmically converting the integrated value of the photocurrent is generated at the connection node a between the capacitor C and the source of the transistor T2. However, at this time, the transistors T4,
T6 is in the OFF state.

Next, when a pulse signal is applied to the gate of the transistor T4 to turn on the transistor T4, a current proportional to the voltage applied to the gate of the transistor T5 is led out to the output signal line 11 through the transistors T4 and T5. You. Now, the voltage applied to the gate of the transistor T5 is
Since the voltage is applied to the connection node a, the output signal line 11
Is a value obtained by natural logarithmically converting the integrated value of the photocurrent.

In this manner, a signal (output current) proportional to the logarithmic value of the amount of incident light can be read. After the signal is read, the transistor T4 is turned off, and the transistor T6 is turned on by applying a high-level signal φVRS2 to the gate of the transistor T6, whereby the potentials of the capacitor C and the connection node a can be initialized. When the output current is naturally logarithmically converted with respect to the amount of incident light, the signal φVRS always remains at the low level.

(2) A case where a photocurrent is linearly converted and output. Next, an operation when the signal φVPS is set to the high level will be described. At this time, a low-level signal φVRS is supplied to the gate of the transistor T3 to turn off the transistor T3. Then, first, the transistor T6
A high-level signal φVRS2 is applied to the gate of the transistor to turn on the transistor T6, thereby resetting the capacitor C and initializing the potential of the connection node a to a potential VRB2 lower than the DC voltage VPD. This potential is held by the capacitor C. Thereafter, the signal φVRS2 is set to low level, and the transistor T6 is turned off. In such a state, when light enters the photodiode PD, a photocurrent is generated. At this time, since a capacitor is formed between the back gate and the gate of the transistor T1 and the junction capacitance of the photodiode PD, a charge due to photocurrent is accumulated in the gate and the drain of the transistor T1. Therefore, the gate voltage of the transistors T1 and T2 becomes a value proportional to the value obtained by integrating the photocurrent.

Since the potential of the connection node a is lower than the DC voltage VPD, the transistor T2 is turned on, and a drain current corresponding to the gate voltage of the transistor T2 flows through the transistor T2. Electric charges are stored in the capacitor C. Therefore, the potential of the connection node a becomes a value proportional to the value obtained by integrating the photocurrent. Next, when a pulse signal is applied to the gate of the transistor T4 to turn on the transistor T4, a current proportional to the voltage applied to the gate of the transistor T5 is led out to the output signal line 11 through the transistors T4 and T5.
Since the voltage applied to the gate of the transistor T5 is the voltage of the connection node a, the current led out to the output signal line 11 is a value obtained by linearly converting the integrated value of the photocurrent.

In this way, a signal (output current) proportional to the amount of incident light can be read. After reading the signal, first, the transistor T4 is turned off,
By applying a high-level signal φVRS to the gate of the transistor T3, the transistor T3 is turned on, and the photodiode PD, the drain voltage of the transistor T1, and the gate voltages of the transistors T1 and T2 are initialized. Next, a high-level signal φVRS2 is applied to the gate of the transistor T6 to turn on the transistor T6 and initialize the potentials of the capacitor C and the connection node a.

The signal reading from each pixel may be performed using a charge-coupled device (CCD).
In this case, the charge can be read out to the CCD by providing a potential barrier having a variable potential level corresponding to the transistor T4 in FIG. 3 or FIG.

When an area sensor having the configuration shown in FIG. 2 provided with the pixels as shown in FIG. 3 or an area sensor having the configuration shown in FIG. 4 provided with the pixels as shown in FIG. The operation of the solid-state imaging device 1 will be described below with reference to FIGS. However, the processing unit 6 is not shown in FIG. The solid-state imaging device 1 shown in FIG.
The switching point at which the area sensor 3 performs the logarithmic conversion operation or the linear conversion operation is set to approximately 700 [cd / m ² ] by the brightness of the subject detected by the switching determination circuit 4. This 7
The reason for setting the value to 00 [cd / m ² ] will be described below.

First, when the area sensor 3 performs logarithmic conversion operation, it is possible to capture an image of a subject in a wide luminance range, although the high-luminance gradation is poor. Therefore, it is effective when the subject is bright, and particularly when the subject is exposed to direct sunlight, or when the direct sunlight is present in the background of the subject, the shadowed portion is sufficiently described, and the depth is large. It is possible to capture a high-quality image. The brightness of such a subject when it is bright is approximately 10
00 [cd / m ² ].

Next, when the area sensor 3 is operated for linear conversion, it is impossible to image a subject in a wide luminance range, but the gradation of the entire image is rich. Therefore, it is effective when the subject is dark, especially if the subject is in the shade,
Alternatively, when used for imaging a subject on cloudy weather, a high-quality image with rich gradation can be captured. The luminance of such a subject when it is dark is approximately 500 [cd /
m ² ]. Therefore, the area sensor 3 is operated in a logarithmic conversion operation when it is bright in direct sunlight, and the area sensor 3 is operated in a linear conversion operation when it is dark without direct sunlight.
m ² ].

(A) When imaging an object in a bright situation As shown in FIG. 7A, when imaging an object 50 which has received direct sunlight, first, each pixel arranged in an odd-numbered row of the area sensor 3 is used. Assuming that image data of one field is output, a luminance signal is transmitted to the switching determination circuit 4 from each pixel arranged in an even row of the area sensor 3. At this time, each pixel arranged in the even-numbered row of the area sensor 3 is performing a logarithmic conversion operation. Then, among the luminance signals output from the respective pixels, the amount of the luminance signal representing the luminance of 700 [cd / m ² ] or more becomes a predetermined value or more. It is determined that there is. The switching signal generating circuit 5 receiving this determination signal outputs
A switching signal for setting VPS (FIG. 3 or FIG. 6) to low level is generated.

Next, according to the switching signal, the source of the transistor T1 (FIG. 3 or FIG. 6) and the capacitor C (FIG. 3) of each pixel arranged in the even-numbered row of the area sensor 3 for outputting the image information of the next field. Or, the voltage applied to FIG. 6) becomes a low level, and as described above, the transistor T
1, T2 (FIG. 3 or FIG. 6) is biased to operate in the sub-threshold region. The pixels arranged on the even rows of the area sensor 3 biased to operate in the logarithmic conversion operation output image data of the next field and are arranged on the odd rows of the area sensor 3 at the same time. The luminance signal is changed by each of the pixels,
Sent to At this time, each pixel arranged in an odd row of the area sensor 3 performs a logarithmic conversion operation.

(B) When imaging an object in a dark situation As shown in FIG. 7B, when imaging an object 50 in which direct sunlight is blocked in cloudy weather or the like, first, the area sensor 3
Assuming that one field of image data is output from each pixel arranged in the odd-numbered row, a luminance signal is transmitted to the switching determination circuit 4 from each pixel arranged in the even-numbered row of the area sensor 3. At this time, each pixel arranged in the even-numbered row of the area sensor 3 is performing a logarithmic conversion operation. Then, among the luminance signals output from the respective pixels, the amount of the luminance signal representing the luminance of 700 [cd / m ² ] or more becomes less than a predetermined value, and the area sensor 3 should be operated by the switching determination circuit 4 to perform the linear conversion operation. It is determined that there is. The switching signal generating circuit 5 receiving this determination signal generates a switching signal for setting φVPS (FIG. 3 or FIG. 6) to a high level.

Next, in response to the switching signal, the voltage applied to the source of the transistor T1 (FIG. 3 or FIG. 6) of each pixel arranged in the even-numbered row of the area sensor 3 for outputting the image information of the next field becomes high level. As a result, as described above, the transistor T1 is substantially turned off. The pixels arranged in the even rows of the area sensor 3 biased so as to operate in the linear conversion operation output image data of the next field at the same time.
A luminance signal is sent to the switching determination circuit 4 by each pixel arranged in an odd row of the area sensor 3. At this time, each pixel arranged in an odd row of the area sensor 3 performs a logarithmic conversion operation.

As described above, when the image data of the field is output by the pixels arranged in the odd-numbered rows of the area sensor 3, the luminance signal outputted by the pixels arranged in the even-numbered rows performing the logarithmic conversion operation. And a switching signal generation circuit 5
A switching signal is sent to the area sensor 3 to determine the operating state of the pixels arranged in the even rows that output the image data of the next field. Further, when the image data of the field is output by the pixels arranged in the even-numbered rows of the area sensor 3, the switching judgment is performed using the luminance signal output by performing the logarithmic conversion operation of the pixels arranged in the odd-numbered rows. The determination is made by the circuit 4, and as a result of the determination, a switching signal is transmitted from the switching signal generating circuit 5 to the area sensor 3 to determine the operation state of the pixels arranged in the odd rows that output the image data of the next field. .

In the present embodiment, the solid-state imaging device is not limited to a solid-state imaging device using all the pixels other than the pixel outputting the image data of the field currently being picked up as the pixel outputting the luminance signal. Instead, a solid-state imaging device in which a part thereof is used as a pixel that outputs a luminance signal may be used. Further, the image data and the luminance signal are serially output using the signal line of the area sensor
A switching means may be provided between the switching determination circuit 4 and the processing unit 6 so that a luminance signal is sent to the switching determination circuit 4 and image data is sent to the processing unit 6.

<Second Embodiment> A second embodiment will be described with reference to the drawings. The solid-state imaging device used in the present embodiment is a solid-state imaging device having the same block configuration as the solid-state imaging device shown in FIG. 1, as in the first embodiment. Further, in the present embodiment, the switching determination circuit 4
As in the first embodiment, instead of detecting only the brightness of the subject from the brightness signal from the area sensor 3, the brightness range of the subject is detected. For other blocks, the same operation as in the first embodiment is performed.

First, a method of detecting the luminance range of a subject will be described. The switching determination circuit 4 compares the signal levels of the luminance signals sent from the area sensor 3 to detect the minimum and maximum luminance signal levels. Then, the luminance range of the field being imaged is detected from the difference between the signal levels of the maximum and minimum luminance signals.

Next, the operation of the solid-state imaging device 1 will be described below with reference to FIGS. FIG.
In the solid-state imaging device 1 shown in (1), the switching point of whether the area sensor 3 performs the logarithmic conversion operation or the linear conversion operation is set to a point where the luminance range of the subject becomes, for example, 2.5 digits.

By the way, when the area sensor 3 performs the logarithmic conversion operation, the high-luminance gradation becomes poor.
It is possible to image a subject in a wide luminance range. Therefore, it is effective when the subject is bright and its luminance range is as wide as about 3 to 4 digits. In particular, when the subject is used when direct sunlight is applied to the subject or when direct sunlight is present in the background of the subject, a shadowed portion is obtained. Is sufficiently performed, so that a high-quality image with a depth can be captured.

Next, when the area sensor 3 is operated for linear conversion, it is impossible to image a subject in a wide luminance range, but the gradation of the entire image is rich. Therefore, it is effective when the subject is dark and its luminance range is as narrow as about two digits,
In particular, when the subject is in the shade or when the subject is imaged in cloudy weather, a high-quality image with rich gradation can be taken.

(A) When imaging an object in a bright condition As shown in FIG. 7A, when imaging an object 50 that has received direct sunlight, first, each pixel arranged in an odd-numbered row of the area sensor 3 is used. Assuming that image data of one field is output, a luminance signal is transmitted to the switching determination circuit 4 from each pixel arranged in an even row of the area sensor 3. At this time, each pixel arranged in the even-numbered row of the area sensor 3 is performing a logarithmic conversion operation. The switching determination circuit 4 sequentially compares the signal levels of the luminance signals transmitted from the pixels arranged in the even-numbered rows from the area sensor 3 and detects the maximum value and the minimum value. Further, when the difference between the maximum value and the minimum value of the signal levels detected as described above is larger than the reference value (when the brightness range of the subject is 2.5 digits or more), it is determined that the brightness range of the subject is wide. Therefore, it is determined by the switching determination circuit 4 that the area sensor 3 should perform the logarithmic conversion operation. The switching signal generating circuit 5 receiving this determination signal outputs
A switching signal for setting PS (FIG. 3 or FIG. 6) to low level is generated.

Next, in response to the switching signal, the source of the transistor T1 (FIG. 3 or FIG. 6) and the capacitor C (FIG. 3) of each pixel arranged on the even-numbered row of the area sensor 3 for outputting the image information of the next field. Or, the voltage applied to FIG. 6) becomes a low level, and as described above, the transistor T
1, T2 (FIG. 3 or FIG. 6) is biased to operate in the sub-threshold region. The pixels arranged on the even rows of the area sensor 3 biased to operate in the logarithmic conversion operation output image data of the next field and are arranged on the odd rows of the area sensor 3 at the same time. The luminance signal is changed by each of the pixels,
Sent to At this time, each pixel arranged in an odd row of the area sensor 3 performs a logarithmic conversion operation.

(B) When imaging an object in a dark situation As shown in FIG. 7B, when imaging an object 50 that is blocked from direct sunlight in cloudy weather or the like, first, the area sensor 3
Assuming that one field of image data is output from each pixel arranged in the odd-numbered row, a luminance signal is transmitted to the switching determination circuit 4 from each pixel arranged in the even-numbered row of the area sensor 3. At this time, each pixel arranged in the even-numbered row of the area sensor 3 is performing a logarithmic conversion operation. The switching determination circuit 4 sequentially compares the signal levels of the luminance signals transmitted from the pixels arranged in the even-numbered rows from the area sensor 3 and detects the maximum value and the minimum value. Further, when the difference between the maximum value and the minimum value of the signal level detected in this way is smaller than the reference value (for example, when the brightness range of the subject is smaller than 2.5 digits), it is determined that the brightness range of the subject is narrow. I do. Therefore, it is determined by the switching determination circuit 4 that the area sensor 3 should perform the linear conversion operation. The switching signal generating circuit 5 receiving this determination signal generates a switching signal for setting φVPS (FIG. 3 or FIG. 6) to a high level.

Next, in response to the switching signal, the voltage applied to the source of the transistor T1 (FIG. 3 or FIG. 6) of each pixel arranged on the even-numbered row of the area sensor 3 for outputting the image information of the next field becomes high level. Thus, as described above, the transistor T1 (FIG. 3 or FIG. 6) is substantially turned off.
The state becomes the F state. The pixels arranged in the even rows of the area sensor 3 biased to operate in the linear conversion operation in this manner output image data of the next field, and at the same time, are arranged in the odd rows of the area sensor 3. A luminance signal is sent to the switching determination circuit 4 by each of the pixels thus set. At this time, each pixel arranged in an odd row of the area sensor 3 performs a logarithmic conversion operation.

As described above, when the image data of the field is output by the pixels arranged in the odd-numbered rows of the area sensor 3, the luminance signal output by the pixels arranged in the even-numbered rows performing the logarithmic conversion operation. The switching determination circuit 4 determines a luminance range from the data, and as a result of the determination, a switching signal is transmitted from the switching signal generating circuit 5 to the area sensor 3 to be arranged on an even-numbered row for outputting image data of the next field. The operating state of the pixel is determined. Also, area sensor 3
When the image data of the field is output by the pixels arranged in the even-numbered rows, the pixel arranged in the odd-numbered rows performs a logarithmic conversion operation to obtain a brightness range from the brightness signal output, thereby determining the switching range. As a result of the determination, a switching signal is transmitted from the switching signal generation circuit 5 to the area sensor 3 to determine the operating state of the pixels arranged in the odd rows for outputting the image data of the next field.

In this embodiment, the luminance range of the subject is obtained based on the luminance signal obtained by forcibly performing the logarithmic conversion operation of the area sensor. However, the area sensor performs the linear conversion operation. The switching range may be determined by detecting the number of luminance signals whose signal levels are saturated among the luminance signals obtained as a result, thereby obtaining the luminance range.
That is, when the area sensor is performing a linear conversion operation,
If the saturated data is larger than the predetermined value, it is considered that many white spots or black spots have occurred, and the conversion operation of the area sensor is switched to a logarithmic conversion operation.

The present embodiment is not limited to a solid-state imaging device using all the pixels other than the pixel outputting the image data of the field currently being picked up as the pixel outputting the luminance signal. Instead, a solid-state imaging device in which a part thereof is used as a pixel that outputs a luminance signal may be used. Further, the image data and the luminance signal are serially output using the signal line of the area sensor
A switching means may be provided between the switching determination circuit 4 and the processing unit 6 so that a luminance signal is sent to the switching determination circuit 4 and image data is sent to the processing unit 6.

In the first and second embodiments, the area sensor having the configuration shown in FIG. 2 has been described using the pixels having the circuit configuration shown in FIG. 3. For example, a pixel having a circuit configuration as shown in FIG. 8 or FIG. 9 may be used. Here, the configuration of the pixel in FIG. 8 is described below. Elements and signal lines used for the same purpose as the pixel shown in FIG. 3 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In the pixel shown in FIG. 8, unlike the pixel shown in FIG. 3, the source and the gate are connected without connecting the drain and the gate of the transistor T1. First,
The operation of the pixel when the photocurrent is logarithmically converted and output will be described. By increasing the voltage difference between the source and the drain of the transistor T1, the voltage generated between the gate and the source is made smaller than the threshold voltage. In this manner, the same state as when the transistor T1 is biased to operate in the sub-threshold region is obtained. Therefore, the photocurrent generated from the photodiode PD can be logarithmically converted and output.

Next, the operation of the pixel when the photocurrent is linearly converted and output will be described. At this time, the signal φVPS applied to the source of the transistor T1 is changed to the DC voltage VPD
By making the potential slightly lower, the transistor T
1 is substantially in a cutoff state. Therefore, no current flows between the source and the drain of the transistor T1. The subsequent operation is the same as that of the pixel shown in FIG.

Next, the configuration of the pixel shown in FIG. 9 will be described below. Elements and signal lines used for the same purpose as the pixel shown in FIG. 8 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In the pixel shown in FIG. 9, a DC voltage VRG is applied to the gate of the transistor T1. Other circuit configurations are the same as those in the pixel shown in FIG. When a pixel having such a configuration is used, its operation is essentially the same as that of the pixel shown in FIG. However, unlike the pixel in FIG. 8, the gate voltage of the transistor T1 can be set to an appropriate voltage.
It is not necessary to set .phi.VPS to a sufficiently low voltage as in the case of the pixel described above, and by setting the voltage to a certain low level, the same state as when the transistor T1 is biased in the subthreshold region can be obtained. When the linear conversion operation is performed, the operation is the same as that of the pixel in FIG.

In the first and second embodiments, the area sensor having the configuration shown in FIG. 4 has been described using the pixels having the circuit configuration shown in FIG. Alternatively, for example, a pixel having a circuit configuration as shown in FIG. 10 or FIG. 11 may be used. Here, the configuration of the pixel in FIG. 10 is described below. Note that elements and signal lines used for the same purpose as the pixel shown in FIG.
The same reference numerals are given and the detailed description is omitted.

In the pixel shown in FIG. 10, as in the pixel shown in FIG. 6, the source and the gate of the transistor T1 are connected without connecting the drain and the gate. First,
The operation of the pixel when the photocurrent is logarithmically converted and output will be described. By increasing the voltage difference between the source and the drain of the transistor T1, the voltage generated between the gate and the source is made smaller than the threshold voltage. In this manner, the same state as when the transistor T1 is biased to operate in the sub-threshold region is obtained. Therefore, the photocurrent generated from the photodiode PD can be logarithmically converted and output.

Next, the operation of the pixel when the photocurrent is linearly converted and output will be described. At this time, the signal φVPS applied to the source of the transistor T1 is changed to the DC voltage VPD
By making the potential slightly lower, the transistor T
1 is substantially in a cutoff state. Therefore, no current flows between the source and the drain of the transistor T1. The subsequent operation is the same as that of the pixel shown in FIG.

Next, the configuration of the pixel shown in FIG. 11 will be described below. Elements and signal lines used for the same purpose as the pixel shown in FIG. 10 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In the pixel shown in FIG. 11, the transistor T1
Is applied with the DC voltage VRG. The other circuit configuration is the same as the circuit configuration in the pixel shown in FIG. When a pixel having such a configuration is used, its operation is essentially the same as that of the pixel shown in FIG. However, unlike the pixel of FIG. 10, the gate voltage of the transistor T1 can be set to an appropriate voltage. Therefore, when performing the logarithmic conversion operation, it is not necessary to set φVPS to a sufficiently low voltage as in the pixel of FIG. By setting the voltage to a certain low level, the same state as when the transistor T1 is biased in the sub-threshold region can be obtained. When the linear conversion operation is performed, the operation is the same as that of the pixel in FIG.

Further, the pixels used in the present invention need only be capable of performing a logarithmic conversion operation and a linear conversion operation with one pixel. For example, FIG. 3, FIG. 6, FIG. 8, FIG.
0 or a pixel having a circuit configuration in which the capacitor of the pixel in FIG. 11 is omitted may be used. Further, as long as the pixel can be switched between the logarithmic conversion operation and the linear conversion operation, its circuit configuration is not mentioned in these circuit configurations.

Although the area sensor has been described using the area sensor having the structure as shown in FIG. 2 or FIG. 4, it is not limited to the area sensor having such a structure.
For example, an area sensor having another configuration in which the MOS transistor provided in the area sensor is a P-channel MOS transistor may be used.

[0094]

As described above, according to the present invention,
Whether the electric signal is logarithmically converted or linearly converted with respect to the incident light is switched based on the output of an area sensor which performs imaging. Therefore, it is possible to always perform good imaging regardless of the brightness state of the subject.For example, when imaging a subject in a bright situation, the area sensor performs logarithmic conversion operation so that a wide luminance range can be captured. When capturing an image of a subject in a dark condition, the area sensor can perform a linear conversion operation so that the image can be captured with good gradation. In addition, since the operation state of the area sensor is automatically switched using the electric signal from the area sensor, it is not necessary to newly provide a sensor for measuring the brightness of the subject, and the configuration is simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the internal structure of a solid-state imaging device according to the present invention.

FIG. 2 is an example of an internal structure of an area sensor used in the solid-state imaging device of the present invention.

FIG. 3 is an example of a circuit configuration of a pixel provided in the area sensor shown in FIG. 2;

FIG. 4 is an example of an internal structure of an area sensor used in the solid-state imaging device shown in FIG.

FIG. 5 is a partial circuit diagram of FIG. 4;

FIG. 6 is an example of a circuit configuration of a pixel provided in the area sensor shown in FIG.

FIG. 7 is a diagram showing a situation of a subject when taking an image using the solid-state imaging device shown in FIG. 1;

8 is an example of a circuit configuration of a pixel provided in the area sensor shown in FIG.

9 is an example of a circuit configuration of a pixel provided in the area sensor shown in FIG.

10 is an example of a circuit configuration of a pixel provided in the area sensor shown in FIG.

11 is an example of a circuit configuration of a pixel provided in the area sensor shown in FIG.

FIG. 12 is a diagram showing output characteristics of a LOG sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solid-state imaging device 2 Objective lens 3 Area sensor 4 Switching determination circuit 5 Switching signal generation circuit 6 Processing part 7 Vertical scanning circuit 8 Horizontal scanning circuit 9 Odd-numbered row 10 Even-numbered row 11, 12 Output signal line 13 Power supply line 14, 15 Signal line Reference Signs List 16 connection switching unit 17 luminance signal line 18 image data line 21 finder Ga11-Gamn pixel Gb11-Gbmn pixel T1-T6 N-channel MOS transistor PD Photodiode C Capacitor

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeshi Yano 2-13-13 Azuchicho, Chuo-ku, Osaka-shi Osaka International Building Minolta Co., Ltd. F term (reference) 4M118 AA02 AA10 AB01 BA10 BA14 CA02 DB01 DB03 DD09 FA06 5C022 AB31 AB68 AC42 AC69 5C024 AA01 CA15 CA21 FA01 GA01 GA31 HA11 HA16 JA04 JA11

Claims (12)

[Claims] 1. An area sensor for generating an electric signal corresponding to the amount of light incident on pixels arranged in a matrix, and an electric signal serving as image information of a first field is supplied to an odd-numbered pixel of the area sensor. The solid-state imaging device performs imaging by repeating an operation of outputting an electric signal serving as image information of a second field from pixels in an even-numbered row of the area sensor after the output from the solid-state imaging device. Can be switched between a first state in which the electric signal is linearly converted with respect to the amount of incident light and is output, and a second state in which the natural signal is converted and output in a natural logarithmic manner. Is output from the pixels arranged on the odd-numbered rows of the area sensor, based on the electric signals output from the pixels arranged on the even-numbered rows of the area sensor. Further, when the image information of the second field is output from the pixels arranged on the even rows of the area sensor, based on the electric signal output from the pixels arranged on the odd rows of the area sensor. A solid-state imaging device that switches an operation state of each pixel that outputs an electric signal serving as image information of a next field in the area sensor. 2. An area sensor for generating an electric signal corresponding to the amount of light incident on pixels arranged in a matrix, and an electric signal serving as image information of a first field is supplied to a pixel in an odd-numbered row of the area sensor. The solid-state imaging device performs imaging by repeating an operation of outputting an electric signal serving as image information of a second field from pixels in an even-numbered row of the area sensor after the output from the solid-state imaging device. Can be switched between a first state in which the electric signal is linearly converted with respect to the amount of incident light and is output, and a second state in which the natural signal is converted and output in a natural logarithmic manner. When the image information of the area sensor is output from the pixels arranged in the odd-numbered rows of the area sensor, the image information is obtained from the electric signals output from the pixels arranged in the even-numbered rows of the area sensor. And when the image information of the second field is output from the pixels arranged on the even rows of the area sensor, the electrical information output from the pixels arranged on the odd rows of the area sensor is obtained. A solid-state imaging device comprising: obtaining luminance information of a subject from a signal; and switching an operation state of each pixel that outputs an electric signal serving as image information of a next field in the area sensor in accordance with the luminance information. . 3. An operation state of each pixel which outputs an electric signal serving as image information of a next field in the area sensor is set to a first state when it is determined that the luminance of the subject is low based on the luminance information. And switching means for setting an operation state of each pixel for outputting an electric signal serving as image information of a next field in the area sensor to a second state when the luminance of the subject is determined to be bright based on the luminance information. The solid-state imaging device according to claim 2, wherein: 4. The apparatus according to claim 3, wherein said switching means generates a switching signal which is a binary voltage signal, and the operating state of each pixel in said area sensor is switched by said switching signal. The solid-state imaging device according to claim 1. 5. An area sensor for generating an electric signal according to the amount of light incident on pixels arranged in a matrix, and an electric signal serving as image information of a first field is supplied to an odd-numbered pixel of the area sensor. The solid-state imaging device performs imaging by repeating an operation of outputting an electric signal serving as image information of a second field from pixels in an even-numbered row of the area sensor after the output from the solid-state imaging device. Can be switched between a first state in which the electric signal is linearly converted with respect to the amount of incident light and is output, and a second state in which the natural signal is converted and output in a natural logarithmic manner. When the image information is output from the pixels arranged in the odd-numbered rows of the area sensor, the image information is obtained from the electric signals output from the pixels arranged in the even-numbered rows of the area sensor. When the luminance information of the subject is detected from the luminance information of the subject, and when the image information of the second field is output from the pixels arranged in the even rows of the area sensor, the luminance information of the second field is arranged in the odd rows of the area sensor. Brightness range detection means for detecting a brightness range of the subject from brightness information of the subject obtained from an electric signal output from the pixel, and image information of a next field in the area sensor according to the brightness range of the subject. A solid-state imaging device characterized by switching the operation state of each pixel that outputs an electric signal. 6. When the luminance range of the subject is determined to be narrow, the operation state of each pixel for outputting an electric signal serving as image information of the next field in the area sensor is set to the first state, and the luminance range of the subject is 6. The solid-state imaging device according to claim 5, wherein when it is determined that the image signal is wide, the operation state of each pixel that outputs an electric signal serving as image information of a next field in the area sensor is set to the second state. apparatus. 7. The brightness range detecting means detects the maximum value and the minimum value by sequentially comparing the magnitude of the level of the electric signal serving as the luminance information sent from the area sensor, and detects the maximum value and the minimum value of the electric signal. Switching determination for determining whether the operation state of a pixel that outputs an electric signal serving as image information of the next field in the area sensor is set to the first state or the second state according to the difference between the maximum value and the minimum value of Means for generating a switching signal for switching an operation state of a pixel which outputs an electric signal serving as image information of a next field in the area sensor according to a result determined by the switching determination means; The solid-state imaging device according to claim 5, further comprising: 8. The solid-state imaging device according to claim 7, wherein the switching signal is a binary voltage signal. 9. The solid-state imaging device according to claim 1, wherein a pixel in the area sensor that outputs the electric signal serving as the luminance information is operated in a second state. . 10. A pixel provided in the area sensor, comprising: a photosensitive element having a first electrode to which a DC voltage is applied; a first electrode, a second electrode, and a control electrode; Is connected to a second electrode of the photosensitive element, and a transistor into which an output current from the photosensitive element flows. By changing a potential difference between a first electrode and a second electrode of the transistor, each pixel is 10. The solid-state imaging device according to claim 1, wherein the operation is switched between a first state and a second state. 11. A pixel provided in the area sensor, comprising: a photosensitive element having a first electrode to which a DC voltage is applied; a first electrode, a second electrode, and a control electrode; A transistor connected to a second electrode of the element, to which an output current from the photosensitive element flows, and to which a second electrode and a control electrode are connected, between the first electrode and the second electrode of the transistor 10. The solid-state imaging device according to claim 1, wherein the operation of each pixel is switched between a first state and a second state by changing a potential difference between the first state and the second state. 12. Each pixel provided in the area sensor includes: a photosensitive element having a first electrode to which a DC voltage is applied; a first electrode, a second electrode, and a control electrode, wherein the DC voltage is applied to the control electrode. And a transistor having a first electrode connected to the second electrode of the photosensitive element and having an output current flowing from the photosensitive element flowing therethrough, wherein a potential difference between the first electrode and the second electrode of the transistor is provided. The solid-state imaging device according to any one of claims 1 to 9, wherein the operation of each pixel is switched between a first state and a second state by changing.