JP2000184290A - Solid-state image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration in the S/N attended with miniaturization of a solid-state image pickup elements and in a frequency characteristic due to light diffraction effect by an aperture area of an incident light limit section caused by the reduction in a distance between photoelectric conversion elements without losing a signal storage time and continuity of the storage time in a solid-state image pickup section. SOLUTION: The solid-state image pickup device is provided with a summing arithmetic section 4 that applies summing and averaging signals outputted n-times for one vertical scanning period from a solid-state image pickup element 2 at a read interval ratio and outputs the result and an input selection arithmetic section 16 that applies band limit to a prescribed signal band of an output from the summing arithmetic section 4 and gives the input of the result of an incident light control section 3. Then a drive control section 8 controls an element drive section 7 so that the storage time of charges read n-times for one vertical scanning period is almost uniformized thereby enhancing the S/N of the signal and widening the aperture area of the incident light limit section 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a solid-state imaging device having aperture control means.

[0002]

2. Description of the Related Art In recent years, solid-state image sensors have been widely used as image sensors in video cameras and electronic still cameras, and an automatic aperture function has been frequently used in order to constantly control the brightness of a screen.

Hereinafter, aperture control of a conventional solid-state imaging device will be briefly described. FIGS. 6 and 7 show a conventional solid-state imaging device. FIG. 6 is a block diagram showing a configuration of a conventional solid-state imaging device. In FIG. 6, reference numeral 41 denotes an incident light limiting unit that controls the amount of incident light on a subject that enters through a lens (not shown), and corresponds to a diaphragm generally used for an imaging unit such as a video camera. 42 is an incident light limiting unit 4
A solid-state imaging device that converts an optical signal from 1 into an electric signal,
Reference numeral 43 denotes an incident light control unit that operates to control the amount of incident light in the incident light limiting unit 41; 44, a signal processing unit that performs signal processing on a subject electric signal from the solid-state imaging device 41; and 45, an electric signal from the solid-state imaging device 41. Is an input operation unit that controls the incident light control unit 43 so that the level becomes a predetermined level, and 46 is an element driving unit that drives the fixed imaging element 42.

FIG. 7 is a timing chart showing the operation of each section of the solid-state imaging device having the configuration shown in FIG. FIG. 3A shows a vertical synchronization signal, FIG. 3B shows a readout signal from a solid-state imaging device synchronized with the vertical synchronization signal,
FIG. 1C shows the charge accumulation level in the solid-state image sensor, FIG. 2D shows the output signal from the solid-state image sensor, FIG. 2E shows the output signal of the signal processing unit, and FIG. This is the output signal from.

The operation of the conventional solid-state imaging unit having the above-described configuration will be described below.

The light signal incident through the lens is limited in the amount of light by an incident light restricting unit 41, forms an image on a photoelectric conversion element on a solid-state imaging device 42, and forms a control signal output from an element driving unit 46. Photoelectric conversion and charge accumulation are performed based on the results. When a uniform optical signal is incident on the solid-state imaging device 42, the vertical synchronization signal shown in FIG. 7A is output at the same timing by the readout signal shown in FIG. The charge thus accumulated is read out from the photoelectric conversion element of the solid-state imaging device 42 and output as an electric signal from the solid-state imaging device 42 as shown in FIG. A signal corresponding to level A is output from the solid-state imaging device 42 during one vertical scanning period Tv. In this way, the electric signal output from the solid-state imaging device 42 is processed by the signal processing unit 44 to convert it into a video signal, and the signal shown in FIG. 7E is output.

On the other hand, an electric signal output from the solid-state imaging device 42 is input to an input operation unit 45, and the input operation unit 45
Then, the incident light limiting unit 41 is driven via the incident light control unit 43 to control the amount of light so that the input electric signal becomes a predetermined level.

If the level set by the input operation unit 45 is A in FIG. 7 (f), the incident light control unit 43 controls the incident light control so that this value is always input to the input operation unit 45. Since the unit 41 is driven, stable incident light control is performed.

[0009]

However, in the above-mentioned conventional solid-state imaging device, as the size of the solid-state imaging device 42 is reduced, the S / N of the output signal is deteriorated due to the reduction in the size of the photoelectric conversion unit in the solid-state imaging device. Further, although frequency characteristics are degraded due to a light diffraction effect due to an opening area of the incident light restricting portion 41 due to a reduction in the distance between the photoelectric conversion elements, a correction means or the like is not particularly provided, and S / N and frequency characteristics are reduced. There has been a problem that a video signal is output from the signal output unit 44 while being deteriorated.

The present invention solves the above-mentioned conventional problems, and does not impair the continuity of the signal accumulation time and the accumulation time, and reduces the distance between S / N-degraded photoelectric conversion elements accompanying the downsizing of the solid-state imaging device. An object of the present invention is to provide a solid-state imaging unit capable of preventing frequency characteristic deterioration due to light diffraction effect due to an opening area of an incident light limiting unit due to reduction.

[0011]

In order to achieve this object, a solid-state imaging device according to the present invention comprises a solid-state imaging device for converting an optical signal into an electric signal and a plurality of times from the solid-state imaging device during one vertical scanning period. Element driving means for driving to output an electric signal, incident light limiting means for limiting incident light to the solid-state imaging device, and incident light control for controlling the incident light limiting means in accordance with an output of the solid-state imaging element Means, addition operation means for adding and averaging the electric signals output a plurality of times during one vertical scanning period from the solid-state imaging device, and input operation for controlling the incident light control section based on the operation result of the addition operation means Means.

With this configuration, the signal read out a plurality of times is added and averaged, so that the signal-to-noise ratio is good, and the added-averaged signal is used for controlling the incident light limiting section, thereby opening the incident light limiting section. It is possible to provide a solid-state imaging section having a large area and good frequency characteristics.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, a solid-state imaging device for converting an optical signal into an electric signal, and an electric signal is output from the solid-state imaging device a plurality of times during one vertical scanning period. Element driving means for driving as described above, incident light limiting means for limiting incident light to the solid-state imaging device, incident light controlling means for controlling the incident light limiting means in accordance with an output of the solid-state imaging element, and An addition operation unit for adding and averaging electric signals output a plurality of times during one vertical scanning period from the imaging element, and an input operation unit for controlling the incident light control unit based on a calculation result of the addition operation unit. With such a configuration, the S / N ratio of the signal can be improved, and the opening area of the incident light limiting portion can be increased.

According to a second aspect of the present invention, there is provided a solid-state imaging device for converting an optical signal into an electric signal, and element driving means for driving the solid-state imaging device to output an electric signal a plurality of times during one vertical scanning period. An incident light restricting unit that restricts incident light to the solid-state imaging device, an incident light control unit that controls the incident light restricting unit according to an output of the solid-state imaging device, and one vertical scanning period from the solid-state imaging device. An addition operation means for adding and averaging the electric signals output a plurality of times during the operation, and selecting and calculating only one of the electric signals output from the plurality of electric signals output from the solid-state imaging device, calculating the incident light control unit. It has an input selection calculating means for controlling. With such a configuration, the S / N of the signal is improved and the opening area of the incident light restricting portion can be widened.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) FIG. 1 is a block diagram showing a configuration of a solid-state imaging device according to Embodiment 2 of the present invention. Reference numeral 1 denotes an incident light amount of a subject incident through a lens (not shown). This is an incident light restricting unit that is an incident light restricting unit, and corresponds to a diaphragm generally used for an imaging unit such as a video camera. Reference numeral 2 denotes a solid-state imaging device that converts an optical signal from the incident light limiting unit 1 into an electric signal. Reference numeral 3 denotes an incident light control unit that is an incident light control unit that operates to control the amount of incident light in the incident light limiting unit 1. An addition operation unit, which is an addition operation means for performing an addition operation on the electric signal output a plurality of times during one vertical synchronization signal period from the solid-state imaging device 2, is a signal for converting the electric signal from the addition operation unit 4 into a video signal. A signal processing unit 6 that is a signal processing unit that performs processing and outputs it to the outside; an input calculation unit 6 that is an input calculation unit that controls the incident light control unit 1 so that the electric signal from the addition calculation unit 4 becomes a predetermined level; Reference numeral 7 denotes an element driving unit that is an element driving unit that drives the solid-state imaging device 2, and reference numeral 8 denotes a driving control unit that is a driving control unit that drives and controls the element driving unit 7.

FIG. 2 is a schematic diagram showing an example of the solid-state imaging device 2 used in the present embodiment. The solid-state imaging device 2 is called an interline CCD, and is widely used in solid-state imaging devices. In FIG. 2, reference numeral 21 denotes a photoelectric conversion element that converts an optical signal into an electric charge and accumulates the electric signal for a certain period of time, 22 denotes a read gate for reading the electric charge accumulated by the photoelectric conversion element 21, and 23 denotes a read through the read gate 22. A vertical transfer stage for sequentially transferring the transferred charges in the vertical direction; 24, a horizontal transfer stage for sequentially transferring the charges transferred by the vertical transfer stage 23 in the horizontal direction; 25, a solid transfer of the charges carried by the horizontal transfer stage 24. This is an output unit that outputs from the image sensor to the outside.

FIG. 3 is a timing chart for explaining the operation of this embodiment in the time axis direction. FIG.
Is a vertical synchronizing signal, and (b) is a solid-state imaging device 2 shown in FIG.
A read signal applied to the read gate 22 of FIG.
2 shows charge accumulation in the photoelectric conversion element 21 when uniform light enters the solid-state imaging device 2 shown in FIG. 2, (d) shows an output signal from the solid-state imaging device 2, and (e) shows an output of the addition operation unit 4. (F) is an output signal of the signal processing unit 5. The readout signal (b) generated twice by the drive control unit 8 in one Tv / 2 cycle during one vertical scanning period is converted into a predetermined voltage by the element drive unit 7 and applied to the solid-state imaging device 2.

The operation of the solid-state imaging device according to the present embodiment configured as described above will be described below.

The light signal incident through the lens is limited in the amount of light by the incident light restricting unit 1, forms an image on the photoelectric conversion element on the solid-state image pickup device 2, and forms a control signal output from the element driving unit 7. Photoelectric conversion and charge accumulation are performed based on the results. When a uniform optical signal is incident on the solid-state imaging device 2, the readout signal shown in FIG. 3B at the same timing as the vertical synchronization signal shown in FIG. 3) is read out from the photoelectric conversion element of the solid-state imaging device 2, and is output as an electric signal from the solid-state imaging device 2 as shown in FIG. A signal corresponding to the level A is output from the solid-state imaging device 2 during the 1/2 vertical scanning period Tv. The electric signal output from the solid-state imaging device 2 in this manner is input to the addition operation unit 4.

At this time, the photoelectric conversion element 2 of the solid-state imaging device 2
1 is the accumulation time T1 = Tv / 2 and the accumulation time T2 = Tv /
For every two, charge accumulation at level A is performed as shown in FIG. 3C, and charge is transferred to the vertical transfer stage 23 via the read gate 22. The charge corresponding to the level A is output from the output unit 25 via the horizontal transfer stage 24 twice in one vertical scanning period as shown in FIG.

The signal output twice during one vertical scanning period is input to the addition operation unit 4, the time axis of the output is adjusted twice, the addition is averaged, and the output is input to the signal processing unit 5. Here, since the main noise of the electric signal output from the solid-state imaging device is random noise, by performing the averaging of the signal output twice, the noise component is square-averaged and is reduced by about 3 dB. The accumulation timing of the two outputs during one vertical scanning period is continuous as shown by T1 and T2. By performing averaging, the signal having the same accumulation time as that of the conventional one output during one vertical scanning period is obtained. Can be obtained. The output signal of the addition operation unit 4 is
And controls the driving of the incident light limiting unit 1 via the incident light controlling unit 3 by performing band limitation on a predetermined signal band.

Here, the opening area of the incident light limiting section 1 is α,
The coefficient given by the input operation unit 6 and the incident light control unit 3 is β,
Assuming that the charge accumulation time in the photoelectric conversion element 21 is t and the signal level output from the photoelectric conversion element 21 is S, “α × t
= Β × S ”holds. That is, it is necessary to increase the opening area of the incident light restricting unit 1 in order to normally obtain the same signal in a short accumulation time.

In the prior art and this embodiment, one-time charge accumulation is Tv in the prior art, but is half as Tv / 2 in the present embodiment. In addition, the signal level output from the photoelectric conversion element is the same level A in the related art and the present embodiment. Therefore, a relationship of “q = p × 2” arises from the previous equation between the opening area p of the incident light limiting unit of the prior art and the opening area q of the incident light limiting unit 1 of the present embodiment. That is, in order to obtain a signal level equivalent to that of the related art, it can be achieved by doubling the opening area of the incident light limiting unit 1 of the present embodiment. Therefore, in order to normally obtain the same signal level within the period T1 or T2, the input operation unit 6 controls the incident light control unit 3 to double the opening area of the incident light limiting unit 1.

As described above, according to the present embodiment, the S / N degradation accompanying the downsizing of the solid-state image pickup device 2 and the incident light limiting section are not impaired without deteriorating the signal accumulation time and the continuity of the accumulation time. Degradation of the frequency characteristics due to the reduction of the aperture area can be prevented by doubling the aperture area of the incident light limiting unit 1.

(Embodiment 2) FIG. 4 is a block diagram showing a configuration of a solid-state imaging device according to Embodiment 2 of the present invention.
Denotes an incident light restricting unit that is an incident light restricting unit that controls an incident light amount of a subject incident through a lens (not shown).
This corresponds to a diaphragm generally used for an imaging unit such as a video camera. Reference numeral 2 denotes a solid-state imaging device that converts an optical signal from the incident light limiting unit 1 into an electric signal.
The incident light control unit 4 is an incident light control unit that operates so as to control the amount of incident light. The arithmetic unit 5 is a signal processing unit that is a signal processing unit that performs signal processing such as converting an electric signal from the addition arithmetic unit 4 into a video signal and outputs the processed signal to the outside.
Is an input selection operation unit that is an input selection operation unit that controls the incident light control unit 3 so that an electric signal from the solid-state imaging device 2 is at a predetermined level. The incident light control unit 3 is controlled by selecting only one of the electrical signals and performing an arithmetic process. Reference numeral 7 denotes an element driving unit which is an element driving unit for driving the fixed imaging element 2;
Reference numeral denotes a drive control unit which is drive control means for controlling the drive of the element drive unit 7.

FIG. 5 is a timing chart for explaining the operation of the present embodiment in the time axis direction. FIG.
Is a vertical synchronizing signal, and (b) is a solid-state imaging device 2 shown in FIG.
A read signal applied to the read gate 22 of FIG.
2 shows charge accumulation in the photoelectric conversion element 21 when uniform light enters the solid-state imaging device 2 shown in FIG. 2, (d) shows an output signal from the solid-state imaging device 2, and (e) shows an output of the addition operation unit 4. (F) is an output signal of the signal processing unit 5. The readout signal (b) generated twice by the drive control unit 8 in one Tv / 2 cycle during one vertical scanning period is converted into a predetermined voltage by the element drive unit 7 and applied to the solid-state imaging device 2. (G) is an output signal of the input selection operation unit 16.

The operation of the solid-state imaging device according to the present embodiment configured as described above will be described below.

The light signal incident through the lens is limited in the amount of light by the incident light restricting unit 1, forms an image on a photoelectric conversion element on the solid-state image pickup device 2, and forms a control signal output from the element driving unit 7. Photoelectric conversion and charge accumulation are performed based on the results. When a uniform optical signal is incident on the solid-state imaging device 2, the readout signal shown in FIG. 5B at the same timing as the vertical synchronizing signal shown in FIG. 5) is read out from the photoelectric conversion element of the solid-state imaging device 2 and output as an electric signal from the solid-state imaging device 2 as shown in FIG. A signal corresponding to the level A is output from the solid-state imaging device 2 during the 1/2 vertical scanning period Tv. The electric signal output from the solid-state imaging device 2 in this manner is input to the addition operation unit 4.

At this time, the photoelectric conversion element 2 of the solid-state imaging device 2
1 is the accumulation time T1 = Tv / 2 and the accumulation time T2 = Tv /
For every two, charge accumulation at level A is performed as shown in FIG. 5C, and charge is transferred to the vertical transfer stage 23 via the read gate 22. The charge corresponding to the level A is output from the output unit 25 via the horizontal transfer stage 24 twice during one vertical scanning period as shown in FIG.

The signal output twice during one vertical scanning period is input to the addition operation circuit 4, the time axis of the output is adjusted twice, the addition is averaged, and the output is input to the signal processing unit 5. Here, since the main noise of the electric signal output from the solid-state imaging device 2 is random noise, by performing the averaging of the signal output twice, the noise component is squared and reduced by about 3 dB. The accumulation timing of the two outputs during one vertical scanning period is continuous as shown by T1 and T2. By performing averaging, the signal having the same accumulation time as that of the conventional one output during one vertical scanning period is obtained. Can be obtained.

Also, during this one vertical scanning period, FIG.
The electric signal output twice from the solid-state imaging device 2 as described above is input to the input selection operation unit 16. As shown in FIG. 5 (g), the input selection calculation unit 16 selects only one of the two outputs (the electrical signal in the T1 period in the present embodiment) and performs a calculation process, and the input light control unit 3 The drive of the incident light limiting unit 1 is controlled via the control unit.

Here, the opening area of the incident light restricting portion 1 is α,
Assuming that the coefficient given by the input selection calculator 16 and the incident light controller 3 is β, the charge accumulation time in the photoelectric conversion element 21 is t, and the signal level output from the photoelectric conversion element 21 is S,
“Α × t = β × S” holds. That is, it is necessary to increase the opening area of the incident light restricting unit 1 in order to normally obtain the same signal in a short accumulation time.

In the prior art and the present embodiment, one-time charge accumulation is Tv in the prior art, but is half as Tv / 2 in the present embodiment. In addition, the signal level output from the photoelectric conversion element is the same level A in the related art and the present embodiment. Therefore, a relationship of “q = p × 2” arises from the previous equation between the opening area p of the incident light limiting unit of the prior art and the opening area q of the incident light limiting unit 1 of the present embodiment. That is, in order to obtain a signal level equivalent to that of the related art, it can be achieved by doubling the opening area of the incident light limiting unit 1 of the present embodiment. Therefore, in order to normally obtain the same signal level in the T1 or T2 period, the input selection calculation unit 16 controls the incident light control unit 3 to double the opening area of the incident light limiting unit 1.

As described above, according to the present embodiment, the S / N degradation and the incident light limiting unit 1 accompanying the downsizing of the solid-state imaging device 2 are maintained without impairing the signal accumulation time and the continuity of the accumulation time. Can be prevented by doubling the opening area of the incident light restricting portion 1.

In the above description, the number of charge readings in one vertical scanning period is two. However, the number of charges may be two or more, and the solid-state imaging device used is an interline type CCD. A sensor, a frame interline type CCD or the like may be used, and the charge reading intervals within one vertical scanning period are set at equal intervals, but may be set at irregular intervals.

[0036]

As described above, according to the present invention, the S / N deterioration due to the miniaturization of the solid-state image pickup device and the incident light due to the reduction of the distance between the photoelectric conversion devices without reducing the continuity of the signal accumulation time and the accumulation time. An excellent effect of preventing frequency characteristic deterioration due to the light diffraction effect due to the opening area of the restricting portion can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a solid-state imaging device according to Embodiment 1 of the present invention.

FIG. 2 is a schematic diagram illustrating a configuration of a solid-state imaging device according to the embodiment;

FIG. 3 is a timing chart showing an operation of the solid-state imaging device according to the embodiment;

FIG. 4 is a block diagram illustrating a configuration of a solid-state imaging device according to Embodiment 2 of the present invention;

FIG. 5 is a timing chart showing the operation of the solid-state imaging device according to the embodiment;

FIG. 6 is a block diagram illustrating a configuration of a conventional solid-state imaging device.

FIG. 7 is a timing chart showing the operation of a conventional solid-state imaging unit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 incident light limiting unit 2 solid-state imaging device 3 incident light control unit 4 addition operation unit 5 signal processing unit 6 input operation unit 7 element drive unit 8 drive control unit 16 input selection operation unit

Claims (2)

[Claims] A solid-state imaging device that converts an optical signal into an electric signal; an element driving unit that drives the solid-state imaging device to output an electric signal a plurality of times during one vertical scanning period; Incident light limiting means for limiting incident light;
Incident light control means for controlling the incident light limiting means according to the output of the solid-state imaging device, and addition arithmetic means for adding and averaging electric signals output a plurality of times during one vertical scanning period from the solid-state imaging device, A solid-state imaging device, comprising: input calculation means for controlling the incident light control section based on a calculation result of the addition calculation means. 2. A solid-state imaging device for converting an optical signal into an electric signal; an element driving unit for driving the solid-state imaging device to output an electric signal a plurality of times during one vertical scanning period; Incident light limiting means for limiting incident light;
Incident light control means for controlling the incident light limiting means according to the output of the solid-state imaging device, and addition arithmetic means for adding and averaging electric signals output a plurality of times during one vertical scanning period from the solid-state imaging device, A solid-state imaging device, comprising: input selection operation means for selecting and calculating only one of the plurality of electric signals output from the solid-state imaging element and controlling the incident light control unit. .