JP3166776B2 - Imaging device and imaging method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an imaging apparatus and an imaging method, and more particularly to an imaging apparatus and an imaging method having a substantially wide dynamic range.

2. Description of the Related Art An imaging apparatus is widely used as a video camera unit such as a camera-integrated VTR and a still video camera. A video camera using an image pickup tube or a solid-state image pickup device has a narrower dynamic range than a conventional silver halide photographic system, and therefore is overexposed or underexposed (a common name for a portion having a remarkably high or low luminance level) in a backlight or the like. And so on. In such a case, in the conventional video camera, the aperture is opened by about two apertures manually or by operating the reverse correction button to adjust the light amount.

However, even when such backlight correction is appropriately performed, overexposure occurs in the background even if the main subject has an appropriate exposure amount, and the screen has only a white background. That is, the narrowing of the dynamic range of the imaging apparatus is not solved only by adjusting the light amount so that the exposure amount of the main subject becomes appropriate as in the conventional apparatus.

In order to solve such a problem, for example, there is a method of expanding the dynamic range by performing two exposures.
In this method, a saturated pixel signal of a screen captured at a normal exposure time of 1/60 second is replaced with a pixel signal captured by a high-speed shutter operation (for example, 1/1000 second). In this method, the exposure time is about 16 times different, so that the dynamic range can be expanded 16 times.

[Problems to be Solved by the Invention] However, the method of expanding the dynamic range by the two exposures as described above has the following problems.

For example, in a movie camera that shoots a moving image, a normal exposure signal and a high-speed shutter signal are read for each field. Therefore, when two image signals are combined, the combined signal is only one image signal in two fields. No. Therefore, during the two-field period, the same synthesized signal is output from the memory or the like, and there is a problem that the dynamic resolution is reduced.

In addition, since each of the two exposures is performed by scanning the image sensor in a predetermined sequence, the next scanning cannot be performed unless all the signals have been output. In many cases, the region where the image sensor is saturated is only a part of the photographing screen, and the replacement of the signal for improving the dynamic range from the above two image signals requires little data. That is, an image is composed of a lot of unnecessary information, and it is uneconomical to output all two imaging signals and perform image processing as in the related art.

In view of such problems, an object of the present invention is to provide an imaging apparatus and an imaging method that can obtain a normal moving image with a wide dynamic range, simple image processing, and substantially.

[Means for Solving the Problems] An imaging apparatus according to a first aspect of the present invention includes a photoelectric conversion unit that converts incident optical information into an electrical signal, and a signal from the photoelectric conversion unit via a control electrode region of a transistor. A read transistor that amplifies and reads, and a signal connected between the photoelectric conversion unit and the control electrode region of the read transistor for transferring a signal of the photoelectric conversion unit to the control electrode region of the read transistor. A unit circuit section including first and second transfer transistors, and a reset transistor for supplying a reset potential, connected between the first transfer transistor and the second transfer transistor. The plurality of readings in the unit circuit units provided in each of the unit circuit units arranged in the vertical direction and arranged in one column in the vertical direction. A vertical output line to which a signal from and the transistor is read, connected in common to the control electrode region of the first transfer transistors each in a plurality of unit circuits of the horizontal direction,
A plurality of first signal lines, each of which is commonly connected to a control electrode region of the second transfer transistor in a plurality of unit circuit units in a horizontal direction,
A plurality of second signal lines; a plurality of third signal lines commonly connected to a control electrode region of the reset transistor in a plurality of unit circuits in a vertical direction; and a plurality of first signal lines First transfer selecting means for supplying a drive pulse to any of the first signal lines, and second transfer for supplying a drive pulse to any of the plurality of second signal lines. Selecting means, and reset selecting means for supplying a drive pulse to an arbitrary third signal line among the plurality of third signal lines.

An imaging apparatus according to a second aspect of the present invention includes: a plurality of arranged pixels; an exposure time setting unit configured to set a first exposure time or a second exposure time shorter than the first exposure time for the pixels; Determining means for determining whether the signal from the pixel is the first exposure time or the second exposure time; and determining whether the signal of the pixel is the first exposure time based on the determination result of the determining means. The exposure time is compared with a predetermined value that differs depending on whether the exposure time is the second exposure time or not, and the exposure time setting means is controlled based on the comparison result, and the first exposure time or the second exposure time is controlled. And control means for setting the time.

The imaging method according to the third aspect of the present invention outputs a signal of a first exposure time or a second exposure time shorter than the first exposure time from a plurality of arranged pixels, and the signal outputs the first exposure time. If the signal is the first exposure time or the second exposure time, the exposure time of the plurality of arranged pixels is set to the first exposure time or the second exposure time based on the comparison result. Is a signal of the second exposure time, the signal is compared with a second predetermined value, and based on the comparison result, the exposure time of the plurality of arranged pixels is determined by the first exposure time or the second exposure time. It is characterized in that it is set to time.

[Operation] In the imaging device of the present invention, the unit circuit unit includes a photoelectric conversion unit, a read transistor that reads a signal, first and second transfer transistors that transfer a signal from the photoelectric conversion unit to the read transistor, and a reset potential. And a plurality of first signal lines for controlling the first transfer transistor of the horizontal unit circuit section, and a plurality of first signal lines for controlling the second transfer transistor of the horizontal unit circuit section. Two signal lines, a plurality of third signal lines for controlling reset transistors of the unit circuit section in the vertical direction,
First transfer selection means for supplying a drive pulse to each first signal line, second transfer selection means for supplying a drive pulse to each second signal line, and supply of a drive pulse to each third signal line By having the reset selecting means, a desired area is reset and the exposure time is controlled, and areas having different exposure amounts can be obtained in one image. , The imaging device does not saturate.

Examples Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram showing a unit circuit of one embodiment of an imaging device according to the present invention.

FIG. 2 is a basic drive timing chart of the unit circuit of FIG.

In FIG. 1, reference numeral 100 denotes a unit circuit section, which constitutes one photoelectric conversion element. 10 is a photodiode serving as a photoelectric conversion unit, 20 is a transfer MOS transistor, and 30 is a reset MOS.
It is a transistor. The reset of the photodiode 10 (FIG. 2A) is performed by the transfer MOS transistor 20.
And the reset MOS transistor 30 is controlled by the drive pulses φ _R1 and φ _C.

40 is a transfer MOS transistor, 50 is a capacitor, and 60 is a read transistor. Volume 50 by the drive pulse phi _R2, and has a control circuit to the base potential of the read transistor 60.

The transfer of the accumulated charges photoelectrically converted by the photodiode 10 (FIG. 2 (B)) is performed by controlling the conduction of the transfer MOS transistor 20 and the transfer MOS transistor 40 by drive pulses φ _R1 and φ _R2 . The transferred charges are temporarily stored in a parasitic base capacitance (not shown) and a capacitance 50 of the read transistor 60 serving as a signal holding unit. When this is read from the stored signal read transistor 60 to the output signal line 65 (FIG. 2 shown (C)), the positive drive pulse phi _R2 is applied to the capacitor 50, the read transistor 60 forward biased. At this time, if the transfer MOS transistor 70 connected to the output signal line 65 into a conductive state by the driving pulse phi _T, the emitter current flows from the read transistor 60 to the temporary storage capacitor 80, it appears emitter voltage corresponding to the base potential.

Note that the waveforms of φR1 and φC in FIG. 2 (C) indicate that they may be at a high level or a low level.

To clear the charge remaining at the base of the read transistor 60 (FIG. 2D), first, reset MOS
The transistor 30 and the transfer MOS transistor 40 are turned on by the drive pulses φ _C and φ _R2 to be reset (period
T _D1 ). Next, the output line reset MOS transistor 90 is _{turned on} by the drive pulse φVC to make the emitter a constant potential,
By applying a positive drive pulse φ _R2 to the capacitor 50, the read transistor 60 is set to a forward bias state to discharge the charge remaining in the base (transient refresh operation).
The reset operation ends (period T _D2 ).

As described above, drive pulses φ _R1 , φ _R2 , φ _C , φ _T , φ _VC
, It is possible to perform from the reset operation of the photodiode, which is the basic operation of the image sensor, to the accumulation operation, and from the transfer of the accumulated charge to the read operation.

FIG. 3 is a schematic diagram of an XY type imaging device in which the above-described unit circuits are arranged.

Here, for simplicity, only 2 × 2 elements are shown.

As shown in FIG. 3, the XY type imaging device has two row decoders (L, R) 110, 120 and two column decoders (U, D) 130, 1
40, readout circuit 150, output amplifier 160, photoelectric conversion element
It has 100.

Each decoder 110, 120, 130, 140 receives a plurality of input pulses (φ
_Ln, φ _Rn, φ _Cn, by phi _On) for outputting a desired selected driving pulse.

An arbitrary photodiode 10 can be reset by a combination of drive pulses of the row decoder 110 and the column decoder 130.

In addition, the charge accumulated in the photodiode 10 is transferred to the read transistor 60 by a combination of the driving pulses of the row decoder 110 and the row decoder 120.

Further, by the drive pulse of the row decoder 120, the accumulated charge from the read transistor 60 in an arbitrary row is output to the output signal line 65.
After that, the data is amplified and transferred to the temporary storage capacity 80 (C _T ).

The base of any read transistor 60 is reset by a combination of the drive pulses of the column decoder 130 and the row decoder 120, and the drive pulse and the drive pulse φ from the row decoder 120 are reset.
The transient refresh operation of the read transistor 60 in an arbitrary row is performed by _VC, and the signal temporarily stored in the read circuit 150 is transferred to the horizontal output line by the column decoder 140 and output to the outside via the output amplifier 160. Is done.

In this embodiment, the photoelectric conversion unit is the photodiode 10, the read transistor is the read transistor 60, the first transfer transistor is the transfer MOS transistor 20, and the second transfer transistor is the transfer MOS transistor 4
0, reset transistor is reset MOS transistor 3
0, a vertical output line is an output signal line 65, a plurality of first signal lines are signal lines R1 _n1 and R1 _n2 , and a plurality of second signal lines are signal lines R2 _m1 and R2.
_m2 , a plurality of third signal lines are signal lines C _n1 and C _n2 , a first transfer selection means is a row decoder L110, a second transfer selection means is a row decoder R120, and a reset selection means is a column decoder U130. .

FIG. 4 is a block diagram showing an example of an image pickup apparatus using the image pickup device.

3, reference numeral 310 denotes an image pickup optical system; 320, an aperture for controlling the amount of light incident on the image pickup device; and 200, an XY type image pickup device shown in FIG. The amount of light incident from the imaging optical system 310 is limited by the stop 320 and forms an image on the image sensor 200. The aperture 320 and the imaging optical system 310 (lens in the figure) are connected to the image processing unit 36.
Driven by a drive circuit 390 controlled by a control signal from 0.

The signal processing circuit 330 is a known circuit that performs gamma correction and other video signal processing. This signal is converted into a digital signal by the A / D converter 340 and recorded in the image memory 350.

The signal from the image memory 350 is transferred to the image processing unit 360.

The image processing unit 360 includes an address unit, an operation processing unit, an operation memory unit, a control unit, and the like, and determines a signal level described below, converts a signal level, and generates a scan address for random control of the image sensor 200. Transfer and imaging optical system 31
A control signal for 0 (lens (focal length)) and the aperture 320 is generated. The image processing unit 360 transfers the scan pattern to the random scan address circuit 370 based on the selection of the sensor scan method and the determination result of the sensor signal level. The random scan address circuit 370 scans the image sensor 200 at random via an address signal via the scan interface 380. By this random scan, the row decoders (L, R) 110, 120 and the column decoders (U,
D) The input data is sent to 130 and 140, and the photodiode 10
Transfer of the stored charge (FIG. 2B), reading of the stored charge (FIG. 2C), reset of the photodiode 10 (FIG. 2A), reset of the read transistor 60 (FIG. 2A). (D) of FIG. 2 and the like are performed.

FIG. 5 (a) is a control flowchart of the image sensor 200, and FIG. 5 (b) is a flowchart relating to processing of a pixel signal output from the image sensor 200.

In FIG. 5 (a), when the operation of the imaging device is started (500), first, a scan selection of the image sensor 200 is performed (502). Pixel accumulation at the TV rate accumulation time (T _S1 = 1
/ 60 seconds), and for pixels that are saturated during the accumulation time of T _S1 , accumulation of pixels with a shorter accumulation time (T _S2 = 1/100)
0 seconds), the accumulation time of each pixel is different within one screen. (2) First, all the signals accumulated at T _S1 are read, and only the pixels saturated at the first time are T _S2. (3) Accumulation time (T _S2 ) for pixels in a certain area only
There is a way to change. A detailed description of the scanning method will be described later.

When the scan is selected (502), the scan pattern is sent from the image processing unit 360 to the random scan address circuit 370.
(504). Random scan address circuit 3
The address is transferred from 70 to the scan interface 380 (506), and the operation of each pixel of the image sensor 200 is controlled via the scan interface 380.

First, the charge accumulated in the photodiode 10 of the selected pixel (X, Y) is transferred to the image sensor 200 to the readout transistor (FIG. 2B) (508).

Next, the signal of the pixel is read out from the image sensor 200 (FIG. 2C), that is, the signal is output (51).
0). When the read operation (FIG. 2C) 510 is completed, the reset operation of the photodiode 10 (FIG. 2A) and the reset operation of the read transistor 60 (FIG. 2D). Made (512). Each operation of the image sensor 200 is a random scan address operation (504)
Is performed for each pixel or for each horizontal pixel column.

Except for the read operation ((C) in FIG. 2) 510, transfer of accumulated charges in a plurality of horizontal pixel columns, reset of the photodiode 10, and reset of the read transistor 60 are possible.

Further, after the signal is read ((C) in FIG. 2), (51)
0), the read signal is the signal processing circuit 330, the A / D converter 3
Data is fetched into the image memory 350 via 40 (514), and the image processing unit 360 performs arithmetic processing and the like (51).
6).

When the reset operation ends, the same operation is repeated again.

 Next, the flowchart of FIG. 5B will be described.

The flowchart shown in FIG.
6 is explained.

The image signal from the image memory 350 first has an accumulation time T _S2
It is determined whether or not the signal is (600). Where T _S2
Signal is transferred to the level converter and (60
2) The signal level is determined (604). If the pixel signal is equal to or higher than the low level V _L , the pixel address (X, Y) is subsequently stored in order to set the pixel accumulation time to T _S2 . If less than the low level _VL , the pixel accumulation time is T _S1
(614).

In the level conversion unit, the operation of T _S2 / T _S1 times is performed (60
2) However, since the dynamic range of the output device is generally narrow, coefficient processing of knee (KNEE) processing is further performed.

If it is determined in the decision 600 that the pixel signal is not the _TS2 pixel signal, the signal is transferred as output data and (61)
0), the signal level is determined, that is, the saturation is detected ( _VH or more) (606). If the signal is saturated, the pixel stores the pixel address (X, Y) to set the accumulation time to T _S2 (608). If the signal is not saturated, the pixel accumulation time is set to T _S1 (616).

This address is reflected from the image processing unit 360 to the random scan address circuit 370, and the photodiode 10 is reset ((A) in FIG. 2).

After the transfer of the output data (610), the data is input to the D / A converter 400 to be analog-converted (612).

Hereinafter, exposure time control by random scanning will be described.

6 (a) to 6 (c) are explanatory diagrams of exposure time control by random scanning, FIG. 6 (a) is a schematic diagram of an image pickup screen, FIG. 6 (b) is an explanatory diagram of vertical scanning, FIG. 6C is an explanatory diagram of horizontal scanning.

The points A and B shown in FIG. 6 (a) indicate the start time and the end time of the vertical scanning. In the screen, the area indicated by abcd has a much stronger incident light quantity than the surrounding area. At a normal television (TV) rate (exposure time 1/60 seconds), the pixels therein are assumed to be saturated.

Here, the exposure time of the pixels in the area abcd is, for example, 1/60
FIG. 6 (b) is an explanatory diagram for shortening to 0 seconds.

In the field period f _v (1), the pixels in each row sequentially transfer accumulated charges ((B) in FIG. 2), read out accumulated charges ((C) in FIG. 2), and reset the photodiode 10 ((C) in FIG. 2). 2 (A) and the resetting of the read transistor 60 (FIG. 2 (D)). Line scan is area ab
When approaching cd, the photodiode is preceded by readout so that the exposure time of the pixels in the area abcd becomes 1/600 second.
Reset 10

In FIG. 6B, a and b indicate a signal reading period and a reset period of a portion from the point a to the point b of the area abcd.

FIG. 6 (c) is an explanatory diagram of driving of the image sensor within one horizontal scanning period.

During the horizontal blanking period HBLK, the transfer from the transfer of accumulated charges ((B) in FIG. 2) to the resetting of the readout transistor 60 ((D) in FIG. 2) is performed, and a signal is output from the image sensor 200 during the effective scanning period. Is done.

In FIG. 6 (c), (B) to (B) in HBLK
(D) shows the operations from the transfer (B) of the accumulated charge to the reset (D) performed during the horizontal scanning period.

In FIGS. 6 (a) to 6 (c), scanning is performed so as to shorten the exposure time of a pixel which is saturated with the normal exposure time. However, a scanning method for expanding the dynamic range is described in this embodiment. However, the present invention is not limited to this. For example, as described above, as another embodiment of expanding the dynamic range, first, an imaging signal by 1/60 second exposure is read, a saturated pixel is detected from the imaging signal, and based on the detection signal, There is also a method of shortening the exposure time of the pixel and performing exposure, and then reading out only the signal of the pixel.

[Effects of the Invention] As described above, according to the present invention, since the exposure time of an arbitrary pixel can be changed, the dynamic range can be substantially widened by a simple and economical processing circuit. . Further, since a signal can be read from an arbitrary pixel, it can be applied to many image input devices.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram showing a unit circuit of an embodiment of an image sensor according to the present invention. FIG. 2 is a basic drive timing chart of the unit circuit of FIG. FIG. 3 is a schematic diagram of an XY type imaging device in which the above-described unit circuits are arranged. FIG. 4 is a block diagram showing an example of an image pickup apparatus using the image pickup device. FIG. 5 (a) is a control flowchart of the image sensor 200, and FIG. 5 (b) is a flowchart relating to processing of a pixel signal output from the image sensor 200. 6 (a) to 6 (c) are diagrams for explaining exposure time control by random scanning. 10: photodiode, 20: transfer MOS transistor, 30: reset MOS transistor, 40: transfer MOS transistor, 50:
Capacitance, 60: readout transistor, 65: output signal line, 70:
Transfer MOS transistor, 80: storage capacitor, 90: output line reset MOS transistor, 100: unit circuit section.

Claims (4)

(57) [Claims] A photoelectric conversion unit for converting incident optical information into an electric signal; a read transistor for amplifying and reading out a signal from the photoelectric conversion unit via a control electrode region of the transistor; and a signal for the photoelectric conversion unit. And first and second transfer transistors connected between the photoelectric conversion unit and the control electrode region of the read transistor, for transferring the data to the control electrode region of the read transistor; and the first transfer And a plurality of unit circuit units including a reset transistor for supplying a reset potential, which is connected between the transistor and the second transfer transistor, are arranged in a horizontal direction and a vertical direction. A vertical direction in which a signal from the read transistor in the unit circuit section is read, which is provided for each of the arranged unit circuit sections. A power line, a plurality of first signal lines commonly connected to a control electrode region of the first transfer transistor in each of the plurality of horizontal unit circuit portions, and a plurality of first signal lines in each of the plurality of horizontal unit circuit portions. A plurality of second signal lines commonly connected to a control electrode region of the second transfer transistor; and a plurality of second signal lines commonly connected to a control electrode region of the reset transistor in a plurality of unit circuit units in the vertical direction, respectively. A plurality of third signal lines; a first transfer selection unit for supplying a drive pulse to an arbitrary first signal line of the plurality of first signal lines; and a plurality of third signal lines; A second transfer selection unit that supplies a drive pulse to an arbitrary second signal line; and a reset selection unit that supplies a drive pulse to an arbitrary third signal line of the plurality of third signal lines. Imaging device having the same. 2. An array of pixels, an exposure time setting means for setting a first exposure time or a second exposure time shorter than the first exposure time for the pixels, and a signal from the pixels. Is the first exposure time,
Determining means for determining whether the exposure time is the second exposure time; and determining whether the signal of the pixel is the first exposure time or the second exposure time based on the determination result of the determining means. An imaging apparatus comprising: a control unit configured to compare with a different predetermined value, control the exposure time setting unit based on a comparison result, and set the exposure time to the first exposure time or the second exposure time. 3. An image pickup apparatus according to claim 2, wherein said exposure time setting means sets a predetermined one area included in said plurality of pixels different from an area other than said predetermined one area. An imaging device, wherein the exposure time is set. 4. A case where a signal of a first exposure time or a second exposure time shorter than the first exposure time is output from a plurality of arranged pixels, and the signal is the signal of the first exposure time. Comparing with the first predetermined value, and setting the exposure time of the plurality of arranged pixels to the first exposure time or the second exposure time based on the comparison result, If the signal is for the exposure time of
And an exposure time for the plurality of arranged pixels is set to the first exposure time or the second exposure time based on a result of the comparison.