JPH03248686A - Image pickup device - Google Patents

Abstract

PURPOSE:To take the picture of a high luminance subject without depending on the precision of a mechanical iris mechanism by taking the picture by the electric charge of a smear component other than the signal charge to be generated by prescribed ratio to the signal charge to be generated in a photoelectric conversion element. CONSTITUTION:An image sensor 21 receives the light of the subject coming through a camera lens 23, the iris mechanism 24, and a beam splitter 25 during the interval of the opening and the closing of a shutter mechanism 22, and sends a signal to a video signal circuit 30. An exposure control circuit 27 receives the signal from a light receiving element 26, and controls the drive of the mechanisms 24 and 22. The operation of the circuit 27 is controlled by a system controller 28. The controller 28 controls a CCD drive circuit 29, the video signal processing circuit 30, and a recording control circuit 31 in addition to the circuit 27. Switching for the photographing of the high luminance subject is executed by the circuit 27 and the controller 28, and if unnecessary charge (smear component) is 0.1% to the signal charge of a solid state image pickup device, the signal charge is 1000 times as large as the unnecessary charge, and shutter speed for obtaining a video image by the unnecessary charge can be set 1000 times slow.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an imaging apparatus that applies a charge-coupled solid-state imaging device to an image sensor, and particularly relates to an imaging apparatus that applies a charge-coupled solid-state imaging device to an image sensor. Related to device technology and circuit technology.

[Prior Art] A conventional imaging device is a still image imaging device such as an electronic still camera, in which a charge-coupled solid-state imaging device is applied as an image sensor, and a diaphragm mechanism is provided in front of the light receiving area of the solid-state imaging device. An imaging optical system such as a shutter mechanism and an imaging lens is arranged, and an optical image of a subject passing through these imaging optical systems is received by a plurality of photoelectric conversion elements arranged and formed in a matrix in the light receiving area. It is configured.

Furthermore, a charge transfer path is formed adjacent to the plurality of photoelectric conversion elements formed in the light receiving region, and pixel signals integrated in the photoelectric conversion elements by exposure are scanned and read out via the charge transfer path.

Note that the diaphragm mechanism and the shutter mechanism control the opening amount of the diaphragm and the shutter speed so that an optimal imaging state is obtained with respect to the brightness and moving speed of the subject.

[Problems to be Solved by the Invention] However, in the conventional imaging device, when imaging the high-brightness subject, there has been a problem that the imaging accuracy decreases due to the following reasons.

In other words, mechanical aperture mechanisms have a mechanical problem in that aperture accuracy decreases as the aperture amount becomes smaller.
Furthermore, it has been difficult to realize highly accurate exposure control due to problems such as a mechanical shutter mechanism having a limit in high-speed shutter opening/closing operations.

The present invention has been made in view of the problems of the prior art, and in particular, it is an object of the present invention to provide an imaging device that can image a high-brightness subject without relying on the accuracy of a mechanical diaphragm mechanism. shall be.

[Means for Solving the Problem] In order to achieve such an object, the present invention provides an imaging apparatus that performs imaging using a charge-coupled solid-state imaging device. We decided to receive the smear component that enters the charge transfer path as a pixel signal. That is, for example, charges generated in the P-well where a photoelectric conversion element is formed and leaked into the charge transfer path, and smear components leaked into the charge transfer path for transferring the signal charge due to diffused reflection, etc., are read out as pixel signals. Realize imaging.

[Function] According to the present invention having such a control means, the amount of charge of the smear component leaking into the transfer channel is extremely small compared to the amount of signal charge generated in the photoelectric conversion element during the exposure period. The shutter time can be opened for a long time or the aperture diameter can be increased in accordance with the magnification of the signal charge amount and the charge amount generated from sources other than the photoelectric conversion element, and mechanical accuracy is not affected. Therefore, low-speed shutter photography of a high-brightness subject and highly accurate exposure control are possible.

[Example] Hereinafter, an example of an imaging device according to the present invention will be described with reference to the drawings. In addition, FIG. 1 is a schematic configuration diagram of a charge-coupled solid-state imaging device, FIG. 2 is a partial plan view of a light-receiving region, FIG. 3 is a vertical cross-sectional view of the main part of the charge-coupled solid-state imaging device, and FIG. 4 5 is a schematic vertical sectional view for explaining potential level control, and FIG. 5 is a schematic configuration diagram of an electronic still camera.

The feature of this embodiment is that the signal charge generated in the photoelectric conversion element corresponding to the pixel is not used as the video signal, but the snare component generated in the area other than the photoelectric conversion element is used to obtain the video signal. However, for convenience of explanation, the overall structure of the charge-coupled solid-state imaging device will be explained with reference to FIG. 1, and then the circuit structure and operation will be explained.

This charge-coupled solid-state imaging device is an interline type device, and receives an optical image of a subject formed through an imaging optical system of an electronic still camera, for example, in a light-receiving region 1 . Then, signal charges generated in a group of photoelectric conversion elements such as photodiodes arranged and formed in a matrix in the light receiving area 1 are transferred to a four-phase drive signal φ1. φ2. φ3. The charge transfer path is configured to read data in synchronization with φ4.

3 is a horizontal charge transfer path, and the signal charge transferred from the charge transfer path in the light receiving area 1 is transferred to a two-phase drive signal φ11.
．． It is serially transferred to output terminal 4 in synchronization with φ12.

Further, to describe the structure of the light receiving region 1 in detail with reference to FIG. 2, a plurality of n-type impurity layers are formed in a matrix in a P-type impurity layer (P-well) formed on the front side of the semiconductor substrate. By this, a plurality of photodiodes Pd1l ~P
d1n, Pd21-Pd2n.

P d31 to P d3n ・------- is the saletail formed.

Between these photodiodes (hereinafter collectively referred to as Pd1j), there are a plurality of charge transfer paths Ll, L2, L3 for transferring signal charges.
(hereinafter collectively referred to as Lj) is formed. In addition, each photodiode Pd1j and charge transfer path Lj
The hatched area surrounded by dotted lines in the figure except for is the channel stopper.

A plurality of transfer electrodes Gl made of a polysilicon layer extending in the horizontal direction are provided on the upper surface of the charge transfer path Lj.

G2, G3-...- (hereinafter collectively referred to as Gj)
are arranged in parallel, and drive signals φ1 to φ4 based on a four-phase drive method at predetermined timings, which will be described later, are applied to four mutually adjacent transfer electrodes as one set. That is, photodiodes arranged along each column (for example, P dllPd12 ,
2 for Pd13 ------- Pd1n )
The transfer electrodes (for example, C1, G2) are associated with each other, and mutually adjacent transfer electrodes partially overlap to avoid creating unnecessary potential barriers. Note that the signal charge generated in each photodiode P dij is transferred to the transfer gate Tgll.

7g12, Tg13 --- to be outputted to the corresponding charge transfer path Lj.

Next, the cross-sectional structure of the light receiving area 1 will be explained based on FIG.

That is, a P-type diffusion region 12 (hereinafter referred to as
A P-well) is formed. A photodiode Pd is formed in the P well 12, and a reverse bias voltage is applied between the P well 12 and the n-type substrate 11.
2 is depleted.

Further, the charge transfer path Lj is formed in the P well 12, and the transfer electrode Gj made of a polysilicon layer is formed above the charge transfer path Lj.
, an aluminum shielding plate 13 is formed. A transfer gate TG is formed between the photodiode Pd and the charge transfer path Lj, and a transfer gate TG is formed between the photodiode Pd and the charge transfer path Lj.
It is configured to transfer the signal charge generated at point d to the charge transfer path Lj. In addition, in Fig. 3, the photodiode Pd
A channel stop 14 is formed on the left side of the charge transfer path Lj and on the right side of the charge transfer path Lj.

Next, the potential well during light reception will be explained. When light hv, which is an optical object image, is incident on the photodiode Pd, signal charges are accumulated on the photodiode Pd. During normal photographing, the accumulated signal charges are transferred to the charge transfer path Lj via the transfer gate TG. Then, after accumulating signal charges by controlling the potential well of the charge transfer path Lj from the depth shown by the dotted line in FIG. 3 to the depth shown by the solid line, the drive signals φ1 to The charges are sequentially transferred and read out in the three directions of the horizontal charge transfer path by φ4.

In contrast to the normal imaging, when photographing a high-precision, high-brightness object, the following light reception and charge transfer are performed.

That is, when imaging a high-brightness object, the potential well of the charge transfer path Lj is set in advance to a desired depth as shown by the solid line in FIG. However, in this setting, the charge transfer path Lj
The setting is not performed over the entire route, but is set intermittently as shown in FIG.

At the time of light reception, light hv is incident on the photodiode Pd, and leaked light is incident on the charge transfer path Lj. Although a signal charge is generated in the photodiode Pd, it does not drive the transfer gate Tg, so the photodiode P
The signal charge generated at d is not transferred to the charge transfer path Lj. On the other hand, when there is incident light on the photodiode Pd, unnecessary charges are generated in the P well 2 below the photodiode Pd. Further, unnecessary charges are also generated in the vertical charge transfer path Lj due to leakage light incident on the charge transfer path Lj. These unnecessary charges correspond to charges other than signal charges in the present invention, and were conventionally swept out onto the n-type substrate 11 as a cause of smear.

However, in this embodiment, by actively utilizing the unnecessary charges that have been swept away, in other words, charges other than signal charges, it is possible to image a high-luminance subject with high exposure accuracy.

If the shutter speed is 1/60sec, F5.6
, if the unnecessary charge (smear component) is 0.1% of the signal charge of a solid-state imaging device that can obtain an image with 100% output under the condition of light intensity of 4000 Lux, the signal charge is 1000 times the unnecessary charge. be.

Therefore, the shutter speed for obtaining an image using unnecessary charges is determined to be 61 sec. Similarly, the aperture may be opened.

Similarly, in a solid-state imaging device in which the unnecessary charge is 0.01% of the signal charge, the shutter speed is 10,000 times higher, and a long-time shutter of 167 seconds is possible. Similarly, you can open the aperture.

In this way, in this embodiment, unnecessary charges are used to perform highly accurate exposure and high-brightness subject photography, and this is made possible by controlling the potential well of the charge transfer path Lj.

That is, by fixing the levels of the drive signals φ1 to φ4, the potential well of the charge transfer channel Lj is intermittently deepened as shown in FIG. 4, and the transfer gate Tg is set to a high level. As a result, the aperture mechanism,
Even if light hv is incident on the photodiode Pd with the shutter mechanism open, the signal charges accumulated in the photodiode Pd are no longer transferred to the charge transfer path Lj.

On the other hand, during the exposure period, charges generated in the P-well 12 flow into the charge transfer path Lj and are accumulated together with charges generated in the charge transfer path Lj in response to leakage incident light.

However, unless the phase of the drive signals φl to φ4 is changed, the charge transfer path Lj does not transfer charges.
The amount of charge accumulated in j gradually increases. When the shutter mechanism is closed after a predetermined period of time has elapsed, the levels of the drive signals φ1 to φ4 sequentially change in a pulse-like manner in conjunction with this. φ
4 is applied, the potential well under the electrode is controlled deeply, and the drive signal φ1. The charges accumulated under the electrode to which φ3 is applied are transferred. Such charge transfer is performed for each charge transfer path Lj, and the charges are transferred to the horizontal charge transfer path 3 as explained in FIG.

The signal charge accumulated in the photodiode Pd is swept out to the n-type substrate 11 using a VOD structure known to those skilled in the art. That is, a voltage higher than that during normal operation is applied to the n-type substrate 11, and the n-layer, P-well 12, and n-type substrate 11 forming the photodiode Pd realize a structure similar to that of an npn transistor, and the signal charge is is swept out onto the n-type substrate 11. At this time, the potential below the photodiode Pd is the surrounding area, that is,
Since the potential is higher than the area of the channel stop 14 and the upper and lower potentials of the charge transfer channel Lj, signal charges do not flow into the charge transfer channel Lj.

Next, an example of an electronic still camera having the function of capturing an image of the high-brightness subject will be described.

FIG. 5 is a schematic configuration diagram of an electronic still camera.

This electronic still camera is provided with the image sensor 21 having the configuration described above. The charge-coupled solid-state imaging device 21 receives object light that has passed through the imaging lens 23, diaphragm mechanism 24, and beam splinter 25 while the shutter mechanism 22 is opening and closing, converts the optical image into an electrical signal, and converts the optical image into an electrical signal to send it to a video signal processing circuit. Output to 30.

The shutter mechanism 22 and the aperture mechanism 24 are provided to adjust the amount of exposure to the charge-coupled solid-state imaging device 21. In order to determine this exposure amount, a part of the subject light extracted by the beam splitter 25 is sent to the light receiving element 2.
6, and the output from the light receiving element 26 is transmitted to the exposure amount m circuit 2.
7 is input. The exposure control circuit 27 calculates the aperture value and shutter speed corresponding to the subject brightness based on the signal output from the light receiving element 26, and controls the driving of the aperture mechanism 24 and the shutter mechanism 22. Note that the operation of the exposure control circuit 27 is controlled by a system controller 28 composed of a microcomputer.

Here, we will discuss high-brightness subject photography. In the charge-coupled solid-state imaging device 21, the signal charge generated in each photodiode and the P well 12 and charge transfer path Lj
The ratio to the charge generated from is constant. Therefore, the exposure control circuit 27 and the system controller 2 that controls it
8, if the amount of charge is 1000 times as much as in the previous example, the shutter time will be changed to 1000 times based on the signal output from the light receiving element 26.
Set to double. At this time, an aperture value that allows the shutter time to be shorter than the above and the aperture to be opened is also set, but the aperture value may be the same as in normal photography.

This electronic still camera also incorporates a finder optical system consisting of a quick return mirror and a pentaprism, but these are omitted to avoid complicating the drawings.

The system controller 28 controls the operations of a CCD drive circuit 29, a video signal processing circuit 30, and a recording control circuit 31 in addition to the exposure control circuit 12. That is, the release button 32
When the half-press signal a is supplied from the release operation detection circuit 32 to the system controller 28, the system controller 28 outputs a photometry timing signal to the exposure control circuit 27. As a result, the exposure control circuit 12 detects the light receiving element 2.
6, the subject brightness information is taken in, and the aperture value and shutter speed are calculated. This calculation is performed in the same way when using a long shutter.

Further, when a signal indicating that the release button 32a is pressed is inputted from the release operation detection circuit 32 to the system controller 28, the aperture 24 and shutter 22 are driven according to the aperture value and the shutter speed calculated by the exposure control @path 27. , the charge-coupled solid-state imaging device 21 is irradiated with subject light at an appropriate amount of exposure.

The CCD drive circuit 29 drives the charge-coupled solid-state imaging device 21 in synchronization with the timing clock TP from the system controller 28 . This timing clock 1
/60 seconds, that is, it has a period equal to one vertical scanning period (one field period; 1v) in the standard television system.

In this electronic still camera, in order to capture video signals using a frame imaging method, the CCD drive circuit 29 supplies the first field pulse F to the charge-coupled solid-state image device 21.
SA, second field pulse FSB, vertical transfer pulse φ
V (corresponding to the drive signals φ1 to φ4) and a horizontal transfer pulse φH (corresponding to the drive signals φ11 to φ12). The first field pulse FSA and the second field pulse FSB each correspond to the timing clock 1.
/02 times the period, and the phases are shifted from each other by half a period. Further, each of the vertical transfer pulse φV and the horizontal transfer pulse φH sends out a video signal for each field from the charge-coupled solid-state imaging device 21 during one period (1■) of the timing clock TPO.

The video signal processing circuit 30 converts the video signal serially output from the charge-coupled surface gymnastics image device 21 into an output signal compliant with, for example, the NTSC system. The output signal thus obtained is supplied to a recording device 34 via a buffer circuit 33 controlled by a recording control circuit 31. The recording device 34 includes, for example, a device that digitally converts the output signal supplied from the buffer circuit 33 and then writes it into a card-type semiconductor memory, so that video data of still images can be recorded. become. Note that the recording device 34 may be a disk device that magnetically records the output signal on a still video floppy.

Note that the present invention can be applied to any appropriate charge-coupled solid-state imaging device. In addition, in order to obtain the photographic effect only by the charge of the smear component, it is preferable to reduce the influence of dark current from the semiconductor substrate side, so it is preferable to form the charge transfer path as close to the surface layer of the semiconductor substrate as possible. Effective.

Further, the present invention can be applied to a charge-coupled stationary image device that performs color imaging.

[Effects of the Invention] As described above, the imaging device according to the present invention performs imaging using charges of a smear component other than signal charges generated at a predetermined ratio to signal charges generated in a photoelectric conversion element of an image sensor. This is how it was done. Therefore, the shutter time can be lengthened in accordance with the predetermined ratio, making it possible to photograph high-brightness objects with high precision without having to strictly adjust the light reception of the image sensor using a mechanical aperture mechanism. , the imaging device can be used for multiple purposes.

[Brief explanation of drawings]

1 to 5 show an embodiment of an imaging device to which the present invention is applied, in which FIG. 1 is a schematic configuration diagram of an image sensor, FIG. 2 is a plan view of the main part of the light receiving area, and FIG. FIG. 3 is a longitudinal sectional view of the light receiving area of the image sensor, FIG. 4 is a schematic sectional view showing control of the potential well of the charge transfer path, and FIG. 5 is a schematic configuration diagram of the electronic still camera. Codes in the figure: 1... Light receiving area, 211. Scanning circuit, 3... Horizontal charge transfer path, 4... Output terminal, 11... N-type substrate, 12 ・ 13 ・ 14 ・ 21 ・ 22 ・ 23 ・ 27 ・ 28 ・ Pd ・ Lj ・ φν, h ν ...P well, ...shielding plate, ...channel stopper, ...charge-coupled solid-state imaging device, ...shutter mechanism, ...aperture mechanism, ...exposure control circuit, ...system controller, ... Photodiode, ...charge transfer path, φH...drive signal, ...incident light.

Claims (1)

[Claims] An optical image of a subject passing through a shutter mechanism and an aperture mechanism is captured by a plurality of photoelectric conversion elements formed in a light-receiving area of a charge-coupled solid-state imaging device, and the optical image generated in these photoelectric conversion elements is An imaging device that scans and reads out pixel signals through a charge transfer path, wherein a smear component mixed into the charge transfer path is received as a pixel signal during an exposure period in which the shutter mechanism is opened.