JP2930313B2 - Electronic imaging device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electronic imaging device that captures and inputs an image of a subject using a solid-state imaging device such as a CCD.

2. Description of the Related Art Recently, an electronic imaging apparatus that electronically captures and inputs an image of a subject using a solid-state imaging device such as a CCD and records the image signal (electronic still image) on a floppy disk or a memory card has been developed. It is attracting attention as an electronic still camera.

This type of electronic still camera is essentially different from a conventional general still camera using a silver halide film in that a so-called element shutter can be used. This element shutter is realized by photoelectrically converting a subject image and controlling the accumulation time of signal charges in a solid-state imaging device that accumulates signal charges according to the light amount of the subject image. Specifically, a high-speed shutter is realized by setting the accumulation time of the signal charge in the solid-state imaging device to be short, and a low-speed shutter is realized by setting the accumulation time to be long.

[Problems to be Solved by the Invention] However, there are the following problems in an electronic imaging apparatus employing this type of element shutter. That is, the signal charge corresponding to the light amount of the subject image accumulated by the solid-state imaging device is controlled only by the accumulation time. Because of this,
Even after the accumulation of the signal charge ends with the elapse of the predetermined accumulation time in the solid-state imaging device, the imaging surface of the solid-state imaging device is continuously irradiated with the subject image. The reduction is a state in which the subject image having the same image plane illuminance as that during the exposure is directly irradiated onto the imaging surface of the solid-state imaging device even after the subject image is exposed at an appropriate image plane exposure amount.

Irradiation of an unnecessary subject image after exposure to the imaging surface of such a solid-state imaging device is a cause of smear when reading out signal charges from the solid-state imaging device,
This causes the quality of the captured image signal to deteriorate. The smear is a phenomenon in which light applied to the imaging surface of the solid-state imaging device is mixed into a transfer path for reading out signal charges to generate extra charges, or light entering the inside of the element substrate. This is a phenomenon in which unnecessary charges are mixed into signal charges accumulated according to a subject image due to diffusion. In particular, when the solid-state image sensor is operated at a high-speed shutter operation by the above-described element shutter, the image plane illuminance is increased to accumulate a predetermined signal charge in the solid-state image sensor. There was a problem of becoming.

The present invention has been made in view of such circumstances,
It is an object of the present invention to provide an electronic imaging apparatus capable of capturing an image of a subject with high quality by an element shutter using a solid-state imaging element without causing a problem of smear.

[Means for Solving the Problems] In order to solve the above problems and achieve the object, an electronic imaging apparatus of the present invention is configured as follows.

An electronic imaging apparatus according to the present invention includes: an imaging optical system that forms an image of a subject at a predetermined position; a light amount adjusting unit that adjusts an incident light amount of a subject image formed by the imaging optical system; A finder for observing a subject image whose incident light amount is adjusted by a light source, and a signal corresponding to the light amount of the subject image which is provided at a position where the subject image is formed and photoelectrically converts the subject image formed at the position. A solid-state imaging device that accumulates electric charges, a solid-state imaging device driving unit that controls accumulation of signal charges by the solid-state imaging device and reading of the accumulated signal charges, and accumulation in the solid-state imaging device by the solid-state imaging device driving unit. In the readout period in which the readout control of the read signal charges is performed, the light amount adjusting means is driven to store the signal charges in the light amount of the subject image formed on the solid-state imaging device. It is characterized by comprising a control means for suppressing the smaller amount than the amount of time that.

According to another electronic imaging apparatus of the present invention, an imaging optical system that forms an image of a subject at a predetermined position, and the amount of incident light of the subject image formed by the imaging optical system according to an exposure control state during shooting. A light amount adjusting means for adjusting the amount of incident light, and a solid-state member provided at an image forming position of the object image, photoelectrically converting the object image formed at the position, and accumulating signal charges corresponding to the light amount of the object image. An imaging device, a solid-state imaging device driving unit that controls accumulation of signal charges by the solid-state imaging device and reading of the accumulated signal charges, and a solid-state imaging device driving unit that controls the accumulation of signal charges by the solid-state imaging device. In the reading period in which the reading control is performed, the light amount adjusting means is driven to reduce the light amount of the subject image formed on the solid-state imaging device to the light amount corresponding to the minimum light amount value by the light amount adjusting means. It is characterized by comprising a control means.

[Operation] According to the electronic imaging device of the present invention configured as described above, when the element shutter is realized by controlling the accumulation time of the signal charges in the solid-state imaging element, the solid-state image sensor after the predetermined signal charge accumulation time is completed. Since the amount of irradiation of the subject image onto the imaging surface of the imaging device is reduced, it is possible to suppress unintended light (subject image) irradiation after accumulation of signal charges, and to prevent unnecessary light from entering the imaging surface. ) Can be effectively suppressed. As a result, even when a large amount of image plane light is introduced during the high-speed shutter operation, it is possible to prevent the occurrence of smear and prevent the quality of the image plane signal from deteriorating.

Hereinafter, a solid-state imaging device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic configuration diagram of an embodiment apparatus, and 1 is an image pickup optical system that forms an image of a subject at a predetermined position. The imaging optical system 1 is generally composed of a plurality of optical lenses, and incorporates therein an aperture mechanism (light amount adjusting means) 2 for adjusting the incident light amount of the subject image.

Then, a CCD 3 which is a solid-state image sensor is provided at an image forming position of a subject image which is formed through the imaging optical system 1 and whose light amount is adjusted by the aperture mechanism 2 and input.
The CCD 3 photoelectrically converts the subject image and inputs the image. A half mirror 4 is provided in the optical path of the imaging system, and a subject image forming a part of the incident light reflected by the half mirror 4 is focused on a focusing glass 5.
The image is formed on the upper side and can be visually recognized through a finder system including the half mirror 6 and the eyepiece 7. The half mirror 6 guides a part of the subject image formed on the focus glass 5 to the photometric sensor 8 and measures the amount of incident light (the amount of the subject image).

This apparatus employs a single-lens flex type optical system using the half mirror 4 as described above, and is configured so that an image of a subject captured by the CCD 3 can be confirmed as it is via the finder system.

The light quantity (brightness) of the subject image detected and received by the photometric sensor 8 is measured by the photometric circuit 11. The exposure control circuit 12 controls the aperture drive circuit 13 and the shutter drive circuit 14 according to the photometric value of the subject image measured by the photometric circuit 11, so that the exposure value of the subject image captured by the CCD 3 becomes appropriate. To

That is, the CCD 3 photoelectrically converts the subject image formed on the imaging surface, accumulates a signal charge corresponding to the light amount,
The subject image is captured by reading out the stored signal charges. In this way, the image signal of the subject image picked up and input by the CCD 3 is given to the image pickup circuit 15 and subjected to processing such as separation into respective color components of three primary colors. Then, the data is recorded and output on a predetermined recording medium (floppy disk or memory card) via the recording circuit 16.

For such an imaging system, the aperture driving circuit 13 drives the above-described aperture mechanism 2 under the control of the exposure control circuit 12, and the subject image formed on the imaging surface of the CCD 3 via the imaging optical system 1. The amount of light is controlled to be narrowed down so that the amount of light becomes an appropriate amount equal to or less than a predetermined image plane illuminance. That is, the aperture mechanism 2
The aperture diameter of the aperture is variably controlled by driving the aperture blades, thereby adjusting (suppressing) the incident light amount of the subject image.

Thus, the shutter drive circuit 14 realizes an element shutter by variably controlling the accumulation time of the signal charges by the CCD 3, and its operation is controlled under the control of the exposure control circuit 12. The control of the signal charge accumulation time by the shutter drive circuit 14, that is, the control of the exposure time for the subject image, is performed in connection with the adjustment of the incident light amount by the aperture mechanism 2 described above. The control is performed such that the aperture value and the exposure time (accumulation time of the signal charge) satisfy a predetermined relationship in accordance with the imaging capability possessed.

More specifically, the imaging capability Lv with respect to the subject luminance is calculated as the sum of the subject luminance Bv and the sensitivity Sv of the imaging signal processing system including the CCD 3 Lv = Bv + Sv Bv = log ₂ (B / K) B; −L] K; Exposure calibration coefficient (generally 1.1 to 1.4) Sv = log ₂ (ISO / 100) +5 However, ISO indicates the sensitivity of the image signal processing system as I
This is the value when expressed in SO speed.

On the other hand, the exposure control ability Ev by the above-described aperture value control and exposure time (accumulation time of signal charge) control is Ev = Av + Tv Av = log ₂ F ² Tv = log ₂ (1 / T) F; aperture value T; shutter speed [sec]. The exposure control circuit 12 controls the aperture drive circuit 3 and the shutter drive circuit 14 so that the relationship of Ev = Lv (Av + Tv = Bv + Sv) is obtained according to the brightness value B of the subject measured by the photometry circuit 11. The exposure is controlled so as to obtain an appropriate exposure by controlling the exposure.

Here, when the shutter release switch 18 is pressed, the system controller 17 controls a series of processing operations for driving the above-described units at the timing shown in FIG. 2 to capture and input a subject image. This system controller 17
The characteristic aperture control in the present apparatus is included in the operation control process of the present invention.

That is, the present apparatus is configured to perform the imaging operation in synchronization with a predetermined timing pulse VD, and to perform the imaging operation in synchronization with the next timing pulse VD after the detection of the turning-on of the shutter release switch 18. The operation starts.
In this imaging operation, first, the aperture driving circuit 13 is controlled in accordance with the amount of light (luminance) of the subject measured by the photometric circuit 11,
This is performed by adjusting the incident light amount (aperture control) so that the light amount (image surface illuminance) of the subject image formed on the image pickup surface of the CCD 3 via the image pickup optical system 1 can have an appropriate exposure value [ Processing in FIG. 2]. The aperture control may be automatically determined according to the amount of incident light according to a program diagram of a predetermined aperture value and shutter speed, but the shutter speed is set with priority. In such a case, when the aperture value is set so as to match the shutter speed and the control is performed, or when the aperture value is preferentially determined, the aperture value is controlled to be reduced to the set aperture value. In some cases.

After the aperture control for the incident light amount of the subject image is performed in this manner, the state is maintained, and then the shutter drive circuit 14 is controlled to perform accumulation (exposure) control of signal charges corresponding to the subject image. . The accumulation control of the signal charges is performed by controlling the accumulation time of the signal charges in the CCD 3 over the time set in relation to the above-mentioned aperture value. After the subject image is thus photoelectrically converted and its signal charge is controlled to be stored, a pulse indicating the end of the exposure is detected and the signal charge stored in the CCD 3 is read out (transfer output). Then, it controls the driving of the recording circuit 16 to execute a recording process of signal charges read from the CCD 3, that is, a captured image signal.

However, when reading out the signal charges from the CCD 3 as described above, the present apparatus controls the aperture driving circuit 13 again in parallel with this to further reduce the amount of incident light as compared with the time of exposure of the subject image. The narrowing control is performed as much as possible.

That is, when the above-described exposure end pulse is detected,
The exposure control circuit 12 is completely independent of the above-described exposure control,
The diaphragm mechanism 2 is driven over the period of reading out the signal charges from the CCD 3, and the incident light amount is controlled to be reduced / suppressed by, for example, setting the minimum diaphragm value [processing shown in FIG. 2]. The aperture control at this time is completely independent of the exposure control when capturing the subject image, and is intended to prevent unnecessary light that causes smear from being irradiated on the imaging surface of the CCD 3 after the exposure is completed. It is done in.

After reading out the signal charges from the CCD 3 and recording the image signal under the condition that the aperture stop control of the incident light is performed, the above-described aperture drive circuit 13 is driven again to open the aperture value. [Process shown in FIG. 2].
Although this process is not related to the electronic imaging of the subject image by the CCD 3, the subject image formed on the focusing glass 5 is brightened to facilitate focusing (focusing) and composition determination. It is performed for the purpose of normalization.

Thus, according to the present apparatus configured as described above and performing the aperture control for the incident light amount as described above, after the CCD 3 performs a predetermined imaging process (exposure), the signal charges accumulated in the CCD 3 by this exposure are read out. Is performed, the amount of light incident on the imaging surface of the CCD 3 is narrowed down, so that irradiation of an extra subject image after the end of exposure can be effectively suppressed. As a result, it is possible to prevent the occurrence of smear due to the extra light and to read out the stored signal charges without deteriorating the quality of the signal charges. In particular, at the time of imaging at a high shutter speed, the imaging is performed by acquiring a larger amount of light for the shorter signal accumulation time, but such a large amount of the subject image is narrowed down after the exposure is completed. The amount of light applied to the imaging surface of the CCD 3 can be kept very low, and as a result, the occurrence of smear can be effectively prevented.

It is conceivable to use a mechanical shutter to prevent the occurrence of smear. However, if the function of the aperture mechanism 2 is used as it is as in the present apparatus, an extra mechanism such as a mechanical shutter is added. There is an effect that there is no need to carry out.

Note that the present invention is not limited to the above-described embodiment. For example, when employing a structure in which the viewfinder system is provided separately from the imaging system, the aperture mechanism 2 is appropriately controlled only during the signal charge accumulation period by the CCD 3, and the next time the exposure is completed, The period until the exposure starts,
The aperture value may be minimized. Although the aperture value after the exposure is set to the minimum aperture value to prevent the occurrence of smear, it is of course possible to control the aperture value to an appropriate value other than the minimum aperture value. In the above-described embodiment, an example of a mechanical diaphragm has been described. However, a light diaphragm capable of electronically adjusting the amount of transmitted light using a liquid crystal or an electrochromic phenomenon may be used. In the case where the photographing operation is continuously performed, the interval between the photographing operations can be shortened by stopping the light amount decreasing operation after the photographing. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[Effects of the Invention] According to the present invention, in a readout period in which readout control of signal charges stored in a solid-state imaging device is performed, the light-amount adjusting unit is driven to drive the light-amount of a subject image formed on the solid-state imaging device. Is reduced to at least a light amount smaller than the light amount during the period in which the signal charge is accumulated, so that the occurrence of smear can be suppressed, and the viewfinder optical system does not become completely dark. In the case of observing the subject image with a viewfinder, it is possible to observe the subject image even after shooting,
As a result, there is no danger of losing sight of the subject and missing a photo opportunity.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an electronic image pickup apparatus according to one embodiment of the present invention, and FIG. 2 is a diagram showing an image pickup operation timing in the embodiment apparatus. 1 ... imaging optical system, 2 ... stop mechanism (light amount adjusting means),
3 ... CCD (solid-state imaging device), 8 ... Photometric sensor, 11 ...
... Photometric circuit, 12 ... Exposure control circuit, 13 ... Aperture drive circuit, 14 ... Shutter drive circuit, 15 ... Imaging circuit, 16 ...
Recording circuit, 17 System controller, 18 Shutter release switch.

Claims (2)

(57) [Claims] An imaging optical system for forming an image of a subject at a predetermined position; a light quantity adjusting means for adjusting an incident light quantity of the subject image formed by the imaging optical system; and an incident light quantity by the light quantity adjusting means. A viewfinder for observing the adjusted subject image, and a photoelectric conversion of the subject image provided at the image forming position of the subject image and forming a signal charge corresponding to the light amount of the subject image. A solid-state imaging device to be accumulated; solid-state imaging device driving means for controlling accumulation of signal charges by the solid-state imaging device and reading out of the accumulated signal charges; In a readout period in which readout control of the signal charge is performed, the light amount adjustment unit is driven to adjust the light amount of the subject image formed on the solid-state imaging device to a period in which the signal charge is accumulated. Electronic imaging device being characterized in that anda control means suppresses the smaller amount than the amount. 2. An imaging optical system for forming an image of a subject at a predetermined position, and an incident light amount of a subject image formed by the imaging optical system is adjusted to an incident light amount according to an exposure control state at the time of photographing. A solid-state imaging device provided at a position where an image of the subject image is formed, photoelectrically converts the subject image formed at the position, and accumulates signal charges corresponding to the light amount of the subject image; Solid-state imaging device driving means for controlling accumulation of signal charges by the imaging device and reading of the stored signal charges; readout in which reading control of the signal charges stored in the solid-state imaging device is performed by the solid-state imaging device driving means Control means for driving the light quantity adjusting means to reduce the light quantity of the subject image formed on the solid-state imaging device to a light quantity corresponding to a minimum light quantity value by the light quantity adjusting means, Electronic imaging apparatus characterized by Bei was.