JP2003204489A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a device by which the video signal of a subject having large brightness difference can be obtained at an optimum level without a saturation by one imaging device. <P>SOLUTION: In the imaging apparatus in which an optical image is photoelectric-converted and the video signal is obtained by storing the charges of the optical image, a means for changing a saturation quantity of charges stored in the imaging apparatus in response to the level of the video signal acquired by the imaging device is provided, non-linear characteristics are imparted to the obtained video signal, and the video signal of the subject having high brightness difference is acquired at the optimum level without saturation. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for converting a subject having a large luminance difference into a video signal without saturation.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, in an image pickup device of a television camera device, a photosensitive portion P and an accumulating portion Q are two-dimensionally arranged by the number of pixels, and charges photoelectrically converted by the photosensitive portion P are arranged. Is stored in the storage unit Q to extract a video signal, C
CD (Charge Coupled Device) type image sensor and MOS (Meta
l Oxide Semiconductor) type image sensor. CCD
In the case of the image pickup device, the light signal I incident in the vertical image period is photoelectrically converted in the photosensitive portion P, the charges are accumulated in the accumulation portion Q, and the charges in the accumulation portion Q are simultaneously transferred to the vertical transfer portion VC in the vertical blanking period. Transferred to. The charges transferred to the vertical transfer unit VC are transferred line by line to the horizontal transfer unit HC during the horizontal blanking period, and the charges of the horizontal transfer unit HC are read out during the video period to extract the video signal V.

[0003]

In the above, as shown in FIG. 4, the storage portion Q is composed of the electrode 4, the insulator 5, and the n-type semiconductor 6, and the substrate voltage D is applied to the electrode 4 and the n-type semiconductor 6. By applying the charge, a potential well is formed and the charge 7 is accumulated. As shown in FIG. 6, one image is recorded in the erase period T
The charge is reset by setting the substrate voltage D to 0 at 0,
By setting the substrate voltage D to D2 in the accumulation period T3, the accumulation unit Q
The charge is accumulated in. By repeating this operation, a moving image signal can be obtained. Here, when a high-luminance subject that exceeds the capacity of the potential well is incident on the optical signal I, the video signal V is saturated. In order to prevent this saturation, as shown in FIG. 5, when the video signal V is saturated in the shutter speed control circuit 3, as shown in FIG.
An electronic shutter system in which the accumulation period T5 of the accumulation unit Q of the entire image sensor 1 is short, the erasing period T4 is long, and the exposure time is shortened by adding the substrate voltage D so that the video signal V is not saturated. There is. However, when the exposure time is limited by this electronic shutter method or the like, the subject of low brightness has a problem that the level of the video signal becomes small and it becomes impossible to take an image. Therefore, in the conventional image sensor, about 4
The double dynamic range is the limit. The present invention eliminates these drawbacks and has means for varying the amount of charge saturation,
It is an object of the present invention to realize a device capable of obtaining a video signal of a subject having a large luminance difference at an optimum level without saturation by giving a video signal a non-linear characteristic.

[0004]

In order to achieve the above object, the present invention provides an image pickup device which obtains a video signal by photoelectrically converting an optical image and accumulating the electric charge of the optical image. It has a means for varying the saturation amount of the electric charge accumulated in the image sensor according to the level, and gives the obtained video signal a non-linear characteristic, so that the video signal of a subject with a large luminance difference is not saturated, but at an appropriate level. It's something I got to get. In addition, the accumulated electric charge of the image sensor is saturated at a predetermined level V1 from 0 in a video signal of a low-luminance subject in the first accumulation period T1, and a predetermined video signal of a high-luminance subject in the second accumulation period T2. Level V1 to predetermined level V2
It is controlled so as to saturate at. As a result, it is possible to obtain a video signal of a subject having a large luminance difference without saturation and at an optimum level, and it is possible to take out a video signal having a wide dynamic range.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, as one embodiment of the present invention,
The configuration and operation of this device will be described in detail with reference to FIGS. I is the incident optical signal, D is the substrate voltage that controls the charge accumulated in the image sensor 1, V is the video signal, 1 is the image sensor that converts the optical signal I into the video signal V, and 2 is the level of the video signal V Is a voltage control circuit for controlling the electric charge accumulated in the image sensor 1 in accordance with the above. The incident optical signal I is photoelectrically converted by the image sensor 1 and a video signal V is output. The video signal V is input to the voltage control circuit 2, and the voltage D1 is added as the substrate voltage D so that the video signal V is saturated at a predetermined level V1 in the storage period T1 shown in FIG. Is the substrate voltage D and the video signal V is at a predetermined level V2.
The voltage D2 is added so as to be saturated at (for example, the 100% level of the rating). By the above operation, the video signal of the low-luminance subject is assigned to the level of 0 to V1 in the accumulation period T1, and the video signal of the high-luminance subject is V level in the accumulation period T2.
It is assigned to levels from 1 to V2. As a result, the video signal V2 stored in the storage period T2 is added to the video signal V1 stored in the storage period T1, and the video signal V having a nonlinear characteristic with respect to the optical signal I is obtained without being saturated. In the present embodiment, the CCD image pickup method has been described as an example of the image pickup element 2, but the present invention is not limited to this, and a MOS type image pickup device that obtains a video signal by photoelectrically converting and accumulating the electric charge. Is also applicable.

[0006]

According to the present invention, it is possible to obtain an image signal of a subject having a large luminance difference with one image sensor at an optimum level without being saturated at the same subject position, and to capture an image of a wide dynamic range. A device can be provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of the present invention.

FIG. 2 is a timing chart showing the operation of the present invention.

FIG. 3 is a block diagram showing the configuration of a general image sensor.

FIG. 4 is a block diagram showing a configuration of a storage unit of a general image pickup device.

FIG. 5 is a block diagram showing a conventional overall configuration.

FIG. 6 is a timing chart showing a conventional operation.

FIG. 7 is a timing chart showing a conventional electronic shutter operation.

[Explanation of symbols]

I: Optical signal, V: Video signal, D: Substrate voltage, P: Photosensitive portion, Q: Storage portion, VC: Vertical transfer portion, FM: Frame storage portion, HC: Horizontal transfer portion, T0: Erase period, T1, T
2: accumulation time, D1, D2: substrate voltage, V1, V2: video level, 1: image sensor, 2: voltage control circuit, 3: shutter speed control circuit, 4: electrode, 5: insulator, 6: n
Type semiconductor, 7: electric charge.

Claims (2)

[Claims] 1. An image pickup apparatus for obtaining a video signal by photoelectrically converting an optical image and accumulating the electric charge in the image pickup apparatus, wherein a saturation amount of the electric charge accumulated in the image pickup element according to the level of the video signal obtained from the image pickup element. And an image pickup device having a means for varying the obtained image signal to have a non-linear characteristic so that the image signal of a subject having a large luminance difference is obtained at an appropriate level without being saturated. 2. The charge saturation amount varying means according to claim 1, wherein the accumulated charge of the image pickup device is saturated from 0 to a predetermined level V1 in a video signal of a low-luminance subject during a first accumulation period T1. , The video signal of the high-luminance subject is changed from the predetermined level V1 to the predetermined level V during the second accumulation period T2.
An image pickup device characterized in that the image pickup device is a means for controlling so as to be saturated at 2.