JPH04207581A - Image pickup device - Google Patents

Abstract

PURPOSE:To minimize the deterioration in image quality at the time of photographing moving pictures by executing short-time exposing in 1st exposing by utilizing the CCD shutter of the image pickup element itself and executing long-term 2nd exposing during the output of a 1st exposing signal. CONSTITUTION:The 2nd exposing longer in the exposing time than the 1st exposing is started immediately after the signal by the 1st exposing is sent from a photodiode 30c constituting a photodetecting part to a vertical transfer CCD 30b and horizontal transfer CCD 30d as transfer means. The 2nd exposing is ended after the signal by the 1st exposing is outputted from the image pickup element. The 2nd exposing of the photodetecting section 30c is executed in the period when the signal by the 1st exposing is outputted from the image pickup element. The deviation in the image pickup time by plural times of exposing is thus decreased. The image pickup device having a wide substantial dynamic range and good moving resolution is obtd. in this way.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an imaging device, and particularly to a substantially dynamic imaging device.
The present invention relates to an imaging device with a wide range.

[Prior Art] Imaging devices are widely used as video camera units such as camera-integrated VTRs and still video cameras. Video cameras that use image pickup tubes or solid-state image sensors have a narrower dynamic range than traditional silver-halide photographic systems, and as a result, when backlit, etc., whites and darks are crushed (a common term for areas with extremely high or low brightness levels). ) etc. occur.

With conventional video cameras, in such cases, the aperture can be opened by about two stops either manually or by operating the backlight compensation button.
The amount of light was being adjusted.

However, even when such backlight compensation is performed appropriately,
Even if the main subject has an appropriate exposure level, overexposure may occur in the background, resulting in a screen where only the background is white. In other words, the narrow dynamic range of the imaging device cannot be solved by simply adjusting the light amount so that the exposure amount of the main subject is appropriate, as in conventional devices.

One way to solve this problem is to expand the dynamic range by performing two exposures, for example. This method uses high-speed shutter operation (for example, l/100
0 seconds). With this method, the exposure time differs by about 16 times, so the dynamic range can also be expanded by about 16 times.

[Problems to be Solved by the Invention] A known example of a method of expanding the dynamic range by multiple exposures is disclosed in Japanese Patent Laid-Open No. 63-3067.
There is a publication No. 79. In this known example, the n-light time is changed for each field, but the exposure timing is poor and shifts by about one field, resulting in a problem that the dynamic resolution deteriorates.

As a known example of eliminating this deterioration of dynamic resolution, there is
There is a publication No.-1.76173.

In this known example, vertical transfer CCDs are installed on both sides of a light receiving element, and charges resulting from two exposures are stored in the respective vertical transfer CCDs. However, since the vertical transfer CCDs are provided on both sides of the light receiving element, the effective aperture area of the light receiving element is small, resulting in low sensitivity. In addition, the frame incline type CCD has a large element area, which poses the problem of high cost for popular cameras.

In view of these problems, it is an object of the present invention to provide an imaging device with a wide substantial dynamic range and good dynamic resolution.

[Means for Solving the Problems] An imaging device of the present invention outputs imaging signals from an imaging element by exposure at different times a plurality of times, and synthesizes the imaging signals to form a composite non-life insurance signal. The image sensor has a light receiving section made up of a plurality of light receiving elements that photoelectrically converts optical information, and a transfer means that transfers a signal from the light receiving section, and the light receiving section performs a first exposure, and the first exposure Immediately after sending the signal from the exposure to the transfer means, a second exposure with a longer exposure time than the first exposure is started, and after the signal from the first exposure is output from the image sensor, the signal from the second exposure is transmitted. is transmitted to the transfer means, and a signal resulting from the second exposure is output from the image sensor.

Further, the imaging device of the present invention is an imaging device that outputs imaging signals from an imaging element by exposure at different times and synthesizes the imaging signals to form a composite imaging signal, the imaging device comprising: controlling the exposure time of the imaging element. A first exposure time is controlled by driving the image sensor, and a second exposure time is controlled by the shutter.

[Function] The imaging device of the present invention immediately starts the second exposure, which has a longer exposure time than the first exposure, after sending the signal from the first exposure point from the light receiving section to the transfer means. (exposure is performed almost continuously), after outputting the signal from the first exposure point from the image sensor, the second exposure is terminated, so that the signal from the first exposure point is output from the image sensor during the period , performs a second exposure of the light receiving section to reduce the deviation in imaging time due to multiple exposures.

Note that the conventional imaging device described above terminates exposure by sending an exposure signal from the light receiving section to the transfer means.
The second exposure cannot be completed until all the signals from the first exposure have been transferred from the transfer means.

In the present invention, the first exposure time is controlled by the operation of sending an exposure signal from the light receiving section to the transfer means (control by driving the image sensor), and the second exposure time is controlled by a shutter that controls the exposure time of the image sensor. This makes it possible to control the second exposure time independently of the transfer operation of the first exposure signal.

Note that the operation of controlling the first exposure time by driving the image sensor is called a CCD shutter when a CCD is used as the transfer means.

[Example] Hereinafter, an example of the present invention will be described in detail using the drawings.

There are many types of image pickup devices used in the present invention. For example, see Technical Report of the Television Society Vol.
．． No. 12 (Feb, 198g) has "IT-CCD image sensor with variable speed electronic shutter". In this paper, the electronic shutter methods for IL-CCDs (interline type CCDs) are as follows: ■ Method of discharging charges to the N-type substrate ■ Method of discharging charges to the shutter drain through a vertical register (vertical transfer CCD) ■ Method of discharging charges to the shutter drain in IL-CCDs Furthermore, a method has been reported in which, in a QFIT or FIT type CCD equipped with a time storage memory, the time is discharged to the shutter drain through a vertical register.

An embodiment of the present invention will be explained by taking as an example an image pickup device using an unnecessary charge discharging method according to method (2), which is currently commonly used.

FIG. 1 is a schematic configuration diagram of an image sensor used in the present invention.

FIG. 2 is a schematic cross-sectional view of the image sensor.

In the first mother, 30a is an image area, and this image area 30a includes a photodiode 30c serving as a light receiving section, and a space for temporarily holding charges photoelectrically converted by the photodiode 30c after the photoelectric conversion is completed. Vertical transfer CCDs 30b are arranged in a plurality of columns. The vertical transfer CCD 30b is shielded from light, and the photocharge held there is the φth vertical transfer pulse. 1, the data is transferred to the horizontal transfer CCD 30d during the horizontal blanking period for every -horizontal scan. Vertical transfer CCD 30b and horizontal transfer CCD 30d
constitutes a transfer means.

Note that the image sensor to which the present invention is applied is not limited to the configuration of the image sensor of this embodiment (for example, vertical transfer C
The present invention can also be applied to an image sensor in which a charge storage section is provided between the CD 30b and the horizontal transfer CCD 30d.

The charges on the horizontal transfer CCD 30d are horizontal transfer pulses φ, l.
The signal is transferred to the output amplifier 30e, subjected to charge-voltage conversion, and output to the outside.

The unnecessary charge accumulated in the photodiode 30c is transferred to the CCD
By applying a shutter pulse φ3N to the substrate (n-type semiconductor substrate 1 in FIG. 2), it is ejected to the CCD substrate.

The cross section of such an image sensor is constructed as shown in FIG.
There is a first well 2 of the type, in which an n-type semiconductor region 3 is formed to constitute a photodiode 30c, and a p-type first well 2 is formed.
A second well 4 and an n-type semiconductor region 5 are formed to constitute a vertical transfer CCD 30b. n-type semiconductor region 3 and n
A polycrystalline region 6 serving as a transfer gate is provided on the p-type first well 2 between the p-type semiconductor region 5 and the n-type semiconductor region 5.
A β film 7 for shielding light is provided thereon. A channel stop is formed by the n-type semiconductor region 8 between the sensors (photodiode 30c+vertical transfer CCD 30b).

Note that the n-type semiconductor region 3. The n-type semiconductor region 5 serves as the drain and source regions of the h-channel insulated gate transistor, and when a positive voltage (φ1lnl) is applied to the polycrystalline region 6, which becomes the gate, the charges accumulated in the n-type semiconductor region 3 It is transferred to the type semiconductor region 5. Also, polycrystalline region 6
When a negative voltage (φ port.I) is applied to the vertical transfer CCD 30
Transfer operation b is performed.

Charge discharge path ■ and charge transfer path ■, ■.

(2) is shown in Figures 1 and 2.

In FIGS. 1 and 2, (2) indicates a discharge pressure path for unnecessary charges from the photodiode 30c, and (2) indicates a vertical transfer CCD 30b from the photodiode 30c.
(2) is a signal charge transfer path from the vertical transfer CCD 30b to the horizontal transfer CCD 30d; (2) is a signal charge transfer path within the horizontal transfer CCD 30d.

The operation of the image sensor according to the present invention will be described below.

FIG. 3 is a timing chart illustrating the operation of the image sensor according to the present invention.

As shown in FIG. 3, the operation of the image sensor of this embodiment includes: ■ first exposure (T, period), which is a short exposure; ■ second exposure (T, period), which is a long exposure. , (1) Transfer of the first exposure signal (Ts, 'period), (2) Transfer of the second exposure signal (7,2' period).

The present invention deals with short exposure (T34 period) and long exposure (T34 period).
It is characterized by the fact that the periods (T, □ period) are carried out almost continuously.

■ First exposure of short-time exposure (T51 period) As shown in Fig. 3, by applying a shutter pulse φ9□ (■ in Fig. 3) to the CCD substrate (n-type semiconductor substrate 1), the photodiode is Unnecessary charges on 30c are discharged and photoelectric conversion is started.

Next, by the pulse φ1 (.) (■ in FIG. 3), the photocharge on the photodiode 30c is transferred to the vertical transfer CCD 30b, and the first exposure is completed (CCD shutter).

(2) Second exposure (T, period) of long-time exposure When the first exposure is finished, the photodiode 30c continues to start long-time exposure (second exposure). This second exposure can be ended after all the photocharges from the first exposure of the vertical transfer CCD 30b are output (after periods "r, ,").

(2) Transfer of first exposure signal (Ts, 'period) Photocharges caused by the first exposure, ie, signal charges, are output to the outside during the second exposure period. The signal charge of the vertical transfer CCD 30b is pulse φ1
(.1 (◎ in Figure 3), the signal is transferred to the horizontal transfer CCD 30d every horizontal blanking period, and during the horizontal effective period, the pulse φ□, ., (■ in Figure 3) causes the output amplifier 30
It is output to the outside via e.

■ Transfer of second exposure signal (period T, A2') When the transfer of the first exposure signal is completed, pulse φ1. . , (■ in Figure 3
′), the photocharges caused by the second exposure are transferred from the photodiode 30c to the vertical transfer CCD 30b, and the second exposure is completed.

When the second exposure is completed, the photocharges due to the second exposure are transferred to the pulse φl1nl (◎' in Figure 3) and the pulse φ□(.1 (■' in Figure 3), in the same way as the transfer of the first exposure signal. is output to the outside.

The above is the basic operation of two exposures and signal transfer. As described above, according to the present invention, it is possible to minimize the time lag between short-time exposure and long-time exposure using a general-purpose, low-cost COD. By combining the signals from these two exposures, the dynamic range can be greatly expanded (detailed explanation will be given later using Figure 5).
.

FIG. 4 is a timing chart explaining the operation of another embodiment of the present invention.

This embodiment differs from the embodiment shown in FIG. 3 in that the end of the second exposure is controlled by another shutter.

The other shacks (shutters in the figure) are normally in an open state, and in this state the first exposure is controlled by the CCD shutter mentioned above and ends. In the embodiment shown in FIG. 3, the second exposure period (T32 period) is completed by adding pulses φ, (.l (■' in FIG. 3) after the transfer of the first exposure signal. The second exposure time will be a value that exceeds the transfer time of the first exposure signal.

In this embodiment, since the second exposure time is controlled using another shack, the second exposure time can be made shorter than the transfer time of the first exposure signal.

The embodiment shown in FIGS. 3 and 4 can be applied to a movie video camera or a still video camera.

In the embodiment shown in FIG. 3, for example, the first exposure period (T,
, ) with a high-speed CCD shutter, and the second n-light interval (T
, 2) can be set to be the same as the one-field period of television, it is possible to obtain a high-speed shutter signal and one-field accumulation signal for each field, making it compatible with movie video cameras. If you use , it will be compatible with still video cameras.

In the embodiment shown in FIG. 4, if the other shutter described above is a low-resolution shutter, it can be used for a movie video camera, and if the other shutter mentioned above is a low-resolution shutter or a focal-brain shutter, it can be used for a still video camera. It will be supported. In the embodiment shown in FIG. 4, short-time exposure may be performed after long-time exposure.

Note that since a mechanical shutter has lower accuracy than a CCD shutter, proper exposure can be obtained by using a CCD shutter that provides long exposure, which is important for image quality.

FIG. 5 is a block diagram of the overall configuration of the imaging device.

In the figure, 10 is a lens, and 20 is an iris or shutter. 30 is a sensor using the image sensor shown in FIG. The subject image is the lens]0. iris 20
The image is then imaged onto the sensor 30. The sensor 30 is controlled by a sensor drive circuit 40 controlled by pulses from a control circuit 70.
Driven by pulses from Iris 20 is sensor 30
The signal output from the camera signal processing circuit 60 passes through the control circuit 70 and is controlled by the drive circuit 50 to have an appropriate signal level. Note that in the case of a still camera, the shutter 20 is controlled to be in the open state when the second exposure is completed, as described above.

The camera signal processing circuit 60 is a -M type video signal processing circuit, and performs knee processing, gamma processing, etc. The signal from the camera signal processing circuit 60 is sent to the A/D converter 8
Analog-to-digital conversion is performed at 0. In this embodiment, first, the first exposure signal is digitally converted and recorded in the memory 90.

In the arithmetic circuit 100, in order to expand the dynamic range,
Image signal synthesis of the first exposure signal from the memory 90 and the second exposure signal from the A/D converter 80 is performed. A control signal for this image signal synthesis is output from the control circuit 70,
The saturated state of the resensor 30 is detected from the long exposure signal (in the case of the embodiment shown in FIG. 3, the second exposure signal), and the saturated pixel signal is replaced with the short exposure signal of one pixel.

The video signal synthesized by the arithmetic circuit 100 is subjected to digital-to-analog conversion by the D/A converter 110 at the next stage, and then guided to the recording system.

[Effects of the Invention] As explained above, according to the present invention, the C of the image sensor itself
The first exposure is a short exposure using a CD shutter, and the second exposure is long while the first exposure signal is being output. Signal charges can be read out sequentially. Therefore, it is possible to minimize the difference in imaging time between two exposures, and to minimize the deterioration of image quality even when shooting a moving image.

Further, according to the present invention, since the second exposure can be controlled by another mechanical or electrical shutter, the second exposure time can be freely set. Therefore, it has the effect of expanding the dynamic range and photographing objects moving at high speed.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an image sensor used in the present invention. FIG. 2 is a schematic cross-sectional view of the image sensor. FIG. 3 is a timing chart illustrating the operation of the image sensor according to the present invention. FIG. 4 is a timing chart explaining the operation of another embodiment of the present invention. FIG. 5 is a block diagram of the overall configuration of the imaging device. 30a: Image area, 30b: Vertical transfer CCD, 3
0c: Photodiode, 30d: Horizontal transfer CCD,
30e output amplifier. Agent Patent Attorney Johei Yamashita

Claims (1)

[Claims] (1) In an imaging device that outputs imaging signals resulting from multiple exposures at different times from an imaging device and synthesizes the imaging signals to form a composite imaging signal, the imaging device includes a plurality of channels that photoelectrically convert optical information. It has a light-receiving section consisting of a light-receiving element and a transfer means for transferring a signal from the light-receiving section, and immediately after performing a first exposure with the light-receiving section and sending a signal resulting from the first exposure to the transfer means. After starting a second exposure with a longer exposure time than the first exposure and outputting the signal from the first exposure from the image sensor, the signal from the second exposure is sent to the transfer means, and the signal from the second exposure is output from the image sensor. An imaging device characterized in that the imaging device outputs from the imaging element. (
2) An imaging device that outputs imaging signals from an imaging element resulting from multiple exposures at different times, and synthesizes the imaging signals to form a composite imaging signal, comprising a shutter that controls the exposure time of the imaging element; An imaging device characterized in that a first exposure time is controlled by driving the image sensor, and a second exposure time is controlled by the shutter.