JPS596678A - Video camera - Google Patents

Abstract

PURPOSE:To obtain a clear still picture, by resolving a picture pickup signal photoelectrically converted by a CCD into three primary colors, synthesizing in brightness to obtain the average value, and operating optimum shutter time. CONSTITUTION:Incident light from an object projected through a half mirror forms an image by an image pickup lens 3 on an interline transferring system IL-CCD 305. An image signal of the object photoelectrically converted by the CCD 305 is inputted to a color separation circuit 306 as a time series signal and resolved into primary color signals of red, green and blue. These color signals are sent to a color signal processing section 317, and at the same time, converted to brightness signals Yc in a brightness synthesizing circuit 307. The average value is detected 308 and inputted to an operation circuit 309. This circuit 309 receives the average value, calculates optimum shutter time TS and sends the information to a driving circuit 310. Accordingly, optimum shutter time is set automatically, and automatic exposure of aperture-priority is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video camera using a solid-state image pickup device made of a charge-coupled device.

In recent years, video cameras and piteo table recorders (hereinafter referred to as VT)
The use of video systems combining the R (referred to as "R") has expanded, and VTRs have been equipped with variable-speed picture search mechanisms useful for tape editing and special playback functions such as still image (IJ) + vivid images, and their use is increasing. We are expanding our scope. By the way, it has been pointed out that -1 conventional video cameras have a drawback in that the depth of field cannot be freely adjusted according to the photographer's intention. In other words, most conventional video cameras are equipped with an auto iris aperture, and with these cameras, the auto iris aperture is automatically controlled according to the brightness of the subject, so the depth of field changes accordingly. Therefore, it is completely impossible to adjust the depth of field according to the photographer's intention. Therefore, by making it possible to adjust the sensitivity of the image sensor in addition to the aperture, it is possible to adjust the depth of field within a certain range, such as opening the aperture and shallowing the depth of field when the sensitivity is set to low. However, even in a video camera using such an image sensor, the shutter time is 14
It is fixed at 0 seconds, and even if you take a picture of a fast-moving subject and play it back as a still for 1 field, the screen will still be 1/2 seconds.
There is a problem that

In other words, in conventional video cameras, the photoelectric charge accumulation time (hereinafter referred to as shutter time) of the photoelectric conversion element for imaging is limited to a certain time, such as 1/60 second or 1/80 second, so high-speed If you shoot and record a moving subject and play it back as a still image, the only result you will get is a blurred or blurred playback image. This can be a problem especially when photographing sports and trying to reproduce the so-called decisive moment with a stop motion and use it to correct the form. Attempting to solve this problem by signal processing on the VTR side would require a complicated and expensive circuit, and the VTR
This would go against the trend of miniaturization and simplification of TR.

The present invention was made in view of this situation, and
The purpose is to develop a video camera that is capable of obtaining clear images without blur during still playback, and that allows the depth of field to be arbitrarily adjusted over a wide range as intended by the photographer. It is said that

In other words, in the video camera of the present invention, ′α is used as an image sensor.
Using a charge coupling device (hereinafter referred to as "CCD"), the photocharge accumulation time (shutter time) of the CCD is used as a control means to change the electronic I/C (7). By actively utilizing the electronic shutter function of the CCD itself, it is possible to capture and record high-speed moving objects.
(In addition to obtaining a blur-free image even when the camera is in use, it also allows for fairly free adjustment of the depth of field by adjusting the shutter speed and time.)

In the present invention, when an interline transfer type or frame transfer type overflow drain +J type CCD is used as the CCD, the control means is an electrode that controls the discharge operation of photoelectric charges to the overflow drain, i.e. The control pulse signal applied to the overflow control cable is temporally controlled by, for example, changing its duty ratio.

Further, when using a frame transfer type CCD without an overflow drain as the CCD, the control means:
The vertical transfer pulse signal to the CCD is temporally controlled.

Embodiments of the present invention will be described below with reference to the drawings.

First, the first embodiment uses an interline transfer type CCD (hereinafter referred to as IL-C) equipped with an overflow drain as a CCD.
FIG. 1 shows an example using the above-mentioned IL-
FIG. 2 is a schematic diagram showing the structure of the CCD, FIG. 2 is a timing chart for explaining its operation, and FIG. 5 is a block diagram showing the main structure of the video camera according to this embodiment.

In FIG. 1, (100) is a photoelectric conversion element light-receiving section forming a large number of pixels, (101) is a plurality of vertical transfer registers that vertically transfers the charge of each light-receiving section, and (102) is a light-receiving section that transfers the charge of each light-receiving section. A transfer gate (105) is used to transfer charges to the vertical transfer registers (101), a horizontal transfer register (105) is used to horizontally read charges from each vertical transfer register (101), and (104) is an output amplifier. An overflow control cage (105) and an overflow drain (106) are provided adjacent to the light receiving section (100).
The overflow drain (106) is controlled by the overflow drain (105).
It should not be discharged. This more IL-C
OD itself has been known for a long time, and although the present invention uses this IL-CCD as an image sensor, it is possible to create a video camera with a new function of varying the photocharge accumulation time by appropriately changing its control signal. That's what you're getting. .

@Figure 2 shows the IL-COD in Figure 1.7) Photocharge tata
A timing chart for driving using the variable distance method is shown in 1. 1, in FIG. 2, (VBLK) is a vertical blanking signal, (φt) is a transfer gate pulse, which is a signal for transferring charge from the light receiving part (ioo) to the vertical transfer register (101), (01i
"CG" is the overflow control gate (105
) [The timing for reading out signals from registers (, 101) and (105) is shown by diagonal blocks in the first part.

While the control pulse signal (OFCG) is at a high level, the voltage is high enough to discharge all of the photocharges generated in the light receiving section (100) to the overflow drain (106) (105). Therefore, during this period (η), even if a source is incident on the light receiving section (100), the photocharge generated at the PN junction cannot be accumulated.Also, the signal (OFCG) is at a low peak) level. During this period, the photocharge generated and accumulated in the light receiving section (100) is transferred from the transfer gate (102) to the vertical transfer register (100).
01) before overflowing to the overflow drain (106
) is applied to the gate (105
), therefore, during this period (TB), it is possible to accumulate photocharges in the light receiving section (100), and excess accumulated charges are discharged to the overflow drain (106) to prevent Pyrill blooming. It will be fulfilled.

Now, in Fig. 2, the vertical blanking signal (VBLK
) is at a low level within the vertical blanking period and immediately before its end, a transfer gate pulse is applied, and the photocharges accumulated in the light receiving section (100) up to that time are transferred to the vertical transfer register (101). Ru.

The pulse width of the transfer gate pulse (φt) is determined by the pulse width of the transfer gate pulse (φt) to transfer the photocharge accumulated in the light receiving section (100) to the vertical transfer register (
101) as long as the pulse width is sufficient to transfer the data to 101). At the same time as the transfer of the photocharges to the vertical transfer register (101) is completed, the control pulse (N (OFCG)) is set to a high level to prevent the accumulation of photocharges in the light receiving section (ioo). After the predetermined transfer period (Tl) has elapsed, the control pulse No. 745 (OFCG)' is set to a low level to enable accumulation of photocharge in the light receiving section (100). This state is used for the next transfer. Gate pulse (
The pulse (φt) continues until the pulse (φt) is applied, and the accumulated photocharge is transferred to the vertical transfer register (φt) by the pulse (φt).
101), the control pulse signal (
opcG) is increased to prevent photoelectric charges from accumulating in the light receiving section (100), and then f'L is repeated. The photocharge transferred to the vertical transfer register (101) is a normal I
According to the operation of the L-CCD, the vertical transfer pulse signal (φv1
) (φV□) and horizontal transfer pulse signal (φh1) (φ
h2) By sequentially reading from the horizontal transfer register (105) via the amplifier (104) from K to
G)-d=low level 17) The COD is driven with the period (T, ) as the shutter time. Therefore, the period (T) during which the control pulse signal (OFCG) is kept at a high level is determined by T = TV - Ts from the desired shutter time period (T8) to be adjusted and the field time (TV). Needless to say, this field time (TV) is 1/60 second in a normal video camera. In addition, the time T for which the control pulse signal (OFCG) is kept at a high level is set to zero, that is, the light receiving section (1
00) is kept in the accumulation state, normal accumulation operation occurs and the accumulation time is fixed at 2Tv, that is, '/30 seconds.

IL-CCD with overflow drain like this
The main structure of a video camera according to the present invention, which is constructed using the above-mentioned image capturing element, is as shown in FIG. The example shown in FIG. 6 is shown in FIG. Imaging collection element I consisting of IL-CCD
This video camera F
', it is a color video camera that performs automatic exposure control using a single aperture priority system.

In Figure 5, a half mirror (500) and a roser (6
oi) and the eyepiece (502) constitute an optical viewfinder, and the incident light from the subject that enters through the flare (600) is captured by the imaging lens (506). imaged on top.

(, 504) is an aperture that is arbitrarily set by the photographer. I
L-CCD (505) The imaging signal of the subject image photoelectrically converted by L/R processing is sent as a time series signal to a color separation circuit (,
506) and is decomposed into 6 primary color signals of gait, green (Gl and #(B).These 5 primary color signals (R1(B)
l (Gl is sent to the color signal processing unit (317), while being input to the luminance signal synthesis circuit (507) and converting the luminance (g
The luminance signal (Yc) is input as an average value signal to an arithmetic circuit (309) via an average value detection circuit (', 508). The arithmetic circuit (,509) receives the average value of the luminance signal (Yo), calculates the optimum shutter time (accumulation time) (T,), and calculates the optimum shutter time (accumulation time) (T,).
The information is sent to the drive circuit (510).

As described above, the optimum shutter time (T8) for the set aperture is automatically set, and aperture-priority automatic photography becomes possible. Since the subject brightness is low compared to the manually set aperture value, the shutter time is set to 1/50.
A situation may occur where the amount of exposure is still insufficient even if the exposure amount is in seconds. For this kind of situation, an alarm circuit (3
20), and a warning to the effect that an appropriate exposure amount cannot be obtained for the set aperture value may be provided by display or sound.

Further, an aperture driving means (2121) shown by a dotted line is provided, and the aperture (,504) is driven until an appropriate exposure amount is obtained.
) may be controlled.

In FIG. 6, the color signal processing section (317) (R
1(Gl )(31
3') 14) (R1CGl (Bl signal is synthesized in the matrix circuit (315) and becomes five signals, luminance signal (Y), color difference signal (RY) and (B-Y), and sent to the encoder circuit. (516) and is sent to the encoder circuit (516).
16) is output as a standard television signal such as NTSC.

Note that (311) in FIG.

In the embodiment of FIG. 6, I L -CCD (,50
5) receives white light, the output levels of the (R1(Gl(Bl) signals are not the same, and for example, the (R) signal for white light is Gl (Bl) If the characteristics are such that it saturates before No. 4m, use the average metering method shown in Fig. 4 as the shutter time control circuit instead of the average photometry method shown in Fig. 5. It is preferable to adopt a method of detecting the peak value of a specific color component signal as in the embodiment.

In FIG. 4, the same reference numerals as in FIG.
The color signal that saturates first, in this case (R1 signal), is input to the peak value detection circuit (400), and is input to the arithmetic circuit (,5
09), however, calculates the shutter time according to the peak value of the signal and sends it to the drive circuit (310). In this way, optimal exposure that does not saturate is given to all of the (R1 (B) (G) signals).

The first and second embodiments described above are cases in which a color video camera capable of aperture-priority automatic exposure is configured using an IL-CCD' (c-imaging element) with an overflow drain. Frame transfer method +7) CCD (
Example 1 of using FT-COD and Tm below as an image sensor
(explain about.

Figure 5a is an FT-CCD without overflow drain.
, Figure 5b shows the FT-C with overflow drain.
Each CD is schematically shown. FT-CCD in Figure 5a
is a surface channel FT-CCD.

In these figures, (500) is the light receiving section, (501) U
, storage section, (502) horizontal transfer register, (503)
is a readout amplifier, (504) is an overflow control gate, and (505) is an overflow drain.The structure and function of each have been well described, so they will not be described in detail here.

Fig. 6a shows the driving operation for changing the shutter time (storage time) of the present invention when the FT-CCD without an overflow drain shown in Fig. 5a is operated in a two-phase drive system both horizontally and vertically. It is a timing chart of each part signal. (VBLK) is a vertical blanking signal, (φ8,) (φa2) is a vertical transfer pulse signal applied to the vertical transfer electrode of the light receiving section (500), and the height of this vertical transfer pulse signal (φ81) (φ8□) is The level voltage is the voltage that allows the accumulation of photocharges below the electrode, and the low level voltage is the voltage that makes it impossible to accumulate the photocharges below the electrode. In the case of such an FT-CCD, in the present invention, the shutter time (storage time) is changed by variably controlling the pulse rise time of the vertical transfer MELF No. 11 (φ8□) (911i2). In other words, a normal FT-CCD
In the driving force formula, vertical transfer pulse signal (φa1) (φ1.
) were to rise at the end of each vertical blanking period (Tvbik) in synchronization with the vertical blanking period (Tvbik), but in this invention, they are caused to rise after an arbitrary time delay after that, and by variable control of this time, the light reception The photoelectric charge accumulation time in the section (500), that is, the charger time, is adjusted to a desired value. Therefore, for (φa1), (Ta)
For the period (φ8.)K, photocharge is accumulated only for the period (Tb), and an interlacing operation is achieved.

(φbl) (φbz) are transfer pulses from the storage section (501) to the horizontal transfer register (502), and only one of them (φbl) is shown in FIG. 6a. Chapter 6a
In the figure, the hatched portions (φa1), (φa2), and (φb1) are the transfer period from the light receiving section (500) to the storage section (501) during the vertical blanking period (Tvb i k ), and this is always the vertical blanking period (Tvb i k ). Ranking period (Tvb i
Of course, the force must be t within k). Within the vertical effective period, transfer pulses (φb1) (φb2) are emitted as many times as the number of vertical pixels.
02).

FIG. 6b is a timing chart of various signals of the drive operation that changes the shutter time (accumulation time) of the present invention when the FT-cco with an overflow drain shown in FIG. 5b is used, and the vertical transfer pulse signal ( φaX
) (φ8□) and λ-bar 70-control cable
) (504) control pulse signal (OF C
Other than (j), it is different from Figure 6a.

Vertical transfer pal No. 2421 (φa1) (φ3□) is E6a
As in the case of the figure, the high level is the photocharge storage disabled voltage, and the low level is the photocharge storage disabled voltage, and the high level voltage of the control pulse signal (OFCG) is the photocharge storage state 41 (f!: If the voltage is low enough to discharge the 71° electric charge W'J accumulated under the photoreceptor electrode C to the overflow drain (505), the accumulated electric charge will increase. The overflow drain (1, 11 can be output to 5 (J5) before turning off)'t
It is L pressure. In Fig. 61), during the field period '(TV, ) II (and IIJ signal 3□) is not applied under the electrode, the photo-charge accumulation O1 is enabled, but the number of control pulses → ) (OFCG) during the high level period (Tl)
) (/ζ Do the strawberry dumping to get the electric charge discharged) L No. Next, control valve switch cr-s (0
During the low level period (T, ) of FCG), charges are not discharged to the overflow drain (505) (because this occurs, photocharge accumulation starts only at this point).

In the subsequent field period (TV2) Vr, the signal (
A similar operation is performed under the light-receiving electrode to which φ11) is applied, and by variable control of the fall time of the control signal to the overflow control gate (504'), the results shown in FIGS. 1 and 2 are Driving with variable shutter time (photocharge accumulation time) is achieved in the same manner as in the above example. There is no need to explain in detail that a video camera capable of automatic exposure control using the aperture priority system similar to that shown in FIG. 5 can be constructed using these FT-CCDs.

In addition, in this FT-COD, regardless of whether it is equipped with an overflow drain or not, light reception is falsely performed even during the vertical transfer period (fP+ line part in Fig. 6 arb) due to structural reasons. , the shutter time (T8
) should be noted that A cannot be made extremely short.

In the example described above, an aperture-priority system was used as an example of a video camera configuration, but the present invention can also be applied to automatic exposure control using a shutter speed-priority system, for example by using a lens with an auto-iris mechanism. Figure 7 shows the main configuration of the video camera in this case. The difference in FIG. 7 from those in FIG. 6 or 4 is that the f# element F(I L -CCD (,505) K
Instead, using F T -COD (519), the average value of the luminance signal obtained by the average value detection circuit C508) is
Instead of calculating in step B) to obtain the signal that gives the accumulation time (shutter time) f, obtain an aperture value control signal, and apply this aperture value control signal to the aperture drive unit (700) If (give it to the aperture (304) is automatically adjusted, and the shutter time is manually set in the drive circuit (610).The aperture drive unit (700) has a motor control circuit (701) and an output amplifier (702), similar to a normal auto iris mechanism.
and multiple drive motors (70, 5). If you manually set the camera to shoot with a short shutter time and playback only one field, you can obtain an easy-to-read still image with less blur. Here, since the brightness of the subject is low relative to the manually set shutter time, a situation may occur where the amount of exposure is still insufficient even if the aperture is opened. For this kind of situation, an alarm circuit (520) shown by the 16-dot line may be installed to display or sound a warning that the appropriate exposure amount cannot be obtained for the set shutter time. .

Further, based on the output signal υζ indicating insufficient exposure from the arithmetic circuit (518) indicated by a dotted line, the drive circuit (310) lengthens the shutter time until the appropriate exposure is obtained within 1/60 seconds. You can control it as you like.

In addition, in the embodiments described so far, the aperture priority method using an IL-CCD with an overflow drain (
6 and 4) and the FT-CCD with shutter speed priority system (Fig. 7). Of course, it is also possible to configure a camera using an aperture-priority system using FT-CCDK or an aperture-priority system using an FT-CCDK.In particular, if the camera is limited to an aperture-priority system, an auto-iris drive motor is not required, which is advantageous for making the video camera smaller and lighter. plan

As described above, in the present invention, since the shutter time is variable, it is possible to perform automatic exposure photography using an aperture-priority method at any aperture and therefore any depth of field.

Also, change the shutter time to the field time (1//6o
Since the time can be shortened to any length of time below (seconds), it is possible to obtain a clear still image without blur by playing back only one field when still playing back the recording of the shooting result.

[Brief explanation of the drawing]

i I Figure 〒ζ IL-CO with bar flow drain
2 is a timing chart for explaining its operation, FIG. 6 is a block diagram showing the main structure of the video camera according to the first embodiment of the present invention, and FIG. A block diagram showing the main configuration of the video camera according to the embodiment, FIG. 5a is an FT without an overflow drain.
- Schematic diagram showing the configuration of CCD, Figure 5b is a schematic diagram showing the configuration of FT-COD with overflow drain, Figure 6
Figure a is a timing chart for explaining the operation of the FT-CCD in Figure 5a), Figure 6b is a timing chart for explaining the operation of the FT-CCD in Figure 5b, and Figure 7 is a timing chart for explaining the operation of the FT-CCD in Figure 5b. FIG. 2 is a block diagram showing the main configuration of such a video camera. (1oo'): Light reception 1: +s, (1o1): Vertical transfer register, (102): ) Transfer gate, (103): Horizontal transfer register, (104): Amplifier, (105) Niover flow control gate , (106) Niober flow drain, (5('
15) : Imaging lens, (304) : Aperture, (305
): Imaging II, -C(': D, (306)
: Color separation circuit, (307) : Luminance signal synthesis circuit, (,
508): Average value detection circuit, (,1509)(,”)
18): Arithmetic circuit, (310): Drive circuit, (5
11): Synchronous signal generation circuit, (312X515) (3
14): Process circuit, (315): Color matrix circuit, (316): Encoder circuit, (617)
: Color signal processing unit, (319) : Imaging FT-C
CD. (400): Peak value detection circuit, (500): Light receiving section, (501): Accumulating section, (5112): Horizontal transfer register, (503): Amplifier, (504) Niober flow control gate, ( 5 [15] Niover”70-drain, (700): Aperture drive unit,
(701): Motor control circuit, (702): Output amplifier, (703): Aperture drive motor. Agent, j ``Buried soil Kimura Sanro Naka 50.m Ya 5b figure

Claims (1)

Claims: (1) A video camera using a charge-coupled device as an image sensor, characterized in that the video camera is equipped with a control means for changing the photocharge accumulation time of the device. (2i'N! The charge-coupling device has an overflow drain for discharging the photocharge, and the control means temporally controls the control signal applied to the gate for controlling discharge of the charge to the overflow drain. A video camera according to claim 1, characterized in that the charge-coupled device is of a frame transfer type, and the control means transmits a vertical transfer pulse signal to the device. 2. The video camera according to claim 1, wherein the video camera is configured to temporally control the video camera.