JPS60134568A - Solid-state image pickup device for still picture - Google Patents

Abstract

PURPOSE:To obtain instantaneously an accurate picture information signal at the start of image pickup by inputting an output of a DC regenerating circuit for correction signal generation and an output of a DC regenerating circuit of an actual picture information signal to a differential amplifier to correct a DC regenerating error thereby reducing the power consumption. CONSTITUTION:A color CCD11 is driven 12 and a picture information signal of an object subjected to photoelectric conversion and fequency multiplex is outputted. A clock component is eliminated from the picture information signal by an LPF 13, the impedance is converted into a sufficiently low impedance by an emitter follower circuit 14 and fed to a clamp circuit 15. Then the signal is subjected to DC regeneration by a clamp pulse from a clamp pulse generating circuit 16 at the circuit 15 and the result is fed to one input terminal of a differential amplifier 17. On the other hand, a signal correcting the DC regeneration error is obtained through the constitution of the emitter follower circuit 18 and the clamp circuit 19 and applied to the other input terminal of the amplifier 17. Then the DC regeneration error is eliminated from the amplifier 17 and a signal amplified into a prescribed level is extracted and processed 20.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an electronic still image imaging device using a solid-state imaging device such as a CCD, and in particular to an electronic still image imaging device that supplies power to the solid-state imaging device only during imaging operation. The present invention relates to a still image solid-state imaging device that can instantaneously and reliably perform direct current reproduction of an image signal, even when the image signal is not in use, thereby obtaining a clear color image with good color balance.

[Technical background of the invention and its problems]

2. Description of the Related Art Recently, there has been active development of electronic still image capturing devices (hereinafter referred to as electronic cameras) that use magnetic sheets or the like as recording media. As the image sensor of this electronic camera, a solid-state image sensor such as a COD is used because it is easy to achieve small size, light weight, and low power consumption.

Unlike general video cameras, electronic cameras do not record continuous image signals, but only one field or one frame image signal on a recording medium such as a magnetic sheet.0And when played back, the recorded image is This system reproduces a single image on a television receiver by repeatedly reproducing the signal. In addition, electronic cameras must have a built-in battery, and small i-
Considering quantification, it is important to further increase i-cost electricity.

Electronic devices that use solid-state imaging devices such as COD have the characteristic of being able to take images instantly after turning on the power, and by taking advantage of these characteristics, the camera section is operated only during the imaging operation. , attempts have been made to prevent battery consumption. However, the electronic circuits of the preamplifier and signal processing section require about 100 milliseconds from power-on to reach a steady state, and there is a problem that they cannot follow the response of the imaging section. Conventionally, even when no imaging operation is required, the power is turned on in advance like a general video camera, and an analog gate circuit is used to extract the signal of one field or frame. A method of recording on a magnetic sheet or the like is used.

By the way, the power 2 using recent solid-state imaging devices such as COD
-Video cameras with power consumption of around 2W have even been developed.

The breakdown is 1.5 W for the CCD imaging section and 0.5 W for the signal processing section (color separation, process circuit, color encoder, etc.).
It is 5W. From this, it is clear that it is possible to significantly reduce power consumption by simply stopping the operation of the CCD imaging section.0 However, when this method is used, the DC regeneration in the signal processing section is sufficient for several tens of milliseconds. (There is a drawback that the upper part of the reproduced image (= color unrelated to the subject) is blurred and the image quality deteriorates significantly.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and aims to reduce power consumption by actively utilizing the feature of solid-state image sensors that it is possible to capture an image instantly after power is turned on. An object of the present invention is to provide a still image solid-state imaging device that can instantaneously and reliably perform direct current reproduction.

[Summary of the invention]

In the present invention, for example, the output of the DC regeneration means for generating correction signals by the emitter follower circuit 18 and the clamp circuit 19 and the output of the DC regeneration means for the actual image information signal are both input to the differential amplifier 17. Solid-state image sensor 1
Even if the power is turned on only when necessary, DC reproduction errors can be corrected, power consumption can be reduced, and an accurate image information signal can be obtained at the instant when imaging is started.

[Embodiments of the invention]

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

FIG. 1 is a schematic configuration diagram of an electronic camera according to the present invention.
FIG. 2 is a diagram of signal waveforms at various parts of the device shown in FIG. 1. In FIG. 1, an optical image of a subject is formed on the surface of a color solid-state image sensor 11 (hereinafter referred to as a CCD) through an imaging lens (not shown). Color CCD II is a two-dimensional image sensor that is integrated with a color mosaic filter with a color arrangement that can obtain frequency multiplexed signals, for example.
It is. This color arrangement and integration technique is a well-known arrangement and technique, so a detailed explanation will be omitted. Color 〇〇D11 is driven by a drive circuit 12 by a well-known means,
A frequency-multiplexed color information signal (image information signal) of the subject image subjected to charging conversion is output. The color 〇〇D11 and the drive circuit 12 are instantaneously supplied with power only when it is desired to take an image (switches and power supplies are not shown on the side), and the other circuits are constantly supplied with power.

The image information signal is input to a low-pass filter 13 to remove the clock component, and is input to an emitter follower circuit 14, where it is converted to a sufficiently low impedance and output. This output is input to the 2-wavelength circuit 15 and is regenerated using the clamp pulse b generated by the clamp pulse generation circuit 16. This DC regenerated signal a is ζ
It is applied to one input terminal of the differential amplifier 17.

On the other hand, a signal C for correcting the DC reproduction error is obtained by the configuration of the emitter follower circuit 18 and the clamp circuit 19, and is applied to the other input terminal of the differential amplifier 17.

As a result, the output d of the differential amplifier 17 has DC reproduction errors removed, is amplified to a predetermined level, is applied to the signal processing circuit 2O, and is separated into a luminance signal and R-Y, B-Y color difference signals. The signal is then FM modulated and recorded on a magnetic sheet or the like as image information. Since known means are used for color separation, FM modulation, etc., detailed explanations will be omitted. Signals a to d in FIG. 2 correspond to the symbols of each part in FIG. 1, and the ON period (ON) in FIG. and 1V is 1
means vertical period. Furthermore, in Figure 1, 21
is a synchronization signal generation circuit, which sets the time axis of system operation, provides a clock to the drive circuit 12, and provides a timing signal to the clamp circuit 16. Is there a diagram that shows a part of the time axis enlarged? IfJ4 diagram is a diagram showing details of the circuit of FIG. 1.

As explained with reference to FIG. 4, the main power source 41 is, for example, a dry battery having an electromotive voltage of 6V. Main power supply switch SW
J is normally in an off state and is in an on state only when performing an imaging operation, and supplies power to the color CCD II and drive circuit 12. When power is supplied to the color CCD 11 and the drive circuit 12, the color CC
Photoelectric conversion and readout operations are performed at DII, and an image information signal is output. Signal changeover switch S'W
2 is normally set to the terminal input side (power supply E side), and is switched to the terminal B side when this is turned on in conjunction with the main power supply switch SWl. At this time, the image information signal is applied to the base of the transistor Q1 constituting the emitter follower circuit 14, and is output from its emitter with sufficiently low impedance. This output is 0.
A 0 ring pulse b is intermittently supplied to the input terminal 42 in response to the readout operation of the color CCDJ 1, and is applied to the base of the transistor Q3 constituting the differential amplifier 17 via a 1 μF coupling capacitor C1. is added to the base of switching transistor Q2.

The collector of this clamp switching transistor Q2 is connected to the base of the transistor Q3, the emitter is connected to the power source E3, and the base is connected to the input terminal 42 via a capacitor C3. A bias resistor R1 is connected between the base and emitter.

When switching transistor Q2 for switching is turned on, the pace potential of transistor Q3 is doubled by the potential of power supply E. However, even if an attempt is made to rapidly raise the potential from zero to the potential of the power supply E, it is limited by the performance of the DC regeneration circuit (clamp circuit 15), and as shown in the waveform shown in FIG. A DC reproduction error occurs over the scanning period (3H).

Next, the DC reproduction error correction means will be explained. This means is composed of transistors Q6, QB, and Q9 having the same configuration and performance as the DC reproduction means composed of two transistors Q, Q, Q, and Qs. This is achieved by DC regeneration means.

The transistor Q9 constitutes an emitter follower circuit 18, and its base is connected to the power supply E and the previous terminal. The low impedance output of this transistor Q9 is inputted to the base of a transistor Q6 constituting a differential amplifier via a 0.1 μF coupling capacitor fC2.

Furthermore, between the base of the transistor Q6 and the power supply 83, the collector-emitter path of a clamping switching transistor Q8 is connected symmetrically to the transistor Q2, forming a clamp circuit 19. C4 is a capacitor, and R2 is a resistor. When the transistor Q8 is turned on by a 2-amp pulse applied to the 0 terminal 42, the base potential of the transistor Q6 is clamped to the potential of the power source E3. However, in this clamping operation, as with the previous DC regeneration means, a DC regeneration error occurs over approximately three horizontal scanning periods, as shown in the waveform shown in FIG. 3(c). , Qs side started under exactly the same conditions, so the DC potential will follow a similar transition period.

Here again, the potential of the power supply E applied to the base of the transistor Q9 is applied at a potential corresponding to the optical black level of the image information signal, which is added to the pace of the second transistor Q1. &-1, a-2 shown in figure (a),
DC level of a-3 and a-4 and c- shown in the same figure (c)
The DC levels of 1, c-2°c-J and c-4 become completely equal, and the DC reproduction error is corrected at the collector of the transistor Q5 constituting the differential amplifier 17. Therefore, as shown in FIG. 3(d), the signal led out to the output terminal 43 via the second transistor Q7 is output as a stable signal without distortion at the same time as the power switch 8W1 is turned on.

Note that R3-R6 are load resistors, and 43 is a constant current source.

In the above description, a case has been described in which a clamp circuit is used as the DC regeneration circuit, but the same effects as in the above embodiment can be obtained by using a sample hold circuit and a sample pulse generation circuit. In addition, although the solid-state imaging device has been described using a COD, it is a MOS.

It can also be realized using other imaging devices such as CID.

〔Effect of the invention〕

As described above, according to the present invention, even when an image information signal is obtained only during an imaging operation, a signal similar to that obtained by direct current reproduction can be obtained instantaneously and reliably.

Therefore, the occurrence of magenta or green edges at the top of the reproduced screen can be avoided, and an extremely natural color reproduced image can be obtained. However, according to the present invention, when performing an image capturing operation, it is possible to record extremely natural color images by simply supplying power to the image sensor and the drive circuit momentarily, so the power consumption of the electronic camera can be reduced. It can be significantly reduced, and the battery can also be significantly downsized. As a result, there is an advantage that it can greatly contribute to reducing the size and weight of the entire electronic camera.

[Brief explanation of drawings]

Fig. 1 is a configuration explanatory diagram showing one embodiment of the present invention, Fig. 2 is a signal waveform diagram of each part of the circuit of Fig. 1, Fig. 3 is a partial spherical diagram of the waveforms of Fig. 2, and Fig. 4 1 is a circuit diagram showing a part of the circuit in FIG. 1 in more detail. 0 11...Color solid-state image sensor, 12... Drive circuit,
13...Low-pass filter, 14.18...Emitter follower circuit, 15.19...Clamp circuit, 16...
・Clamp pulse generation circuit, 17... Differential amplifier, 2
O...Signal processing circuit, 41...Main power supply, 8W1゜8
W2...Switch 0 Applicant's agent Takehiko Suzue Figure 1 Figure 2 (b) ON+OFF+0N-1 Figure 3

Claims (1)

[Claims] A solid-state image sensor to which power is supplied only during imaging operation, means for DC reproducing the image information signal output from the solid-state image sensor, and correction signal generation for correcting DC reproduction errors occurring in the DC reproducing means. DC regeneration means for
means for intermittently generating clamp pulses in synchronization with the image information signal to perform the DC reproduction; and receiving and amplifying the DC reproduced image information signal at one input and the correction signal at the other input. What is claimed is: 1. A still image solid-state imaging device comprising differential amplification means.