JPH01264481A - Video camera - Google Patents

Abstract

PURPOSE:To improve efficiency in transferring a carrier by providing a photoelectric converting part for a charge coupled device(CCD) and changing the depth of the potential well of a CCD transfer part according to the quantity of the carrier to be generated. CONSTITUTION:An optical image image-formed from an image pickup lens 11 onto the CCD12 is converted into the carrier at the photoelectric converting part. This carrier is transferred to a transfer part in the CCD 12, and after that, the carrier is outputted as an electric signal and supplied through a preamplifier 13 and a signal processing circuit 14 to a signal level detecting circuit 15 as a video signal. Here, since the output level of the amplifier 13 is proportional to the yield of the carrier, the circuit 15 becomes a carrier detecting means. This detected signal level is supplied to a CCD driving circuit 16. The circuit 16 controls the potential difference between adjoining electrodes in the transfer part of the CCD12 and changes the depth of the potential well of the transfer part according to which is larger, either the detected signal level or a prescribed level. Thus, the video signal having a sufficient level can be obtained, the sensitivity of a video can be enhanced, and the efficiency in transferring the carrier can be improved even when the quantity of the carrier is small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a video camera using a charge-coupled device (hereinafter referred to as COD) as a solid-state wi image element.

(Prior Art) Generally, in video cameras, a COD is often used as a solid-state image sensor.

As shown in FIG. 3, the CCO has a large number of electrodes an on the semiconductor substrate 21 via an insulator 1122.

The configuration is such that bn and Cn (n is a positive integer) are arranged. And these electrodes an, bn.

A predetermined voltage is applied to Cn, and the applied voltage moves a potential well consisting of a depletion layer 23 formed under the electrode. As a result, carriers within this potential well move and are transferred.

Generally, when a COD is used as an image sensor for a video camera, carriers generated in the photoelectric conversion section of the COD in proportion to the amount of incident light are transferred to vertical and horizontal transfer sections, and then sequentially transferred to an output circuit. This signal reading section outputs it as a voltage signal.

However, in video cameras using COD, CO
When the amount of light incident on the charging conversion section D is small, fewer carriers are generated in this photoelectric conversion section. As a result, when these carriers are transferred using a potential well, residual transfer tends to occur at each transfer stage, resulting in a decrease in the level of the electrical signal.

(Problems to be Solved by the Invention) As described above, in video cameras using COD, conventionally, when the amount of incident light is small, the amount of carrier generation is small, so the carrier transfer efficiency decreases, and the output electric signal There was a problem that the level of

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a video camera that can prevent carrier transfer efficiency from decreasing and obtain electrical signals of a sufficient level even when the amount of incident light is small.

[Configuration of the Invention (Means for Solving the Problems)] In order to achieve the above object, the present invention provides a method for achieving the above object by reducing the amount of carrier between adjacent electrodes in the transfer section when the amount of carriers generated from the charging conversion section is less than a predetermined amount. The potential difference is made larger than that when the amount of carriers is larger than a predetermined value l.

(Function) According to the above configuration, when the amount of carriers generated is larger than a predetermined amount, the potential well formed under the electrode becomes deeper than when the amount of carriers generated is smaller than the predetermined amount. As a result, the carrier transfer efficiency is increased, and even though the amount of carrier generation is small, a video signal of a sufficient level can be obtained, and the sensitivity of the video camera is increased.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

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

In FIG. 1, the CCD 1 is
The optical image formed on 2 is converted into a carrier by a photoelectric conversion section. After this carrier is transferred to a transfer section inside the CCD 12, it is output as an electrical signal from a signal readout section. After this electrical signal is amplified by the preamplifier 13,
The signal is supplied to the signal processing circuit 14. The signal is then subjected to predetermined signal processing in the signal processing circuit 14 and output as a video signal.

The output of the preamplifier 13 is further supplied to a signal level detection circuit 15, and its signal level is detected. In this case, since the output level of the preamplifier 13 is proportional to the amount of carriers generated in the charging conversion section, detecting the output level of the preamplifier 13 means detecting the amount of carriers generated. This detection output is supplied to the COD drive circuit 16. When the signal level detected by the signal level detection circuit 15 is lower than a predetermined level, the COD drive circuit 16 makes the voltage applied to each electrode of the transfer section of the CCD 12 higher than the voltage applied when the signal level is higher than the predetermined level. This increases the potential difference between adjacent electrodes. This deepens the potential well, making it easier for carriers to move. As a result, the rate at which carriers remain untransferred is reduced, and an electrical signal of sufficient level can be obtained despite the small amount of carriers generated.

Note that 17 is a synchronization signal generation circuit that generates horizontal and vertical synchronization signals. Further, 18 is a power supply circuit.

FIG. 2 is a circuit diagram showing an example of a specific configuration of the signal level detection circuit 15 and the CCD drive circuit 16.

In FIG. 2, the average level of the output of the preamplifier 13 is detected by an integrating circuit 151 using an operational amplifier. This detection output is supplied to comparators 152 and 153, and it is determined whether or not it is larger than a predetermined level.

If the average level is higher than the predetermined level, the switch 161 of the COD drive circuit 16 is turned on. As a result, the voltage Va is supplied to the drive amplifier 163, and the COD
This voltage ya voltage is supplied to the electrode of the transfer section. On the other hand, if the average level is lower than the predetermined level, the switch 162 is turned on and the voltage vb is supplied to the drive amplifier 163. As a result, the voltage vb is supplied to the transfer section iii of the CCD 12.

Here, voltages Va and Vb are set to satisfy the relationship Va<Vb. Therefore, when the average level is lower than the predetermined level, a larger voltage is applied to each electrode than when the average level is lower than the predetermined level, and the transfer efficiency is increased.

The above operation will be explained with reference to FIGS. 3(a) to 3(d). This figure 3 (a) to (d) shows the three-phase drive C
It is a diagram showing the operating principle of OD.

FIGS. 3(a) to 3(d) show electrodes an and bn.

It is shown that by applying a voltage to Cn, the potential well moves and carriers are transferred.

If the average level of the electrical signal is greater than the predetermined level,
A voltage va of +8■ is supplied to the electrodes.

On the other hand, when the average level is smaller than the predetermined level, v
vb greater than a is supplied. As a result, Figure 3 (
As shown in C), the depth of the potential well becomes deeper and the carrier transfer efficiency becomes higher.

As described above, in this embodiment, when the average level of the output of the preamplifier 13 is smaller than a predetermined level, the CCD 12
By applying a higher voltage to the electrodes of the transfer section than when the average level is higher than a predetermined level, the potential difference between adjacent electrodes is increased.

According to such a configuration, the potential well becomes deep and carriers are efficiently transferred, so that even if the number of carriers generated is small, a video signal of a sufficient level can be obtained.

It goes without saying that the detection of carrier generation l in the photoelectric conversion section of the CCD 12 may be performed at a location other than the output stage of the preamplifier 13.

Furthermore, in the previous embodiment, the case where the present invention is applied to a video camera using a three-phase drive COD was explained, but it is of course applicable to a video camera using a two-phase or four-phase CCD. It is.

Various other modifications can be made without departing from the spirit of the invention.

[Effects of the Invention] As described above, the present invention improves the carrier transfer efficiency by changing the depth of the potential well in the COD transfer section according to the amount of carriers generated in the photoelectric conversion section of the COD. This is what I did. As a result, even when there are few carriers, a video signal of sufficient level can be obtained, and the sensitivity of the video camera can be increased.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention, and FIG.
This figure is a circuit diagram showing an example of a specific configuration of a part of FIG. 1, and FIG. 3 is a diagram showing the operating principle of a three-phase drive COD. 11...Imaging lens, 12...CCD, 13...
Preamplifier, 14... Signal processing circuit, 15... Signal level detection circuit, 16... CCOM operation circuit, 17...
・Synchronization signal generation circuit, 18...power supply circuit, 151...
・Integrator circuit, 152.153... Comparator, 16
1.162...Switch, 163...Drive amplifier. Figure 1

Claims (1)

[Claims] A charge-coupled device having a photoelectric conversion section that generates carriers according to the amount of incident light and a transfer section that transfers the carriers generated in the photoelectric conversion section; a carrier detection means for detecting the amount of carrier; and a carrier detection means for detecting the amount of carrier; when the amount of carrier detected by the carrier detection means is less than a predetermined amount, the potential difference between adjacent electrodes in the transfer section of the charge-coupled device is set to be higher than when the amount of carrier is greater than the predetermined amount; A video camera characterized in that it is equipped with a potential difference control means for increasing the potential difference.