JP2558436Y2 - Television camera equipment - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television camera apparatus using a FIT (frame interline transfer) or FT (frame transfer) type CCD image pickup device.

[0002]

2. Description of the Related Art A FIT-CCD image pickup device is provided with a memory section inside a CCD in order to improve vertical smear which has been a problem in an IT (interline transfer) -CCD image pickup device. By transferring charges to the memory unit at high speed during the vertical blanking period, V ·
The effect of unnecessary charges accumulated in the CCD (vertical CCD) is eliminated, and vertical smear is reduced. However, this high-speed transfer pulse is output together with the video signal, and its level reaches several times that of the video signal. Therefore, for example, a correlated double sampling circuit (CD) for processing the CCD output signal
S circuit). That is, the sampling operation is incomplete or the accuracy thereof is insufficient, and shading appears on the screen. The transfer pulse also has a temperature dependency, and increases as the temperature rises. For this reason, shading changes due to temperature appear, and the performance of the television camera is significantly deteriorated.

FIG. 3 shows a system diagram of a conventional system. This method is the correlated double sampling method itself.
The operation of this method will be described with reference to FIG. FIG. 4 shows a schematic diagram of the FIT-CCD. As you can see from the figure,
The FIT-CCD includes an imaging unit and a memory unit, and a signal from the imaging unit is generated by a high-speed transfer pulse inserted during a vertical blanking period shown in FIG.
The vertical smear is improved by high-speed transfer to the memory unit.

The operation is as follows. First, about 90
With a sweep pulse having a frequency of 0 KHz, the dark current charge generated in the vertical CCD and the remaining smear charge are swept to the drain to refresh the vertical CCD. Thereafter, the signal charge from the PD (photodiode) is read by the read pulse. The read signal charges are transferred to the memory unit at a high speed by a transfer pulse having the same frequency (about 900 KHz) as the sweep pulse. As a result, the influence of smear charge leaking into the vertical CCD can be eliminated, and the vertical smear can be improved. The improvement is proportional to the frequency of the high-speed transfer pulse.
In the case of 900 KHz, it is improved by about 35 dB.

However, this transfer pulse is output as a part of the CCD image output signal as shown in FIG. Originally, this transfer pulse only serves to transfer signal charges to the memory unit, and is a signal that becomes unnecessary thereafter. Therefore, the CCD should be processed by the CCD itself.
D is output as a part of the video output signal. This signal is guided to a correlated double sampling circuit (hereinafter referred to as CDS) which is a signal processing circuit shown in FIG.
By performing sample and hold, 1 / f and reset noise generated inside the CCD are removed.

However, as shown in FIG. 5C, the pulse signal for clamping and sampling and holding is a pulse that is continuously connected in both the horizontal and vertical periods (4).
(For a 100,000 pixel CCD, about 14 MHz) Therefore, the sweeping and transfer pulses are similarly clamped, sampled and held. However, as shown in FIG. 6, the clamp pulse (DS1) and the sample hold pulse (DS2) are formed in accordance with the field-through period of the video signal and the signal period, and are thus swept out.
It is not suitable for transfer pulse clamp and sample hold operations.

Furthermore, these unnecessary pulses are large signals reaching several times the level of the video signal, and also have a temperature dependency, and the level increases as the temperature rises. For this reason, the clamp and sample hold operations are incomplete, and as shown in (e) and (f) of FIG. Further, there is a disadvantage that this changes depending on the temperature.

[0008]

SUMMARY OF THE INVENTION The present invention eliminates these drawbacks and removes unnecessary sweeping and transfer pulses from the CCD output signal before inputting the signal to the CDS circuit. Is optimized over the entire period.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a television camera using a FIT (frame, interline transfer) type CCD image pickup device together with signals from the FIT type CCD image pickup device. Unnecessary pulse extracting means for removing unnecessary pulses such as transfer pulses within a vertical blanking period to be output in a stage preceding a signal processing circuit such as a correlated double sampling circuit (CDS circuit) for processing a CCD output signal is provided. The configuration is such that an adverse effect generated by the transfer pulse or the like is not transmitted to a subsequent signal processing circuit.

[0010]

By inserting this sampling circuit, unnecessary pulses during the vertical blanking period can be removed, the operation of the CDS circuit can be made normal, and the vertical video signal jumps at the camera output ( shading)
Can be eliminated.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described in more detail with reference to FIGS. The parts related to the present invention are 12-15
Reference numeral 12 denotes a buffer, and 13, 14, and 15 denote a switch unit, a power supply, and a sampling pulse which constitute an unnecessary pulse sampling circuit. Here, the CC shown in FIG.
When the D output signal is input to the buffer 12, this output is input to the switch 13 of the sampling circuit. The switch unit 13 is configured by, for example, a multiplexer or the like.
The other input of the switch unit 13 is connected to a power source 14
Is connected to the potential indicated by V _C. This potential V _C is selected so as to be equal to the DC potential of the CCD output signal input to the switch unit 13. To the control terminal of the switch unit 13 (multiplexer), a sampling pulse for extracting unnecessary pulses (sweeping pulse and transfer pulse) shown in FIG. 2C is applied. As a result, the output 1 of the switch unit 13
In FIG. 6, a signal from which the sweeping-out and transfer pulses have been removed can be obtained as shown in FIG. As a result, the CDS circuit composed of 1 to 11 is brought into an optimal operation state, and a normal signal without a jump or the like can be obtained as shown in FIG.

[0012]

As described above, by implementing the present invention, the operation of the CDS circuit can be made normal, and even if a FIT-CCD is used, the same S / N improvement effect as that of the IT-CCD can be obtained. And the effect is great. Also, the 1 / f noise generated by the sampling circuit is naturally improved by the CDS circuit.

[Brief description of the drawings]

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

FIG. 2 is a waveform chart for explaining the operation of the present invention.

FIG. 3 is a block diagram of a conventional example.

FIG. 4 is a schematic view showing the structure of an FIT-CCD.

FIG. 5 is a waveform diagram illustrating a conventional operation.

FIG. 6 is a waveform diagram illustrating a conventional operation.

[Explanation of symbols]

 2, 3, 8, 10 Clamp circuit 5, 6, 9, 11 Sample hold circuit 12 Buffer 13, 14, 15 Extraction circuit

Claims (1)

(57) [Scope of request for utility model registration] 1. A television camera using an FIT (frame interline transfer) type CCD image sensor, unnecessary pulses such as transfer pulses in a vertical blanking period output together with a signal from the FIT type CCD image sensor. Means for extracting unnecessary pulses to be removed before a signal processing circuit such as a correlated double sampling circuit for processing a CCD output signal so as to prevent the adverse effects caused by the transfer pulse or the like from being transmitted to subsequent signal processing circuits. A television camera device, comprising: