JPS61224670A - Image pickup device - Google Patents

Abstract

PURPOSE:To prevent in advance deterioration in picture quality by detecting a change in a cathode current of an image pickup tube and designing the device that an alarm signal is raised when the detection result reaches a preset level so as to warn the period of replacement of the image pickup tube. CONSTITUTION:When emittion of thermoelectrons of a hater is reduced, the cathode current is decreased to decrease the 2nd grid current 2. A current detection circuit 4 detects the decrease in the 2nd grid current 2 and the output voltage at that time is inputted to a level comparison circuit 5. An output of the level comparison circuit 5 is inputted to a voltage control circuit 7 and the 1st grid voltage 3 is controlled by the output of the level comparison circuit 5. On the other hand, the output voltage of the level comparison circuit 5 is inputted to another level comparison circuit 10, which compares the output voltage of the level comparison circuit 5 with a reference voltage set by a reference voltage generating circuit 11 to output a voltage in response to the decrease in the emission and a drive circuit 12 amplifies the voltage to light a display element 13 such as an LED.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an imaging device capable of providing a life warning device for an imaging tube.

[Prior Art] An example of an imaging device using a conventional image pickup tube and equipped with an image pickup tube life warning device is a video camera for broadcasting or business use that is equipped with an energizing time meter.

However, although the hour meter used here displays the usage time, it does not warn or display the time to replace the image pickup tube, so it has the disadvantage that it cannot respond to fluctuations in the lifespan of the image pickup tube.

Furthermore, although it is possible to use this energization time meter by attaching it to a consumer video camera, it is large and expensive, which increases the cost and increases the size of the camera, making it impractical. Therefore, such time meters were not used at all in video cameras using consumer-grade image pickup tubes.

Another example is one that detects only the presence or absence of the second grid current in the image pickup tube, and if no current is flowing, closes the iris to protect the image pickup tube or issues a warning. . However, with this configuration, the second grid current cannot be detected quantitatively, so there is a drawback that it is not possible to know in advance when it is time to replace the image pickup tube.

By the way, the lifespan of the image pickup tube of a consumer video camera is approximately 50 years.
It is said that it lasts about 0 hours, and it was thought that there would be no problem since it had a relatively long lifespan for home use, and there was no need to replace it every time.

However, in recent years, consumer cameras have spread rapidly and are not only used in a variety of ways, such as for surveillance, but are also used all the time or frequently. As a result, the life of the image pickup tube is coming to an end sooner, and there is a growing desire to know in advance when to replace it.

This is because, in particular, most consumer cameras are single-tube type, which is different from professional multi-tube type cameras, and when the life of the image pickup tube comes to an end, various adverse effects will occur on the circuit configuration. In other words, as the life of the image pickup tube reaches its end, emissions decrease, and not only does the beam become insufficient and the bright areas of the subject become blurred, but also the focus shifts and the resolution decreases.
This is because negative effects such as a decrease in coloration and an increase in color unevenness on the monitor television screen occur, degrading the image quality and making the screen very difficult to see.

[Purpose] The present invention has been made to eliminate such conventional drawbacks, and its purpose is to prevent deterioration of image quality by warning that it is time to replace the image pickup tube, and to prevent deterioration of image quality. To provide a compact and inexpensive imaging device capable of warning the lifespan of an imaging tube.

[Embodiment] FIG. 1 shows a first embodiment of the present invention. In this embodiment, the present invention is applied to a video camera using an emission reduction compensation circuit, and FIG. 1 shows a life warning device for an image pickup tube of the camera.

In the figure, l is the image pickup tube, 2 is the second grid current of the image pickup tube l, 3 is the first grid voltage of the image pickup tube l, 4 is the current detection circuit, 5 is the level comparison circuit (comparator), and 6 is the level comparison circuit. a reference voltage generation circuit for setting the reference voltage of 5;
7 is a voltage control circuit that controls the first grid voltage 3;
is a positive polarity high voltage power supply, 9 is a negative polarity high voltage power supply, 10
12 is a reference voltage generation circuit which inputs the output of the level comparison circuit 5, 12 is a drive circuit for the display element 13, and 13 is a warning means (such as a light emitting diode).

14 is a portion surrounded by a broken line and is an emission reduction compensation circuit.

With this configuration, when the emission of thermoelectrons from the heater decreases, the cathode current decreases, and the second grid current tJL2 also decreases. The current detection circuit 4 detects this decrease in the second grid current 2 and inputs the output voltage at that time to the level comparison circuit 5. The input voltage is compared in this level comparison circuit 5 with a reference voltage set in advance by a reference voltage generation circuit 6. and,
The output of the level comparison circuit 5 is input to the voltage control circuit 7,
The first grid voltage 3 is controlled by the output of this level comparison circuit 5. The controlled first grid voltage 3 increases the second grid current 2 in the developer tube 1, which in turn increases the cathode current. Since the second grid current 2 is feedback-controlled in this way, the cathode current and the second grid current 2 are always constant.

On the other hand, the output voltage of the level comparison circuit 5 is input to another level comparison circuit 10. Then, level comparison circuit 1
0 compares the output voltage of the level comparison circuit 5 with a reference voltage set by the reference voltage generation circuit 11 and outputs a voltage corresponding to a reduction in emissions. The drive circuit 11 increases this voltage to light up the display element 13 such as an LED.

In this way, in the imaging device of this embodiment, even if the emission decreases, the second grid current 2 does not change, but the output of the level comparison circuit 5 changes, so this output is used to determine the lifespan of the developing tube. The display element (LED, etc.) 13 is illuminated with an output corresponding to a reduction in emissions compared with a corresponding reference voltage. Therefore, the user of the video camera can know when to replace the image pickup tube before its life reaches the end, and can prevent deterioration in image quality caused by missing the timing for replacement. .

For example, in a single-tube system for consumer use, when the emission of the image pickup tube decreases, not only does the beam become insufficient and the bright parts of the subject are crushed, but also the focus shifts and the resolution decreases, resulting in a decrease in coloration and color distortion. Although unevenness increases, such a phenomenon can be prevented.

Further, as described above, this life warning device has a relatively simple circuit configuration and is mechanically compact, so it is inexpensive and particularly suitable for civilian video cameras.

FIG. 2 shows a second embodiment, in which the same or equivalent parts as in FIG. 1 are given the same reference numerals. This embodiment is an example in which the present invention is applied to a video camera that does not use a circuit that compensates for low emissions I''.

In FIG. 2, the second grid current 2 is detected by the current detection circuit 4.
The output voltage is then input to the level comparator circuit 5. The level comparison circuit 5 compares this input voltage with a reference voltage set by the reference voltage circuit 6 and outputs a voltage corresponding to a reduction in emissions. The drive circuit 11 amplifies this voltage and lights up the display element (LED etc.) 12.

This embodiment is characterized in that the level of the second grid current is directly detected, but the functions and effects are not essentially different from those of the first embodiment.

Note that the developing tube life warning device according to the present invention is suitable for somewhat high-end consumer, professional, and broadcast cameras.
It may be used in conjunction with a conventional energizing time meter. In this case, for example, if an electronic time meter is used, when a certain energizing time on the footrest is reached, the warning means of the above-mentioned life warning device will be used. Can be configured to issue a warning.

[Effects] As explained above, according to the present invention, a change in the cathode current of the image pickup tube is detected and a warning signal is issued when this reaches a preset level, so that the image pickup tube cannot be replaced. It is possible to obtain an imaging device which can prevent deterioration of image quality by giving a warning about the timing, and which can also give a warning about the end of the life of an image pickup tube, which is small and inexpensive.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main parts of a first embodiment of the invention, and FIG. 2 is a block diagram showing the main parts of an MS2 embodiment of the invention. In the figure, l is an image pickup tube, 2 is a second grid current, 3 is a first grid voltage, 4 is a current detection circuit, 5.10 is a level comparison circuit (comparator), 6.11 is a reference voltage generation circuit,
7 is a voltage control circuit, 11 is a display element drive circuit, and 12 is a display element (LED etc.).

Claims (1)

[Claims] It has a detection means for detecting a change in the current of the image pickup tube, a comparison means for comparing the level of the current detected by the detection means with a reference level, and a warning signal forming means for forming a warning signal based on the output of the comparison means. Imaging device.