JPS58196782A - Photographing device for crt screen - Google Patents

Abstract

PURPOSE:To realize a correct exposure for a film, by detecting the luminance of a back-porch or front-porch signal of a vertical scanning signal to control the open time of a shutter by the output. CONSTITUTION:When a photographing switch S2 is pushed, flip-flop circuit 17 is set, a shutter 4 opens through a driver 18 simultaneously with the starting of a screen, and a film starts to be exposed. A pedestal level, which shows the max. luminance of the screen is measured by detecting the luminance of a back-porch or front-porch signal of a vertical scanning signal with a photoelectric transfer element 7, and, an exposure is found by means of the output of it to reset the flip-flop 17 and to control the open time of the shutter 4 with an actual time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a so-called cathode ray tube screen photographing device for photographing an image of a so-called CRT.

In computer tomography equipment, ultrasonic diagnostic equipment, etc., when displaying the image signal sent from these equipment as television No. 411 on a cathode ray tube and photographing it with photographic film, the nature of the film's density and Gradation becomes extremely important. However, due to changes over time and temperature, the brightness of the CRT screen may vary.
They tend to change, and if you take pictures without taking any precautions, there is a high risk that you will not be able to obtain high-quality images.

In order to compensate for this change, correction methods such as a pre-scan method and a screen average metering method have been conventionally implemented. The former Briscan method is a method in which a white screen is displayed on the cathode ray tube before the shadow, this brightness is measured and memorized, and the fogging time is determined based on this memorized value when the next photograph is taken. The circuit requires a white screen to be displayed, which is cumbersome to operate. In addition, in this case, since measurements are not performed in real time, there is also the drawback that changes in conditions due to voltage fluctuations etc. during imaging cannot be accounted for. Furthermore, the latter screen average metering method measures the brightness of almost the entire CRT screen, but if there are too many or too few white areas on the screen, it may not necessarily produce an image with good contrast. It is known that it cannot be obtained.

An object of the present invention is to provide a CRT screen photographing device that solves the above-mentioned problems and enables accurate fog light control in real time. In order to detect the brightness of signals other than image signals related to screen brightness, a photoelectric conversion element is placed at a predetermined position on the surface of the cathode ray tube, and the exposure amount is determined by receiving the output signal from the photoelectric conversion element and the shutter is The present invention is characterized in that it includes an exposure control circuit that controls the open time in real time.

The present invention will be explained in detail based on illustrated embodiments.

FIG. 1 shows the basic configuration of a general CRT screen photographing device.A mask plate 2 is provided on the front of the CRT 1 to demarcate the effective display range of only the image. The image is photographed and imaged on the film 5 through the camera.

Further, a scanning signal for a vertical period of one field of a general television signal is formed from a front porch signal F, a vertical synchronizing signal S, a back porch signal B, and an image signal (2), as shown in FIG.

When taking a photograph, the cathode ray tube 1 normally displays a negative image so that the photographed photograph and the viewing monitor image are in the same black and white state. The brightness on the surface of the cathode ray tube 1 in response to this television signal is as shown in FIG. 3, which is an inversion of the signal in FIG. 2. The levels of the back porch signal B and the front porch signal F are the same as the highest brightness portion of the image signal I, and are equal to the pedestal level P.
1 In the embodiment of the present invention, as shown in FIG. 4, a small hole 6 is provided in the mask plate 2 on the front surface of the cathode ray tube l, and a photoelectric conversion element 7 is embedded therein. It is attached toward and in contact with the tube surface of No. 1. The mounting position of this photoelectric conversion element 7 is as follows.
This is the scanning start position of the vertical scanning signal, and is positioned so as to face the scanning position of the back porch signal B, which is above the screen.

FIG. 5 is a block and circuit configuration diagram of an exposure control circuit that controls the opening time of the shutter 4. The output of the photoelectric variable sensor f7 is input to the peak hold circuit 11, and the output of this peak hold circuit 11 is The comparison circuit 12 is connected to the comparison circuit 12 of FIG. On the other hand, the first comparison circuit 12 has a first reference voltage E.
! The output from the first integrating circuit 13 which integrates the electric quantity of 1. It is compared with the output from the previous peak hold circuit 1.1, and the output operates switch S1.

The second integrating circuit 14 is configured to manually output the second reference voltage E2. The output of the second integration circuit 14 is input to the second comparison circuit 15, and this comparison 101 path 15
The output voltage of the second comparison circuit 15 is compared with the output voltage from the variable resistor R for setting the sensitivity of the film 5, and the output of the second comparison circuit 15 is inputted to a flip-flop circuit 17 via a differentiating circuit 16. The flip-flop circuit t-7 has a photographing switch S2.
The output of the flip-flop circuit 17 is connected to operate the driver circuit 18 to open and close the shutter 4. Note that this control circuit is designed to operate in l-field units, the peak hold circuit 11 is configured to operate in synchronization with the horizontal scanning signal, and the first integration circuit 13 is configured to operate in synchronization with the vertical scanning signal. When you press the shooting switch S2, the shutter 4 will start from the start of the next screen.
is opened, and the shutter 4 is configured to close at the same time as the end of vertical scanning after the required number of screens has elapsed.

When the photographing switch S2 is pressed for photographing, the flip-flop circuit 17 is set, the shutter 4 is opened via the driver circuit 18 at the start of the screen, and the exposure of the film 5 is started. On the tube surface of a cathode ray tube,
As mentioned above, the brightness of the back porch signal B is the same as the brightest part of the screen, and the brightness of the back porch signal B
When the bright spot passes in front of the photoelectric conversion insert 7, an output proportional to the bright spot is obtained from the photoelectric conversion element 7, and the peak hold circuit 11 holds the maximum value of the output of the photoelectric conversion element 7, and the output from the cathode ray tube is The brightness of the back porch signal B on l will be held.

- Simultaneously with the start of vertical scanning, the first integrating circuit 13 starts integrating the first reference voltage E1, and the hold value of the peak hold circuit 11 and the integrated value of the integrating circuit 13 become 1.
If there is a match within the field, the first comparison circuit 12 is activated. The output of the first comparator circuit 12 is turned on at the same time as the start of vertical scanning, and the circuit is configured such that the output is turned off when the comparator circuit 12 operates with input coincidence. A pulse having a time width proportional to the brightness of the back porch signal B on the cathode ray tube l detected by the element 7 is output. At the end of vertical scanning, the peak hold circuit 11 and the first integrating circuit 13 are turned off and set, and the above operation is repeated in synchronization with the free direct scanning signal, so that the output of the first comparing circuit 12 is B. For each field of No. 1,
A signal with a pulse width proportional to the brightness is output. The switch Sl is turned on only during the period when the output pulse of the first comparison circuit 12 continues, and the second integration circuit 14 sequentially changes the internal reference voltage E2 only during the period when the switch S1 is on. This second integrating circuit 1
The output of No. 4 has a value proportional to the cumulative time during which the switch Sl is on. The oT variable resistor R is for setting the soothing light beam, and when the output of the second integrating circuit 14 matches the value preset by the variable resistor R, the second
The comparison circuit 15 operates and outputs an output, the flip-flop circuit 17 is reset via the differentiating circuit 16, and the shutter 4 is closed by the driver circuit 18 to complete the photographing.

In this way, in the embodiment of the present invention, the brightness of this part is determined by utilizing the fact that l~ivy pouch signal B is the pedestal level P of the television signal and is 1, which is the reference part of the brightness of the screen. Since each field of the television signal is detected and the amount of dew J is determined based on the integrated value of its brightness, the brightness of the CRT 1 may change due to deterioration of the CRT 1, changes over time, temperature changes, etc. too.

The exposure amount determined by the variable resistor H is always obtained, and photography with stable film density can be performed.

In addition, when shooting by displaying a positive image on the tube surface of the cathode ray tube 1, the back porch signal B in the vertical scanning signal does not become bright on the tube surface, so the back porch signal is By adding a signal of a certain level that corresponds to B, the brightness of this part can be changed to
It is possible to perform accurate exposure control in the same way as in the case of negative display.

In the embodiment, the back porch signal B was used as the pedestal level P, but the front porch signal F
may also be used, and in this case, the position of the photoelectric conversion sensor f7 will be below the tube surface. However, since the number of rasters of the front porch signal F is smaller than that of the back porch signal B, restrictions are imposed on the measurement technique. Also,
The exposure control circuit is not limited to that shown in FIG. 6, and circuits with other configurations can be selected as appropriate.

As described above, according to the CRT screen photographing apparatus according to the present invention, when photographing a CRT screen, the pedestal level indicating the maximum brightness of the screen is set to the back porch signal of the vertical scanning signal or the brightness of the 70 point single signal. By detecting and measuring the brightness of the screen, it is now possible to accurately control the exposure value for the film in real time.

[Brief explanation of the drawing]

The drawings show an embodiment of the apparatus for photographing a cathode ray tube screen according to the present invention. FIG. 1 is an explanatory diagram of photographing a cathode ray tube screen, FIG. An explanatory diagram of the brightness when displaying in a negative state, Fig. 4 is a perspective view of the photoelectric conversion element attached to the cathode ray tube, Fig. 5 is a block circuit diagram of the front control circuit, and Fig. 6 is the cathode ray tube screen. FIG. 4 is an explanatory diagram of a vertical scanning signal when displaying in a positive state. 1 is a cathode ray tube, 2 is a mask plate, 3 is a lens, 4 is a shutter, 5 is a film, 11 (i peak hold circuit, 12.15 is a comparison circuit, 13.14 is an integration circuit, 16
is a differential circuit, 17 is a) 1) tube flop circuit, 18 is a dry/< circuit, St, S2t* switch, El, E
2 is a reference voltage. Patent applicant Kowa Co., Ltd. Drawings Figure 2, Figure 113, Figure 114, II! Figure 6

Claims (1)

[Claims] 1. A photoelectric conversion element disposed at a predetermined position on the surface of a cathode ray tube in order to detect the brightness of a signal other than an image signal related to screen brightness in a television vertical scanning signal, and the photoelectric conversion element What is claimed is: 1. A picture-taking device for a cathode ray tube screen, characterized by comprising an exposure control circuit that receives an output signal from an element, determines the exposure lid, and controls the opening time of the shutter in real time. 2. The apparatus for photographing a cathode ray tube screen according to claim 1, wherein a back porch signal is used as the signal relevant to the screen at one time. 3. The apparatus for photographing a cathode ray tube screen according to claim 2, wherein a constant level signal is added to the pack pouch signal when the screen is photographed in a positive state.