JPS634384B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a television camera with a built-in pattern projector, in which a test pattern projector is fixedly or removably attached to the objective lens of the television camera.

Currently, most color TV cameras used for broadcasting are of the three-tube type, and when replacing the image pickup tube, during regular maintenance, or before starting operation, a series of adjustment operations are required to ensure good color image quality. Requires. Conventionally, test patterns such as resolution, registration, grayscale, etc. are illuminated with flat light, and after facing the imaging lens and framing to the regular dimensions, the CCU adjuster ( Some of this is done by moving the camera (located on the camera side). A commonly used method for imaging this type of test pattern is to illuminate a transmissive or reflective test pattern with external light. However, in the case of this method, it is necessary to exchange patterns and perform setting operations each time, which requires a lot of effort and time.

On the other hand, although the stability of color TV cameras has been significantly improved, there are cases where it is necessary to check using test patterns even during operation, which is difficult to do with the above-mentioned method.

In order to improve the operability of color TV cameras by improving these problems, a method has been developed in which a test pattern projector is built into the zoom lens, which is the objective lens of a color TV camera (in the normal case). Due to insufficient performance, it is only used in supplementary applications.

Next, the reason will be explained using drawings.

Referring to FIG. 1, a conventional method of imaging a test pattern using external light illumination will be described. A light source 1 illuminates a reflective test pattern chart 2, such as a gray scale, and the chart 2 is passed through a three-color separation prism system Y through a zoom lens X consisting of a zoom section 1 and a relay section.・After color separation into green and blue region light,
An image is formed on the light receiving surface of each image pickup tube 3RGB. At this time, chart 2 is normally illuminated by light source 1 so that the color temperature is 3000 and illuminance is 2000 lux, which are the standard imaging conditions, and the brightness on the image pickup tube light receiving surface is adjusted by aperture 4 of zoom lens X. do.

On the other hand, the imaging method using the built-in pattern projector is
A transmission type test pattern chart 2', such as a gray scale, is illuminated through a condenser lens 9 using a light source 1' such as a tungsten incandescent lamp.

The light passing through the chart 2' is reflected by the reflecting mirror 12 and then enters the projection lens 8. The light emitted from the projection lens 8 is reflected by the prism-shaped half mirror 6 disposed between the relay lens front group 5 and the relay lens rear group 7 of the relay section of the zoom lens X, and then reflected by the relay lens rear group 7 and the relay lens rear group 7. The light passes through a three-color separation prism system Y and is color-separated into red, green, and blue light, and reaches the light receiving surface of each image pickup tube 3RGB.
At this time, the projection lens 8 and the relay lens rear group 7 separate the image pickup tubes 3 for each of the red, green, and blue regions.
A chart 2' is imaged on the RGB light receiving surface.

Here, the power supply for the light source 1 of the built-in pattern projector is usually a stabilized DC voltage of 24 V and a current capacity of 0.75 A, which is common to the circuit power supply of the color TV camera, so the light source 1' may be a halogen bulb or the like. High color temperature light bulbs such as optical light bulbs with flat-wound filaments cannot be used, and ordinary tungsten incandescent light bulbs with a color temperature of 2550 ± 50 are used, so they cannot be used in outdoor light. Compared to light source 1 in lighting, it is about 450 times lower.

In addition, the spectral transmittance characteristics of the zoom lens many. on the other hand,
In the built-in pattern projection optical system, the overall thickness of the glass is much thinner than that of the Zoom Lens .

Based on the above, when comparing the imaging state of the test pattern with external light illumination and the imaging state of the test pattern with the built-in pattern projector, it is found that the brightness of both methods on the light receiving surface of the image pickup tube 3G for green region light is equal. Then, the latter method becomes brighter on the light receiving surface of the red region light imaging tube 3R, and the former method becomes brighter on the light receiving surface of the blue region light imaging tube 3B. Therefore, a color filter (spectral characteristic correction filter) 10 and an ND filter 11 for adjusting the light amount so that the brightness of the former method matches that of the latter method are arranged near the condenser lens 9 of the built-in pattern projector. has been done.

Therefore, in the conventional method as described above, the imaging state of the test pattern by external light illumination and the imaging state of the test pattern by the built-in pattern projector have a certain color temperature (3000〓 in the above embodiment).
There was no match at other color temperatures.

On the other hand, as TV cameras have become more sophisticated and more compact, their range of use has expanded, and in addition to being used in indoor studios, they are now being used for broadcasting sports, theaters, etc.
Furthermore, news programs that previously used 16mm cine have recently begun to use small TV cameras called ENG.

Therefore, the illumination conditions of the subject to be imaged by the television camera also have a very wide range. For example, outdoors, the color temperature in the morning and evening is between 2000 and 4000, and in daylight.
The color temperature changes from 6000 to 7000 over time. Conventionally, the following method has been used to adjust the television camera under such lighting conditions. The design standard color temperature of ordinary television cameras is set to 3000〓 or 3200〓. Therefore, for example, when photographing a subject under lighting with a color temperature of 6000〓 using a television camera with a design standard color temperature of 3000〓, the color temperature conversion filter built into the television camera (usually a zoom lens) is used. If there is a filter that converts 6000〓 to 3000〓 (placed between Zoom lens
The white and black balance was adjusted by adjusting the amplification factors of the red and blue camera tube outputs relative to green.

However, in the current built-in pattern projector, since the color temperature is fixed, it is impossible to deal with arbitrary color temperature or changes in color temperature as described above.

As described above, the current built-in pattern projector does not match the imaging state of the test pattern with external light illumination due to a number of factors, and therefore, the reality is that it is only used in an auxiliary manner.

The object of the present invention is to eliminate the above-mentioned drawbacks, to put a built-in pattern projector into practical use, and to improve the operability of a color TV camera.

This purpose is characterized in that the light incident on the objective lens is used to illuminate the test pattern chart of the built-in pattern projector.

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

FIG. 2 is an embodiment of a built-in pattern projector according to the present invention.

An optical path switching prism mirror 21 is disposed between a relay front group 5 and a relay rear group 7 of a relay section of a zoom lens X. Note that this prism-shaped mirror 21 is located outside the effective beam of light that exits the relay front group 5 and enters the relay rear group 7 when the zoom lens 2' is assumed to be inserted into the effective light flux. Zoom lens
The incident light passes through the zoom section and the front relay group 5, is reflected by the mirror surface 22 of the prism mirror 21, and then enters the condenser lens system 27.
The light emitted from the condenser lens system 27 changes its optical path by the reflecting surfaces 25 and 26 of the optical path deflection prism 24, and illuminates the test pattern chart 2'.
The light that has passed through the test pattern chart 2' enters the projection lens 8, and the light emitted from this is reflected by the reflective surface 23 of the prism-shaped mirror 21, and then
The light passes through the color separation prism Y and reaches the light receiving surface of the image pickup tube 3G. In this figure, only the green area light portion of the three-color separation prism Y as shown in FIG. 1 is shown.

At this time, the test pattern chart 2' is imaged on the light receiving surface of the image pickup tube 3G by the projection lens 8 and the relay rear group 7.

At this time, depending on the zoom section, the relay front group 5, and the condenser lens system 27, the subject in front of the zoom lens
If the image is formed upward, the image of the test pattern chart 2' will overlap with the subject image, causing problems in camera adjustment. Therefore, by placing a diffuser plate 28 such as ground glass in the condenser lens system 27, the test pattern chart 2' This prevents the subject image from appearing above. Note that the same effect can be obtained by placing the diffuser plate 28 in the zoom section or the relay front group 5, but this diffuser plate 28 is only necessary when using the built-in pattern projector and is not necessary during normal imaging.
It is necessary to take the diffuser plate 28 in and out.

On the other hand, if it is placed inside or near the condenser lens system 27, it is advantageous because the diffuser plate 28 can be fixed because it is an optical system dedicated to the built-in pattern projector. Furthermore, since this device is a television camera, the relationship between the test pattern chart 2' and the subject image can be easily confirmed using a monitor television or an electronic viewfinder. Therefore, by using a diffuser plate 28 with low diffusivity or omitting it, the loss of light amount caused by this can be reduced or eliminated. However, in this case, check the relationship between the test pattern chart 2' and the subject image on a monitor TV, etc., and rotate the zoom ring and focus ring of the zoom lens It is necessary to make sure that this does not happen.

Regarding the color temperature of the built-in pattern projector, the same light source as that of the object to be imaged is used in the built-in pattern projector, and the zoom lens X is common to both, and only the built-in pattern projection optical system Z is different. However, the transmittance of only the built-in pattern projection optical system Z has a fairly flat characteristic because its total glass thickness is relatively thin, and can be corrected by coating or the like.

Also, regarding the amount of light, the aperture 4 of the zoom lens
Make adjustments. At this time, the aperture 4' of the projection lens 8 and the aperture 4 of the zoom lens
It is convenient to set the optical constants such as the focal length of the condenser lens system 27 so that they are almost reciprocal, since uniform illumination can be obtained. Naturally, the aperture 4'
It is also possible to adjust the light amount by

In this example, the built-in pattern projector is used to shoot a white or almost achromatic subject using the zoom lens
Aim at the state where the subject is most blurry, that is, set the zoom position of the zoom lens X near the maximum focal length,
Set the focus to either close range or infinity, then switch to the built-in pattern projector,
If the light intensity is adjusted using the aperture 4 of the zoom lens The imaging state by the built-in pattern projector matches.

It goes without saying that the prismatic mirror 21 and the optical path polarizing prism 24 in the figure can be replaced with ordinary mirrors.

In addition, in the present invention, as mentioned above, TTL
By lighting with the (THROUGH THE LENS) method, color temperature can be measured under the lighting conditions checked on a monitor, etc., making it possible to match the imaging conditions with high precision.

As described above, according to the present invention, it is possible not only to easily match the imaging state of a test pattern using conventional external light illumination and the imaging state using a built-in pattern projector, but also to make it possible to easily match the imaging state of a test pattern using conventional external light illumination. This saves power and eliminates problems such as lamp disconnections and heat generation.Furthermore, the imaging conditions of the external lighting and the built-in pattern projector match even under lighting of any color temperature. This makes it possible to put a built-in pattern projector into practical use and significantly improves the operability of color television cameras.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the optical layout of a conventional television camera, and FIG. 2 is a diagram showing the optical layout of the television camera of the present invention. In the figure, X is a zoom lens, is a zoom part, is a relay part, Y is a color separation prism, G is an image pickup tube, and 5
2 is a front relay group, 7 is a rear relay group, 21 is a mirror prism, 27 is a condenser lens, 28 is a diffuser plate, 2' is a test pattern, and 8 is an imaging lens.

Claims (1)

[Claims] 1. In a television camera having a pattern projection unit that introduces light from a test pattern into the optical path of an objective lens to form a test pattern image on an imager, the light incident on the objective lens is converted into a test pattern. A television camera characterized in that a light source for illuminating the test pattern is not required by providing a light guiding optical system and illuminating the test pattern with light from the light guiding optical system. 2. The television camera according to claim 1, wherein the light guide optical system includes a diffuser plate. 3. The television camera according to claim 1, wherein the aperture of the objective lens and the aperture of the pattern projection section are substantially the same.