JPS60165886A - Color television camera - Google Patents

Abstract

PURPOSE:To offer a color TV camera which can obtain a picture signal with proper luminance information corresponding to a film density at the time of film image pick up by applying gamma correction to the luminace signal obtained by means of photometry of an incident light amount. CONSTITUTION:A light quantity from a color negative film 1l which is image picked up by a lens 3 and a signal process circuit 4 is measured by a photometry means and a gamma value of a gamma correction circuit 5 is controlled by a characteristic curve generator circuit 10. While a luminance signal from the circuit 4 is inputted to the circuit 5 whose gamma value is controlled, and applied with gamma correction, inputted to an inversion circuit 6 and inverted and inputted to an encoder 7. Thus a properly gamma corrected picture signal is obtained in correspondence with the light quantity incident to the lens 3, that is, the density of the film 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a color television (TV) camera that can always obtain an image signal having appropriate brightness information in accordance with the film density when photographing a film.

Prior Art and Problems Color TV cameras have comma correction circuits that compensate for the gamma values in the color TV receiver to provide an image output signal with an overall gamma of unity.

Moreover, the color TV camera has auto iris, AG
C; etc., the circuit is configured so that a constant image output can be obtained regardless of the amount of incident light.

For example, in a color negative film, there is a relationship between the negative density and the amount of transmitted light as shown in FIG. 1, for example. For example, transmitted light as shown in Figure 1! #range is a
and b (these are the ranges in which the amount of transmitted light changes linearly in response to negative density changes), and the transmitted sight range is in the ranges C and d (these are the negative density The amount of transmitted light changes non-linearly in response to the change in film density.
The relationship between the amount of light transmitted through the film and the electrical output of the TV camera is
As shown in FIG. 2, it can be seen from FIG. 2 that the gamma value of the film differs depending on the density.

Therefore, when a color negative film is imaged using a color TV camera, the density information in the color negative film is lost, and an image signal having appropriately gamma-corrected luminance information cannot be obtained.

Purpose of the Invention The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a color TV camera that can obtain an image signal having appropriate brightness information corresponding to the film density when photographing a film. With the goal.

Structure of the Invention The present invention provides an imaging means for imaging a subject to obtain a luminance signal, a photometry means for measuring the amount of light incident on the imaging means, and a gamma value that can be changed and that can be obtained by the imaging means. This color TV camera is equipped with a correction means for gamma-correcting the brightness signal obtained by the photometry, and a changing means for changing the gamma value of the correction means based on the photometry signal from the photometry means.

Embodiment of the Invention FIG. 3 is a block diagram showing an embodiment of a color TV camera according to the invention. In Figure 3, l is a color negative film, 2 is a light source, and these color negative films l
The light source 2 is placed at a predetermined location within a film imaging device (not shown), and a color TV camera, which will be described later, is also set at a predetermined location where it can image a color negative film l within the imaging device.

The color TV camera uses a lens 3 to capture an image formed by the lens 3 to generate a luminance signal (Y) and a color difference signal (R-Y,
A signal processing circuit 4 that obtains B−Y) and this signal processing circuit 4
A gamma value correction circuit 5 which inputs a luminance signal from a signal processing circuit 4 and performs gamma correction, and whose gamma value can be changed, and a color difference signal from a signal processing circuit 4 and an #open signal from a comma correction circuit 5. an inverting circuit 6 that inverts these; an encoder 7 that inputs the inverted one-time signal and color difference signal from the inverting circuit 6 and outputs a color composite dual image signal;
A mirror 8 arranged behind the lens 3 (but in front of the aperture) so as to project a portion of the light that has passed through the lens 3, and a photometer 9 that measures the amount of light from the mirror 8. From photometric means 9? It has a characteristic curve generation circuit 1O that changes the gamma value of the gamma correction circuit 5 based on the 1III optical signal.

The inversion circuit 6 has a changeover switch that allows each signal to pass through without being inverted.

The photometric means 9 detects the light from the mirror 8! The average value of the light incident on the lens 3 is photometered by the diffuser plate 4q and a phototransistor that receives the light from the diffuser plate.

Therefore, the photometric means 9 obtains a photometric signal having a value corresponding to the density of the color negative film 1.

The characteristic curve generating circuit 10 operates a gamma correction circuit 5 based on the photometric signal from the photometric means 8 so that a characteristic comma value as shown in FIG. 4 can be obtained depending on the amount of light incident on the lens 3. By controlling the i! An image signal gamma-corrected to 1ilti7J is obtained.

With the above configuration, the amount of light from the color negative film 1 that is imaged by the lens 3 and the signal processing circuit 4 is determined by the Al11 light by the photometry means. The gamma value of the gamma correction circuit 5 is controlled by the characteristic curve generation circuit 1O in accordance with the photometric signal obtained in this manner. On the other hand, the luminance signal from the signal processing circuit 4 is inputted to the gamma correction circuit 5 whose gamma value is controlled as described above for gamma correction, then inputted to the inversion circuit 6, inverted, and inputted to the encoder 7. . In this way, an image signal is obtained which has been gamma-corrected appropriately in accordance with the amount of light incident on the lens 3, that is, the density of the color ink film l.

FIG. 5 is a block diagram showing a part of another embodiment of the color TV camera according to the present invention, and since the other parts are the same as those in FIG. 3, illustration thereof is omitted. As shown in FIG. 5, the photometric means 9 includes a phototransistor 8A that receives light from a diffuser (not shown), a voltage extraction resistor 9B connected to the emitter of the transistor 9A, and a resistor 9B connected to the emitter of the transistor 9A. The smoothing circuit includes a resistor 9G and a capacitor 9D connected to the smoothing circuit. The output voltage of this smoothing circuit, that is, lI
The +1 optical signal is input to the window comparator 11.

As shown in FIG. 6, the window comparator 11 outputs a high (V) I) voltage only within a certain input voltage range.
In other input voltage ranges, the output voltage is low (VL).

As shown in FIG. 5, the comma correction circuit 5A has two correction circuits 12A and 12B having gamma values of 0.45 and 0.7, respectively, and these circuits 12A and 12B include a signal processing circuit. The cape melon signal from is input. Further, the outputs of these circuits 12A and 12B are connected to input terminals a and b of the electronic switch 13, respectively. The electronic switch 13 is controlled by the output of the window comparator 11 as follows. That is, when the output voltage of the window comparator 11 is high, the correction circuit 12B having a gamma value of 0.45 is connected to the output terminal of the electronic switch 13, and when the output voltage of the comparator 11 is low, the correction circuit 12B has a gamma value of 0.45. The correction circuit 12A having a comma value of 7 is '
It is connected to the output terminal of the 1-child switch i3.

Therefore, by setting the input voltage range in which the output voltage of the window comparator 11 is high to the ranges a and b shown in FIG. 1, for example, the film moisture content can be qualitatively addressed. The luminance signal can be comma-corrected.

The photometering means may be constructed such that, for example, a proximity switch is placed adjacent to the auto-iris lever which is normally connected to the lens, and the output of the proximity switch is used as a photometry signal.

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, by photometrically measuring the amount of light incident on the imaging means, based on this, both images having appropriate brightness information corresponding to the film density are determined. It is possible to provide a color TV camera that can receive signals.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an example of the relationship between negative density and amount of transmitted light;
Figure 2 is a diagram showing an example of the relationship between the amount of incident light on the film and the electrical output of the TV left camera, and Figure 3 is a diagram showing an example of the relationship between the amount of incident light on the film and the electrical output of the TV left camera.
FIG. 4 is a diagram showing an example of the comma characteristic in the gamma correction circuit obtained by the characteristic curve generation circuit, and FIG. 5 is a configuration diagram showing an example of the V camera.
FIG. 6 is a block diagram showing a part of another embodiment of the V camera, and FIG. 6 is a diagram showing the input/output characteristics of the window comparator. l...Color negative film, 2...Light source, 3...
Lens, 4... Signal processing circuit, 5... Gamma correction circuit, 6... Inversion circuit, 7... Encoder, 8.
...Mirror, 8...Photometering means, 10...Characteristic curve generation circuit, 11...Window comparator, 12A, 12B...Correction circuit, 13...Electronic switch. Figure 2: Amount of light transmitted through the fill Figure 3: Figure 4 Entry +: L amount

Claims (1)

[Scope of Claims] An imaging means for imaging a subject to obtain a luminance signal; a photometry means for measuring the amount of light incident on the imaging means; 1. A color television camera comprising: a correction means for extracting a comma from a luminance signal obtained by the photometry; and a changing means for changing a gamma value of the correction means based on a photometry signal from the photometry means.