JPH08214322A - Telecine camera - Google Patents

Abstract

PURPOSE: To secure the fidelity of an outputted image by providing a nonlinear circuit which performs color correction with characteristic opposite to the discoloring characteristic of a film. CONSTITUTION: Discoloring correction circuits 10-12 whose discoloring characteristics are provided with inverse function characteristics are used. Signals from photoelectric conversion elements 1-3 are amplified, and inputted to the discoloring correction circuits 10-12 via white balance circuits 7-9, and also, inputted to circuits 13-15 provided with linear characteristics. The output signals of the discoloring correction circuits 10-12 to which discoloring correction is applied at every color and that of the circuits 13-15 provided with the linear characteristics are inputted to multiplication circuits 16-18 forming pairs, respectively. The multiplication ratios of those two output signals are varied by the multiplication circuits 16-18, and they are inputted to signal processing circuits 19-21. The signal processing circuits 19-21 perform gamma correction, white clipping and white compression, etc., appropriately, respectively. The output signals of the signal processing circuits 19-21 are inputted to an encoder 22, and they are converted to regular composite video signals, and also outputted to a following stage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to color correction of a fading film in a telecine camera.

[0002]

2. Description of the Related Art A telecine camera has been conventionally used as an apparatus for capturing an image obtained from a movie or a slide film (hereinafter referred to as film) and generating a television signal. The so-called fading of the image on the film becomes noticeable after a lapse of time after development. FIG. 3 shows an example of this fading characteristic, in which the abscissa axis represents the transmittance of the film before fading, and the ordinate axis represents the transmittance of the film which is fading by a predetermined amount. Because of these characteristics, even if the image is taken with a telecine camera that has the linearity between the tone of the telecine camera and the tone of the video playback device side, when using a faded film, the Alternatively, the original linear image at the time of film development and the image output to the video reproducing device side cannot maintain the above linearity, and
The reproduced color will be far from the original one.
Generally, a faded film has a smaller transmittance of blue (B) and green (G) and a relatively larger transmittance of red (R) due to the characteristics of the color-developing body, resulting in a reddish color.

Conventionally, the telecine camera has dealt with the above problems by changing the characteristics of γ correction.
Generally, the γ correction function is divided into two, and the γ correction function of the flow of the video signal, which is closer to the signal source, is called pre-gamma, and the above fading correction is performed here. FIG. 4 shows a block configuration example of a video signal processing circuit of this telecine camera. In addition, in FIG. 4, the circuit configuration of three systems of R, G, and B is described with one figure.

Reference numerals 1, 2, and 3 denote photoelectric conversion elements which convert the image pickup light into electric signals. Preamplifiers 4, 5 and 6 amplify the signals from the photoelectric conversion elements 1 to 3, respectively. After that, the amplified signals are adjusted in white balance circuits 7, 8 and 9 to balance the three colors. After that, the pre-gamma correction circuit 41,
42 and 43 carry out correction in which the characteristics of the γ correction are changed corresponding to the above-described fading correction, and further gamma correction circuits 44, 45 and 46 carry out the conventional γ correction to carry out the correction. The respective signals are input to the encoder circuit 22 and converted into a composite video signal here.

[0005]

In the case of the above-mentioned conventional method, the input / output characteristics of gamma correction are e _o = e _i γ, where e _o : output (electrical or optical intensity), e _i : input ( Electricity or light intensity) and γ are arbitrary numerical values. In the case of a television system, normally γ = 0.45, and therefore, in the case of the characteristics such as the fading film shown in FIG. 3, accurate correction cannot be performed. Therefore, there is no 1: 1 correspondence between the image reproduced on the image receiving side and the original image in terms of gradation and color reproducibility. Furthermore, for the purpose of correcting non-linearity on the image receiving side, which is the original purpose of gamma correction, the standard for adjusting gamma becomes unclear, and it becomes difficult to maintain image fidelity.

It is an object of the present invention to eliminate these drawbacks and ensure the fidelity of the output image.

[0007]

In order to achieve the above object, the present invention provides a circuit having a non-linear characteristic as shown in FIG. 5 which represents a fading correction function characteristic which is an inverse function characteristic of a fading characteristic in a telecine camera. In order to correct the fading characteristics of the film, the normal gamma correction is then performed. This correction has a function of adjusting the correction amount according to the degree of fading.

[0008]

By using such a non-linear circuit, the fading characteristic shown in FIG. 3 is canceled by using a circuit having an inverse function characteristic, the input / output characteristic becomes a straight line, and fading correction is performed. That is, the characteristic of the fading film is e _o = k ₁ f _i
If (e _i ) and the correction characteristic is e _o ′ = k ₂ / f _i (e _i ), then e _o ′ = k ₁ k ₂ / e _o . Let k ₁ and k ₂ be arbitrary constants.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 1, 2 and 3 are photoelectric conversion elements. Usually R, G, B
The elements for the three colors are used separately. Reference numerals 4, 5, and 6 are preamplifiers corresponding to these elements, and are photoelectric conversion elements 1 to 3.
Amplify the signal from to the required level. After that, the amplified signals are input to the color fading correction circuits 10, 11 and 12 via the white balance circuits 7, 8 and 9, respectively, and to the circuits 13, 14 and 15 having the linear characteristic. The output signals of the color fading correction circuits 10 to 12 and the output signals of the circuits 13 to 15 having the linear characteristic are paired for each color and input to the multiplication circuits 16 to 18, respectively. In the multiplication circuits 16 to 18, the multiplication ratio of the above-mentioned two types of signals input to the multiplication circuits 16 to 18 is changed for each color by a control signal from a control circuit described later. The signals multiplied by the multiplication circuits 16 to 18 as described above are output and input to the signal processing circuits 19, 20, and 21.

The signal processing circuits 19 to 21 appropriately perform gamma correction, white clip, white compression, black clip, blanking insertion and the like. Signal processing circuit 19-
The output signal of 21 is input to the encoder circuit of 22,
Here, it is converted into a normal composite video signal and output to the subsequent stage. Of course, even if the synchronizing signal is applied to the outputs of the signal processing circuits 19 to 21 without being converted into the composite video signal by the encoder circuit 22 and the R, G, and B component signals synchronized with the synchronizing signal are output to the subsequent stage. Good.

The control circuit for controlling the above-mentioned multiplication ratio is preset in the main controller 29 in this embodiment, and the ratio among the R, G and B colors is parallel to the main controller 29. The circuit is preset with the connected variable resistors 26, 27 and 28. The variable resistors 26 to 28 are 23, 24 and 25, respectively.
, Connected to a DC amplifier composed of operational amplifiers,
The control signals for controlling the polarities of the R, G, and B colors in the correction direction and the correction amounts according to the input signal are output. Of course, the control ratio can be changed by changing the gain of each DC amplifier.

Next, a second embodiment will be described. In this embodiment, the multiplication circuits 16 to 16 for automatically performing fading correction are described.
18 is an example of a circuit configuration of control for controlling 18. Second of the present invention
2 showing the configuration of the control circuit of the embodiment of FIG. 2, the outputs of the multiplication circuits 16, 17, 18 are introduced into the circuits 30, 31, 32 having level selectivity, and the level selection is made by the differential amplifiers 33, 34. Signal of the output of the circuit 31 having the property and each of R and B of the outputs of the circuits 30 and 32 having the level selectivity.
The difference with the signal is taken, and these difference signals are fed to the DC amplifier 23,
Enter in 25. On the other hand, the Gch control is set by the main controller 29 in advance and is controlled through the DC amplifier 24.

Although not shown, the first and second embodiments
Of the variable resistors 26 to 2
It is also possible to adopt a configuration in which the manual setting operation in 8 and the automatic setting operation by the DC amplifiers 33 and 34 are switched by a switch or the like.

[0014]

As described above, according to the present invention, the reproducibility of gradations, colors and the like can be more faithfully reproduced to the original image when the fading film is imaged and a television signal is generated.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of implementation of the present invention.

FIG. 2 is a diagram showing a configuration of a control circuit according to a second embodiment of the present invention.

FIG. 3 is a diagram showing the fading characteristics of a fading film.

FIG. 4 is a diagram showing a block configuration example of a video signal circuit of a conventional telecine camera.

FIG. 5 is a diagram showing characteristics of a fading correction function.

[Explanation of symbols]

 1,2,3 Photoelectric conversion element 4,5,6 Preamplifier 7,8,9 White balance circuit 10,11,12 Discoloration correction circuit 13,14,15 Circuit having linear characteristics 16,17,18 Multiplier circuit 19 , 20, 21 Signal processing circuit 22 Encoder 23, 24, 25 DC amplifier 26, 27, 28, 29 Variable resistor 30, 31, 32 Circuit having level selectivity 33, 34 Differential amplifier

Claims (2)

[Claims] 1. A telecine camera for picking up a film image, comprising a non-linear circuit for performing color correction with an inverse characteristic of a film fading characteristic. 2. The telecine camera according to claim 1, wherein the degree of the color correction can be varied.