JPS61208370A - Photoelectric converting device - Google Patents

Abstract

PURPOSE:To attain setting of proper gamma curve even when a part of sharp density-difference exists in the image by detecting the minimum, maximum, and average values using the values from the photoelectric transferring, setting, the aperture of an optical diaphragm or the gain of an amplifying circuit, and by setting the D.C. level of a clamp circuit. CONSTITUTION:An output obtained by the main scanning and subscanning by a CCD line sensor 5 that is made a pre-scanner, appears in the output of an OB clamp circuit 8, and its part shielded by a frame out of the film is detected by a frame-detecting circuit 9. In a CPU 16, the output value of a light-quantity integrating circuit 12 is divided by that of a time integrating circuit 13 in order to calculate an average-density information. Following the pre-scanning, the main scanning is executed. And when the latter is executed, the output of the OB clamp circuit 8 is gamma-corrected by an analog gamma correcting circuit 17 to provide an easy gamma-digital correction. The signal is converted to a digital one by an A/D converter, and further, gamma-corrected by a RAM 19 for digital-gamma-correction, and then inputted to an image memory 20 to be displayed in a displayer 21.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a photoelectric conversion device that converts an optical signal obtained based on image information recorded on a film into an electrical signal.

(Snowscape of the Invention) The density distribution range of an image recorded on a negative film or a positive film photographed by a camera system using silver halide film varies depending on the exposure and development conditions of the film at the time of each photographing. For example, the density distribution range of the image recorded on the film varies depending on overexposure, underexposure, the brightness distribution state of the surface of the object, etc. Using such films with various density distribution ranges as they are, the back side of the film is illuminated with a light source with a constant amount of light, and the transmitted light is converted into a photoelectric conversion element (for example, CO2).
It is difficult to obtain a reproduced image with appropriate gradation when photoelectrically converting the image into an electric signal using a D-line sensor and then reproducing an image from the electric signal.

Furthermore, let's consider the photoelectric conversion device in the conventional photoelectric transmission system. Traditional photographic transmission systems develop negative (positive) film photographed by a camera.
The photographic paper is exposed and printed based on the developed film, and the printed photographic paper is irradiated with a certain amount of light.
The reflected light is converted into an electrical signal by a photoelectric conversion element and transmitted to a telephone line or the like. Therefore, in the conventional photographic electronic transmission system, the density distribution of the image is biased due to the gamma characteristics of the film used and the exposure conditions at the time of shooting. Photoelectric conversion can be performed on the top. However, in the new photographic transmission system, which uses developed film as it is to photoelectrically convert it and transmits it using a telephone line, etc., the density distribution of the image may be biased due to the gamma characteristics of the film used or the exposure conditions at the time of shooting. Since it was difficult to correct this, there was a problem in that the image quality of the reproduced image on the receiving side was extremely poor and could not be put to practical use.

Therefore, for films with various exposure conditions.

The minimum density of an image recorded on negative or positive film (
The values of the most transparent part) and the maximum (blackest part) are detected, and the level of the electrical signal obtained by photoelectrically converting the transmitted light of the minimum density part is determined by the opening of the optical aperture means or the gain of the amplifier circuit. The level of the electrical signal obtained by photoelectrically converting the transmitted light of the maximum 1 degree portion is set within the predetermined range by controlling the DC level. The applicant has already proposed this technique in Japanese Patent Application No. 58-198745. According to this, if a very small area of the film contains extreme density information 2. For example, if there is small dust or scratches on the film, it will be judged as an image with a very large gradation difference. A gamma curve is selected based on the gamma curve, and the aperture opening and DC level determined by the gamma curve are determined to perform density correction, so that the density is biased. Low contrast (
It has been confirmed that this method has a drawback in that it results in images with a soft tone.

(Object of the Invention) The present invention solves these drawbacks and provides a photoelectric conversion device that performs appropriate density correction without being affected by extremely bright or dark areas in extremely small areas on the film screen. The purpose is to obtain.

(Summary of the Invention) The present invention detects the minimum (most transparent part), maximum (blackest part), and average values of the density of an image recorded on a negative film or a positive film using photoelectric conversion values, and The opening of the optical diaphragm means or the gain of the amplifier circuit is set so that the maximum value becomes less than a predetermined value, the DC level of the clamp circuit is set so that the maximum value becomes a predetermined value or more, and the maximum value The technical point is to determine gamma characteristics to obtain appropriate gradation based on the relationship between the minimum and average values.

(Embodiment) FIG. 1 shows an embodiment of the present invention, in which a light source 1 illuminates a film 2, and its image is transmitted through a lens 3. CCD through aperture 4
An image is formed on the line sensor 5. CCD line sensor 5
performs plane scanning by self-scanning (main scanning) and scanning at low speed by a mechanical mechanism (not shown) (sub-scanning).

The output of the CCD line sensor 5 is adjusted to an appropriate level by the head amplifier 6.

After being amplified, a low pass filter (LPF) 7 removes clock noise and optical black (OB
) The clamp circuit 8 allows the optical black part to
It is clamped and the DC component is regenerated.

First, before creating one image, COD is performed at high speed.

scanned. This is called prescan. Here, prescan will be explained.

Prior to pre-scanning, minimum density detection circuit 10, maximum density detection circuit 11. Light amount integration circuit 12゜Time integration circuit 1
3 voltage is initialized (reset).

Next, when pre-scanning is performed, the signals obtained by the main and sub-scanning of the CCD line sensor 5 appear at the output of the OB clamp circuit 8, and are detected by the frame outside the film by the frame detection circuit 9.
Detect parts sold at low prices.

It is controlled so that it is not included as information on the necessary parts. In the pre-scan, the output of the OB clamp circuit 8 is held by the minimum density detection circuit 10 (peak hold circuit) to hold the voltage of the lightest density part of the nine screens, and the output from the maximum density detection circuit 11 (peak hold circuit) and frame detection. circuit 9
The voltage of the part with the highest density in the effective screen outside the frame is held by the signal from

The light amount integrating circuit 12 integrates the light amount within the effective screen during pre-scanning, and the 2-hour integrating circuit 13 measures the area of the effective screen from the output of the frame detection circuit 9. The above minimum and maximum concentration detection circuits 10, 11. amount of light.

The output signals of the time integration circuits 12 and 13 are switched by the analog switch 14, and then taken into the CPU 16 as a digital signal by the A/D conversion circuit 15. CPU
16, the output value of the light amount integration 'circuit 12 is transferred to the time integration circuit 1.
The average density information is calculated by dividing by the output value of 3.

Based on the above information, the CPU 15 performs arithmetic processing and
and sends data to the digital gamma correction RAM 19. Here, the digital gamma correction RAM is a lookup table created by storing correction data in advance to enable various gamma corrections.

With this, the pre-scan is completed, and the ninth main scan is performed. When the main scan is performed, the output of the OB clamp circuit 8 is gamma-corrected in advance by the analog gamma correction circuit 17 to make digital gamma correction easier.
The signal is converted into a digital signal by the /D conversion 18, and then subjected to gamma correction by the digital gamma correction RAM described above, and then input to the image memory 20 and displayed on the display 21.

It is also printed by a printer 211 or the like.

When sending photos to a long distance via telephone or other lines,
Yo,, Ino\Ya's transmission speed, □7. scan slowly,
After storing data for one line of pixels of COD in the line memory 22, it is read out and D
/A conversion 23.

After converting it into an analog signal and passing it through the 1-line filter 24, it is subjected to AM modulation or FM modulation by the modulator 25 and output to the 1-line.

FIG. 2 is a circuit diagram showing the main parts of the embodiment shown in FIG. 1 in more detail. In Fig. 2, S, a to ■ Sad are the frame detection IC, #C9, and the reference voltage source Vref.
It is controlled by a signal from a frame detection circuit 9 consisting of 3, and is closed when inside the frame and open when outside the frame.

Sta'''S, d is an initial reset switch, which is closed before measurement to set the signal to the initial state, and during measurement.

It's open. Ic, ~, are operational amplifier circuits +R1~, are resistors I C1-C4 are capacitors, and DI-2 are diodes. Ict+ Ict+ R+ +
D+C1l constitutes a positive peak-hold circuit, that is, a minimum density detection circuit 10, which measures the minimum density of the film.

Ic, , Ica+ R2+ D@ * C2 creates a negative peak-hold circuit, that is, maximum concentration detection circuit 1
1 is constructed to measure the maximum density of the film.

R3, C'l+ Ic5 is a circuit that measures the integral value of the amount of light, and + Rs * Rh + I Ch is a conversion circuit that inverts the output voltage and converts it into a voltage suitable for input to the A/D conversion circuit 15. These circuits constitute a light amount integrating circuit 12.

Vreft, R4, Ca, and Icy measure the time within the frame (effective screen area) by integrating the constant voltage Vreft, and calculate +ICm+R? ＋R
s, and these constitute a time integrating circuit.

14 is an analog switch that switches each signal to A/D
It is output to the conversion circuit 15.

FIG. 3 is a diagram showing the frequency of standard negatives by density, where A is the minimum density, B is the average density, and C is the maximum density. For such a standard negative, it is possible to obtain a positive image signal output with an appropriate gradation even with only the maximum and minimum densities.

Figure 4 is a diagram showing the frequency of negatives by density when the subject has dark parts or shadows, and the minimum density A is the average density B.
I get away from it. In this case as well, in the present invention, it is possible to set a gamma curve by determining the average density, and it is possible to obtain an appropriate positive image signal output, and furthermore, it is possible to cut out dark portions.

In FIG. 5, the difference in synthetic leather B is large when there is bright lighting in the subject. In this case as well, it is possible to obtain an appropriate positive image signal output as in FIG.

(Effects of the Invention) As described below, according to the present invention, it is possible to set an appropriate gamma curve even when there are parts with extremely different densities.

[Brief explanation of drawings]

FIG. 1 shows an embodiment according to the invention. FIG. 2 is a circuit diagram showing the main parts of the embodiment in detail. FIG. 3 is a diagram showing the frequency of negatives according to density in a product-moment manner. FIG. 4 is a diagram showing the frequency by density when there is a shadow or a dark part in a part of the subject. FIG. 5 is a diagram showing the frequency by density when there is a particularly bright part such as illumination in a part of the subject. (Explanation of symbols of main parts) 2--m-film 4--one aperture 5--- CCD line sensor 10--m-minimum density detection circuit 11--one maximum density detection circuit 12-- -Light amount integration circuit 13---One hour integration circuit

Claims (1)

[Claims] an optical system that illuminates the film; a photoelectric conversion element that converts light transmitted through the film by the optical system into an electrical signal; and density detection means that detects the maximum, minimum, and average densities of the film from the output of the photoelectric conversion element. , a calculation means for performing a predetermined calculation based on the output of each of the concentration detection means, a control means for controlling the level of the electrical signal output to be within a certain range based on the output of the calculation means, and A photoelectric conversion device comprising: a gamma correction means for determining a gamma value based on the output, and applying gamma correction to the electrical signal output using the determined gamma value.