JPH0610723B2 - Imager for color negative film - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus which is used in a photo lab or the like and obtains a simulation image of a print used for observing a color negative image photographed on a photographic film. .

Conventional technology Generally, the screen of a color negative film has a distribution of light and darkness and colors, and has different blue, green, and red densities in each part of the screen, but those negative films are not always suitable. The image is not taken with the exposure amount, and the exposure amount must be adjusted appropriately during printing.

However, in most cases, by controlling the amount of transmitted light of the three color components of blue, green and red over the entire area of the screen to be constant,
I try to create prints with a good color balance and print quality. This is based on an empirical rule that in a normal shooting scene, the average reflectances of the three colors obtained by integrating the entire scene are substantially constant. Those skilled in the art refer to this as a LATD (all area average transmission density) control method. That is, when a neutral general subject is photographed with a color negative film, the average transmission density depends on the overexposure and underexposure, the light quality of the light source at the time of photography, the sensitivity of the blue, green, and red photosensitive layers of the color negative film, and the presence or absence of a microphone. Although changing, these changes are automatically controlled by making the exposure exposure amounts of blue, green and red constant during printing.

On the other hand, the density change of the three colors of the color negative film caused by the different color distribution of the subject changes the area ratio of the three colors of the subject.
It has a property that it is not automatically controlled by the LATD control method.

In addition, when the brightness configuration is extremely biased compared to the normal brightness distribution, such as when there are extremely high brightness areas or when there are many low brightness areas compared to a normal scene, for example, when the scene is large. The density change of the negative film that occurs when the area is composed of the shadow part or the highlight part is due to the area change of the density of the subject. It cannot be corrected by the LATD control method that controls the quantity. In addition, when the main subject constitutes a shadow portion or an extreme highlight portion as compared with surrounding subjects, these cannot be corrected because the scene configuration greatly differs from the conditions set by the printer.

Those skilled in the art call a scene in which a print with an imbalanced color balance is photographed as a color ferria, and a scene in which a print with an unsatisfactory print quality is produced as a density ferria. The rate of appearance of these varies depending on the time of year, but color feria is around 5%, and density feria is
It is said to be 30-40%.

On the other hand, a normal color printer has a correction key with a constant exposure amount variation range of 10 to 20%, and the operator extracts the characteristics of the scene for each original image and selects the correction key as appropriate. A good print can be created by changing the exposure amount for each of blue, green, and red. For example, when a subject such as a person is highlighted in a flash scene, and the surroundings are dark, light printing can be performed according to the LATD control for the reason described above. Recognize that and decide the degree of baking based on experience. In addition, for a scene in which a specific color has a strong control, such as a red string, if the LATD control is performed, it is controlled to make the whole gray, and the red of the red string is not reproduced. Create prints by changing the balance of the amount of green / red printing light based on experience. Not only the above example, but also suitable for various shooting scenes.
A great deal of skill and experience is required because the relationship between the characteristics of each scene and the print to be created must be known in order to determine the printing exposure amount for each of green and red.

On the other hand, by reproducing a simulation image of a print using a video system and observing this image, it is possible to make the above skill and experience unnecessary. That is, TV
An image on a color negative film is picked up using an image pickup device such as a camera, and the average value of the image signal or the function output of the image signal is controlled so as to be constant, and LAT can be obtained by inverting the image
It is possible to reproduce the print simulation image after correction by reproducing the print simulation image by the D control method and changing the reproduction level of this display image. Therefore, the operator does not have to predict the print result and is easy. It is possible to determine the optimum printing exposure amount.

In a television camera, which is generally the simplest and cheapest imaging device, the following example is a typical method for controlling to keep the average value of the video signal constant.

As a first method, there is a method in which the diaphragm of the lens used for image formation on the photocathode is sequentially subjected to feed-bic control by the average value of the video signal. That is, by controlling the diaphragm according to the magnitude of the average value of the video signal, the amount of light incident on the photocathode can be adjusted and the average value of the video signal can be made constant.

As a second method, there is a method in which the sensitivity of the image pickup tube is sequentially feedback-controlled by the average value of video signals.
When a vidicon is used as the image pickup tube, its image pickup sensitivity changes depending on the level of the target voltage. Therefore, the average value of the video signal is amplified by DC and fed back as the target voltage to automatically adjust the sensitivity to the amount of incident light,
It is possible to make the average value of the video signal constant.

However, the sequential feedback control based on the average value of the video signal as in these examples has a drawback that the control time is very long and the control accuracy is low and the video signal is not stable if the control time is not sufficiently taken. The video signal is obtained by repeating the vertical scan by repeating the vertical scan by repeating the horizontal scan vertically with respect to the normal screen for a fixed number of times. In order to make the control follow the average value of the video signal of the entire screen without being influenced by the video signal of a part of the screen, the control speed, which should be called the time constant of the control, is compared with the vertical scanning cycle. However, it is necessary to make it slow enough, and when the control speed is increased, feedback control is performed by part of the video signal of the screen,
Not only is the average value of the video signal not constant, but unnecessary fluctuations are added to the video signal, which makes the video signal extremely unstable. Therefore, the above-mentioned method which is usually used can be used for monitoring without abrupt change of the incident light amount in a short time, but a large change in average density for each frame as the invention is applied. This is an inconvenient control method for obtaining a stable video signal by capturing a large amount of images on a color negative film, which may be accompanied, in a short time and while controlling accurately.

An object of the present invention is to solve this problem in view of various problems in the method of controlling the average value of the video signal, and to stabilize while capturing an image on a color negative film accompanied by a rapid change in the amount of incident light in a short time. It is possible to obtain high-speed and high-precision control results at the same time as obtaining various video signals, and it is possible to continuously test a large amount of color negative film. It is intended to provide an unnecessary imaging device.

According to the above-mentioned object, an image pickup means for outputting a video signal from an image on a color negative film while moving a horizontal scan in a vertical direction, and a video signal obtained during at least a vertical scanning period of the video signal output from the image pickup means. Calculating means for calculating an image pickup condition based on the above, and a sensitivity adjustment for adjusting the image pickup sensitivity of the image pickup means on the basis of the adjustment signal outputted from the calculating means, and for holding at least a vertical scanning period. And a color negative film imaging device.

Embodiment FIG. 1 is a block diagram showing an embodiment of an image pickup apparatus according to the present invention, and FIG. 2 is a timing chart showing the timing of each signal in this embodiment.

The subject image formed on the photoelectric surface of the image pickup tube 100 is photoelectrically converted, and sequentially scanned by the electron beam deflected by the deflection circuit 103 in the horizontal direction which is the main scanning direction and the vertical direction which is the sub-scanning direction. Is output as. The vertical scanning is completed by repeating the horizontal scanning in the vertical direction with respect to the normal screen periodically, and the vertical scanning is completed. However, the '1' code period of the vertical synchronizing signal (negative logic) shown in FIG. Corresponds to the period. The video signal output from the image pickup tube 100 is amplified by a video signal amplification circuit 101, and then a synchronization signal is added by a synchronization synthesis circuit 102 and output. On the other hand, the increased video signal is simultaneously integrated by the integrating circuit 106 during the '0' code period of the integration command signal (negative logic) synchronized with the vertical synchronizing signal. During the '1' code period of the integration command signal, the charge accumulated in the integration circuit 106 according to the video signal is discharged, the integration circuit 106 is initialized, and the integration signal shows the initial state. The integrated signal is sampled by the sample and hold circuit (S / H) 105 according to the sample and hold (S / H) command signal that is output after the vertical scanning period and after the vertical scanning period.
To be held. Therefore, it was sampled and held (S /
H) The integrated signal is equal to the integrated value of the video signal obtained during the vertical scanning period. The sampled and held integrated signal is DC-amplified by the DC-amplifying circuit 104, and the image pickup tube 1 is used as a sensitivity adjustment signal.
Given to 00. Therefore, the sensitivity adjustment signal is the DC widening circuit 10
It is output as a function of the integral signal defined by the characteristics of 4. This enables control so that the integrated signal has a predetermined value. For example, when the imaging sensitivity increases or decreases according to the level of the sensitivity adjustment signal, the characteristics of the DC amplification circuit are that the sensitivity adjustment signal is high for a low integration signal and low for a high integration signal as compared to a predetermined value. It suffices to give a decreasing function to the integral signal that outputs the sensitivity adjustment signal.

Here, in order to obtain high control speed and control accuracy, it is desirable to define the characteristics of the DC amplification circuit from the relationship of the integrated signal with respect to the sensitivity adjustment signal. Further, since the sampled and held integrated signal is held until just before the next sample and hold command signal is output, this DC-amplified sensitivity adjustment signal is also held at least for the next vertical scanning period. Signals that control the timing of signals such as the vertical synchronizing signal, the integration instruction signal, and the sample and hold instruction signal are output from the synchronizing circuit 107.

As described in the above embodiment, according to the present invention, the image signal is integrated every vertical scanning period, and the image pickup sensitivity can be controlled by the obtained integrated signal. High-speed, high-precision control is possible without the control being affected.

Furthermore, since the sensitivity adjustment signal can be held for at least the vertical scanning period, a stable video signal output can be obtained.

FIG. 3 is a block diagram showing an embodiment in which a part of the control circuit is digitalized in the image pickup apparatus according to the present invention.

Similar to the above example, the video signal is integrated by the integrating circuit 307 during one screen scanning period. The obtained integrated signal is analog or digital
The analog / digital (A / D) converted signal is sent to the CPU 308 by the (A / D) conversion circuit 306. The CPU 308 sends an output corresponding to the integrated signal to the digital / analog (D / A) conversion circuit 305 according to a specific logic flow. The digital / analog conversion circuit 305 converts the digital signal sent from the CPU 308 into an analog signal and holds it until the next signal is sent. This signal is DC-amplified by the DC-amplification circuit 304 and given to the image pickup tube 300 as a sensitivity adjustment signal.

The signal timing is controlled by various synchronizing signals output from the synchronizing circuit 309, and is also controlled by the CPU 308 with reference to the synchronizing signals sent from the synchronizing circuit 309.

When the integrated signal is converted into a digital signal through the analog / digital conversion circuit and the sensitivity adjustment signal is output through the digital / analog conversion circuit according to the function defined for the digital signal as in the above embodiment, the sensitivity is It is possible to perform control that is less dependent on the relationship between the adjustment signal and the imaging sensitivity, and it is possible to improve control accuracy. This is because the function that defines the relationship between the sensitivity adjustment signal and the integral signal is uniquely determined by the characteristics of the DC widening circuit in the analog control circuit described above, whereas in the digital control circuit as in the above embodiment. In case of, it is easy to add judgment function,
Therefore, there is a point that the above function can be elastically defined according to the integral signal and the like. Examples include changing the control time and the target integration value according to the integration signal, and adaptively changing the above function from the locus of changes in the integration signal accompanying control. It is also possible to define the above function by an external signal such as a measured value of transmitted light of an image on a color negative film. Furthermore, if a filter for three-color separation is placed in front of the image pickup device and this filter is rotated and the video signal of each color is guided in synchronization with this rotation, the target integrated value of each color does not necessarily match, so depending on the timing. It is easy to change these target integral values.

In addition, a signal conversion circuit is provided in the preceding stage of the integration circuit, a video signal is converted through this circuit, integrated, and controlled by the obtained integrated signal as in each of the above-described embodiments. LAT the simulation image by the signal
This is effective in that it is closer to the printed image by D control. That is, the photoelectric conversion characteristic of the image pickup device is usually different from the photoelectric conversion characteristic of the light receiver used for the LATD control of the color printer. Therefore, in order to obtain a simulation image of printing under LATD control, it is desirable that these characteristics match. Therefore, it is rational from this point that the video signal integrated as described above is a signal converted through the signal conversion circuit. FIG. 4 is a block diagram showing this embodiment. The video signal is converted by the signal conversion circuit 400, integrated by the integration circuit 401, and taken out as an integrated signal.

Here, the input / output characteristics of the signal conversion circuit do not necessarily have to be shown by a straight line, and in particular, the mutual photoelectric conversion characteristics of the image pickup tube and the light receiver in the above are often expressed exponentially. Therefore, it is often desirable that the input / output characteristics be non-linear. FIG. 5 is a graph showing an example of input / output characteristics of the signal conversion circuit in such a case.
The output current is plotted on the vertical axis.

In addition, it is possible to obtain a simulation image of printing by the LATD control method by capturing an image on a color negative film and controlling the obtained video signal or the average value of the function output of the video signal to be constant. This corresponds to controlling the integrated signal in each of the above explanations so as to have a predetermined value.

The integrated signal is replaced by an analog-to-digital conversion of the video signal or the function output of the video signal, and the total numerical data obtained in one vertical scanning period or a plurality of vertical scanning periods or an amount based on the integrated value of appropriately sampled numerical data Yes, this example is included in the present invention.

Further, the integrated signal or a measurement value based on a separately measured image-transmitted light on the color negative film can be inserted into the diaphragm of the lens used for image formation in the image pickup device or the optical path.
An example in which the image pickup sensitivity is adjusted as described above while controlling the amount of light incident on the photocathode by using one or more filters, and correction information that is automatically or artificially determined as a control parameter is used to set the target. An example in which the function that defines the relationship between the sensitivity adjustment signal and the integrated signal is changed by changing the integrated value is also included in the present invention.

Also, a color simulation image under LATD control can be obtained by arranging a filter for three-color separation in front of the image pickup device and guiding the video signal of each color according to the present invention.

EFFECTS OF THE INVENTION The image pickup apparatus according to the present invention described above is capable of reproducing a simulation image of printing under the LATD control of a color printer at high speed and with a stable video signal while having high control accuracy. Since a large amount of color negative film can be continuously tested, the operator is not required to have any skill or experience, and the present invention provides an image pickup apparatus which is very effective in photographic processing. became.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an image pickup apparatus according to the present invention, and FIG. 2 is a timing chart showing the timing of each signal in this embodiment. FIG. 3 is a block diagram showing an embodiment in which a part of the control circuit is digitalized in the image pickup apparatus according to the present invention.
FIG. 5 shows a block diagram of an embodiment in which the signal is converted and then integrated, and FIG. 5 is a graph showing the input / output characteristics of the signal conversion circuit. 100, 300 ... Pickup tube 101, 301 ... Video signal amplification circuit 102, 302 ... Sync signal synthesis circuit 103, 303 ... Deflection circuit 104, 304 ... DC amplification circuit 105 ... Sample and hold circuit 106, 307 ... Integration circuit 107, 309 ... Synchronization circuit 305 ... D / A conversion circuit 306 ... A / D conversion circuit 308 ... CPU

Claims (1)

[Claims] 1. An image pickup means for outputting a video signal from an image on a color negative film while moving a horizontal scan in a vertical direction, and a video signal obtained at least during a vertical scanning period of the video signal output from the image pickup means. Calculating means for calculating an image pickup condition based on the image pickup condition, and a sensitivity adjusting means for adjusting the image pickup sensitivity of the image pickup means on the basis of the adjustment signal outputted from the calculating means, and for holding at least a vertical scanning period. An image pickup device for a color negative film, comprising: