JPS60251779A - Video camera device - Google Patents

Abstract

PURPOSE:To reproduce details of a high light section and a shadow section by allowing an incident luminous amount switching means to switch the attenuation mode of the incident luminous amount to a photoelectric converting section of an image pickup meand and allowing an incident luminous amount adjusting means to bring a video signal to a prescribed level. CONSTITUTION:The aperture of a diaphragm 2 at the back of an image pickup lens 1 is controlled by a drive motor 2A. An image pickup tube is provided at the back of the diaphragm 2 and an object image is formed on a photoelectric converting section 3A. A luminance signal is extracted from an output video signal OUT by an LPF8, fed to a diaphragm drive circuit 10 via a mean value detecting circuit 9 and the motor 2A controls the aperture of the diaphragm. An incident luminous amount switching means 200 consists of a sawtooth wave generating circuit 14 receiving a signal V from a synchronizing signal generating circuit 4, a phase comparator circuit 15 receiving an output of a sampling pulse generating circuit 16 triggered by the output of the circuit 14 and a rotation detecting section 13 and a rotating disc 11 receiving an output of the circuit 15 and switching the incident luminous amount driven by the motor 12 via a current amplifier circuit 17.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a video camera device, and particularly to a video camera device suitable for imaging a subject with high contrast.

(Prior Art) Generally, in order to image a subject in a video camera device, an image tube and a CCD image sensor are used.

Imaging means such as MO8O8-like elements+ and SPD imaging elements are widely used. In such m18 means, there is generally a relationship as shown in FIG. 1 between the amount of incident light at the photoelectric conversion section and the photoelectric conversion output.

That is, during the initial period when the amount of incident light reaches a certain amount of incident light from 0 to a certain amount of incident light (0), a small photoelectric conversion output of a substantially constant level is generated based on the dark current, and from this amount of incident light (o) to a predetermined amount of incident light (2), During the photovoltaic period, the photoelectric conversion output increases as the amount of incident light increases.

When the incident scene has a light intensity of 1 or more, the photoelectric conversion output becomes saturated.

Therefore, in a conventional video camera device, an incident light adjusting means, for example, an aperture adjustment is performed so that the amount of light incident on the imaging means is between light tIo and (1).

In this way, high-quality imaging can be performed for normal subjects without causing problems with separate equipment. However, if the contrast in the subject is very high, for example, as shown in Figure 2, sunlight may be shining directly on the subject.
When photographing a part of a backlit tree on imaging screen A, one horizontal scanning line forms screen A! As shown in Fig. 3, the video signal corresponding to the highlight part (high brightness part) AI should ideally be as shown by the broken line W, which would be the photoelectric conversion output as described above. Ideally, the video signal corresponding to the shadow part (low brightness part) A2 becomes a white level due to the saturation characteristics of the dotted line BVc.
The area as shown becomes the black level due to the dark current characteristics of the photoelectric conversion output as described above. Therefore, an image obtained by recording and reproducing a video signal of 5 as shown in FIG. 3 is formed only of highlight portions where details are not reproduced and shadow portions where details are not reproduced, resulting in extremely poor image quality.

In order to improve this and reproduce the details of the highlight part of the subject, the amount of light incident on the photographing means can be adjusted by adjusting the aperture or N.
It is also possible to use a D filter or the like to attenuate the image further than the normal amount, but in this way, the details in the highlights will be reproduced, but the details in the shadows will not be reproduced, causing so-called crushed blacks. You can only get a clear image.

In addition, if the amount of light incident on the imaging device is increased further than the normal amount in order to reproduce the details of a part of the shadow of the subject, the details of part of the shadow will be reproduced, but the details of the dark and illumination parts will be reproduced. Therefore, only a video signal corresponding to an image with so-called whitewashing can be obtained.

When capturing a high-contrast subject with a conventional video camera device, it is important to choose between reproducing details in the /'t 2nd part of the screen and reproducing details in the shadow part based on the importance of the image. , there is a problem that only images can be obtained at the expense of others.

(Objective) The object of the present invention is to solve the above-mentioned problems and to provide a video camera device capable of reproducing both the details of the light and shadow parts of an image with very high contrast, such as in backlit photography. Our goal is to provide the following.

(Summary) The video camera device according to the present invention includes an incident light amount switching means and an incident light amount adjusting means, and the incident light amount switching means attenuates the amount of incident light to the photoelectric conversion section of the imaging means every 1 field or every 17 days. The input light intensity adjustment means adjusts the incident light intensity so that the video signal reaches a predetermined level.
This method is characterized by controlling t.

(Example) Hereinafter, the present invention will be explained based on illustrated embodiments.

In FIG. 4, an iris (diaphragm) 2 is disposed behind the imaging lens 1, and the aperture diameter of the iris 2 is controlled by two drive motors. An imaging tube 6, which is an imaging means, is arranged behind the iris 2.
A subject image is now formed on the photoelectric conversion section 3A of the image pickup tube 3. The image pickup tube 3 causes the electron beam to perform horizontal and vertical scanning based on a horizontal synchronizing signal H and a vertical synchronizing signal V from a synchronizing signal generating circuit 4. It is designed to perform vertical scanning. In addition, the photoelectric conversion section 3A
The photoelectric conversion output corresponding to the subject image generated in ' is current-amplified by a preamplifier 6 and supplied to an NTSC color video processor 7. This supplied signal is
The video processor 7 converts the signal into an NTSC color video signal based on the horizontal synchronizing signal H and vertical synchronizing signal V from the synchronizing signal generating circuit 4. The video signal thus created is sent as an output video signal OUT from an output terminal to an external device (not shown), such as a video tape recorder. Further, from this output video signal OUT, a luminance signal is extracted by a four-pass filter 8, and a luminance signal is extracted by a resistor 9.
A. Capacitor 9B.

The average level is detected by a well-known average value detection circuit 9 formed by a resistor 9C. This detected average level signal is supplied to the iris drive circuit 10, and the aperture diameter of the iris 2 is controlled by the motor 2A. This control is a negative feedback loop control that controls the output level of the average value detection circuit 9, in other words, the amount of light incident on the photoelectric conversion section 6A to a predetermined value.

Further, the imaging device 100 having such a configuration and operation is well known.

The video camera device according to the present invention is provided with incident light amount switching means 200 for switching the amount of light incident on the photoelectric conversion section 3A of the imaging means. That is, in the photographing optical path between the imaging lens 1 and the iris 2, as shown in detail in FIG. As shown in FIG. 4, is arranged so as to block the photographing optical path to the photoelectric conversion surface 3A,
A motor 12 is connected to the center of this rotating disk 11.

Further, a rotation detecting section 13 is disposed near the rotating disk 11 to detect the position of the force at the boundary 11C (see the fifth section) between the transparent plate 11A and the light attenuating plate 11B. The transparent plate 11A is made of a transparent optical glass plate, and the light reduction plate 11B is made of a material that has the same refractive index and thickness as the transparent plate 11A, but differs only in light transmittance.

Further, the vertical synchronization signal V from the synchronization signal generation circuit 4 is supplied to the sawtooth wave generation circuit 14,
The output terminal of the circuit 14 is connected to one comparison input terminal of a phase comparison circuit 15. The other comparison input terminal of the in-phase comparison circuit 15 is connected to the output terminal of a sampling pulse generation circuit 16 that is triggered by the output of the rotation detection section 15. The output end of this phase comparison circuit 15 is connected to the motor 12 via a current amplification circuit 17.

The video camera device of this embodiment includes the incident light amount switching means 200 configured as described above. below,
The operation will be explained using waveforms in FIGS. 6 and 7 and FIG. 11.

The sawtooth wave generation circuit 14 is triggered by the L level pulse in the vertical synchronization signal V from the synchronization signal generation circuit 4, and a sawtooth wave signal a is generated. is supplied to one input end of the
The sampling pulse generation circuit 16 is triggered by the H level pulse of the signal generated in the rotation detection unit 13 when the boundary portion 11C of the rotation disc 11 is detected by the rotation detection unit 13, and the sampling pulse generation circuit 16 is A sampling pulse C serving as an H level pulse is supplied to the other input terminal of the phase comparison circuit 15. The output of the in-phase comparison circuit 15, that is, the sampling hold voltage SR becomes a voltage proportional to the phase difference between the sawtooth wave signal a and the sampling pulse C. This sampling hold voltage SH is supplied to a current amplification circuit 17, where the current is amplified to a predetermined value and drives the motor 12. As a result, the rotating disk 11 rotates at a rotation speed of 3Q rps in phase synchronization with the vertical synchronizing signal VK. Rotating disk 110 at this time
Although the rotational phase can be arbitrarily varied depending on the mounting position of the rotation detecting section 15, in this embodiment, the boundary portion 11C of the rotating disk 11 coincides with the vertical blanking period.

In the field high attenuation mode in which the light attenuation plate 11B of the rotating disk 11 operating in this manner is located on the photographing optical path behind the imaging lens 1, a high-contrast photographic mountain pass screen as shown in FIG. 2, for example, is produced. In the case of A, the video signal level corresponding to the bright areas A, , A of the same screen A becomes the gray level, and the video signal level corresponding to the shadow (JA2 becomes the black level. Therefore, the highlight area A
A video signal 0UT1 as shown in FIG. 7 is obtained in which only the dials of , , A are reproduced. At this time, the iris 2 is controlled so that the level of the output video signal OUT becomes the average level detected by the average value detection circuit 9.

In addition, in the low attenuation mode of the field in which the transparent plate 11A of the rotating disk 11 is located on the imaging optical path behind the imaging lens 1, for example, in the case of a high contrast imaging screen A as shown in FIG. is the highlight part A of the same screen A
,, the video signal level corresponding to Al becomes the white level,
The video signal level corresponding to the shadow portion A2 becomes the gray level. Therefore, a video signal 0UT2 as shown in FIG. 7 is obtained in which the details of only the shadow part A2 are reproduced.

At this time, the iris 2 receives the video signal 0UT as described above.
2 is controlled to be at a half-average level.

And, the level of the image 1 low signal in the above-mentioned high attenuation mode and the level of the image 1 low signal in the high attenuation mode! The signal levels are approximately the same. Therefore, a field in which details in the highlight portion are reproduced and a field in which details in a portion of the shadow portion are reproduced are alternately repeated.

Further, in the above embodiment, the high attenuation mode and the low attenuation mode are switched for each field of the video signal, but it is also possible to reduce the number of rotations of the rotating disk 11 by half and switch the mode for each frame of the video signal. good. In this case, some 7 ritzker will be noticeable.

Next, another embodiment of the present invention will be described using FIG.

The electrical circuit of this embodiment is basically the electrical circuit shown in FIG. 4 with an additional electrical circuit 500 added thereto. That is,
Unlike the color video processor 7 (see FIG. 4), the color video processor 7A has a function of adding a horizontal synchronizing signal H and a vertical synchronizing signal V. It is connected to the input end of an NTSC encoder/coder 7B having a function of adding horizontal and vertical synchronizing signals H and V, and output video signals OU and T are sent out from the output end of the encoder 7B. Further, the output terminal of the low-pass filter 8 is connected to the input terminal of the field selection circuit 19.
The output terminal of 9 is connected to the comparison input terminal of the comparator 20. The field selection circuit 19 is a type of switch circuit, and is turned on and off for each field by the output signal d of the field discrimination circuit 22 to which the vertical synchronizing signal V is supplied.
It is controlled off. Comparator 2 above
A voltage obtained by converting the voltage of the terminal to which the positive voltage Vcc is supplied to the optimum reference voltage using a variable resistor of 2 OA is applied to the zero reference voltage application terminal. The output terminal of the comparator 20 is connected to the control terminal of the analog switch 1B via a delay circuit 21 having a delay time of one field time.

The operation of this embodiment depicted in this way will be explained using FIG. 9.

The luminance signal obtained at the output end of the low-pass filter 8 is the 9th
As shown in the signal e shown in the figure, the video signal e1 in which the details of the highlight part are reproduced and the video signal e2 in which the details of the shadow part are reproduced alternately for each field. . After passing through the path 19, the video signal e is extracted from the signal e and becomes the signal f. This signal f is compared with the reference level voltage REF by the comparator 2o, and when the signal f exceeds the reference level voltage REF, the output of the comparator 20 becomes the KL level as shown by the signal g. This signal g is delayed by one field time by the delay circuit 21 and becomes a signal. This signal is supplied to the control end of the analog switch 18, and the analog switch 18 is activated by the H level pulse of the signal, and a signal corresponding to a portion of the shadow of the video signal e2 in the signal e is extracted. A signal i is obtained from which the signal corresponding to the highlight portion of the video signal e2 is removed. As a result, the signal corresponding to the highlight part of the video signal e1 in the high attenuation mode and the signal corresponding to the highlight part of the video signal e2 in the low attenuation mode do not overlap, and are synthesized with good image quality. be done. According to this embodiment, a video signal is obtained in which a signal at a substantially white level corresponding to a highlight portion, which is included in the video signal in the low attenuation mode, is removed, so that it is finally recorded and reproduced. Image quality can be improved.

It goes without saying that the iris 2 used in the above embodiments may be replaced by a liquid crystal whose transmitted light amount is variable, a physical aperture, or the like.

Moreover, instead of the rotating disk 11 used in the incident light switching means in each of the above embodiments, a thin light shielding plate having arc-shaped notches 30A and 50B at symmetrical positions can be used, for example, as shown in FIG. The first rotating shutter 30 is made of a sexual disc.
The same shutter 30 and the second rotary shutter 1 of the same shape are mounted so that they overlap in a co-moving manner, and the above-mentioned notch 30 is
A, the first slit is formed by the overlapping angle of 31A, and the second slit is formed by the overlapping angle of the notch, 3[]B, 31B.
A neutral density filter may be attached to one of both slits. In this case, the first and second rotations are performed at 180 Orpm so that the first slit exposes the photoelectric conversion section 3A of the camera tube 5 and the second slit exposes the photoelectric conversion section 3A for each field of the video signal. It is necessary to rotate the shutters 30, 31 synchronously.

Further, by varying the opening angles of the first slit and the second slit for each field of the image signal, the amount of light incident on the photoelectric conversion section 5A can be switched for each field as described above.

Furthermore, the above-mentioned rotating disk 11 is used as the incident light switching means.
Instead of using the first and second rotary shutters 30 and 31, a liquid crystal, a physical aperture, or the like that changes the amount of transmitted light may be used, and the amount of transmitted light may be switched for each field of the video signal.

By the way, if you move the above incident light amount switching means out of the optical path of the image, you can use it as a conventional video camera. In order to prevent this change, it is desirable to insert a transparent plate optically the same as the afterglow filter used in the incident light amount switching means into the imaging optical path.

(Effects of the Invention) As described above, according to the present invention, it is possible to obtain a video signal that reproduces both the details of the highlight part and the detail of the shadow part even during high contrast shooting such as backlight shooting, and as a result, This has the effect of allowing high-quality recording and reproduction.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram showing the relationship between the amount of incident light and the photoelectric conversion output in the imaging means, and Figure 2 is a schematic diagram of the subject to explain the contrast state of the image taken during backlight photography. Figure 3 is the above-mentioned second figure.
FIG. 4 is an electric circuit diagram of a video camera device showing an embodiment of the present invention. FIG. 6 and 7 are a front view showing the details of the rotating disk shown in FIG. FIG. 9 is a waveform diagram for explaining the operation of the circuit shown in FIG. 8, and FIG. FIG. 7 is an exploded perspective view showing another example of the light amount switching means. View 1 Ward 2 map

Claims (2)

[Claims] (1) an incident light amount switching means that switches the attenuation of the amount of incident light to the photoelectric conversion section of the imaging means alternately between a high attenuation mode and a low attenuation mode for each field or frame of the video signal; and an incident light amount adjusting means for controlling the amount of light incident on the photoelectric conversion unit so that each video signal in the high attenuation mode and the low attenuation mode obtained by the imaging means is at a predetermined level. Features video camera equipment. (2) The video camera device according to claim 1, wherein a white level portion of a video signal obtained by the imaging means in a low attenuation mode is removed.