JPS647542B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a television imaging method and apparatus using a plurality of image pickup tubes. More specifically, when photographing a subject with a high contrast ratio, such as a surveillance television camera, for example, when a dimly lit area is locally illuminated with an electric light, not only the brightly illuminated area but also other dimly lit areas are captured. The present invention relates to an imaging method and apparatus for obtaining clearly visible images.

In general, so-called multi-tube television cameras that use a plurality of image pickup tubes are broadly classified into three-dimensional television cameras for obtaining stereoscopic information and color television cameras for obtaining color information.

That is, in a stereoscopic television camera, two imaging tubes are used mainly as a means for obtaining stereoscopic information for industrial use. Color television cameras are widely used for broadcasting, industrial, and educational purposes, and 2-tube, 3-tube, and 4-tube configurations have been put into practical use, but they require color information in addition to black-and-white information. In order to achieve this, especially in the case of a two-tube configuration, a color stripe image is optically formed using a color stripe filter or the like, and then black and white information and color information are separated using electrical means. In the case of three-tube and four-tube configurations, there is an image pickup tube dedicated to color information.

As described above, multi-tube television cameras have been mainly applied to stereoscopic televisions and color televisions, and have not been used much for surveillance purposes.

On the other hand, most conventional black-and-white or color single-tube TV cameras are used for surveillance, entertainment,
It is used for educational purposes and is rarely used for broadcast program production. This means that single-tube television cameras have more severe conditions than television cameras used at broadcasting stations from the standpoint of lighting technology and photographing technology. Moreover, when we consider the actual state of its operation, we find that the single-tube type has major drawbacks. For example, if a single pipe system is used for monitoring purposes and is installed outdoors,
Other optical conditions, such as extreme differences in brightness between daytime and nighttime, changes in direct and backlight due to the movement of the sun, and differences in light intensity and contrast between clear and cloudy skies, are important in relation to the subject to be monitored. is also very complex. Normally, the brightness ranges from about 5 lux to about 70,000 lux, so it is extremely difficult to install a television camera in a fixed manner for monitoring purposes and make it fully effective. For example, it is common practice to install a television camera so that it can properly monitor the indoor scene with a brightness of about 500 lux, and to make sure that the face of a person who enters with a flashlight after the lights are turned off can be clearly seen. This is an extremely natural requirement for office nighttime management. However, a single-tube television camera like the one described above does not function satisfactorily, with only the flashlight part appearing white and other parts appearing black.

Surveillance television cameras, etc., may have an automatic aperture on the lens similar to the automatic aperture mechanism found in general cameras, or an auto-target that causes the image pickup tube to self-bias. However, the effect that satisfies special conditions such as office nighttime management cannot be obtained.
Even if you manually adjust the lens and adjust the bias of the image pickup tube, it is not possible to obtain a proper image.Therefore, single-tube television cameras cannot be used as general-purpose surveillance television cameras. cannot function fully.

The present invention eliminates the drawbacks of the single-tube type television camera by making it a multi-tube type. In other words, the amount of incident light from the subject is divided into appropriate ratios by a half mirror, and supplied to the imaging section that handles the dark region and the imaging tube that handles the bright region, and then to the imaging tube that handles the dark region. The input signal is clipped at a predetermined value to emphasize the dark area, and the signal input to the image pickup tube that handles the bright area is lowered in signal level to include the bright area. By mixing these signals, an image with clear details in both bright and dark areas can be obtained.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 1, 1 is a subject and 2 is an objective lens. A half mirror 3 is provided on the optical axis of the objective lens 2, and an image pickup tube 4 as a first image pickup section is provided on the optical axis of the half mirror 3. An optical image is formed. Further, a total reflection mirror 6 is installed on the reflection optical axis of the half mirror 3, and an image pickup tube 7 as a second image pickup section is installed on the reflection optical axis. An optical image is formed.

When the transmittance of the half mirror 3 is sufficiently over 50%, such as when the transmittance is 95%, the first image pickup tube 4 is used for dark areas, and the second image pickup tube 7 is used for bright areas. As a result, the contrast range in the subject 1 is divided into two parts. In this case, a light amount adjustment filter 9 may be provided on the optical axis of the total reflection mirror 6 and the second image pickup tube.

Next, the first image pickup tube 4 includes an amplifier 10,
It is connected to a mixer 12 via a white clipper 11, and the second image pickup tube 7 is directly connected to the mixer 12 via an amplifier 13. This mixer 12 is connected to a synchronizing signal generator 15 together with a synchronizing signal generating circuit 14, and is further connected to an output terminal 16.

Next, the operation of this circuit will be explained.

First, let us consider an object 1 having different reflectance in a band shape as shown in FIG. 2b. Note that the numbers indicate reflectance, where 0 is black with a reflectance of 0%, and 100 is white with a reflectance of 100%. When the gamma (Γ when e ₀ = e ₀ ) is approximately 1, the video signal 17 obtained by imaging the subject 1 with an ideal device has a staircase waveform as shown in Figure 2a. Assume that there is.
When the subject 1 opens and closes the lens aperture in this manner, the video signal waveform amplitude increases or decreases when the image pickup tube bias is a fixed bias. However, in the case of automatic target bias, the waveform amplitude hardly changes unless the subject changes within the range where the lens aperture is opened beyond a certain value.

Next, in FIG. 1, the first image pickup tube 4 is used for dark areas and has a fixed bias, the second image pickup tube 7 is used for bright areas and has an auto target bias, and a lens without an aperture is used. use

Then, the light beam from the subject 1 passes through the objective lens 2 and reaches the half mirror 3. If the transmittance of this half mirror 3 is, for example, 95%, 95% of the transmitted light is sent to the first image pickup tube 4, and the remaining 5% of the reflected light is sent to the total reflection mirror 6, and further to the filter 9 as necessary.
is sent to the second image pickup tube 7 through the camera. As shown in FIG. 3b, the beam current of the first image pickup tube 4 is set so that the portion exceeding the input light amount 18 set by the fixed bias is removed as a saturated region. Only the signal of 1 is extracted with emphasis.

In addition, the remaining 5% that entered the second image pickup tube 7
The input light intensity is adjusted by auto target bias,
FIG. 3c includes a bright area to a dark area that is approximately proportional to the amount of light input to the second image pickup tube 7.
The signal waveform shown in is obtained.

In other words, the first and second image pickup tubes 4 and 7 have
Instead of obtaining an output waveform as shown in FIG. 3a, which is obtained by amplifying the signal waveform 17 of the subject 1 as shown in FIG.
As shown in Figure 3b, the bright area is cut out and the information in the dark area is emphasized to a sufficient amplitude. is small, but information in the bright region can be obtained with sufficient amplification. In other words, for the first image pickup tube 4 for dark areas, it is approximately equivalent to opening the lens aperture, and for the second image pickup tube 7 for bright areas, it is equivalent to fully closing the lens aperture. Since they are almost equivalent,
A good S/N ratio can be ensured for any output signal. Then, the transmittance of half mirror 3 is
If the reflectance is 90% or more and the reflectance is 10% or less, it will cover a sufficient light amount range as a surveillance television camera.

Next, the signal outputs of the first and second image pickup tubes 4 and 7 are amplified by amplifiers 10 and 13, respectively. Among these, the amplified dark part signal of one of the amplifiers 10 does not require information above a certain level as a signal amplitude, so the white clipper 10
1 clips the white information above a certain level, and the clipped information and the output information of the other amplifier 13 are subjected to simple addition or arithmetic averaging in the mixer 12. That is, the optimal level signal of the dark area where the white information is clipped as shown in FIG. 3b and the optimal level signal of the bright area as shown in FIG. Obtain a signal with an output waveform as shown in Figure 3d. As can be seen from this output waveform, although the contrast differs from the actual output waveform, sufficient information is obtained for both the dark region and the bright region.

This output signal further includes a synchronization signal generator 1.
A synchronizing signal 19 from 4 is added by a mixer 15, and sent as a composite video signal from an output terminal 16 to an external connection device such as a television receiver.

Next, FIG. 4 shows another embodiment of the three-tube type. In this example, the first, second, and third image pickup tubes 4, 7a, and 7b are used for dark areas and indoor bright areas, respectively. , which functions for use in bright outdoor areas. Therefore, for example, the first half mirror 3 transmits 75% of the amount of light that enters from the subject 1 through the objective lens 2, and 2
The second half mirror 6a transmits 20% of the light amount (medium light amount), and the last total reflection mirror 6b transmits 50% of the light amount.
% light amount (small light amount) transmitted. These obtain outputs at predetermined levels from the first, second, and third image pickup tubes 4, 7a, and 7b, and further, the amplifiers 10,
It is amplified by 13a and 13b. The dark area output of the first image pickup tube 4 is adjusted to the white clipper 1 as necessary.
It is clipped at 1 and added at mixer 12. That is, assuming that the amount of incident light is as shown by the solid line in a in FIG. 5, 75% of the total amount of light is incident on the first image pickup tube 4, and A fixed bias 20 is set for the signal so that the indoor bright area and the outdoor bright area are cut off, as shown in FIG. Therefore, there is no information on the indoor bright area and the outdoor bright area, and good information only on the dark area is emphasized and output. Next, since 20% of the total amount of light is incident on the second image pickup tube 7a, in this second image pickup tube 7a,
By setting the fixed bias 21 as shown in FIG. 5c, high level information corresponding to the outdoor bright region is saturated and clipped and output. At this time, information from the dark region is output at a considerably low level. Therefore, only information from the indoor bright region is output at a good level. Furthermore, since the third image pickup tube 7b is set to auto-target bias, it outputs signals covering the entire area of 5% of the total amount of incident light. That is, information from the outdoor bright region is output at a good level. At this time, both the information from the dark area and the information from the indoor bright area are output, but at extremely low levels.

When these three output signals are mixed in the mixer 12, the characteristics shown by the dotted line in FIG. 5a are obtained.
That is, in the dark area, among the information of the first, second, and third image pickup tubes 4, 7a, and 7b, the information of the first image pickup tube 4 is particularly emphasized and output, and in the indoor bright area, the information of the first image pickup tube 4 is outputted with emphasis. Since the information of the second and third image pickup tubes 7a and 7b is clipped, the information of the second and third image pickup tubes 7a and 7b is
In particular, the information from the second image pickup tube 7a is emphasized and output, and the bright area is further output from the first and second image pickup tubes 4 and 7.
Since the information of the third image pickup tube 7b is both in a clipped state, the information of the third image pickup tube 7b is emphasized and output. In this way, in the image obtained by adding and synthesizing the three signals, the information of each part of the dark part, middle bright part, and bright part clearly appears. In the above description, the level of the signal output in the bright area of the second image pickup tube 7a may be further adjusted using a white clipper, as in the case of the first image pickup tube 4. In addition to the output signal synthesized as described above, the synchronization signal 1
9 is added to obtain an output from the output terminal 16.

With this configuration, it is possible to clearly obtain all information such as the brightest part outdoors, the second brightest part indoors, and other dark parts such that the contrast is divided into three levels. The same applies to the case of four or more tubes.

In the embodiments shown in FIGS. 1 and 4, the reflected light beams from the half mirrors 3 and 6a are further reflected by the total reflection mirrors 6 and 6b to form images on the mirrors 7 and 7b. However, the reflected light beams from the half mirrors 3 and 6a may be directly imaged by the image pickup tubes 7 and 7b without being reflected by the total reflection mirror.

In the embodiment described above, only contrast was considered a problem. However, depending on the subject, such as for monitoring the inside of a furnace, hue as well as contrast may be an issue. In such a case, the half mirrors 3 and 6a are adjusted according to the spectrum of the luminescent object.
Alternatively, the light amount adjustment filters 9, 9a, and 9b may have spectral characteristics.

In the embodiments described above, the case where an image pickup tube was used as the image pickup section was explained. But this CCD
(Charge Coupled Devise) and BBD (Bucket
It is also possible to use a solid-state image sensing device such as a solid-state imaging device (Brigade Device).

Although not shown in the drawings, a gamma circuit or the like may be inserted at the process stage in order to compensate for the characteristics of the image pickup tube or the characteristics of the composite video signal.

In the present invention, as described above, an imaging section for bright areas and an imaging section for dark areas are provided, corresponding to the brightness level of the subject and the spectrum to be identified, and their signal outputs are mixed. Therefore, what is noteworthy is that it has a good S/N ratio that allows even a portion of the incident light to be taken in without being reflected, allowing discrimination of all gradations from bright to dark areas of a subject with a high contrast ratio. It is used to obtain images, and has extremely excellent characteristics that are completely different from the conventional system where you only have to choose between viewing bright areas or dark areas. Further, since the signal is not replaced with another signal in the threshold state, so-called blacking out or whitening phenomenon does not occur in the image. Furthermore, since the level of bright areas is not simply lowered, the contrast between bright areas and dark areas will not be reversed. Furthermore, if a plurality of image pickup tubes, half mirrors, and other circuits are housed in the same housing like a single color camera, it is particularly effective as a surveillance camera.

As described above, the present invention has been explained with reference to various embodiments. However, the present invention is not limited to these examples unless the gist of the invention is changed.
The invention also extends to other embodiments.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a television imaging device according to the present invention, and FIGS. 2a and 2b are
Signal waveform diagram and front view of the subject, Figure 3 a, b,
c, d are signal waveform diagrams of each part in the example shown in FIG. 1, FIG. 4 is a block diagram of another embodiment of the present invention, and FIG. It is a signal waveform diagram of each part. 1...Subject, 2...Objective lens, 3, 6a...
...Half mirror, 4, 7, 7a, 7b... Image pickup tube, 5, 8... Photoconductive surface, 6, 6b... Total reflection mirror, 9, 9a, 9b... Filter, 10, 1
3, 13a, 13b...Amplifier, 12, 15...
Mixer, 14... Synchronization signal generator, 16... Output terminal, 17... Signal waveform, 18, 20, 21...
Fixed bias, 19... synchronization signal.

Claims (1)

[Scope of Claims] 1. The amount of incident light from the subject is divided into two at a predetermined ratio, and the light is received by a dark region imaging section and a bright region imaging section, respectively, and the light is received from one of the dark region imaging sections. For the signal output from the other imaging section, the white signal above a certain level is clipped to obtain a signal that emphasizes the dark region, and for the signal output from the other bright region imaging section, the bright region is obtained by lowering the image signal level. A television imaging method in which a video signal is obtained by obtaining a signal including a dark area, and mixing a signal that emphasizes the dark area with a signal including a bright area whose signal level is lowered. 2. In order to emphasize the signal in the dark area, increase the ratio of the amount of light incident on the image pickup unit for the dark area from the subject,
2. The television imaging method according to claim 1, wherein the ratio of the amount of light incident on the bright region imaging section from the subject is reduced in order to lower the signal level in the bright region. 3. In order to emphasize the signal in the dark region and lower the signal level in the bright region, the amplification degree of the output of the imaging section for the dark region and the output of the imaging section for the bright region are adjusted. The television imaging method according to scope 1. 4. One half mirror that divides the incident light amount from the subject into a light amount that sufficiently exceeds 50% and the remaining light amount, a dark area imaging section that forms an image using light that sufficiently exceeds 50% of this half mirror, and the above-mentioned. an imaging unit for bright areas that forms an image using the remaining light of the half mirror;
a white clipper that clips a white signal of a certain level or higher from among the signal outputs of the image pickup unit for dark areas; an output from the white clipper that emphasizes the dark areas and cuts out the bright areas; and the image pickup unit for bright areas; 1. A television imaging device comprising: a mixing section that lowers the level of an image signal from a 3D image signal and mixes the image signal level with an output including a bright area, and obtains the output of the mixing section as a video output. 5. The television imaging device according to claim 4, wherein the imaging section comprises an image pickup tube or a solid-state image sensor. 6. The television imaging device according to claim 4, comprising a light amount adjustment filter in the front part of the bright section imaging section. 7. The television imaging device according to claim 4, wherein the half mirror and/or the light intensity adjustment filter have spectral characteristics according to the emission spectrum of the subject. 8. The television imaging device according to claim 4, wherein after mixing the signal output of the image pickup section for dark areas and the signal output of the image pickup section for bright areas, a synchronization signal is added by a mixer. 9. The television imaging device according to claim 4, wherein a gamma circuit is inserted to compensate for the characteristics of the imaging section or the composite video signal. 10 First and second half mirrors that divide the amount of incident light from the subject into three stages: large, medium, and small, and the optical axis on the high light amount axis divided by these first and second half mirrors. There is an imaging section for dark areas that white-clips areas other than dark areas and outputs only the signals of the dark areas, and an imaging unit for dark areas that white-clips the outside bright areas and outputs only the signal of the dark areas. an image pickup unit for indoor bright areas that outputs a signal of 1; an image pickup unit for outdoor bright areas that is installed on the low light intensity axis and outputs the entire area including the outdoor bright area at a low level; 1. A television imaging device comprising a mixing section that mixes signals from a bright section imaging section and an outdoor bright section imaging section.