JPS63312779A - Diaphragm control mechanism for tv camera - Google Patents

Abstract

PURPOSE:To obtain a clear picture at all times by discriminating a brightness level of a desired picture part segmented by a picture segmentation means and using an diaphragm means so as to apply diaphragm operation in response to a discrimination signal. CONSTITUTION:A picture processing section 8 applies A/D conversion to a picture signal inputted from a TV camera 1 at an A/D conversion section 9 and a picture segmentation section 10 segments a desired picture part corresponding to a specific object by using the picture processing method for window setting on the screen. The picture segmented by the segmentation section 10 is fed to a pattern recognition processing section for number discrimination and fed to a brightness level extraction section 11. The extraction section 11 applies the density histogram generation processing in the segmented picture part and a brightness level comparison section 12 compares the density histogram characteristic value and its comparision signal is fed to a diaphragm control section 3 via a picture signal control section 13.

Description

[Detailed description of the invention] (Field of invention) The present invention relates to an aperture control mechanism for a TV camera.

(Prior art and its problems) The aperture of a conventional TV camera lens is, for example, performed by an automatic aperture adjustment mechanism (using an EE lens). Aperture adjustment by this automatic aperture adjustment mechanism converts the image signal from the TV camera into a voltage signal, and then operates the servo motor to operate the aperture so that the voltage signal level approaches the set voltage level corresponding to the set image illuminance. It is done by doing this.

However, in the case of conventional examples using such a configuration, the aperture control is performed based on the average illuminance of the entire image, so the desired subject may be located in a very dark or bright part of the image. In this case, there was a problem that a clear image of the subject could not be obtained.

This problem occurs, for example, when identifying a car's license plate in an AVI (vehicle identification) system. As shown in Figure 4, the entire image including the car body A is approximately Even if it becomes clear,
There have been cases where only the number plate 0 portion, which is the desired subject, is too bright or too dark, resulting in a lack of contrast and indistinctness.

(Object of the Invention) The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an aperture control mechanism for a TV camera that can obtain a clear image of a desired subject.

(Structure and Effects of the Invention) In order to achieve such objects, the present invention provides an aperture control mechanism for a TV camera, and an image cutout system for cutting out a desired image portion in an image signal from the TV camera. determining means for determining the brightness level of the image portion cut out by the image clipping means and outputting a determination signal thereof; aperture signal output means for outputting an aperture signal in response to the determination signal; and the aperture. and an aperture means for performing an aperture operation of the TV camera lens in response to a signal. .

According to this configuration, the determination means determines the brightness level of the desired image portion cut out by the image cutout means, and the aperture operation is performed by the aperture means in response to the aperture signal output from the aperture signal output means in response to the determination signal. It will be done.

Therefore, according to the TV camera equipped with the aperture control mechanism of the present invention, images are taken in the optimum aperture state for the desired image portion, so that the desired image is always clear, and in the AVI system, it is possible to It can be used extremely effectively for discrimination, etc.

(Description of Examples) Hereinafter, the present invention will be described in detail based on examples shown in the drawings. FIG. 1 is a simplified configuration diagram showing the aperture control mechanism of the TV camera of the present invention, in which the symbol l is, for example, C.
It is a TV camera consisting of a CD camera, and is integrally equipped with a lens 2. For example, in an AVI system, it is used to image the front of a car 21 traveling on an expressway 20 as shown in FIG. It is provided.

3 is an aperture control section of the lens 2, and the aperture control section 3 includes a detection section (aperture signal output means) 4, a control signal generation section (aperture signal output means) 5, a motor control section (aperture means) 6, and a servo motor. (Aperture means) 7. In the aperture control section 3, the detection section 4 converts the image signal input from the image processing section 8 into a voltage signal, and the control signal generation section 5 causes the level of the voltage signal from the detection section 4 to approach a set value. A control signal is given to the motor control section 6, and based on the control signal, the motor control section 6 gives a drive signal to the servo motor.

In the above configuration, the image signal from the TV camera 1 is directly input to the detection unit 4 without passing through the image processing unit 8, and the aperture control is performed in this manner.
This corresponds to an E lens.

The image processing section 8 includes an A/D conversion section 9, an image cutting section (image cutting means) 10, and a brightness level extraction section (judgment means) 1.
1, a brightness level comparison section (determination means) 12, and an image signal control section (aperture signal output means) 13. In the image processing section 8, an A/D conversion section 9
A/D converts the image signal input from the TV camera l so that it can be treated as a digital image, and the image cutting unit IO
Then, a desired image portion corresponding to a specific subject is cut out using an image processing method that is performed by setting a window on the screen.

The above-mentioned image cutting operation of the image cutting unit IO is performed only when it is determined that a desired object such as a license plate exists through a search process performed by a microcomputer based on the image signal (not shown).

The image cut out by the image cutting section 10 is sent to a pattern recognition processing section for number discrimination, and then sent to a brightness level extraction section 11. Brightness level extraction unit 11
Then, a density histogram creation process is performed on the cut out image portion, and the density histogram characteristic value is compared with a target level value in the brightness level comparison section 12, and the comparison signal is i! ! II image signal control section 13.

The image signal control section 13 is provided to attenuate and amplify the image signal provided from the TV camera 1 to the detection section 4 based on the comparison signal provided from the brightness level comparison section 12).

The density histogram processing in the luminance level extraction section 11 and the comparison processing in the luminance level comparison section 12 will be described.

Each of FIG. 3 shows a density histogram created by the brightness level extraction unit 11 in the cut out image part, in which all pixels in the cut out screen are integrated for each luminance gradation, and the distribution state of the number of integrated numbers is It shows.

The vertical axis shows the number of pixels and the horizontal axis shows the gradation. (a)
shows the case where it is too dark, (b) shows the case where it is appropriate, and (C) shows the case where it is too bright. In the density histogram obtained, the average value avr-(max
+m1n)/2 is determined, and the brightness level comparison unit 12
, this characteristic value is the target value P + at two predetermined points.
It is compared with P* and the brightness is determined under the following conditions.

■ If it is too dark avr< P + 3rd
Figure (a) ■ Proper case P, ≦avr≦P! Fig. 3 (b) ■ When it is too bright avr> P 2
FIG. 3(C) Then, a comparison signal is outputted to the detection section 4 in accordance with the determination results. This comparison signal is a signal for attenuating and amplifying the image signal. ■ If it is too dark, the attenuation command signal is used. ■ If it is appropriate, the maintenance command signal is used. ■ If it is too bright, the amplification command signal is used. Each is output.

Next, the operation of this embodiment will be explained.

For TV cameras, the shutter speed is 1/60.
When an image of a road without a car is captured in sec, the image signal is sent to the A/D converter 9 and the image signal controller 13. In this case, in the license plate search process by the microcomputer processing described above, it is determined that there is no license plate in the image, so the image cropping unit IO does not perform image cropping processing and outputs no cropped image signal. On the other hand, the image signal sent directly from the TV camera 1 to the image signal control section 13 is sent as is to the detection section 4, as there is no command signal from the brightness level comparison section 12, and the above-mentioned aperture adjustment is performed based on that signal. This aperture adjustment operation is similar to that of a conventional EE lens.

In reality, if there are no cars on the road as described above,
Also, even if there is a car, there are many cases in which the plate is not visible in the image, compared to cases in which the plate is shown in the image shown below. This is the normal basic aperture control operation for the right camera.

On the other hand, if there is a car on the road and a license plate is confirmed in the image, the image of the license plate is extracted by the image cutting unit 10 and sent to the brightness level extraction unit 11, and the brightness level is After the comparison process in the comparison section 12, an attenuation command signal is outputted to the image signal control section 13 if it is too dark, and an amplification signal signal is outputted to the image signal control section 13 if it is too bright.
The image signal control unit 13 uses T based on these command signals.
The image signal sent from the V right camera to the detection unit 4 is appropriately attenuated and amplified. Then, the calibration control operation is performed in the same manner, and in this way, an image is taken in an aperture state suitable for the plate number, and a clear image of the license plate portion is obtained.

If the configuration employs an EE lens, as in the above embodiment, the basic aperture adjustment based on normal changes in brightness over time, etc. will be performed by the EE lens mechanism, and the aperture adjustment for the desired image portion will be performed. Since the aperture adjustment is performed carefully based on the signal from the determining means, the aperture adjustment operation is performed optimally and smoothly so that a clear image of the desired image portion can be obtained even when the illuminance changes over a wide range as a whole.

In addition to the above embodiments, the present invention has a configuration in which the first/fourth aperture adjustment device for adjusting the illuminance of the entire image is manually operated, and furthermore, it does not include an aperture adjustment mechanism for adjusting the illuminance of the entire image. It can also be used as a composition.

In addition, in the above embodiment, the density histogram is used in the judgment means and the iG filtering method is adopted for the characteristic values, but other characteristics such as the weighted average value and the number of pixels at the dark and saturation levels are used to compare the characteristic values with the target level. It is also possible to compare the characteristic values using the average value of the restored images.

[Brief explanation of the drawing]

1 to 3 relate to an embodiment of the present invention, FIG. 1 is a simplified configuration diagram thereof, FIG. 2 is a perspective view of the arrangement of a TV camera, and FIGS. 3(a), (b), and (c) are density It is a histogram. FIG. 4 is a front view of a typical car image. l...TV camera, 4...detection section (aperture signal output means), 5...control signal generation section (aperture signal output means), 6
・Motor control unit (throttle means), 7... Servo motor (
aperture means), 10... image cutting section (image cutting means), ll... brightness level extraction section (determination means), 12
- Brightness level comparison section (judgment means), 13... Image signal control section (aperture signal output means) +3°

Claims (1)

[Claims] (1) A TV camera, an image cutting means for cutting out a desired image portion from an image signal from the TV camera, and a determining means for judging the brightness level of the image portion cut out by the image cutting means and outputting a judgment signal thereof. An aperture mechanism for a TV camera, comprising: an aperture signal output means for outputting an aperture signal in response to the determination signal; and an aperture means for performing an aperture operation of the TV camera lens in response to the aperture signal.