GB2256990A

GB2256990A - Television camera automatic iris adjustable apparatus

Info

Publication number: GB2256990A
Application number: GB9206650A
Authority: GB
Inventors: Jong Phil Lee
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1991-06-19
Filing date: 1992-03-26
Publication date: 1992-12-23
Also published as: KR930000999A; KR930003305B1; DE4212515A1; JPH05167917A; GB9206650D0

Description

4') -, -, 0 -?,) J - t- AUTOMATIC IRIS ADJUSTING APPARATUS

Background of the Invention

This invention relates to an iris adjusting apparatus for automatically adjusting exposure of an object in response to the relative brightness between an object and background, and more particularly, to an iris adjusting apparatus for automatically adjusting exposure of an object, in which a photographing picture is divided into several areas so as to photograph a targeted object with optimized brightness, and thebrightness of the specific divided area is compared with a reference value for iris adjustment.

Generally, in a camera-integrated video tape recorder (camcorder) or a movie camera or the like, an iris is automati cally adjusted according to brightness of the object, A conventional image sensing apparatus such as a video camera having a function to automatically control exposure in responsE.

to a video signal obtained from the image pickup device, averages the brightness of the entire picture, that is, object.

plus background(the magnitude of the signal level). If the average value is smaller than a specific level(that is, the picture is dark), the iris opens. If the average value i,- larger than a specific level(that is, the picture is bright), the iris closes. Accordingly, the iris is adjusted in response to the average illumination density of the entire picture irrespective of the brightness of the object. That is, the conventional image sensing apparatus averages the brightness of the entire picture, and opens or closes the iriz- 1 by the iris aperture value which is determined by the average value. Thus, a conventional image sensing apparatus of this type has a drawback in that when the background is too bright in comparison with the brightness of the object, or when the sun is in a picture, the iris closes, whereby the object is photographed too dark to discriminate it.

There have been attempts to solve the above problems. For example, to determine the iris adjustment value, the brightness of the portion, excluding the upper portion of the picture, is averaged when a high luminance cloud or the sky is photographed in the upper portion of the picture, thereby solving the problem.

A method for obtaining an iris adjustment value has been proposed, in which a signal average weighting value becomes smaller with respect to the upper portion of the picture, and larger with respect to the lower portion of the picture, to thereby calculate the average value.

However, by such techniques, the brightness of the object to be photographed is not accurately detected, but is detected along with most of the background. Accordingly, when the background is relatively too bright, or the picture is in a backlight state, the object is photographed too dark. Also, when the background is relatively too dark, the iris opens to make a long exposure, with the result that the object is photographed too bright.

2 Summary of the Invention

To solve the above problems, it is an object of this invention to provide an iris adjusting apparatus for automatically adjusting exposure of an object, in which an entire picture to which an object belongs is divided into several areas in accordance with the magnitude and brightness of the object, any one area is selected according to the state of the object among the several divided areas, and brightness of the selected specific area is utilized as a variable value for iris adjustment.

It is another object of this invention to provide an iris adjusting apparatus having a backlight correction function.

To accomplish the above objects of this invention, there is provided an iris adjusting apparatus for automatically adjusting exposure of an iris in response to a video signal obtained from a charge-coupled device, which comprises means for dividing a picture of the video signal into several areas, means for designating one area among the divided areas, means for selectively outputting a video signal corresponding to the area designated by the designating means among the video signals received from the charge-coupled device, means fox comparing a brightness value of the video signal supplied frolri the output means with a previously set reference value, and means for automatically adjusting exposure of the iris in response to the compared value supplied from the comparing means.

3 Other features and operations of the preferred embodiment of the automatic iris adjusting apparatus according to this invention will be described in detail hereinafter with reference to the accompanying drawings.

Brief Description of the Drawings

FIG. 1 is a block diagram showing an automatic iris adjusting apparatus according to this invention.

FIGs. 2A, 2B and 2C are exemplary diagrams showing kinds of window pulses of the window pulse generator shown in FIG. 1 and the picture divisions corresponding thereto.

Detailed Description of the Preferred Embodiment

Referring to FIG. 1, the preferred embodiment of the automatic iris adjusting apparatus according to this inventior largely comprises an iris driving signal generating means 10, a window pulse generating means 20, and an iris adjusting means 30.

In FIG. 1, iris driving signal generating means 10 comprises a sample and hold portion 11 for sampling a video signal picked up in a charge-coupled device 1 as an image pickup device and holding the sampled video signal, a gain control portion 12 for controlling gain of the sampled-andheld video signal, a signal switching section 13 for outputting a video signal of a picture corresponding to a divided specific area among the gain controlled signal according to a window 4 pulse, a signal shaping portion 14 for shaping a waveform of the video signal of the picture corresponding to the divided specific area in response to a clamp signal and a blanking signal, and an integrator 15 for obtaining an average value of the shaped waveform signal.

Meanwhile, window pulse generating means 20 comprises a video processor 21 which processes and outputs a luminance signal of a video signal having passed through the sample and hold portion 11 after being picked up by the charge-coupled device 1, an analog to digital converter 22 which converts the luminance signal of video processor 21 into a digital signal, a picture area divider 23 which receives the digital-converted signal and divides a charge-coupled picture into several areas, a picture area selector 24 which outputs a signal of a specific area selected from the divided areas according to user's selection, and a window pulse generator 25 which generates horizontal and vertical analog window pulses corresponding to the signal of the selected specific area. Here, the user operates an external key switch(not shown) so that the picture area selector 24 outputs the signal corresponding to the picture of the specific area among the divided areas.

Iris adjusting means 30 comprises compares an iris driving signal a comparator 31 which supplied from iris driving signal generating means 10 with a reference level, thereby controlling the drive of iris adjustment motor 32 according to the output of comparator 31. Here, iris driving signal generating means 10 and iris adjusting means 30 are known technologies except that signal switching section 13 for selecting a video signal of the divided picture according to the window pulse signal of window pulse generator 25 is constituted in iris driving signal generating means 10.

Operation of the iris adjusting apparatus according to this invention will be described on the basis of the above construction.

In FIG. 1, the video signal picked up by charge-coupled device 1, is supplied to gain control portion 12 and video processor 21 via sample and hold portion 11. Video processor 21 processes the received video signal and outputs a luminance signal which represents a brightness. The luminance signal is converted into a digital signal in analog-to-digital converter 22 and supplied to picture area divider 23. Picture area divider 23 divides the digital signal into a previously set and predetermined number of areas. In this embodiment, the portion from which the upper of the entire picture is excluded is further divided into three portions. The upper portion of the picture is excluded because the background, such as the sky or a cloud having a great illumination density difference from the object, is located in the upper portion of the picture, with a result that it is difficult to accurately detect brightness of the object in the case where the background is included.

Also, in this embodiment, to divide a picture into three portions, a method of counting horizontal synchronizing pulses 6 by a duration corresponding to the divided area is adopted. As shown in FIGs. 2A, 2B and 2C, picture area divider 23 of this embodiment divides the entire picture bexcept for upper portion a of the picture, into three picture areas. Among the divided picture areas, only one area is selected by picture area selector 24 to be controlled by the userOs key input. That is, the user actuates the key input to select a desired picture area by considering the size of the object and comparing brightness of the object with that of background. In this embodiment, in accordance with the condition of the object and the background, the key input is actuated to select the entire picture area except for the upper portion of the picture as shown in FIG. 2A in the case of the normal state. Also, when the background is too bright and the object is large in size, the key input is actuated to select a divisional picture area as shown in FIG. 2B. In addition, when the background is bright and the object is small in size, the key input. is actuated to select a divisional picture area as shown in FIG. 2C.

In this embodiment, a picture is divided into three areas only when the background is normally bright with respect to the object, and the former is brighter than the latter. However, when the background is relatively dark with respect to the object, the entire picture may be minutely divided into more areas.

Meanwhile, a signal of the picture with respect to the selected specific area among three picture areas divided by 7 picture area divider 23 is supplied to window pulse generator 25. This window pulse generator 25 generates horizontal and vertical window pulses corresponding to the picture signal supplied from picture area selector 24 and supplies them to signal switching section 13. At this time, horizontal and vertical window pulses are applied to signal switching section 13 as the respective different pulses according to the size of the selected divisional picture areas(the unhatched portions), as shown in FIGs. 2A, 2B and 2C.

signal switching section 13 which receives the window pulses, receives the gain controlled video signal from gain control portion 12, and selects and outputs the video signal corresponding to the selected specific picture area according to the horizontal and vertical window pulses. That ist when window pulse generator 25 supplies horizontal and vertical window pulses to signal switching section 13, so that the large divisional picture is selected as shown in FIG. 2A, the video signal corresponding to the selected large divisional picture is selected, and when the small divisional picture is selected as shown in FIG. 2C, the video signal corresponding to the selected small divisional picture is selected.

The video signal selected by signal switching section 13 is supplied to signal shaping portion 14, shaped into a video signal of a specific level in response to clamp and blanking signals, and applied to integrator 15 which integrates it as an average value. Thus, the integrated value of integrator 15 varies according to the selected picture area of the divided 8 picture areas. The integrated value is applied to comparator 31 in iris adjusting means 30, compared with the reference level set by means of resistors RI and R2 Thereafter, the difference value compared in comparator 31 is supplied to iris adjustment motor 32 controlling the driving of motor 32, thereby opening or closing the iris.

As described above, the automatic iris adjusting apparatus according to this invention divides the picture to which the object belongs into several areas and one area of the divided areas is selected by the user in accordance with the magnitude of the object and the brightness of the background, thereby automatically adjusting exposure of the iris. For this reason, the object can be always properly photographed. Also, the automatic backlight correction function is performed.

9

Claims

1. An automatic iris adjusting apparatus forautomatically adjusting the aperture of an iris in response to video signals obtained from a charge-coupled device, said apparatus comprising:

means for dividing a picture of a video signal into several areas; means for designating one area among the divided areas; means for selectively outputting the video signal corresponding to the area designated by said designating means among the video signals received from the charge-coupled device; means for comparing a brightness value of the video signals supplied from said output means with a previously set reference value; and means for automatically adjusting exposure of the iris in response to the compared value supplied from said comparing means.

2. An automatic iris adjusting apparatus as claimed in claim 1, wherein said dividing means comprises a video processor which outputs a luminance signal representing a brightness from the video signal supplied from the charge-couple device, an analog-to-digital converter for converting the luminance signa1 supplied from said video processor into a digital signal, and a picture area divider for dividing the digital signal into a plurality of previously set areas.

3. An automatic iris adjusting apparatus as claimed in claim 2, wherein said picture area divider divides a picture into several areas by counting a horizontal synchronizing signal in said video signal.

4. An automatic iris adjusting apparatus as claimed in claim 1, wherein said picture area divider means divides a portion of one picked-up picture except for a specific area in said picture into a plurality of areas.

5. An automatic iris adjusting apparatus as claimed in claim 4, wherein said excepted portion is an upper portion of said picture.

6. An automatic iris adjusting apparatus as claimed in claim 1, wherein said designating means comprises a picture area selector for selectively outputting a signal of a divided specific area by an external input signal, and a window pulse generator which generates horizontal and vertical window pulses corresponding to the signal supplied from said picture area selector and supplies the horizontal and vertical window pulses to said selectively outputting means.

11

7. Apparatus according to any preceding claim including user operable key means for selecting the picture area.

Z.

8. Apparatus for automatically adjusting the iris of a video camera, substantially as hereinbefore described with reference to the accompanying drawings.

9. A video camera incorporating apparatus according to any preceding claim.