JPS60232783A - Auto-iris device of video camera - Google Patents

Abstract

PURPOSE:To prevent an image pickup tube from burning by outputting a focusing signal when the inclination of a simpled video signal exceeds a prescribed value, and on the basis of the signal, executing automatic focusing and iris control. CONSTITUTION:A CPU5 calculates luminance distribution on the basis of a video signal written in a memory 8 and compares the inclination of the luminance distribution with a prescribed value to detect a sharp changing point exceeding the prescribed value. When the CPU5 detects the most sharp changing point, the changing point is judged as a fucusing position, a focusing signal F is outputted from the CPU5 and a motor stopping signal is outputted from a motor control circuit 9 on the basis of the focusing signal F to stop a motor 10 for moving a focus lens 1a. When focusing is impossible on a range finding line fixed on one scanning line, a range finding line setting signal is changed to move the range finding line up and down in the vertical direction and a start position specifying signal S3 outputted from the CPU5 is changed to move a range finding area in the horizontal direction and execute focusing operation.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to an auto-iris device for a video camera that can perform appropriate iris control.

(b) Prior art The automatic aperture control of conventional video cameras uses the average or peak value of video signals from image pickup devices such as image pickup tubes and solid-state image sensors to keep the image plane illuminance constant through a servo system. I am doing it.

With this method, if there is a part of the background in the screen that is brighter than the subject, the subject image will be difficult to see due to insufficient light, and conversely, if the subject is brightly lit, the subject will appear white. It happens.

Therefore, as a method to solve this problem, the so-called center-weighted metering method uses wide blanking pulses to extract only the signal in the center of the screen, and the shortcomings of this method are further improved and distance metering is applied to a part of the screen. An automatic video signal aperture circuit has been proposed in which the IJ is weighted more than other parts (Japanese Patent Laid-Open No. 11489/1989). As another method.

A method has been proposed in which the brightness detection area of the subject is selected at an arbitrary position, size, and shape on the screen (Japanese Patent Laid-Open No. 58-16
217゛No. 0).

However, in the above conventional method.

Outside photometering area for automatic aperture adjustment If an extremely bright area such as the sun or a light source enters the camera, automatic aperture adjustment will not work and image capture tube burn-in may occur.

(c) Purpose and structure of the invention The present invention has been made in view of the above points, and an object thereof is to prevent image pickup tube burn-in by performing appropriate iris control in a video camera that performs automatic focus adjustment. In order to achieve this purpose, the video signal that constitutes one screen output from the video camera is sampled along a predetermined ranging area on the screen, and the slope of the luminance signal of the sampled video signal is set to a predetermined value. When the focus position is exceeded, the in-focus position is output, and based on this in-focus signal, automatic focus adjustment is performed and iris control is performed.

) Example The present invention will be explained below with reference to the drawings.

FIG. 1 shows a block diagram of one embodiment of a video camera having an auto-iris device according to the invention. This embodiment has an autofocus mechanism built in.
is a lens system having a focus lens 1a and an iris 1b.

2 is an image pickup tube, 3 is a camera circuit that processes the video signal output from the image pickup tube 2, and 4 is an autofocus operation and an auto iris based on the synchronization signal and horizontal transfer pulses generated by the camera circuit 3 and various signals from the CPU 5. 6 is an A/D converter that digitally converts the video signal S output from the camera circuit 3; 7 is a peak value detection circuit that detects the peak value of the video signal S; 8 is an A/D converter that controls the timing of the operation; A memory 9 stores a video signal on a specified distance measurement line from the D-converted video signal S, and 9 drives and stops the focus lens drive motor 10 based on the result of the CPU 5 determining the slope of the brightness level of the video signal. Reference numeral 11 is a focus lens drive gear, and when this gear 11 rotates, the rack 12 moves in the direction of the arrow, so the focus lens la attached to it moves left and right. Further, 13 is a motor control circuit that controls driving of the iris drive motor 14 based on the brightness level of the video signal by the CPU 5.

Next, before explaining the auto-iris control operation according to the present invention, the auto-focus operation will be explained based on the flowchart of FIG. First, using the video signal stored in the memory 8, the CPU 5 examines the slope of the change in brightness level (
F-1) Next, determine whether the slope exceeds a predetermined value and is steep. If not, determine whether or not you are going over a steep slope (F-
4'). As a result, if the frame is becoming steeper than the previous frame, it is assumed that the frame is approaching the in-focus position, and the motor IO continues to rotate (F-5); otherwise, it is assumed that the frame is moving away from the in-focus position, and the motor 10 is reversed. (F-6).

FIG. 3 shows an example of the timing controller shown in FIG. 1, and is an example in which focusing is determined using a distance measurement line set on one scanning line as shown in FIG. 4 (A). .

The timing controller 4 (shown surrounded by a broken line) includes a counter 41 that receives a horizontal synchronization signal H5 and a vertical synchronization signal vS from the camera circuit 3 and a ranging line setting signal S1 from the CPU 5.

An AND circuit 42 calculates the AND of the horizontal synchronization signal E (S) and the output S2 of the counter 41, the output of the AND circuit 42, the horizontal transfer pulse HTP from the camera circuit 3, and the ranging start position designation signal s3 from the CPU 5. a counter 43 which outputs a ranging line signal S4 in response to the received signal, and a horizontal transfer pulse H.
It is comprised of an AND circuit 44 which takes the logical product of TP and the distance measurement line signal S4 from the counter 43, and a write timing circuit 45 which instructs writing of the video signal into the memory 8 and outputs a write address. The horizontal transfer pulse HTP is generated by the synchronization signal generation circuit of the camera circuit 3.

Next, the circuit operation will be explained.

Figure 5 (A) and C) are partially enlarged views of Figure 4 (A) and (B), and Figure 5 (A) corresponds to the embodiment shown in Figure 3. .

The counter 41 is reset every vertical synchronization signal vS and starts counting the horizontal synchronization signal H3.

When the count value of the counter 41 matches the ranging line setting signal Sl inputted from the CPU 5, a matching signal S2 is outputted from the counter 4I. The distance measurement line setting signal Sl is a signal for setting the scanning line number (for example, n) that defines the distance measurement line in order to specify the distance measurement line.By changing this signal Sl, the distance measurement line can be moved vertically on the screen. Can be moved. When the match signal S2 is output from the counter 41, the AND condition is established by the horizontal synchronizing signal H3n that is output at the start of scanning of the scanning line that defines this distance measurement line, and the counter 43 is set and counts the horizontal transfer pulse HTP. Begin to. On the other hand, the counter 43 has C
Since the start position designation signal S3 (for example, from the m-th horizontal transfer pulse) that designates the start position of distance measurement is input from the PU5, the output circle of the counter 43 has a count value that is equal to the start position designation signal Ss (m ), it changes from ``L'' to ``H'', and after counting the horizontal transfer pulse HTP by a preset value (for example, k) within the counter 43 itself, it changes from ``H'' to ``H'' again. Therefore, only while the output of the counter 43 is at the 'H' level, the horizontal transfer pulse HTP passes through the AND circuit 44 and is sent to the A/D converter 6 and the write timing circuit 45 as the ranging signal S5. Thus, the horizontal position and length of the ranging line (the part indicated by the small continuous circles in Figure 4 (a)) are
It is determined based on the start position designation signal Sa (m) from the CPU 5 and the set value (k) of the counter 43 itself.

The A/D converter 6 A/D converts the video signal S at the timing of the horizontal transfer pulse HTP input as the signal S5,
Write to the memory 8 based on the write signal and address data from the write timing circuit 45.

The CPU 5 calculates the brightness distribution using the video signal S written in the memory 8, compares the slope of the brightness distribution with a predetermined value, and detects a steep change point exceeding the predetermined value. There are various ways to calculate the brightness distribution, but for example, among the video signals written in the memory 8, the slope may be calculated sequentially from the difference in brightness level using video signals corresponding to some horizontal transfer pulses. There is a way to do it.

When the steepest change point is detected by CPU5.

It is determined that this is the in-focus position, and the CPU 5 outputs the in-focus signal F, and this in-focus signal F causes the motor control circuit 9 to
(See FIG. 2) while outputting a motor stop signal to stop the motor 10 that is moving the focus lens 1a.

The above description has been given of the case where the distance measurement line is set on one specific scanning line, but if focusing is not possible with that distance measurement line, the distance measurement line setting signal s output from the CPU 5
By changing 1, the distance measurement line is moved up and down in the vertical direction of the screen, and by changing the start position designation signal output from the CPU 5, the distance measurement area is moved in the horizontal direction of the screen. Perform focusing by moving the area on the screen. By doing this, even when photographing a plain wall, it is possible to focus on one point on the wall that appears on the screen if there is a small foreign object such as dirt.

Such movement of the ranging area can be realized by a program.

Now, the auto iris control operation will be explained based on the flowchart of FIG. 6. Note that the auto iris control operation starts after the above-described focusing operation ends.

While the focusing operation is in progress, the peak value detection circuit 7 detects the peak value of the video signal output from the camera circuit 3, converts it from A/D to A/D using the A/D converter 6, and stores it in the memory 8 (P -1). When the focus position F is output at the end of the focusing operation, the CPU must determine whether the peak value of the brightness signal exceeds a predetermined dangerous value that may cause burn-in on the image pickup tube 1.P-2 ), the CPU 5 outputs an iris signal. The motor control circuit 13 receives this iris signal 9D and drives the iris drive motor 14, thereby narrowing down the iris lb (P-3).

Here, enter the peak value of the luminance signal again (P-4), determine whether the peak value is greater than the dangerous value or not (P-5), and if it is greater than the dangerous value, return to step ('P-3) and adjust the iris. Keep narrowing down. Conversely, if the peak value of the iris becomes less than the critical value as a result of narrowing down the iris, the iris drive motor 14 is stopped (P-6). After that, the luminance signal of the video signal S is taken in and A
/D conversion Store as 8 light values in memory (P-7)
.

The CPU 5 integrates this photometric value to calculate the photometric amount.
-8), this photometric amount is compared with a predetermined target value for iris control (P-9). As a result, if the photometric amount is larger than the target value, the process returns to step (P-1), and if it is smaller, the process returns to step (P-4) and repeats the above-described operation.

Step (P-2) G: Let me explain this step back.

If the peak value detected by the peak value detection circuit 7 is less than the critical value indicating the degree of risk of burn-in of the image pickup tube 1, the luminance signal is captured and input as a photometric value (P-10). The CPU 5 integrates this photometric value to calculate the photometric amount (P-11), and compares the photometric amount with a predetermined target value for iris control (P-12), similarly to step (P-9). As a result, if the photometric amount is larger than the target value, the iris is stopped (P-13), and if it is equal to the target value, the iris motor 14 is stopped (P-1).
4) End the iris routine (P-16). If it is smaller than the target value, open the iris lb<(P-15).

In the case of steps (P-13) and (P-15), the process returns to step (P, -1) and repeats the above-described operation.

By controlling the iris by directly using the distance measurement area used in autofocus operation,
The iris control itself is significantly simplified, and since the iris control is performed at one in-focus position, it becomes possible to perform accurate iris control based on the optimum brightness of the subject.

In the above embodiment, a distance measurement line is set on one scanning line, and the video signal is continuously A/D converted and written into the memory, so an A/D converter capable of high-speed processing is required.

FIG. 7 shows another embodiment of the timing controller shown in FIG. 1, and is an embodiment in which focusing is determined using the distance measuring line shown in FIG. 4 (b).

The timing controller 4 (shown surrounded by a broken line) includes a counter 41 that receives a horizontal synchronization signal H3 and a vertical synchronization signal ■s from the camera circuit 3, and a ranging line setting signal S1 from the CPU 5.

The horizontal synchronization signal H8 is set by the output of the counter 41.
, and an AND circuit 46 that performs the logical product of the output of the counter 41, the output of the counter 45, and the horizontal synchronization signal H3.

It is set by the 'H' output of the AND circuit 46, and the CPU 5
A counter 47 that counts horizontal transfer pulses HTP from the camera circuit 3 and outputs a distance measurement signal based on a distance measurement start position designation signal s'3 from The sample and hold circuit 48 holds only the sample data.

Next, the circuit operation will be explained with reference to FIG.
When the horizontal synchronization signal H3 is counted up to 1, a coincidence signal S2 is output. The counter 45 is set by this signal 82G and starts counting the horizontal synchronizing signal H5, and outputs a ``H'' signal until the count value reaches the number of scanning lines defining the lowest position of the distance measurement line. Result, AND circuit 4
Reference numeral 6 outputs an ``H'' signal S1 for each scanning line between the highest position and the lowest position of the distance measurement line. A counter 47 receives a signal S' for each starting position of a scanning line that crosses the distance measurement line.
4 and starts counting horizontal transfer pulses H3P.

That is, when the counter 47 receives the horizontal synchronization signal H3n of the n-th scanning line at the top of the distance measurement lines, it starts counting the horizontal transfer pulses HTP, and the count value becomes the distance measurement start position designation signal S' given from the CPU 5. 3 (m), the distance measurement signal 8 is output only at that moment, the video signal S at that time is taken into the sample hold circuit 48 and held, and then A/D converted by the A/D converter 6G and stored in the memory. Write to 7.

C for the next scanning line (n+1) that crosses the distance measurement line.
This time, the PU 5 outputs (m+1), which is delayed by one horizontal transfer pulse from the previous scanning line, as the distance measuring bottle start position designation signal S'3. As a result, when the count value of the counter 47 reaches (m+l)f, the distance measurement signal 8 is output only at that moment, the video signal S at that time is taken into the sample hold circuit 48 and held, and thereafter, within l horizontal synchronization period. The data is A/D converted and written to the memory 7.

Similarly, for the next scanning line (n+2)), the counter 47
The count value is increased by one horizontal transfer pulse (
m+2), the A/D converted data of the video signal S is written into the memory.

In this way, the video signal S is similarly written into the memory 7G for a predetermined number of scans by the counter 45, but during this time the CPU 5 uses the video signal stored in the memory 7 according to a predetermined program to distribute the brightness. Calculate and examine the change in slope. As a result, when the change in the slope of the brightness distribution becomes the steepest, it is assumed that the focus is reached, and the focus signal F
Output. Upon receiving this focus signal F, the motor control circuit 5 stops the autofocus lens drive motor 9.

When the focus signal F is output from the CPU 5, the iris control explained using FIG. 6 starts. The iris control operation in this case is exactly the same as the operation described above, so a description thereof will be omitted.

In this embodiment, similarly to the embodiment shown in FIG.
The distance measurement line can be arbitrarily changed on the screen by changing the distance over time according to a predetermined program.

In this embodiment, the distance measurement line crosses a plurality of scanning lines and only the video signal corresponding to the I horizontal transfer pulse is captured for each scanning line, so the A
Can be processed with a /D converter. Furthermore, a color signal may be used instead of a luminance signal for determining focus.

(E) As described in detail, the present invention samples the video signal of a limited area on the screen, and performs automatic focus adjustment and aperture adjustment based on the sampled video signal. Therefore, since iris control is performed based on the subject that is in focus, it is possible to prevent the image pickup tube from being burned in even if an extremely bright part such as the sun or a light source enters outside the distance measurement area.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of an auto-iris device for a video camera according to the present invention, and FIG. 2 is a flowchart of an auto-focus operation. FIG. 3 is a block diagram of an embodiment of the timing controller used in the auto iris device shown in FIG.
The figures show two different examples of distance measurement lines used for focusing and iris control. Figures 5A and 5A are diagrams explaining the operation of capturing video data on the distance measurement lines in the auto-iris device according to the present invention. FIG. 6 is a flowchart of the auto-iris control operation according to the present invention, and FIG. 7 is a block diagram of another embodiment of the timing controller. 1... Lens system 1a... Focus lens 1b.
...Iris 2...Image tube 3...Camera times flFf1 4...Timing controller 4I...Counter 43...Counter 4
5...Write timing circuit 6...A/D converter 7...Peak value detection circuit 8.
...Memory 9...Motor control circuit IO...Focus lens drive motor 11...Focus lens drive gear ν...Rack 13...Motor control circuit 14
...°Iris drive motor patent applicant Hiroo Tsuchi Suzuki, attorney for Konishiroku Photo Industry Co., Ltd.

Claims (1)

[Claims] a sampling means for sampling a video signal constituting one screen output from a video camera while moving a focus lens along a predetermined distance measurement line on the screen; and a luminance signal of the video signal sampled by the sampling link means. and a control means for stopping the focus lens and controlling the iris based on the luminance signal when the goldfish signal is output. A distinctive feature is the auto iris device of the video camera.