JP2907901B2 - Focus area control method of video camera for video conference - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a focal area of a video camera for a video conference used in a video conference system.

[Conventional technology]

2. Description of the Related Art Conventionally, in a video conference system, a conference participant uses a manually-focused television camera that remotely focuses the television camera, or a video camera on a predetermined specific focus area (usually near the center of the screen). An autofocus television camera that automatically focuses on the image was used.

[Problems to be solved by the invention]

In the above-described conventional television camera, focusing is often required by remote control, or even when an autofocus television camera is used, the focal region is often fixed, and there are many backgrounds such as a video conference. In the scene, there is a problem that a person is not always focused.

[Means for solving the problem]

A method of controlling a focal region of a video camera for a video conference according to the present invention is a video camera for a video conference equipped with an auto-focus video camera, which converts an output image signal of the auto-focus video camera from analog to digital and pre-frames each frame. Divided into a plurality of blocks of a predetermined size, determine whether the block of a moving image or a block of a still image for each block, except for blocks that do not correspond to the region of the predetermined plurality of locations in the TV screen, If there are only still image blocks, the current area is selected. If there is only one motion image block, the area corresponding to the motion image block is selected. If there are two or more blocks, the center area of the TV screen is selected. Outputs a focus area control signal based on the selection result to the focus television camera, and selects one of a plurality of predetermined areas in the television screen Characterized in that to adjust the automatic focus image on the region Te.

[Action]

In the present invention, by applying the present invention to a video conference system having a relatively large number of still parts, automatic focusing is always performed on a person with a relatively large amount of motion.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

First, before describing the embodiments, the principle of the present invention will be described to facilitate understanding of the present invention.

FIG. 1 is a block diagram for explaining the principle of the present invention.

In the figure, reference numeral 11 denotes a function for automatically focusing on an image on a specific area (hereinafter, referred to as an auto-focus area) of a television screen, and moves the auto-focus area to an arbitrary position on the television screen. An autofocus television camera that can be controlled so as to cause the autofocus television camera 11 to select and set one of a plurality of predetermined positions in a television screen according to a focus area control signal 1311. It is configured to be able to. 12 this auto focus tv camera
An analog-to-digital converter (hereinafter abbreviated as an A / D converter) 11 converts the output image signal from analog to digital. An output signal from the A / D converter 12 is converted into a plurality of signals of a predetermined size. It is determined whether the block is a motion image block (hereinafter referred to as a moving block) or a still image block (hereinafter referred to as a static block), and outputs a focus area control signal 1311. This is a dynamic block determination circuit.

The focus area control signal 1311 supplied from the moving block determining circuit 13 to the auto-focusing television camera 11 is a means for moving the auto-focusing area to an arbitrary position on the television screen according to the determination result of the moving block determining circuit 13. Is composed.

With the configuration shown in FIG. 1, a moving area can be detected for each frame, and the autofocus area of the autofocus camera can be made to follow the moving area, so that a relatively moving person or the like is automatically focused. be able to.

 The present invention is implemented as follows.

 FIG. 2 is a block diagram showing one embodiment of the present invention.

In the figure, reference numeral 20 automatically focuses on an image on an auto-focus area in a television screen, and explains a focus area which the auto-focus TV camera can take as an auto-focus area by a focus-area control signal 2820. 3rd diagram for
An autofocus television camera having a function of setting one of the five areas A, B, C, D, and E shown in the figure. Reference numeral 21 denotes an output signal 2021 of the autofocus television camera 20 (in this embodiment, only the luminance signal component A / D conversion circuit for analog / digital conversion of the image data 2122 is divided into blocks (9 divisions) for performing the dynamic / static block determination on the image data 2122 which has been A / D converted by the A / D conversion circuit 21. 9) as shown in Table 1
This is a scan conversion circuit that divides the data into blocks and converts television scanning into block scanning.

23 is a frame memory, 24 is a subtractor, 25 is an input signal 2425
An adder that takes the absolute value of this and adds the absolute value sum signal 2529 in the block to the adder, 26 is a register cleared by the block reset signal 2726, 27 is reset by the synchronization signal 2027 and outputs the block reset signal 2726 and the block signal 2728 Timing generation circuit, and 28 is a dynamic block signal 2928
And the block signal 2728 as input, accumulates the dynamic / static block information of 9 blocks (No. 1 to 9 in Table 1) for one frame, and based on the dynamic / static results of these 9 blocks. A control circuit 29 for outputting the focus area control signal 2820 compares the absolute value sum signal 2529 within the block with a predetermined threshold value TH, and outputs the predetermined threshold value TH based on the absolute value sum signal 2529 within the block. If it exceeds, the block is regarded as a dynamic block, and if it is less than a predetermined threshold value TH, it is determined to be a static block,
This is a dynamic / static block determination circuit that outputs a dynamic block signal 2928. 2224 indicates a current frame image signal, and 2324 indicates a previous frame image signal.

Table 2 is a table for explaining details of functions of the control circuit 28 as an example.

In Table 2, a mark "○" indicates a dynamic block, a mark "X" indicates a static block, and a mark "-" indicates a dynamic or static block. Note retains the previously selected focus area.

Table 2 is a block number 1 to 1 shown in Table 1.
9 and five focus areas A to E shown in FIG. 3 are selected by inputting the motion / static judgment result of each block (in the table, ：: represented by a dynamic block, ×: represented by a static block). Is shown.

The example shown in Table 2 is a comparatively simple example. The dynamic / static information of the blocks Nos. 2, 4, 6, and 8 is ignored, and the remaining blocks (Nos. 1, 3, 5, 7) are ignored. , 9), the focus area is selected based on the result of the motion / still judgment. If two or more motion blocks occur, the focus area A which is the center of the screen is selected, and if all the blocks are static blocks, The control is performed such that the position of the focus area is not changed and the focus area is maintained in the previously selected focus area.

〔The invention's effect〕

As described above, the present invention can be applied to a video conference system having a relatively large number of still parts, so that the automatic focusing can be always performed on a person having a relatively large number of movements.
In addition to the fact that manual focus adjustment is not required, there is an effect that the background is not focused by a scene.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining the principle of the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a focus which the autofocus television camera in FIG. It is a figure for explaining a field. 11: Auto focus camera, 12: A / D converter, 13: Dynamic block judgment circuit, 20: Auto focus TV camera, 21 ...
A / D conversion circuit, 22 scan conversion circuit, 23 frame memory, 24 subtractor, 25 adder, 26 register
27: Timing generation circuit, 28: Control circuit, 29: Dynamic / static block determination circuit

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-1-16178 (JP, A) JP-A 1-175373 (JP, A) JP-A 1-289781 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H04N 5/232 A H04N 5/232 Z H04N 7/15

Claims (1)

(57) [Claims] 1. A video camera for a video conference provided with an autofocus television camera, wherein an output image signal of the autofocus television camera is converted to an analog / video signal.
Digitally converted, divided into a plurality of blocks of a predetermined size for each frame, and determined for each block whether it is a block of a moving image or a block of a still image, and a plurality of predetermined regions in a television screen Excluding the blocks that do not correspond to, the current region is the case of only the block of the still image, the region corresponding to the block of the moving image when there is one block of the moving image, and the center of the TV screen when there are two or more blocks of the moving image. And outputs a focus area control signal based on the selection result to the autofocus television camera, selects one of a plurality of predetermined areas in the television screen, and automatically outputs an image on the area. A method of controlling a focal region of a video camera for a video conference, comprising: