JPH04404A - Video camera - Google Patents

Abstract

PURPOSE:To make automatic focusing operation efficient by moving a focus lens in one direction and changing the moving direction unless proper evaluation data is obtained within a specific period after an intermediate position is detected. CONSTITUTION:A controller 10 moves the focus lens as shown by, for example, an arrow Z and a focus lens position detector 13 detects a 2.5m focus position as the intermediate point. Simultaneously with this intermediate-point detection, the controller 10 makes its internal counter count the time and reverses the driving direction of the lens unless the proper evaluated value data Dt for focusing is obtained before the counter enters the time-up state. Such unneces sary operation that the focus lens is driven to an end point position and the direction is changed there for N-directional movement to reach a point Pj of the proper evaluated value data for the 1st time is eliminated to enable efficient focus operation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video camera having an autofocus function.

[Summary of the Invention] In the video camera of the present invention, when the focus lens is driven in one direction during autofocus, appropriate focus control information is provided for a predetermined period after reaching the midpoint of the lens movable range. If the point cannot be obtained, it is assumed that there is no just focus point in the direction of travel, and
The direction is reversed. With this control, even if there is no just focus point in the direction of lens movement, the lens is not moved to the end point position, and the autofocus operation becomes more efficient.

[Prior Art] As a focus lens drive control method for autofocus operation, the frequency component of the video signal excluding the direct current component is maximized at the focus position, and the frequency component of the video signal excluding the direct current component is used. There is a known method (so-called hill-climbing control) in which the value obtained by integrating the frequency components is used as evaluation value data as autofocus control information, and the focus ring is driven to the position where this evaluation value data is maximized to control the focus lens position. (Patent application Sho 62-14662
No. 8).

For example, assume that when a focus lens (focus ring) is controlled to move within the range of N (wide-angle) and H (telephoto) for a certain subject, a curve of evaluation value data Dt is obtained as shown in Figure 4. do. If the focus lens is at the Pl point when the autofocus operation starts, first move the focus lens in any direction to obtain the evaluation value data Dt, and check the direction in which the high evaluation value data Dt is obtained (hereinafter, This action is called a direction-determining action). Then, while driving the focus lens in a direction in which the high evaluation value data Dt is obtained, the evaluation value data Dt is
are obtained one after another, and finally, while making small adjustments in the father direction or N direction near the top of the curve of the evaluation value data, the point where the highest evaluation value data Dt is obtained, that is, P,
This method places the focus lens at a specific point.

Note that the direction of movement at the start of the autofocus operation, that is, the direction of movement in the direction determining operation, is set, for example, based on the focus position in the immediately preceding autofocus operation. The direction of movement is not always determined to be the father direction or the N direction.

[Problems to be Solved by the Invention] However, in such an autofocus control method, when the evaluation value data Dt as shown in FIG. If the focus lens is driven in the forward direction and a direction determining operation is performed at the start of the autofocus operation, appropriate evaluation value data cannot be obtained during the direction determining operation. In other words, even if the lens is driven from point P to stationary far position P2, the evaluation value data D
Since t is almost constant at a very low level or is hardly obtained, it cannot be determined whether the peak of the evaluation value data Dt is in the father direction or in the N direction from point P.

Therefore, the focus lens is driven as it is to the end point position P2, and there the direction is changed and moved in the N direction, and only after passing through the P1 point is the appropriate evaluation value data Dt.
From there, the mountain climbing control will reach point P. That is, a very wasteful operation must be performed between P and P2.

In this way, especially when the in-focus position is near one of the end points, if the focus lens is driven in the opposite direction to the in-focus position at the start of autofocus operation, that operation will become inefficient. There are also problems in that the autofocus control time becomes longer and the lens movement becomes unsightly.

[Means for Solving the Problems] The present invention has been made in view of these problems, and includes detecting at least whether the focus lens is at both ends of its movable range or at an intermediate point. In addition, if suitable focus control information is not obtained for a predetermined period after the intermediate point is detected during the direction determination operation at the start of the autofocus operation, the moving direction is reversed. The present invention provides a video camera equipped with a control means.

[Function] Although it depends on the detection method of evaluation value data as focus control information, in most cases for various subjects, the curve of evaluation value data is as shown in Fig. 1 (a) If a mountain is formed within the range of N (widest angle position) to the focal position, (b) If a mountain is formed within the range of 2.5m focal point to oo (stationary far position), (c) When a mountain is formed around the 2.5m focal point, it is classified as follows. In particular, the inefficient autofocus operation described above occurs in cases (a) and (b).

Therefore, for example, if a 2.5m focal point is detected as an intermediate point, and proper evaluation value data is not obtained for a predetermined period after the moving lens passes this intermediate point, then In this case, it can be determined that there is no just focus point.

[Embodiment] FIG. 2 shows a block diagram of an autofocus control circuit system of an embodiment of the video camera of the present invention.

1, the focus lens is moved by the drive motor 2 to move the arrow A,
A lens system whose focal position is controlled by being rotated in direction B and moved in the direction of arrow C9D is shown. This lens system is capable of autofocus operation by performing mountain climbing control using a contrast detection method (frequency separation method), which will be described below. In this case, the focus lens focuses on a long distance when it is driven in the A direction (= when it moves in the C direction), and it focuses on a near distance when it is driven in the B direction (= when it moves in the D force direction). The distance shall be focused.

Reference numeral 3 denotes a CCD image sensor, which captures a subject image through the lens system 1 and outputs the image signal to the signal processing circuit 4.

The signal processing circuit 4 forms a luminance signal and a chroma signal from the output signal of the CCD image sensor 3, and is composed of a process circuit, a color encoder, and the like.

5a and 5b are bandpass filters to which the luminance signal taken out from the signal processing circuit 4 is supplied. The band pass filter 5a has a center frequency of, for example, 100 KHz, and the band pass filter 5b has a center frequency of, for example, 5 KHz.
00 KHz. These band pass filters 5a, 5
b, a predetermined frequency component in the luminance signal supplied from the signal processing circuit 4 is extracted. The extracted frequency components are then supplied to detection circuits 6a and 6b via amplifiers, and the level of the predetermined frequency components is detected.

7 is a switch circuit, and bandpass filters 5a, 5
1. Select whether to use the detection output of the frequency component extracted in 1 as autofocus control data under the control of the autofocus control system controller (hereinafter referred to as controller) 10. For example, when the subject has a strong contrast, the band The output of the pass filter 5a is selected, and when the object has a weak contrast, the output of the band pass filter 5b is selected.

The detection output selected by the switch circuit 7, that is, the signal at the level of a predetermined frequency component in the luminance signal, is digitized by the A/D converter 8, and the digital output is supplied to the integration circuit 9. The controller 1 is installed in the integration circuit 9.
An integration area control signal is supplied from the A/D converter 8, and level data of a predetermined frequency component in the luminance signal input from the A/D converter 8 is integrated over a period specified by the integration area control signal. As an actual integration operation, for example, a method of integrating the maximum value in one horizontal period for one field can be considered. This integration result data is supplied to the controller 10 as evaluation value data Dt.

The controller 10 is configured to perform hill climbing control using the supplied evaluation value data Dt and to achieve autofocus operation. In other words, the focus lens is driven, and the distribution and intensity of the spectral components are measured in the process of going from a completely out-of-focus state to an in-focus state, and then back to an out-of-focus state. The spectral components are closer to the high range side and smaller in size, and as the focus comes, the spectral components move to the higher range side and the size becomes larger. Various curves such as the following are obtained.Therefore, autofocus control can be achieved by driving the lens to the PJ position so that the data obtained by integrating the high-frequency components extracted from the video signal is maximized.

A focus lens motor drive circuit 11 drives the drive motors 2a and 2b in accordance with drive direction control signals (SF, Sa) from the controller 10. Further, a drive speed control signal Ss is supplied via the D/A converter 12, and the lens drive speed is set based on the drive speed control signal Ss. Note that the drive direction control signals S, , S, and drive speed control signal Sll are generated by the hill-climbing control described above during autofocus operation. The lens is driven in the telephoto direction (00) by the drive direction control signal SF, and the drive direction control signal S! l allows wide-angle side direction (
N).

Reference numeral 13 denotes a focus lens position detector, for example, a reflective film is formed in a predetermined range of a cylindrical portion of the focus lens, and a detection light is irradiated onto this cylindrical portion from a light emitting diode.
The focus lens position can be detected depending on whether the irradiated position is the reflective film forming part, that is, whether the rotational position of the cylindrical part in the entrance direction or the B direction is a position where reflected light can be obtained. The detection signal is input to the controller 10 via the A/D converter 14. In particular, in this embodiment, the position detector 13 detects that the lens has reached the end point position (the tatami floor corner position or the stationary far position) and that
Reaching the focal position is detected.

In this embodiment in which the autofocus control circuit system is configured in this manner, as described above, the controller 10 executes hill climbing control based on the evaluation value data Dt, and the focus lens is driven to achieve autofocus. However, the autofocus operation (hill-climbing control) is achieved through five stages of control: (1) drive start mode, (2) direction detection mode, (2) focus point passing mode, (2) reversal return mode, and (2) fine adjustment mode.

For example, as explained in FIG. 4 above, if the lens is located at point P1, the lens is first moved in a predetermined direction in drive start mode ■, and then in direction detection mode ■. The sequentially obtained evaluation value data Dt, Dt・
The direction determination operation is performed based on... Then, in the focus point passing mode (2), the camera moves in the determined direction while detecting the evaluation value data Dt. At this time, the evaluation value data Dt that is sequentially detected becomes higher as it approaches the in-focus position, but when the lens passes the just focus position PJ, the evaluation value data Dt obtained at that point has a lower value than the immediately preceding evaluation value data Dt.

That is, it is detected that the lens has passed through the just focus position due to a decrease in the evaluation value data. Therefore, the direction of movement is reversed as reverse return mode ■, and the movement is slightly moved toward the just focus point PJ.Finally, as the fine adjustment mode ■ is selected, the movement direction is reversed and moved slightly in the N and ■ directions until the just focus point PJ is reached. A point is reached where high evaluation value data Dt can be obtained.

In this embodiment, when the controller 10 controls the autofocus operation described above, operations associated with intermediate point detection are executed as shown in the flowchart of FIG. 2.

That is, the controller 10 outputs the drive speed control signal Ss and the drive direction control signal SF or SR to drive the unidirectional lens in the drive start mode (Floo).
Subsequently, a direction determination operation is performed in the direction detection mode (2). In other words, when the evaluation value data Dt increases as the movement progresses, it is determined that a peak point exists in the direction of movement, and the focus lens is positioned at the just focus point P by moving in modes ■ to ■. (F.I.O.
I-F2O3). Also, according to the movement, the evaluation value data Dt
is decreasing, it is determined that a peak point exists in the direction opposite to the direction of travel, and the other drive direction control signal SR is
Alternatively, output SF to reverse the moving direction, and then similarly position the focus lens at the just focus point P by operating modes ■ to ■ (F102→F107→F)
108).

However, if the direction determination operation is impossible, that is,
If the evaluation value data Dt is not obtained even if the movement is continued in one direction, or if the evaluation value data Dt remains constant at a very low level, the focus lens 2.
When the 5m focus position is reached, the built-in counter means
Execute time count (F2O3-F2O3).

For example, in the case of FIG. 1(a) or FIG. 1(b), when the focus lens is driven in the two directions of the arrows from the point P1 in mode 2, this case corresponds.

Then, it continues to move in that direction, but if the evaluation value data Dt that increases sequentially is obtained, it directly enters the operation of modes ■ to ■ and positions the focus lens at the just focus point PJ (F105→ F1
08).

However, if proper evaluation value data cannot be obtained within a predetermined period until the counter means times up even if the motor continues to move, driving direction reversal control is performed. For example, in Fig. 1 (a) or (b), the period required to move the lens from the 2.5 m focusing position to point P3 is counted, and during this time the lens continues to be driven in the same direction. When you reach point P3 and count up,
If proper evaluation value data Dt is still not obtained, it is determined that the movement is backward with respect to the in-focus position, and the driving direction is reversed (F2O3-F2O3). After that, it is driven in the opposite direction, and when it reaches the point where the evaluation value data Dt is obtained, it enters the operation of modes ■ to ■.
Position the focus lens at just focus point PJ (-F2O3).

As the controller 10 performs the above operation control, the video camera of this embodiment can move the end point even if the focus lens is moved in the opposite direction in mode (2) and the direction is opposite to the in-focus position. reach the position,
There will be no unnecessary movements such as turning around.

Note that the intermediate position does not necessarily need to be set to the 2.5 m focusing position, and an appropriate intermediate position may be determined according to the characteristics of the video camera used. Further, the predetermined period from the 2.5 m focusing position is also determined according to the characteristics of the implementing device.

Note that the predetermined period from the intermediate position (P in the above example)
, -P, movement period) may be determined by detecting the position of the P3 point itself, without depending on the time count.

[Effects of the Invention] As explained above, in the video camera of the present invention, when the focus lens moves in one direction and proper evaluation value data is not obtained within a predetermined period after reaching an intermediate position is detected, Since the system is equipped with a means to control the direction of movement in the opposite direction,
This eliminates the need for the focus lens to travel backwards to the end point, contrary to the in-focus position, and achieves efficient autofocus operation.

[Brief explanation of the drawing]

Figures 1 (a), (b) and (c) are explanatory diagrams of types of evaluation value data, Figure 2 is a block diagram showing an embodiment of the autofocus control system of a video camera of the present invention, and Figure 3 is a diagram of the present invention. FIG. 4 is a flowchart showing the autofocus control operation in the embodiment, FIG. 4 is an explanatory diagram of mountain climbing control, and FIG. 5 is an explanatory diagram of reverse running operation to an end point. 1 is the lens system, 2 is the focus lens motor, 3 is the CC
10 is a controller, 11 is a focus lens drive circuit, and 13 is a focus lens position detector. a □ Lens movement range □ Figure -1 - Lens movement range □

Claims (1)

[Claims] In a video camera configured to perform autofocus operation by driving a focus lens based on autofocus control information, at least the focus lens is positioned at both end points of its movable range. A detecting means capable of detecting that the focus lens is located at an intermediate point is provided, and when the focus lens is moving in one direction during autofocus operation, the intermediate point is detected by the detecting means. A video camera characterized in that the video camera is equipped with a control means configured to reverse the direction of movement if appropriate focus control information is not obtained within a predetermined period.