JPH01132279A - Auto-focus video camera - Google Patents

Abstract

PURPOSE:To detect a focusing position of a zoom lens automatically in a macro region by using a focusing appreciation value, used for the drive control of a focus motor to displace a focus lens to a position where it comes to a maximum value, for the drive control of a zoom motor in the macro region as well. CONSTITUTION:The movement of the respective lenses in the macro region is different from the movement in a zoom region, and it has a characteristic that the execution of focus action comes possible similarly to a case that the focus lens 2 is displaced. Accordingly, in this macro region too, the rotation control of the zoom motor 6 is executed in a zoom motor control circuit 31 by the output of the comparison circuit 19 so that it reaches the top M' of the mountain of the appreciation value. Namely, the rotating direction of the zoom motor 6 is determined to be the direction in which the focus appreciation value of the present field of a first memory 17 comes always larger compared with the focus appreciation value before one field of the second memory 18, and the zoom motor 6 is stopped at the point of time that it reaches the top M'.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to an autofocus system for a video camera that automatically adjusts focus based on a video signal obtained from an image sensor.

(Main) Conventional technology In the autofocus device of a video camera, the method of using the video signal itself from the image sensor to measure the focus control state has essentially no variation, and is difficult to use when the depth of field is shallow or when shooting at a far distance. Many runners-up are excellent in that they are able to focus accurately even on subjects such as Moreover, it is for autofocus! No separate sensor is required and the mechanism is extremely simple.

Conventionally, as an example of this auto-7 orcus method, the so-called hill-climbing autofocus method disclosed in Japanese Patent Application Laid-Open No. 60-97784 (HO4N5/232) is well known.

In this method, the high-frequency components of the luminance signal in the imaged video signal obtained from the image sensor are sequentially integrated over one field, and this integrated value is used as a focus evaluation value and compared for each field. The drive of the focus motor is controlled to displace the focus lens in the optical axis direction until the value reaches the maximum value.

By the way, video cameras are generally provided with a stopper to prevent the focus ring that supports the focus lens from rotating beyond the infinity point or the near point.

Therefore, the above-mentioned mountain climbing method is applicable when the subject exists between the near shield of the focus lens and the infinity #r, but when the subject is at a closer distance than the near point,
That is, when the focus lens is in the macro area, the focus lens cannot be moved to the in-focus position.

Therefore, normally when performing a focusing operation at a short distance, for example, ``Video Cameras and How to Use Them'' (May 20, 1980, published by Japan Broadcasting Publishing Association), p. 144~ The method disclosed on page 145 has been awarded.

In other words, a zoom lens that uses a macro (super close-up) mechanism on a video camera! The zoom lens that is attached to the lens and zooms from the telephoto position to the wide-angle position in the normal range from the near point to the infinity point is used for focusing when the subject is at close range, and this zoom lens is used for zooming from the normal wide-angle limit to the wide-angle limit. Furthermore, the lens is manually forced to move in the wide-angle direction and is configured to stop at a position where the user can recognize that it is in focus.In this macro area, the focus lens is fixed at the near point. ing.

(C) Problems to be Solved by the Invention According to the prior art described above, the focus operation in the macro area is performed by manually rotating the zoom ring to fully displace the zoom lens, which is extremely difficult to operate.

B.) Means for Solving the Problems The present invention provides a method for driving a zoom motor in a macro region with a focus measurement value t1 for controlling the drive of a focus motor that displaces a focus lens to a position where the focus lens is at its maximum value in a normal region. It is also used for control, and is characterized by displacing the zoom lens to the position where the maximum value is obtained.

(E) Function Since the present invention is configured as described above, the zoom lens is displaced in a macro area so as to automatically detect the in-focus position.

(f) Example An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a side view of the imaging mechanism of the device of this embodiment, and (1
) is a focus ring that supports the focus lens (21), and a meshing part (1a) is formed on the curved surface, and a gear (6&) rotated by the focus motor (3) meshes with this meshing part (1a). ing.

(5) is a zoom ring that supports the zoom lens (4), and a gear (6) that rotates with a zoom lens (6) on the circumference.
0 (7) is a lip with a first stage for zoom position/detection formed on the zoom ring (5), and is fixed to the support part (8). The movable contact piece (9a) of the detection switch (9)
7a), the intermediate part (7D), and the concave part (7o) can be brought into contact with each other, and in the state of contact with the convex part (7a), 'pgje (
in the telephoto) area, in contact with the middle part (7b)
le (middle) area, detects the presence of the zoom lens (4) in the wide (wide-angle) area while in contact with the concave part (7c) the zoom ring (
5) is a lip with a second step for macro area detection, and when the movable contact piece (9!L) is in contact with the first step part (10a), the zoom lens (4) is in the macro area. It is detected that the limit point of the macro area has been reached when the second step (10 m) K runs over.

(Ill is the ninth electromagnetic lock that distinguishes the movement of the zoom ring (5) into the macro area and other areas. When the zoom ring (5) rotates in the direction of the arrow, the movable contact piece (9a) moves into the recess ( This is a mechanical locking means that prevents rotation of the zoom ring (5) at a position just before it runs onto the first step part (10a) from 7a).

TI is a release mechanism switch that manually releases the electromagnetic lock (lυ). 0 is the lens barrel, and Q4 is the board to which the OOD (image sensor) is fixed.

Next, the focusing operation will be described in detail using the circuit block diagram shown in FIG.

The incident light from the subject passes through the focus lens (2) and zoom lens (4) and is focused on 0ODO4+, and the image output created here becomes the imaged video signal in the process circuit t1!9, which is the focus evaluation value. The signal is input to the generation circuit TIE.

The focus evaluation value generation circuit <IG is configured as shown in FIG. Vertical synchronization signal (''/D)% horizontal synchronization signal (H
D) is input to the gate control circuit (161) to set the sampling area. Gate control circuit (16
1)), vertical synchronization signal (VD)% horizontal synchronization signal (H
D) and a fixed oscillator output, set a rectangular sampling area in the center of the screen, and supply a gate opening/closing signal to the gate circuit (160) that allows passage of the luminance signal only within this sampling area. do.

Only the luminance signal corresponding to the range of the sampling area is passed through the gate circuit (16Q') through the high-pass filter (H, P, F) (16(1)) to separate only the high-frequency components and send it to the next stage. Amplitude detection is performed by the detection circuit (16θ).This detection output is integrated for each field by the integration circuit (16f), and converted to a digital value by the A/D conversion circuit (16g) to evaluate the focus of the current field. The focus evaluation value generation circuit 11e configured as described above always outputs the focus evaluation value for one field.

This focus evaluation value is once held in the first memory αD, and then input to the second memory αS and the comparison circuit (19).The second memory holds the focus evaluation value one field before the first memory (171). The comparison circuit a9 successively compares the focus evaluation value of the current field and one field before.

(A) is a near point switch that mechanically detects that the focus ring (11) comes into contact with the near point stopper and the focus lens (2) has reached the near point.

(21J is a motor switching circuit that controls the switching circuit based on the output of the comparison circuit (19 output and the near point switch). For example, when the subject is between the near point and the infinity point of the focus lens (2), In some cases, the relationship between the focus evaluation value and the lens distance (the distance from the focus lens (2) to the subject) becomes as shown in Figure 4, and the top of the mountain with the maximum evaluation value appears, so the motor In the switching circuit (2D), the output of the switching circuit (19) is supplied to a comparison circuit (19), and the rotation direction and stop timing of the focus motor (3) are determined based on this comparison output.

The focus operation in this case is to first rotate the focus motor (3) in any direction as an initial state, and if the focus evaluation value increases, maintain the same rotation direction;
If it decreases, the rotation direction is reversed and the focus lens is constantly moved in the increasing direction, and when it passes the peak and begins to decrease, the focus motor (3) is immediately reversed and returned by a predetermined amount to focus. Stop the motor (3) at the apex.

If there is a subject between the near point and the infinity point, the zoom lens (4) is set to Te1 by the zoom command means.
A command is issued to the zoom motor control circuit C11 so that three areas of , Middle, and Wide can be selected.
Control the zoom motor (6). The zoom area is detected by using the movable contact piece (9a) and the first recessed lip (as described above).
7) is detected by the detection switch (9) depending on the state of contact with w.
Even if the tae region is selected and the zoom ring (5) continues to rotate, the rotation is blocked at the position just before the movable contact piece (9a) runs over the first step (10&) from the recess (70). It never becomes a macro area.

Next, if the subject is closer than the near point, the focus evaluation value will be maximum at the near point, as shown in Figure 5, but the top of the mountain will not appear further away from the near point. Therefore, the motor switching Circuit C! υ reaches the maximum evaluation value at the near point, and detects that the increasing trend continues up to this point, issues a switching signal, switches the switching circuit, and supplies the comparison circuit 0 output to the zoom motor control circuit (31+). This switching signal is also supplied to the electromagnetic lock Qll, and the electromagnetic lock aυ is thereby unlocked.

When the zoom motor control circuit Gll receives the comparison output, the zoom command means (7) deactivates the zoom ring (5) so that the zoom lens (4) unconditionally enters the macro area. The movable contact piece (9a) is further rotated in the direction of the arrow in FIG.
I).

In this macro area, a zoom lens (41u T e
As shown in the zoom range from l e to Wiae, the focal length up to CtOD is changed without changing the focus position, and the operation that does not cause a change in the focus state due to zooming is not performed. Execute the commonly known macro, focusing.

That is, although the normal zoom lens (4) supported by the zoom ring (5) is shown as a single lens as shown in Fig. 2 for ease of explanation, it is actually a variable magnification lens. It is composed of a variator, a compensator that does not change the focal plane, and multiple lens groups called erector and relay lenses.In the macro area, the movement of each lens group is different from that in the zoom area. It has a characteristic that the focus operation can be performed in the same way as if the focus lens (2) were displaced.

Therefore, even in this macro area, the zoom motor (6) is adjusted so that the output of the comparison circuit α9 reaches the peak of the focus evaluation value.
Rotation control is performed by the father motor control circuit c313. That is, the rotation direction of the zoom motor (6) is determined in such a direction that the focus evaluation value of the current field in the first memory fiη is always larger than the focus evaluation value of one field before the second memory α seconds, and - When the zoom motor (
6) Stop. The focus operation at this time is exactly the same as the mountain climbing servo controlled by the focus motor described above, except that the motor is a zoom motor.

In addition, the electromagnetic lock a can be manually activated using the release mechanism switch (121).
By releasing υ and manually rotating the zoom ring (5), manual focusing operation in the macro area is also possible as in the conventional example. Furthermore, in the macro area, the zoom ring (5) moves in the direction of the arrow in Fig. 2, and the movable contact piece (9a) rides on the second step (101), that is, the subject approaches the lens extremely. If the macro area cannot be covered because of the macro area, the zoom lens (4) is stopped at the limit point (near point) of the macro area and the focusing operation is completed.

It goes without saying that the circuit block shown in FIG. 1 can be processed by software using a microcomputer.

FIG. 6 is a flowchart illustrating the operation of the circuit block diagram of FIG. 1.

In FIG. 6, the hill-climbing servo in step (40) performs the focus operation in accordance with the displacement of the focus lens (2), and the hill-climbing servo in step (411)
shows macro focusing. Also, step (4)
? Detection of reaching the far point of J is done by a far and white stopper (not shown) that detects when the focus ring (1) has rotated until the focus lens (2) reaches the infinity point. , the focus lens (2) is fixed at the infinity point.

In addition, in step (43 (44) (4!9 (46)), if the subject moves after the focus operation is completed, it is detected that the focus evaluation value has fluctuated by a certain threshold or more, and the focus operation is restarted from the beginning. It is shown that.

(G) Effects of the Invention According to the present invention as described above, the focus lens is automatically displaced in areas other than the macro area so that the focus evaluation value reaches the top of the mountain, and the focus evaluation value also reaches the peak in the macro area. The zoom lens is automatically displaced so as to reach the apex of , and macro focusing D1' is executed, making it possible to perform an autofocus operation with high precision and excellent operability.

[Brief explanation of the drawing]

The drawings all relate to one embodiment of the present invention, and Fig. 1 is a circuit block diagram, Fig. 2 is a side view of the imaging mechanism, Fig. 3 is a main circuit block diagram, and Figs. 4 and 5'' are focal points. FIG. 6 is a flowchart showing the relationship between evaluation values and lens positions. a4...0OD (imaging device), (lG...focus evaluation value generation circuit, (2)...focus lens, (3) )
... Focus motor, +4) ... Zoom lens,
(6)...Zoom motor.

Claims (1)

[Claims] (1) a focus evaluation value generating means that outputs the level of a high-frequency component of an imaged video signal obtained by an image sensor as a focus evaluation value; a focus motor that displaces the focus lens to a position where the evaluation value is maximum; and a zoom lens that displaces the zoom lens to a position where the focus evaluation value is maximum when the subject is closer than the near point of the focus lens. An autofocus video camera consisting of a zoom motor.