JPH04342216A - Focusing - Google Patents

Abstract

PURPOSE:To provide a focusing device which can execute focusing exactly and with high accuracy irrespective of a photographing state, the condition of photographer's eyes, the degree of skill, etc. CONSTITUTION:Focusing lens moving means 9, 10 move a master lens 104 prepared to focusing in a lens means 1 and execute the focusing. Light condensed by the lens means is converted to an electric signal in a photoelectric convertion means, and a focus detecting means outputs the present focus evaluating value y(n) from a luminance signal Y in this electric signal. This device is provided with a delaying circuit 17 for delaying this focus evaluation valye y(n) outputted from a focus detecting circuit 4 by a prescribed period, and the difference of the focus evaluating value y(n) and a focus evaluating value y(n-1) before the prescribed period outputted from the delaying circuit 17 is derived in an arithmetic circuit. Also, a control circuit 5 moves a lens part offered to focusing by controlling a focus lens moving means, at the time of focusing by a manual operation, and also, executes the speed reduction control of the moving speed of a focusing lens, when the difference of the focus evaluation value y(n-1) delayed by the prescribed period and the present focus evaluation value y(n) is varied from large value to small one.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] This invention relates to a camera-integrated VTR.
The present invention relates to a focus adjustment device used for such applications.

0002

[Prior Art] Currently, as autofocus (hereinafter referred to as AF) for camera-integrated VTRs, etc., the video AF method that uses video signals and the infrared distance measurement method that uses infrared rays are in practical use. . However, none of these methods can be said to have sufficient performance, and most of them also have a manual focus (hereinafter referred to as MF) function.

However, the criterion for making MF decisions is the photographed image reflected in the viewfinder (hereinafter referred to as EVF), but many of these EVFs are small and difficult to see, making it difficult to make accurate focus decisions. Difficult to do. Recently, in order to downsize, there has been a trend toward the adoption of zoom lens barrels that do not allow direct manual movement of the focus lens, such as the inner focus system in which focus is adjusted using the rear group lens without moving the front group lens. At present, it cannot be said that the usability of the MF function has improved.

FIG. 3 shows a block circuit diagram of the configuration of a focusing device that combines an inner focus zoom lens with a video AF method. In FIG. 3, (1) is an inner focus zoom lens as a lens means, and this zoom lens (1) includes a fixed front lens (101) for focusing, a variator (102) for variable magnification, and a variator (102) for variable magnification. It has a compensator (103) that corrects the image plane as the lens moves (102), and a master lens (104) that is part of the relay system lens and is used for focusing. It is composed of a lens group, but here it is represented by a single lens.

(2) is a CCD as a photoelectric conversion means provided on the outgoing light side of the zoom lens (1);
(2) converts the subject image formed by the zoom lens (1) into an electrical signal. (3) is a camera signal processing circuit which inputs the electric signal from the CCD (2), and this camera signal processing circuit (3) outputs a video signal V and a luminance signal Y (FIG. 4(a)).

(4) is a focus detection circuit which inputs the luminance signal Y from the camera signal processing circuit (3), and this focus detection circuit (4) detects a signal b (FIG. 4(b) )) high-pass filter (hereinafter referred to as “H
PF") (401), an amplifier (404), and a low-pass filter (401) that outputs a signal c (FIG. 4(c)) that cuts unnecessary high-frequency components from the output signal of the amplifier (404).
(hereinafter referred to as "LPF") (405), LPF (405)
) is detected and a smooth waveform signal d (Figure 4
(d)), an A/D converter (407) that converts the input signal d into a digital signal, and a digital converter (407) that converts the input signal d into a digital signal. The digital addition output of the adder (408) is the focus evaluation value y.
(an index indicating the state of focus). (5) is a control circuit into which the focus evaluation value y output from the adder (408) is input; (6) is a zoom motor (6) that moves the variator (102) based on the zoom command from the control circuit (5); 7), and (8) is a potentiometer that detects the position of the variator (102), that is, the focal length, and outputs a signal with a potential that corresponds one-to-one with the lens position.

(9) is a master lens for focusing (1
A control circuit (
5) The focusing lens moving means is constituted by a pulse motor driver driven based on the focus command. (11) is an end point detection switch that detects the end point of the movable range of the master lens (104), and this end point detection switch (11) is turned ON when the master lens (104) is focused on an object at infinity. This represents the amount of movement of the master lens (104) based on this position.

(12) is the focus changeover switch that switches between AF and MF modes, and (13) is the MF switch near. When the MF switch near (13) is pressed in the MF mode, the focus is on a nearby subject. The master lens (104) moves in the direction in which the two lenses match. (14) is the MF switch far, and has the opposite function to the MF switch near (13). (15) is a display circuit that displays the video signal V on the EVF (16).

First, the AF adjustment operation using the video AF method will be explained. Object light incident through the zoom lens (1) is converted into an electrical signal by a CCD (2), and becomes a video signal V through a camera signal processing circuit (3).

Luminance signal component Y of this video signal V (FIG. 4(
a)) is led to the focus detection circuit (4), and first the HPF (
401), the signal b of the predetermined high frequency component (FIG. 4(
b)) is extracted. This signal b is amplified by an amplifier (404) and then band-limited by an LPF (405) (Fig.
(c)), detected by the detector (406) (Fig. 4(d)
). Furthermore, it is converted into a digital value by an A/D converter (407), and the data in the focus detection area shown in FIG. 4 is added by an adder (408), and the result is output as a focus evaluation value y. In other words, the focus evaluation value y is the integral value of the high frequency component, and since this high frequency component corresponds to the contrast of the screen, the contrast is maximum, that is, the maximum value when the master lens (104) is at the in-focus point. The value becomes smaller as the distance from the focused point increases.

Therefore, as the master lens (104) moves, the focus evaluation value y has a chevron-shaped characteristic as shown in FIG. The control circuit 5 controls the pulse motor (10) to drive the master lens (104) to the in-focus point so that the focus evaluation value y is always the maximum.

Note that the difference between the characteristics y1 and y2 in FIG.
This is due to the difference in the cutoff frequency of the PF (401); for example, the characteristic y1 shows a case where the cutoff frequency is low.

Next, the MF adjustment operation will be explained. When the focus changeover switch (12) is activated and the information that the mode has been switched to MF mode is input to the control circuit (5), the control circuit (5) immediately stops the AF operation based on the focus evaluation value y, and switches the MF switch ( 13), MF switch far (14)
accepts the output of That is, near the MF switch (13
) is pressed, the pulse motor (10) is driven via the pulse motor driver (9), and the master lens (104) is moved in a direction to focus on a subject at a short distance. Similarly, when the MF switch far (14) is pressed,
Master lens (10
4) Move.

These MF switches near (13) and M
F switch far (14) is 1 when pressed intermittently.
When pressed twice, the pulse motor (10) rotates by one step. Therefore, the pulse motor (10)
rotates, and the master lens (104) moves by the amount of rotation.

Next, when these MF switch near (13) and MF switch far (14) are pressed down continuously,
The pulse motor (10) rotates at a constant pulse rate,
Operates to move the master lens (104). Therefore, the photographer can adjust the focus according to his/her will.

[0016]

[Problem to be Solved by the Invention] Since the conventional focus adjustment device is configured as described above, it is difficult for the photographer to
When adjusting the focus, the adjustment is often done while observing the EVF. However, this EV
The screen of F is small and the resolution is not sufficient, and it is sometimes difficult to judge whether or not the camera is in focus depending on the shooting situation, the condition of the photographer's eyes, etc. In addition, because the focus lens cannot be moved directly manually, it may take a long time to reach the target, resulting in not being able to record good images or missing photo opportunities. There was a problem that the

[0017] The present invention has been made to solve the above-mentioned problems, and enables accurate MF without being affected by the shooting situation or the condition of the photographer's eyes.
Another object of the present invention is to provide a focus adjustment device that allows even beginners to take good pictures regardless of their handling proficiency.

[0018]

[Means for Solving the Problems] A focus adjustment device according to the present invention includes a lens means for condensing light from an object, and a focusing lens moving means for moving a lens portion of the lens means used for focusing. a photoelectric conversion means for converting the light focused by the lens means into an electric signal; a focus detection circuit for inputting a luminance signal of the electric signal and outputting a focus evaluation value; a delay circuit that delays an output focus evaluation value for a predetermined period; an arithmetic circuit that calculates a difference between the focus evaluation value and a focus evaluation value output from the delay circuit before a predetermined period; Controlling the focusing lens moving means to move the lens portion provided for the focusing, and decelerating the moving speed of the focusing lens when the difference determined by the arithmetic circuit changes from large to small. It is equipped with a control circuit for controlling.

[0019]

[Operation] The focus adjustment device according to the present invention displays the current focus evaluation value on the viewfinder together with the video signal during focus adjustment by manual operation, and also displays the current focus evaluation value on the viewfinder together with the video signal, and also displays the current focus evaluation value when the difference between the focus evaluation value and the focus evaluation value before a predetermined period is large. By slowing down the moving speed of the focusing lens when the focus changes to small, it is possible to quickly and reliably perform highly accurate focusing.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a block circuit diagram showing a focus adjustment device for a camera-integrated VTR as a preferred embodiment of the present invention, and the same parts as those in the conventional device shown in FIG. omitted. In Figure 1, (1
7) is a delay circuit that delays the focus evaluation value y(n) by one field period, and (18) is the current focus evaluation value y(n).
and 1 as the predetermined period output from the delay circuit (17).
The difference from the focus evaluation value y(n-1) before the field period (
This is an arithmetic circuit that calculates the differential coefficient.

Next, the operation of the above embodiment will be explained. When the focus changeover switch (12) operates and the fact that the mode has been switched to MF mode is input to the control circuit (5),
The control circuit (5) stops the AF operation, and the display circuit (15)
through the EVF (16) to the current focus evaluation value y
(n) is expressed numerically as shown in FIG. The position of the master lens (104) at this time is shown in FIG. 6 (a).
If this is the case, the display on the EVF (16) will be as shown in FIG. 2(a).

Next, when the photographer presses either the MF switch near (13) or the MF switch far (14) to find the focal point (in this case, it is assumed that the focal point is in the close direction), Even if you press the MF switch far (14), the focus cannot be obtained, so when you press the MF switch near (13), it will eventually come into focus (Figure 2 (b)) and go too far (Figure 2 (c)) . The EVF (16) display at this time is as shown in FIG. 2(b) and FIG. 2(c), respectively.

The photographer can visually and quantitatively confirm the increase or decrease in the focus evaluation value y(n) corresponding to the increase or decrease in the contrast of the photographed image, thereby enabling accurate focusing. For example, even if it is difficult to judge which of Figure 2(b) or Figure 2(c) is more in focus depending on the shooting situation, you can check that the focus point has been passed by looking at the focus evaluation value y(n) displayed at the same time. This allows the photographer to press the MF switch far (14) and return the master lens (104) to the position shown in FIG. 2(b).

Next, regarding the amount of overshoot from the in-focus point,
MF switch near (13) or MF switch far (14)
If you keep pressing , the pulse motor (10) will rotate at a constant pulse rate, so even if you try to stop the movement of the master lens (104) at the desired position, it will inevitably end up overshooting. It will become.

Here, the focus evaluation value y(n) is also input to the delay circuit (17) and delayed by one field period. The arithmetic circuit (18) subtracts this one-field delayed output y(n-1) from the focus evaluation value y(n) to obtain the sequential differential coefficient K (=y(n) - y(n-1)). ing. Since the focus evaluation value y(n) depicts the characteristics of a mountain with respect to the movement of the focus lens, the differential coefficient K becomes smaller as it approaches the in-focus point, and its sign reverses (becomes a negative value) when it passes the in-focus point. .

If the MF switch near (13) or MF switch far (14) is kept pressed down, the pulse motor (10
) continues to rotate at the same pulse rate, so it is possible to go past the in-focus point all at once. Therefore, in such a case, by monitoring the differential coefficient K and lowering the pulse rate of the pulse motor (10) when K changes from large to small, the rotation of the pulse motor (10) can be reduced. This prevents the speed from going too far due to deceleration, which improves usability.

[0027] In the above embodiment, an example was shown in which the numerical value of the focus evaluation value obtained by the video AF method is displayed as it is at the upper right corner position on the EVF, but the display position may be at any other position. It has a similar effect. In addition, the display format may be not the focus evaluation value itself, but may be a peak indicator, for example, with exactly the same effect. In addition, the following various modifications are possible.

(1) Instead of the focus evaluation value, the ratio of the two focus evaluation values with different characteristics Y1 and Y2 shown in FIG.
A similar numerical value obtained from two or more focus evaluation values may be used.

(2) Two M as means for realizing MF
Although the example using the F switch has been shown, other means may be used.

(3) Although the present embodiment shows the case of one field as the period for delaying the focus evaluation value, this may be another period, such as one frame.

(4) A DC motor may be used as long as it has the positional accuracy and stopping accuracy necessary for the focus motor, and in that case, lowering the applied voltage corresponds to lowering the pulse rate.

[0032]

[Effects of the Invention] As described above, according to the present invention, the MF
The system is configured to calculate the difference (differential coefficient) between the current focus evaluation value obtained by the video AF method and the focus evaluation value a predetermined period ago, and control the rotational speed of the focus motor according to the change in the differential coefficient. Therefore, it is possible to quickly and reliably perform highly accurate focusing without being affected by the shooting situation or the condition of the photographer's eyes during MF, and even beginners can take good pictures regardless of their handling proficiency. This improves usability.

[Brief explanation of drawings]

FIG. 1 is a block circuit diagram showing a focus adjustment device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of the operation of a focus adjustment device according to an embodiment of the present invention.

FIG. 3 is a block circuit diagram showing a conventional focus adjustment device.

FIG. 4 is a waveform diagram showing internal signals of the focus detection circuit.

FIG. 5 is a diagram showing a focus detection area.

FIG. 6 is a characteristic diagram of focus evaluation values with respect to focus lens positions.

[Explanation of symbols]

(1) Inner focus zoom lens (lens means) (2) CCD (photoelectric conversion means) (3) Camera signal processing circuit (4) Focus detection circuit (5) Control circuit (16) Viewfinder (EVF) (17)
Delay circuit (18) Arithmetic circuit

Claims (1)

[Claims] 1. A lens means for condensing light from an object, a focusing lens moving means for moving a lens part of the lens means used for focus alignment, and an electrical system for transmitting the light condensed by the lens means. A photoelectric conversion means for converting into a signal, a focus detection circuit for inputting the luminance signal of the electric signal and outputting a focus evaluation value, and a delay circuit for delaying the focus evaluation value output from the focus detection circuit for a predetermined period. and,
an arithmetic circuit that calculates a difference between the focus evaluation value and a focus evaluation value outputted from the delay circuit a predetermined period ago; and a control circuit that moves a lens portion that is controlled by the arithmetic unit and controls a speed of movement of the focusing lens to reduce when the difference determined by the arithmetic circuit changes from large to small.