JPH0553040A - Lens position detecting device - Google Patents

Abstract

PURPOSE:To further secure the corresponding relation of a lens position and a lens position holding means for holding the lens position as position data. CONSTITUTION:The device is provided with a lens position holding means for holding a lens position to a first reference position of a lens group 2 as position data, a first detecting switch 5 for detecting a fact that the lens group 2 reaches a first reference position and generating a first detecting signal, and a second detecting switch 6 for detecting a fact that the lens group 2 reaches a second reference position and generating a second detecting signal. In such a state, at the time point when a first detecting signal is generated, the held position data is updated by first reference position data for showing a fact of being a first reference position, and at the point of tome when a second detecting signal is generated, the held position data and second reference position data for showing a fact of being a second reference position are compared, and when there is a difference exceeding a prescribed value, the held position data is updated by second reference position data for showing a fact of being a second reference position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens position detecting device,
In particular, the present invention relates to a lens position detecting device in a lens system that has a function of varying magnification and that changes an image forming position according to a focal length.

[0002]

2. Description of the Related Art Focusing systems used in video cameras and the like are a front lens system using a lens group at the frontmost portion (position farthest from an image pickup device) and a rear lens system other than that depending on the type of lens to be moved. There is a so-called inner method using groups. The major difference between these two methods is the behavior in the zooming operation that changes the focal length.

In the front lens system, a mechanism such as a cam is generally used, so that a focus shift due to a zoom operation does not occur even when the focusing lens unit is fixed. On the other hand, in the inner method, for example, as shown in Japanese Patent Publication No. 52-15226 (G02B7 / 14), it is necessary to move the focusing lens group along with the zoom operation in order to maintain the focus. Become.

In this inner method, in order to maintain the focus during zooming, the focusing lens is moved along the curve of FIG. This FIG. 4 shows the focusing lens position (horizontal axis) for focusing on an object whose subject distance (distance between camera and subject) is infinity and 1 m at each focal length (vertical axis). When the zoom is shifted to the wide-angle side during shooting of a subject in focus at the telephoto side where the subject distance is infinity, the focusing lens needs to be displaced along the curve L1. is there. Similarly, it indicates that a subject having a subject distance of 1 m must be displaced along the curve L2.

In the above-mentioned inner method, it is necessary to know the focal length at the start of zooming and the position of the focusing lens in order to make the focusing lens follow the curve of FIG. 4 when maintaining the focus. Therefore, generally, regarding the focal length, a mechanism using a potentiometer linked to the focal length and knowing its absolute position by a voltage value is used. Further, with respect to the focus lens position, a pulse is generated with the movement of the lens, and the position of the lens can be known by counting this with a counter. It is also possible to count in open loop using a stepper motor.

By the way, when counting the above-mentioned pulses, it is indispensable to set the reference position for resetting the counter. Normally, a switch for detecting the reference position is used, and a signal is sent when the lens reaches a predetermined position. To reset the counter.

On the other hand, in order to prevent the lens from being driven beyond the mechanical limit due to the movement of the focusing lens accompanying the focusing operation, the reference position detection switch is an end point switch indicating the movable limit of the focusing lens. Often used as

[0008]

In the prior art, the position of the focusing lens and the value of the counter are reset in response to a signal from the reference position detecting switch, and a one-to-one correspondence is secured. However, if the state where the focusing lens does not move and the focusing operation is performed continues for a long time at the position where the reference position detection switch is located, the position of the focusing lens and the value of the counter have a one-to-one correspondence due to mechanical play. There is a problem that it does not become.

It is an object of the present invention to make the correspondence between the lens position and the lens position holding means for holding the lens position as position data more reliable.

[0010]

In order to solve the above problems, the present invention provides, as a lens position detecting device, lens position holding means for holding the lens position of a lens group with respect to a first reference position as position data, and the lens. A first detection switch that detects that the group has reached the first reference position and issues a first detection signal; and a first detection switch that detects that the lens group has reached the second reference position and issues a second detection signal. 2 detection switch and 1st updating the position data held by the lens position holding means with the 1st reference position data indicating the 1st reference position when the 1st detection signal is issued The updating means and the position data held by the lens position holding means at the time when the second detection signal is issued are compared with the second reference position data indicating the second reference position to determine a predetermined value. The second if there is a difference more than updating in the second reference position data indicating the second reference position the position data held in the lens position holding means
And an updating means are provided.

In particular, it is assumed that the lens group has a function of varying the magnification and performs focusing control in the lens system in which the image forming position changes according to the focal length.

[0012]

Since the present invention is configured as described above, the position data held by the lens position holding means can be stored as necessary even when the lens group is located not only at the first reference position but also at the second reference position. Will be updated.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a functional block diagram of a lens position detecting device according to the present invention. In the figure, reference numeral 1 is a lens group having a zoom function, 2 is a focusing lens having a focusing function, 3 is a zoom motor for displacing the lens group 2 in the optical axis direction, and 4 is a focusing lens. A focus motor 5 for displacing 2 in the optical axis direction, a first position detection switch 5 for detecting that the focusing lens has reached a first reference position, and a reference numeral 6
Is a second position detection switch for detecting that the focusing lens has reached the second reference position.

Further, 7 is a solid-state image pickup device for converting incident light imaged through each lens group into an electric signal, and 8 is a signal processing circuit for forming an electric signal obtained from the solid-state image pickup device 7 into a video signal. , 9 are focus evaluation value generation circuits for outputting a focus evaluation value serving as a criterion for determining the degree of focusing using the video signal. Specifically, as shown in FIG. 3, the focus evaluation value generation circuit 9 inputs the video signal output from the signal processing circuit 8 and outputs the brightness in the focus area arranged in the center of the image pickup screen. A focus area extraction circuit 90 that extracts only the signal in a time division manner, an HPF 91 that extracts only the high frequency component of this output, and an integrator 92 that integrates one field of the output of this HPF 91 and outputs it as a focus evaluation value. The microcomputer 10 drives and controls the focus motor 4 so as to move and stop the focusing lens 2 to a position where the focus evaluation value sequentially output from the integrator 92 for each field at the time of the focusing operation has the maximum value. Signal is supplied. The above-described focusing operation based on the principle that the high-frequency component of the luminance signal becomes maximum in the focused state is a technique known as a so-called hill-climbing autofocus method.

Reference numeral 11 denotes a potentiometer for detecting a focal length, that is, a zoom area from the position of the lens group 1 in the optical axis direction, and specifically, a conductive contact piece 11 interlocking with the lens group 1.
a, a power supply voltage + B, and a resistor 11b inserted between the ground, and the contact piece 11a is displaced in conjunction with the lens group 1 to change the voltage at this contact piece.
The voltage value is applied to 0 to detect the telephoto to wide-angle zoom area based on this voltage value.

The counter 12 detects the rotation state of the focus motor 4, and issues N rotation detection pulses for one rotation of the motor and a signal indicating the rotation direction (near point direction or far point direction). In response to the output from the rotation detector 13 attached to the focus motor 4, the rotation detection pulse is counted up when the rotation direction is the direction to move the focusing lens 2 to the near point direction, and conversely moves to the far point direction. When it is in the direction to make it, the rotation detection pulse is counted down, and this count value is supplied to the microcomputer 10 as the current lens position of the focusing lens 2. The comparator 14 will be described later.

The relationship between the first position detection switch 5, the second position detection switch 6 and the focusing lens 2 is configured as shown in FIG. That is, the focusing lens 2 is attached to the ring 15, the rack portion 16 extending in the optical axis direction is fixed to the upper side of the ring 15, and the pinion gear 17 driven by the focus motor 4 so as to be capable of forward and reverse rotation is provided. Rack 16
When the pinion gear 17 is rotated by the focus motor 4, the focusing lens 2 advances and retracts integrally with the rack portion 16 and the ring 15 in the optical axis direction to perform the focusing operation. Also, a contact piece 18 is provided below the ring 15.
Is fixed, and a first position detecting switch 5 and a second position detecting switch 6 are provided in the movement path of the contact piece 18.

The first position detection switch 5 is a conductive contact piece 5.
When the focusing lens 2 reaches the switch position, the contact piece 18 contacts the contact piece 5b and elastically deforms the contact pieces 5a, 5b. Conductive, and at the same time as this contact, the first position detection switch 5
The counter 12 is pulsed. Where the first
The position detection switch 5 is attached to the chassis 20 by inserting a screw 22 into a through hole 19a formed in the integrally formed mounting portion 19 and a groove 21 provided in the chassis 20 so as to extend in the optical axis direction. Screwed and fixed, but screw 22
If is removed, it is possible to move the focusing lens 2 in parallel with the optical axis direction. That is, the first reference position, which is the position of the first position detection switch 5, is the movable limit position of the focusing lens 2, and is movable for the purpose of absorbing an error in manufacturing the optical mechanism.

The second position detection switch 6 is located substantially at the center of the movable range of the focusing lens 2, and when the contact piece 18 passes over the movable portion 6a, the contact piece 18 pushes the movable portion 6a in the direction of arrow A. , The switch is turned on, and the comparator 14 shown in FIG.
Is pulsed. The first position detection switch 5
Since the second position detection switch 6 and the second position detection switch 6 are connected by the connecting means 23, the second reference position is also adjusted by adjusting the first reference position.

Next, the operation of correcting the value of the counter 12 by the first position detection switch 5 and the second position detection switch 6 will be described with reference to FIG.

When the focusing lens 2 reaches the first reference position,
A pulse is generated from the first position detection switch 5, the pulse is input to the reset terminal 12a of the counter 12, and the counter 12 is reset. The first reference position value is the movable limit position of the focusing lens 2, and is the reference position at which the counter 12 indicating the position of the focusing lens 2 starts counting. Normally, when the power of the entire apparatus is turned on, the focusing lens 2 is once moved to a first reference position, that is, a movable limit position, a pulse is generated by the first position detection switch 5, and the counter 12 is reset. Subsequently, the focusing lens 2 is moved to the second reference position, a pulse is generated by the second position detection switch 6, and the value of the counter 12 at that time is the value M originally indicated by the counter 12 at the second reference position. Is held in the comparator 14. Therefore, when starting to use the device, the focusing lens 2
And the value of the counter 12 have a one-to-one correspondence.

When the focusing lens 2 reaches the second reference position, a pulse is generated from the second position detection switch 6 and the pulse is input to the comparator 14. The comparator 14 compares the value X of the counter 12 at the time when the pulse is input with the value M that the counter 12 should originally show at the second reference position, and the difference between them is a predetermined value, for example, the number M. When it is more than%, the counter 12 is preset to the value M. That is,
Unlike the operation by the first position detection switch 5, the counter 12 is preset as necessary. Therefore,
For example, when the position where the high-frequency component of the luminance signal is maximum, that is, when the focus position is detected and then the focus lens 2 is moved to that position, the preset focus position changes and the focus position is accurately adjusted. It reduces the occurrence of problems such as not getting rushed.

[0024]

As described above, according to the present invention, the lens position data is corrected not only at the first reference position but also at the second reference position, so that the lens position and the lens position are held as position data. The correspondence with the lens position holding means can be made more reliable, and the effect is great.

[Brief description of drawings]

FIG. 1 is a circuit block diagram of an embodiment of the present invention.

FIG. 2 is a diagram illustrating a positional relationship between a reference position detection switch and a lens.

FIG. 3 is a block diagram of a main circuit of FIG.

FIG. 4 is a diagram showing a relationship between a lens position and a zoom area.

[Explanation of symbols]

 2 Focusing lens 4 Focus motor 5 First position detection switch 6 Second position detection switch 12 Counter 13 Rotation detector 14 Comparator

Claims (2)

[Claims] 1. A lens position holding means for holding, as position data, a lens position of a lens group with respect to a first reference position, and a first detection signal is generated by detecting that the lens group has reached the first reference position. A first detection switch, a second detection switch that detects that the lens group has reached a second reference position and issues a second detection signal, and the lens position hold at the time when the first detection signal is issued. First updating means for updating the position data held by the means with the first reference position data indicating the first reference position, and the lens position holding means at the time point when the second detection signal is issued. The position data held by the lens position holding means is compared with the second reference position data indicating the second reference position. 2 units And a second updating unit that updates with second reference position data indicating a quasi-position. 2. The lens group has a function of varying the magnification, and performs focusing control in a lens system in which an image forming position changes according to a focal length. Lens position detection device.