JPH06281852A - Lens driving device - Google Patents

Abstract

PURPOSE:To prevent a deviation of control and hitting against a mechanical end by providing a means for detecting and stopping a real movable end set electrically before a moving lens group hits against the mechanical end, also, informing that reset is necessary again, when it is decided that a deviation is generated in position control of an electrical end. CONSTITUTION:In a moving ring 2, a first light shielding member 2a and a second light shielding member 2b are provided separately along the optical axis direction, and as the moving ring 2 moves, a detecting signal is outputted from a first photosensor 7 and a second photosensor 8. The first light shielding member 2a is arranged to a reset position of the lens movement from a mechanical movable range end in the front end side of the lens movement, and the second light shielding member 2b is arranged in the front and the rear ends in a movable range of a lens, and to a position for stopping forcibly a stepping motor 6. In such a state, by pulse signal for moving a moving lens group 1, it is driven from the reset position to a prescribed position, a pulse signal of a prescribed number of pulse signals is counted, and when it reaches the prescribed number, driving is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens driving device for an optical apparatus, and more particularly to a lens driving device for driving a lens by a stepping motor such as a video camera.

[0002]

2. Description of the Related Art In a conventional lens driving device, when a stepping motor is used as a driving source for moving a lens group along the optical axis direction, the starting position of the stepping motor is detected within the lens moving range. The lens driving is performed from the starting point by open loop control.

[0003]

Conventionally, in the case of open loop control by a stepping motor, the stop at the end of the moving lens group depends only on the number of drive steps electrically detected from the starting point, so that some kind of impact is generated. If the lens group position becomes incorrect due to, the moving end of the lens group also becomes incorrect and hits the end including the mechanical allowance provided before electrically stopping, and it is impossible to drive in the reverse direction from that position. May be Further, although the drive in the reverse direction is possible, there is a risk that the control may be performed with the starting position being wrong.

It is an object of the present invention to eliminate the above hazards and to provide an improved lens driving device.

[0005]

According to the present invention, the moving movable lens group detects and stops an electrically movable actual movable end before hitting the mechanical end, and when the electric end is detected. When it is determined that the position control is out of order, a means for notifying that the reset is necessary again is provided to prevent the out of control from hitting the mechanical end.

[0006]

1 is a perspective view of a mechanical structure portion showing an embodiment of a lens driving device according to the present invention.

Reference numeral 1 denotes a moving lens group held by a moving ring 2.
Reference numeral 3 denotes a guide bar for supporting the movement of the movable ring 2 in the optical axis direction. Reference numeral 4 denotes a guide bar for the movement of the movable ring 2 in the optical axis direction, and prevents the guide bar 3 from swinging about the guide axis 3. It's a bar.

A stepping motor 6 drives the moving ring 2 in the optical axis direction, and a feed screw 9 is attached to an output shaft (not shown). Reference numeral 5 denotes a nut member provided integrally with the moving ring 2, which is screwed to the feed screw 9, and is screwed forward or backward by driving the motor 6 with a driving force to move the moving lens together with the moving lens 2. The group 1 is moved along the optical axis direction.

The movable ring 2 is provided with a first light-shielding member 2a and a second light-shielding member 2b which are spaced from each other along the optical axis direction, and with respect to the first light-shielding member 2a and the second light-shielding member 2b. Known first photosensor 7 and second photosensor 8 are arranged, and detection signals are output from these first photosensor 7 and second photosensor 8 as the movable ring 2 moves. There is.

FIG. 2 is a schematic diagram of a control system of the lens driving device of this embodiment.

In the figure, reference numeral 20 is a control device composed of, for example, a microcomputer, 21 is a motor drive circuit for controlling the energization of the stepping motor 6, and the control device 20 is a zooming operation such as zooming or widening operation.
Alternatively, when a command for autofocus is input, a drive signal having a pulse number corresponding to the command is output to the stepping motor 6 to drive the moving lens group 1 stepwise. Reference numeral 22 denotes an electronic viewfinder (EVF: Electronic _/ Vie) provided in an optical device such as a camera.
w _· Finder) is a display device control circuit.

The control device 20 digitally converts the detection signals, which are analog signals from the first photosensor 7 and the second photosensor 8, into a signal of "1" when they are blocked by the respective light shielding members. Is converted into a signal of "0" when not blocked by each of the light shielding members.

In the present embodiment, the first light blocking member 2a and the second light blocking member 2b are entirely non-translucent in the length direction, and the first light blocking member 2a is located on the front end side of the lens movement. It is arranged from a mechanical movable range end (hereinafter referred to as a mechanical end) to a position corresponding to a reset position of lens movement, and the second light blocking member 2b is a front and rear end in the movable range of the lens and forces the stepping motor 6 It is arranged up to a position corresponding to a position for mechanically stopping (hereinafter referred to as an electronic stopper).

Therefore, when the movable lens group 1 is present at the front mechanical end, the first photosensor 7 is blocked by the first light blocking member 2a, outputs a signal "1", and the second photosensor 8 is the first. 2 Since it is not blocked by the light blocking member 2b, a signal of "0" is output. FIG. 3 shows the relationship between the signal from the photosensor and the lens position.

In FIG. 3, when the movable ring 2 is located between the front end electronic stopper and the front mechanical end, the second ring
“0” from the photo sensor 8, the first photo sensor 7
Outputs a signal of "1" from "01", and when it is located between the front end electronic stopper and the reset position, it outputs a signal of "1" to both "11", and the reset position and the rear side electron. When it is located between the stopper position and the stopper position, a signal of "1" is output from the second photo sensor 8 and a signal of "0" is output from the first photo sensor 7 and "10", which is the rear electronic stopper position. When it is located between the rear side mechanical end, both outputs the signal of "0" and "00".

When a signal for moving the moving lens group 1 is input, the control device 20 outputs a predetermined number of pulse signals in the forward direction or the reverse direction to move the moving lens group 1 from the reset position to the predetermined position. To drive. Then, if the predetermined number of pulse signals is the number of pulses up to the electronic stopper position,
The number of pulses is counted, and when the number reaches a predetermined number, driving is stopped.

Here, the moving lens group 1 becomes abnormal due to a shock or the like in the screwing relationship between the feed screw 9 and the nut member 5,
For example, when the displacement of the moving ring 2 corresponding to the amount of movement corresponding to several steps occurs on the mechanical end side, it should be possible to stop the driving at the electronic stopper position by counting the driving pulse, but the movement exceeds the electronic stopper position. The ring 2 may move to the mechanical end.

When the moving ring 2 crosses the mechanical end, the signal "0" is output from the second photo sensor 8, so that it can be judged that there is an abnormal state, but only the signal from the second photo sensor 8 is present. Then, it is not possible to determine whether the mechanical end on the front side or the mechanical end on the rear side is approached, and even if the movable lens group 1 is returned to the reset position, the forward or reverse direction with respect to the stepping motor 6 is not detected. I can't judge whether to turn on the power.

However, by adding the signal from the first photo sensor 7, it becomes possible to judge whether or not the front mechanical end is approached, and the movable lens group 1 can be returned to the reset position.

Therefore, when the mechanical stopper side is dislocated from the electronic stopper position, the lens drive is forcibly stopped, the photographer is notified of this through the display on the EVF, and the photographer is informed of the reset position of the movable lens group 1. It is possible to prompt a return operation by a manual operation, and by turning off the main switch of the camera and turning on the main switch again, the moving lens group 1 is automatically set to the reset position,
It is possible to take a picture without any abnormality.

In resetting, when returning from the mechanical end on the front side to the reset position, since the reset position is when the signals from both photosensors are switched from "11" to "10", the energization should be stopped there. become.

FIG. 4 is a flow chart showing the control operation by the control device 20 described above.

It is determined whether the detection information of the first photo sensor 7 and the second photo sensor 8 is "01" or "00", and the driving pulse number is calculated from the reset position shown in FIG. If the pulse count is a value that reaches the electronic stopper position when it is out of the stopper position, the driving is stopped at the electronic stopper position (step 1).

However, even though the counted pulse (which counts the number of pulses generated in the driving circuit) has not reached the value corresponding to the electronic stopper position, the second photosensor 8 and the first photosensor 7 The signal is "01"
Alternatively, if it is "00", it is determined that an abnormal state has occurred, and the process proceeds to step 2.

In step 2, the stepping motor 6
Whether or not to forcibly stop the driving is displayed in the EVF to notify the resetting, and the photographer is prompted to perform the resetting operation. Here, by performing the re-reset operation, the movable lens group 1 can return to the reset position and take an image again without trouble.

In this embodiment, in order to reduce the power consumption due to the constant energization of the sensor during signal detection, position detection is performed within the interval between the maximum electronic stopper and the mechanical end (mechanical maximum movable end). I have to.

[0027]

In the lens driving device of the present invention, the electric stopper position can be confirmed by adding one reset switch to the conventional lens driving device, and the open loop control by the stepping motor is used. In the vicinity of the movable end, feedback control can be performed by detecting the end by detecting a signal.

Further, the risk of the lens colliding with the mechanical end can be eliminated.

[Brief description of drawings]

FIG. 1 is a diagram showing a mechanical structure of an embodiment of a lens driving device according to the present invention.

FIG. 2 is a schematic diagram of a control system of the lens driving device of the present invention.

FIG. 3 is a diagram showing signals generated in a sensor within a lens movement range in the lens driving device of the present invention.

FIG. 4 is a diagram showing a part of a control operation performed by a control device of the lens driving device of the present invention.

[Explanation of symbols]

1 ... Moving lens group 2 ... Moving ring 3 ... Guide bar 4 ... V bar 5 ... Nut member 6 ... Stepping motor 7 ... Sensor 8 ... Sensor 9 ... Feed screw

Claims (4)

[Claims] 1. A drive means for driving a lens that is movable in a mechanical movable range, an actual movable end position of the movable lens set in the mechanical movable range, and the mechanical movable range. Lens position detecting means for detecting at least an end position, and control means for stopping driving of the driving means when the lens position detected by the lens position detecting means is located between the actual movable end and the mechanical movable end. A lens driving device comprising: 2. The lens driving device according to claim 1, wherein the lens position detecting means is capable of discriminating between the front movable side and the rear movable side in the range of the actual movable end and the mechanical movable end. 3. The control means according to claim 2, wherein the control means controls the drive means so as to return the movable lens group to the reset position based on the detected range of the actual movable end and the front side or the rear side of the mechanical movable end. A lens driving device characterized by: 4. The notification according to claim 1, 2 or 3, wherein the control means notifies that an abnormality has occurred in position control when the lens position is between the actual movable end and the mechanical movable end. A lens driving device comprising means.