JPH05181048A - Optical equipment - Google Patents

Abstract

PURPOSE:To detect the absolute position of a moving lens in a short time and to shorten the rising time of a system in focusing operation. CONSTITUTION:Detection mechanisms 14 and 15 for detecting the reference position of a lens L1 are provided at plural places in the optical equipment where the lens L1 is moved by a stepping motor 12 as a driving source, and a position detecting means 16 for detecting the absolute position of the lens L1 based on the number of steps of the stepping motor 12 from the reference position is also provided in the optical equipment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device for detecting the absolute position of a moving lens for focusing, zooming or the like.

[0002]

2. Description of the Related Art Conventionally, in the one in which a focus lens for a silver halide camera or a video camera is driven by a stepping motor, the position detection of the focus lens group is obtained by the step number of the stepping motor, and the open control is performed based on this step number. In order to do so, it is necessary to detect the absolute position that serves as a reference when the power is turned on or when the system is restarted. Generally, a detection device for detecting a position is provided with a non-contact type such as a photo sensor or a contact type such as a leaf switch in a moving stroke of the focus lens, and the focus lens group directly detects these sensors. , Switch on, off to detect.

[0003]

However, in the above-mentioned conventional example, in order to detect the reference position of the focus lens group in the shortest time regardless of the position of the focus lens group, , It is desirable to place the focus lens group at the center position of the moving stroke. However, there is a drawback in that the time required to detect the reference position becomes longer as the movement stroke of the focus lens group becomes longer.

Further, in the above conventional example, when plastic is used for the lens structure, expansion and contraction occur due to temperature change, but if there is only one position for detecting the reference position of the focus lens group, the focus lens group It was impossible to detect that the lens barrel is changing focus when the lens barrel expands or contracts due to temperature change while driving the stepping motor.

[0005]

SUMMARY OF THE INVENTION The present invention is an optical device for moving a lens using a stepping motor as a drive source, and a plurality of detecting mechanisms for detecting the reference position of the lens are provided at a plurality of positions, It is characterized by an optical device provided with position detecting means for detecting the absolute position of the lens based on the number of steps of the stepping motor, and makes it possible to detect the absolute position of the moving lens in a short time. ..

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIG. In this embodiment, a case where the movement amount of the focus lens group is divided into three will be described.

Reference numeral 11 denotes a lens holding cylinder of the focus lens group L1, and reference numerals 11a and 11b denote photosensors 14 and 1.
5 is a light-shielding plate as an operating member for turning on-off 5. The lens holding cylinder 11 is a rack 1 that is fitted with a feed screw.
1c, the feed screw 12a protruding from the stepping motor 12 serving as an actuator meshes with the rack 11c, and the lens holding cylinder 11 is guided by the guide bar 17 at the U groove 11d so that its rotation is restricted. It can move only in the direction. Therefore,
When the motor 12 is driven and the feed screw 12a is rotated,
The lens holding cylinder 11 for focusing can be moved in the optical axis direction to perform the focusing action by the focus lens group L1. Reference numerals 14 and 15 denote photosensors for detecting the reference position of the focus lens unit L1, and the light shield plate 11a.
Alternatively, 11b is moved to the position of the photosensor 14 or 15 to block light, thereby detecting that the focus lens group L1 has reached the reference position. Reference numeral 16 is a printed circuit board on which circuit means including a microcomputer μm for controlling the motor 12 and the photosensors 14 and 15 and detecting the absolute position of the focus lens group L1 is mounted.

FIG. 2 shows zone division of the movement stroke of the focus lens unit L1 of the embodiment. In this embodiment, the photosensors 14 and 15 are used to divide into three zones.

FIG. 3 shows a control circuit of the embodiment, in which outputs from the two photosensors 14 and 15, the power switch 17 and the focus detection device are input to the microcomputer μ-com, and based on the information. The drive (forward / reverse rotation) of the motor 12 is controlled by program control.

FIG. 4 shows the microcomputer μ-c of FIG.
It is a flowchart showing the om control, and the operation of lens position detection will be described below.

When the power switch 17 of the system changes from the off state to the on state (ST1), the photo sensor 1
Check the state of 4, 15 (ST2, ST3, ST6)
When the photo sensor 14 is shielded from light and the photo sensor 15 is not shielded, it is determined to be in the zone 1 shown in FIG. 2, the motor 12 is rotated, and the focus lens group is moved in the object side optical axis direction (ST4). ). When the photo sensor 14 detects a switching point that has moved to a point where light blocking and transmission switch (ST5), the motor is stopped (ST12) and a reference position as an absolute position is detected (ST13). When the photo sensor 15 is shielded and the photo sensor 14 is not shielded, it is determined that the zone is in zone 3, the motor 12 is rotated in the opposite direction to step 4, and the focus lens group is moved in the optical axis direction on the image formation side. (ST7). Then, when the photo sensor 15 detects a switching point that has moved to a point where light blocking and transmission switch (ST8), the motor is stopped in the same manner (ST12) to detect the reference position (ST1).
3). When both the photo sensors 14 and 15 are not shielded from light, it is determined that they are in the zone 2, and the motor 12 is rotated in any direction to move the focus lens group in the image forming side or the object side optical axis direction (ST9). .. And
When the photosensor 14 or the photosensor 15 detects a switching point that has moved to a point where light blocking and transmission switch (ST10, ST11), the reference position is detected (ST13). When the reference position is detected, that state, that is, which photosensor 14 or 15 position the reference position is detected is stored. Thereby, when driving the motor 12 for the focusing operation based on the output from the focus detection device 18 thereafter, the focus lens group L1 is calculated by calculating the driving step number of the stepping motor 12 from the stored reference position. The absolute position of is detected (ST15).

Next, a second embodiment will be described with reference to FIG.

The second embodiment shows another example of the reference position detecting structure, and the other structure and operation flowchart are the same as those of the first embodiment. Reference numerals 54 and 55 are leaf switches as a reference position detecting structure, which are turned on and off by the movement of the projecting portions 51a and 51b as operating members.

Next, a third embodiment will be described with reference to FIG.

The third embodiment is a microcomputer μ-c.
8 shows another control flow chart of om, and the other configurations are the same as those in the above-described first embodiment.

In the flowchart of FIG. 6, steps 1 to 14 are the same operations as in the first embodiment,
The description is omitted.

When the focus operation for driving the stepping motor 12 to obtain the focus based on the output of the focus detection device 18 is being executed (ST16), the drive pulse of the stepping motor 12 is always counted (ST1).
7). At the time of counting the number of pulses, the actual number of counts between the two reference positions is compared with the number of stored pulses (the value stored in the memory in the microcomputer μ-com), and if they do not match, Stepping motor 1
The drive characteristic of No. 2 is changed (ST19). The change in the drive characteristic is to increase the drive voltage or delay the cycle of the drive step to improve the pulse followability. Unless the power switch 17 is turned off (ST20),
The focus operation is continued.

Next, a fourth embodiment will be described with reference to FIG.

The fourth embodiment is a microcomputer μ-c.
8 shows another control flow chart of om, and other configurations are the same as those in the first embodiment.

In the flowchart of FIG. 6, steps 1 to 14 are the same operations as in the first embodiment,
The description is omitted. The steps 16 to 18 are the same as those in the third embodiment.

In the fourth embodiment, if the actual count number and the stored pulse number do not match, it is determined that the dimensional change of the component has occurred due to the temperature change (ST21). In step 21, how much the actual count number and the stored pulse number are deviated is stored, and the drive characteristic change of the stepping motor 12 is executed according to the deviated amount (ST22). The change of the drive characteristic means that the number of drive pulses of the stepping motor 12 is corrected (increased or decreased) in order to obtain the focus early or to maintain the focus even if the temperature changes. .. The amount of this correction naturally depends on the temperature, so
It is determined based on the shift amount stored in step 21.
This operation continues unless the power switch 17 is turned off (ST23).

In the above embodiments, the focus lens group is described as an example of the moving lens, but it goes without saying that it may be a zoom lens group. Also, as a reference position detection mechanism,
Mechanisms other than those shown in the embodiments, for example, magnetic sensors can be used. Also, various arrangements of the detection mechanism can be naturally performed.

[0023]

According to the present invention, the detection mechanism for detecting the reference position of the moving lens is provided at a plurality of positions, and the absolute position of the lens is detected based on the step number of the stepping motor from the reference position. By doing so, the time for detecting the position of the moving lens can be shortened. Therefore, in a system in which the movable lens is first moved to the reference position when the power is turned on and then the normal focusing operation is performed, the system start-up time can be shortened.

Further, by storing a value corresponding to the amount of movement between the reference positions, comparing the stored value with the actual step number of the stepping motor, and changing the drive characteristic of the motor when there is a difference, It is possible to reduce the operation error of the moving lens such as focus shift.

A value corresponding to the amount of movement between the reference positions is stored, the stored value is compared with the actual number of steps of the stepping motor, and when there is a difference, the dimensions of the parts are changed due to temperature change. By making a judgment and changing the drive characteristic of the stepping motor, it is possible to accurately move the lens.

[Brief description of drawings]

FIG. 1 is a perspective view of a lens moving mechanism as a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing zone division of a moving stroke of the focus lens group in FIG.

FIG. 3 is a circuit configuration diagram of an embodiment.

FIG. 4 is a flowchart showing a lens position detecting operation of the first embodiment.

FIG. 5 is a perspective view of a lens moving mechanism as a second embodiment.

FIG. 6 is a flowchart as a third embodiment.

FIG. 7 is a flowchart as a fourth embodiment.

[Explanation of symbols]

 L1 focus lens group 11 lens holding cylinder 12 stepping motor 14 photo sensor 15 photo sensor μ-com microcomputer 54 leaf switch 55 leaf switch

Claims (3)

[Claims] 1. An optical device for moving a lens using a stepping motor as a drive source, comprising position detecting means for obtaining the absolute position of the lens by the number of steps of the stepping motor from a reference position. The detection means is provided with a plurality of detection mechanisms for detecting the reference position of the lens, and is an optical device. 2. The optical device according to claim 1, further comprising a comparison means for storing a value corresponding to a movement amount between the detection mechanisms at the plurality of locations and for comparing the stored value with the number of steps. machine. 3. The optical device, wherein the position detecting means detects a temperature change by comparing the number of moving steps between the detecting mechanisms at the plurality of places with the stored value.