JPH0559415U - Lens drive mechanism with step motor as drive source - Google Patents

Abstract

(57) [Abstract] [Purpose] To reduce the maximum focusing delay time of the lens driving mechanism driven by the step motor. [Structure] The rotation of the step motor 1 is transmitted through a transmission mechanism 4 to drive a lens system 5. When the main switch 12 is turned on, the lens system 5 is driven to a position where the second detecting means for detecting the intermediate position is operated, and the shutter operation is waited at that position, so the maximum value of the focusing delay time is about 1 /.
Shortened to 2. Main switch 12 in this standby state
Since the lens system returns to the position where the first detecting means for detecting the initial position is activated when the switch is turned off, the lens system is retracted during carrying and the portability does not deteriorate.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a lens driving mechanism using a step motor as a driving source, and relates to a lens driving mechanism most suitable for a still camera.

[0002]

[Prior Art]

 In recent years, as a lens drive mechanism for still cameras, a mechanism that uses a step motor as a drive source and drives the lens system to a target position according to the distance measurement result of the object distance measurement mechanism has become widespread. Generally, in this type of mechanism, when the main switch on the camera side is turned on, the lens is retracted into the body as much as possible. For example, when the shutter button is half pressed, the motor is energized to focus the lens system. It is designed to drive to a position.

[0003]

[Problems to be solved by the device]

 However, in recent years, cameras with multifocal lenses including long focal length areas and zoom lenses have become widespread, and it becomes necessary to subdivide the number of lens settings according to the shallow depth of field. ing. For this reason, the conventional mechanism has a problem that the delay time required for the lens system to make the maximum stroke in the half-pressed state of the shutter becomes too long. Of course, even if the number of lens setting steps increases, if the pulse period for driving can be shortened, the delay time can be shortened, but the pulse period is shortened from the viewpoint of motor followability. Is limited. Furthermore, in this type of mechanism, the initial position of the lens system should be set in advance near the midpoint of the effective focus adjustment area, and the lens system should be extended or retracted according to the subject distance. However, if the initial position of the lens system is set near the midpoint of the effective focus adjustment area in this way, the lens system will be extended up to the intermediate shooting distance when the camera is carried. Its portability deteriorates.

[0004]

[Means for Solving the Problems] The present invention has been made in view of such problems, and the focusing movement in a lens driving mechanism using a step motor as a driving source is performed without deteriorating the portability of the camera. It is intended to reduce the maximum delay time for production.

In summary, a lens driving mechanism using a step motor of the present invention as a driving source is a lens system having a step motor capable of rotating in forward and reverse directions and a lens group for photographing as in the case of the conventional mechanism. And a power transmission system that transmits the rotation of the step motor to the lens system, and drives the lens system to the in-focus position by transmitting the rotation of the step motor prior to the operation of the shutter blades. Assuming a lens drive mechanism using a step motor as a drive source, the first detection means for detecting that the power transmission system is in the initial position, and the power transmission system are approximately in the middle of the effective focus adjustment area. And a second detection means for detecting that the first motor is turned off and the step motor is operated to a position where the first detection means operates when the main switch is turned off. The power transmission system is driven, and when the main switch is turned on, the step motor is driven to a position where the second detection means operates, and the power transmission system is driven to stand by. Is.

[0006]

[Action]

 According to the present invention, when the main switch is turned on, the lens system is driven to the vicinity of the intermediate point where the second detection means operates and stands by, so that the maximum delay time for the focusing operation can be shortened. In addition, since the lens system is driven to the initial position where the first detecting means operates when the main switch is turned off, the storability during carrying does not deteriorate.

[0007]

【Example】

 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, FIG. 1 is a mechanism diagram showing the initial state of the present invention in principle. 1 is a step motor capable of forward and reverse rotation by a drive pulse, 2 is an output pinion of the step motor 1, 3 is a two-stage gear, and 4 is The respective cam members are shown. The rotation of the output pinion 2 is transmitted to the cam member 4 via the two-stage gear 3 and the rack 4a formed on the cam member 4, and the cam member 4 travels to the right or left depending on the rotation direction of the output pinion 2. To do.

A lens driving cam 4b is formed on the side of the subject of the cam member 4, and a cam follower 5a formed in the lens system 5 is formed on the lens driving cam 4b by a spring 6 (a spring for simplifying the drawing. 6 indicates the biasing direction only with an arrow.) When the cam member 4 travels to the right in the drawing, the lens system 5 resists the spring 6 and follows the guide member 7. It is extended toward the subject.

Next, 8 is an origin switch for detecting that the cam member 4 is at the initial position. When the cam member 4 is at the initial position, the origin switch 8 is detected by the detection pin 4c formed on the cam member 4. Breaks. In the present embodiment, the origin switch 8 is adjusted so that when the cam member 4 is converted from the initial position into the rotation pitch of the step motor 1 and moved to the right by two steps, it is released from the detection pin 4c to make.

Reference numeral 9 is a photo interrupter in which the optical path is blocked by the detection projection 4d formed on the cam member 4 when the cam member 4 is near the midpoint of its operating area. In the present embodiment, the photo interrupter 9 is adjusted so that the optical path is shielded and turned off when the cam member 4 is in the range corresponding to two steps each from the midpoint of its operating region to the front and back. Further, 10 is a limit switch for detecting the advance end of the cam member 4, and the limit switch 10 breaks by the detection pin 4e formed on the cam member 4 when the cam member 4 reaches the advance end.

Next, FIG. 2 is a block diagram of the control system, in which 1 is the step motor described above, 8 is the origin switch described above, 9 is the photo interrupter described above, and 10 is the limit switch described above. Are shown respectively. Further, reference numeral 11 is a release switch interlocking with the shutter button, and 12 is a main switch. Reference numeral 13 indicates a program control device.

Next, the operation of this embodiment will be described with reference to the above matters, the state explanatory diagrams of FIGS. 3 and 4, the flowcharts of FIGS. 5 and 6, and the time chart of FIG. 7. 3 shows a state in which the cam member 4 is moved near the midpoint, and FIG. 4 shows a state in which the cam member is moved to the advance end.

First, when the main switch 12 of the camera is made, the control device 13 checks whether or not the origin switch 8 is broken. Normally, the origin switch 8 is broken by the detection pin 4c. Therefore, the control device 13 causes the step motor 1 to rotate counterclockwise for two pulses, and the cam member 4 travels to the right in the drawing, and travels for two pulses. Sometimes the origin switch 8 is released from the detection pin 4c and is making. Therefore, if the origin switch 8 breaks at this point, the control device 13 reverses the step motor 1 for two steps and then interrupts the energization to display an error.

On the other hand, if the origin switch 8 is making at this point, the control device 13 monitors the photo interrupter 9 and rotates the step motor 1 counterclockwise by 4 pulses to move the cam member 4 to the right. When the cam member 4 corresponding to 1/2 of the total number of steps in the effective focus adjustment area of the lens system travels to the right, the photo interrupter 9 is shielded from the optical path by the detection protrusion 4d of the cam member 4 and is inverted from on to off. (State shown in FIG. 3). Therefore, if the photo interrupter 9 remains on even if the control device 13 performs the forward rotation operation in four steps every fixed number of times corresponding to the total number of steps in the effective focus adjustment area of the lens system, the feeding failure occurs. It is judged that it has occurred, and after supplying the same number of reverse rotation pulses as the forward rotation pulses to the step motor 1 until now, energization is cut off and an error is displayed. In the attached flow chart, operations and judgments that cannot be written in the frame are marked outside the frame. Judgment A in FIG. 5 is performed in steps of 4 steps to the middle position of all steps in the effective focus adjustment area of the lens system. It is based on turning.

Then, when the photo interrupter 9 is turned off by the forward rotation operation of each of the four steps, the operation shifts to the operation of the flowchart of FIG. When the main switch is turned on, the origin switch 8 should normally be off as described above, but if the origin switch 8 is on at this time, some kind of momentum is given. Therefore, it is possible that lens system 5 is protruding.

As such an unexpected projection of the lens system 5, a case where the shielding projection piece 4d of the cam member 4 projects beyond the position of the photo interrupter 9 and a shielding projection piece 4d of the cam member 4 are the photo interrupter It is considered that the case has not reached the position of 9.

First, when the shielding projection 4d of the cam member 4 exceeds the position of the photo interrupter 9, steps are performed by 1/2 step of the total number of steps in the effective focus adjustment area of the lens system. If the motor 1 is rotated in the reverse direction, the shield projection 4d of the cam member 4 should pass the position of the photo interrupter 9 during that time. If the photo interrupter 9 is turned off during the reverse operation of the step motor 1, control is performed. The device 13 determines that the lens system 5 has reached the midpoint position and shifts to the operation of the flowchart of FIG.

When the shielding projection 4d of the cam member 4 has not reached the position of the photo interrupter 9, the step motor is moved by 1/2 step of the total number of steps in the effective focus adjustment area of the lens system. When 1 is reversed, the detection pin 4c of the cam member 4 should break the origin switch 8 during that time. If the origin switch 8 breaks during the reverse rotation of the step motor 1, the controller 13 causes the origin switch 8 to break. The operation starts from the time when the break is detected.

Then, even if the step motor 1 is rotated in the reverse direction by 1/2 step of the total number of steps in the effective focus adjustment area of the lens system, both the origin switch 8 and the photo interrupter 9 are still turned on. The device 13 determines that an abnormality such as a switch malfunction is occurring, not a simple malfunction such as the lens system 5 popping out, and the step motor 1 is further reversed by two steps and then the power is cut off to display an error message. do.

When the photo interrupter 9 is turned off, the lens system 5 is located near the midpoint in the effective focus adjustment area, and the maximum delay time required for the focusing operation from there is shortened to 1/2. Therefore, the controller 13 waits at that position while monitoring both the release switch 11 and the main switch 12. If the main switch 12 breaks without making the release switch 11 at this time, the controller 13 supplies the step motor 1 with a reverse pulse sufficient to return the mechanism to the initial position, and the cam member 4 and the lens system. When 5 is returned to the initial position and the origin switch 8 breaks, the power supply is cut off and all operations are completed. If the origin switch 8 is still in the break state even if the reverse pulse for returning the mechanism to the initial position is supplied to the step motor 1, the control device 13 causes the reverse pulse of, for example, a maximum of 8 pulses to be output to the step motor 1. If the origin switch 8 is still broken, it is judged that some restoration failure or contact failure of the origin switch 8 has occurred, and the error is displayed after turning off the power.

On the other hand, if the release switch 11 is made without breaking the main switch 12, the control device 13 measures the distance to the subject and determines the driving direction and the driving distance from the midpoint position of the cam member 4. The calculated number of driving pulses (X pulses) corresponding to the in-focus position are supplied to the step motor 1, and the step motor 1 is rotated forward or backward by X pulses to move the lens system 5 forward or backward. Fig. 4 shows the state where the lens system has been extended to the advanced end. Then, after moving the lens system 1 to a desired position, the step motor 1 is stopped and the shutter (not shown) is opened and closed.

After the operation of the shutter, the control device 13 causes the step motor 1 to return-rotate by the above-mentioned X pulse, so that the cam member 4 reaches the midpoint position and the photo interrupter 9 is turned off. When the photo interrupter 9 is turned off, the controller 13 waits at the midpoint position while monitoring the state of the release switch 12 or the main switch 11 as described above.

On the other hand, if the photo interrupter 9 does not turn off even when the step motor 1 is rotated by the above-mentioned X pulse, the controller 13 determines that a trouble such as a malfunction of the photo interrupter 9 has occurred. , After supplying the reverse rotation pulse only for returning the cam member 4 to the initial position to the step motor 1, the energization is cut off and an error is displayed.

Although the mechanism has been simplified in the above description, it goes without saying that the shape and structure of each mechanism member should be appropriately determined according to the needs of each camera. Further, although an example using limit switches or photo interrupters as various sensors has been shown above, it goes without saying that any sensor means capable of detecting position can be appropriately selected and used in the present invention. Absent. Further, although the example in which the lens system 5 is cam-driven has been shown above, the transmission mechanism may be of any structure as long as the rotation of the step motor 1 is transmitted, and the gear is directly transmitted by a gear such as a rack and pinion. But it doesn't matter.

[0025]

[Effect of the device]

 As described above, according to the present invention, when the main switch is on, the lens system can be driven from around the midpoint within the effective focus adjustment range of the lens system, so the maximum delay time required for the focusing operation is increased. The value can be reduced to about 1/2, and since the lens system is retracted to the initial position when the main switch is turned off, there is no adverse effect on the storability during carrying.

[Brief description of drawings]

FIG. 1 is a mechanism diagram showing in principle a lens drive mechanism using a step motor as a drive source according to an embodiment of the present invention.

FIG. 2 is a block diagram of a control system of the present invention.

FIG. 3 is a mechanism diagram showing in principle the state in which the cam member is driven near the midpoint in the above embodiment.

FIG. 4 is a mechanism diagram showing in principle the state in which the cam member is driven to the advanced end in the above embodiment.

FIG. 5 is a flowchart showing the first half of the control operation of the present invention.

FIG. 6 is a flowchart showing the latter half of the control operation of the present invention.

FIG. 7 is a time chart of the present invention.

[Explanation of symbols]

 1 step motor 2 output pinion 3 2 step gear 4 cam member 4a rack 4b lens drive cam 5 lens system 5a cam follower 8 origin switch 9 photo interrupter 11 release switch 12 main switch 13 controller

Claims (1)

[Scope of utility model registration request] 1. A forward / reverse rotatable step motor, a lens system having a photographing lens group, and a power transmission system for transmitting the rotation of the step motor to the lens system. In a lens drive mechanism using a step motor as a drive source, which transmits the rotation of the step motor in advance to drive the lens system to a focus position, it is detected that the power transmission system is at the initial position. The first detection means and the second detection means for detecting that the power transmission system is in a substantially intermediate area of the effective focus adjustment area are provided, and the first detection means is provided when the main switch is turned off. The step motor is driven to a position where it is operated to drive the power transmission system, and the step is moved to a position where the second detection means is operated when the main switch is turned on. A lens drive mechanism using a step motor as a drive source, characterized in that a motor is used to drive the power transmission system to stand by.