Camera lens barrel having both pulse drive control and microstep drive control

• US 5,519,465 A
• Filed: 04/07/1994
• Issued: 05/21/1996
• Est. Priority Date: 11/09/1990
• Status: Expired due to Term

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Kawamura, Hiroshi, Nakazato, Kunio, Nakayama, Akihito, Inoue, Norikatsu
• Primary Examiner(s): Gellner, M. L.
• Assistant Examiner(s): HAN, JANG K
• Application Number:
  US08/224,197
• Time in Patent Office: 775 Days
• Field of Search: 354/195.1, 354/195.12, 354/400, 359/684, 359/686, 359/694, 359/696, 359/697, 359/823
• US Class Current: 396/86
• CPC Class Codes: G02B 7/102 controlled by a microcomputer cameras with interchangeable lenses G03B17/14

Abstract

A camera lens barrel having a first grouped lens, a movable second grouped lens for variable magnification, a third grouped lens, and a fourth grouped lens, which are respectively arranged along an optical axis, and accommodating a drive system for the first to fourth lenses. The camera lens barrel is provided with a stepping motor, a control device capable of respectively carrying out in a low speed drive mode at least micro step drive control and pulse drive control of the stepping motor, and a moving mechanism for converting rotation of the stepping motor into movement of the second grouped lens along the optical axis. The control device carries out position control of the second grouped lens according to a control quantity of the stepping motor. As the stepping motor is driven under the micro step drive control, the generation of noise and vibration can be greatly suppressed as compared with a conventional lens barrel employing a DC motor as a drive source.

Claims

1. In a camera lens barrel having a first grouped lens, a movable second grouped lens for variable magnification, a third grouped lens, and a fourth grouped lens, which are respectively arranged along an optical axis, and accommodating a drive system for said first to fourth lenses, the improvement comprising:

a stepping motor having a lead screw mounted on an outer surface of a rotary shaft;

control means selectively carrying out in a low speed drive mode and in a high speed drive mode at least micro step drive control and pulse drive control of said stepping motor and providing position control of said second grouped lens according to a control quantity of said stepping motor;

a frame for the second grouped lens which is directly engaged with said lead screw, said lead screw and frame directly converting rotation of said stepping motor into movement of said second grouped lens along said optical axis; and

a mode switch for selecting said high-speed drive mode or said low-speed drive mode, wherein when the high-speed drive mode is selected, said control mean carries out pulse drive control of said stepping motor, while when the low speed drive mode is selected, said control means carries out the micro step drive control of said stepping motor.

2. The camera lens barrel according to claim 1, wherein said control means includes means for calculating a position of said second grouped lens on the basis of a rotational position of said stepping motor corresponding to an end position of said second grouped lens and subsequently according to the control quantity of said stepping motor.

3. The camera lens barrel according to claim 1, wherein the pulse drive control is a one-phase-on pulse drive, a two-phase-on pulse drive, or a half-step drive control.

4. The camera lens barrel according to claim 1, wherein the micro step drive control is a two-phase sin/cos drive control.

5. The camera lens barrel according to claim 1, wherein said control means is a control system comprising:

a control circuit having a microcomputer;

a control data memory comprising a micro step control data memory section for said micro step drive control and a trapezoidal control data memory section for said pulse drive control; and

a driver circuit for connecting said control circuit to said stepping motor.

6. A drive arrangements for a lens grouping, comprising:

a camera lens barrel having a first grouped lens, a movable second grouped lens for variable magnification, a third grouped lens, and a fourth grouped lens, said first to fourth lenses arranged respectively along an optical axis of said lens barrel, and a drive system for said first to fourth lenses accommodated within said lens barrel, said drive system comprising;

a stepping motor having a rotation responsive to a drive control;

means for converting rotation of said stepping motor into movement of said second grouped lens along said optical axis, said means for converting including a frame having a tapped hole in which a lead screw is engaged, said lead screw being mounted on an outer surface of a rotary shaft coupled to said stepping motor;

drive control means, including a control circuit, cooperating with said stepping motor for selectively providing a micro step drive control in a low speed drive mode for said stepping motor and a pulse drive control in a high speed drive mode for said stepping motor and providing position control of said second grouped lens according to a control quantity of said stepping motor; and

means cooperating with said drive control means for selecting said high speed drive mode or a low speed drive mode for said stepping motor, wherein when the high speed drive mode is selected, the drive control means carries out pulse drive control of said stepping motor, and when the low speed drive mode is selected, the control means carries out the micro step drive control of said stepping motor.

7. The drive arrangement set forth in claim 6 wherein said control circuit includes a microcomputer accommodating a program for executing said micro step drive control and said pulse drive control, a control data memory storing data for executing said pulse drive and said micro step drive, and driver circuits cooperating with said data memory and said stepping motor.

8. The drive arrangement set forth in claim 6, wherein said control means calculates a position of said second grouped lens on the basis of a rotational position of said stepping motor corresponding to an end position of said second grouped lens and subsequently according to the control quantity of said stepping motor.

9. The drive arrangement as set forth in claim 6, wherein the pulse drive control is a one-phase-on pulse drive, a two-phase-on pulse drive, or a half-step drive control.

10. The drive arrangement as set forth in claim 6, wherein the micro step drive control is a two-phase sin/cos drive control.

11. The drive arrangement as set forth in claim 6, wherein said selecting means includes a mode switch for selecting either the pulse drive mode or the microstep drive mode.

12. A camera lens barrel comprising:

a plurality of lens groups arranged consecutively along a common optical axis including a first lens group, a second lens group, a third lens group and a fourth lens group, said first lens group and said third lens group being fixed within the lens barrel, and said second lens group and said fourth lens group being movable along said optical axis;

a stepping motor operatively coupled to a rotary shaft;

a driving circuit for driving said stepping motor;

a frame in which said second lens group is mounted, said frame including a hole formed therein;

a lead screw mounted on said rotary shaft and threadedly inserted into said hole, whereby rotation of said shaft causes said frame to move in a linear direction along said optical axis;

a sensor provided in a fixed position relative to said frame, said sensor providing a position signal indicative of a position of said sensor and said second lens group relative to the first lens group;

mode select means for providing a mode signal indicative of a desired operation mode, said operation mode being one of a high speed mode and a low speed mode; and

means for controlling said driver circuit with a control quantity output and for determining the position of said second lens group along said optical axis based on said position signal, said mode signal, and said control quantity output.

13. The camera lens barrel according to claim 12 further comprising a second sensor fixed relative to said fourth lens group, said second sensor providing a second position signal to said control circuit indicative of the absolute position of said second sensor and said fourth lens group relative to the lens barrel.

14. The camera lens barrel according to claim 13 further comprising a linear motor operatively coupled to said fourth lens group, said linear motor adjusting the position of said fourth lens group along said optical axis based on the output of a second driver circuit, said second driver circuit being controlled by said control circuit based on said second position signal, whereby drive control of said stepping motor is carried out in association with drive control of said linear motor.

15. The camera lens barrel according to claim 12 wherein said second lens group is moved along said optical axis to adjust zoom, and said fourth lens is moved along said optical axis to adjust focus.

16. The camera lens barrel according to claim 12 further comprising an adjustable iris positioned along said optical axis.

17. The camera lens barrel according to claim 12 wherein said control circuit includes a microcomputer and a control data memory in which a program is stored, said program executing a desired operation mode.