Original scanning apparatus

• US 5,119,136 A
• Filed: 12/11/1989
• Issued: 06/02/1992
• Est. Priority Date: 12/13/1988
• Status: Expired due to Fees

• Current Assignee: Minolta Camera Kabushiki Kaisha
• Original Assignee: Minolta Camera Kabushiki Kaisha
• Inventors: Morikawa, Takeshi
• Primary Examiner(s): Grimley, A. T.
• Assistant Examiner(s): Smith, Matthew S.
• Application Number:
  US07/448,711
• Time in Patent Office: 904 Days
• Field of Search: 355/233, 355/235, 355/228, 355/232, 355/67, 355/208, 358/497
• US Class Current: 399/208
• CPC Class Codes: G03B 27/526 in which the projection optics move
• CPC Class Codes: G03G 15/04 for exposing, i.e. imagewise exposure by optically projecting the original image on a photoconductive recording material

Abstract

A pulse corresponding to the rotation of a motor which moves a scanning system of an original scanning apparatus in a reciprocating motion is counted by a counter each time when the scanning system is operated in the forward and backward movement. By a software control which is performed basing on the counted value, a time period to start braking the scanning system at a practical position in the returning movement is obtained to stop the scanning system at its home position. In order to obtain a desired speed, a duty ratio of a pulse for applying electricity to a motor is controlled from a pulse which corresponds to the rotation of the motor being operated and a pulse width corresponding to the rotation of the motor when it is driven at a desired speed.

Claims

1. An original scanning apparatus comprising:

a motor;

a scanning system being reciprocated by said motor to scan an orginial through forward movement thereof;

pulse generating means for generating encoder pulses corresponding to the rotation of the motor;

pulse supplying means for supplying drive pulses to apply electric current to the motor, said drive pulse having a fixed but different frequency from that of the encoder pulse when the motor is driven at a constant speed; and

control means for controlling the speed of the motor in accordance with the on time width of the drive pulse which is supplied by the pulse supplying means, said control means deciding a duty ratio of the drive pulse from the encoder pulse width generated at present and a reference encoder pulse width corresponding to the rotation of the motor when it is driven at a desired speed and supplying the drive pulse to the motor according to the duty ratio desired.

2. The original scanning apparatus as defined in claim 1, wherein the pulse supplying means supplied a pulse of a fixed frequency.

3. The original scanning apparatus as defined in claim 1, wherein the control means performs speed control by a pulse width modulation method.

4. The original scanning apparatus as defined in claim 3, wherein the control means performs speed control by an acceleration when electric current is applied to the motor and by a deceleration when electric current is not applied to the motor.

5. The original scanning apparatus as defined in claim 1, wherein the control means measures values of the acceleration and the deceleration at the time when the speed of the scanning system reaches a predetermined desired speed for scanning the original.

6. A scanning apparatus which is arranged to scan an original through forward movement of a scanning system reciprocated by a motor, comprising:

pulse generating means for generating encoder pulses corresponding to the rotation of the motor;

pulse supplying means for supplying drive pulses to apply electric current to the motor, said drive pulses having a fixed but different frequency from that of the encoder pulses when the motor is driven at a constant speed, and

control means for controlling the speed of the motor in accordance with a time width of the drive pulse which is supplied by the pulse supplying means, said control means providing a duty ratio of the drive pulse from the encoder pulse width and a reference encoder pulse width corresponding to the rotation of the motor when it is driven at a desired speed and supplies the drive pulse to the motor according to the duty ratio decided.

7. A scanning apparatus which is arranged to scan through a forward movement of a scanning system reciprocated by a motor and to return to an initial position, comprising:

pulse generating means for generating encoder pulses corresponding to the rotation of the motor;

pulse supplying means for supplying drive pulses to apply electric current to the motor, said drive pulses having a fixed but different frequency from that of the encoder pulses when the motor is driven at a constant speed, and

control means for controlling the speed of the motor by pulse width modulation in accordance with a time width of the drive pulse which is supplied by the pulse supplying means, said control means providing a duty ratio of the drive pulse from the encoder pulse width and a reference encoder pulse width corresponding to the rotation of the motor when it is driven at a desired speed, and supplying the drive pulse to the motor according to the duty ratio so that an acceleration of the scanning system occurs when electric current is applied to the motor, and a deceleration occurs when electric current is not applied to the motor.

8. A scanning apparatus comprising:

a motor;

a scanning system being reciprocated by the motor to scan an original through forward movement thereof;

control means for controlling the scanning system so that the scanning system is moved forward from a standard position at a predetermined constant speed to scan the original, and after the scanning action is finished the scanning system is moved backward while providing full power to the motor until a braking action is started at a predetermined point in time in the backward movement so as to stop the scanning system at the standard position;

pulse generating means for generating a pulse corresponding to the rotation of the motor;

a counter for counting the pulses after the scanning system has moved away from the standard position, and

means for causing the control means to start a braking action when the value of said counter has become a predetermined value wherein the counter performs a count up operation when the scanning system is being moved forward, and when the scanning system is being moved backward, it performs a count down operation form the value counted in the forward movement.

9. A scanning apparatus comprising:

a motor;

a scanning system being reciprocated by the motor to scan an original through forward movement thereof;

control means for controlling the scanning system so that the scanning system is moved forward from a standard position at a predetermined constant speed to scan the original, and after the scanning action is finished the scanning system is moved backward while providing full power to the motor until a braking action is started at a predetermined point in time in the backward movement so as to stop the scanning system at the standard position;

pulse generating means for generating a pulse corresponding to the rotation of the motor;

a counter for counting the pulses after the scanning system has moved away from the standard position, and

means for causing the control means to start a braking action when the value of said counter has become a predetermined value, wherein the counter, when the scanning system is moved backward, counts the pulse in a different manner from that at the time when the scanning system is moved forward.

10. The scanning apparatus as defined in claim 9, wherein the counter counts each pulse when the scanning system is moved forward and the counter counts a predetermined number each time pulses of the predetermined number of pulses are generated when the scanning system is moved backward.

11. A scanning apparatus which is arranged to scan through a forward movement of a scanning system reciprocated by a motor and to return to an initial position, comprising:

a source of electrical power;

pulse generating means for generating encoder pulses corresponding to the rotation of the motor;

pulse supplying means for supplying drive pulses to apply electric current from the source of electrical power to the motor, said drive pulses having a different frequency from that of the encoder pulses when the motor is driven at a constant speed;

means for providing a regenerative braking action to the motor to caused deceleration, and

control means for controlling the speed of the motor by pulse width modulation in accordance with a time width of the drive pulse which is supplied by the pulse supplying means, said control means providing a duty ratio of the drive pulse from the encoder pulse width and a reference encoder pulse width corresponding to the rotation of the motor when it is driven at a desired speed, and supplying the drive pulse to the motor according to the duty ratio so that an acceleration of the scanning system occurs when electric current, from the source of electrical power, is applied to the motor, and a deceleration occurs when electric current, from the source of electrical power, is not applied to the motor.

12. A scanning apparatus which is arranged to scan an original through a forward movement of a scanning system reciprocated by a motor and to return the scanning system to a home position, comprising:

pulse generating means for generating encoder pulses corresponding to the rotation of the motor;

pulse supplying means for supplying drive pulses to apply electric current to the motor, said drive pulses having a fixed but different frequency from that of the encoder pulses when the motor is driven at a constant speed, and

control means for controlling the speed of the motor in accordance with a time width of the drive pulse which is supplied by the pulse supplying means, said control means providing a duty ratio of the drive pulse from the encoder pulse width and a reference encoder pulse width corresponding t the rotation of the motor when it is driven at a desired speed and supplies the drive pulse to the motor according to the duty ratio decided;

a counter for counting pulses of the pulse generating means, and

means for causing a braking action to be applied to the motor when the counter counts a predetermined number of pulses when the scanning system is being moved in a backward movement towards the home position.