JPS61116342A - Controlling method of lens position - Google Patents

Abstract

PURPOSE:To always move precisely a lens to an objective position by reciprocating a lens after turning on a power supply, and finding out and storing the hysteresis of a detector to calibrate the position of a lens. CONSTITUTION:Reflected light form an original is made incident upon a lens unit 1 along an optical axis P, reflected by a fixed mirror 3 through an optical board 2 on which a light passing notched pat is formed and then led to a photosensitive drum. A lens unit 1 is reciprocated before and after the hole position and the hysteresis of the home position sensor LHPS is previously stored. If a moving direction when the lens unit is moved up to an objective position is oriented in a specific direction, the position of the lens unit 1 is calibrated in accordance with the hysteresis at the calibration of the lens unit 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a lens position control method in a variable magnification copying machine.

<Summary of the Invention> The present invention provides a method for detecting the home position of a lens using a detection device having an amount of hysteresis. The position is calibrated accordingly.

<Prior Art and Its Disadvantages> Variable magnification copying machines, particularly stepless variable magnification copying machines equipped with a zoom lens, generally use a stepping motor as a drive source for moving the lens.

Further, a home position is set within the movement range of the lens, and the movement of the lens is performed based on the home position. However, since a sensor with a detection width made of a phototransistor or the like is used to detect the home position, when the detection plate that operates according to the movement of the lens crosses the area of this detection width, the sensor output is smoothly continuous. changes, making it difficult to identify the home position. Therefore, generally, a Schmitt trigger circuit is used to specify the position where the output voltage of the sensor rises from "0" to "l" or falls from "1" to "0" as the home position. Figure 1 shows how to specify the home position using a Schmitt trigger circuit.

In the same figure (A), 12 is a lens position detection plate, which is fixed to the lens inside the copying machine. L HP
S is a home position (HP) detection sensor. 13 is a phototransistor. The LHPS 2 has a U-shaped cross section, and an LED (not shown) is arranged facing the phototransistor 13 in a direction perpendicular to the plane of the paper. The lens position detection plate 12 is this U-shaped LHP.
It can move in the direction of arrow A or B along the groove S. When the detection plate 1 moves in the direction B from the position shown in the figure and the tip of the plate reaches the side edge of the phototransistor 20, the phototransistor output, that is, the L HP S output, changes as shown in the figure (B). begins to change. The tip of the detection plate 12 is a phototransistor 20
The LHPS output reaches its maximum when it completely crosses the line. Furthermore, when the detection plate 12 moves in the direction of arrow A from the position where it completely crosses the phototransistor 20, the LH
The PS output is generated when the detection plate 12 moves in the B direction.

Take a change that is opposite to the change of time. A Schmitt trigger circuit (not shown) that receives the LHPS output converts the change in the output voltage shown in FIG. 5B into the voltage change shown in FIG. When the detection plate 12 moves in the direction of arrow B, the output voltage follows a trajectory of a-*l)-wC-+d. When the detection plate 1 moves in the direction of the arrow from completely covering the phototransistor 20, d −+ 6−+ f
- Follow the trajectory of 1-3. In this case, the home position will be set at point f or point f.

If the home position is specified using a Schmitt trigger circuit with hysteresis characteristics as described above, LH
Errors caused by the PS detection width can be eliminated. However, as shown in the same figure (C), when the home position is set to point b, for example, and the lens detection plate 12 is moved in the direction of arrow A, it follows the trajectory of d -1-6- + f - + a, so it is at point b. cannot be detected. For this reason, in the conventional lens position control method, if you try to calibrate the count value of the counter at the home position when moving the lens, the detection plate 1 must be moved during the lens movement process.
It was necessary to move the robot in the B direction and pass the home position HP. Therefore, when the lens position detection plate 12 is simply moved from the right side to the left side of the home position HP, there is a drawback that it is impossible to calibrate the counts of the counters at the home position HP.

<Object of the Invention> An object of the present invention is to store the amount of hysteresis in advance when detecting the home position using a detection device with hysteresis characteristics, so that the home position can be detected regardless of whether the lens is moving in the left or right direction. To provide a lens position control method capable of calibrating count values of counters at a position HP and always accurately moving a lens to a target position.

<Structure and effects of the invention> This invention is constructed as follows.

After turning on the power, move the lens back and forth around the home position. At this time, a counter is used to control the lens movement. As the counters, for example, a current position counter for the home position and a movement amount counter indicating the amount of movement from the current position to the destination position are used. In this case, the home position is a position where the output of the detection device rises or falls, as shown in FIG. 1(C). Here, the position where the output voltage rises, that is, point b, is defined as the home position.

When the lens is moved back and forth to the home position, the amount of hysteresis (distance from point f to point b in FIG. 1C) of the detection device can be determined by using the above counter.

For example, if you use the above position counter and movement amount counter as counters, move the lens to the right, set the position counter to 0 at point b, and use the movement amount counter to move the lens a little further to the right. Then, move the lens to the left (until the phototransistor output becomes stable) and read the contents of the position counter when the lens reaches point f. The counted value of the position counter at this time is the hysteresis amount M (see FIG. 1(C)).

Thereafter, when moving the lens to the target position, calibration is performed at point b when moving the lens to the right, and calibration is performed by subtracting the hysteresis amount M at point f when moving the lens to the left. As a result, even when the lens moves in either the left or right direction, the count value of the counter can be calibrated when passing the home position HP.

As described above, according to the present invention, by determining the hysteresis amount of the home position detection device in advance and storing it in the memory, when the lens moves in a direction where the hysteresis amount becomes a problem, the hysteresis amount is determined according to the hysteresis amount. The counter count value can be calibrated at the home position regardless of whether the lens moves left or right, and the lens can always be stopped at the correct position. can.

<Embodiment> FIG. 2 is a schematic plan view of a zoom copying machine lens drive section in which the lens position control method according to the present invention is implemented. Reflected light from the document illuminated by a light source (not shown) enters the lens unit 1 along the optical axis P, and is reflected by the fixed mirror 3 via the optical base plate 2 in which a cutout for light passage is formed. It is guided to a photoreceptor drum (not shown). The lens unit 1 is fixed to an arm 4 located perpendicular to the optical axis P, and one end of the arm 4 is attached to a shaft 5 located horizontally to the optical axis P.
It is slidably supported. Further, one end of the arm 4 is fixed to a part of a wire 6, and the wire 6 is connected to a pulley 7.
It is hung at 9. Further, the pulley 9 is connected to a speed reduction mechanism 11 of a lens motor 10, which is a stamping motor. One end of a lens position detection plate 12, which is parallel to the optical axis P and extends in the direction of the fixed mirror 3, is fixed to the other end of the arm 4. This lens position detection plate 1
A home position sensor LHPS is arranged in the extending direction of 2. This home position sensor LHPS
is composed of an optical sensor consisting of a light receiving element (phototransistor) and a light emitting element (LED), which has a recess in the center through which the lens position detection plate 12 passes. When the lens position detection plate 12 is located in this recessed portion, the lens is turned on. The output of the sensor LHPS is input to a Schmi-node trigger circuit (not shown), where it is connected to the circuit shown in FIG.
) is converted to an output voltage as shown in The position of point b in FIG. 1(C) is the home position of the lens. In addition,
Axes 13.14 are set on both sides of the copying machine body parallel to the optical axis P, and both ends of the mirror and base 15 are aligned with this axis 13.14.
is slidably supported. The mirror base 15 fixes a mirror that receives reflected light from the original when scanning the original.
Together with another mirror base to which a light source (not shown) is fixed, it reciprocates along axes 13 and 14 during document scanning.

FIG. 3 is a schematic block diagram of the control section. The control section of the copying machine in this embodiment is composed of a master CPU (MCPU) 50 and a slave CPU (SCPU) 51. The MCPU 50 sends lens initial commands and lens movement commands to the 5 CPU 51.
sends status etc. to the MCPU 50. MCPU
50 receives signals from input key 1 various sensors, etc., and inputs the ROM
5 CPU according to the program predefined in 52
It sends commands to the CPU 51, receives status from the CPU 51, and controls various solenoids, main motors, etc. Upon receiving the command sent from the MCPU 50, the 5CPU 51 receives a signal from the home position sensor LHPS via the Schmitt trigger circuit, and operates the lens motor 1 according to a program predefined in the ROM 53.
Send a drive pulse to 0. Further, after performing a predetermined operation, it transmits status and the like to the MCPU 50. Furthermore, 5CPU51 is at the home position of the lens (point b)
A position counter indicating the current position relative to the target position and a movement amount counter indicating the movement distance from the current position to the destination position are allocated to the internal RAM.

Next, the operation of the five CPUs of the control section will be explained with reference to FIG. FIG. 4 is a flowchart showing the lens position control operation of the 5 CPUs.

When the power is turned on, step nl (step ni is simply n)
i), it is determined whether the Schmitt trigger S lower output is in the on state or the off state. When the Schmitt trigger ST is in the on state, the lens position detection plate 1 is located to the right of point b in FIG. 1(C). In this state, the process progresses to nl-+n2 and the pulse motor MT is rotated to the left. When the Schmitt trigger S lower output turns off, that is, when point f is reached, the process proceeds to n3. Here, a predetermined negative value -N1 is set in the counter C2.

A negative value -N1 moves the lens position detection plate 12 further to the left from point f to completely change the sensor LHPS output.
This is a value large enough to make the counter C
2 constitutes a movement amount counter from the current position to the destination position.

At n4, the motor MT continues to rotate to the left, and when the drive pulse P falls, 1 is added to the counter C2, and at n5, the motor MT continues to rotate to the left until it is determined that the counter C2 becomes O.

When the Schmitt trigger output is already in the OFF state at nl, or when the Schmitt trigger output is turned off by the operations in n2 to n5 above, proceed to n6 and set the motor MT.
Starts clockwise rotation. Continue clockwise rotation until the output of Schmitt trigger ST turns on. That is, the motor MT continues to rotate clockwise until it reaches point b. When reaching point b, n
1, the counter C1 is set to 10", and the counter C2 is set to a positive value Nl. The counter C1 represents the current position with respect to point b. In this embodiment, point b is the home position. Set in counter C2. The positive value Nl is large enough to move the lens position detection plate 1 until the LHPS output becomes completely "H", as in n3 above.Next, clockwise rotation is continued at n8. Drive pulse P
At each falling edge, 1 is added to the counter C1 and 1 is subtracted from the counter C2. When it is detected at n9 that the value of the counter c2 has become 0, that is, when the lens position detection plate 12 completely covers the phototransistor 20 by moving sufficiently to the right, the process proceeds to nlO.

At nto, the motor is rotated to the left and moved one step at a time until the Schmitt trigger S lower output is turned off, that is, until the point f is reached. When the point f is reached, the count value of the counter C1 at that time is stored in a predetermined area of the RAM in the 5cPU 51 at n11. The count value of the counter C1 at n11 becomes the amount of hysteresis. By reciprocating the Uchi lens detection plate 12 back and forth to the home position as described above, the amount of hysteresis of the Schmitt trigger ST when point b is set as the home position is stored in the memory. Next, rotate the motor MT clockwise again at n12, and when the Schmitt trigger S lower output turns on at n13,
That is, when point b is reached, the process proceeds to n14 and the motor MT is stopped. At point b, the position counter C is set by the process of n7 above.
1 must be “0”, so check this with n15 and if you can confirm that it is “0”, n1
The process moves to the standby routine of step 6. If the count value of the position counter C1 is not "O", it means that a deviation has occurred in the position calibration of n8 to n13, so the calibration is performed again starting from n2.

At n16, the system waits for the magnification signal SM to be sent from the MCPU 50, and when the signal SM is sent (then, the lens position N2 corresponding to the magnification is read out from the list stored in advance in the ROM 53. At n17, The movement amount counter C2 is set to the value obtained by subtracting the contents of the position counter C1 from the target lens position N2.Initially, since the position counter C1 is "O", the contents of the movement amount counter C2 are equal to the target lens position N2. At n1B, it is determined whether the amount of movement entered in the amount of movement counter C2 is positive (rotation to the right) or negative (rotation to the left). If it is positive, the process proceeds to n19 and rotates to the right and the amount of movement is countered by the amount of movement counter C2 for each drive pulse. 1 is subtracted from , and 1 is added to the position counter C1. At n20, it is determined whether or not the Schmitt trigger S lower output is turned on during movement, that is, whether or not the point b is passed.If it is passed, n
At step 21, the target lens position N2 is set in the movement amount counter C2, and "0" is set in the position counter C1 to calibrate the counter. At this point, even if an error occurs during movement at n19, calibration will be performed. At n22, it is determined whether the movement amount counter C2 has reached "0". That is, it is determined whether the target lens position has been reached. If “O”, send a lens movement completion signal SL to the MCPU 50 at n23, stop the motor MT, and then n1
Return to the standby routine of step 6.

If the amount of movement entered in the movement amount counter C2 at n18 is negative (rotation to the left), the process proceeds to n24 and the motor MT is rotated to the left. Then, for each driving pulse, the movement amount counter C2
1 is added to the position counter ci, and 1 is subtracted from the position counter ci. Also, it is determined at n25 whether or not the point f is passed during the movement, and if the point is passed, the counts of the movement amount counter C2 and the counter C1 are calibrated at n26. That is, the movement amount counter C2 is set to the target lens position N2 minus the hysteresis amount stored in the memory, and the position counter C1 is set to the hysteresis amount. As a result, calibration is performed using the home position (point b) as a reference. Below n2
2, the count value of the movement amount counter C2 is "0" as above.
n23 when it becomes “O”.
Proceed to.

When point b is set as the home position by the above operation, even if the lens position detection plate 12 moves to the left, when it reaches one point, the hysteresis amount stored in the memory is set to the position counter C1. Position calibration can be performed by setting. In addition, when entering the standby routine n16, a timer T is set at n30, and when a predetermined time T0 is exceeded, the process returns to n2. In other words, large vibrations may occur when loading a cassette into a copying machine or removing a jam.In such cases, the count value of the position counter C1 may deviate. regularly by routine
The operation below 2124 calibrates the position and returns it to the same magnification position.

In this embodiment, a photodetection sensor consisting of a combination of a phototransistor and an LED was used as the HP detection sensor, but the present invention can also be applied to the case where a magnetic sensor, a microswitch, a reed switch, etc. are used. Further, there are cases where a plurality of HP detection sensors can be used, and it goes without saying that the present invention can be applied to each position in such a case as well. Furthermore, in this embodiment, the point b in FIG. 1 is set as the home position, and when the lens moves to the left, the hysteresis amount is decremented from the movement amount counter C2 at one point, but the point f is set as the home position. When the lens moves to the right, the movement amount counter C is set at point b.
The amount of hysteresis is decreased from 2.

[Brief explanation of the drawing]

FIGS. 1A to 1C are diagrams illustrating in detail the operation of a detection device having hysteresis characteristics and the present invention. FIG. 2 is a schematic plan view of a zoom copying machine lens drive section in which the method of the present invention is implemented, FIG. 3 is a schematic block diagram of the control section, and FIGS. 5 CPUs to implement
3 is a flowchart showing the operation of FIG. 1-Lens unit, IO-Lens motor (stepping motor), LHPS
-Home position sensor, 12-Lens position detection plate, ST-Schmitt trigger circuit.

Claims (1)

[Claims] (1) The lens is moved by a stepping motor, the lens movement amount and position are obtained from the count value of a counter, and the home position is detected by a detection device with hysteresis characteristics, and the lens position is calibrated when the home position is detected. In the lens position control method, the hysteresis of the detection device is determined and stored by reciprocating the lens back and forth to the home position after the power is turned on, and when the direction of movement when moving the lens to the target position is a specific direction. A lens position control method characterized in that, when calibrating the lens position, the lens position is calibrated according to the amount of hysteresis.