JP2006118863A - Positioning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extensively reduce the processing time of a personal computer regarding the detection of a position. <P>SOLUTION: A positioning device includes a 1st detection means for measuring the travel distance of a member to be driven with a 1st scale, and a 2nd detection means for measuring the movement of the object with a 2nd scale finer than the 1st scale in scale interval, wherein the 1st detection means is switched to the 2nd detection means corresponding to the remaining distance to the target position while travelling to the target position, and the member is stopped when it is detected that the member reaches the target object. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a position detection device for moving or rotating a driven member by a desired moving amount or rotating amount, or moving or rotating a driven member to a desired position. The apparatus of the present invention is a digital processing circuit and an analog processing circuit for performing position detection in a control device that uses a motor for moving or rotating a driven part as a drive source and includes speed detection and position detection. It is suitable for improving the control method for effectively controlling both of them so that the driven part driven by the motor is accurately stopped at a predetermined position.

The case where the present invention is applied to an autofocus function of a camera will be described. At present, a camera is generally equipped with an autofocus function, and it is required to improve the focus accuracy in autofocus and shorten the time until the subject is focused. It has been. As a method for solving this problem, it is considered necessary to improve the accuracy of the encoder element used for detecting the position of the focus lens with regard to increasing the accuracy of the focus.
Conventional methods currently used to achieve this high accuracy include the use of optical elements utilizing light transmission and reflection, such as photointerrupter elements and photoreflector elements, and magnetic detection elements such as MR elements and Hall elements. It has become common. However, any of these detection methods requires processing a specific pattern on a measurement object for detection, and there are various restrictions on the processing of the pattern.

For example, in a light passing method using a photo interrupter, a long and narrow hole called a slit is formed in a disk-like plate attached to a rotating member, light passes through the hole portion, and light is blocked except for the hole. Some devices convert the light quantity difference into an electrical signal to detect the amount of rotation of the rotating member. In this manner, the amount of rotation of the rotating member can be detected more finely by shortening the width of the hole formed in the disk and increasing the number of holes per rotation. However, in order to realize this, a high-precision processing technique is required for the disc, and it becomes very expensive.
Further, it is known that a photo interrupter element takes a certain amount of delay time to convert an optical signal into an electric signal. In other words, it is an element with poor photoelectric conversion responsiveness, so even when the rotation speed is the same, the S / N ratio when converted to an electrical signal deteriorates due to the narrow slit on the disk, and electrical detection is performed. The circuit also needs to be complicated and expensive.

Introducing a method for solving the problems of these detection systems, Patent Document 1 (Japanese Patent Laid-Open No. 6-313718) discloses that an output of an element is converted by an A / D converter in a position detection circuit using an MR element. An offset adjustment for detecting and optimizing the output range of the element is described using a D / A converter.
In addition, as an optical apparatus that includes a plurality of detection units and performs control to switch between them, an autofocus (hereinafter referred to as AF) lens described in Patent Document 2 (Japanese Patent Laid-Open No. 2001-83397), for example, Equipped with two types of speed detection means: a pulse encoder that detects the drive speed and drive amount, and a pulse encoder that detects the drive speed of the AF actuator, and detects the speed close to the AF actuator when the AF actuator is activated / accelerated. It is described that the speed control is performed based on the speed information from the means, and the speed control is performed based on the speed information from the speed detecting means close to the focus lens when the AF actuator is decelerated or stopped.
JP-A-6-313718 JP 2001-83397 A

Patent Document 2 is a method for canceling mechanical friction in order to stabilize the stop position of the focus lens. Patent Document 1 has a circuit configuration for eliminating an electrically unstable element. Both objectives seek stable position detection accuracy.
However, in the method as in Patent Document 1, the state of the A / D converter must be detected at all times, and when used in a device with movement amount control and speed control, the load on each control unit increases. As countermeasures, it may be possible to make each control independent or to speed up the control unit itself, but the control unit becomes expensive in any case.
Further, in the method described in Patent Document 2, the resolution of the pattern used for the detection system remains limited in manufacturing, and the amount of movement of the focus lens cannot be set finely. In addition, when a minute focus lens is moved, problems such as low effects occur.

FIG. 2 shows a detection system circuit simplified to make the circuit described in Patent Document 1 easier to understand.
The circuit A in FIG. 3 is a system in which the output of the MR element is divided by a resistor and extracted. VR1 adjusts the offset voltage of the output. The divided output is connected to an analog input terminal of the microcomputer, and is divided into fine voltages by the A / D conversion function of the microcomputer, and the voltage value is detected as a movement amount. For example, when the amplitude of the analog signal is 1 V and the power supply voltage of the A / D converter is 3 V and the resolution is 10 bits, 1 V / 3 V × 1024 = about 341, and the MR element outputs 1 V at 341 amplitudes. It will be divided and the accuracy can be improved considerably.
However, it is necessary for the microcomputer to always monitor the amplitude signal from the MR element, and it is quite difficult to perform other controls (for example, speed control) with the same microcomputer. Therefore, it is necessary to prepare another microcomputer or use a high-speed microcomputer, which is considered to be expensive and increase power consumption.

As a method for simplifying the method described in Patent Document 1, a circuit B will be described. VR2 adjusts an output offset voltage. The divided output is connected to the input of the comparator IC (COMP), and a fixed voltage that is resistance-divided by R1 and R2 is input to the other input terminal of COMP. The fixed voltage is used as a reference voltage, and the difference between the detected voltage from the MR element and the reference voltage is output from COMP as a square wave. By counting this square wave with a microcomputer, it can be detected as the amount of movement of the measurement object.
In order to perform high-precision detection by this method, as described in the background art section above, a high-precision processing technique for the MR element measurement object itself is required, resulting in an expensive configuration.
An object of the present invention is to solve the problems in the above-described conventional example.

  In order to solve the above-described problem, a first position detection device according to the present invention includes a first detection unit that measures a movement amount of a driven member with a first scale, and a movement amount of the driven member. Second detection means for measuring with a second graduation having a smaller interval than the first graduation, and driving the driven member toward a desired target position, and according to the remaining moving amount to the target position Drive control means for switching between the first detection means and the second detection means and stopping the driven member when it is detected that the driven member has reached the target position. Features.

In the present invention, the movement includes not only linear movement and curved line movement, but also includes rotation when the driven member is a rotating body.
Preferably, the drive control means uses the first detection means when the remaining moving amount is larger than a predetermined value, and uses the second detection means when the remaining movement is smaller than the predetermined value.
The measurement only needs to be performed in the vicinity of the driven member passing through each scale. Therefore, the processing time for measuring the amount of movement of the driven member can be reduced for the portion measured with the first scale having a wide interval. In addition, by measuring the remaining portion with the second scale, it is possible to greatly improve the position detection accuracy as compared with the case where only the first scale is measured.
In the first position detection device, the second detection means is a periodic signal generated in accordance with the movement of the driven member and has a voltage amount corresponding to the position of the driven member within each period. The position signal generating means for generating the voltage and means for A / D converting the voltage amount can also be used. The A / D conversion means includes means for generating a digital value corresponding to each of the second scales, conversion means for converting the digital value into a voltage amount, a voltage amount output from the conversion means, and the position signal. You may comprise by the comparison means which compares the voltage amount which a generation means outputs, and the means which outputs the said digital value when the output of this comparison means inverts as a position measurement value.

The second position detection apparatus according to the present invention is a position that generates a position signal that is a periodic signal generated according to the movement of the driven member and has a voltage amount corresponding to the position of the driven member within each period. It is represented by the number of signal generation means, first detection means for detecting the amount of movement of the driven member by the first scale from the position signal, and the number of second scales having a smaller interval than the first scale. Calculating means for dividing the target movement amount of the driven member into the number of the first graduations and the remaining movement amount less than the first graduation interval; and the calculated remaining movement amount as a voltage amount. A converting means for converting; a comparing means for comparing a voltage amount output by the converting means with a voltage amount output by the position signal generating means; and the first detecting means is operated by the first detection means when the driven member moves. Count the number of the first scale calculated by the means, and the output of the comparison means is inverted Wherein the driven member characterized by comprising a second detecting means for detecting that it has moved the target amount of movement when the.
According to the second position detection device, the time that increases in the processing time related to position detection is greater than the time required for calculating the remaining movement amount compared to the case where the total movement amount is measured by the first detection means. The time for converting the remaining movement amount into the voltage amount and the time for judging the output reversal of the comparison means, and the time for the measurement processing by the second detection means is also A / D converted. As in the case where the driven member is moved, the processing time can be further reduced as compared with the case where the position measurement processing is performed at every time interval in which the driven member moves.

  In a preferred embodiment of the present invention, the conversion means outputs the voltage amount to the comparison means when the first detection means counts the number of first scales calculated by the calculation means. The first detection means includes position pulse generation means for generating a pulse for each predetermined cycle or predetermined phase of the position signal, and the amount of movement of the driven member using the position pulse as the first scale. Is detected. As a more specific example, the position signal generating means includes a first position signal as the position signal, a second position signal that is 90 degrees out of phase with the first position signal, and the first position signal. A third position signal in which the polarity of the signal is inverted, and the position pulse generating means includes second comparing means for comparing the first position signal and the second position signal; Position signal and third comparison means for comparing the third position signal with each other, and the position pulse is generated each time the output of either the second or third comparison means is inverted.

  According to the present invention, the processing time of the microcomputer can be greatly reduced, and a cheaper microcomputer can be selected.

Hereinafter, preferred embodiments of the present invention will be described based on examples with reference to the drawings.
FIG. 1 shows the configuration of an autofocus single-lens reflex camera according to an embodiment of the present invention.
In the figure, 1 is an autofocus interchangeable lens, 2 is a focus unit including an optical lens for focusing on a subject and a mechanical mechanism that holds the optical lens and moves in the optical axis direction, and 3 indicates a focus unit 2. A motor unit 4 including a motor that is a driving source for moving in the optical axis direction and a plurality of gear trains for transmitting the driving force of the motor, 4 is a part of the gear in the focus unit 3, and is called a pulse plate A circular plate with magnetized surroundings is connected, and the pulse plate rotates in accordance with the rotation of the motor. The pulse is rotated by an element called an MR element and output, and output from an amplifier or comparator. This is a detector configured to be read by the lens microcomputer 7 through an electric circuit. This detector may be of a type that detects transmission or reflection of light rays such as a photo interrupter or a photo reflector, in addition to a magnetic flux detection device such as an MR element or a Hall element.

  Reference numeral 6 denotes an EEPROM in which various information relating to the interchangeable lens is stored in advance. In this embodiment, for example, data for comparison with an output value related to the speed from the detector 4 is stored. Reference numeral 7 denotes a lens microcomputer that controls all of the lens 1. The functions of the lens microcomputer 7 include a general-purpose I / O port, a serial communication function, a timer counter function, an A / D function, a D / A function, and a plurality of interrupt input functions using external terminals. Reference numeral 8 denotes a contact unit for communication between the camera and the lens. A plurality of metal protrusions are projected on the camera side, and a metal piece is embedded on the lens side so as to contact the protrusions. A power supply terminal, a GND terminal, an input terminal, an output terminal, a synchronous clock terminal, and the like are connected to the camera-side protrusion, and are configured to come into contact with the lens-side protrusion when the lens is attached to the camera. The camera-lens communication and power supply by synchronous serial communication are received through the contact.

  Reference numeral 11 denotes a distance measuring unit for camera autofocus. The distance measuring unit 11 is configured to measure the distance to the subject. There is no problem with the so-called phase difference method, which is the mainstream of the current autofocus, in addition to the type in which the distance measurement unit 11 performs distance measurement by the time when infrared light, sound waves, etc. reciprocate between the camera and the subject. Reference numeral 12 denotes a camera microcomputer that controls all of the cameras. The camera microcomputer 12 is configured to determine the amount of movement of the focus unit 2 from the communication with the lens microcomputer 7 and the output value from the distance measuring unit 11. Reference numeral 13 denotes a camera body. The camera 13 has various other functions, but these functions are irrelevant to the present invention, and thus description thereof is omitted. Moreover, the solid line arrow of FIG. 1 means an electrical connection, and a dotted line means a mechanical connection. The one-point difference line represents the optical axis.

The operation of the camera 13 and the lens 1 will be described based on the above configuration.
The camera 13 has a switch (not shown). When the switch is operated by the user, the camera microcomputer 12 operates the distance measuring unit 11. The distance measuring unit 11 measures the distance to the subject and outputs the result to the camera microcomputer 12. The camera microcomputer 12 transmits the distance measurement result to the lens microcomputer 7 through the contact unit 8, and the lens microcomputer 7 calculates the shift amount and the moving direction of the focus unit 2 from the current position based on the received distance measurement result. It operates to move the focus unit 2 by the shift amount. The lens microcomputer 7 applies a voltage to the motor in the motor unit in order to move the focus unit 2 in the set direction. When the motor is started, the gear in the motor unit 3 rotates, and when the backlash between the gears is clogged, the driving force is transmitted to the focus unit 2 and the focus lens starts moving. The pulse plate connected to a part of the gear in the motor unit rotates in synchronism with the rotation of the gear, and the MR element in the detector 4 detects the output change accompanying the rotation of the pulse plate and sends the rotation amount to the lens microcomputer 7. And transmit as rotational speed.

FIG. 3 is an electric circuit diagram for detecting the output from the MR element mounted in the detector 4 by the lens microcomputer 7. FIG. 4 shows an output waveform of each element in FIG. The operation of the camera shown in FIG. 1 will be described with reference to FIGS.
Two MR elements are mounted in the detector 4 and are arranged at positions that are 90 ° out of phase with respect to the magnetic field intensity period from the magnetized pulse plate. The waveforms when one MR element is A and the other is B are the Aanl and Banl waveforms in FIG. From this waveform, it can be seen that the phase is shifted by 90 ° while the motor is rotating in a predetermined direction, and the phase of the Banl signal is advanced. When the motor rotates in the opposite direction, the phase of the Banl signal is delayed by 90 °.
VR3 and VR4 in FIG. 3 are volume resistors for adjusting the offset of the MR element A and MR element B. Normally, the offset amount of the MR element itself is very small and can be omitted. Vref is a reference voltage divided by the resistors R3 and R4. Usually, R3 = R4 and Vref = 1/2 VCC.

  AMP1 is a Banl output inverting amplifier using Vref as a reference voltage, and the amplification factor is determined by resistors R6 and R5. In this embodiment, R6 = R5 and / Banl, which is the inverted output of Banl, is output. It can be confirmed from FIG. 4 that / Ban is inverted with respect to Banl. COMP1 is a comparator that compares the reference voltage Vref with the Aanl waveform. This converts the analog signal waveform of Aanl into a digital signal waveform called Apls. This Apls signal is connected to the digital input terminal of the lens microcomputer 7. COMP2 is a comparator that compares the reference voltage Vref with the Banl waveform. This converts the analog signal waveform of Banl into a digital signal waveform called Bpls. This Bpls signal is connected to the digital input terminal of the lens microcomputer 7.

  COMP3 is a comparator that compares the Aanl signal and the Banl signal waveform. This compares the voltage values of the Aanl signal and the Banl signal, and converts the result into a digital signal waveform called AvsB. The AvsB signal is configured to output a Hi level signal when the voltage of the Aanl signal is higher than the voltage value of the Banl signal. COMP4 is a comparator that compares the Aanl signal and the / Banl signal waveform. This compares the voltage values of the Aanl signal and the / Banl signal, and converts the result into a digital signal waveform of Avs / B. The Avs / B signal is configured to output a Hi level signal when the voltage of the Aanl signal is higher than the voltage value of the / Banl signal.

  COMP5 is a comparator that compares the Aanl signal with the analog signal output Vstop voltage from the D / A function built in the lens microcomputer 7. This compares the voltage values of the Aanl signal and the Vstop signal, and converts the result into a digital signal called Astp. The Astp signal is configured to output a Lo level signal when the voltage of the Aanl signal is higher than the voltage value of the Vstop signal. COMP 6 is a comparator that compares the Banl signal with the analog signal output Vstop voltage from the D / A function built in the lens microcomputer 7. This compares the voltage values of the Banl signal and the Vstop signal, and converts the result into a digital signal called Bstp. The Bstp signal is configured to output a Lo level signal when the voltage of the Banl signal is higher than the voltage value of the Vstop signal. VCC is a power source supplied from the camera 13.

FIG. 5 is an operation signal diagram in which the operation in FIG. 3 is simplified. The method for detecting the amount of rotation of the motor will be described in detail with reference to FIGS.
When the signal from the MR element A (Aanl signal) is expressed as an A signal and the signal from the MR element B (Banl signal) is expressed as a B signal, the A signal and the B signal are respectively sent from the A / D converter in the lens microcomputer 7. Use to detect.

First, it can be seen from FIG. 5 that the voltage hardly varies at the peak points of the A signal and the B signal. Therefore, even if the voltages of the A signal and the B signal are detected as they are, the detected voltage value cannot be recognized as the same movement amount because the slope of the signal change is different between the peak point and the change point.
Therefore, when comparing the signals A and B and A and / B as shown in FIG. 5, the A signal rises in the region A> B and A </ B, and the B signal in the region A> B and A> / B. It can be seen that the A signal falls in the region A <B and A> / B, and the A signal falls in the region A <B and A </ B. In other words, the magnitude of each signal voltage is compared, the A signal and the B signal are read by the A / D converter in the above-described state, added in the rising state, and in the falling state, the difference between the current detection voltage and the previous detection voltage Can be read as an accumulated movement amount from the stop position. The AvsB signal and the Avs / B signal in FIG. 3 are used as logic signals when determining which of the Aanl signal or the Banl signal is read.

However, as described above, when the Aanl signal and the Banl signal are always read in accordance with the switching between the AvsB signal and the Avs / B signal, the processing of the lens microcomputer 7 becomes enormous, and the motor is being driven. Other processing is almost impossible. We will continue to explain that point further.
FIG. 6 is a diagram for explaining stop position detection according to the present embodiment. As described above, the lens microcomputer 7 cannot perform other processing by the method of always reading the MR sensor output signal. Therefore, in this embodiment, as shown in FIG. 6, the comparator COMP and a D / A converter built in the lens microcomputer 7 are used. The MR sensor signal is input to the negative input terminal of COMP, and the D / A converter signal is input to the positive terminal.

  While the motor is rotating, a sine wave signal is output from the MR sensor, but it is only necessary to stop the focus unit 2 accurately at the target position. The voltage value to be the position is obtained by calculation in advance, and the voltage obtained by the calculation is output by the D / A converter immediately before the voltage value is reached, and at the same time, the COMP output connected to the external interrupt terminal of the lens microcomputer 7 Processing to interrupt the microcomputer with the rising edge signal. That is, when the position to be stopped is reached, an interruption is generated in the lens microcomputer 7, and the focus unit 2 can be stopped with high accuracy by prohibiting the motor drive by the interruption process. In FIG. 6, for example, the target stop position voltage V1 is calculated in advance, and V1 is generated by the D / A converter immediately before the stop position. If the target stop position voltage is V2, V2 is calculated by the D / A converter immediately before the stop position. It will be good to generate. The actual flow is to calculate the stop voltage before driving the motor and only output the voltage calculated just before the stop, so the load related to the processing of the lens microcomputer 7 is directly applied by the A / D converter described above. Compared to the reading type, it can be determined to be equal to zero.

  Further, the position immediately before the stop described above can be easily determined by using the Apls signal and Bpls signal obtained by converting the Aanl signal and the Banl signal into digital signals in FIG. 3 and the AvsB signal and the Avs / B signal. For example, within one cycle of the A signal which is the MR sensor signal of FIG. 5, it can be divided into four areas as shown in the figure, and it can be determined that these four are always output repeatedly. If the period of the A signal is 1000 pulses in the resolution of D / A conversion, if the target position is 900 pulses, 900 / (1000/4) = 3.6, which is 0.6 in the fourth area after the third division. X (1000/4) = 150th pulse is calculated. For easy understanding, when the start position is the position within the rising edge of the A signal in FIG. 5 and the lowest voltage C position, the falling signal of the B signal which is the signal in the fourth area is read, and the 150th pulse This is the position where the voltage is generated. When the start position is deviated, the deviated voltage value may be added to the voltage value of the 150th pulse (the result of addition may be the fourth division, but in this case, within the rising position of the A signal, that is, It can be determined that it is in the first area of the next cycle). That is, the boundary where A <B and A </ B> in FIG. 5 (in FIG. 3, when the AvsB signal is Lo and the Avs / B signal is Lo) is detected, and the voltage corresponding to the 150 pulse position is D / A at that timing. When the output is output by the converter and the output change point of the comparator is detected, the stop position accuracy can be improved by stopping the motor. Further, even when the Apls signal and the Bpls signal are used as the division position detection signals, the same control can be performed because the initial position is different from the above-described value.

  Further, when the rotation amount of the motor unit 3 is very small, there is a possibility that the stop position may be reached before the switching of the AvsB signal or the Avs / B signal occurs. In this case, the D / A converter is simultaneously performed with the motor driving. Similar control is possible by applying a predetermined voltage to.

Based on the above, the operation of the lens microcomputer 7 will be described with reference to FIGS. 1 and 3.
The lens microcomputer 7 receives the distance measurement result transmitted from the camera microcomputer 12 through the contact unit 8, calculates the displacement amount and the moving direction of the focus unit 2 from the current position based on the received distance measurement result, and the displacement. It operates to move the focus unit 2 by an amount. The amount of deviation obtained by calculation is the number of pulses when the focus unit 2 is moved. As a precondition for actually performing this calculation, the A / D converter of the lens microcomputer 7 is applied with a power supply voltage of 5V and has an accuracy of 10 bits, and the Aanl signal or Banl signal is 2.5V ± 2.5V. Output an amplitude voltage of. First, when the A / D function is used, if the Aanl amplitude is ± 2.5 V and the phase difference from Banl is 90 °, there is a relationship between sin and cos, so the intersection is √2 / 2 × 2.5 When × 2 = about 3.53 and A / D conversion is performed for an amplitude of about 3.53 V, 3.53 V / 5 V × 1024 bits = about 723. At the intersection of the Aanl signal and the Banl signal, the low voltage is 5V / 3.53V / 2 = about 0.708V, and the high voltage is 3.53V + 0.708V, which is 4.24V. For these reasons, the resolution of the movement amount in A / D conversion is 723 divisions (pulses) at the peak-to-peak amplitude, and as a result of calculating the deviation amount with this as the minimum resolution, movement of 10,000 pulses is required. In this case, the target position is 10000/723 pulses = 13 change point passes + 601 pulses.

  Here, if the start position is within the falling position of Banl from the state of the AvsB signal and the Avs / B signal, the 13th division takes into account that the signal reading is repeated in 4 cycles and 13 divisions / 4 cycles In this case, 0.25 = 3 + 0.25 and 0.25 is a division position one position ahead of the current position, and it can be determined that it is within the rising division of the A signal. Therefore, as a result of reading the current voltage value of the Aanl signal with the A / D converter, the lowest voltage value is 0.708 V (for the sake of easy understanding) (in the case of an intermediate voltage, the result of adding the voltages) The division position, the target pulse, and the target voltage are determined and corrected), and the voltage of the 601 pulse is 601/723 × 3.53V + 0.708V = about 3.64V. That is, this voltage is a voltage output by the D / A converter.

  In summary, the lens microcomputer 7 terminates the calculation before driving the motor and drives the motor. The AvsB signal and the Avs / B signal are detected with a period that does not skip, and the 13th period is counted. When switching in the thirteenth cycle is detected, the D / A converter outputs 3.64 V to the Vstop signal, and since it is the rising signal detection of the Aanl signal, it is set so that an interrupt can be made at the falling edge of the Astp signal. The lens microcomputer 7 continues other processes until an interrupt signal is input. When the interrupt signal is input, the driving of the motor is stopped. The lens microcomputer 7 determines that the focus unit 2 has stopped at a predetermined position by stopping the motor, and sends information on the motor stop to the camera microcomputer 12.

FIG. 7 is a flowchart showing processing relating to autofocus of the camera microcomputer 12. The autofocus operation of the camera shown in FIG. 1 will be described with reference to FIG.
The camera 13 shown in FIG. 1 is equipped with a release button (not shown), and the user prompts the camera 13 to operate with this release button. The release button is a two-stage stroke switch that is set so that AF operation is performed when only the first stage (one stroke) is ON, and release operation is performed when the second stage is ON. . Hereinafter, the ON in one stroke is referred to as S1, and the ON in the first stroke is referred to as S2.

[Steps 100 and 101]
First, the camera microcomputer 12 determines whether the user has turned on only S1. When nothing is pressed, the process proceeds to step 100, and when it is pressed, the process proceeds to step 102.
[Step 102]
Since S1 is pressed, the camera microcomputer 12 issues a distance measurement start command to the distance measurement unit 11, and measures the distance to the current subject (in the case of the phase difference method, the focus state is detected).

[Step 103]
The distance measurement data is transmitted to the lens microcomputer 7, and the lens microcomputer 7 compares the received distance measurement data with the current position of the focus unit 2, and transmits the result to the camera microcomputer 12 (steps 200 to 203 in FIG. 8). The camera microcomputer 12 determines the received focus state, does nothing if the subject is in focus, and proceeds to step 106 to end the AF operation.
[Step 104]
If it is determined in step 103 that the subject is not in focus, the focus unit 2 is moved and communication for focusing is transmitted to the lens microcomputer 7. The data communicated at this time is the above-mentioned distance measurement information and status data for instructing the lens microcomputer 7 to permit lens correction.

[Step 105]
When the movement of the focus unit 2 is completed (step 308 in FIG. 9), the lens microcomputer 7 transmits the fact as status information to the camera microcomputer 12 (steps 200 to 203 in FIG. 8). The camera microcomputer 12 confirms the lens status information and waits until the correction is completed.
[Step 106]
If the camera microcomputer 12 determines in step 105 that lens correction has been completed, status information prohibiting lens correction is transmitted to the lens microcomputer 7, and the focus correction process is terminated.

FIG. 8 is a flowchart relating to the communication interruption process of the lens microcomputer 7. The operation of this embodiment will be described with reference to FIG.
[Steps 200 and 201]
First, when communication is transmitted from the camera microcomputer 12, the command data transmitted from the camera microcomputer 12 is confirmed. The command data is code data representing a request content from the camera microcomputer 12 to the lens microcomputer 7, and the lens microcomputer 7 analyzes the code data to determine a request from the camera. The contents of the command data include a movement permission command for the focus unit 2, a movement stop command for the focus unit 2, a transmission request for information related to optics (focal length, FNo, lens status information, etc.), a reception request for distance measurement information, etc. The microcomputer 7 analyzes these command data.

[Step 202]
The lens microcomputer 7 analyzes the command data and transmits necessary data to the camera microcomputer 12. At this time, when the command data received from the camera microcomputer 12 is lens status information, the lens microcomputer 7 determines whether the focus unit 2 is currently moving or stopped, and transmits status information transmission data to the camera microcomputer 12. Record the result. This status information is transmitted to the camera microcomputer 12 when the next communication from the camera microcomputer 12 is received. If the command data received from the camera microcomputer 12 is a distance information reception request, the lens microcomputer 7 receives the distance information from the camera microcomputer 12 in the next communication and stores the data in the internal memory.
[Step 203]
When the command analysis by communication from the camera microcomputer 12, the data setting, and the transmission process are completed, the interrupt process is terminated.

FIG. 9 is a flowchart of a program relating to the movement of the focus unit 2 of the lens microcomputer 7. The description will be continued based on FIG.
[Steps 300 and 301]
When the lens 1 is attached to the camera 13, power is supplied to the lens microcomputer 7 through the contact unit 8, and the lens microcomputer 7 executes a reset process. When the processing is completed, the state of the switches attached to the lens 1 (not shown) is detected and stored in the internal memory. These switches include, for example, a switch for switching between two operation modes of auto focus and manual focus, and a switch for selecting operation / non-operation of camera shake correction.

[Step 302]
The lens microcomputer 7 and the camera microcomputer 12 are configured to communicate with each other through the contact unit 8, and the lens microcomputer 7 confirms whether the correction permission for the focus unit 2 is transmitted from the camera microcomputer 12. If the correction permission has not been transmitted, the process returns to step 301 to detect the state of the switches again. The communication from the camera is processed by the interrupt processing (FIG. 8) of the lens microcomputer 7, and necessary information (for example, correction permission, etc.) is stored in the internal memory of the lens microcomputer 7 in the interrupt processing. Is done.

[Step 303]
When the permission for correction of the focus unit 2 is transmitted from the camera microcomputer 12 in step 302, the current position information based on the voltage, the position information to be stopped, and the voltage value are calculated and stored in the internal memory. The lens microcomputer 7 starts the movement of the focus unit 2 by driving the motor unit 3 immediately after completing each calculation. At this time, a flag for informing the camera microcomputer 12 that the focus unit 2 is moving is set, and the camera microcomputer 12 is communicated. The camera microcomputer 12 recognizes that the focus unit 2 is moving through this communication.

[Step 304]
The lens microcomputer 7 counts the switching between the AvsB signal and the Avs / B signal, which are the respective coarse movement amounts output from the detector 4, and compares the predetermined amount with a predetermined amount, and waits until the predetermined amount is reached. . The predetermined amount referred to here is a count number for detecting a stop division position by the AvsB signal and the Avs / B signal.
[Step 305]
If the predetermined amount is reached in step 304, the result calculated before driving the motor unit 3 is read from the memory, and a predetermined voltage is output by the D / A converter. Also, one of the two external interrupts is permitted from the memory value.

[Step 306]
The lens microcomputer 7 discriminates the target speed information Vm set in advance and the current speed of the focus unit 2, and changes the voltage applied to the motor unit 3 so as to reach the target speed. Note that the current speed can be calculated from the number of changes in the Apls signal or Bpls signal per unit time.
[Step 307]
The lens microcomputer 7 determines whether or not the voltage to the motor unit 3 is supplied. If the voltage is supplied, the process proceeds to step 305.

[Step 308]
The lens microcomputer 7 determines that the focus unit 2 has moved by a predetermined amount of movement based on the distance measurement information transmitted from the camera microcomputer 12, and is moving to inform the camera microcomputer 12 that the focus unit 2 is stopped. The flag is cleared and the camera microcomputer 12 is communicated. Upon receiving this communication, the camera microcomputer 12 determines that the focus unit 2 has reached a predetermined position, and proceeds to the next operation.

FIG. 10 is a flowchart of a program relating to an interrupt process by an external interrupt of the lens microcomputer 7. The explanation will be continued based on this figure.
When the COM 5 or 6 in FIG. 3 or the output of COM in FIG. 6 (Astp or Bstp in FIG. 3) is inverted, the lens microcomputer 7 uses this as an interrupt signal to start the interrupt processing in FIG.
[Steps 400, 401, 402]
The lens microcomputer 7 immediately stops the voltage supply to the motor unit 3 and ends the interrupt process.
The fact that the supply of voltage to the motor unit 3 has been stopped is determined by the lens microcomputer 7 and the lens driving process is completed (steps 307 and 308 in FIG. 9), which is communicated to the camera microcomputer 12 (FIG. 8) and focused. The correction ends (steps 105 and 106 in FIG. 7).

The above is the description of the embodiment related to the present invention. In this embodiment, the description is made on the assumption that the lens interchangeable single-lens reflex camera is used. However, the control apparatus equipped with the means for detecting the rotation amount and the movement amount is described. If there is, it corresponds to all of them. Needless to say, the present invention is applied to an extremely simple control method especially for the purpose of improving detection accuracy.
By using the present invention, the processing time of the microcomputer can be greatly reduced, and a cheaper microcomputer can be used.

  In the above description, the second detection means converts the position (residual movement amount) within the range of the first scale obtained by dividing one cycle of the output of the MR element A into the target movement amount into a voltage amount, This is compared with the voltage amount output from the MR element A, and the matching point is detected as the target position of the focus lens. The output of the position sensor such as the MR element A is directly A / D converted. This may be the current position of a driven member such as a focus lens. This A / D conversion means can be configured using the D / A conversion function of the lens microcomputer 7. That is, sequential digital values are input to the D / A conversion function to convert them into voltage amounts, and the point where the voltage amount and the output of the position sensor match is detected as the current position of the driven member.

1 is an internal block diagram of an autofocus camera and an interchangeable lens according to an embodiment of the present invention. It is explanatory drawing of the conventional movement amount detection system. It is a circuit diagram of a movement amount detection system. FIG. 4 is a time chart of each terminal in the circuit diagram of FIG. 3. It is a principle diagram of movement amount detection. It is explanatory drawing regarding stop position accuracy improvement. It is a flowchart figure of a camera microcomputer. It is a flowchart figure of a lens microcomputer. It is a flowchart figure of a lens microcomputer. It is a flowchart figure of a lens microcomputer.

Explanation of symbols

1: Autofocus interchangeable lens 2: Focus unit 3: Motor unit 4: Detector 6: EEPROM
7: Lens microcomputer 8: Contact unit 11: Distance measuring unit 12: Camera microcomputer 13: Camera body

Claims (6)

First detection means for measuring the amount of movement of the driven member with a first scale;
Second detection means for measuring the amount of movement of the driven member with a second scale having a smaller interval than the first scale;
The driven member is driven toward a desired target position, and the first detection means and the second detection means are switched and used in accordance with the remaining amount of movement to the target position. And a drive control means for stopping the driven member when it is detected that the target position has been reached.   The drive control means uses the first detection means when the remaining moving amount is larger than a predetermined value, and uses the second detection means when the remaining movement is smaller than the predetermined value. The position detection apparatus according to 1. Position signal generating means for generating a position signal having a voltage amount corresponding to the position of the driven member within each period, which is a periodic signal generated according to the movement of the driven member;
A first detecting means for detecting a movement amount of the driven member by a first scale from the position signal;
The target movement amount of the driven member represented by the number of second graduations having a smaller interval than the first graduation is changed to the number of the first graduations and the remaining movement amount less than the first graduation interval. Computing means for calculating separately;
Conversion means for converting the calculated remaining movement amount into a voltage amount;
Comparing means for comparing the voltage amount output by the converting means with the voltage amount output by the position signal generating means;
When the driven member moves, the first detecting means counts the number of first scales calculated by the calculating means, and the output of the comparing means is reversed, the driven member is moved to the target movement amount. And a second detecting means for detecting the movement of the position detecting device.   The said conversion means outputs the said voltage amount to the said comparison means, when the said 1st detection means counts the number of the 1st scales which the said calculation means calculated. Position detection device.   The first detection means includes position pulse generation means for generating a pulse at a predetermined cycle or a predetermined phase of the position signal, and detects the amount of movement of the driven member using the position pulse as the first scale. The position detection device according to claim 3 or 4, wherein The position signal generating means includes a first position signal as the position signal, a second position signal that is 90 ° out of phase with the first position signal, and a first position signal in which the polarity of the first position signal is inverted. 3 position signal and
The position pulse generating means includes a second comparing means for comparing the first position signal and the second position signal, and a third for comparing the first position signal and the third position signal. 6. The position detecting device according to claim 5, wherein the position pulse is generated each time the output of either the second or third comparing means is inverted.

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