JP6368605B2 - Position detecting device and driving device provided with the same - Google Patents

Description

  The present invention relates to a position detection device and a drive device including the position detection device.

  An imaging device such as a digital still camera or a digital video camera has an autofocus function. In the autofocus function, the position of the focus lens included in the imaging optical system in the imaging apparatus is controlled so that the subject image is focused on the imaging surface. The position control of these focus lenses is performed by feed forward control which is so-called open control or feedback control which is closed loop control. In order to perform feedback control of the focus lens position, position detection means such as a position sensor and means for calculating the lens position using the output of the position sensor are required.

  Various means have been proposed as a focus lens position sensor. For example, using a magnetic scale interlocking with the drive unit and a sensor using a GMR element (Giant Magneto Resistive effect device) that detects a position by detecting a magnetic flux generated from the magnetic scale. A configured two-phase encoder is known.

  In a two-phase encoder using a GMR sensor, the output of the GMR sensor is required to be an ideal sine wave and cosine wave. For this reason, an error included in the output of the GMR sensor is corrected. For example, Patent Document 1 discloses the following technique. That is, first, a plurality of candidate functions are prepared in advance. In operation, the total error signal function contained in the actual GMR output signal is determined for the ideal sine wave. For each candidate function, a value obtained by squaring the value obtained by subtracting the candidate function from the total error signal function is obtained, and a value obtained by integrating the value for one period is obtained. The correction value is determined by selecting a candidate function that minimizes the integrated value. The correction value is used to correct the error of the GMR sensor.

  In the method disclosed in Patent Document 1, since the difference between the total error signal function and the candidate function is integrated, a correction value closest to the error of one cycle can be obtained. On the other hand, the amount of data and the amount of calculation are enormous.

  For example, in the position control of the focus lens or the like at the time of moving image shooting, it is necessary to control the position of the focus lens as a drive unit sequentially and at high speed and accurately. Furthermore, it is required to suppress noise as much as possible in these position controls.

Japanese Patent Laid-Open No. 2006-194661

  An object of the present invention is to provide a position detection device that can easily and easily correct an error included in an output of a sensor used in a two-phase encoder with a small amount of data processing, and a drive device including the position detection device.

According to one aspect of the present invention, the position detection device includes a scale unit and a detection unit disposed to face the scale unit, and a relative movement amount between the scale unit and the detection unit. A position acquisition unit that generates a two-phase periodic position information signal that includes a first position information signal and a second position information signal that is 90 ° out of phase with the first position information signal. And the values of the normalized position information signals when the absolute values of the normalized position information signals obtained by normalizing the amplitudes of the measured position information signals to a predetermined amplitude are equal to each other , A correction coefficient determining unit for determining a correction coefficient based on a difference from the value of the normalized position information signal when the absolute values of the normalized position information signal are equal to each other; and a signal equal to the signal period of the position information signal A pre-prepared correction reference function having a period A correction value determining unit for calculating a correction value based on the correction value function obtained by multiplying the correction coefficient, the position information signal by adding or subtracting the correction value for each of the position information signal A correction unit that calculates a corrected position information signal after correction.
According to one aspect of the present invention, a scale unit and a detection unit disposed to face the scale unit are provided, and the first and second detection units are arranged in accordance with a relative movement amount between the scale unit and the detection unit. A position acquisition unit that generates a two-phase periodic position information signal including one position information signal and a second position information signal that is 90 ° out of phase with the first position information signal; The value of the normalized position information signal when the absolute values of the normalized position information signal obtained by normalizing the amplitude of the position information signal thus obtained to a predetermined amplitude are equal to each other, and each ideal normalized position information signal A correction coefficient determining unit that determines a correction coefficient and an offset correction coefficient based on a difference from the value of the normalized position information signal when the absolute values of the signal are equal to each other, and a signal period equal to the signal period of the position information signal Pre-prepared correction with A correction value determining unit that calculates a correction value based on a correction value function obtained by adding the offset correction coefficient to a value obtained by multiplying the correction function by a quasi-function; and the correction value is assigned to each position information signal. And a correction unit that calculates a corrected position information signal obtained by correcting the position information signal by addition or subtraction.

  According to another aspect of the present invention, the drive device includes a drive unit having a fixed member, a movable unit that moves relative to the fixed member, the position detection device, and a control unit. One of the scale unit and the detection unit is fixed to the fixed member, the other is fixed to the movable unit, and the position acquisition unit is located between the fixed member and the movable unit. The position information signal corresponding to the relative movement amount is generated, and the control unit controls the operation of the drive unit based on the corrected position information signal output from the position detection device.

  ADVANTAGE OF THE INVENTION According to this invention, the position detection apparatus which can correct | amend the error contained in the output of the sensor used for a two-phase encoder with simple and small data processing amount, and a drive device provided with the position detection apparatus can be provided.

FIG. 1 is a block diagram showing an outline of a configuration example of a camera system to which a position detection apparatus according to an embodiment of the present invention is applied. FIG. 2 is a diagram showing an outline of a configuration example of a drive unit that drives a movable unit including a focus lens and a position sensor that detects the position of the movable unit. FIG. 3 is a diagram illustrating an outline of a configuration example of the position sensor. FIG. 4 is an example of a control block diagram for controlling the position of the movable part. FIG. 5 is a block diagram illustrating an outline of a configuration example of the lens control unit. FIG. 6 is a block diagram illustrating an outline of a configuration example of the position calculation unit. FIG. 7 is a diagram for explaining an example of an output of the GMR sensor and an error signal. FIG. 8 is a diagram for explaining an example of the output of the GMR sensor, its error, and a correction value function for correcting the error. FIG. 9 is a diagram illustrating an example of a relationship between an A-phase output and a B-phase output. FIG. 10 is a diagram showing an example of a Lissajous waveform showing the locus of the output relationship between the A-phase output and the B-phase output. FIG. 11 is a flowchart illustrating an example of the position control operation. FIG. 12 is a flowchart illustrating an example of the current position calculation process. FIG. 13 is a diagram for explaining the movement of the movable part in the adjustment operation. FIG. 14 is a flowchart illustrating an example of the adjustment operation. FIG. 15 is a flowchart illustrating an example of the movement control operation. FIG. 16 is a diagram for explaining the relationship between the movement target position and the control target position in the adjustment operation. FIG. 17 is a flowchart illustrating an example of the feedback control process. FIG. 18 is a flowchart illustrating an example of the correction coefficient calculation process. FIG. 19 is a diagram for explaining the movement of the movable part in the movement control operation. FIG. 20 is a diagram for explaining the relationship between the movement target position and the control target position in the movement control operation. FIG. 21 is a flowchart illustrating an example of output correction processing. FIG. 22 is a diagram for explaining an example of the relationship between the output of the GMR sensor, the error signal, the correction value function for correcting the error, the correction method, and the correction result. FIG. 23 is a diagram illustrating an example of a Lissajous waveform showing the locus of the output relationship between the A-phase output and the B-phase output before and after correction. FIG. 24 is a diagram illustrating an example of an FFT analysis result representing a difference in driving sound generated from the movable part depending on whether or not the GMR sensor output signal is corrected.

  An embodiment of the present invention will be described with reference to the drawings. The present embodiment relates to a lens drive in an imaging apparatus, particularly a lens barrel of the imaging apparatus. Hereinafter, in the present embodiment, the present embodiment will be described by taking as an example the control of the lens position that is performed when the focus lens is driven.

  An outline of a configuration example of the camera system 1 according to the present embodiment is shown in FIG. The camera system 1 includes a camera body 30 and a lens barrel 10 connected to the camera body 30. This camera system 1 is a digital camera configured such that a camera body 30 acquires a subject image formed by a lens included in a lens barrel 10 as image data. In the description of the present embodiment, the camera system 1 is assumed to be an interchangeable lens camera in which the camera body 30 and the lens barrel 10 are provided as separate bodies. 1 may be a camera in which a lens barrel and a camera body are integrally provided.

  The camera body 30 includes an image pickup device 31, an image pickup circuit 32, an auto exposure (AE) processing unit 33, an auto focus (AF) processing unit 34, an image calculation unit 35, an image processing circuit 36, and a liquid crystal display ( LCD) driver 37, liquid crystal display (LCD) 38, input unit 39, Body control unit 40, power supply unit 41, nonvolatile memory 42, built-in memory 43, compression / decompression unit 44, and removable memory 45 And a body side interface 46.

  The imaging element 31 has an imaging surface including a plurality of photoelectric conversion pixels. The image sensor 31 receives a subject image (light image) formed by the lens barrel 10 on the imaging surface. The imaging device 31 generates an image signal representing a subject image by photoelectrically converting incident light by each photoelectric conversion pixel.

  The image pickup circuit 32 controls the image pickup device 31 to start and end photoelectric conversion, and controls to read out electric charges accumulated in each pixel by photoelectric conversion as an image signal. The imaging circuit 32 is controlled according to a control signal from the Body control unit 40.

  The AE processing unit 33 has a function of measuring subject luminance with respect to an image signal obtained from the imaging circuit 32. The AE processing unit 33 performs an operation related to exposure in shooting, and calculates, for example, a shutter speed, an aperture value, sensitivity, and the like for obtaining appropriate exposure.

  The AF processing unit 34 detects the focus information of the subject from the image signal. The AF processing unit 34 performs an autofocus operation such as calculation of information necessary for driving the lens of the lens barrel 10.

  The image calculation unit 35 performs image calculation such as addition synthesis of image signals and pixel thinning processing. The image processing circuit 36 performs various image processing such as gradation correction and noise correction on the image signal. The LCD driver 37 drives the LCD 38. The LCD 38 displays the captured image. The input unit 39 is a part for a user to input an operation on the camera body 30.

  The Body control unit 40 comprehensively controls the camera body 30. The objects controlled by the body control unit 40 are the imaging circuit 32, the AE processing unit 33, the AF processing unit 34, the image calculation unit 35, the image processing circuit 36, the LCD driver 37, and the like, which are connected via the bus line 47. Has been. Further, the Body control unit 40 is connected to the nonvolatile memory 42, the built-in memory 43, the compression / decompression unit 44, the removable memory 45, and the bus line 47. The power supply unit 41 supplies power to each part of the camera body 30.

  Program data to be operated by the body control unit 40 is recorded in the nonvolatile memory 42. The built-in memory 43 temporarily holds data when the image calculation unit 35 and the image processing circuit 36 perform various processes. The compression / decompression unit 44 performs compression processing or expansion processing on the captured image data. The removable memory 45 is a memory for recording photographed image data. The body side interface 46 is an interface for communicating with the lens barrel 10.

  The body control unit 40, the AE processing unit 33, the AF processing unit 34, the image calculation unit 35, the image processing circuit 36, the compression / decompression unit 44, and the like, for example, use a central processing unit (CPU) or an application specific integrated circuit (ASIC). Including various operations.

  Next, the lens barrel 10 will be described. The lens barrel 10 includes a fixing member 11, a focus lens 12, a zoom lens 13, a diaphragm 14, a focus lens driver 15, a zoom lens driver 16, a diaphragm driver 17, a position sensor 18, and a lens control unit. 19, a lens operation unit 20, a nonvolatile memory 21, and a lens side interface 22.

  The fixed member 11 holds the focus lens 12, the zoom lens 13, and the diaphragm 14. The focus lens 12 can move in the lens barrel 10 in the optical axis direction. The focus lens 12 is driven so as to change the focus position of the subject image. The zoom lens 13 is movable in the lens barrel 10 in the optical axis direction. The zoom lens 13 is driven manually or automatically so as to change the photographing magnification and the focal length. In the diaphragm 14, the amount of opening changes in order to change the amount of light of the subject image guided to the image sensor 31.

  The focus lens driver 15 is a circuit that drives the focus lens 12 based on an operation control signal output from the lens control unit 19. The zoom lens driver 16 is a circuit that drives the zoom lens 13 based on an operation control signal output from the lens control unit 19. The aperture driver 17 is a circuit that drives the aperture 14 based on an operation control signal output from the lens control unit 19.

  The position sensor 18 detects the position of the focus lens 12 in the optical axis direction. The position sensor 18 functions as a position acquisition unit and outputs a position information signal. Based on the output of the position sensor 18, the position of the focus lens 12 is calculated.

  The lens control unit 19 controls each part in the lens barrel 10 in an integrated manner. The lens control unit 19 includes a CPU and performs various calculations. The operation of the lens control unit 19 is performed according to a program recorded in a nonvolatile memory 21 described later. The lens control unit 19 may include an ASIC or the like. For example, the lens control unit 19 controls the operations of the focus lens 12, the zoom lens 13, and the diaphragm 14. Further, the lens control unit 19 acquires the position of the focus lens 12 from the position sensor 18.

  The lens operation unit 20 is a part for a user to input an operation on the lens barrel 10. The nonvolatile memory 21 stores a program for the lens control unit 19 to perform a control operation, adjustment values such as the positions of the focus lens 12, the zoom lens 13, and the diaphragm 14, and the like. The lens side interface 22 is connected to the body side interface 46. The lens side interface 22 is an interface circuit for transmitting and receiving control signals between the camera body 30 and the lens barrel 10.

  A drive mechanism for moving the focus lens 12 along the optical axis direction and a position detection mechanism for detecting the position of the focus lens 12 in the optical axis direction will be described. FIG. 2 shows an outline of an external appearance of a configuration example of the position sensor 18 included in the drive mechanism and the position detection mechanism of the focus lens 12.

  As shown in FIG. 2, the movable unit 122 including the focus lens 12 is moved in the optical axis direction along the fixed member 11 by the driving unit 123. The drive unit 123 includes a drive mechanism using, for example, a voice coil motor (VCM). That is, the movable coil 122 has a VCM movable coil 124 fixed thereto. On the other hand, the fixed member 11 is provided with a VCM stator 126 including a permanent magnet so as to face the movable coil 124. As described above, the movable portion 122 is moved by the VCM including the stator 126 and the movable coil 124.

  In addition, although the example which the movable part 122 moves by VCM was shown here, it is not restricted to this system, Another system may be used. For example, a driving method using a stepping motor or an ultrasonic motor may be applied.

  In the present embodiment, as the position sensor 18, a GMR sensor 182 as a detection unit using a magnetoresistive element such as a GMR element (Giant Magneto Resistive effect device) is used. A GMR element is an element whose electrical resistivity changes according to the magnitude of the input magnetic flux density. The GMR sensor 182 using such a GMR element is fixed to the fixing member 11. A magnetic scale 188 is fixed to the movable part 122 including the focus lens 12. The GMR sensor 182 and the magnetic scale 188 are disposed to face each other.

  The magnetic scale 188 is alternately magnetized with N poles and S poles every predetermined position period. Here, the length of the position period between the N pole and the S pole is referred to as one magnetization pitch. Since the electrical resistivity of the GMR element included in the GMR sensor 182 changes according to the magnetic flux density by the magnetic scale 188, the GMR sensor 182 outputs an electrical signal corresponding to the position relative to the magnetic scale 188. That is, the GMR sensor 182 outputs a periodic position information signal for each magnetization pitch according to the movement of the movable portion 122.

  The GMR sensor 182 may be fixed to the movable portion 122 and the magnetic scale 188 may be fixed to the fixed member 11. Further, the position sensor 18 is not limited to the GMR sensor, and other sensors may be used.

  The configuration of the GMR sensor 182 and the magnetic scale 188 will be further described with reference to FIG. The GMR sensor 182 includes a first GMR sensor 184 and a second GMR sensor 185. The first GMR sensor 184 and the second GMR sensor 185 are arranged in a direction in which the magnetization of the magnetic scale 188 changes, that is, in the optical axis direction, by a distance that is 1/4 of one magnetization pitch. Yes.

  In the first GMR sensor 184 and the second GMR sensor 185, the electric resistivity changes according to the magnitude of the magnetic flux density. Therefore, when the movable part 122 operates in the optical axis direction, the first GMR sensor 184 and the second GMR sensor 185 The magnitude of the signal output as the position information signal from the second GMR sensor 185 changes according to the magnetization period. Since the first GMR sensor 184 and the second GMR sensor 185 are arranged at positions separated by a quarter magnetization pitch, the two GMR sensor signal outputs that are output according to the amount of movement of the movable part 122 are: The phase is shifted by a quarter period (90 °). Thus, the GMR sensor 182 and the magnetic scale 188 are configured to function as a two-phase linear encoder. The outputs of the first GMR sensor 184 and the output of the second GMR sensor 185 are orthogonal to each other. One output of the output of the first GMR sensor 184 and the output of the second GMR sensor 185 is referred to as a sine wave signal, and the other is referred to as a cosine wave signal. The output of the first GMR sensor 184 corresponds to the first position information signal, and the output of the second GMR sensor 185 corresponds to the second position information signal.

  In order to detect the position with a position resolution finer than the magnetization position period of the magnetic scale 188, the position sensor 18 performs interpolation processing on the sine wave signal and cosine wave signal, which are the above-described two-phase outputs, and performs detailed detection. The position needs to be calculated. In the interpolation process, for example, there is a method of calculating a phase angle corresponding to the phase relationship of each signal by performing an arctangent operation on a sine wave signal and a cosine wave signal. In this method, the relative position within the magnetization position period of the magnetic scale 188 can be calculated based on the phase angle of the two-phase output.

  Next, FIG. 4 shows a control block diagram when the position control of the movable portion 122 is performed. The lens control unit 19 calculates the position of the focus lens 12 in the optical axis direction based on the output of the position sensor 18, and uses the calculation result to cause the position of the focus lens 12 to follow the target position by feedback control. To control.

  As shown in FIG. 4, the target position instruction unit 201 in the lens control unit 19 sets the target position of the movable unit 122. Further, the position calculation unit 204 in the lens control unit 19 calculates the current position of the movable unit 122 as corrected position information based on the output of the position sensor 18. The calculation unit 202 calculates a difference between the target position of the movable unit 122 and the corrected position information indicating the current position as a control position deviation. An operation amount calculation unit 203 in the lens control unit 19 calculates an operation amount based on the control position deviation. The operation amount calculated by the operation amount calculation unit 203 is transmitted to the focus lens driver 15. The focus lens driver 15 operates the drive unit 123 by supplying power to the drive unit 123 for moving the movable unit 122 based on the operation amount. The position of the movable part 122 is detected by the position sensor 18. The detection result of the position sensor 18 includes a detection error. In the present embodiment, the position calculation unit 204 corrects an error included in the output of the position sensor 18.

  A configuration for controlling the position of the movable unit 122 included in the focus lens 12 included in the lens control unit 19 will be further described. FIG. 5 is a block diagram showing a functional configuration included in the lens control unit 19. The lens control unit 19 includes a position calculation unit 204, a lens control communication interface 205, an operation input interface 206, a memory interface 207, and a focus lens control unit 210.

  The position calculation unit 204 calculates the position of the movable unit 122 based on the signal acquired from the position sensor 18. The lens control communication interface 205 performs transmission / reception of communication signals and processing of signals with the lens side interface 22. The operation input interface 206 acquires an operation signal related to an operation input to the lens operation unit 20. The memory interface 207 transmits / receives data to / from the nonvolatile memory 21.

  The focus lens control unit 210 calculates an operation amount to be output to the focus lens driver 15 so that the position of the focus lens 12 matches the target position. The focus lens control unit 210 includes a target position instruction unit 201, a calculation unit 202, and an operation amount calculation unit 203.

  The target position instruction unit 201 acquires an operation signal from the operation input interface 206. In addition, the target position instruction unit 201 acquires a control signal from the camera body 30 from the lens control communication interface 205. The target position instruction unit 201 calculates a control target position, which is a target position for each periodic process, based on these signals representing the movement target position. The control target position is output to the calculation unit 202.

  The calculation unit 202 acquires the current position of the movable unit 122 from the position calculation unit 204 and acquires the control target position from the target position instruction unit 201. The calculation unit 202 calculates a difference between the control target position and the current position of the movable unit 122 as a control position deviation. The operation amount calculation unit 203 calculates an operation amount for driving the focus lens driver 15 based on the control position deviation calculated by the calculation unit 202.

  Note that the position calculation unit 204 and the focus lens control unit 210 acquire necessary programs, parameters, and the like from the nonvolatile memory 21 via the memory interface 207 and perform various calculations.

  Next, the position calculation unit 204 in the lens control unit 19 will be described. The output signal of the first GMR sensor 184 and the output signal of the second GMR sensor 185 are each transmitted to the position calculation unit 204 in the lens control unit 19. The position calculation unit 204 calculates the position of the movable unit 122 based on the output signal of the first GMR sensor 184 and the output signal of the second GMR sensor 185.

  FIG. 6 is a block diagram illustrating an outline of a configuration example of the position calculation unit 204 in the lens control unit 19. Hereinafter, a signal based on the output signal of the first GMR sensor 184 is referred to as an A-phase signal, and a signal based on the output signal of the second GMR sensor 185 is referred to as a B-phase signal. The A-phase signal output from the first GMR sensor 184 and the B-phase signal output from the second GMR sensor 185 are amplified by the amplifier circuit 189 and input to the position calculation unit 204.

  The position calculation unit 204 includes an A / D conversion unit 242, a correction coefficient determination unit 243, a correction unit 251, a phase angle calculation unit 256, a calculated position output unit 258, and a storage unit 260. The correction coefficient determination unit 243 includes a first normalization correction unit 244 and a second normalization correction unit 246. The correction unit 251 includes a first error correction unit 252 and a second error correction unit 254.

  The A / D conversion unit 242 converts the A-phase signal output from the first GMR sensor 184 and amplified, and the B-phase signal output from the second GMR sensor 185 into a digital signal.

  The signal output from the GMR sensor includes amplitude deviation and offset deviation. The correction coefficient determination unit 243 performs a correction process for correcting the amplitude shift and the offset shift so that the offset levels of the signals after AD conversion are aligned and the amplitude is aligned to a constant value. Hereinafter, this correction processing is simply referred to as normalization. The first normalization correction unit 244 performs an operation for normalizing the amplitude deviation and the offset deviation so that the A-phase signal output from the first GMR sensor 184 has a predetermined amplitude and a predetermined offset level. Do. Similarly, the second normalization correction unit 246 normalizes the amplitude deviation and the offset deviation so that the B phase signal output from the second GMR sensor 185 has a predetermined amplitude and a predetermined offset level. Perform the operation. The normalized A-phase signal and B-phase signal are referred to as normalized position information signals.

  Further, the correction coefficient determination unit 243 uses the value of the normalized position information signal when the absolute value of the A-phase normalized position information signal is equal to the absolute value of the B-phase normalized position information signal, Determine the correction factor. The correction coefficient determination unit 243 stores the determined correction coefficient in the storage unit 260 as the correction coefficient table 262.

  The correction unit 251 performs a correction process for correcting an error between the A-phase and B-phase normalized position information signals and ideal sine waves and cosine waves. That is, the first error correction unit 252 performs correction processing on the A-phase signal output from the first normalization correction unit 244. Similarly, the second error correction unit 254 performs correction processing on the B-phase signal output from the second normalization correction unit 246. The A-phase signal and the B-phase signal that have been subjected to the correction process will be referred to as corrected position information signals. The correction unit 251 uses a correction reference function, which will be described in detail later, and the correction coefficient determined by the correction coefficient determination unit 243 in the correction process.

  The phase angle calculation unit 256 acquires the A-phase signal output from the first error correction unit 252 and the B-phase signal output from the second error correction unit 254, and based on them, the magnetic scale The phase angle for each magnetization pitch period is calculated. The phase angle calculation unit 256 is a ratio of the A phase signal (sine wave signal) output from the first error correction unit 252 to the B phase signal (cosine wave signal) output from the second error correction unit 254. The arc tangent operation is performed. The phase angle calculation unit 256 calculates the relative position within the magnetization pitch period of the magnetic scale 188 by multiplying the arc tangent calculation result by the relative position conversion coefficient within the pitch. Information necessary for the calculation performed by the phase angle calculation unit 256 is included in the storage unit 260 as the phase angle calculation table 264.

  The calculated position output unit 258 calculates the position of the movable unit 122 by adding or subtracting the offset obtained by further counting the magnetization pitch to the calculation result of the phase angle calculating unit 256.

  As described above, the position sensor 18 and the position calculation unit 204 constitute a position detection device that detects the position of the movable unit 122.

  Next, an error that occurs in the position detection of the movable part 122 using the position sensor 18 will be described. FIG. 7 is a schematic diagram for explaining two signals of the A phase and the B phase that are output from the GMR sensor 182 in accordance with the position of the movable portion 122. In FIG. 7, the horizontal axis represents time.

  As shown in FIG. 7A, one magnetization pitch is defined according to the position period of the N pole and S pole of the magnetic scale 188. The output of the GMR sensor 182 has periodicity for each magnetization pitch. One magnetization pitch is divided into four states. Each state includes 90 ° phase.

  FIG. 7B shows the output of the normalized GMR sensor 182. FIG. Here, the solid line shows an ideal case of the output waveform of the A phase output from the first GMR sensor 184, and shows a sine wave shape. A broken line indicates an ideal case of the output waveform of the B phase output from the second GMR sensor 185, and indicates a cosine wave shape. An alternate long and short dash line is a waveform indicating the output of the A phase (hereinafter referred to as a (t)) output from the first GMR sensor 184 and includes an error. Therefore, an ideal case indicated by a solid line There is a slight deviation between An alternate long and two short dashes line is a waveform indicating an output of the B phase (hereinafter referred to as b (t)) output from the second GMR sensor 185 and includes an error. There is a slight deviation from the case.

  FIG. 7C shows an ideal output of the A phase output from the first GMR sensor 184 indicated by the solid line and an A phase actually output from the first GMR sensor 184 indicated by the alternate long and short dash line. The error Δd1 existing between the output and the output is shown. FIG. 7D shows an ideal output of the B phase output from the second GMR sensor 185 indicated by a broken line, and B actually output from the second GMR sensor 185 indicated by a two-dot chain line. An error Δd2 existing between the phase outputs is shown. In the present embodiment, the error Δd1 and the error Δd2 are corrected. The correction coefficient used in this correction is expressed as k [p, s] using the magnetization pitch p and the state s as shown in FIG.

That is, k [p, s] is determined based on the position p of the magnetization pitch of the GMR sensor to be corrected and the state s determined by the combination of the signs a (t) and b (t). Here, the value indicated by the magnetization pitch p represents the number of periods of the output waveform of the A phase and the output waveform of the B phase. The value indicated by the state s indicates an area divided into four according to the magnitude relationship between the A-phase output and the B-phase output. Specifically, the state s has the following relationship depending on the signs of a (t) and b (t). That is,
When a (t) ≧ 0 and b (t) ≧ 0, the state s is 1.
When a (t) ≧ 0 and b (t) <0, the state s is 2,
When a (t) <0 and b (t) <0, the state s is 3,
State a is 4 when a (t) <0 and b (t) ≧ 0.

As described above, the A-phase output (a (t)) output from the first GMR sensor 184 includes the error Δd1 with respect to the ideal sine wave, and the second GMR sensor 185. The B-phase output (b (t)) output from the signal includes an error Δd2 with respect to an ideal cosine wave. When the error Δd1 related to the A phase and the error Δd2 related to the B phase are combined and expressed as an error Δd, the error Δd is expressed by the following equation (1) in consideration of the periodic characteristics of the GMR sensor 182 and the magnetic scale 188. Can be approximated.
Δd = k [p, s] × sin (π × | Lv | / Amp) (1)
Here, Lv indicates the output signal level of the GMR sensor after normalization, and Amp indicates the amplitude of the output signal of the GMR sensor after normalization.

As described above, the factors that cause the error signal Δd to be included in the output of the GMR sensor 182 include the following.
1. This is because the gap width (gap) between the magnetic scale 188 and the detection surface of the GMR sensor 182 varies depending on the detection position.
2. In relation to 1 above, it is caused by assembly tolerance when the movable part 122 is configured.
3. This is due to the detection surface of the GMR sensor 182 and the inclination of the magnetic field direction generated from the magnetic scale 188.

  The output of the GMR sensor 182 and the correction applied to the output of the GMR sensor 182 will be further described with reference to FIG. The left diagram in FIG. 8 is a diagram showing in detail the output of the A phase and the B phase after normalization. The horizontal axis represents time t, and the vertical axis represents the output of the GMR sensor 182. Also in this figure, the solid line shows the ideal case of the output waveform of the A phase output from the first GMR sensor 184, and the broken line shows the output waveform of the B phase output from the second GMR sensor 185. In the ideal case, a one-dot chain line indicates an A-phase output waveform (a (t)) output from the first GMR sensor 184, and a two-dot chain line is output from the second GMR sensor 185. An output waveform (b (t)) of the B phase is shown. As shown in this figure, the output signal of the GMR sensor 182 has the maximum error signal Δd near the half of the amplitude, and the deviation from the ideal waveform is the largest.

The right diagram in FIG. 8 is a diagram showing the relationship between the output of the GMR sensor 182 shown on the vertical axis and the correction value function f [x] shown on the horizontal axis. In this figure, the broken line indicates the correction reference function g [x], and the solid line indicates the correction value function f [x]. Here, the correction value function f [x] is expressed by the following equation (2) using the correction coefficient k [p, s] and the correction reference function g [x].
f [x] = k [p, s] × g [x] (2)

  Here, the correction coefficient k [p, s] is a solid line indicating the ideal case of the output waveform of the A phase indicated by the solid line in the left diagram of FIG. 8 and a broken line indicating the ideal case of the output waveform of the B phase. The output value of the GMR sensor 182 at the intersection of the GMR sensor 182 at the intersection with the two-dot chain line indicating the output waveform a (t) of the A phase and the alternate long and two short dashes line indicating the output waveform b (t) of the B phase. It is determined based on the difference d from the value of. That is, the correction coefficient k [p, s] is the value of the ideal case where the absolute value of the A-phase output is equal to the absolute value of the B-phase output and the A-phase output a (t). It is determined based on the difference d between the absolute value and the B-phase output b (t) when the absolute value is equal. For example, the correction coefficient k [p, s] is determined so as to increase as the difference d increases. The relationship between the difference d and the correction coefficient k [p, s] may be recorded in the nonvolatile memory 21 as a function or a table, for example.

In the present embodiment, the output of the GMR sensor 182 is corrected using a correction value obtained based on the correction value function f [x]. That is, when the output of the GMR sensor 182 before correction is α and the output of the GMR sensor 182 after correction is the corrected position information signal α ′, the corrected position information signal α ′ is expressed by the following equation (3). expressed.
α ′ = α + f [α]
= Α + (k [p, s] × g [α]) (3)

  In the present embodiment, the position of the movable portion 122 is calculated using the corrected position information signal α ′ that is the output of the GMR sensor 182 after correction.

  In this embodiment, the position calculation unit 204 sequentially uses the correction coefficient k [p, s] for the A-phase output a (t) and the B-phase output b (t) of the GMR sensor 182 to generate an error Δd. Correct. The value of the correction coefficient k [p, s] is stored in the storage unit 260 as the correction coefficient table 262 for the movable range of the movable unit 122. The value of the correction coefficient k [p, s] included in the correction coefficient table 262 is, for example, the GMR sensor output when the focus lens 12 is driven from one end to the opposite end when the power is turned on. Based on the two signal outputs of 182, it is calculated and stored for each magnetization pitch p.

  A phase output a (t) and the corrected A phase output a ′ (t) obtained by correction as described above, the B phase output b (t) and correction as described above. FIG. 9 shows the corrected B-phase output b ′ (t). In FIG. 9, the horizontal axis represents time t, and the vertical axis represents the output of the GMR sensor 182. In FIG. 9, the solid line indicates a ′ (t), the broken line indicates b ′ (t), the alternate long and short dash line indicates a (t), and the alternate long and two short dashes line indicates b (t).

  FIG. 10 shows a Lissajous waveform in which a (t) and a ′ (t) shown in FIG. 9 are plotted on the horizontal axis and b (t) and b ′ (t) are plotted on the vertical axis. In FIG. 10, the solid line indicates the relationship between a ′ (t) and b ′ (t), and the broken line indicates the relationship between a (t) and b (t). This Lissajous waveform shows a trajectory of the relationship between changes in the two signals. According to the Lissajous waveform, by assigning the output of two signals output at the same time to the horizontal axis and the vertical axis, the relationship between the amplitude and phase of the two signals can be grasped by one figure. When the two signal outputs of the GMR sensor 182 are an ideal sine wave signal and an ideal cosine wave signal, the Lissajous waveform is a perfect circle. As shown in FIG. 10, it can be seen that the relationship between a ′ (t) and b ′ (t) after correction indicated by a solid line is a perfect circle, and these are ideal waveforms. On the other hand, the relationship between a (t) and b (t) before correction indicated by a broken line is a locus in which 45 ° + 90 ° × N (N = 0, 1, 2, 3) is distorted inward from a circle, A shape close to a rhombus is shown. From this, it can be seen that a (t) and b (t) before correction include an error.

  In general, when the detection position is calculated by performing the interpolation process using the output of the two-phase encoder, the phase angle composed of the phase relationship between the A-phase output and the B-phase output is calculated. This is because the ratio between the output of the A phase and the output of the B phase is calculated, and the output of the A phase and the output of the B phase are calculated by calculating an arctangent function for the calculated ratio value. The phase angle formed by is calculated. This phase angle can be illustrated by the phase angle based on the relationship between the point on the locus of the Lissajous waveform as shown in FIG. 10 and the origin position of the Lissajous waveform. As described above, when the Lissajous waveform shows a shape close to a rhombus, the arc tangent calculation using the output of the GMR sensor is an arc tangent calculation using an ideal sine wave signal and an ideal cosine wave signal. An error Δd occurs for the result. The magnitude of the error Δd changes periodically, and this changing period is a period related to a quarter period of the magnetization pitch. As a result, a periodic error corresponding to ¼ period of the magnetization pitch occurs in calculating the lens position in the optical axis direction.

  Let us consider a case where the error Δd has a quarter period of the magnetization pitch, and this error remains as it is without a mechanism for reducing the error as in the present embodiment. At this time, the position detected based on the phase angle calculated by the position calculation unit 204 also generates an error of ¼ period of the magnetization pitch. When the operation of the movable portion 122 is controlled using this position detection result, the control position deviation, which is the deviation between the target position and the detection position in the feedback control, also periodically changes in magnitude and becomes 1 / magnetization pitch. There is a periodic error related to the four periods. Due to the change in the control position deviation of 1/4 period of the magnetization pitch, a change in which the operation amount, which is the drive amount to the movable portion 122, is increased or decreased in feedback control occurs. As a result, a driving sound having a frequency corresponding to a quarter period of the magnetization pitch and the driving speed of the focus lens is generated from the movable portion 122 of the focus lens 12.

The frequency of the extra driving sound at the time of driving the movable part 122 caused by this error is generated based on the relationship based on the following equation (4).
Driving sound frequency (Hz) caused by distortion
= Focus lens driving speed (mm / s) / (magnetization pitch (mm) / 4) (4)

  For example, when the constant speed moving speed of the focus lens 12 is 50 mm / s and the magnetization pitch is 250 μm, the frequency of the driving sound is 800 Hz. 800 Hz is a frequency that is sensitive to human hearing. When such a sound is recorded in, for example, moving image shooting, it becomes difficult to hear.

  Next, operations related to position control according to the present embodiment will be described. FIG. 11 is a flowchart showing the position control operation. The position control operation starts when the camera system 1 is activated.

  In step S101, the lens control unit 19 sets an initial value of the correction coefficient k [p, s]. Note that the initial value of the correction coefficient k [p, s] may be, for example, 0, a value determined at the previous operation, or another value. In step S102, the lens control unit 19 sets a correction flag indicating whether or not to perform correction to OFF.

  In step S <b> 103, the lens control unit 19 performs current position calculation processing for calculating the position of the movable unit 122 including the focus lens 12 in the optical axis direction based on the output signal of the GMR sensor 182. The current position calculation process will be described with reference to the flowchart shown in FIG.

  In step S <b> 201, the lens control unit 19 acquires the normalized A-phase output a (t) and B-phase output b (t) of the GMR sensor 182.

  In step S202, the lens control unit 19 determines whether or not the correction flag is ON. When the correction flag is not ON, that is, when the correction flag is OFF, the process proceeds to step S204. On the other hand, when the correction flag is ON, the process proceeds to step S203. In step S203, the lens control unit 19 performs output correction processing. The output correction process will be described later. After the output correction process, the process proceeds to step S204.

  In the current position calculation process in step S103 described here, the output correction process is not performed because the correction flag is OFF.

In step S204, the lens control unit 19 performs an arctangent calculation based on a (t) and b (t) acquired in step S201. That is, the phase angle θ is calculated based on the following formula (5).
θ = arctan (a (t) / b (t)) (5)

  In step S205, the lens control unit 19 calculates a relative position within the magnetization pitch by multiplying the calculated phase angle θ by a predetermined relative position conversion factor within the pitch. In step S206, the lens control unit 19 adds an offset amount (magnetization pitch count offset addition amount 266) corresponding to the value of the magnetization pitch p to the relative position within the magnetization pitch obtained in step S205, and the light. The current position of the movable part 122 in the axial direction is calculated. Thus, the current position calculation process ends. Thereafter, the process returns to step S103.

  Returning to FIG. 11, the description will be continued. After the current position calculation process in step S103, the process proceeds to step S104. In step S104, the lens control unit 19 sets the feedback control state flag to ON. Here, the feedback control state flag is a flag indicating whether feedback control is being performed. In step S105, the lens control unit 19 performs a position holding operation. The position holding operation is an operation for keeping the position of the movable portion 122 at the current position. By this processing, the position of the movable part 122 remains at the current position.

  In step S <b> 106, the lens control unit 19 determines whether there is an operation command that is a command for moving the movable unit 122. When there is no operation command, the process repeats step S106 and waits. When there is an operation command, the process proceeds to step S107.

  In step S107, the selected operation mode is determined. When the selected operation mode is an adjustment operation for determining the correction coefficient k [p, s], the process proceeds to step S108. In the present embodiment, the adjustment operation is first performed when the camera system 1 is activated. Therefore, the adjustment operation is selected when the determination of step S107 is performed for the first time, and the adjustment operation is not selected when the determination of step S107 is performed for the second time and thereafter.

  In step S108, the lens control unit 19 performs an adjustment operation to calculate a correction coefficient. A movement path of the movable part 122 including the focus lens 12 in the adjustment operation will be described with reference to a schematic diagram shown in FIG. First, it is assumed that the movable part 122 is at a position A shown in FIG. At this time, in the adjustment operation, the movable portion 122 is moved to the position B at the end on the camera body 30 side. Subsequently, the movable part 122 is moved to the position C on the end opposite to the camera body 30. Based on the output of the GMR sensor 182 while moving from the position B to the position C, the correction coefficient k [p, s] is determined.

  The adjustment operation process will be described with reference to the flowchart shown in FIG. In step S <b> 301, the lens control unit 19 sets the end on the camera body 30 side as the movement target position of the movable unit 122.

  In step S302, the lens control unit 19 performs a movement control operation. The movement control operation is an operation for moving the movable portion 122 to the instructed movement target position. The movement control operation will be described with reference to the flowchart shown in FIG.

  In step S401, the target position instruction unit 201 of the lens control unit 19 is a target position for each processing cycle during the movement based on the current position of the movable unit 122 and the movement target position (position B in FIG. 13). A certain control target position is calculated. FIG. 16 shows the relationship among the initial position, the movement target position, and the control target position. In FIG. 16, the horizontal axis is time t, and the vertical axis is the position of the movable portion 122. In the movement control operation, the control target position Dn (n = 1, 2, 3,..., N) is set so that the movable part 122 is moved at a constant speed.

  In step S402, the lens control unit 19 performs a feedback control process. The feedback control process is a process of driving the movable unit 122 according to the difference between the current position and the control target position for each process, that is, by feedback control. The feedback control process will be described with reference to FIG.

  In step S501, the lens control unit 19 sets a control target position in the process being executed according to the elapsed time based on the control target position calculated in step S401. In step S <b> 502, the lens control unit 19 performs a current position calculation process, and calculates the current position of the movable unit 122 using the output signal of the GMR sensor 182. The current position calculation process is the process described with reference to FIG. That is, it is simply as follows.

  In step S201, the lens control unit 19 obtains an A-phase output a (t) and a B-phase output b (t). In step S202, the lens control unit 19 determines whether or not the correction flag is ON. Since the correction flag is OFF at this time, the process proceeds to step S204. In step S204, the lens control unit 19 calculates the phase angle θ based on a (t) and b (t). In step S205, the lens control unit 19 calculates the relative position within the magnetization pitch based on the phase angle θ. In S206, the offset amount is added to the relative position within the magnetization pitch to calculate the current position of the movable unit 122 in the optical axis direction. Thereafter, the process returns to the feedback control process described with reference to FIG.

  In the feedback control process, after the current position is calculated in step S502, the process proceeds to step S503. In step S503, the calculation unit 202 of the lens control unit 19 calculates a control position deviation from the difference between the control target position set in step S501 and the current position acquired in step S502. In step S <b> 504, the lens control unit 19 calculates an operation amount of the movable unit 122 based on the control position deviation, and outputs the calculated operation amount to the focus lens driver 15. As a result, the movable part 122 moves.

  In step S505, the lens control unit 19 determines whether or not the in-adjustment flag is ON. When the adjustment in progress flag is not ON, the feedback control process ends. On the other hand, when the in-adjustment flag is ON, the process proceeds to step S506. In step S506, the lens control unit 19 performs a correction coefficient calculation process. After the correction coefficient calculation process, the feedback control process ends.

  Here, since the adjustment-in-progress flag is OFF, the correction coefficient calculation process in step S506 is not performed, and the process returns to step S402 of the movement control operation described with reference to FIG. Returning to FIG. 15, the description of the movement control operation will be continued. After the feedback control process in step S402, the process proceeds to step S403.

  In step S403, the lens control unit 19 determines whether or not the movement target position set in step S301 has been reached. When the movement target position has not been reached, the process returns to step S401. That is, the feedback control process is repeated until the movement target position is reached, and the movable unit 122 gradually moves toward the movement target position. When it is determined in step S403 that the movement target position has been reached, the movement control operation ends, and the process returns to step S302 of the adjustment operation described with reference to FIG. That is, when the movable part 122 reaches the end (position B shown in FIG. 13) on the camera body 30 side, the movement control operation ends.

  Returning to FIG. 14, the description of the adjustment operation will be continued. After the movement control operation in step S302, the process proceeds to step S303. In step S303, the lens control unit 19 sets the adjusting flag to ON. Further, the lens control unit 19 sets a variable p representing the magnetization pitch number to 1. In step S304, the lens control unit 19 sets an end (position C shown in FIG. 13) opposite to the camera body 30 side as a movement target position.

  In step S305, the lens control unit 19 performs a movement control operation. The movement control operation is the operation described with reference to FIG. That is, it will be briefly described as follows. In step S401, the target position instruction unit 201 of the lens control unit 19 is a target position for each processing cycle during movement based on the current position of the movable unit 122 and the movement target position (position C in FIG. 13). A certain control target position is calculated.

  In step S402, the lens control unit 19 performs a feedback control process. The feedback control process is the process described with reference to FIG. That is, it will be briefly described as follows. In step S501, the lens control unit 19 sets a control target position in the process being executed. In step S <b> 502, the lens control unit 19 performs a current position calculation process, and calculates the current position of the movable unit 122 using the output signal of the GMR sensor 182. The current position calculation process is the process described with reference to FIG.

  In step S503, the lens control unit 19 calculates a control position deviation from the difference between the control target position and the current position. In step S504, the lens control unit 19 calculates an operation amount based on the control position deviation. Output to the driver 15. As a result, the movable part 122 moves. In step S505, the lens control unit 19 determines whether or not the in-adjustment flag is ON. Here, since the in-adjustment flag is ON, the process proceeds to step S506.

  In step S506, the lens control unit 19 performs a correction coefficient calculation process. That is, the correction coefficient calculation process is repeatedly executed while the movable unit 122 moves from the end on the camera body 30 side (position B in FIG. 13) to the opposite end (position C in FIG. 13). The correction coefficient calculation process is a process for determining the correction coefficient k [p, s]. The correction coefficient calculation process will be described with reference to the flowchart shown in FIG.

  In the correction coefficient calculation process, the absolute values of the A phase output a (t) and the B phase output b (t) of the GMR sensor 182 are used. A point where the absolute value of the A phase output a (t) and the absolute value of the B phase output b (t) are equal is called an intersection. Since one magnetization pitch of the magnetic scale 188 is one period of the output signal of the GMR sensor 182, there are four intersections in one magnetization pitch. The correction coefficient k [p, s] is determined based on the absolute value of the output of the GMR sensor 182 at the intersection.

  In step S <b> 601, the lens control unit 19 acquires the A-phase output a (t) and the B-phase output b (t) of the GMR sensor 182. In step S602, the lens control unit 19 determines whether or not the absolute value of a (t) is equal to the absolute value of b (t). If the absolute value of a (t) is not equal to the absolute value of b (t), the process proceeds to step S610. On the other hand, when the absolute value of a (t) is equal to the absolute value of b (t), the process proceeds to step S603.

  In step S603, the lens control unit 19 determines whether a (t) is 0 or more and b (t) is 0 or more. When a (t) is 0 or more and b (t) is 0 or more, the process proceeds to step S604. In step S604, the lens control unit 19 sets the variable E (p, 1) to the absolute value of a (t). That is, the absolute value of a (t) when the state s is 1 and the absolute value of a (t) is equal to the absolute value of b (t) is set to the variable E (p, 1). Thereafter, the process proceeds to step S610.

  When it is determined in step S603 that a (t) is not less than 0 and b (t) is not not less than 0, the process proceeds to step S605. In step S605, the lens control unit 19 determines whether a (t) is 0 or more and b (t) is less than 0. When a (t) is 0 or more and b (t) is less than 0, the process proceeds to step S606. In step S606, the lens control unit 19 sets the variable E (p, 2) to the absolute value of a (t). That is, the absolute value of a (t) when the state s is 2 and the absolute value of a (t) is equal to the absolute value of b (t) is set in the variable E (p, 2). Thereafter, the process proceeds to step S610.

  If it is determined in step S605 that a (t) is not less than 0 and b (t) is not less than 0, the process proceeds to step S607. In step S607, the lens control unit 19 determines whether a (t) is less than 0 and b (t) is less than 0. When a (t) is less than 0 and b (t) is less than 0, the process proceeds to step S608. In step S608, the lens control unit 19 sets the variable E (p, 3) to the absolute value of a (t). That is, the absolute value of a (t) when the state s is 3 and the absolute value of a (t) is equal to the absolute value of b (t) is set to the variable E (p, 3). Thereafter, the process proceeds to step S610.

  If it is determined in step S607 that a (t) is less than 0 and b (t) is not less than 0, the process proceeds to step S609. In step S609, the lens control unit 19 sets the variable E (p, 4) to the absolute value of a (t). That is, the absolute value of a (t) when the state s is 4 and the absolute value of a (t) is equal to the absolute value of b (t) is set in the variable E (p, 4). Thereafter, the process proceeds to step S610.

  In step S610, the lens control unit 19 determines whether the magnetization pitch has changed. When the magnetization pitch has not changed, the process proceeds to step S612. On the other hand, when the magnetization pitch is changing, the process proceeds to step S611. In step S611, the lens control unit 19 adds 1 to the variable p. Thereafter, processing proceeds to step S612.

  In step S612, the lens control unit 19 determines whether or not the movable unit 122 has reached the end opposite to the camera body 30 (position C in FIG. 13). When the movable part 122 has not reached the end, the correction coefficient calculation process ends. On the other hand, when the movable part 122 has reached the end, the process proceeds to step S613.

In step S613, the lens control unit 19 calculates a correction coefficient k [p, s]. A method for calculating the correction coefficient k [p, s] will be described below. Since the A-phase output a (t) and the B-phase output b (t) are ideally sine waves whose phases are shifted by 90 degrees, the A-phase output a (t) and the B-phase output The value Lid of the ideal A-phase output a (t) and B-phase output b (t) at the intersection with b (t) is expressed by the following equation using the amplitude Amp of a (t) or b (t): It is represented by (6).
Lid = Amp × sin45 ° (6)

However, as described above, the output signal of the GMR sensor 182 deviates from an ideal sine wave signal, and the actual level of the intersection is smaller than the ideal value. Therefore, for the four intersections in one cycle of the absolute value of a (t) (| a (t) |) and the absolute value of b (t) (| b (t) |), Based on the above, the correction coefficient k [p, s] is obtained using the correction reference function g [x] (x is a (t) or b (t)).
k [p, s] = (Lid−Lint) / g [Lid] (7)
Here, Lid is the ideal intersection level, Lint is the intersection level of a (t) and b (t) in the state s of the p-th magnetization pitch, p is the pitch number, and s is a ( It is a state determined by a combination of signs of t) and b (t). That is, the above formula (7) is as follows.
k [p, 1] = (Amp × sin (π / 4) −E (p, 1))
/ G [(Amp × sin (π / 4))]
k [p, 2] = (Amp × sin (π / 4) −E (p, 2))
/ G [(Amp × sin (π / 4))]
k [p, 3] = (Amp × sin (π / 4) −E (p, 3))
/ G [(Amp × sin (π / 4))]
k [p, 4] = (Amp × sin (π / 4) −E (p, 4))
/ G [(Amp × sin (π / 4))]

  Here, the correction reference function g [x] will be described. In the present embodiment, a function that gives a correction amount corresponding to a (t) or b (t) is determined in advance as the correction reference function. For example, as shown in FIG. 8, the correction reference function g [x] is a function such that the value becomes 0 at the maximum value and the minimum value of the output of the GMR sensor 182 that fluctuates and the midpoint thereof.

The correction reference function g [x] is included in the error signal Δd shown in the above equation (1) and is expressed by the following equation (8).
g [x] = sin (π × | Lv | / Amp)
= Sin (π × | x | / Amp) (8)
Here, Lv indicates the output signal level of the GMR sensor after normalization, and Amp indicates the amplitude of the output signal of the GMR sensor after normalization.

  In step S614, the lens control unit 19 stores the correction coefficient k [p, s] calculated in step S613 in the storage unit 260 as a correction coefficient table. In step S615, the lens control unit 19 sets the correction flag to ON. Thereafter, the correction coefficient calculation process ends, and the process returns to step S506 of the feedback control process described with reference to FIG.

  After the correction coefficient calculation process in step S506, the feedback control process ends, and the process returns to step S402 of the movement control operation described with reference to FIG. After the feedback control process in step S402, the process proceeds to step S403. In step S403, the lens control unit 19 determines whether or not the target position has been reached. When the movement target position has not been reached, the feedback control process is repeated. When the movement target position has been reached, the movement control operation ends, and the process is step S305 of the adjustment operation described with reference to FIG. Return to. That is, when the movable part 122 reaches the end opposite to the camera body 30 side (position C shown in FIG. 13), the movement control operation ends. In this way, the correction coefficient k [p, s] is determined for the entire movable range of the movable portion 122.

  After the movement control operation, the process proceeds to step S306. In step S306, the lens control unit 19 sets the adjusting flag to OFF. Thereafter, the adjustment operation ends, and the process returns to step S108 described with reference to FIG. After the adjustment operation, the process proceeds to step S109. In step S109, the lens control unit 19 performs a control end operation, and ends the feedback control. Thereafter, the process returns to step S104.

  If it is determined in step S107 that the selected operation is a normal operation, the process proceeds to step S110. The normal operation is an operation of moving the movable unit 122 including the focus lens 12 from the current position to another position. For example, when the AF operation is performed based on the processing result of the AF processing unit 34 of the camera body 30, the normal operation is selected.

  In step S <b> 110, the lens control unit 19 sets a movement target position that is a target position for moving the movable unit 122 based on information input via the lens control communication interface 205 and the operation input interface 206. . In step S111, the lens control unit 19 performs the movement control operation described with reference to FIG. That is, it will be briefly described as follows.

  In step S401, the target position instruction unit 201 of the lens control unit 19 is a target position for each processing cycle during movement based on the current position of the movable unit 122 and the movement target position set in step S110. A control target position is calculated. For example, as shown in FIG. 19, consider a case where the movable unit 122 located at the initial position D is moved to the movement target position E. The control target position set at this time is schematically shown in FIG. In FIG. 20, the horizontal axis is time t, and the vertical axis is the position of the movable portion 122. In the movement control operation, the control target position Dn (n = 1, 2, 3,..., N) is set so that the movable part 122 is moved at a constant speed.

  In step S402, the lens control unit 19 performs a feedback control process. The feedback control process is the process described with reference to FIG. That is, it will be briefly described as follows. In step S501, the lens control unit 19 sets a control target position in the process being executed. In step S <b> 502, the lens control unit 19 performs a current position calculation process, and calculates the current position of the movable unit 122 using the output signal of the GMR sensor 182. The current position calculation process is the process described with reference to FIG. That is, it is as follows.

  In step S201, the lens control unit 19 obtains an A-phase output a (t) and a B-phase output b (t). In step S202, the lens control unit 19 determines whether or not the correction flag is ON. Since the correction flag is ON at this time, the process proceeds to step S203.

  In step S203, the lens control unit 19 performs output correction processing. The output correction process corrects the A-phase output a (t) and the B-phase output b (t) of the GMR sensor 182 based on the correction reference function g [x] and the correction coefficient k [p, s]. It is processing. The corrected phase A output is a ′ (t), and the corrected phase B output is b ′ (t). The output correction process will be described with reference to the flowchart shown in FIG.

  In step S701, the lens control unit 19 determines whether a (t) is 0 or more. When a (t) is 0 or more, the process proceeds to step S702.

In step S702, the lens control unit 19 determines whether b (t) is 0 or more. When b (t) is 0 or more, the process proceeds to step S703. That is, the process of step S703 is performed when the state s is 1. In step S703, the lens control unit 19 corrects a (t) and b (t) using the following correction equations (9) and (10).
a ′ (t) = a (t) + k [p, s] × g [a (t)] (9)
b ′ (t) = b (t) + k [p, s] × g [b (t)] (10)

  Thereafter, the output correction process ends, and the process returns to step S203 of the current position calculation process described with reference to FIG.

When it is determined in step S702 that b (t) is not 0 or more, the process proceeds to step S704. That is, the process of step S704 is performed when the state s is 2. In step S704, the lens control unit 19 corrects a (t) and b (t) using the following correction equations (11) and (12).
a ′ (t) = a (t) + k [p, s] × g [a (t)] (11)
b ′ (t) = b (t) −k [p, s] × g [b (t)] (12)

  Thereafter, the output correction process ends, and the process returns to step S203 of the current position calculation process described with reference to FIG.

When it is determined in step S701 that a (t) is not 0 or more, the process proceeds to step S705. In step S705, the lens control unit 19 determines whether b (t) is 0 or more. When b (t) is 0 or more, the process proceeds to step S706. That is, the process of step S706 is performed when the state s is 4. In step S706, the lens control unit 19 corrects a (t) and b (t) using the following correction equations (13) and (14).
a ′ (t) = a (t) −k [p, s] × g [a (t)] (13)
b ′ (t) = b (t) + k [p, s] × g [b (t)] (14)

  Thereafter, the output correction process ends, and the process returns to step S203 of the current position calculation process described with reference to FIG.

When it is determined in step S705 that b (t) is not 0 or more, the process proceeds to step S707. That is, the process of step S707 is performed when the state s is 3. In step S707, the lens control unit 19 corrects a (t) and b (t) using the following correction equations (15) and (16).
a ′ (t) = a (t) −k [p, s] × g [a (t)] (15)
b ′ (t) = b (t) −k [p, s] × g [b (t)] (16)

  Thereafter, the output correction process ends, and the process returns to step S203 of the current position calculation process described with reference to FIG.

  By the output correction process as described above, a corrected A-phase output a ′ (t) and a corrected B-phase output b ′ (t), which are corrected position information signals, are obtained. The output correction process is schematically shown in FIG.

  FIG. 22A shows the numbers of the magnetization pitch p and the state s. FIG. 22B shows the output of the GMR sensor 182. Here, the solid line shows an ideal case of the output waveform of the A phase output from the first GMR sensor 184, and shows a sine wave shape. A broken line indicates an ideal case of the output waveform of the B phase output from the second GMR sensor 185, and indicates a cosine wave shape. The alternate long and short dash line indicates the A phase output a (t) output from the first GMR sensor 184. A two-dot chain line indicates a B-phase output b (t) output from the second GMR sensor 185.

  (C) of FIG. 22 schematically shows an absolute value of a value obtained by multiplying the correction reference function g [x] by the correction coefficient k [p, s]. FIG. 22D shows whether | k [p, s] × g [a (t)] | is added to or subtracted from the output a (t) of the A phase. As shown in (d) of FIG. 22, whether to add or subtract | k [p, s] × g [a (t)] | is determined by the state.

  FIG. 22E shows the output of the GMR sensor 182 before and after correction. Here, the solid line indicates the corrected A-phase output a ′ (t), the broken line indicates the corrected B-phase output b ′ (t), and the alternate long and short dash line indicates the first GMR before correction. The A-phase output waveform a (t) output from the sensor 184 is shown, and the two-dot chain line shows the B-phase output waveform b (t) output from the second GMR sensor 185.

  As is apparent from FIGS. 22B and 22E, the corrected output of the GMR sensor 182 is close to the ideal output of the GMR sensor 182.

Returning to FIG. 12, the description of the current position calculation process will be continued. After the output correction process in step S203, the process proceeds to step S204. In step S204, the lens control unit 19 uses the following equation (17) based on a ′ (t) and b ′ (t), which are outputs of the GMR sensor 182 corrected by the output correction process in step S203. The phase angle θ is calculated.
θ = arctan (a ′ (t) / b ′ (t)) (17)

  In step S205, the lens control unit 19 multiplies the phase angle θ by a predetermined relative position conversion factor within the pitch, and calculates the relative position within the magnetization pitch. In step S206, the lens control unit 19 adds the offset amount to the relative position in the magnetization pitch obtained in step S205, and calculates the current position of the movable unit 122 in the optical axis direction. Thereafter, the process returns to step S502 of the feedback control process described with reference to FIG.

  After the current position calculation process in step S502, the process proceeds to step S503. In step S503, the lens control unit 19 calculates a control position deviation from the difference between the control target position and the current position. In step S504, the lens control unit 19 calculates an operation amount based on the control position deviation. Output to the driver 15. As a result, the movable part 122 moves.

  In step S505, the lens control unit 19 determines whether or not the in-adjustment flag is ON. Here, since the in-adjustment flag is OFF, the feedback control process ends, and the process returns to step S402 of the movement control operation described with reference to FIG.

  Returning to FIG. 15, the description of the movement control operation will be continued. After the feedback control process in step S402, the process proceeds to step S403. In step S403, the lens control unit 19 determines whether or not the movement target position set in step S110 of the apparatus operation described with reference to FIG. 11 has been reached. When the movement target position has not been reached, the process returns to step S401. That is, the feedback control process is repeated until the movement target position is reached. When it is determined in step S403 that the movement target position has been reached, the movement control operation ends, and the process returns to step S111 of the apparatus operation described with reference to FIG.

  Returning to FIG. 11, the description of the position control operation will be continued. After the movement control operation in step S111, the process proceeds to step S109. In step S109, the lens control unit 19 performs a control end operation, and ends the feedback control. Thereafter, the process returns to step S104.

  If it is determined in step S107 that the selected operation is a control end operation, the process proceeds to step S112. In step S112, the lens control unit 19 performs a control end operation, and ends the feedback control. Thereafter, the process proceeds to step S113. In step S113, the lens control unit 19 sets the feedback control state flag to OFF. Thereafter, the movement control operation ends.

  FIG. 23 shows a Lissajous waveform created based on the output of the GMR sensor 182 before and after correction. Here, the solid line is a Lissajous waveform created using the A-phase output and the B-phase output of the GMR sensor 182 after correction, and the broken line is the A-phase output and B-phase of the GMR sensor 182 after correction. It is a Lissajous waveform created using the output. It is clear that the Lissajous waveform after correction has a shape closer to a perfect circle than the Lissajous waveform before correction.

  Further, FIG. 24 shows frequency characteristics of driving sound generated when the focus lens 12 is driven at a constant speed using the output of the GMR sensor 182 before and after correction. In FIG. 24, the solid line shows the result of FFT analysis of the driving sound generated when the focus lens 12 is driven at a constant speed using the output of the GMR sensor 182 after correction, and the broken line shows the GMR before correction. The result of FFT analysis of the driving sound generated when the focus lens 12 is driven at a constant speed using the output of the sensor 182 is shown. As is apparent from FIG. 24, it can be seen that the drive sound generated after the correction is lower than that before the correction at about 800 Hz indicating the peak.

  When the correction as described above is not performed, when the movable unit 122 is driven at a constant speed, the speed of the movable unit 122 is set to a period due to a periodic error existing in the output of the GMR sensor 182. And a relatively loud driving sound can be generated. On the other hand, according to the present embodiment, since the output of the GMR sensor 182 approaches an ideal case by correction, the speed of the movable part 122 approaches a constant speed, and the drive sound that can be generated is reduced.

  In addition, since the driving speed of the movable part is maintained at a value closer to the designated driving speed, the autofocus accuracy is also improved. Furthermore, the power consumption is reduced by reducing the change in the amount of extra operation.

  In the present embodiment, a common correction coefficient k [p, s] is used in each state s, and based on the above formulas (9) to (16) using a predetermined correction reference function g [x]. A corrected position information signal is calculated. As described above, since the amount of calculation is small in the correction according to the present embodiment, according to the present embodiment, appropriate correction can be performed simply and with a small amount of data processing.

  In the above-described embodiment, the correction coefficient k [p, s] is described as a configuration that is determined at the time of activation. However, the present invention is not limited to this. In the inspection of the lens barrel 10 before shipment, the correction coefficient k [p, s] is obtained and stored in the nonvolatile memory 21, and the correction coefficient k [p, s] is not obtained at startup. It is good. In this way, the processing amount in the lens control unit 19 is reduced compared to the case of the present embodiment.

  In consideration of the aging of the magnetic scale 188 and the like, a configuration may be used in which the peak level and intersection level of the output of the GMR sensor 182 are stored during actual use, and the correction coefficient is constantly updated. In this way, the position calculation system is improved as compared with the case of the present embodiment.

  Further, in the present embodiment, the point where the absolute value is equal to the output of the A phase and the output of the B phase is used in order to obtain the correction coefficient k [p, s]. A point where the values of the output and the B-phase output are equal may be used. In this case, the correction coefficient k [p, s] is determined so that the correction coefficient k [p, s] differs depending on the signs of a (t) and b (t).

  In this embodiment, the correction coefficient k [p, s] is obtained for each magnetization pitch p and for each state s. However, although the correction coefficient k [p, s] is obtained for each state s, all the magnetizations are obtained. A correction coefficient k [p, s] common to the pitch p may be used. In this way, the processing amount according to the present embodiment is reduced.

  In the above description, the case where the Lissajous waveform related to the GMR sensor 182 is distorted so as to be recessed inward with respect to the circle has been described as an example. However, the present invention is not limited to this, and the same correction can be applied to a case where 45 ° + 90 ° × N (N = 0, 1, 2, 3) of the Lissajous waveform is distorted so as to bulge outward.

  In the present embodiment, the correction reference function g [x] is a function such that the value of g [x] becomes 0 at the maximum value and minimum value of the output of the fluctuating GMR sensor 182 and the middle point thereof. However, it is not limited to this.

  In the present embodiment, Expression (8) is shown as an example of the correction reference function g [x], but is not limited thereto. Moreover, although the formula (7) is shown as an example of the correction coefficient k [p, s], it is not limited to this. The correction coefficient k [p, s] may use another relationship as long as an ideal intersection and an intersection of a (t) and b (t) are used.

In the present embodiment, Expression (2) is shown as an example of the correction value function, but the present invention is not limited to this. For example, as in the following formulas (18) and (19), a product of a correction coefficient k [p, s] and a correction reference function g [x] plus C that is a predetermined offset value constant, Alternatively, the correction value function may be determined by adding an offset value to a value C [p, s] that is individually determined by the magnetization pitch p and the state s. These offset values can also be used when, for example, the sensor output changes in offset depending on the temperature condition of the sensor.
f [x] = k [p, s] × g [x] + C (18)
f [x] = k [p, s] × g [x] + C [p, s] (19)

  In this embodiment, a magnetic encoder is used as the position sensor, but the type of encoder is not limited to this. For example, an optical encoder or a capacitive encoder may be used for the driving device. In this embodiment, a linear scale is used as the magnetic scale 188, but the present invention is not limited to this. For example, an annular magnetic scale may be used as the position sensor 18 that detects rotation.

  In this embodiment, a two-phase encoder has been described as an example, but the present invention is not limited to this. For example, the technology according to the present embodiment can be similarly applied to encoders of three phases or more.

  In the present embodiment, the operation has been described assuming that the position calculation unit calculates the position of the focus lens. However, the present invention is not limited to this. For example, the technique of the present embodiment can be applied to the movement of the zoom lens. The technique of the present embodiment can also be applied to position detection when moving an object other than a lens.

  DESCRIPTION OF SYMBOLS 1 ... Camera system, 10 ... Lens barrel, 11 ... Fixed member, 12 ... Focus lens, 13 ... Zoom lens, 14 ... Aperture, 15 ... Focus lens driver, 16 ... Zoom lens driver, 17 ... Aperture driver, 18 ... Position Sensor, 19 ... Lens control unit, 20 ... Lens operation unit, 21 ... Non-volatile memory, 22 ... Lens side interface, 30 ... Camera body, 31 ... Image sensor, 32 ... Imaging circuit, 33 ... AE processing unit, 34 ... AF Processing unit 35 ... Image calculation unit 36 ... Image processing circuit 37 ... LCD driver 38 38 Liquid crystal display 39 39 Input unit 40 Control unit 41 Power source 42 Non-volatile memory 43 Internal memory 44 ... Compression / expansion unit, 45 ... Removable memory, 46 ... Body-side interface, 47 ... Bus line, 122 ... Moving part, 123 ... Drive ,... 124, movable coil, 126, stator, 182, GMR sensor, 184, first GMR sensor, 185, second GMR sensor, 188, magnetic scale, 189, amplification circuit, 201, target position indicating unit, 202 ... Calculation unit 203 ... Operation amount calculation unit 204 ... Position calculation unit 205 ... Lens control communication interface 206 ... Operation input interface 207 ... Memory interface 210 ... Focus lens control unit 242 ... A / D conversion unit 243 ... Correction coefficient determination unit, 244 ... First normalization correction unit, 246 ... Second normalization correction unit, 251 ... Correction unit, 252 ... First error correction unit, 254 ... Second error correction unit 256: Phase angle calculation unit, 258 ... Calculation position output unit, 260 ... Recording unit, 262 ... Correction coefficient table, 264 ... Phase angle calculation table, 66 ... magnetization pitch count offset addition amount.

Claims (9)

A scale unit and a detection unit disposed opposite to the scale unit, and the first position information signal and the first unit according to a relative movement amount between the scale unit and the detection unit . A position acquisition unit that generates a two-phase periodic position information signal consisting of the position information signal of the second position information signal and a second position information signal whose phase is shifted by 90 ° ;
The value of the normalized position information signal when the absolute values of the normalized position information signals obtained by normalizing the amplitudes of the measured position information signals to a predetermined amplitude are equal to each other , and the ideal normalization of each A correction coefficient determination unit that determines a correction coefficient based on a difference from the value of the normalized position information signal when the absolute values of the position information signal are equal to each other;
A correction value determination unit that calculates a correction value based on a correction value function obtained by multiplying a correction reference function prepared in advance having a signal period equal to the signal period of the position information signal by the correction coefficient ;
A position detection apparatus comprising: a correction unit that calculates a corrected position information signal obtained by correcting the position information signal by adding or subtracting the correction value to or from each of the position information signals. A scale unit and a detection unit disposed opposite to the scale unit, and the first position information signal and the first unit according to a relative movement amount between the scale unit and the detection unit . A position acquisition unit that generates a two-phase periodic position information signal consisting of the position information signal of the second position information signal and a second position information signal whose phase is shifted by 90 ° ;
The value of the normalized position information signal when the absolute values of the normalized position information signals obtained by normalizing the amplitudes of the measured position information signals to a predetermined amplitude are equal to each other , and the ideal normalization of each A correction coefficient determination unit that determines a correction coefficient and an offset correction coefficient based on a difference from the value of the normalized position information signal when the absolute values of the position information signal are equal to each other;
A correction value is calculated based on a correction value function obtained by adding the offset correction coefficient to a value obtained by multiplying a correction reference function having a signal period equal to the signal period of the position information signal by the correction coefficient. A correction value determination unit to perform,
A position detection apparatus comprising: a correction unit that calculates a corrected position information signal obtained by correcting the position information signal by adding or subtracting the correction value to or from each of the position information signals. The correction coefficient determination unit determines the correction coefficient every quarter period of the signal period,
The correction unit calculates the post-correction position information signal using the correction coefficient that is common within a quarter of the signal period.
The position detection device according to claim 1 or 2 . The correction coefficient determining unit determines the correction coefficient in a predetermined phase;
The correction unit calculates the corrected position information signal by repeatedly using the common correction coefficient corresponding to the predetermined phase for each signal period.
The position detection device according to any one of claims 1 to 3 . A non-volatile memory;
The correction coefficient determination unit records the correction coefficient in the nonvolatile memory,
The correction unit reads the correction coefficient recorded in the nonvolatile memory, and calculates the corrected position information signal using the read correction coefficient;
The position detection device according to any one of claims 1 to 4 . The position detection device according to claim 5 , wherein the correction coefficient determination unit determines the correction coefficient every time the position detection device is activated, and records the determined correction coefficient in the nonvolatile memory. The position detection device according to claim 5 , wherein the correction coefficient determination unit determines the correction coefficient before shipment of the position detection device, and records the determined correction coefficient in the nonvolatile memory. The correction coefficient determination unit repeatedly determines the correction coefficient during operation of the position detection device and updates the correction coefficient,
The correction unit calculates the corrected position information signal using the updated correction coefficient.
The position detection device according to claim 5 . A drive unit having a fixed member and a movable unit that moves relative to the fixed member;
The position detection device according to any one of claims 1 to 8 ,
A control unit and
One of the scale part and the detection part is fixed to the fixed member, and the other is fixed to the movable part,
The position acquisition unit generates the position information signal according to a relative movement amount between the fixed member and the movable unit,
The control unit controls the operation of the driving unit based on the corrected position information signal output by the position detection device.
Drive device.

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