JP2017044972A - Optical equipment, and its control method and control program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably perform offset cancellation regardless of a usage condition when detecting a position of an AF lens.SOLUTION: When imaging a subject, a camera drives an imaging optical system 12 along an optical axis to allow the imaging optical system to focus at the subject. The position of the imaging optical system is detected by using magnetic sensors 19a and 19b to obtain detection position information. CPU 111 sets sensitivities of the magnetic sensors, and on the basis of detection position information being obtained by using magnetic sensors in which sensitivities are set to prescribed low sensitivity, corrects detection position information being obtained by using magnetic sensors in which sensitivities are set to high sensitivities higher than the prescribed low sensitivity.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical instrument, a control method thereof, and a control program.

  In general, in an imaging apparatus such as a digital still camera or a video camera, an imaging apparatus that detects the position of a photographing lens such as a focus lens and drives and controls the photographing lens according to the lens position is known (Patent Document 1). See).

  Then, in the imaging device described in Patent Document 1, when a sensitivity increase condition such as the completion of the focusing operation is satisfied, the constant current supplied to the Hall element is increased to increase the sensitivity of the Hall element. ing.

JP 2009-47757 A

  In the imaging apparatus described in Patent Document 1 described above, when the Hall element is switched to high sensitivity, it is necessary to remove the offset component superimposed on the output of the Hall element. For this reason, in the imaging apparatus described in Patent Document 1, an offset amount to be removed is obtained from the output of the high-sensitivity Hall element, and the offset amount is subtracted from the output of the Hall element.

  However, if the output of the Hall element at the time of high sensitivity is already saturated, the offset amount to be removed cannot be obtained.

  Accordingly, an object of the present invention is to provide an imaging apparatus capable of performing offset removal stably regardless of use conditions, a control method thereof, and a control program.

  In order to achieve the above object, an optical apparatus according to the present invention is an optical apparatus that drives an imaging optical system along an optical axis to focus the imaging optical system on the subject when imaging a subject. Detecting means for detecting the position of the imaging optical system to obtain detected position information; setting means for setting the detection sensitivity of the detecting means; and the setting means sets the detection sensitivity of the detecting means to a predetermined low sensitivity. Obtained by the detection means when the detection sensitivity of the detection means is set higher than the low sensitivity by the setting means based on the detection position information obtained by the detection means when Correction means for correcting the detected position information.

  The control method according to the present invention includes a detection sensor that detects the position of an imaging optical system that can move along the optical axis and obtains detection position information. When imaging a subject, the imaging optical system is moved along the optical axis. An optical device control method for driving and focusing the imaging optical system on the subject, wherein a setting step for setting a detection sensitivity of the detection sensor, and a detection sensitivity of the detection sensor at a predetermined low level in the setting step Based on the detection position information obtained by the detection sensor when the sensitivity is set, the detection sensor when the detection sensitivity of the detection sensor is set higher than the low sensitivity in the setting step. And a correction step of correcting the obtained detected position information.

  A control program according to the present invention includes a detection sensor that detects a position of an imaging optical system that can move along an optical axis and obtains detection position information. When imaging a subject, the imaging optical system is moved along the optical axis. A control program used in an optical device that drives and focuses the imaging optical system on the subject, the setting step for setting the detection sensitivity of the detection sensor in a computer included in the optical device, and the setting step Based on the detection position information obtained by the detection sensor when the detection sensitivity of the detection sensor is set to a predetermined low sensitivity, the detection sensitivity of the detection sensor is higher than the low sensitivity in the setting step. And a correction step of correcting the detected position information obtained by the detection sensor when set to.

  According to the present invention, based on the detection position information obtained when the detection sensitivity is low, the detection position information obtained when the detection sensitivity is high is corrected. As a result, offset removal can be performed stably regardless of the use conditions.

It is a figure which shows the structure about an example of the imaging device as an optical apparatus by embodiment of this invention. It is sectional drawing which shows the structure of the camera shown in FIG. It is a figure for demonstrating the output of the magnetic sensor shown in FIG. 1, (a) is a figure which shows the output of a 1st magnetic sensor, (b) is a figure which shows the output of a 2nd magnetic sensor, (c). These are figures which show the relationship between the output of a 1st magnetic sensor, the output of a 2nd magnetic sensor, and the output (differential output) of a 1st differential amplifier. It is a figure for demonstrating an example of the scanning operation | movement of AF lens shown in FIG. It is a figure for demonstrating the other example of the scanning operation | movement of AF lens shown in FIG. 3 is a flowchart for explaining an example of an AF operation performed by the camera shown in FIG. 1.

  Hereinafter, an example of an imaging apparatus as an optical apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing the configuration of an example of an imaging apparatus as an optical apparatus according to an embodiment of the present invention.

  An imaging apparatus as an illustrated optical apparatus is, for example, a digital camera (hereinafter simply referred to as a camera), and includes an optical unit (also referred to as an imaging optical system or an optical system) having an AF lens 12. The AF lens 12 is movable along the photographing optical axis 11 as will be described later. The AF lens 12 is held by a lens holding frame 13, and this lens holding frame 13 is supported by a guide shaft 14 so as to be slidable in the direction of the photographing optical axis 11.

  The lens barrel portion 21 (FIG. 2) is provided with support portions 15a and 15b, and the guide shaft 14 is supported by the support portions 15a and 15b. A permanent magnet 16 is fixed to the lens holding frame 13, and this permanent magnet 16 is magnetized in the direction indicated by the arrow 16a in the figure. As a result, external magnetic fields 16 b and 16 c are formed by the permanent magnet 16.

  A core 18 is disposed opposite the permanent magnet 16, and a coil 17 is wound around the core 18 and fixed thereto. A pair of magnetic sensors (detection sensors) 19a and 19b such as Hall elements or MR elements are arranged at a predetermined interval along the extending direction of the guide shaft 14. A first differential amplifier 19c is connected to the magnetic sensors 19a and 19b. The first differential amplifier 19c amplifies and outputs the difference between the outputs of the magnetic sensors 19a and 19b.

  An imaging element (also referred to as an imaging unit) 110 is disposed at the subsequent stage of the optical system, and a subject image (optical image) is formed on the imaging element 110 via the optical system. Then, the image sensor 110 generates an image signal corresponding to the optical image. The image sensor 110 performs A / D conversion on the image signal and outputs it as image data.

  The camera body (FIG. 2) is provided with a CPU 111. The CPU 111 includes an evaluation value calculation unit 111a, an association unit 111b, a drive instruction unit 111c, a target value calculation unit 111d, a sensor control unit 111e, and an offset control unit 111f. The evaluation value calculation unit 111a obtains a contrast evaluation value related to the subject image based on the image data that is the output of the image sensor 110.

  The association unit 111b associates the position of the AF lens 12 (hereinafter simply referred to as the lens position) obtained in accordance with the outputs of the magnetic sensors 19a and 19b and the contrast evaluation value as an association signal as described later. Output. The drive instruction unit 111c outputs a drive instruction signal for controlling the driving of the AF lens 12 according to the association signal or the lens position and the output of the target position calculation unit 111d.

  The target position calculation unit 111d outputs the target position of the AF lens 12 to the drive instruction unit 111c and the sensor control unit 111e. The sensor control unit 111e controls the drive current applied to the magnetic sensors 19a and 19b according to the target position of the AF lens 12 that is the output of the target position calculation unit 111d. The offset controller 111f controls the timing for removing the offset component superimposed on the outputs of the magnetic sensors 19a and 19b.

  The coil drive unit 112 applies a drive current to the coil 17 based on a drive instruction signal that is an output of the drive instruction means. The sensor driving unit 113 applies a driving current to the magnetic sensors 19a and 19b based on the output of the sensor control unit 111e. The gain compensator 114 compensates the output of the first differential amplifier 19c based on the output of the drive instruction unit 111c.

  The first path switching unit 115 switches the output of the gain compensation unit 114 based on the output of the sensor control unit 111e. Here, the first path switching unit 115 refers to the output of the sensor control unit 111e, and when the sensitivity of the magnetic sensors 19a and 19b is high, the output of the gain compensation unit 114 is used as the compensation signal B as the second differential signal. The data is sent to the amplification unit 117 and the first sample hold unit (S / H 1) 116a. On the other hand, when the sensitivity of the magnetic sensors 19a and 19b is low, the output of the gain compensation unit 114 is sent as the compensation signal A to the second path switching unit 118 and the second sample hold unit (S / H 2).

  The first sample-and-hold unit 116a holds the compensation signal B based on the output timing of the offset control unit 111e as the compensation signal C. The second sample and hold unit 116b holds the compensation signal A based on the output timing of the offset control unit 111e as a compensation signal E.

  The second differential amplifier 117 differentially amplifies the compensation signal B and the compensation signal C to obtain a compensation signal D. Then, the compensation signal D, which is the output of the second differential amplifier 117, and the compensation signal E, which is the output of the second sample and hold unit 116b, are added to form a compensation signal D. The second path switching unit 118 selectively outputs the compensation signal A and the compensation signal D based on the output of the sensor control unit 111e. The amplification / ADC 119 amplifies the output of the second path switching unit 2 and A / D-converts it and sends it as a lens position to the CPU 111 (here, the association unit 111b and the drive instruction unit 111c).

  FIG. 2 is a cross-sectional view showing the structure of the camera shown in FIG.

  In addition to the AF lens 12, the optical system includes lenses 21a and 21b, an optical low-pass filter 22, and the like. The optical system is held by the barrel portion 21. Although not shown in FIG. 1, the diaphragm / shutter 23 is disposed downstream of the optical system, and the above-described imaging element 110 is disposed downstream of the diaphragm / shutter 24. The camera body 24 is provided with an image sensor 110 and a CPU 111, and a rear liquid crystal monitor 25 is disposed on the back thereof.

  The lens barrel portion 21 is supported by the camera body portion 24, and the CPU 111 provided in the camera body portion 24 controls the lens barrel portion 21 to perform zoom control, shutter control, and collapsible control.

  FIG. 2 shows an imaging apparatus in which the lens barrel portion 21 and the camera body portion 24 are integrated.

  With reference to FIGS. 1 and 2, a magnetic field is generated when the coil driving unit 112 passes a current through the coil 17. The AF lens 12 is driven along the photographing optical axis 11 (in the direction of the arrow 11a shown in FIG. 2) according to the magnetic field and the magnetic flux of the permanent magnet 16 (that is, the external magnetic fields 16a and 16b). The magnetic sensors 19a and 19b detect the position of the AF lens 12. In FIG. 1, the outputs of the magnetic sensors 19a and 19b change according to the external magnetic fields 16b and 16c by the magnet 16.

  FIG. 3 is a diagram for explaining the output of the magnetic sensor shown in FIG. FIG. 3A is a diagram showing the output of the first magnetic sensor, and FIG. 3B is a diagram showing the output of the second magnetic sensor. FIG. 3C is a diagram showing the relationship between the output of the first magnetic sensor, the output of the second magnetic sensor, and the output (differential output) of the first differential amplifier.

  In FIG. 3A, the change of the output of the magnetic sensor 19a with respect to the change of the magnetic field is shown, and the magnetic field change range is defined as shown. In the magnetic field change range, the output of the magnetic sensor 19a increases as indicated by the thick line 32a as the magnetic field decreases as indicated by the arrow 31a.

  FIG. 3B shows the change in the output of the magnetic sensor 19b with respect to the change in the magnetic field, and the magnetic field change range is defined as shown. Then, in the magnetic field change range, as the magnetic field increases as indicated by the arrow 31b, the output of the magnetic sensor 19b decreases as indicated by the thick line 32b.

  In FIG. 1, when the permanent magnet 16 is driven in a direction approaching the magnetic sensor 19b, the magnetic field applied to the magnetic sensor 19a decreases and the magnetic field applied to the magnetic sensor 19b increases.

  FIG. 3C shows the differential output 33 of the first differential amplifier 19c when the permanent magnet 16 is driven in a direction approaching the magnetic sensor 19b. The differential output 33 is an output corresponding to the difference between the output 32a of the magnetic sensor 19a and the output 32b of the magnetic sensor 19b.

  The output 32a of the magnetic sensor 19a and the output 32b of the magnetic sensor 19b have a narrow linear range (magnetic field change range) as shown in FIGS. 3A and 3B, but the differential output 33 has an output 32a. And 32b are canceled out, so the linear range is widened.

  Furthermore, the differential output obtained by the first differential amplification section 19c has an advantage that noise of in-phase components can be removed like a change in the external magnetic field. However, a large magnetic field change occurs with the driving of the coil 17 provided in the vicinity of the magnetic sensors 19a and 19b. Although this magnetic field change is an in-phase component with respect to the magnetic sensors 19a and 19b, it is a large change and may not be sufficiently removed by the differential output.

  On the other hand, the magnetic field generated by the coil 17 can be predicted in advance by a drive instruction signal that is an output of the drive instruction section 111c. The gain compensator 114 adjusts the gain of the first differential amplifier 19c based on the output of the drive instruction unit 111c to reduce the influence of the magnetic field generated by the coil 17 on the magnetic sensors 19a and 19b.

  In FIG. 1, the gain compensator 114 adjusts the gain of the first differential amplifying unit 19c. However, the gain compensation unit 114 directly adjusts the outputs of the magnetic sensors 19a and 19b to perform differential amplification. Also good.

  As described above, the obtained position information of the AF lens 12 is amplified to a predetermined dynamic range by the amplification / ADC 119, then A / D converted, and sent to the drive instruction unit 111c. The drive instruction unit 111c outputs a drive instruction signal for driving the AF lens 12 to the coil drive unit 112 according to the difference between the position information of the AF lens 12 and the target value sent from the target value calculation unit 111d. Such control is known feedback drive control, and the drive instruction unit 111c performs advance or delay phase control as necessary in order to stabilize the coil drive.

  Here, the output (target value) of the target value calculation unit 111d for driving the AF lens 12 in focus will be described.

  In the method of focusing using the contrast evaluation value of the image, the AF lens 12 is scanned within a predetermined range, and the position of the AF lens 12 having the largest contrast evaluation value in the scanning is in focus (focusing). Position).

  When scanning the AF lens 12, for example, the AF lens 12 is first positioned at a predetermined position (initial position) such as the end of the driving stroke. Then, the AF lens 12 is driven in a predetermined direction from the initial position. At this time, contrast evaluation values are sequentially obtained with a rough sampling period in accordance with the image data output from the imaging unit 110 (coarse scan).

  Subsequently, when the contrast evaluation value changes from increasing to decreasing, the driving of the AF lens 12 is stopped. Then, the AF lens 12 is scanned again in the vicinity of the region where the contrast evaluation value changes from increasing to decreasing. At this time, a contrast evaluation value is obtained at a dense sampling period according to the image data output from the imaging unit 110 (fine scan).

  Subsequently, the AF lens 12 is driven again to the position of the AF lens 12 at which the highest contrast evaluation value is obtained in the contrast evaluation values obtained at a dense sampling period.

  Note that, as described above, the final AF lens 12 is not in the position where the highest contrast evaluation value is obtained, but according to a curve connecting the contrast evaluation value groups obtained in a dense sampling period. A target position may be determined.

  FIG. 4 is a diagram for explaining an example of the scan operation of the AF lens shown in FIG.

  In FIG. 4, the horizontal axis indicates the time for scanning the AF lens 12 along the optical axis 10. The vertical axis indicates the contrast evaluation value that is the output of the evaluation value calculation unit 111a, the output (lens position) of the amplification / ADC 119 that is input to the CPU 111, and the target position.

  The target value, which is the output of the target value calculating means 111d, is indicated by a broken line 40a. Here, the AF lens 12 is already at the end of the driving stroke (for example, the position where the optical system is focused when the subject is at an infinite position). It is assumed that

  When a shooting preparation operation such as turning on the power of the camera or pressing the release button halfway is started, the target value increases as time passes. A curve 43 indicates the position of the AF lens 12 driven according to the target value indicated by the broken line 40a. As described above, the drive instructing unit 111 c drives the AF lens 12 by controlling the coil driving unit 112 according to the target value that is the output of the target value calculating unit 111 d and the position information of the AF lens 12. Therefore, the curve 43 follows the broken line 40a with a slight delay.

  Plots 43a to 44l are outputs (signals input from the amplification / ADC 119 to the CPU 111) of the magnetic sensors 19a and 19b when the AF lens 12 moves as indicated by the curve 43, and indicate the position of the AF lens 12. . As the AF lens 12 indicated by the curve 43 moves, the focus state of the subject image incident on the imaging unit 110 changes. As a result, the contrast evaluation value, which is the output of the evaluation value calculation unit 111a, changes.

  Plots 41a to 41f shown in FIG. 4 indicate contrast evaluation values that are outputs of the evaluation value calculation unit 111a. When the contrast evaluation value increases and starts decreasing as shown by the plot 41f, the target value calculation unit 111d fixes the output to the target value at the time when the output starts decreasing. Thus, it can be seen that the AF lens 12 has passed the in-focus position indicated by the plot 41e. The above operation is referred to as a rough scan 41.

  The CPU 111 sets a section (dense scan section) in which the AF lens 12 is driven (that is, scanned) again based on the change in the contrast evaluation value from the plot 41a to the plot 41f. The CPU 111 sets a peripheral section including the highest contrast evaluation value 41e among the contrast evaluation values 41a to 41f obtained in the rough scan 41 as a fine scan section. The target value calculation unit 111d outputs a target value for moving the AF lens 12 again in the fine scan section (broken line 40b).

  The AF lens 12 is driven based on this target value. At this time, the evaluation value calculation unit 111 a outputs the contrast evaluation value by sampling that is denser than the sampling in the coarse scan 41. Then, when the movement (that is, scanning) of the AF lens 12 in the reset scan section (fine scan section) is completed, the AF lens 12 stops at the scan end position. The above-described operation is called fine scan.

  As described above, when the driving of the AF lens 12 in the dense scan section is completed, the CPU 111 determines the most contrast evaluation value based on the contrast evaluation value 41l from the contrast evaluation value 41g obtained by the evaluation value calculation unit 111a in the dense scan section. The position of the AF lens 12 having a high value is obtained.

  For example, when the AF lens position corresponding to the highest contrast evaluation value is the plot 41 i, the associating unit 111 b associates the position 43 i corresponding to the contrast evaluation value as the position of the AF lens 12. When obtaining the highest contrast evaluation value from the curve connecting the contrast evaluation values 41g to 41l, when the highest contrast evaluation value is between the plot 41h and the plot 41i, the associating unit 111b sets the position 43h as The position between the positions 43 i is associated as the position of the AF lens 12.

  The associating unit 111b outputs the position of the AF lens 12 (for example, the position 43i) as a target value to the drive instructing unit 111c instead of the target value calculating unit 111d. Then, the drive instructing unit controls the coil driving unit 112 according to the difference between the output of the amplification / ADC 119 and the output of the associating unit 111b.

  As a result, the AF lens 12 is driven until the output of the amplification / ADC 119 reaches the position 43i and stops at the position 43i. The above-described operation is referred to as a focusing operation 46. In this way, the AF lens 12 is driven to the in-focus position, and the in-focus operation is completed.

  By the way, in the above-described scanning operation, the accuracy from the position 41g to the position 41l associated in the associating unit 111b becomes a problem. The magnetic sensors 19 a and 19 b are supplied with a driving current from the sensor driving unit 113 and detect the position of the AF lens 12. At this time, if the drive current supplied from the sensor drive unit 113 to the magnetic sensors 19a and 19b is large, the magnetic detection sensitivity becomes high and the position of the AF lens 12 can be detected with high accuracy.

  However, when the driving current supplied from the sensor driving unit 113 is increased, that is, when the magnetic detection sensitivity is increased, the magnetic field change is increased, and the outputs of the magnetic sensors 19a and 19b may be saturated. On the other hand, when the driving current supplied from the sensor driving unit 113 is small, saturation does not occur, but the magnetic detection sensitivity is low, and the position of the AF lens 12 cannot be detected with high accuracy.

  Therefore, here, in the rough scan section and the fine scan section, the driving current supplied from the sensor driving unit 113 to the magnetic sensors 19a and 19b is reduced (using the compensation signal A), and the AF lens 12 is operated under the condition that there is no saturation. Control. When the associating unit 111b associates the position detection output of the AF lens 12 with the contrast evaluation value of the evaluation value calculating unit 111a, the driving signal is increased and the compensation signal B is used. Further, the compensation signal B is used by increasing the drive current when performing the focusing operation.

  As a result, during the rough scan 41 and the fine scan 42, the AF lens 12 can be stably driven and controlled over the entire scan. In the focusing operation, the AF lens 12 can be driven and controlled with high accuracy.

  When performing the coarse scan 41, the sensor control unit 111e controls the sensor drive unit 113 so as to reduce the drive current supplied to the magnetic sensors 19a and 19b. Further, the first path switching unit 115 sends the compensation signal A, which is the output of the gain compensation unit 114, to the second path switching unit 118 under the control of the sensor control unit 111e. Then, the second path switching unit 118 sends the compensation signal A to the amplification / ADC 119 under the control of the sensor control unit 111e. During the fine scan 42, the sensor control unit 111e controls the sensor driving unit 113 to alternately increase / decrease the driving current for the magnetic sensors 19a and 19b.

  At the initial stage of the fine scan 42, the offset control unit 111f controls the first sample hold unit 116a to cause the first sample hold unit 116a to distribute the compensation signal B. The second differential amplification unit 117 outputs a differential amplification output between the hold value of the first sample hold unit 116a and the compensation signal B.

  The differential amplification output immediately after the differential amplification is zero because it is the difference between the hold value (compensation signal) C (equal to the compensation signal B) and the compensation signal B. The compensation signal B changes with the passage of time, but the hold value C does not change, so the differential amplification output changes. Further, the compensation signal A before outputting the compensation signal B is given to the second sample hold unit 116b. The second sample hold unit 116b samples and holds the compensation signal A and outputs a hold value E. Then, the differential amplification output D of the differential amplification unit 117 and the hold value E are added and sent to the second path switching unit 118 as a compensation signal D.

  Accordingly, the second path switching unit 118 performs compensation signal A (plots 43f, 43g, 43h, 43i, 43j, 43k, 43l) and compensation signal D (plots 44f, 44g, 44h, 44i, 44j, 44k, 44l). And are output alternately. In this way, the initial value of the compensation signal D (plot 44f) is almost the same output as the initial value of the compensation signal A (plot 43f). Since the compensation signal B is larger than the compensation signal A, it is saturated when the displacement of the AF lens 12 is large.

  Here, in FIG. 4, for example, a case where the compensation signal B is obtained when the AF lens 12 moves will be described.

  A straight line 45 indicates the detection position output of the AF lens 12 when the driving current applied by the sensor driving unit 113 to the magnetic sensors 19a and 19b is increased and a driving current five times the normal driving current is supplied. In this case, the straight line 45, that is, the detection position output reaches the output saturation level 47 soon after the driving of the AF lens 12 is started. The output saturation level 47 is determined by the dynamic range of the amplifier in front of the amplification / ADC 119. The position detection exceeding the output saturation level 47 always has a constant value as a saturation signal. That is, the position of the AF lens 12 cannot be detected.

  On the other hand, when the drive current applied to the magnetic sensors 19a and 19b by the sensor driving unit 113 is small, the position detection output of the AF lens 12 falls within the range of the output saturation level 47 as shown in plots 43a to 43l. The range is set to use all dynamic ranges.

  When performing the fine scan 42, the AF lens 12 is driven and controlled based on the compensation signal A (magnetic sensor output with low sensitivity). At this time, the compensation signal B (magnetic sensor output with high sensitivity) and the contrast evaluation value are associated with each other almost simultaneously. That is, since the compensation signal A is weak and has a lot of noise, it is not suitable to calculate the target value by associating the contrast evaluation value with the compensation signal A, so the compensation signal B and the contrast evaluation value are associated with each other.

  The sensor control unit 111e controls the drive current applied to the magnetic sensors 19a and 19b by driving and controlling the sensor drive unit 113 at a cycle of 10 kHz, for example. At this time, the compensation signal A and the compensation signal B are selectively output by the first path switching unit 115. The compensation signal A is input to the CPU 111 via the second path switching unit 118 and the amplification / ADC 119. Then, the drive instruction unit 111c controls the coil drive unit 112 based on the output of the amplification / ADC 119 and the target value that is the output of the target value calculation unit 111d.

  At the start of the fine scan 42 (at the time when the first path switching unit 115 switches to the compensation signal B after the plot 43f is obtained by the compensation signal A), the offset control unit 111f moves to the first sample hold unit 116a. Send sample hold signal. As a result, the first sample hold unit 116a samples and holds the compensation signal B and outputs a hold value (compensation signal) C. The second differential amplifier 117 outputs a differential amplified output of the compensation signal B and the compensation signal C. However, immediately after the start of the fine scan 42, the compensation signal C is equal to the compensation signal B. The dynamic amplification output becomes zero.

  The second sample hold unit 2 samples and holds the compensation signal A when the position of the AF lens 12 is the plot 43f under the control of the offset control unit 111e, and outputs it as the compensation signal E. The sum of the compensation signal E and the differential amplification output of the second differential amplification unit 117 is the compensation signal D.

  As a result, the compensation signal D is substantially equal to the lens plot 43f that initially indicates the position of the AF lens 12, as indicated by plots 43f to 43l shown in FIG. 4, and thereafter the compensation signal D is 5 compared to the plots 43f to 43l. Doubled.

  In this way, the plot 43f is close to the output saturation level 47 at the start of output, and thereafter moves away from the saturation level 47, so that the output of the amplification / ADC 119 is not saturated as the AF lens 12 moves.

  FIG. 5 is a diagram for explaining another example of the scan operation of the AF lens shown in FIG. In FIG. 5, the same elements as those in FIG. 4 are denoted by the same reference numerals.

  FIG. 5 shows an example in which the scanning operation is performed in the direction opposite to the scanning operation of the AF lens 12 shown in FIG. That is, FIG. 5 shows a case where the AF lens 12 is positioned at a position where the optical system is in focus when the subject is at a close position, and the AF lens is driven from that position. In this case, during the coarse scan 41, the output of the compensation signal A gradually decreases as shown by plots 43a to 43f. When the fine scan 42 is performed, the compensation signal D increases with the fine scan 42 from the same output as the plot 43f as shown by the plot 44f. However, since the compensation signal D in the plot 44f is small, the output saturation level 47 will not be exceeded even if the compensation signal D increases thereafter.

  FIG. 6 is a flowchart for explaining an example of the AF operation performed by the camera shown in FIG. The process according to the flowchart shown in the figure is performed under the control of the CPU 111.

  Now, when the shooting preparation start button is operated in the camera, the sensor control unit 111e controls the sensor drive unit 113 to reduce the drive current applied to the magnetic sensors 19a and 19b (step S6001). Then, the CPU 111 takes in the compensation signal A, which is the output of the first path switching unit 114, through the second path switching unit 118 and the amplification / ADC 119 (step S6002).

  Subsequently, the drive instruction unit 111c drives and controls the coil drive unit 112 based on the compensation signal A and the target value, and applies a drive current to the coil 17 (step S6003). As a result, the AF lens 12 starts a rough scan.

  Next, the evaluation value calculation unit 111a takes in image data that is the output of the imaging unit 110 at a predetermined period (for example, 1/120 second), and obtains a contrast evaluation value (step S6004). Then, the drive instruction unit 111c determines whether or not the contrast evaluation value has passed the maximum value (maximum value: vertex) (step S6005). That is, here, the drive instruction unit 111c determines whether or not the contrast evaluation value obtained in time series with the driving of the AF lens 12 has started to decrease.

  If the contrast evaluation value does not pass the maximum value (NO in step S6005), drive instruction unit 111c returns to the process in step S6003. On the other hand, when the contrast evaluation value passes the maximum value (NO in step S6005), the drive instruction unit 111c controls the coil drive unit 112 based on the target value that is the output of the target value calculation unit 111d to control the AF lens 12. The drive is stopped (step S6006).

  Subsequently, the sensor control unit 111e controls the sensor driving unit 113 to increase the driving current applied to the magnetic sensors 19a and 19b (step S6007). Then, the drive instruction unit 111c takes in the compensation signal B, which is the output of the first path switching unit 114, via the second differential amplification unit 117, the second path switching unit 118, and the amplification / ADC 119. Hold as a (first detection position information) (step S6008).

  Next, the sensor control unit 111e controls the sensor driving unit 113 to change the driving current applied to the magnetic sensors 19a and 19b to small (step S6009). Then, the drive instruction unit 111c takes in the compensation signal A, which is the output of the first path switching unit 114, via the second path switching unit 118 and the amplification / ADC 119, and serves as a signal b (second detection position information). Hold (step S6010).

  Next, the drive instruction unit 111c performs a calculation c = a−b, which is a process of subtracting the signal b from the signal a (step S6011). As a result, a composite signal (that is, an offset component) c of the offset component of the compensation signal B to be removed and the offset component of the compensation signal A to be added is obtained.

  Subsequently, the sensor control unit 111e controls the sensor driving unit 113 to alternately switch the driving current applied to the magnetic sensors 19a and 19b between large and small (step S6012). Then, the CPU 111 takes in the compensation signal B and the compensation signal A in the same manner as the processing in step S6002 (step S6013). At this time, the compensation signal B is used for correlation with the contrast evaluation value, and the compensation signal A is used for driving control of the AF lens 12.

  Next, the drive instruction unit 111c detects the position of the AF lens 12 based on the compensation signal A, and drives and controls the coil drive unit 112 in accordance with the position and the target value to apply a drive current to the coil 17. (Step S6014). As a result, the AF lens 12 starts a fine scan.

  Note that the range of the fine scan is a range of plots 41d to 41f sandwiching the apex (near the plot 41e) as shown in FIG.

  Subsequently, the drive instruction unit 111c subtracts the offset component c from the compensation signal B (step S6015). As a result, the subtracted compensation signal B has the same value as the plot 43f, which is the value of the compensation signal A, as indicated by a plot 44f in FIG. Next, the evaluation value calculation unit 111a calculates a contrast evaluation value based on the image data that is the output of the imaging unit 110 (step S6016).

  The associating unit 111b records the contrast evaluation value and the position of the AF lens 12 in association with each other (step S6017: pairing). The position of the AF lens 12 at this time is a position obtained in step S6015 described later, and is a position indicated by plots 44f to 44l shown in FIG.

  Subsequently, the drive instruction unit 11c determines whether scanning has been performed in the dense scan range (step S6018: reach range). If the range has not been reached (NO in step S6018), the process returns to step S5012. On the other hand, if the range has been reached (YES in step S6018), the drive instruction unit 111c determines the position of the AF lens 12 having the highest contrast evaluation value according to the change in the contrast evaluation value obtained in the process of step S6016. Ask. Then, the drive instruction unit 111c sets the target position of the AF lens 12 based on the position detection output associated in step S6017 (step S6019; target value setting).

  Subsequently, the sensor control unit 111e controls the sensor driving unit 113 to increase the driving current applied to the magnetic sensors 19a and 19b (step S6020). Then, the drive instructing unit 111c takes in the compensation signal B in the same manner as in step S6015, and subtracts the offset component c from the compensation signal B in the same manner as in step S6015 (step S6021).

  Next, the drive instruction unit 111c detects the position of the AF lens 12 based on the compensation signal B after subtraction. Then, the drive instructing unit 111c drives and controls the coil driving unit 112 based on the position of the AF lens 12 and the target value that is the output of the target value calculating unit 111d, and applies a driving current to the coil 17 (step S6022). Focus control).

  Thus, in the focus control, the drive current applied to the magnetic sensors 19a and 19b is increased. At this time, since the control feedback gain is changed, adjustment for adjusting the gain is performed.

  Subsequently, the drive instruction unit 11c determines whether or not the AF lens 12 has reached the target position (plot 44i shown in FIG. 4) (step S6023). If the AF lens 12 does not reach the target position (NO in step S6023), the drive instruction unit 11c returns to the process of step S6021. On the other hand, when AF lens 12 reaches the target position (NO in step S6023), drive instruction unit 11c ends the AF operation.

  Thus, in the embodiment of the present invention, the detection position when the magnetic sensor is set to high sensitivity is corrected based on the detection position of the AF lens when the magnetic sensor is set to low sensitivity. Thereby, drive control of the imaging optical system can be performed with high accuracy.

  As is clear from the above description, in the example shown in FIG. 1, the drive instruction unit 111c and the coil drive unit 112 function as drive control means. The permanent magnet 16, the magnetic sensors 19a and 19b, and the differential amplifier 19c function as detection means. Further, the sensor control unit 111e and the sensor driving unit 113 function as setting means. The drive instruction unit 111c, the offset control unit 111f, the first sample hold unit 116a, the second sample hold unit 116b, and the second difference image amplification unit 117 function as correction means.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to these embodiment, Various forms of the range which does not deviate from the summary of this invention are also contained in this invention. .

  For example, the function of the above embodiment may be used as a control method, and this control method may be executed by the imaging apparatus. Further, a program having the functions of the above-described embodiments may be used as a control program, and the control program may be executed by a computer included in the imaging apparatus. The control program is recorded on a computer-readable recording medium, for example.

[Other Embodiments]
The present invention supplies a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and one or more processors in a computer of the system or apparatus read and execute the program This process can be realized. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

12 AF lens 16 Permanent magnet 19a, 19b Magnetic sensor 110 Imaging element (imaging part)
111 CPU
111a Evaluation value calculation unit 111c Drive instruction unit 111e Sensor control unit 111f Offset control unit 112 Coil drive unit 113 Sensor drive unit

Claims (8)

When imaging a subject, an optical device that drives the imaging optical system along an optical axis to focus the imaging optical system on the subject,
Detection means for detecting the position of the imaging optical system to obtain detection position information;
Setting means for setting the detection sensitivity of the detection means;
Based on the detection position information obtained by the detection means when the detection sensitivity of the detection means is set to a predetermined low sensitivity by the setting means, the detection sensitivity of the detection means by the setting means is lower than the low sensitivity. Correction means for correcting the detected position information obtained by the detection means when set to a high sensitivity,
An optical apparatus comprising: The detection means changes the detection sensitivity according to the magnitude of the applied drive current,
The optical apparatus according to claim 1, wherein the setting unit changes the detection sensitivity by changing a magnitude of a drive current applied to the detection unit. Drive control means for driving and controlling the imaging optical system along the optical axis;
3. The optical apparatus according to claim 1, wherein when the imaging optical system is driven and controlled by the drive control unit, the setting unit changes detection sensitivity of the detection unit. The detection means includes a permanent magnet provided in the imaging optical system;
The optical apparatus according to claim 1, further comprising: a pair of Hall elements arranged at a predetermined interval along the optical axis.   When the sensitivity of the detection unit is set to the low sensitivity by the setting unit, the drive control unit is obtained via the imaging optical system by driving the imaging optical system along the optical axis. The optical apparatus according to claim 3, wherein driving of the imaging optical system is stopped when passing through a position where a contrast evaluation value corresponding to an image is maximized. When the drive of the imaging optical system is stopped by the drive control unit, the setting unit sets the sensitivity of the detection unit to high sensitivity, and the correction unit detects detection position information obtained by the high sensitivity detection unit. Is obtained as the first detected position information,
When the first detection position information is obtained, the setting means lowers the sensitivity of the detection means, and the correction means detects the detection position information obtained by the low sensitivity detection means as a second detection. The optical apparatus according to claim 5, wherein the optical apparatus is obtained as position information, and the first detected position information is corrected with the second detected position information. The image pickup optical system includes a detection sensor that detects a position of an image pickup optical system movable along the optical axis and obtains detection position information, and drives the image pickup optical system along the optical axis when picking up a subject. A method of controlling an optical device that focuses on the subject,
A setting step for setting the detection sensitivity of the detection sensor;
Based on the detection position information obtained by the detection sensor when the detection sensitivity of the detection sensor is set to a predetermined low sensitivity in the setting step, the detection sensitivity of the detection sensor in the setting step is lower than the low sensitivity. A correction step for correcting the detected position information obtained by the detection sensor when the high sensitivity is set,
A control method characterized by comprising: The image pickup optical system includes a detection sensor that detects a position of an image pickup optical system movable along the optical axis and obtains detection position information, and drives the image pickup optical system along the optical axis when picking up a subject. A control program used by an optical device for focusing the subject on the subject,
In the computer provided in the optical device,
A setting step for setting the detection sensitivity of the detection sensor;
Based on the detection position information obtained by the detection sensor when the detection sensitivity of the detection sensor is set to a predetermined low sensitivity in the setting step, the detection sensitivity of the detection sensor in the setting step is lower than the low sensitivity. A correction step for correcting the detected position information obtained by the detection sensor when the high sensitivity is set,
A control program characterized by causing