JPH09203643A - Method for detecting position and driving control apparatus of optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To highly accurately detect continuous position signals well even when a value of an intersection of position signals is changed because of an amplitude change of detection signals by obtaining the value of the intersection of the position signals during an actual operation and operating a position. SOLUTION: A value of an intersection CRS PNT is calculated from position signals Xa[n], Xb[n] of A, B phases at a control time point TRK n and position signals Xa[n-1], Xb[n-1] of A, B phases at a control time point TRKn-1. A target position and the present position are corrected with the utilization of the thus-calculated values of intersections whereby a vibrating state is prevented from being generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for detecting the position of an optical element such as a lens and a diaphragm in a camera or a video camera and an improvement in a drive control device.

[0002]

BACKGROUND ART In conventional cameras and video cameras,
Step motors are often used as lens driving means, and the lens position is obtained by counting step pulses for control. However, as the functions and performances of cameras and video cameras have become higher and higher in recent years, it is necessary to drive the lens at high speed and with high accuracy, and further downsizing and weight saving are also demanded. Therefore, recently, a voice coil motor has been used as a lens driving means, and a position detecting means for detecting the lens position at high speed and with high accuracy has been required.

FIG. 1 is a block diagram of a lens drive controller. The target of drive control is the zoom lens group 4, which performs zooming, the diaphragm 5, and the focus lens group 6, which performs focus adjustment. These are driven by actuators 7, 8, 9 respectively, and these actuators 7, 8, 9 are driven by drive circuits 10, 11, 12. Zoom lens group 4, aperture 5, focus lens group 6
The positions of are detected by the position detectors 1, 2 and 3, respectively. The image pickup device 13 is arranged on the same optical axis as the lens groups 4, 6 and diaphragm 5, and desired image information can be obtained by the image signal processing circuit 14.

The CPU 15 for position control functionally includes a target position calculation unit 16, a lens position calculation unit 17, a position error calculation unit 18, and a control unit 19. The target position calculation unit 16 calculates the target positions of the lens groups 4, 6 and the diaphragm 5. The lens position calculator 17 calculates the positions of the lens groups 4, 6 and the diaphragm 5 from the position information detected by the position detectors 1, 2, 3. The position error calculation unit 18 calculates a position error from the target position calculated by the target position calculation unit 16 and the position of each part calculated by the position calculation unit 17. In the control unit 19,
The positions of the lens groups 4 and 6 and the diaphragm 5 are controlled by using the drive circuits 10, 11 and 12 so that the position error of each part calculated by the position error calculation unit 18 is eliminated.

FIG. 2 shows an application example in which a voice coil motor is used as the actuators 7, 8 and 9.
In the figure, the lens group 31 is held by a lens holding frame 32, and a drive coil 33 is wound around the lens holding frame 32. The lens holding frame 32 is a guide shaft 34.
The guide shaft 34 is supported by a mounting seat 37. A magnet 35 and a yoke 36 are housed and held in the mounting seat 37, and a position detecting element 38 for detecting the position is provided on one shaft side of the lens holding frame 32.
A lid 39 is attached to the attachment seat 37 after storage.

The lens holding frame 32 is freely movable in the optical axis direction along a guide shaft 34 fixed in parallel. Then, a driving force is generated by passing a current through the driving coil 33, and the lens group 31 held by the lens holding frame 32 slides in the optical axis direction.

The position detecting element 38 is a contact type such as a direct acting variable resistor, a non-contact type such as one using a magnet and a magnetoresistive (MR) element, or one using a light emitting element and a light receiving element. Things are being considered. In any case, high-speed, high-precision (high-resolution) position detection is required in the entire lens movement range.

As a method of using an MR element as a position detecting element, there is a position detecting device disclosed in Japanese Patent Laid-Open No. 4-233411, for example. According to this, in the detection signal composed of a plurality of phases, a signal portion having a high linearity between the intersections of the respective phases is extracted as a position signal. For example, the position signal in the case of a detection signal having three phases is as shown in FIG. The three-phase signals A, B, and C change in a sine wave shape with phase differences of equal intervals, but between the intersections of the phases of these signals (displayed by thick lines), a highly linear waveform is obtained. ing. Therefore, it is possible to obtain a highly accurate position signal by using these sawtooth-shaped signals with high linearity as the position signal and detecting the value between the intersections. Even when the light emitting element and the light receiving element are used, highly accurate position detection can be performed similarly.

[0009]

However, in the position detecting method for extracting the highly linear portion of the detection signal composed of a plurality of phases as the position signal, the detection signal having the same amplitude in the entire lens movement range is used. It is difficult to obtain the characteristics of the detection element and the assembling accuracy. In addition, the amplitude of the detection signal may change due to changes in environmental temperature. When such an amplitude change of the detection signal occurs,
The value of the intersection of each phase changes depending on the lens position.
Since the lens position is calculated with the value of the intersection as a reference, the detection accuracy of the lens position is lowered, or a discontinuous point of the detection position occurs.

Further, when the target position is given by the number of tracks (the number of linear portions of sawtooth wave) and the value of the position signal, the intersection position may become smaller than the target position due to the decrease of the position signal amplitude. is there. Then, the actual lens position corresponding to the target position does not exist, and there is the inconvenience that a vibrating state occurs at a position sandwiching the intersection.

Further, in the case where the target position is given by an absolute position from a preset optical origin (an arbitrary optical reference point, for example, an intersection of the image pickup surface and the optical axis), the amplitude changes The value of the intersection of each phase of the detection signal changes. Therefore, there is a disadvantage that a discontinuity occurs in the calculated position error even though the lens is moving at a constant speed. When such a discontinuity occurs, there arises a problem that the operation noise becomes loud especially at low speed operation.

The present invention focuses on the above points,
When extracting the signal part with high linearity between the intersections of each phase in the detection signal consisting of multiple phases and using it as the position signal, even if the value of the intersection changes due to the amplitude change of the detection signal, it is possible to achieve high accuracy with good accuracy. It is an object of the present invention to provide an optical element position detection method and drive control device capable of detecting continuous position signals.

[0013]

In order to achieve the above object, according to the present invention, the value of the intersection of each phase in a detection signal composed of a plurality of phases is detected or estimated during the control operation of an optical element. The target position and the current position are calculated based on.

As a result, when the target position is given by the number of tracks and the value of the position signal, the vibration generated at the position sandwiching the intersection is reduced. Further, when the target position is given by the absolute position from the reference point, the operation sound at the time of low speed operation generated by the change of the position signal amplitude is reduced.

The above and other objects, features and advantages of the present invention will be apparent from the following detailed description and the accompanying drawings.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to Examples. In the following description, the case where three-phase detection signals are output from the lens position detection element will be described as an example.

[0017]

Example 1 First, a basic lens position measuring method using a magnetoresistive element will be described by taking the case shown in FIG. 3A as an example. As described above, the three-phase signal composed of the A, B, and C phases changes in a sinusoidal shape with the phases at equal intervals, and the signal is highly linear between the intersections of the phases. . A highly accurate lens position measurement can be performed by detecting the value (signal level) between the intersections by using the sawtooth signal having a high linearity and shown by a thick line as a position signal.

In this method, however, the signal level and the lens position do not have a 1: 1 correspondence, as shown in FIG. Therefore, it is possible that the lens positions are different even though the signal levels are the same.
Therefore, the lens position is determined by the number of tracks, which is the number of linear portions of the sawtooth wave, and the value of the linear portion of the position signal.

Next, focusing on the track, there are six types of modes shown in Table 1 below, that is, position signal modes, depending on the magnitude relationship of the three-phase detection signals A to C. For example, in mode 0, as shown in FIG. 3A, the magnitude relationship of the position signals A to C is C>A> B, and the linear portion, that is, the effective position signal is in the A phase. Similarly, in mode 1, the magnitude relationship of the position signals A to C is C>B> A,
The straight line portion, that is, the effective position signal is the B phase. The same applies to modes 2 to 5. 0 like this
Six modes from 5 to 5 are repeated.

[0020]

[Table 1]

Next, the current number of tracks is counted due to the change in the position signal mode at each position detection time point. The above-mentioned 6 types of position signal modes can be selected from "T MODE 0 ~
The relationship with the position signal when the switching level of the position signal, that is, the value of the signal at the intersection is expressed by "CRSPNT 0-5" is shown in Table 2 below. For example, CRSPNT 0
Is an intersection point on the lower side (minus side) of the A phase and the B phase, as shown in FIG. Similarly, CRSPNT 1 is the intersection of the B phase and the C phase on the upper side (plus side). CRSPNT 2-5
The same applies to. Such CRSPNT 0 to 5 are repeated. FIG. 3A shows the relationship among the position signals A to C, the position signal modes T MODE 0 to 5, and the intersection point values CRSPNT 0 to 5.

[0022]

[Table 2]

The change amount within the position detection time which can be discriminated only by the change of the position signal mode is ± 2 tracks. For example, in FIG. 3A, the position signal mode is “CRSPNT
3 ”. On the other hand, for the positions of ± 3 tracks, the position signal mode is “CRSPNT 0” on both the left and right sides, and it is impossible to distinguish between the CRSPNT 0 track on the left side and the CRSPNT 0 track on the right side in the figure. Therefore, it is ± 2 tracks that can be identified only by the change in the position signal mode. However, it is possible to discriminate up to ± 5 tracks by introducing a discrimination method that takes speed into consideration.

The amount of change in the count value of the number of tracks is shown in FIG.
As shown in, the amount of change between the position signal mode (T MODEn-1) at the time of previous position detection (displayed with a black circle in the figure) and the position signal mode (T MODEn) at the time of detection of the current position (displayed with a white circle in the figure) Can be obtained by Table 3 summarizes the changes at this time. For example, as shown by arrow F1 in FIG. 4, when the signal mode T MODEn-1 at the previous position is “3” and the signal mode T MODEn at the current position is “2”, the track is moving to the right adjacent track. , Track count change Δ
TRK CNT becomes "-1". As shown by arrow F2 in FIG. 4, when the signal mode T MODEn-1 at the previous position is “3” and the signal mode T MODEn at the current position is “5”, the track is moving to the left adjacent track, Count change ΔTRK CN
T becomes “+2”. Others are the same.

[0025]

[Table 3]

Next, the number of tracks at the target position and the value of the position signal are represented by "TRGT TRK" and "TRGT POS", respectively, and the number of tracks at the current position and the value of the position signal are "TRK CNT",
It is represented by "POS". In a camera or video camera, the target position of the lens is given at the beginning of each field of the image. When the lens operates stepwise as shown in FIG. 5, such a way of expressing the target position is performed.

When the number of tracks at the target position and the number of tracks at the current position match, that is, when TRGT TRK = TRK CNT, they are within the same track, so the position error amount ERR
Can be obtained from the difference between the target position signal TRGT POS and the current position signal POS.

When the target number of tracks and the number of tracks at the current position do not match and both positions deviate within a range of ± 1 track, as shown in FIG. 6, the intersection of the corresponding position signal modes is changed. Using the value CRSPNT, it can be calculated by the following equation (1). This formula is the intersection point CRSPNT
It is calculated by extending the straight line portion from [n] to CRSPNT [n-1] and projecting points a and b on a'and b '.

[0029]

[Equation 1]

Even when the number of tracks at the target position and the number of tracks at the current position deviate by ± 1 track or more, the position error can be calculated in the same manner. However, since the values of the respective intersections are different, the amount of calculation increases, which makes it considerably complicated.

As described in the background art, the amplitude of the detection signal may change depending on the lens position, or the amplification of the detection signal may change depending on the change of the environmental temperature. For example, consider the case where the amplitude of the detection signal has become small as shown in FIG. Due to the decrease in the amplitude, the value of the intersection of each phase of the detection signal is changed from "CRS PNT REF" to "CRS PNT REA".
It will change to "L".

Here, consider the case where the target position is given by TRGT TRK = n, TRGT POS> CRSPNT REAL, as indicated by the white circles in the figure. The position error ERR at this time is shown in FIG.
It becomes as shown in. In the figure, (A) shows the case where the current position POS is TRK n, and (B) shows the case where the current position POS is TRK n-1. In either case, the intersection position is smaller than the target position due to the decrease in the position signal amplitude. Therefore, the actual lens positions that satisfy the target positions TRGT TRK = n and TRGT POS will not exist. Therefore, when the detection signal of the phase that represents the position signal in TRK n reaches TRGT POS,
The tracks have already been switched. In such a state, the lens cannot reach the target position, and the lens vibrates at the positions sandwiching the intersection. In order to improve such inconvenience, in the first embodiment, the value of the intersection is detected or estimated during the actual control operation.

By the way, in order to detect the value of the intersection (signal level of the intersection) during the control operation, the lens must pass through the intersection. However, it is convenient that the change in the position signal amplitude causes inconvenience because the lens movement is performed while the intersection is sandwiched as described above, and the value of the intersection can be detected.

As a concrete method of detecting the value of the intersection, first, as shown in FIG. 10, there is a method of obtaining from the signal value of each phase before and after passing through the intersection. As described above, the position mode is obtained from the magnitude relationship of the detection signals of each phase (Table 1
The number of tracks is counted based on this). Therefore, the value of the detection signal of each phase at the control time points TRK n-1 and TRK n has already been obtained.

In the example of FIG. 10, the position signals Xa [n] and Xb [n] of the A and B phases at the control time TRK n and the control time TRK.
Position signals Xa [n-1] and Xb [n-1] of A and B phases at n-1
From this, the value of the intersection CRS PNT can be calculated by the following equation (2).

[0036]

[Equation 2]

By thus calculating the value of the intersection and correcting it as shown in FIG. 9 and also correcting the target position, the occurrence of the above-mentioned vibration state can be avoided. The calculation method of equation (2) gives an approximate value. However, the change amount of the intersection value due to the change in the detection signal amplitude becomes a problem when the lens position control state is the settling or tracking state, and since the movement amount within one control time is small, Even with such an approximate simple calculation, the value of the intersection can be accurately obtained. Of course, it does not prevent the calculation of the value of the intersection with higher accuracy.

As described above, the lens position can be accurately obtained by correcting the value of the intersection during the lens movement control operation. Further, it is conceivable to increase the accuracy to calculate the position error when the error amount is small, and to decrease the accuracy to reduce the calculation amount when the error amount is large. As an example, as shown in FIG. 11, when the current position with respect to the target position TRGT POS is TRGT TRK ± 1 track, the position error is accurately calculated, and when the position is deviated by more than that, The position error is roughly calculated. For example, FIG.
As shown in, when the error is large, the accuracy is reduced by using the average value CRS O on the upper side of each phase, the average value CRS E on the lower side, and the average value CRS AVE of the level difference of the linear part, and the error is large. It is possible to reduce the calculation amount of.

An example of rough calculation of the position error using the average value in the case shown in FIG. 13 is given by the following equation (3). Here, TRK CNT is the count value of the number of tracks.

[0040]

(Equation 3)

[0041]

Second Embodiment Next, a second embodiment of the present invention will be described. In order to keep the focus in focus while the zoom lens is moving, the position of the focus lens must be moved corresponding to the position of the zoom lens. In such a case, the lens movement, that is, the zoom tracking operation is a continuous operation unlike the step operation as shown in FIG.

Generally, position control is performed by PTP control (Point To
Point control) and CP control (Continuous Path cont
rol). The PTP control is a control method in which only a target position is given and a trajectory until reaching the target position is not specified, like a step operation. On the other hand, in CP control, a target position is given at each control time point,
This is a control method that follows the trajectory.

In the case of zoom tracking operation, the target position of the focus lens changes as the zoom lens moves, so it is necessary to perform CP control as shown in FIG. 14, for example. During such CP control operation, it is necessary to calculate the target position at each control time point. Therefore, considering the calculation algorithm and the amount of calculation for that purpose, the target position should be calculated from an appropriate reference point, for example, the optical origin position. It is desirable to express by the continuous absolute position of. Then, the current position from the optical origin can be obtained by sequentially adding the movement amounts from the previous control time point.

FIG. 15 shows an example. The target position from the optical origin is “Z POS TRGT”, the position signal value at the time of the previous control is “POS BUF”, the current position signal value is “POS”, and the current position from the optical origin is “Z POS TRGT”. POS ”.
When calculating the position error when the target position is represented by the absolute position from the optical origin, the difference between the current number of tracks and the number of tracks at the time of the previous control is within ± 1 track, as shown in FIG. As described above, the value CRSPNT at the intersection of the corresponding position signal modes can be used to calculate as in equation (4) below.

[0045]

(Equation 4)

As described above, even when the lens position is represented by the absolute position from the optical origin, the current position is calculated by counting the current number of tracks due to the change in the position signal mode at each control point as described above. That is no different. Even if the difference between the current number of tracks and the number of tracks at the time of the previous control is deviated by ± 1 track or more,
Similarly, the position error can be calculated. But,
Since the values of the respective intersections are different, the amount of calculation increases, which makes it considerably complicated.

Also in this case, the amplitude of the detection signal may change depending on the lens position, or the amplitude of the detection signal may change due to the change of the environmental temperature, and the value of the intersection of each phase of the detection signal may change. However, even though the lens is moving at a constant speed, a discontinuity occurs in the calculated position error. Then, similarly, there is an inconvenience that an operation sound becomes loud especially at a low speed operation.

FIG. 16 shows how such a discontinuity occurs. The value of the intersection of each phase of the detection signal also changes from "CRS PNT REF" to "CRS PNT REAL" due to the change in amplitude. Here, if the actual lens position is "POS", the absolute position "Z POS" from the optical origin is
An error that is twice the amount of change in the value of the intersection will occur. Due to this error amount, a discontinuity occurs in the position error calculated when the lens passes the intersection. In order to improve such inconvenience, also in the second embodiment, the value of the intersection is detected or estimated during the actual control operation.

By the way, as a method of detecting the value of the intersection,
For example, as shown in FIG. 10, there is a method of obtaining from the signal value of each phase before and after passing through the intersection. Intersection value "CR
“SPNT” is calculated from the equation (2). Further, similarly to the first embodiment, the accuracy may be increased to calculate the position error when the error amount is small, and the accuracy may be decreased to reduce the calculation amount when the error amount is large. For example, as shown in FIG. 17, when the difference between the current number of tracks and the number of tracks at the time of the previous control is ± 1 track, the position error is accurately calculated. Calculated by using the average value of the intersection points of each phase shown in 12 with reduced accuracy,
The calculation amount can be reduced when the error is large.
Further, as shown in FIG. 18, the average value may be used to roughly calculate the position error as in the following expression (5).

[0050]

(Equation 5)

[0051]

Other Embodiments The present invention has many embodiments and can be variously modified based on the above disclosure. For example, the following is also included. (1) In the above embodiment, the case where the output of the magnetoresistive element is three phases has been described, but the number of phases may be appropriately set as necessary. The measurement accuracy improves as the number of phases increases. (2) The calculation formulas such as the values of the intersections shown in the above embodiment are also examples, and may be calculated by an appropriate formula as necessary. (3) The above embodiment is an example of detecting the position of the lens,
The same applies to other optical elements such as a diaphragm.

[0052]

As described above, according to the present invention,
It has the following effects. (1) Since the position calculation is performed by obtaining the value of the intersection of the position signal during the actual operation, vibration at the positions sandwiching the intersection is reduced, and stable operation is possible. (2) Also, when the position is absolutely given from the reference point, the occurrence of operating noise due to the discontinuity of the position error calculated when the lens is operating at low speed is reduced, and similarly. Stable operation becomes possible. (3) When the error between the target position and the current position is large, the average value of the intersections of the phases of the position signal is used to calculate the target position and the current position. It is possible to reduce the calculation amount when is large.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of a lens driving device.

FIG. 2 is an exploded perspective view showing an example of a voice coil motor.

FIG. 3 is an explanatory diagram showing an example of a position signal composed of three phases and another example of the position signal.

FIG. 4 is an explanatory diagram showing how the number of tracks is counted.

FIG. 5 is an explanatory diagram showing a step operation of a lens.

FIG. 6 is an explanatory diagram showing an example of a position error calculating method.

FIG. 7 is an explanatory diagram showing an influence when a value of an intersection changes.

FIG. 8 is an explanatory diagram showing a position error when the value of the intersection changes.

FIG. 9 is an explanatory diagram showing how the intersection value and the target position are corrected.

FIG. 10 is an explanatory diagram showing a method of calculating an intersection value.

FIG. 11 is an explanatory diagram showing how the position error calculation method is switched.

FIG. 12 is an explanatory diagram showing an average value of position signals.

FIG. 13 is an explanatory diagram showing a state of rough calculation of position error.

FIG. 14 is an explanatory diagram showing an example of a tracking operation of a lens.

FIG. 15 is an explanatory diagram showing an example of a position error calculation method.

FIG. 16 is an explanatory diagram showing how discontinuities are generated.

FIG. 17 is an explanatory diagram showing how the position error calculation method is switched.

FIG. 18 is an explanatory diagram showing a state of rough calculation of a position error.

[Explanation of symbols]

 1, 2, 3 ... Position detector 4 ... Zoom lens 5 ... Aperture 6 ... Focus lens 7, 8, 9 ... Actuator 10, 11, 12 ... Drive circuit 13 ... Image sensor 14 ... Video signal processing circuit 15 ... CPU 16 ... Target position calculation unit 17 ... Lens position calculation unit 18 ... Position error calculation unit 19 ... Control unit 31 ... Lens group 32 ... Holding frame 33 ... Drive coil 34 ... Guide shaft 35 ... Magnet 36 ... Yoke 37 ... Mounting seat 38 ... Position detection Element 39 ... Lid

Claims (4)

[Claims] 1. A position detection of an optical element for detecting the position of an optical element by utilizing a signal between intersections of sinusoidal position signals composed of a plurality of phases having equal phase differences output from the position detection element. In the method, during the operation of controlling the optical element from the current position to the target position, an intersection point value calculating step of obtaining a value of an intersection point of each phase of the position signal; A method for detecting the position of an optical element, comprising a calculation step for calculating the position. 2. When the target position and the current position are represented by the number of intersections of each phase of the position signal and the signal between the intersections, the calculation step has a large error between the target position and the current position. In this case, the target position and the current position are calculated by using the average value of the intersections of the respective phases of the position signal, and the position detecting method of the optical element according to claim 1. 3. When the target position and the current position are represented as absolute values from a preset reference point, the calculation step is performed when the movement amount of the optical element within the control interval of the optical element is large. The position detecting method for an optical element according to claim 1, wherein the target position and the current position are calculated using an average value of intersections of the phases of the position signal. 4. A position detecting element for outputting a sinusoidal position signal composed of a plurality of phases having equal phase differences; position detecting means for extracting a signal between intersections of the respective phases of the position signal; position detecting Position detecting means for calculating the position of the optical element by the method according to claim 1, 2 or 3 based on the detection signal detected by the means; target position calculating means for calculating the target position of the optical element; A drive control of an optical element, comprising: a position error calculation means for calculating a position error from the position and the current position; a control means for controlling the position of the optical element based on an output value of the position error calculation means. apparatus.