JP4500287B2 - Autofocus system apparatus and method capable of compensating load force fluctuation - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an autofocus system apparatus for optical photographing equipment and a method thereof, and more particularly, to an autofocus system apparatus for optical photographing equipment capable of providing compensation control for external load force, rocking and stagger. It relates to that method.

A conventional autofocus system employs a step motor as an autofocus actuator, but has the following drawbacks.
1. The focus time is not fast enough and cannot be applied to high quality mobile photography devices.
2. In the slow autofocus process, the system takes time and consumes energy.
3. The mechanical noise in the autofocus process is relatively large.
4). In the autofocus process, a loss of synchronization occurs due to external load fluctuations, and compensation by feedback parameters after digital signal processing is required.

  When a linear magnetic actuator is used as an actuator of an autofocus system, the linear magnetic actuator is easily affected by load fluctuations, and a desired focus position cannot be achieved accurately. The main load fluctuations of the actuator (or motor) of the autofocus system are gravity and rocking (stagger stagger). For example, when the actuator of the autofocus system is horizontally operated, the output change of the actuator is necessarily different from that when the actuator of the autofocus system is vertically operated. Therefore, when the same control force is used for the position movement amount control of the linear motor in different load situations in the horizontal direction and the vertical direction, the accurate focus position cannot be reached. In order to solve the above-described problem of different load forces in the horizontal and vertical directions caused by gravity, the conventional solution techniques include the following.

  U.S. Pat. No. 5,838,374 (Applicant Sanyo) discloses an autofocus camera that provides compensation for changes in the external force load of a linear motor. However, Sanyo's compensation for loading is based on Newtonian laws of mechanics. Accordingly, when the camera is at a different posture angle, the linear motor that controls the autofocus is affected differently by the gravitational force, so that the result of the movement is not a desired setting command. In addition, Sanyo's camera can predict the horizontal state of the linear motor designed in advance through preliminary calculations and experimental results, move the motor by a predetermined distance, and output voltage value and position movement amount. It exhibits a linear relationship. Therefore, through the calculation of position feedback signal and Newtonian mechanics, the amount of error in position movement is used to determine the magnitude of the load force and to increase or decrease the voltage bias value that drives the motor. It is possible to compensate for fluctuations in the external gravity load of the motor.

  In US Pat. No. 5,057,859 (Olympus), the motor position detection uses a pulse generator as an encoder to generate a pulse signal, and converts the counted pulse value into an actual position movement amount. However, Olympus cannot provide a compensation mechanism during load force fluctuations.

  Further, in US Pat. No. 5,325,145 (Applicant: Canon), the focusing process achieves a focusing operation through three lenses. Based on the results of image analysis, the degree of complete focus is judged, and the three focus motors are moved at three different speeds (ie, high speed, medium speed, and low speed) so that each lens can move to the correct focus position. To do. However, Canon, like Olympus, cannot provide a compensation mechanism when the load force fluctuates.

  The above-mentioned Sanyo can compensate for the external load force fluctuation of the motor, but cannot provide a compensation mechanism for the load force fluctuation caused by the swing (stagger stagger). Moreover, the precondition that Sanyo realizes is the position movement amount of the motor movement, and the relationship between the speed and the driving voltage is sufficiently linear. However, in practice, it is difficult to design and manufacture an element that can achieve such a requirement. Therefore, solving the problem of the influence of the fluctuation of the load force due to the above-mentioned swing (stagger stagger) on the focus is the most serious problem that the industry currently faces. In addition, the industry is still seeing how high speed focus can be effectively compensated for load fluctuations by using linear actuators and combining load fluctuation compensation control methods without increasing hardware costs. It is the most serious challenge facing. Therefore, there is a need to provide an autofocus system device that can compensate for load fluctuations and can focus accurately at high speed.

  SUMMARY OF THE INVENTION Therefore, a main object of the present invention is to provide an autofocus system apparatus that can compensate for load fluctuations and can perform high-speed and accurate focusing. This autofocus system apparatus achieves position control that compensates for load force fluctuation by using a linear actuator and combining a load fluctuation compensation control method and monitoring and controlling the speed and position change amount of the actuator.

Another object of the present invention is to provide an autofocus system device that provides compensation control with respect to fluctuations in load force of a stagger.
In order to achieve the above object, according to an embodiment of the present invention, a lens focus is controlled using a load variation compensation control method, and a high speed focus is achieved using a linear actuator as a carrier. Subsequent load fluctuation compensation program code can be reduced and written to the read-only memory in the central processing unit of the system, and the reference model used during the load fluctuation compensation control is a complex s region ( s-domain), the input / output results are created in advance in a read-only memory in the central processing unit of the system, and the table search method is used. Thus, it is possible to effectively reduce the calculation amount and achieve a good compensation control effect.

A further object of the present invention is to provide a fast and accurate autofocus method.
To achieve this object, according to one embodiment of the present invention, a magnetoresistive sensor is used to detect a magnetic field change of a linear magnet bar generated by a linear actuator, and the magnetic field change is subsequently detected by a central processing unit. Generating a position signal corresponding to the linear actuator by a position calculation method; generating a position command corresponding to the position of the linear actuator using an image digital signal processor; using a position controller; Determining a primitive control voltage of a horizontal attitude of the linear actuator based on the position command and receiving the position command; using a position differentiator, which converts the position signal into the linear actuator. Used to convert to an actual speed signal; using a reference model converter, Using a reference model characteristic of the linear actuator built in the read-only memory to convert the input linear actuator control voltage to a speed at which the corresponding movable lens carrier can be moved; Comparing a speed signal output from the reference model converter with an actual speed signal generated by the position differentiator by using a comparator to generate one speed difference signal; using a load fluctuation compensator; The compensation control voltage is used to determine the compensation control voltage based on the speed difference value output from the speed comparator, and the compensation control voltage and the primitive control voltage generated by the position controller are input to the adder and added together. And is transmitted to a driver of the linear actuator to adjust the speed of the linear actuator.

  In addition, the load variation compensation control method used by the present invention generates a control voltage that can correct the load force variation based on the difference in speed variation. Therefore, the present invention can not only compensate for the influence of gravity, but also can compensate for load force fluctuations other than gravity, and can focus accurately at high speed.

  Still another object of the present invention is to provide a load variation compensation control method, and the principle that it uses is that the amount of change in the speed of the linear actuator exhibits a linear relationship with the load variation present outside. The fluctuation amount of the external load can be accurately known from the speed change amount, and the fluctuation of the external load is compensated based on the speed change amount of the linear actuator.

The autofocus system apparatus and method of the present invention have the following advantages over the prior art.
1. The present invention can provide an autofocus system device that provides compensation control for load force fluctuation of a stagger, which not only can provide compensation for load fluctuation caused by gravity, and Because it provides compensation for load fluctuations caused by external perturbation or stagger, it not only provides compensation for load fluctuations caused by gravity compared to the prior art, but also external Since the load fluctuation caused by the perturbation (or fluctuation) is compensated, the effect can be remarkably enhanced as compared with the prior art.
2. The autofocus system device of the present invention not only eliminates the drawbacks of known stepping motors, but also improves actuator efficiency, shortens autofocus time, and reduces battery electrical energy consumption. Can increase the service life compared to the prior art.
The present invention performs compensation control on an autofocus system that can compensate for load fluctuations and achieves a high-speed and accurate autofocus effect. The linear actuator of the present invention itself has a small volume and a structure. In addition to having the advantage of being simple, compensation control for, for example, oscillation other than gravity can be performed, and the difference in speed change amount can be achieved by utilizing the fact that the speed change amount and the external load have linear characteristics. In contrast, a new control voltage can be generated to compensate for load force fluctuations and achieve fast and accurate focus.

The best mode for carrying out the present invention will be described below with reference to the drawings.
Based on the law of Newtonian mechanics, if the linear actuator is influenced by the external load F _LOAD and the output of the linear actuator is F and the frictional force is zero (0), the net output of the linear actuator is These are expressed by Equation (1) and Equation (2).

  In the equation, M represents the weight of the linear actuator, a represents the acceleration of the linear actuator, Δν represents the speed change amount in Δt time, and V represents the operating voltage of the linear actuator. (1) can be modified to the following formula (3).

In Formula (3), since M, F, and Δt are all fixed values, Δν and F _LOAD Δ indicate a linear relationship. Therefore, the present invention compensates for fluctuations in the external load based on the speed change amount of the linear actuator.

FIG. 1 is a hardware configuration diagram of an autofocus system apparatus according to the present invention.
In FIG. 1, an autofocus system device includes a central processing unit (CPU) (14), two or more analog / digital converters (A / D converters) (13), and a lead having a capacity of 60 KBytes, for example. An only memory (ROM) (15) and, for example, a random access memory (RAM) (16) having a capacity of 1 KBytes are included. The driver (11) of the linear actuator (9) can receive digital data and control commands output from the central processing unit (CPU) (14) on the one hand via a serial transmission interface. On the other hand, different drive voltages are generated based on the received data and control commands and supplied to the linear actuator (9).
When the linear actuator (9) moves, the magnetoresistive encoder detects the magnetic field change of the linear magnet bar (6) using the magnetoresistive sensor (MR sensor) (7), and the two phase differences are detected. A 90 degree positive cosine magnetic signal (ie, sine and cosine) is generated and sent to an active low-pass filter (10) via a flexible printed circuit (FPC) (8) for signal noise. Then, the voltage level is adjusted to a range that can be received by the subsequent analog / digital converter (A / D converter) (13) via the signal amplifier (12). Finally, the obtained noiseless signal is output again to the central processing unit (CPU) (14) by the analog / digital converter (A / D converter) (13), and the linear actuator ( The position of 9) can be calculated accurately.

Please refer to FIG. 2 showing the block diagram of the present invention at the same time. The position command d ^{* of the} image digital signal processor (17) is sent to the position controller (20), and the position controller (20) is inside the central processing unit (CPU) (14) (as shown in FIG. 1). First, a primitive control voltage command V when the actuator is horizontal is determined through a two-stage proportional integration calculation method. At this time, if the external load is not in on the linear actuator (9) above or mobile lens carrier (1), since no correcting the original control voltage command V by the feedback compensation voltage V _e, the input control voltage instruction V ^* Is equal to the primitive control voltage command V.
Next, the pulse width modulation signal converter (22) converts the input control voltage command V ^* into a drive voltage command V _COM necessary for appropriate pulse width modulation control and an appropriate pulse width duty cycle command DT _COM . These two commands are sent again to the programmable motor driver (11) of the linear actuator (9), and finally a control voltage of pulse width modulation PWM is generated and provided to the linear actuator (9). Accordingly, the linear actuator (9) shown in FIG. 1 moves linearly in the yoke (5) along the guide rod (3) together with the movable lens carrier (1).

The present invention uses load fluctuation compensation as a theoretical basis. That is, the response characteristics of the reference model of the linear actuator (that is, the input primitive control voltage command V and the speed change amount Δνe are in direct proportion) through the computer simulation and experiment in advance are read within the arithmetic control chip. A table is created in the only memory (ROM) (15) to configure the reference model converter (28).
Further, the actual speed ν of the linear actuator (9) is continuously fed back via the magnetoresistive sensor (MR sensor) (7) in the position differentiator (25), and based on the sampling time C _DATA. The difference is calculated and the actual speed ν of the actual linear actuator (9) is output.
This actual speed ν is obtained by referring to and integrating the corresponding speed change amount Δνe based on the primitive control voltage command V output from the reference model converter (28) of the speed response characteristic of the built-in linear actuator reference model. And is subtracted by the central processing unit (CPU) (14) inside the comparator (26). In practice, this comparator (26) is essentially a subtractor. When there variation in the external load T _ext (t) together with a linear actuator (9) is movable lens carrier (1), since the difference value e _v after the subtraction calculation becomes a constant value, the load fluctuation compensation device (27 ) To generate different levels of compensation control command V _e based on the magnitude of the difference value e _v , and then add the compensation control command V _e and the primitive control voltage command V (21) by An input control voltage command V ^* with a set of compensation characteristics is generated to dynamically compensate for the speed difference caused by the external load T _ext (t).

In order to improve the use efficiency of electric energy, the input control voltage command V ^* is subjected to high-speed calculation inside the central processing unit (CPU) (14) via the pulse width modulation signal converter (22) and appropriate pulse width modulation. Determine the drive voltage command V _COM required for control and the appropriate pulse width duty cycle command DT _COM , and these two commands are the programmable motor driver (11) of the linear actuator (9) that receives the serial digital data input Send to. Thus, the compensation control mechanism of the present invention can not only modulate the effects caused by gravity load fluctuations, but can also compensate for external perturbation (or rocking) inputs.

In FIG. 3, a characteristic curve as a basis of an arithmetic method in which the input control voltage command V ^* is converted into a drive voltage command V _COM required for pulse width modulation control and an appropriate pulse width duty cycle command DT _COM is shown. The solid line (voltage V ₁ ) represents the primitive control voltage, and the dotted line (voltage V ₂ ) represents the compensation control voltage command.
Further, based on the above-described theoretical experiment, when the entire experimental platform is first leveled and the time axis is 70 milliseconds, as shown in FIG. 4A, the external instantaneous perturbation (or oscillation) load is a linear actuator ( 9) Added above. That is, when the time axis is lower than 70 milliseconds, T _ext (t) −T (t) = 0 because the external load T _ext (t) is _unchanged and gravity T (t). Is 70 ms, there is already an instantaneous perturbation in addition to gravity. As shown in FIG. 4A again, when the time axis is 70 milliseconds, the embodiment of the present invention (see FIGS. 1 and 2) generates a compensation control voltage to generate an external perturbation on the linear actuator (9) ( (Or rocking) compensate for input. FIG. 4B shows the relationship between the external load fluctuation and the time axis according to the embodiment of the present invention.

  As described above, preferred embodiments of the present invention have been disclosed. However, these embodiments are not intended to limit the present invention, and the technical idea of the present invention can be easily understood by those skilled in the art. Therefore, the scope of patent protection should be determined based on the scope of the claims and their equivalents, since appropriate changes and modifications can be naturally made to these embodiments.

1 is a hardware configuration diagram showing an autofocus system device according to an embodiment of the present invention. 1 is a configuration block diagram showing an autofocus system device according to an embodiment of the present invention. Explanatory drawing which shows the characteristic curve based on the calculation method by which an input control voltage is converted into the drive voltage command required for pulse width modulation control, and a suitable pulse width duty cycle command. Explanatory drawing which shows the relationship between the compensation control voltage and time axis concerning embodiment of this invention. Explanatory drawing which shows the relationship between the external load fluctuation | variation concerning this Embodiment, and a time-axis.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mobile lens carrier 2 Sleeve 3 Guide rod 5 Yoke 6 Magnet bar 7 Magnetoresistive sensor 8 Flexible printed circuit 9 Linear actuator 10 Active low-pass filter 12 Signal amplifier 13 Two or more analog / digital (A / D) Converter 14 Central processing unit (CPU)
15 Read-only memory (ROM)
16 Random access memory (RAM)
17 Image digital signal processor

Claims (9)

A linear actuator over that used to drive the movable lens carrier for fixedly supporting the lens;
An image digital signal processor used to generate the position command corresponding to the position of the linear actuator;
Which receives the position command, a position controller for determining the primitive control voltage of the horizontal position of the linear actuator based on the position command;
Includes a magnetoresistive encoder, a position differentiator for converting the position signal generated by the magnetoresistive encoder to the actual speed signal of said linear actuator;
The reference model characteristics created from the original control voltage and the speed variation of the linear actuator of the linear actuator, a source control voltage of linear actuators, this query the speed variation of the corresponding linear actuator integrating this a reference model converter you outputs an output value was collected using;
By comparing the actual speed of the raw made the linear actuator by the position differentiator and output values of the reference model converter, and one that generates a speed difference signal comparing unit;
The compensation control voltage determined based on the speed difference value to the output of the previous SL ratio較器adds to enter into both the adder and a source control voltage generated by the said compensation control voltage and the position controller, wherein the linear actuator a load fluctuation compensator and transmitted to the driver to adjust the speed of the linear actuator,
Including auto focus system device.   Furthermore, a pulse width modulation signal converter is included, and the pulse width modulation signal converter converts the combined compensation control voltage and the original control voltage into a drive voltage command and an appropriate pulse width duty cycle command required by the pulse width modulation signal. 2. The autofocus system device according to claim 1, wherein the autofocus system device is used to convert and the two commands are subsequently input to a driver of the linear actuator. Further , the magnetoresistive encoder includes a magnetoresistive sensor used to sense a magnetic field change of the linear magnet bar generated by the movement of the linear actuator, and the magnetoresistive encoder corresponds to the linear actuator according to a position calculation method of a central processing unit. The autofocus system device according to claim 1, which generates a position signal. Autofocus system according to claim 1 before Symbol ratio較器is substantially subtractor. Wherein the position controller, said position command received, the autofocus system according to 請 Motomeko 1 you calculated as the original control voltage during a horizontal posture before Symbol linear actuator. Detecting a magnetic field change of a linear magnet bar generated by a linear actuator using a magnetoresistive sensor, and the magnetic field change subsequently generates a position signal of the linear actuator by a position calculation method of a central processing unit;
Generating a position command corresponding to the position of the linear actuator using an image digital signal processor;
Using a position controller to determine a primitive control voltage of the horizontal attitude of the linear actuator based on and used to receive the position command;
Using the position differentiator to convert the position signal of the linear actuator to the actual speed signal of said linear actuator;
The reference model characteristics made from the speed variation of the original control voltage and the linear actuator using the reference model converter linear actuator, the control voltage of the linear actuator, query the speed variation of the corresponding linear actuator to And output the output value obtained by integrating this ;
Using the ratio較器compares the actual speed of the linear actuator to produce an output value and a position differentiator to the output of the reference model converter to generate one of the speed difference signal;
A load fluctuation compensator is used to determine a compensation control voltage based on the speed difference value output from the speed comparator, and both the compensation control voltage and the original control voltage generated by the position controller are input to the adder. And adding to the linear actuator driver to adjust the speed of the linear actuator.   The method further includes the step of using a pulse width modulation signal converter, which converts the combined compensation control voltage and the original control voltage into a drive voltage command required by the pulse width modulation signal and an appropriate pulse width duty cycle command. The autofocus method according to claim 6, wherein the two commands are then input to a driver of the linear actuator.   The autofocus method according to claim 6, wherein in the step of using the speed comparator, the speed comparator is substantially a subtractor.   The autofocus method according to claim 6, wherein the position command received by the position controller is used as a primitive control voltage when the linear actuator is in a horizontal posture during the step of using the position controller.

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