TWI573456B - Optical image stabilization device - Google Patents

Description

Optical image stabilization device

This invention relates to optical images, and more particularly to optical image stabilization devices.

In addition to digital cameras, more and more handheld electronic devices now have built-in camera functions, such as mobile phones, tablets, and the like. However, the camera module of mobile phones and tablets does not have the same amount of light as the digital camera, so it is necessary to use a better anti-shake mechanism to get better photos and/or video quality. With the popularity of mobile phones and tablets and the increasingly fierce market competition, it is necessary to rely on high-performance and low-cost optical image stabilization (OIS) solutions to bring more electronic devices such as mobile phones and tablets. Competitive advantages.

An object of the present invention is to provide an optical image stabilization device and a lens adjustment method based on the optical image stabilization device, which utilizes an easy-to-implement circuit to reduce the influence of vibration during shooting to improve image quality.

The invention discloses an optical image stabilization device, which is applied to a camera module. One lens of the camera module is driven by a motor, and the camera module includes a driving sensor for sensing the driving force of the motor. And a vibration sensor including a vibration level detecting the camera module, the optical image stabilization device comprising: a filter for calculating a time change of driving the sensing signal by one of the driving inductors by using a first adder The mapping circuit is configured to store a mapping table corresponding to a first angular offset of the driving sensing signal; a conversion unit coupled to the mapping circuit for using the mapping table according to the mapping table The driving induction signal is converted into the first angular offset; an integrator is used to integrate the vibration sensing signal of one of the vibration sensors to generate a second angular offset; and a second adder coupled The integrator and the conversion unit are configured to calculate a difference between the first angular offset and the second angular offset; and a motor driving circuit coupled to the second adder One basis for the difference to be used to control the variable control of the motor driving amount of the lens; wherein the first adder and the second adder circuit adding a common line.

The optical image stabilization device of the present invention and the lens adjustment method based on the optical image stabilization device achieve the effect of optical image stabilization by an easy-to-implement circuit, and achieve the effect of the shared circuit by controlling the time of each component. Save circuit costs.

The features, implementations, and effects of the present invention are described in detail below with reference to the drawings.

The technical terms of the following descriptions refer to the idioms in the technical field, and some of the terms are explained or defined in the specification, and the explanation of the terms is based on the description or definition of the specification.

The disclosure of the present invention includes an optical image stabilization device and a lens adjustment method based on the optical image stabilization device. Since some of the components included in the optical image stabilization device of the present invention may be known components alone, the following description will be given for details of known components without affecting the full disclosure and feasibility of the device invention. Abridged. In addition, the lens adjustment method based on the optical image stabilization device of the present invention may be in the form of a soft body and/or a firmware, and the description of the following method invention will be emphasized without affecting the full disclosure and feasibility of the method invention. In the step content instead of hardware.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a functional block diagram of one embodiment of an optical anti-shake circuit of the present invention. One of the functions of the optical image stabilization device 10 (or optical anti-shake circuit) is to control the voice coil motor 40 according to the vibration sensing signal generated by the vibration sensor 30 (reaction to the vibration degree of the camera module). Adjust the position of the lens to compensate for lens shift caused by camera module vibration. The vibration sensor 30 can be, for example, a gyroscope that senses the vibration of the camera module to produce an angular velocity signal. The integrator 130 performs an integral operation on the angular velocity signal after the digitization (converted by the ADC 120) to obtain an angular offset corresponding to the degree of vibration of the camera module. _Gyro ; on the other hand, the driving sensor 50 (for example, a Hall sensor) induces a change in the magnetic field generated by the voice coil motor 40 (reacting the amount of driving of the voice coil motor 40 to the lens, that is, the amount of displacement of the reaction lens) Driving the sensing signal S', the driving sensing signal S' is converted into a digital format by the ADC 190 (driving the sensing signal S), filtering the noise through the filter 180, and then converting the mapping table by the conversion unit 160 with reference to the mapping circuit 170 Angle offset corresponding to the lens displacement _Hall . The adder 135 calculates the angular offset _Gyro and angular offset _Hall difference , a proportional integral and differential (PL) controller 140 is further based on the difference Controlling the magnitude (eg, current magnitude) of the drive signal V when the motor drive circuit 150 drives the voice coil motor 40, causing the voice coil motor 40 to move the lens to the target position in a progressive manner to avoid the lens moving in a large amount in one position. Produces significant damping. Please note that due to the difference Or angular offset _{The gyro} is generated according to the vibration sensing signal of the vibration sensor 30, so it can be regarded as the vibration compensation signal in the optical image stabilization device 10; in addition, in some cases, if the lens is not swaying during the movement process, the sloshing is not obvious. The optical image stabilization device 10 can omit the proportional integral derivative controller 140. In this case, the motor drive circuit 150 is directly coupled to the adder 135 and directly depends on the difference. To drive the voice coil motor 40.

The driving sensor 50 is susceptible to an operating environment such as temperature, so that the driving sensing signal S has a large amount of noise, and one of the purposes of the filter 180 is to filter out such noise. 2 is a partial circuit diagram of an embodiment of a filter of the present invention, the purpose of which is to filter out drastic changes in signals caused by noise in continuous signals. The three delay units 181, 182, and 183 each delay the signal by a clock period T of one system, and the adder 184 is coupled to the three delay units to calculate the difference between the signal S[k-1] and the signal S[k-2]. And the difference between the signal S[k] and S[k-1] (k is an integer representing the time indicator): (1) (2) After the comparator 185 will versus Absolute difference Compare with a threshold if versus If the absolute difference is greater than the critical value, it means that the value of the signal S[k-1] is too far from the value of the signal S[k] and the value of the signal S[k-2] (ie, the signal S[k-1] may be For the noise, the comparator 185 outputs a control signal, so that the multiplexer 186 selects the signal S[k-2] output to filter out the noise signal S[k-1]; versus The absolute difference is not greater than the threshold, and the comparator 185 outputs a control signal to cause the multiplexer 186 to select the signal S[k-1] output. Therefore, the filter 180 compares the three consecutive signals after the analog-to-digital conversion of the driving inductor 50, wherein only the adder 184 is used for addition and subtraction and the comparator 185 is used for comparison, without using a multiplier or the like. Circuits occupying circuit area and computationally time-consuming, thus reducing the cost of the filter 180 and increasing efficiency.

The driving induction signal S of the driving sensor 50 is filtered to become a filtering signal S_F, and the filtering signal S_F is converted into an angular offset by the conversion unit 160 by referring to the mapping table of the mapping circuit 170. _Hall . Drive sensor signal S and angular offset of drive sensor 50 The correspondence of the _hall is pre-measured and stored in the mapping table of the mapping circuit 170, and the conversion unit 160 refers to the mapping table and uses the interpolation method and/or the extrapolation method to convert the driving sensing signal S into a corresponding angular offset. _Hall . For example, the converting unit 160 first determines that the filtered signal S_F is located in the interval [S _map , S _map+1 ] of the mapping circuit 170, wherein S _map and S _{map +1} respectively correspond to the angular offset _Map and _Map+1 , and the slope of this interval is ratio _map ; then the angular offset .

However, sometimes the output of the driving sensor 50 is excessively affected by environmental factors such as temperature, and a large range of unreasonable output values are generated in the driving sensing signal S. At this time, the filter 180 can refer to the driving signal of the motor driving circuit 150. The angular offset corresponding to V is used to filter out this wide range of unreasonable output values. When the optical image stabilization device 10 reads the driving sensing signal S of the driving sensor 50, the multiplexers 165 and 175 select the filtering signal S_F and the corresponding mapping table according to the control signal Ctrl (issued by the processing unit 110) to cause the conversion unit 160 to Get the angular offset by conversion _Hall , then the proportional integral derivative controller 140 can control the motor driving circuit 150 according to the above mechanism; on the other hand, when the motor driving circuit 150 drives the voice coil motor 40, the multiplexers 165 and 175 select the driving signal V according to the control signal Ctrl. And the corresponding mapping table causes the converting unit 160 to convert the signal v2h, and the filter 180 refers to the signal v2h to filter out the unreasonable output value of the signal S. That is to say, the optical image stabilization device 10 can use the same conversion unit 160 to convert the driving induction signal S of the driving sensor 50 and the driving signal V of the motor driving circuit 150.

3 is a partial circuit diagram of an embodiment of a filter of the present invention, the purpose of which is to filter out a wide range of unreasonable output values in the drive sense signal S of the drive inductor 50. The signal v2h[k] is a signal after the drive signal V is converted by the conversion unit 160. The delayed signal S[K] and the signal v2h[k] are simultaneously input to the adder 188, and the adder 188 calculates the absolute difference as . The comparator 189 compares the absolute difference with the preset value. If the absolute difference is greater than the preset value, indicating that the drive sensing signal S at this time has an unreasonable output value, the filter 180 skips the section and is unreasonable. The output is reversed. If the absolute difference is not greater than the preset value, indicating that the drive sensing signal S at this time is a reasonable output value, the filter 180 can further filter the driving sensing signal S (using the Filter circuit).

A detailed circuit diagram of the proportional-integral-derivative controller 140 is shown in FIG. Error amount e (ie the difference in the aforementioned angular offset) After the delay of the three delay units 141, 142, and 143, the delayed error amount e is multiplied by the PID coefficient (stored in the register 147) by the multiplier 145, and the adder 146 outputs the output of the multiplier 145. Adding to the previous control variable u[k-1], the last control variable u[k] is as follows: (3) The motor drive circuit 150 adjusts the magnitude of its drive signal V (ie, the driving force) according to the control variable u, wherein the PID coefficients k1, k2, and k3 and the original PID coefficients (k _{p ,} k _i , k _d ) have the following Conversion relationship: (4) The above conversion relationship can be derived from the original PID formula. The most basic principle formula of PID is expressed as follows: (5) After converting equation (5) to discrete time mode, you can get: (6) Adjust equation (6) as follows: (7) Applying the conversion relationship of equation (4) to equation (7) and rearranging, equation (3) can be obtained. The operation is performed by using the converted PID coefficients k1, k2, and k3, so that the proportional-integral-derivative controller 140 of the present invention can be completed by the simple circuit shown in FIG. 4, and complicated integral and differential operations can be eliminated.

In summary, the optical image stabilization device 10 of the present invention has the characteristics of simple circuit, and through the appropriate timing design, the adders 135, 184, 188, and 146 can share the same addition circuit, and the comparators 185 and 189 can also share The same comparison circuit. In one embodiment, the multiplying circuit used by the adding circuit, the comparing circuit, and the multiplier 145 may be a 16-bit digital circuit, which can complete the functions required by the optical image stabilization device 10, and The filter 180 completed in Fig. 3 has excellent effects although it uses simple circuits and components. Therefore, the optical image stabilization device 10 of the present invention has the advantages of low cost and high performance.

Figure 7 is a timing diagram of the addition circuit, the multiplication circuit, and the comparison circuit of the present invention used by the components of the optical anti-shake circuit. The vertical axis represents time, and each time unit is one clock cycle of the system. At time T1, the converting unit 160 (using the adding circuit and the multiplying circuit) converts the driving signal V into a signal v2h according to the corresponding mapping table in the mapping circuit 170; at time T2, the filter 180 (using the adding circuit and the comparing circuit) Driving the sensing signal S to perform filtering to obtain the filtered signal S_F; at time T3, the converting unit 160 (using the adding circuit and the multiplying circuit) converts the filtered signal S_F into an angular offset according to the corresponding mapping table in the mapping circuit 170. _Hall ; at time T4, adder 135 (using the addition circuit) calculates the angular offset _Gyro and angular offset _Hall difference At time T5, the PID controller 140 (using the adder circuit and the multiplying circuit) is based on the difference Controlling the magnitude of the driving signal V when the motor drive circuit 150 drives the voice coil motor 40; and at time T6, the converting unit 160 (using the adding circuit and the multiplying circuit) again converts the driving signal V according to the corresponding mapping table in the mapping circuit 170 It is the signal v2h as a reference for the next filter of the filter 180. The optical anti-shake circuit detects and compensates the x-axis at time T1~T6, and detects and compensates the y-axis and z-axis respectively at the next time T7~T12 and time T13~T18. The above description of time T1~T6. The times T19 and T20 are the time for waiting for the voice coil motor 40 to react. When the voice coil motor 40 is completed, the filter 180 can filter the drive sensing signal S again according to the signal v2h obtained at the time T6. Then repeat the above steps.

Another function of the optical image stabilization device 10 is to analyze the output image of the image sensor 20 to know the assembly error of the lens of the camera module after assembly. Such assembly errors may cause image shift or blurry. The assembly error can be known and stored in advance, and the assembly error can be offset by controlling the displacement of the lens after photographing, so that even if the lens assembly is not perfect, the camera module can still capture a clear image. FIG. 5 is a flow chart of an embodiment of the optical image stabilization device 10 of the present invention for detecting and recording an assembly error of a camera module. At the beginning of the process (for example, the camera module has just completed assembly), since there is no analysis result, step S520 is skipped directly to step S520. In step S520, the camera module first captures an image of the reference object through the lens and the image sensor 20. The reference object has a positioning mark, so that the processing unit 110 can analyze the position and the sharpness of the positioning mark on the reference object to generate an analysis result (step S530), and according to the analysis result (for example, whether the image is clear enough, whether the position of the image is clear or not) Correct, etc.) to determine whether the position of the lens needs to be adjusted (step S540). If the analysis result indicates that the position of the lens has not been adjusted to the optimum position (YES in step S540), the processing unit 110 controls the motor drive circuit 150 in accordance with the analysis result to drive the voice coil motor 40 to adjust the lens (step S510). In this way, steps S510 to S540 are repeatedly performed. Finally, when the image of the reference object is clear enough (NO in step S540), the amount of adjustment in each axial direction of the lens during the adjustment of steps S510 to S540 (for example, x, y, The adjustment amount in the z direction is , , , wherein one of the x, y, and z directions is the focal length direction, and then the processing unit 110 stores the obtained adjustment amount in the memory 115 (step S550). The memory 115 can be a non-volatile memory component, such as a flash memory, and the adjustments are not lost due to powering down of the optical image stabilization device 10. Then, when the camera module captures the image, the motor drive circuit 150 drives the voice coil motor 40, that is, the motor drive, with reference to the lens adjustment amount in the memory 115 in addition to the control variable u of the proportional integral derivative controller 140. The circuit 150 further adjusts the driving amount of the voice coil motor 40 to the lens in accordance with the lens adjustment amount (step S560). In this way, the lens can be moved to a better shooting position to overcome the assembly error of the lens, and at the same time achieve the effect of optical anti-shake.

However, there are many factors that cause the camera to blur when the camera module is shooting. One of the reasons is because the target being shot is moving. Therefore, another function of the optical image stabilization device 10 is to analyze the output image of the image sensor 20 to know the moving state of the target, and to perform corresponding compensation according to the moving state of the target. FIG. 6 is a flow chart of an embodiment of the present invention for offset compensation of a lens according to displacement information of a target. As shown in the figure, when the camera module is about to shoot the target, the lens is now aimed at the target and the image sensor 20 has generated an image of the target (step S610). Afterwards, the processing unit 110 analyzes the image of the target object and generates angular velocity information corresponding to the displacement of the target object (that is, the degree of displacement of the target object is converted into the vibration degree of the camera module) (step S620), and the angular velocity information represents the target object during the shooting process. The state of movement in . Then, the integrator 130 integrates the angular velocity information to obtain an angular offset corresponding to the target displacement, and the proportional integral derivative controller 140 determines the difference between the angular offset and the angular offset of the driving sensor 50. The lens shift compensation amount is determined (step S630). Then, the motor driving circuit 150 drives the voice coil motor 40 to adjust the lens according to the lens offset compensation amount, that is, the motor driving circuit 150 further adjusts the driving amount of the voice coil motor 40 to the lens according to the lens shift compensation amount (step S640). Make the offset trend of the lens consistent with the displacement trend of the target to get a clearer image of the target. The flow of FIG. 6 can be performed simultaneously with the aforementioned optical anti-shake mechanism of the optical image stabilization device 10 for better image quality.

The optical image stabilization device 10 described above is applied to a camera module. The camera module includes an image sensor 20, a vibration sensor 30, a voice coil motor 40, and a drive sensor 50. The optical image stabilization device 10 can be part of the camera module or be independent of the camera module. It is noted that the shapes, dimensions, proportions, and order of steps of the elements are merely illustrative, and are intended to be used by those of ordinary skill in the art to understand the invention and not to limit the invention. In addition, the foregoing embodiment is exemplified by a camera module of a handheld device, which is not a limitation of the present invention. Those skilled in the art can appropriately apply the present invention to other types of image capturing devices according to the disclosure of the present invention. .

Although the embodiments of the present invention are described above, the embodiments are not intended to limit the present invention, and those skilled in the art can change the technical features of the present invention according to the explicit or implicit contents of the present invention. Such variations are all within the scope of patent protection sought by the present invention. In other words, the scope of patent protection of the present invention is defined by the scope of the patent application of the specification.

10‧‧‧Optical image stabilization device
20‧‧‧Image sensor
30‧‧‧Vibration sensor
40‧‧‧ voice coil motor
50‧‧‧Drive sensor
110‧‧‧Processing unit
115‧‧‧ memory
120, 190‧‧‧ analog digital converter
130‧‧‧ integrator
135, 184, 188, 146‧‧ ‧ adders
140‧‧‧Proportional Integral Derivative Controller
150‧‧‧Motor drive circuit
160‧‧‧Conversion unit
165, 175, 186‧‧‧ multiplexers
170‧‧‧ mapping circuit
180‧‧‧ filter
141, 142, 143, 144, 181, 182, 183, 187‧‧‧ delay units
185, 189‧‧‧ comparator
145‧‧‧Multiplier
147‧‧‧ 存存器
S510 ~ S560, S610 ~ S640‧ ‧ steps

1 is a functional block diagram of an embodiment of an optical anti-shake circuit of the present invention; [Fig. 2] is a partial circuit diagram of an embodiment of a filter of the present invention; [Fig. 3] A partial circuit diagram of an embodiment; [Fig. 4] is a detailed circuit diagram of the proportional integral derivative controller 140 of the present invention; [Fig. 5] is an implementation of the assembly error of detecting and recording the camera module of the optical image stabilization device 10 of the present invention. [FIG. 6] is a flowchart of an embodiment of the present invention for offset compensation of a lens according to displacement information of a target; and [FIG. 7] is an addition circuit, a multiplication circuit, and a comparison circuit of the present invention. Timing diagram used by the various components of the optical anti-shake circuit.

10‧‧‧Optical image stabilization device

20‧‧‧Image sensor

30‧‧‧Vibration sensor

40‧‧‧ voice coil motor

50‧‧‧Drive sensor

110‧‧‧Processing unit

115‧‧‧ memory

120, 190‧‧‧ analog digital converter

130‧‧‧ integrator

135‧‧‧Adder

140‧‧‧Proportional Integral Derivative Controller

150‧‧‧Motor drive circuit

160‧‧‧Conversion unit

165, 175‧‧‧ multiplexers

170‧‧‧ mapping circuit

180‧‧‧ filter

Claims (6)

An optical image stabilization device is applied to a camera module, wherein a lens of the camera module is driven by a motor, the camera module includes a driving sensor for sensing the driving force of the motor, and including Detecting a vibration sensor of the camera module, the optical image stabilization device includes: a filter, wherein a first adder is used to calculate a change in time of driving the sensing signal by one of the driving inductors to Filtering the driving sensing signal; a mapping circuit for storing a mapping table of the driving sensing signal corresponding to a first angular offset; a converting unit coupled to the mapping circuit, configured to sense the driving according to the mapping table The signal is converted into the first angular offset; an integrator is used to integrate the vibration sensing signal of one of the vibration sensors to generate a second angular offset; and a second adder coupled to the integrator And the conversion unit is configured to calculate a difference between the first angular offset and the second angular offset; and a motor driving circuit coupled to the second adder for It should be one of the difference variables to control the motor controlling the drive amount of the lens; wherein the first adder and the second adder circuit adding a common line. The optical image stabilization device of claim 1, further comprising: a proportional integral derivative controller coupled to the second adder and the motor driving circuit for generating the control variable according to the difference. The optical image stabilization device of claim 1, wherein the conversion unit is further coupled to the motor driving circuit for converting a driving signal of the motor driving circuit into a reference signal, wherein the filter further utilizes a The third adder calculates a difference between the driving sense signal and the reference signal to filter the driving sensing signal, and the third adding unit shares the adding circuit with the first adder and the second adder. The optical image stabilization device of claim 3, wherein the filter further comprises: a first comparator coupled to the third adder for using the difference between the driving sensing signal and the reference signal The absolute value is compared with a first preset value; and a second comparator is coupled to the first adder for using the absolute difference between the amount of change in the driving sense signal and the second pre- The value is compared for comparison; the first comparator and the second comparator share a comparison circuit. The optical image stabilization device of claim 1, wherein the camera module further comprises an image sensor for sensing an image from a reference object, the optical image stabilization device further comprising: a processing unit, The image sensor is coupled to analyze the image of the reference object to generate an adjustment amount for compensating the assembly error of the camera module; and a memory coupled to the processing unit and the motor driving circuit for The adjustment amount is stored; wherein the motor driving circuit further controls the driving amount of the motor to the lens according to the adjustment amount. The optical image stabilization device of claim 1, wherein the camera module further comprises an image sensor for sensing an image from a target, the optical image stabilization device further comprising: a processing unit, The image sensor and the motor driving circuit are coupled to analyze an image of the target object to generate an angular velocity information corresponding to the target displacement, and generate an offset compensation amount according to the angular velocity information; wherein the motor driving circuit further The amount of driving of the motor to the lens is controlled according to the offset compensation amount.