Automatically aligned focus mechanism with voice coil motor

Abstract

The present application provides an automatic alignment focusing structure with voice coil motors, which can be applied to a camera module. The voice coil motors of the focusing structure can push a circuit board to displace. The side of the circuit board opposite to each voice coil motor is provided with an image sensor. The image sensor can transmit the sensed information to an image processor to convert the information into corresponding image information. The image processor can calculate a flatness deviation value according to the image information and generate at least one displacement control information. Then, each voice coil motor pushes the circuit board to make the side of the circuit board together with the image sensor keep aligned and flat with a lens, and make the object image fall on the image sensor to complete focusing.

Description

Technical Field

[0001] The present application relates to a focusing structure, and more particularly to a focusing structure that automatically adjusts back focus using multiple voice coil motors. Background Art

[0002] With the rise of smartphones and the increasingly advanced lenses they come with, photography has become increasingly popular. In particular, the booming development of social networking sites has enabled people to document their lives with photos all the time. This has led many people to no longer be satisfied with just mobile phone cameras and to pursue various types of digital cameras, such as SLRs, mirrorless SLRs, and SLR-like cameras.

[0003] The current design trend in camera specifications is towards ultra-thin designs and high pixel counts, resulting in the continued miniaturization of camera modules. High-pixel camera modules often offer features like autofocus. Generally speaking, the imaging structure in a camera consists of at least a lens, shutter, and photosensitive element. The lens is composed of multiple lenses, and the lens's optical properties (e.g., focal length) also affect image quality. "Focus" ensures that the external image (or object image) falls precisely on the photosensitive element, resulting in a clear photo. The following is the formula for convex lens imaging:

[0004] 1 / u+1 / v=1 / f

[0005] Continuing from the above formula, u refers to the object distance, v refers to the image distance, and f refers to the focal length. Since the focal length of a lens can be determined in advance, simply knowing either the object distance or the image distance allows the remaining value to be calculated. This led to the development of active auto-focus technology, which uses an external rangefinder (such as a laser or infrared) to measure the object distance to achieve focus. However, adding a rangefinder increases the cost of the camera and does not effectively reduce its size. Therefore, passive auto-focus technology has emerged. This technology uses software algorithms to process the image and detect focus when high contrast (optimal clarity) is detected. This not only meets the trend of slim and compact digital camera designs, but also eliminates the cost of a rangefinder.

[0006] When a camera uses passive autofocus technology, a voice coil motor (VCM) is commonly used to move the lens until the image is clear (i.e., in focus). However, some camera devices have mechanical limitations that may restrict lens movement. In these cases, the aforementioned autofocus structure cannot be properly implemented, and the industry may even need to design complex mechanisms to meet focusing requirements. Summary of the Invention

[0007] To address the aforementioned issues, the inventors, drawing upon years of extensive practical experience in various design, processing, and manufacturing fields, and adhering to a spirit of continuous improvement, have, after years of diligent research and experimentation, finally developed the present invention, an automatic alignment focusing structure with a voice coil motor. The present invention is intended to provide users with a better user experience.

[0008] To solve the above technical problems, a technical solution adopted by the present application is to provide an automatic alignment focusing structure with voice coil motors, which can be applied to a camera module with an image processor. The focusing structure includes a substrate, a plurality of voice coil motors, a circuit board and an image sensor. Each voice coil motor is arranged on one side of the substrate and spaced apart from each other by a distance. The circuit board is located at one end of the plurality of voice coil motors and can be pushed and displaced by the plurality of voice coil motors. The image sensor is located on one side of the circuit board and can convert an optical signal projected onto the image sensor through a lens into an analog electrical signal. The image sensor can transmit the analog electrical signal to the image processor in the camera module, so that the image processor can calculate a flatness deviation value according to the image information after converting the analog electrical signal into corresponding image information, and generate at least one displacement control information corresponding to the flatness deviation value. That is, the image processor can be located in the camera module, and can obtain the analog electrical signal transmitted by the image sensor, and convert it into corresponding image information, and can calculate a flatness deviation value according to the image information, and generate at least one displacement control information corresponding to the flatness deviation value. Each voice coil motor can receive the displacement control information transmitted from the image processor and push the circuit board according to the displacement control information, so that one side of the circuit board and the image sensor can be aligned and flattened with the lens, and the object image can be focused on the image sensor to complete the focusing. In this way, the present application does not need to use expensive correction inclination equipment, but only needs to control the distance of each voice coil motor pushing the circuit board, so that the circuit board and the image sensor on it can be kept flat with the lens, so that the optical axis of the lens can be kept perpendicular to the circuit board (including image sensor).

[0009] Optionally, the image processor is provided with an original flatness value, and the displacement control information received by the voice coil motor is generated by the image processor according to the original flatness value and the flatness deviation value. That is, in the case of generating the image information by the image processor, the image processor will generate each displacement control information according to the original flatness value and the flatness deviation value.

[0010] Optionally, the focusing structure is provided with four voice coil motors, and the plurality of voice coil motors are respectively arranged near four corners of the circuit board.

[0011] Optionally, the image sensor is arranged in the central region of the circuit board.

[0012] Optionally, the image sensor is of CMOS specification.

[0013] Optionally, the voice coil motor can only push the circuit board in its own axial direction.

[0014] In order to further illustrate the purpose, technical features and effects of this application, a specific implementation method is given with reference to the accompanying drawings and described in detail as follows. However, the drawings provided are only for reference and explanation and are not used to limit this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is an exploded diagram of the focusing structure and lens of the present application;

[0016] Figure 2 It is a stereogram of the focusing structure of the present application;

[0017] Figure 3A is a side view of the voice coil motor of the present application without pushing the circuit board;

[0018] Figure 3B is a side view of the voice coil motor of the present application pushing the circuit board;

[0019] Figure 4 is a schematic diagram of the focusing structure, lens and shooting target of this application; and

[0020] Figure 5 It is a schematic diagram of the flatness value and flatness deviation value of the focus structure calculation of the present application. DETAILED DESCRIPTION

[0021] To further clarify the objectives, technical solutions, and advantages of this application, the following detailed description of the embodiments of the "auto-aligned focusing structure with a voice coil motor" disclosed in this application is provided with reference to the accompanying drawings. Those skilled in the art will appreciate the advantages and benefits of this application from the disclosure herein. This application may be implemented or applied through other different specific embodiments, and the details herein may be modified and altered based on different perspectives and applications without departing from the spirit of this application. It should be noted that the drawings herein are for illustrative purposes only and are not intended to be representations of actual dimensions. While examples of parameters with specific values ​​may be provided herein, it should be understood that the parameters do not need to be exactly equal to the corresponding values, but may be approximated to the corresponding values ​​within acceptable error tolerances or design constraints. Furthermore, unless otherwise specified or defined by the context, the terms "a," "the," and "said" herein include the plural.

[0022] It should be understood that, although the terms first, second, etc. can be used herein to describe various components or signals, these components or signals should not be limited by these terms. These terms are only used to distinguish one component from another. Furthermore, directional terms such as "upper", "lower", "front", "back", "left", "right", etc. mentioned in subsequent embodiments are only with reference to the directions of the drawings. Therefore, the directional terms used are used for illustration and not for limiting the scope of protection of the present application. In addition, the term "or" used herein can include any one or more combinations of the associated listed items.

[0023] Furthermore, the terms "substantially" or "approximately" and the like used herein can refer to a value or an average of values within a range of deviation that can be recognized or determined by those skilled in the art for a certain value, including a certain error that can be generated when the certain value is measured considering the limitations of the measurement system or device. For example, the value mentioned substantially can include ±5%, ±3%, ±1%, ±0.5%, ±0.1% or one or more standard deviation ranges of the certain value.

[0024] The present application is an automatic alignment focusing structure with voice coil motors, which is applied to a camera module. The lens used in the camera module is fixed by a mechanism and cannot be displaced. Therefore, the focusing structure of the present application uses automatic back focus adjustment (ABF). Please refer to FIGS. 1 and 2. In an embodiment, the focusing structure includes a substrate 11, a plurality of voice coil motors 12, a circuit board 13, an image sensor 14 and an image processor 15. The plurality of voice coil motors 12 can be arranged on one side of the substrate 11 and spaced apart from each other by a distance. Since the structure of the voice coil motor 12 is a known technology, it will not be described here. As long as each voice coil motor 12 can achieve the functions described later, it is called a voice coil motor 12 in the present application.

[0025] As mentioned above, please refer to FIGS. 3A and 3B. The circuit board 13 is located at one end of each voice coil motor 12 and can be displaced by each voice coil motor 12. For example, in the direction of FIG. 3B, the circuit board 13 is pushed up and down by the voice coil motor 12. In this embodiment, the voice coil motor 12 can only push the circuit board 13 up and down in the axial direction of the voice coil motor 12, and the number of voice coil motors 12 is four, which can be arranged near the four corners of the circuit board 13. However, this is not limited. In other embodiments of the present application, the number of voice coil motors 12 and the position of the corresponding circuit board 13 can be adjusted according to product requirements.

[0026] Referring again to Figures 1 and 2 , the image sensor 14 is located on the side of the circuit board 13 facing away from the voice coil motor 12, forming a sensor board with the circuit board 13. When light is projected onto the image sensor 14 through the lens 16, the image sensor 14 converts the light signal into an analog electrical signal. In this embodiment, the image sensor 14 is a CMOS sensor and is located in the center of the circuit board 13. However, this is not limiting. In other embodiments of the present application, the image sensor 14 may also be a charge-coupled device (CCD). Furthermore, when the circuit board 13 is pushed up and down by the multiple voice coil motors 12, the distance between the image sensor 14 and the lens 16 will change, as shown in Figures 3A and 3B. The first distance H1 in Figure 3A is the distance between the image sensor 14 and the lens 16 before the circuit board 13 is pushed by the voice coil motor 12. The second distance H2 in Figure 3B is the distance between the image sensor 14 and the lens 16 after the circuit board 13 is pushed by the voice coil motor 12. The first distance H1 is greater than the second distance H2.

[0027] Referring again to FIG. 1 , the image processor 15 is located in the camera module and can be disposed on the circuit board 13 or other circuit boards ( FIG. 1 shows the image processor 15 not being located on the circuit board 13 ). The image processor 15 can be electrically connected to the image sensor 14 to obtain an analog electrical signal transmitted from the image sensor 14 and convert it into corresponding image information. An analog / digital conversion circuit (A / D Conversion Circuit) can be provided between the image sensor 14 and the image processor 15 to convert the analog electrical signal generated by the image sensor 14 into a digital signal to facilitate subsequent processing by the image processor 15 . However, in other embodiments of the present application, the analog / digital conversion circuit can also be integrated into the image processor 15 according to the design requirements of the circuit architecture.

[0028] Continuing with the above, please refer again to FIG. 1 , the image processor 15 can calculate a flatness deviation value based on the image information. The algorithm used for the calculation can adopt the Fast Fourier Transform (FFT), Discrete Cosine Transform (DCT), or Gradient Method, etc. Simply put, in a clear (focused) image, the difference in grayscale values ​​between adjacent pixels is large, especially at the edges. In other words, a clear (focused) image will show a clear edge, but a blurred (out-of-focus) image does not have the aforementioned characteristics. Therefore, the image processor 15 will be able to obtain the flatness deviation value required to change the target image from out-of-focus to in-focus through the aforementioned algorithm. The image processor 15 then generates at least one corresponding displacement control message based on the aforementioned calculation results and transmits each displacement control message to each voice coil motor 12, causing each voice coil motor 12 to push the circuit board 13 until the image sensor 14 on the circuit board 13 is in focus with the lens 16. Because the pushing distances of each voice coil motor 12 can be the same or different, by controlling how different voice coil motors 12 push the circuit board 13, the position between the circuit board 13 (including the image sensor 14) and the lens 16, as well as the tilt of the circuit board 13 itself, can be adjusted. This ensures that the circuit board 13, along with one side of the image sensor 14, remains aligned and level with the lens 16, allowing the image to be focused on the image sensor 14.

[0029] Furthermore, in this embodiment, referring again to Figures 1 and 2 , the image processor 15 is provided with an original flatness value. When the image processor 15 generates the image information, it generates each displacement control information based on the original flatness value and the flatness deviation value. The original flatness value is the distance between the circuit board 13 (including the image sensor 14) and the lens 16, and this distance also includes the tilt angle between the circuit board 13 and the lens 16. Furthermore, based on the original flatness value and the flatness deviation value, the image processor 15 calculates the required displacement distance of the circuit board 13 and deduces the individual displacement distances of each voice coil motor 12, so that the image sensor 14 can capture a clear image (i.e., a well-focused image).

[0030] Generally speaking, in the early stages of camera module production, in order to maintain the flatness between the lens 16 and the circuit board 13 (including the image sensor 14), it is usually necessary to use expensive equipment to adjust their tilt so that the optical axis L of the lens 161 of the lens 16 can remain orthogonal to the circuit board 13 (including the image sensor 14) (i.e., maintain good flatness). This situation will cause the industry to bear increased costs. However, through the overall structure of the present application, the image processor 15 can be based on the effective focal length of the lens 16 and the focus target. For example, the lens 161 on the left in FIG. 4 has an effective focal length of 5.0 mm and corresponds to the shooting target 21; the lens 161 on the right in FIG. 4 has an effective focal length of 60.0 mm and corresponds to the shooting target 22. After receiving the shooting information from the image sensor 14, the image processor 15 can generate corresponding image information and calculate the flatness value that meets the above-mentioned image information (as shown by the thick black line in FIG. 5). Afterwards, the image processor 15 can calculate the original flatness value and the above-mentioned flatness value. The flatness deviation value (as indicated by the dotted line in FIG. 5 ) is used to generate displacement control information required by each voice coil motor 12 to push the circuit board 13, thereby maintaining the circuit board 13 (including the image sensor 14) and the optical axis L of the lens 161 of the lens 16 at right angles or substantially right angles, thereby achieving alignment and flatness of the circuit board 13 (including the image sensor 14). This not only eliminates the cost of conventional expensive equipment for tilt adjustment, but also allows the multiple voice coil motors 12 to conveniently adjust the flatness between the circuit board 13 (including the image sensor 14) and the lens 16 if the lens 16 deflects due to external forces or other factors during subsequent use.

[0031] The above description is only a preferred feasible embodiment of the present application and does not limit the scope of protection of the claims of the present application. Therefore, any equivalent changes that a person skilled in the art can think of without creative work based on the technical content disclosed in the present application should be included in the scope of protection of the claims of the present application.

Claims

1. An automatic alignment focusing structure with a voice coil motor, applicable to a camera module having an image processor and a lens fixed by a mechanism and unable to move, characterized in that: The focusing structure includes: a substrate; A plurality of voice coil motors are disposed on a side surface of the substrate and are spaced apart from each other; a circuit board located at one end of the plurality of voice coil motors and capable of being pushed and displaced by the plurality of voice coil motors; and an image sensor located on a side of the circuit board and capable of converting a light signal projected onto the image sensor via the lens into an analog electrical signal; The image sensor is capable of transmitting the analog electrical signal to the image processor in the camera module, so that the image processor can convert the analog electrical signal into corresponding image information, calculate a flatness deviation value based on the image information, and generate at least one displacement control information corresponding to the flatness deviation value; Each of the voice coil motors can receive the displacement control information transmitted from the image processor and push the circuit board according to the displacement control information so that the circuit board and one side of the image sensor can be aligned and flat with the lens, and the object image falls on the image sensor to achieve focusing.

2. The focusing structure according to claim 1, wherein: The image processor is provided with an original flatness value, and the displacement control information received by the voice coil motor is generated by the image processor according to the original flatness value and the flatness deviation value.

3. The focusing structure according to claim 1, wherein: The focusing structure is provided with four voice coil motors, and each of the voice coil motors is respectively close to four corners of the circuit board.

4. The focusing structure according to claim 3, characterized in that: The image sensor is arranged in the central area of ​​the circuit board.

5. The focusing structure according to claim 1, wherein: The image sensor is of CMOS specification.

6. The focusing structure according to claim 1, characterized in that: The voice coil motor can only push the circuit board in its own axial direction.

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