CN102540639A - Automatic focusing method and image capturing system - Google Patents

Abstract

The present invention relates to an auto-focusing method and an image capturing system, and more particularly, to an auto-focusing method and an image capturing system for focusing in a first moving interval of a focusing mode by a focusing lens and recording a plurality of first focusing positions and a plurality of corresponding first focusing data. Then, it is determined whether the first focus data has an absolute maximum value. If not, determining a second moving interval, and focusing the focusing lens in the second moving interval to obtain a plurality of second focusing data; and determining an absolute maximum value according to the second focusing data, and enabling a second focusing position corresponding to the absolute maximum value to be an automatic focusing position.

Description

Autofocus method and image capture system

technical field

The invention relates to an imaging technology, in particular to an automatic focusing method of an image capture system.

Background technique

Before the digital camera leaves the factory, it usually calibrates the infinity focus position of the focus lens, and records the corrected infinity focus position in the internal memory of the digital camera. When the user half-presses the shutter button to start the auto-focus procedure, the digital camera uses the stored infinity focus position as a reference to move the focus lens to focus.

However, digital cameras are often affected by external environmental changes, such as temperature or humidity changes, or by external forces, such as falling or different placements, causing the focus lens to shift, making the real infinity focus position different from the calibration value before leaving the factory , causing the focus lens to fail to move to the correct focus position, allowing users to shoot blurry images due to poor focus or failure. Especially for lenses made of plastic, since the plastic material itself is easy to absorb moisture, it is easy to cause changes in the refractive index of the lens. In addition, the lens may expand and contract with temperature and humidity, or the moisture content may change, resulting in a change in the refractive index.

It can be seen that the above-mentioned existing imaging technology obviously still has inconvenience and defects in the method and use, and needs to be further improved urgently. In order to solve the above-mentioned existing problems, relevant manufacturers have tried their best to find a solution, but no suitable design has been developed for a long time, and there are no suitable methods and methods to solve the above-mentioned problems. This is obviously a problem that relevant industry players are eager to solve. Therefore, how to create a new autofocus method and image capture system is one of the current important research and development topics, and has also become a goal that the industry needs to improve.

Contents of the invention

The purpose of the present invention is to overcome the defects of existing imaging technology, and provide a new autofocus method and image capture system, the technical problem to be solved is to make it propose an autofocus method and image capture system , to correct the deviation of the preset focus position due to the influence of the external environment, so as to be able to accurately focus automatically, which is very suitable for practical use.

The purpose of the present invention and the solution to its technical problems are achieved by adopting the following technical solutions. According to the present invention, a focus lens is used to focus in a first movement interval of a focus mode; a plurality of first focus positions and corresponding first focus data are recorded; and it is judged whether the first focus data has an absolute the maximum value; if not, then determine a second movement interval; make the focusing lens focus in the second movement interval to obtain a plurality of second focus data; and determine the absolute maximum value according to the second focus data, And make a second focus position corresponding to the absolute maximum value an automatic focus position.

The purpose of the present invention and its technical problems can also be further realized by adopting the following technical measures.

The aforementioned auto-focus method further includes: when it is determined that there is an absolute maximum value in the first focus data, determining the first focus position corresponding to the absolute maximum value as the auto-focus position.

In the aforementioned auto-focus method, wherein the first focus data and the second focus data are edge sharpness values.

In the aforementioned autofocus method, wherein the first movement interval is between a first preset position and a second preset position, when the first focus data corresponding to the second preset position is relatively maximum value, the second moving interval is to move outward from the second preset position to a third preset position; when the first focus data corresponding to the first preset position is a relative maximum value, then the The second movement interval is outward translation from the first preset position to a fourth preset position.

The purpose of the present invention and the solution to its technical problem also adopt the following technical solutions to achieve. According to the present invention, a focus lens is proposed; an actuator drives the focus lens to a plurality of first focus positions in a first movement interval of a focus mode; a storage device is used to record the above-mentioned first focus positions and corresponding A plurality of first focus data; and a central processing system, used to determine whether there is an absolute maximum value in the first focus data; wherein when the absolute maximum value does not exist in the first focus data, the central processing system determines a first focus data Two movement intervals, and the actuator drives the focus lens to move within the second movement interval to obtain a corresponding plurality of second focus data, and the central processing system determines the absolute maximum value according to the second focus data , and make a second focus position corresponding to the absolute maximum value an automatic focus position.

The purpose of the present invention and its technical problems can also be further realized by adopting the following technical measures.

In the aforementioned image capture system, wherein the first movement interval is between a first preset position and a second preset position, when the first focus data corresponding to the second preset position is relative to When the maximum value is reached, the second movement interval is translated outward from the second preset position to a third preset position; when the first focus data corresponding to the first preset position is the relative maximum value, then The second moving section is outwardly translated from the first preset position to a fourth preset position.

In the aforementioned image capture system, the first preset position is an infinity focus position stored in the storage device.

In the aforementioned image capture system, the storage device has a built-in actuation step adjustment table for adjusting an actuation step change rate of the actuator according to the focusing mode and an environmental parameter.

In the aforementioned image capture system, the central processing system adjusts the third preset position and the fourth preset position according to the actuation step adjustment table.

The aforementioned image capture system, wherein the central processing system updates the infinity focus position according to the fourth preset position, and the storage device updates the actuation step adjustment table according to the fourth preset position .

Compared with the prior art, the present invention has obvious advantages and beneficial effects. As can be seen from above technical scheme, main technical content of the present invention is as follows:

In order to achieve the above object, the present invention provides an autofocus method. Firstly, a focus lens is used to focus in a first movement interval of a focus mode, and multiple first focus positions and corresponding multiple first focus data are recorded. Next, it is judged whether there is an absolute maximum value in the first focusing data. If not, then determine a second movement interval, and make the focus lens focus in the second movement interval, so as to obtain a plurality of second focus data; and determine the absolute maximum value according to the second focus data, and make the absolute maximum The second focusing position corresponding to the value is an auto-focusing position.

In addition, to achieve the above object, the present invention also provides an image capture system, which includes a focusing lens, an actuator, a storage device, and a central processing system. The actuator drives the focus lens to a plurality of first focus positions in a first movement interval of a focus mode. The storage device records the above-mentioned first focus position and a plurality of corresponding first focus data. The central processing system determines whether there is an absolute maximum value in the first focusing data. Wherein, when the above-mentioned first focus data does not have an absolute maximum value, the central processing system determines a second movement interval, and makes the actuator drive the focus lens to move within the second movement interval, so as to obtain corresponding multiple second focus data, and the central processing system determines the absolute maximum value according to the second focus data, and makes the second focus position corresponding to the absolute maximum value an auto-focus position.

By means of the above-mentioned technical solution, the autofocus method and image capture system of the present invention have at least the following advantages and beneficial effects: when the digital camera is subject to changes in the external environment or external force, the focus lens is shifted, so that the true infinity focus position Different from the calibration value before leaving the factory, the focus lens can automatically move to the correct focus position, overcoming blurred images caused by poor focus or failure of the user. Especially for lenses made of plastic, since the plastic material itself is easy to absorb moisture, it can automatically correct for changes in the refractive index of the lens.

To sum up, the present invention relates to an auto-focus method and an image capture system, especially to use a focus lens to focus in a first movement interval of a focus mode, and record a plurality of first focus positions and corresponding A plurality of first focusing data. Next, it is judged whether there is an absolute maximum value in the first focusing data. If not, then determine a second moving interval, and make the focusing lens focus in the second moving interval, so as to obtain a plurality of second focusing data; and determine the absolute maximum value according to the above-mentioned second focusing data, and make the absolute maximum The second focusing position corresponding to the value is an auto-focusing position. The present invention has significant progress in technology, and has obvious positive effects, and is a novel, progressive and practical new design.

The above description is only an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, it can be implemented according to the contents of the description, and in order to make the above and other purposes, features and advantages of the present invention more obvious and understandable , the following preferred embodiments are specifically cited below, and are described in detail as follows in conjunction with the accompanying drawings.

Description of drawings

FIG. 1 is a functional block diagram of the image capture system of the embodiment of the autofocus method and the image capture system of the present invention.

FIG. 2 is a flow chart of the auto-focus method and the auto-focus method of the image capture system embodiment of the present invention.

3A, 3B, and 3C illustrate various edge curves.

10: Lens module 102: Focus lens

104: Lens driving device 12: Storage device

122: memory 124: hard disk

14: Central processing system 142: Computing unit

144: Control unit 16: Image sensing unit

18: Environmental parameter sensing unit 21-27: Steps

D1: the first moving interval D2, D3: the second moving interval

F1: First preset position F2: Second preset position

F3: The third preset position F4: The fourth preset position

AF, AF’, AF”: auto focus position

Detailed ways

In order to further explain the technical means and effects that the present invention adopts to achieve the intended purpose of the invention, below in conjunction with the accompanying drawings and preferred embodiments, the specific implementation methods, methods, Steps, features and effects thereof are described in detail below.

FIG. 1 shows a functional block diagram of an image capture system according to an embodiment of the present invention. The image capture system of this embodiment is mainly used to perform autofocus. The image capture system can be a camera, video camera, mobile phone, personal digital assistant (Personal Digital Assistant, PDA), digital music (MPEG Audio Layer 3, MP3 ) player or webcam, but not limited thereto. In this embodiment, the image capture system mainly includes a lens module 10 , a storage device 12 and a central processing system 14 . In addition, the image capture system may further include an image sensing unit 16 and an environmental parameter sensing unit 18 .

As shown in FIG. 1 , the lens module 10 of this embodiment includes a focusing lens 102 and a lens driving device 104 . Wherein, the focus lens 102 can move within a preset movement interval to focus on the subject. The focus lens 102 generally includes at least one focus lens. The lens driving device 104 is controlled by the central processing system 14 and is used to drive the focus lens of the focus lens 102 to move to a plurality of focus positions. The lens driving device 104 may include an actuator, such as a stepping motor, but not limited thereto.

Please continue to refer to FIG. 1, the image captured by the lens module 10 is converted from an analog optical signal to a digital electrical signal through the image sensing unit 16, which includes a plurality of focusing data obtained by the lens module 10, such as edge sharpness (sharpness) value. Then, the above focus data is fed to the central processing system 14 for calculation and processing. The central processing system 14 of this embodiment includes a computing unit 142 and a control unit 144 . Wherein, the calculation unit 142 performs numerical calculation on the focus data, and the control unit 144 determines how to control the lens driving device 104 to move the focus lens 102 according to the calculation result, and finally obtains an auto-focus position. The operation unit 142 of this embodiment can be a digital signal processor, the control unit 144 can be a central processing unit, and the central processing system 14 can be a chip in practice, and the operation unit 142 and the control unit 144 are integrated on the chip , but not limited to this.

Please continue to refer to FIG. 1 , the storage device 12 is mainly used to record the aforementioned focus positions and corresponding focus data. The storage device 12 in this embodiment includes a built-in memory 122 as a main memory and a hard disk 124 as a secondary memory. In addition, the storage device 12 can also be used to store the focus position at infinity. Specifically, in one embodiment, the storage device 12 stores the actuation step adjustment table of the lens driving device 104, which records the change of the actuation step corresponding to the change rate of the environmental parameter of each focus mode (zoom mode). rate, where the environmental parameter refers to temperature or humidity, but is not limited thereto. Table 1 below shows an example of an actuation step adjustment table. In Table 1, temperature is used as an environmental parameter as an example. In this example, for the wide-angle focus mode, if the infinity focus position at a temperature of 25°C is the position of 200 steps, then at a temperature of 0°C, the infinity focus position will become the position of 150 steps, that is, 200 steps -10*((25-0)/5). In one embodiment, the central processing system 14 can update the adjusted infinity focus position in the storage device 12 . The above-mentioned temperature change can be provided by the environmental parameter sensing unit 18 .

Table I

FIG. 2 shows a flowchart of an auto-focusing method according to an embodiment of the present invention, which is applicable to the image capture device shown in FIG. 1 . Please also refer to the image capture device shown in FIG. 1 for the following description of the process in FIG. 2 . First, in step 21 , in a focus mode, focus is performed at a plurality of first focus positions of the focus lens 102 in a first movement interval of the focus mode. As mentioned above, the focusing lens 102 can be driven to the above-mentioned first focusing position by the actuator of the lens driving device 104 . Taking digital cameras as an example, digital cameras are generally divided into several focus modes, such as general focus mode and close focus mode. The focus range is from 80cm to 10cm, but not limited thereto. Next, in step 22 , the storage device 12 records the first focus position and the corresponding first focus data. In this embodiment, the first focus data is an edge sharpness value. The above-mentioned first focus position and the above-mentioned first focus data jointly form an edge curve. FIG. 3A is an example of an edge curve, the vertical axis represents the focus data, and the horizontal axis represents the focus position. In this example, the first moving section D1 is between the first preset position F1 and the second preset position F2. Wherein, the first preset position F1 may be an infinity focus position, which may be stored in the storage device 12 .

Please continue to refer to FIG. 1 , FIG. 2 and FIG. 3A , in step 23 , the central processing system 14 judges whether there is an absolute maximum value in the above-mentioned first focusing data of the edge curve. In this embodiment, the values at the front and rear adjacent positions of the "absolute maximum value" are all smaller than the absolute maximum value. If the judging result in step 23 is that the edge curve already has an absolute maximum value, go to step 24 and determine the first focus position corresponding to the absolute maximum value as the auto focus position. Taking the edge curve shown in FIG. 3A as an example, the central processing system 14 judges that there is an absolute maximum value at the first focus position AF according to the slope of the edge curve, or according to the values of the front and rear adjacent positions of the first focus position, and Define this position as the auto focus position.

Please refer to FIG. 1 and FIG. 2, if the judgment result in step 23 is that the edge curve does not have an absolute maximum value, then enter step 25, and the central processing system 14 calculates the second movement interval according to the edge curve. Next, in step 26 , the central processing system 14 enables the actuator of the lens driving device 104 to move the focus lens 102 to focus at a plurality of second focus positions in the second moving interval, so as to obtain a plurality of corresponding second focus data. Like the aforementioned first focus data, the second focus data in this embodiment is the edge sharpness value. Finally, in step 27 , the central processing system 14 defines an absolute maximum value according to the slope or value of the edge curve of the second focus data, and uses the second focus position corresponding to the absolute maximum value as the auto-focus position.

FIG. 3B illustrates another edge curve. The first focus data corresponding to the second preset position F2 is not an absolute maximum value for the first movement interval D1, but only a relative maximum value. That is, the central processing system 14 according to the edge curve It is judged that only a relative maximum value exists in the first focusing data by a slope or a numerical value of . Therefore, according to step 25, the second preset position F2 is translated outward to the third preset position F3 to obtain a second movement interval D2 between the second preset position F2 and the third preset position F3, Or push back from the third preset position F3 to a specific position before the second preset position F2 as the second movement interval D2, that is, the second movement interval D2 can be from the second preset position F2 to the third The preset position F3 may also be from a specific position to a third preset position F3, including the second preset position F2. Please refer to FIG. 1 and FIG. 2 at the same time. Specifically, the third preset position F3 can be calculated by the central processing system 14 using an extrapolation method based on the edge curve, or a preset value that has been built in the storage device 12. Set the distance value; and the specific position can be the preset distance value that the focus lens 102 is advanced from the second preset position F2 to the first preset position F1 direction by the lens driving device 104, for example, if a stepping motor is used as the lens driving device 104, the set specific position is the position where the stepper motor advances from the second preset position F2 to the first preset position F1 by a preset number of steps, but it is not limited thereto. In this embodiment, the second movement interval D2 is from the second preset position F2 to the third preset position F3.

Please refer to FIG. 1 and FIG. 2 again, and then, according to step 26 , the focus lens 102 is moved in the second movement interval D2 to obtain the second focus data. Finally, according to step 27, the absolute maximum value of the second movement interval D2 is determined, and the corresponding second focus position AF' is used as the automatic focus position. Taking the edge curve shown in FIG. 3B as an example, the central processing system 14 judges that there is an absolute maximum value at the second focus position AF', and therefore makes it the auto focus position.

3C illustrates yet another edge curve, the first focus data corresponding to the first preset position F1 is not the absolute maximum value for the first movement interval D1, but only a relative maximum value, that is, the central processing system 14 according to the edge curve The slope or value of is judged as the relative maximum value. Therefore, according to step 25, the first preset position F1 is outwardly translated to the fourth preset position F4, thereby obtaining a second movement interval D3 between the first preset position F1 and the fourth preset position F4, Or push back from the fourth preset position F4 to a specific position after the first preset position F1 as the second movement interval D3, that is, the second movement interval D3 can be from the first preset position F1 to the fourth The preset position F4 may also be from a specific position to a fourth preset position F4, including the first preset position F1. In this embodiment, the first preset position F1 to the fourth preset position F4 are used as the second movement interval D3, but it is not limited thereto. Next, according to step 26 , move the focus lens 102 in the second movement interval D3 to obtain second focus data. Finally, according to step 27, the absolute maximum value of the second movement interval D3 is determined, and the corresponding second focus position AF" is used as the automatic focus position. Taking the edge curve shown in FIG. 3C as an example, the central processing system 14 judges the second focus position There is an absolute maximum at position AF", so that makes it the autofocus position.

Please refer to FIG. 1, FIG. 3B, FIG. 3C and Table 1. In one embodiment, the central processing system 14 can adjust the actuator of the lens driving device 104 according to the focusing mode and the current environmental parameters, such as temperature or humidity. Rate of change of actuation steps. Furthermore, the central processing system 14 can also adjust the third preset position F3 and the fourth preset position F4 according to the actuation step adjustment table as shown in Table 1. In another embodiment, the central processing system 104 can update the focus position at infinity according to the fourth preset position F4, and the storage device 12 can update the number of actuation steps as shown in Table 1 according to the fourth preset position F4 The modulation table is not limited thereto. Those skilled in the art can also adjust other environmental parameters to revise another actuation step modulation table or replace it with an actuation step modulation formula.

The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this field Those skilled in the art, without departing from the scope of the technical solution of the present invention, may use the technical content disclosed above to make some changes or modify them into equivalent embodiments with equivalent changes, but as long as they do not depart from the technical solution of the present invention, the Technical Essence Any simple modifications, equivalent changes and modifications made to the above embodiments still fall within the scope of the technical solution of the present invention.

Claims (10)

1. automatic focusing method is characterized in that it comprises following steps:

Utilize a focus lens in one first moving section of a focusing pattern, to focus;

Write down a plurality of first focusing positions and corresponding a plurality of first focus data;

Judge whether above-mentioned first focus data exists a bare maximum;

As not, then determine one second moving section;

This focus lens is focused, to obtain a plurality of second focus data in this second moving section; And

According to this bare maximum of above-mentioned second focus data decision, and make with corresponding one second focusing position of this bare maximum be an automatic focusing position.

2. automatic focusing method as claimed in claim 1 is characterized in that it more comprises: when judging that there is a bare maximum in above-mentioned first focus data, then decision is this automatic focusing position with corresponding this first focusing position of this bare maximum.

3. automatic focusing method as claimed in claim 1 is characterized in that above-mentioned first focus data and above-mentioned second focus data are clear-cut margin degree values.

4. automatic focusing method as claimed in claim 1; It is characterized in that this first moving section is between one first predeterminated position and one second predeterminated position; When corresponding this first focus data of this second predeterminated position was relative maximum, then this second moving section was outwards to move to one the 3rd predeterminated position from this second predeterminated position; When corresponding this first focus data of this first predeterminated position was relative maximum, then this second moving section was outwards to move to one the 4th predeterminated position from this first predeterminated position.

5. image acquisition system is characterized in that it comprises:

One focus lens;

One actuator drives this focus lens to a plurality of first focusing positions in one first moving section of a focusing pattern;

One storage device is in order to write down above-mentioned first focusing position and corresponding a plurality of first focus data; And

Whether one central processing system exists a bare maximum in order to determine above-mentioned first focus data;

Wherein work as above-mentioned first focus data and do not have this bare maximum; Then this central processing system determines one second moving section; And this focus lens of this actuator is moved in this second moving section; Obtaining corresponding a plurality of second focus data, and this central processing system is according to above-mentioned this bare maximum of second focus data decision, and make with corresponding one second focusing position of this bare maximum be an automatic focusing position.

6. image acquisition system as claimed in claim 5; It is characterized in that this first moving section is between one first predeterminated position and one second predeterminated position; When corresponding this first focus data of this second predeterminated position was relative maximum, then this second moving section was outwards to move to one the 3rd predeterminated position from this second predeterminated position; When corresponding this first focus data of this first predeterminated position was relative maximum, then this second moving section was outwards to move to one the 4th predeterminated position from this first predeterminated position.

7. image acquisition system as claimed in claim 6 is characterized in that this first predeterminated position is an infinite distance focusing position that is stored in this storage device.

8. image acquisition system as claimed in claim 7 is characterized in that building in this storage device one and activates step number modulation table, in order to activate the step number rate of change according to one of this focal modes and this actuator of environmental parameter modulation.

9. image acquisition system as claimed in claim 8 is characterized in that this central processing system is according to this actuating step number modulation table, with modulation the 3rd predeterminated position and the 4th predeterminated position.

10. image acquisition system as claimed in claim 8 it is characterized in that this central processing system according to this infinite distance focusing position of the 4th predeterminated position renewal, and this storage device should activate step number modulation table according to the 4th predeterminated position to upgrade.

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