CN110830710A - Focusing method of super-long focal length lens - Google Patents

Focusing method of super-long focal length lens Download PDF

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CN110830710A
CN110830710A CN201910207912.9A CN201910207912A CN110830710A CN 110830710 A CN110830710 A CN 110830710A CN 201910207912 A CN201910207912 A CN 201910207912A CN 110830710 A CN110830710 A CN 110830710A
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focus
focal length
lens
distance
value
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CN110830710B (en
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张腾腾
黄仝宇
汪刚
宋一兵
侯玉清
刘双广
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Gosuncn Technology Group Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/60—Control of cameras or camera modules
    • H04N23/67—Focus control based on electronic image sensor signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N23/00—Cameras or camera modules comprising electronic image sensors; Control thereof
    • H04N23/50—Constructional details
    • H04N23/55—Optical parts specially adapted for electronic image sensors; Mounting thereof

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Abstract

The invention belongs to the technical field of camera focusing, and particularly relates to a focusing method of an ultra-long focal lens. Therefore, according to a relevant calculation formula in a program, a focus value can be obtained under the known distance and zoom values, so that the focusing lens can be quickly pulled to a corresponding position, and the accuracy is also ensured. The scheme can effectively solve the related problems of the super-long-focus lens due to the large focal length range. The focusing speed is fast and accurate, and the focusing success rate is high; effectively reducing the loss of the focusing motor and prolonging the service life of the lens.

Description

Focusing method of super-long focal length lens
Technical Field
The invention relates to the technical field of camera focusing, in particular to a focusing method of an ultra-long focal length lens.
Background
Whether the automatic focusing lens can automatically focus to obtain a clear image or not in the image acquisition process is the first step of analyzing and processing the image, and whether the electric lens actuating mechanism can quickly move to a corresponding zooming position or not is determined. The traditional manual focusing mode mainly depends on visual measurement and manual adjustment of people, is not only tedious and long in time consumption, but also has great subjective influence on longitude adjustment by people. Therefore, the auto-focus lens is more and more favored.
At present, the focusing mode of an ultra-long focal length lens (the focal length is more than 500mm) is mainly adopted by the method that in the focusing range of the lens, the lens is firstly pulled up by a motor, and the clearest point of an image is searched back and forth by a related algorithm.
The prior art has the following disadvantages: because the focal length of the super-long focal lens is much longer than that of a common lens, in the traditional focusing method, when a motor pulls a focusing lens back and forth, the time consumed by focusing is much longer than that of the common lens, meanwhile, because the multiplying power range of the super-long focal lens is large, the pulling-up range of the focusing lens becomes very large when the lens is zoomed from the widest angle to the longest angle, in addition, the field angle of the widest angle is narrow, the image characteristics after zooming to the long focal length are almost not available, the focusing algorithm of software can not calculate a high-peak focusing point according to the image, and the motor can push and search back and forth at this time, so that the service life of the motor is greatly shortened, and meanwhile, the accuracy and the success rate of focusing are greatly reduced.
Disclosure of Invention
The invention aims to provide a focusing method of an ultra-long focal length lens, which aims to solve the problems of low focusing speed, low focusing accuracy and the like of the conventional focusing method.
The invention is realized by the following technical scheme:
a focusing method of an ultra-long focal length lens comprises the following steps:
s1, acquiring the distance from the camera to the target point through an automatic distance measuring device, acquiring the focal length value focus at the distance, and repeating the step to acquire the focal length values focus at different object distances and different magnifications;
s2, fitting the relation between the focal length value focus, the object distance and the multiplying power zoom through a fitting formula;
s3, acquiring a second distance and a second magnification zoom of the camera, and acquiring a second focal length value focus according to the relation between the focal length value focus, the object distance and the magnification zoom, which is fitted in the step S2;
and S4, rapidly pulling the focusing lens to a corresponding position according to the second focal length value focus acquired in the step S3.
Further comprising fitting the focus curve at each object distance using F ═ a × exp (b × Z) + c × exp (d × Z) to obtain coefficient parameters: a. b, c, d, wherein F is the focus value and Z is the zoom value;
the obtained actual object distance is D0Zoom value of Z0Focus value F (Z)0) The calculation steps are as follows:
(1) firstly, the actual object distance D is calculated0Left and right two adjacent critical object distances D1And D2Focus value Fx (Z)0) And Fy (Z)0)，D1<D0<D2，
Fx(Z0)＝a1*exp(b1*Z0)+c1*exp(d1*Z0)
Fy(Z0)＝a2*exp(b2*Z0)+c2*exp(d2*Z0)
Wherein，a1、b1、c1、d1And a2、b2、c2、d2Respectively, critical object distance D1And D2The coefficient parameter of (2);
(2) using Fx (Z)0) And Fy (Z)0) Is calculated by the difference of (D)0Focus value of (d):
F(Z0)＝Fx(Z0)+(Fx(Z0)-Fy(Z0) λ), where λ is a fixed parameter, λ ═ D (D)0-D1)/(D2-D1)。
Preferably, if the object distance is greater than the maximum object distance, i.e., 1200 m, the focus value at 1200 m may be directly calculated.
Preferably, the object distance is obtained in real time by a distance measuring sensor.
Preferably, the magnification zoom and the focal length value focus are acquired by a closed-loop control motor system.
Preferably, the related data of the experimental test is acquired, the object distance is changed under the same zoom value, the current focal length value focus is respectively tested at intervals of a certain distance, and the record is made.
Preferably, the maximum distance for lens tests of different focal lengths also differs, depending on the returned focal length value focus, as a test threshold when focus no longer changes.
Preferably, the experimental test data is simulated by Matlab.
Preferably, a three-dimensional stereo image with distance as an X-axis, zoom step number as a Y-axis and focus as a Z-axis is created by using the dark fixing Tool.
Preferably, the relevant distance measuring sensor is mounted alongside the lens so that the lens and the target object of the distance measuring sensor are as consistent as possible.
Compared with the prior art, the invention has at least the following beneficial effects or advantages:
the focusing method of the super-long-focus lens provided by the invention effectively solves the relevant problems of the super-long-focus lens caused by large focal length range; the focusing speed is high, the focusing is accurate, and the focusing success rate is high; effectively reduces the loss of the focusing motor and prolongs the service life of the lens.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings;
FIG. 1 is a block diagram of an automatic distance measuring device of the present invention;
FIG. 2 is a three-dimensional spatial data plot based on Distance, Zoom and Focus of the present invention.
Detailed Description
The invention is described in further detail below with reference to specific embodiments and with reference to the attached drawings.
The scheme provides a focusing method of an ultra-long focal length lens. The method mainly comprises the steps of obtaining the distance from a camera to a target point through an automatic distance measuring device, testing focal length values (focus) at different object distances (distances) and different multiplying powers (zoom) through experiments, and fitting a related calculation formula algorithm. Therefore, the focus value can be obtained under the known diatance and zoom values according to the relevant calculation formula in the program, so that the focusing lens can be quickly pulled to the corresponding position, and the accuracy is also ensured. The focusing method comprises the following steps:
s1, acquiring the distance from the camera to the target point through an automatic distance measuring device, acquiring the focal length value focus at the distance, and repeating the step to acquire the focal length values focus at different object distances and different magnifications;
s2, fitting the relation between the focal length value focus, the object distance and the multiplying power zoom through a fitting formula;
s3, acquiring a second distance and a second magnification zoom of the camera, and acquiring a second focal length value focus according to the relation between the focal length value focus, the object distance and the magnification zoom, which is fitted in the step S2;
and S4, rapidly pulling the focusing lens to a corresponding position according to the second focal length value focus acquired in the step S3.
The specific method comprises the following steps:
1. acquiring experimental data: the lens and the target object of the sensor can be kept consistent as much as possible by mounting the relevant distance measuring sensor and the lens side by side. Thus, distance is obtained in real time through the sensor, zoom and focus are obtained through the closed-loop control motor system, and the distance measuring device is shown in figure 1.
2. Experimental test-related data: under the same zoom (Z) value, the object distance (D) is changed, and the current focus (F) value is tested at intervals and recorded. The maximum distance of lens test is different according to different focal lengths, and the focus is not changed any more as a critical point according to the returned focus value. The experimental data are shown in tables 1, 2, 3 and 4:
TABLE 1
Z\F\D 5300 90000 21000 125000 200000 500000 1200000
17410 3314 3311 3308 3317 3313 3308 3300
17268 3327 3324 3321 3317 3316 3315 3313
16788 3397 3394 3391 3379 3379 3381 3383
16329 3397 3419 3447 3467 3463 3457 3448
15888 3532 3509 3483 3516 3516 3518 3521
15463 3601 3594 3586 3581 3584 3590 3599
15053 3658 3664 3673 3664 3661 3657 3651
14655 3722 3688 3647 3729 3729 3729 3729
14269 3792 3770 3745 3794 3794 3794 3794
13892 3862 3854 3845 3859 3859 3859 3859
13525 3919 3919 3921 3898 3902 3911 3924
13166 3976 3975 3974 3962 3964 3969 3976
12815 4046 4023 3995 4027 4029 4034 4041
12471 4116 4074 4023 4092 4092 4092 4093
12133 4173 4172 4172 4157 4156 4155 4154
11801 4243 4234 4225 4222 4222 4223 4224
TABLE 2
Figure BDA0001999573030000051
Figure BDA0001999573030000061
TABLE 3
Figure BDA0001999573030000062
Figure BDA0001999573030000071
TABLE 4
Figure BDA0001999573030000072
Figure BDA0001999573030000081
3. Fitting a curve with experimental data to obtain a calculation formula: the tested experimental data are imported into Matlab, Distance is used as X axis, Zoom step number is used as Y axis, Focus is used as Z axis, and a Tool Curve fixing Tool is used to build an image, as shown in FIG. 2.
And finally, obtaining a formula model under each Distance through fitting. The data processing is as follows:
the focus curves at each object distance were fitted using F ═ a × exp (b × Z) + c × exp (d × Z) to yield coefficient parameters: a. b, c and d, wherein F is a Focus value (Focus value) and Z is a Zoom value;
the curve fitted at 5300mm, 5.3 meters, is:
F1＝7671*exp(-4.981e-05*Z)-1367*exp(-0.001027*Z)
the curve fit at 9000mm, i.e. 9 meters, is:
F2＝7565*exp(-4.882e-05*Z)-2013*exp(-0.001048*Z)
the curve fitted at 21000mm, 21 meters, is:
F3＝7436*exp(-4.757e-05*Z)-2801*exp(-0.001061*Z)
the curve fit at 125000mm, i.e. 125 m, is:
F4＝7229*exp(-4.483e-05*Z)-3350*exp(-0.001221*Z)
the curve fit at 200000mm, i.e. 200 m, is:
F5＝7210*exp(-4.459e-05*Z)-3381*exp(-0.001234*Z)
the curve fit at 500000mm, i.e. 500m, is:
F6＝7176*exp(-4.415e-05*Z)-3438*exp(-0.001259*Z)
the curve fitted at 1200000mm, i.e. 1200 m, is:
F7＝7170*exp(-4.408e-05*Z)-3419*exp(-0.001265*Z)
since there is partial focusing ambiguity (focusing near limit) within 5 meters, the object distance can be considered to be outside of 5 meters.
At this time, using these fitted curves, Zoom (motor control derived) can calculate that Focus should be controlled to a corresponding value at this time, which is clear, due to Distance (Distance sensor derived).
If a focus value F is to be calculated with Distance of 750 meters and Zoom value of 757 (757), the steps are as follows:
(1) the distance is found to be 500<750<1200, so the focus values at 500m and 1200 m are calculated as:
F6(757)＝7176*exp(-4.415e-05*757)-3438*exp(-0.001259*757)≈5615
F7(757)＝7170*exp(-4.408e-05*757)-3419*exp(-0.001265*757)≈5622
(2) the focus value at 750 meters is then calculated using the difference as follows:
λ＝(750-500)/(1200-500)≈0.35
F(757)＝F6(757)+(F6(757)-F7(757))*λ≈5615+(5622-5615)*0.35≈5617
and if the object distance is larger than 1200 m, directly calculating the focus value at the position of 1200 m.
4. The program is realized as follows: after the relevant formula model is obtained, the function of auxiliary focusing can be realized in the program.
In conclusion, the method for testing the focusing value according to the object distance and the focal length value and the method for achieving rapid and accurate focusing according to the formula model effectively reduce the loss of the focusing motor and prolong the service life of the lens. The related problems caused by the large focal length range of the super-long focal length lens are effectively solved; therefore, the focusing speed is high, the focusing is accurate, and the focusing success rate is high.
The above-mentioned embodiments are provided to further explain the objects, technical solutions and advantages of the present invention in detail, and it should be understood that the above-mentioned embodiments are only examples of the present invention and are not intended to limit the scope of the present invention. Any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the invention are also within the protection scope of the invention.

Claims (10)

1. A focusing method of an ultra-long focal length lens is characterized by comprising the following steps:
s1, acquiring the distance from the camera to the target point through an automatic distance measuring device, acquiring the focal length value focus at the distance, and repeating the step to acquire the focal length values focus at different object distances and different magnifications;
s2, fitting the relation between the focal length value focus, the object distance and the multiplying power zoom through a fitting formula;
s3, acquiring a second distance and a second magnification zoom of the camera, and acquiring a second focal length value focus according to the relation between the focal length value focus, the object distance and the magnification zoom, which is fitted in the step S2;
and S4, rapidly pulling the focusing lens to a corresponding position according to the second focal length value focus acquired in the step S3.
2. The method of claim 1, wherein the focus curve at each object distance is fitted using F ═ a × exp (b × Z) + c × exp (d × Z) to obtain coefficient parameters: a. b, c, d, wherein F is the focus value and Z is the zoom value;
the obtained actual object distance is D0Zoom value of Z0Focus value F (Z)0) The calculation steps are as follows:
(1) firstly, the actual object distance D is calculated0Left and right two adjacent critical object distances D1And D2Focus value Fx (Z)0) And Fy (Z)0)，D1<D0<D2，
Fx(Z0)＝a1*exp(b1*Z0)+c1*exp(d1*Z0)
Fy(Z0)＝a2*exp(b2*Z0)+c2*exp(d2*Z0)
Wherein, a1、b1、c1、d1And a2、b2、c2、d2Respectively, critical object distance D1And D2The coefficient parameter of (2);
(2) using Fx (Z)0) And Fy (Z)0) Is calculated by the difference of (D)0Focus value of (d):
F(Z0)＝Fx(Z0)+(Fx(Z0)-Fy(Z0))*λ
wherein λ is a fixed parameter, λ ═ D0-D1)/(D2-D1)。
3. The focusing method of the superlong focal lens according to claim 2, wherein if the object distance is greater than the maximum object distance, i.e. 1200 m, the focus value at 1200 m is directly calculated.
4. The focusing method of the superlong focal length lens as claimed in claim 2, wherein the object distance is obtained in real time by a distance measuring sensor.
5. The focusing method of the extra-long focal lens according to claim 2, wherein the magnification zoom and the focal value focus are acquired by a closed-loop control motor system.
6. The focusing method of the extra-long focal length lens as claimed in claim 2, wherein experimental test related data is obtained, the object distance is changed under the same zoom value, and the current focal length value focus is respectively tested at intervals and recorded.
7. The method of claim 6, wherein the maximum distance of lens test is different for different focal lengths, and is determined according to the returned focal length value focus, and is used as test threshold when focus is no longer changed.
8. The focusing method of the ultra-long focal length lens as claimed in claim 2, wherein the experimental test data is simulated by Matlab.
9. The focusing method of the extra-long focal lens according to claim 7, wherein a three-dimensional stereoscopic image with distance as an X-axis, zoom steps as a Y-axis, and focus as a Z-axis is created using a Curve fixing tool.
10. A method for focusing an extra-long-focus lens according to claim 3, wherein the associated distance measuring sensor is installed side by side with the lens so that the lens and the target object of the distance measuring sensor are as consistent as possible.
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CN110958387B (en) * 2019-11-19 2021-06-29 维沃移动通信有限公司 Content updating method and electronic equipment
CN111818261A (en) * 2020-07-07 2020-10-23 深圳市中江天华科技有限公司 Automatic focusing method and system based on flight time

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