CN108761776B - A zoom lens zoom cam optimization method - Google Patents

Abstract

The invention belongs to the field of photoelectric imaging equipment, and in particular relates to a zoom lens zoom cam optimization method. This method solves the problems of uneven zoom lens zoom cam, low zoom precision, slow speed, and easy jamming. The specific method steps are: [1] optical system design; [2] analysis of cam pressure angle; [3] 】Construct piecewise function of the whole cam according to the trend presented by the cam pressure angle;【4】Analyze the focal length output accuracy.

Description

A zoom lens zoom cam optimization method

technical field

The invention belongs to the field of photoelectric imaging equipment, and in particular relates to a zoom lens zoom cam optimization method.

Background technique

Optoelectronic equipment is mainly composed of optical lenses, detectors, peripheral circuits and equipment, of which the lens is an important part of its composition. In order to improve the application range of equipment, more and more zoom lenses are used. In the design of the zoom lens, the cam is still a commonly used mechanism for zooming and focusing, so the design of this mechanism is particularly important.

It is clearly pointed out in the relevant research theories of zoom lenses that various structural forms of zoom lenses have a certain range of focal length. can not achieve. The existing lens design uses multiple groups (three groups, four groups) to cooperate with the appropriate root change point to solve the contradiction between miniaturization and large zoom ratio, but the zoom group or compensation group spacing at the root change point The cam curve of the cam tends to turn rapidly and cause the pressure angle to be too large, and even the distance corresponding to the zoom group and compensation group will change in waves, which eventually makes the design impossible to realize in the structure. In addition, the change rate of the focal length at the root change point will change greatly. This change and the unsmoothness of the cam will lead to the instability of the motor driving force and will also lead to a decrease in the output accuracy of the focal length of the optical system.

Contents of the invention

In order to solve the problems existing in the background technology, this patent proposes an optimal design method of the zoom lens zoom cam to solve the problems of uneven zoom lens zoom cam, low zoom precision, slow speed, and easy jamming.

Concrete technical scheme of the present invention is:

The invention provides a zoom lens zoom cam optimization method, comprising the following steps:

【1】Optical system design;

【1.1】Output the corresponding spacing values of the focal length, zoom group and compensation group through the optical design software;

[1.2] Design the parameters related to the cam rotation angle;

[1.3] Obtain a linearly distributed cam curve according to steps [1.1] and [1.2];

【2】Analysis of cam pressure angle;

Analyze the linear distribution of the cam curve, if the analysis results meet the requirements of use, jump directly to step [4], if not meet the requirements, find the part of the cam pressure angle that is too large, and use this as a basis to divide the cam rotation angle, and prepare Go to step [3];

[3] According to the trend presented by the cam pressure angle, the entire cam is constructed as a piecewise function, and the construction needs to meet three conditions:

A. The values at the joints of each function are the same;

B. The differential results at the junctions of each section of the function are the same;

C. The change rate of each segment function is similar to the change rate of the cam pressure angle;

Then connect the piecewise functions to fit a nonlinear distribution cam curve, and then make a one-to-one correspondence between the nonlinear distribution cam curve and the focal length, zoom group, and compensation group and jump back to step [2] to analyze the nonlinear distribution Whether the cam pressure angle of the cam curve meets the requirements of use;

If the usage requirements are met, skip to step [4];

If the usage requirements are not met, then jump back to step [3], if there is no room for optimization, it means that there is a problem in the design, you need to jump back to step [1], and redesign the optical lens or cam structure;

【4】Analyze the focal length output accuracy;

If the focal length output accuracy meets the requirements of use, the result will be output directly;

If the output accuracy of the focal length does not meet the requirements of use, it is necessary to analyze the cause,

There are two reasons for this:

Case 1: due to the cam curve of the nonlinear distribution;

Case 2: It is not caused by the cam curve of nonlinear distribution;

For case 1, further optimize the cam curve with nonlinear distribution, jump to step [3], the optimization method is basically the same, the only difference is that it is segmented according to the focal length output accuracy, and the function is constructed. After the construction is completed, you need to re-enter Step [2];

For the second case, it is necessary to optimize the number of teeth of the cam barrel and the parameters of the focusing motor. After optimization, if the requirements are met, the results can be output directly.

Further, there are multiple piecewise functions, and the derivative values and function values of the joints of the piecewise functions are equal, and the piecewise functions can be connected to form a relatively continuous function.

Further, when the segmentation basis of the above segmental function is the cam rotation angle, if the cam pressure angle is too large or too small at a certain rotation angle, it can be independently regarded as a segmental function.

Further, during the construction of the above-mentioned piecewise function, the cam rotation angle corresponding to the position piecewise function with an excessively large pressure angle is re-divided with a larger amount. In order to compensate for the rotation angle occupied by a large part of the pressure angle, a certain limit Reduce the rotation angle corresponding to the part where the pressure angle is too small.

Further, the initial function of the above piecewise function is derived from the linear construction of the optical zoom output parameters and the cam structure parameters.

The advantages of the present invention are:

The invention provides a method for optimizing the cam curve in the zoom lens by using a piecewise function. The method can reduce the excessive part of the cam pressure angle in the zoom lens, and can also increase the small part of the cam pressure angle to make the zoom lens During the zooming process, the pressure angle of the cam changes within a certain range, and the output force is relatively stable when the motor controls its movement, thereby solving the problems of low zooming precision, unevenness, slow speed, and easy jamming in the zoom lens.

Description of drawings

Fig. 1 is a flow chart of the method provided by the present invention;

Fig. 2 is the cam optimization example of the present invention;

Fig. 3 is an example of optimization of focal length output precision in the present invention.

Detailed ways

Referring to FIG. 1 , the present invention provides an optimal design method to solve the problem of uneven cam, low zoom precision, slow speed and easy jamming in zoom lens design.

Its main process is shown in Figure 1:

First complete the first step of initialization, that is, complete the optical design, output the corresponding distance values of the focal length, zoom group, and compensation group through the optical design software, design and give the relevant parameters of the cam rotation angle, and then perform linear cam design according to the initial input parameters.

Secondly, complete the second step, which is the analysis of the cam pressure angle. If the analysis result meets the use requirements, jump directly to the fourth step. If the requirements cannot be met, divide the cam rotation angle, and prepare to enter the third step.

If you enter the third step of segmented function construction and optimization, you need to construct the segmented function according to the trend of the pressure angle of the corresponding segment, and the construction here needs to meet three conditions (1) The value of the connection of each segment function is the same, ( 2) The differential results at the joints of each segment function are the same, (3) The rate of change of each segment function is similar to the rate of change of the cam pressure angle. The piecewise functions are then concatenated to form a cam curve with a nonlinear distribution. Then make a one-to-one correspondence between the nonlinearly distributed cam curve and the focal length, zoom group, and compensation group, and jump back to the second step to analyze whether the pressure angle of the nonlinearly distributed cam curve meets the requirements.

If you go directly to the fourth step of focal precision analysis, first analyze whether the output precision of the focal length meets the requirements, and if so, output the result directly; On a basis, further optimize the cam curve with nonlinear distribution. The optimization method is basically the same. The only difference is that it is segmented according to the focal length output accuracy and the function is constructed. After the construction is completed, it is necessary to re-enter the second step to prevent new optimization. The function at has a large influence on the pressure angle.

If the nonlinear cam curve optimization cannot meet the focus output accuracy requirements, or the reason is not caused by the nonlinear cam curve, then it is necessary to optimize the number of teeth of the cam barrel and the parameters of the focusing motor. This optimization method will not The cam curve of the nonlinear distribution has a direct influence, so after the optimization is completed in this way, the results can be output directly if the requirements are met.

In addition, the following clarifications are required for the piecewise function:

There are multiple piecewise functions, and the derivative values and function values at the joints of the piecewise functions are equal, and each piecewise function can be connected into a relatively continuous function.

When the segmental basis of the segmental function is the cam rotation angle, if the cam pressure angle is too large or too small at a certain rotation angle, it can be independently used as a segmental function.

During the construction of the piecewise function, the segmental function corresponding to the position where the pressure angle is too large gives a large amount when re-dividing the cam rotation angle. A small portion corresponds to a reduced rotation angle.

The initial function of the piecewise function comes from the linear construction of the optical zoom output parameters and the cam structure parameters.

A specific example of cam optimization is shown in Figure 2. Taking a three-component optical system as an example, the cam pressure angle suddenly increases at the lower right corner of compensation group 2 (shown by the dotted line in the figure). In order to solve this problem, nonlinear optimization is performed on it, and the optimization function is divided into two sections. The first section still maintains a linear growth, and the second section is a power exponential growth. The optimized result is shown in the solid line in the figure. It can be seen that The zoom group has little change, the pressure angle of compensation group 1 increases slightly, the pressure angle of compensation group 2 increases slightly, and the pressure angle of compensation group 2 decreases obviously.

A specific example of focusing precision optimization is shown in Figure 3. Taking a certain three-element optical system (focal length about 600mm-200mm) as an example, when the rotational arc length is 0, it corresponds to the telephoto position, and when the rotational arc length is the maximum, it corresponds to the short focus position. Location. Among them, the dotted line is the result before optimization, and the solid line is the result after optimization. After optimization, although the output accuracy of short focal length slightly increases, the output accuracy of telephoto decreases significantly, and drops by about 1 times.

Claims (5)

1. a kind of zoom lens zoom cam optimization method, which comprises the following steps:

[1] Optical System Design；

[1.1] focal length, zoom group, the corresponding distance values of compensation group are exported by optical design software；

[1.2] angular displacement of the cam relevant parameter is designed；

[1.3] cam curve of linear distribution is obtained according to step [1.1] and [1.2]；

[2] analysis at cammed compression angle；

The cam curve of linear distribution is analyzed, directly jumps into step [4] if analysis result meets requirement, such as Being unable to satisfy requirement, then to find cammed compression angle excessively most of, is split on this basis to angular displacement of the cam, while quasi- It is standby to enter step [3]；

[3] trend showed according to cammed compression angle carries out piecewise function construction to entire cam, and construction need to meet three Condition:

A, numerical values recited is identical at each section of functional link；

B, differentiation result is identical at each section of functional link；

C, each section of function change rate is similar to cammed compression angular rate of change；

Then piecewise function is connected to the cam curve of one nonlinear Distribution of fitting, then the cam of nonlinear Distribution is bent Line and focal length, zoom group, compensation group are corresponded and are jumped back to the cam of the cam curve of step [2] analysis nonlinear Distribution Whether pressure angle meets requirement；

If meeting requirement, go to step [4]；

If being unsatisfactory for requirement, step [3] are jumped back to again if not optimizing leeway and illustrate the problems in the design, need to jump It returns step [1], optical lens or cam structure is designed again；

[4] focal length output accuracy is analyzed；

Result is directly exported if focal length output accuracy meets requirement；

If focal length output accuracy is unsatisfactory for requirement, need to analyze its Producing reason,

Its reason has two kinds of situations:

Situation one: due to caused by the cam curve of nonlinear Distribution；

Situation two: caused by not being the cam curve of nonlinear Distribution；

For situation one, the cam curve of nonlinear Distribution is advanced optimized, jumps into step [3], optimal way is basic It is identical, only difference is that being segmented according to focal length output accuracy, and constructed fuction, need to reenter after construction complete Step [2]；

For situation two, then need to optimize the number of teeth and the focusing parameter of electric machine of cam canister, after optimization, if meeting the requirements Result can directly be exported.

2. zoom lens zoom cam optimization method according to claim 1, it is characterised in that:

The piecewise function be it is multiple, the junction derivative value of piecewise function is equal and functional value is equal, each piecewise function it Between can connect into a relatively continuous function.

3. zoom lens zoom cam optimization method according to claim 1, it is characterised in that:

When piecewise function segmentation is according to being angular displacement of the cam, cammed compression angle is excessive at certain rotational angle or mistake It is small, it can independently be used as one section of piecewise function.

4. zoom lens zoom cam optimization method according to claim 1, it is characterised in that: the piecewise function construction In the process, the amount given when the excessive corresponding angular displacement of the cam of location segment function of pressure angle is repartitioned is larger, in order to The angle of rotation that compensation pressure angle largely occupies excessively can be subtracted with the corresponding rotational angle of fraction of crossing pressure angle of certain limit It is small.

5. zoom lens zoom cam optimization method according to claim 1, it is characterised in that: the piecewise function rises Beginning function derives from the lineament of optical zoom output parameter and cam structure parameter.