CN101246263A - Double crosshair reticle for detecting shake of boresight of zoom lens and method of use - Google Patents

Abstract

The invention relates to a method for making and using a double cross reticle for detecting shaking of the visual axis of a zoom lens. In order to solve the measurement problem of boresight shake of the zoom lens with a large zoom ratio, a concentric double crosshair reticle is designed. In the center of the reticle, two concentric crosshairs are drawn. The width and length of the large crosshairs The width and length ratio of the small reticle is equal to the zoom ratio of the lens; the small reticle is completely blackened, the color of the large reticle is lighter, and the gray scale is 1/3-1/2 of the small reticle; Use the reticle to locate the boresight center of the long focal length, and use the light-colored large reticle to locate the boresight center of the short focal length to obtain high-precision detection results of boresight shake of the zoom lens. It solves the detection of the shaking of the boresight of the zoom lens with a large zoom ratio that cannot be realized by the conventional method. Through practical application, the correctness and feasibility of the detection tool and detection scheme are proved. Moreover, the tool is simple, easy to use, low in cost, and of considerable value.

Description

Double crosshair reticle for detecting shake of boresight of zoom lens and method of use

Technical field:

The invention relates to a detection tool used in the fields of optical adjustment and optical detection, that is, a reticle for detecting shaking of the visual axis of a zoom lens and a use method thereof.

Background technique:

The shaking of the boresight of the zoom lens before and after the focal length change will cause the position of the image in the field of view to change. If the boresight target deviates from the central field of view, it will affect high-precision measurement or TV tracking. Therefore, during the design, assembly and testing process of the zoom lens, the boresight shake should be controlled within a certain tolerance range.

A conventional method for detecting boresight shake of a zoom lens requires the following steps. (see picture 1)

first step:

As shown in Figure 1, arrange the detection collimator, the zoom lens to be detected, and the reading microscope to be coaxial, and place the crosshair reticle on the focal plane of the detection collimator, and the zoom lens projects the image of the crosshair reticle onto the image plane of the zoom lens.

The second step:

Adjust the zoom lens to be tested to telephoto, and fine-tune the position of the reading microscope so that the center image of the reticle reticle of the detection collimator coincides with the center of the reticle of the reading microscope, and record the position of the reading microscope when the lens is at a long focal length (x ₁ , y ₁ ).

The third step:

Adjust the focal length of the lens to short focal length, repeat the second step, and record the reading microscope position (x ₂ , y ₂ ) when the lens is in short focal length.

The fourth step:

The distance between the position (x ₁ , y ₁ ) and the position (x ₂ , y ₂ ) is the amount of boresight shake of the long and short focus of the zoom lens, which is converted into an angle according to the following formula:

(弧度)1)

(radian)1)

For a conventional zoom lens with a relatively small zoom ratio, the crosshair reticle can clearly image both the long and short focal lengths of the lens, and it is easy to measure the center position of the crosshair image. Problems arise when the boresight of a focal length lens wobbles, as shown in Figure 2.

$\frac{\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

H: Detect the line width of the reticle on the focal plane of the collimator

h: line width of the crosshair image on the focal plane of the zoom lens

F: Detect the focal length of the collimator

f: zoom lens focal length

can launch:

$\frac{{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; h</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

h ₁ : reticle line width at telephoto,

h ₂ : Reticle line width at short focus,

f ₁ : long focal length of the lens,

f ₂ : short focal length of the lens,

That is, the line width ratio of the crosshair image on the focal plane of the zoom lens is equal to the focal length change ratio of the zoom lens. Assuming that the focal length change ratio of the zoom lens is 15 to 30 times, the image formed by the crosshair reticle of the detection collimator when the focal length of the lens is zoomed is clear. The line width of the reticle image is moderate, and the center of the reticle image is the center of the telephoto boresight of the zoom lens.

After zooming, according to the formula 3), the image of the reticle is reduced by 15-30 times, and the line width of the reticle is also reduced by 15-30 times. Because the line width of the reticle is too thin, the reticle is too small and long 1. The huge change of the image width of the short focal length leads to the fact that although the crosshair image can be clearly seen at the long focal length, the crosshair image cannot be observed at the short focal length, and the center of the short focal length visual axis cannot be measured.

Detect the shake of the boresight of the zoom lens with higher zoom ratio, because the gap between the long and short focal lengths is larger, and the contradiction of seeing the reticle image at the same time is more irreconcilable.

Replacing a microscope objective lens or eyepiece with a higher magnification can enlarge the image of the crosshair reticle at short focus, but it may cause the position of the reading microscope to change, resulting in a change in the visual axis, bringing new error sources, and reducing the visual axis of the zoom lens Shaking detection accuracy, so this method should not be used.

Invention content:

In order to solve the problem that the reticle image cannot be seen clearly at the same time in the process of detecting the shaking of the visual axis of the zoom lens with high zoom ratio in the background technology, the present invention specially makes a concentric double reticle reticle. Draw two concentric crosshairs, the length, width and grayscale of the two crosshairs will vary.

Use one set of crosshairs to locate the center of the boresight of the long focal length, and another set of crosshairs to locate the center of the boresight of the short focal length. The whole process does not need to replace the microscope lens, which is conducive to obtaining high-precision detection results of the boresight shake of the zoom lens. Therefore, the present invention will provide a method for making and using a crosshair reticle for detecting shaking of the boresight of a zoom lens with a high zoom ratio.

The specific structure of reticle reticle of the present invention is as follows:

See Figure 3. First, determine the center of the reticle and mark two concentric crosshairs. The non-concentricity error is determined by the detection accuracy of the boresight shake of the zoom lens, generally 0.001mm.

The ratio of the width and length of the large reticle to the width and length of the small reticle is equal to the zoom ratio of the lens; the small reticle is completely blackened, the color of the large reticle is lighter, and the gray scale is about 1/3 of the small reticle.

According to the routine detection method of boresight shake of zoom lens, there are 4 steps to detect,

First, use the dark small reticle to locate the center of the long focal length visual axis. At this time, the light-colored large reticle does not affect the microscope observation of the dark small reticle.

When switching to the short focal length of the lens, the small dark reticle cannot be observed with a microscope due to its small size, while the large light reticle becomes clearer due to the reduced image height. Use it to locate the center of the short focal length visual axis and complete the detection change The boresight of the focal length lens shakes.

Advantages of the present invention: the present invention proposes a visual axis shake detection tool and a using method of a zoom lens with relatively large magnification ratio. Through the special concentric double reticle reticle, use the large and small reticle with the same central position at the long and short focal lengths to determine the change of the visual axis of the zoom lens. It solves the detection of the shaking of the boresight of the zoom lens with a large zoom ratio that cannot be realized by the conventional method. The embodiment of the present invention proves the correctness and feasibility of the detection tool and the detection scheme through the actual application in the measurement of a zoom lens. Moreover, the tool is simple, easy to use, low in cost, and of considerable value.

Description of drawings:

Figure 1 Schematic diagram of the arrangement of the boresight shake of the zoom lens: in the figure, the collimator 1, the zoom lens to be inspected 2, the reading microscope 3, the human eye 4,

Figure 2 Schematic diagram of double crosshair imaging:

H: Detect the line width of the reticle on the focal plane of the collimator

h: line width of the crosshair image on the focal plane of the zoom lens

F: Detect the focal length of the collimator

f: zoom lens focal length

Fig. 3 schematic diagram of concentric double reticle reticle of the present invention

Detailed ways:

Embodiments of the present invention are shown in Fig. 1, Fig. 2, Fig. 3, 550mm collimator 1, the zoom lens 2 to be inspected of 25 times zoom ratio, reading microscope 3, human eye 4, crosshair line width 5, crosshair line Like width 6.

The embodiment of the present invention is arranged according to Fig. 1, and the zoom lens 2 to be inspected of 550mm collimator 1, 25 times zoom ratio, reading microscope 3 and human eye 4 are arranged in a straight line.

first step:

On the focal plane of the detection collimator 1, a concentric double crosshair reticle is placed, and the zoom lens 2 projects the image of the concentric double crosshair reticle onto the image plane of the zoom lens 2;

The second step:

Adjust the detected zoom lens 2 to telephoto, and fine-tune the position of the reading microscope 3. First, use the dark small reticle to locate the center of the long focal length visual axis. At this time, the light reticle will not affect the observation of the microscope. The reading microscope 3 position (x ₁ , y ₁ ) when the lower lens is at a long focal length;

The third step:

Adjust the focal length of the zoom lens 2 to short focal length, and repeat the second step. When switching to the short focal length of the lens, the small dark reticle cannot be observed by microscope 3 because of its small size, while the large light reticle becomes more and more blurred due to the reduced image height. Clear, use it to locate the center of the boresight of the short focal length, and record the reading microscope 3 position (x ₂ , y ₂ ) when the lens is at the short focal length;

The fourth step:

The distance between the position (x ₁ , y ₁ ) and the position (x ₂ , y ₂ ) is the amount of boresight shake of the long and short focus of the zoom lens, which is converted into an angle according to the following formula:

(弧度)1)。

(radian) 1).

Claims (3)

1. A double crosshair reticle for detecting shaking of the visual axis of a zoom lens, characterized in that: two concentric crosshairs are drawn in the center of the reticle to make a concentric double crosshair reticle; The ratio of the width and length of the large reticle to the width and length of the small reticle is equal to the zoom ratio of the lens; The small crosshair is completely blackened, the color of the large crosshair is lighter, and the grayscale is 1/3-1/2 of the small crosshair; 2. according to claim 1, a kind of double cross reticle for detecting the shake of the boresight of the zoom lens is characterized in that the non-concentricity error of the concentric double cross reticle is determined according to the shaking detection accuracy of the boresight of the zoom lens, Generally take 0.0005mm-0.001mm. 3. A method of using a double crosshair reticle for detecting shaking of the boresight of a zoom lens, characterized in that the method of using the concentric double crosshair reticle: first step: Arrange the detection collimator, the detected zoom lens, and the reading microscope to be coaxial, and place the concentric double reticle reticle on the focal plane of the detection collimator, and the zoom lens projects the image of the concentric double reticle onto the zoom lens. The image plane of the focal length lens; The second step: Adjust the zoom lens to be tested to telephoto, and fine-tune the position of the reading microscope. First, use the small dark crosshair to locate the center of the long focal length boresight, and record the position of the reading microscope when the lens is at the long focal length (x ₁ , y ₁ ); The third step: Adjust the focal length of the lens to the short focal length. The small dark reticle cannot be observed with a microscope due to its small size, while the large light reticle becomes clearer due to the reduced image height. Use it to locate the center of the short focal length visual axis and record the lens Reading microscope position (x ₂ , y ₂ ) at short focal length; The fourth step: The distance between the position (x ₁ , y ₁ ) and the position (x ₂ , y ₂ ) is the amount of boresight shake of the long and short focus of the zoom lens, which is converted into an angle according to the following formula:

(radian) 1).

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