CN107091729A - A kind of focal length of lens method of testing without mechanical movement - Google Patents

Abstract

The present invention proposes a method for testing the focal length of a lens without mechanical movement. The Ronchi grating forms an image on the focal plane of the lens to be tested through a collimator, and the image formed is then imaged through electronically controlled zooming, and finally passed through a microscopic objective lens on the CCD. Get the clearest photos on your camera. To calculate the size of the photo, use the formula The focal length of the lens to be tested is calculated; the invention can realize the automatic detection of the focal length of the lens without mechanical movement, and has the characteristics of convenient detection, high precision, wide testing range and low cost.

Description

A method for testing lens focal length without mechanical movement

technical field

The invention relates to a method for testing the focal length of a lens without mechanical movement, and belongs to the technical field of photoelectric detection.

Background technique

Lens is a widely used optical device, used in various optical systems, the focal length of the lens is its main optical parameter. Whether the focal length of the lens is accurate or not directly affects the performance of the optical system, therefore, many applications require accurate measurement of the focal length.

In traditional focal length measurement, the focal length of a lens or optical system is measured by the magnification method, and the distance between the Porrot plate images is read using an eyepiece micrometer with a microscope. Due to the complexity of the structure of the eyepiece micrometer itself, it is easy to cause imaging instability when the micro-handwheel is rotated during the measurement process, resulting in gyration errors, and because it only relies on the subjective judgment of the operator, it has high requirements for the operator and has a large of human error. At present, image measurement technology is applied to lens focal length measurement, which can realize automatic interpretation and measurement, greatly improve measurement efficiency and measurement accuracy, and avoid human error. However, there are still problems in measuring the focal length of a lens or optical system by the magnification method:

(1) CCD obtains a clear image as the premise of measuring the distance of the Polo plate image. It must move the position of the microscopic shooting system precisely to obtain a clear image. The larger the range of focal length measurement, the farther the distance of mechanical movement. And it must be on the optical axis of the system in the whole moving range. To achieve automatic measurement, a high-precision stepping motor is required, and a high-precision and large-range mechanical motion controllable system is expensive, which will increase the cost of the test system and increase the difficulty of system adjustment.

(2) The currently used Polo plate has three pairs of reticles, which are easy to run out of the field of view during the adjustment process, and the measurement accuracy is not high enough.

Contents of the invention

The object of the present invention is to solve the problems such as difficult adjustment, low measurement accuracy and high cost of the existing lens focal length testing device with the lens focal length test method without mechanical movement. The test method of the present invention can automatically detect the lens focal length quickly and accurately. The detection is convenient, the precision is high, the test range is wide, and the cost is low.

A method for testing the focal length of a lens without mechanical movement, comprising the following steps:

(1) Set the LED light source, Ronchi grating, collimator, lens to be tested, electronically controlled zoom lens and microscope on the test platform in sequence, so that the Ronchi grating, collimator, lens to be tested, electronically controlled zoom lens and The microscope is sequentially set on the outgoing light path of the LED light source;

(2) Control the function generator through the computer terminal to control the voltage applied by the high-voltage amplifier on the electronically controlled zoom lens. The oscilloscope scans the voltage applied to the electronically controlled zoom lens, and sets a step scan of 0.1v for the voltage. Step 0.1v to control the microscope to take a photo, so as to obtain a series of photos;

(3) The computer uses an improved sharpness evaluation function based on grayscale difference to make a difference between the eight fields of pixel I(x, y), and calculate the surrounding points of each photo obtained in step (2). Make a judgment to obtain a photo with the highest definition;

(4) The computer side uses a nonlinear filter median filter method to denoise the photo with the highest resolution obtained in step (3), and then perform image correction processing. The specific steps are:

A. Use the canny operator to detect the edge of the photo. This method uses two thresholds to detect the strong and weak values of the edge;

B. Find the straight line on the edge of the photo;

C. Find the slope of the straight line in step B according to the straight line equation, and calculate the angle between the straight line and the vertical line, which is the inclination angle, and then rotate and correct the photo according to the included angle;

(5) Add the gray value of each column of the corrected photo, take the row of pixels as the horizontal axis, and the gray value of the column as the vertical axis, and use the software to draw the coordinate map; the extreme point is the Ronchi The position of the bright stripes of the grating, and the pixel interval between adjacent bright stripes is the size of the Ronchi grating. Using the software on the computer side to process multiple bright stripes, the size of the image through the microscope objective lens can be obtained, that is, the average value _of y3;

( ₆ ) Substitute y3 into the following formula to obtain the focal length f of the lens to be tested:

In the formula, L, m, V, f ₀ , y ₀ are all known quantities, where: y ₀ is the size of the grating, f ₀ is the focal length of the collimator, m is the magnification of the microscope objective lens, and L is the measured The distance between the lens and the electronically controlled zoom lens, V is the image distance of the electronically controlled zoom lens.

Described in above-mentioned steps (3) do difference value to eight domains of pixel I (x, y), the position of eight neighborhoods is shown in the following formula:

The improved sharpness evaluation function based on gray difference is:

in:

G ₁ ＝|I(x,y)-I(x+1,y)|+|I(x,y)-I(x,y-1)|

G ₂ ＝|I(x,y)-I(x,y+1)|+|I(x,y)-I(x-1,y)|

G ₃ ＝|I(x,y)-I(x-1,y-1)|+|I(x,y)-I(x-1,y+1)|

G ₄ ＝|I(x,y)-I(x+1,y-1)|+|I(x,y)-I(x+1,y+1)|

In the formula: I(x,y) is the gray value of the focus position, I(x+1,y), I(x,y-1), I(x,y+1), I(x-1, y), I(x-1, y-1), I(x-1, y+1), I(x+1, y-1), I(x+1, y+1) and I (x, y) The gray value of the adjacent surrounding 8 pixels. G ₁ , G ₂ , G ₃ , and G ₄ are respectively the sum of the absolute value of the gray difference between I(x, y) and two surrounding pixels.

A test device suitable for a lens focal length test method without mechanical movement includes: an LED light source, a Ronchi grating, a collimator, a lens to be tested, an electronically controlled zoom lens, and a microscope are sequentially arranged on the outgoing light path of the LED light source; The high-voltage amplifier is connected to the control zoom lens, and the high-voltage amplifier is connected to the computer terminal through the function generator, and the function generator is operated on the computer terminal to provide different driving signals for the high-voltage amplifier, thereby driving the focal length of the electronic control zoom lens to be continuously adjustable; the high-voltage amplifier and The oscilloscope is connected to detect the output waveform of the high-voltage amplifier on the oscilloscope; the microscope is connected to the computer, and the computer is installed with software that automatically scans the voltage waveform on the oscilloscope to obtain the driving voltage on the high-voltage amplifier, and processes the image formed by the microscope. software.

Connect the function generator to the high-voltage amplifier to obtain sufficient driving voltage for the zoom lens, and then detect the waveform output from the high-voltage amplifier on the oscilloscope. Connect the function generator and the high-voltage amplifier to the PC through the USB interface to realize automatic voltage adjustment through software. scanning. Connect the CCD camera to the PC through the USB interface, and the image can be processed by software. The size of the microscope image is measured by image measurement technology, the ratio of the image to the object is obtained, and then the focal length of the lens to be tested is obtained without knowing the specific value of the focal length of the electronically controlled zoom lens.

Preferably, the output voltage range of the high voltage amplifier is 0-200 volts. The high-voltage amplifier is used to drive the electronically controlled zoom lens to realize the continuous adjustment of the focal length of the electronically controlled zoom lens, and the test of the lens focal length from negative focus to positive focus can be realized without mechanical movement.

The Ronchi grating acts as a reticle. The Ronchi grating has uniform fringe distribution, the reticle is not easy to run out of the field of view, the adjustment adaptability is strong, and the measurement accuracy can be greatly improved.

Technical effect of the present invention:

The invention greatly simplifies the process of testing the focal length of the lens to be tested, without mechanical movement, the image of the Ronchi grating is formed on the CCD through the lens to be tested and the electronically controlled zoom lens, and the electronically controlled zoom lens is used to automatically zoom and measure on the computer Obtain the clearest imaging on the CCD, take a picture and calculate the size of the photo, and then substitute into the formula to calculate the focal length of the lens to be tested, without knowing the specific focal length of the electronically controlled zoom lens, and adopt the method of the present invention to measure the accuracy very high.

Description of drawings

Fig. 1 is the schematic diagram of the focal length testing device of the non-mechanical movement lens;

Figure 2 is a schematic diagram of the connection between the electronically controlled zoom lens and the computer terminal;

Fig. 3 is the image obtained by CCD and the definition diagram; wherein Fig. 3a is a series of photographs obtained with voltage variation; Fig. 3b is the discrimination of the clearest photo;

Figure 4 is a diagram of the measurement process of the grating size of the clearest image obtained by the CCD; Figure 4a is the clearest photo obtained; Figure 4b is the image correction; Figure 4c is the pixel interval of bright stripes.

detailed description

Principle of the present invention is:

As shown in Figure 1, the size of the Ronchi grating 2 is y ₀ , and the image 5 is formed at the focal plane of the lens under test through the collimator 3 and the lens under test 4, and the image size of the Ronchi grating through the lens under test is y ₁ , and then The electronically controlled zoom lens 6 forms an image 7, the size of the image formed by the zoom lens is y ₂ , and finally the image 9 is formed on the CCD 10 by the microscope objective lens 8, and the size of the image 9 formed on the CCD by the microscope objective lens is y ₃ . When the focal length of the lens to be tested changes, a clear image can be obtained on the CCD by adjusting the driving voltage of the electronically controlled zoom lens. The focal length of the collimator is f ₀ , the focal length of the lens to be tested is f, the focal length of the electronic control zoom lens is f ₁ , the distance between the test lens and the electronic control zoom lens is L, and the object distance and The image distances are U and V respectively, and the magnification of the microscope objective is m.

According to the principle of magnification method, we can know that:

From the imaging of the convex lens, it can be seen that:

It can be seen from the microscope imaging that:

From (1), (2), (3) can get:

It can be seen from Figure 1 that:

U=L-f (5)

Substitute (5) into (4) to get:

The size y ₀ of the Ronchi grating is determined by the specification of the grating and is a known quantity; the focal length f ₀ of the collimator is determined by the specification of the collimator and is a known quantity; the magnification m of the microscope objective lens is determined by the microscope It is determined by the model, which is a known quantity; the method to obtain L, m, V is: use the lens to be tested with known focal length to perform the above operations, and when a clear image is obtained on the CCD, the size y ₃ of the image is obtained. At this time ( 6) In the formula, f, m, f ₀ , y ₀ , and y ₃ are all known, and the above operations are performed with a plurality of lenses to be measured with known focal lengths, and the equations for calculating L and V are obtained, and L and V are calculated, and The L, V are constants.

For example, the collimator focal length f ₀ is 500mm, y ₀ is 0.2mm, the electric control zoom lens is the Arctic316 zoom lens produced by varioptie company, and the selected CCD camera is Daheng MER-125-30UM/UC-L series Digital camera, single pixel size is 3.75μm×3.75μm, m is taken as 10, and two standard lenses with known focal lengths of 40mm and 120mm are used to calibrate. According to the above method, y3 is measured to be 33.37 and _200.5 pixel intervals respectively, and L is 200mm and V is 50mm.

Therefore, L, m, V, f ₀ , and y ₀ in formula (6) are all known, so the focal length f of the lens to be measured can be obtained by measuring y ₃ imaged in the CCD.

As shown in Figure 2, build an electronically controlled zoom lens system and an image processing system. Connect the function generator to the high-voltage amplifier to obtain sufficient driving voltage for the zoom lens, and then detect the waveform output from the high-voltage amplifier on the oscilloscope. Connect the function generator and the high-voltage amplifier to the PC through the USB interface to realize automatic voltage adjustment through software. scanning. Connect the CCD camera to the PC through the USB interface, and the image can be processed by software.

In order to measure the focal length of the lens to be tested, it can be seen from formula (6) that it is only necessary to measure the grating size y3 _of the microscopic imaging, and y3 can be obtained by processing the clearest photos taken _on the CCD camera.

As shown in Figures 1 and 2, a lens focal length testing device without mechanical movement includes: an LED light source, a Ronchi grating, a collimator, a lens to be tested, an electronically controlled zoom lens, and a microscope, which are sequentially arranged on the outgoing light path of the LED light source The electronically controlled zoom lens is connected to a high-voltage amplifier, the high-voltage amplifier is connected to the computer terminal through a function generator, and the function generator is operated on the computer terminal to provide different driving signals for the high-voltage amplifier, thereby driving the continuously adjustable focal length of the electronically controlled zoom lens The high-voltage amplifier is connected with the oscilloscope, and the waveform output by the high-voltage amplifier is detected on the oscilloscope; the microscope is connected to the computer terminal, and the computer terminal is installed with software that automatically scans the voltage waveform on the oscilloscope to obtain the driving voltage on the high-voltage amplifier, and the result of the microscope. Image processing software.

A method for testing the focal length of a lens without mechanical movement, comprising the following steps:

(1) Set the LED light source, Ronchi grating, collimator, lens to be tested, electronically controlled zoom lens and microscope on the test platform in sequence, so that the Ronchi grating, collimator, lens to be tested, electronically controlled zoom lens and The microscope is sequentially set on the outgoing light path of the LED light source;

(2) Control the function generator through the computer terminal to control the voltage applied by the high-voltage amplifier on the electronically controlled zoom lens. The oscilloscope scans the voltage applied to the electronically controlled zoom lens, and sets a step scan of 0.1v for the voltage. Step 0.1v to control the microscope to take a picture, so as to obtain a series of pictures, as shown in Figure 3a;

(3) The computer uses an improved sharpness evaluation function based on grayscale difference to make a difference between the eight fields of pixel I(x, y), and calculate the surrounding points of each photo obtained in step (2). Make a judgment to obtain a photo with the highest definition; the traditional gray-scale difference evaluation function only makes a difference in the horizontal and vertical directions of the gray-scale value. The improved gray-scale difference function performs the difference on the eight fields of the pixel I(x, y), which increases the judgment of surrounding points and improves the accuracy of obtaining clear images. The eight domains of the pixel I(x, y) are differenced, and the positions of the eight neighbors are shown in the following formula:

The improved sharpness evaluation function based on gray difference is:

in:

G ₁ ＝|I(x,y)-I(x+1,y)|+|I(x,y)-I(x,y-1)|

G ₂ ＝|I(x,y)-I(x,y+1)|+|I(x,y)-I(x-1,y)|

G ₃ ＝|I(x,y)-I(x-1,y-1)|+|I(x,y)-I(x-1,y+1)|

G ₄ ＝|I(x,y)-I(x+1,y-1)|+|I(x,y)-I(x+1,y+1)|

In the formula: I(x,y) is the gray value of the focus position, I(x+1,y), I(x,y-1), I(x,y+1), I(x-1, y), I(x-1, y-1), I(x-1, y+1), I(x+1, y-1), I(x+1, y+1) and I (x, y) The gray value of the adjacent surrounding 8 pixels. G ₁ , G ₂ , G ₃ , and G ₄ are respectively the sum of the absolute value of the gray difference between I(x, y) and two surrounding pixels.

The sharpness evaluation function can automatically obtain clear images and is real-time. The acquired photos are calculated through the image sharpness discrimination function to obtain the clearest photos, as shown in Figure 3b.

(4) The computer side uses a nonlinear filter median filter method to denoise the photo with the highest resolution obtained in step (3), and then perform image correction processing. The specific steps are:

A. Use the canny operator to detect the edge of the photo. This method uses two thresholds to detect the strong and weak values of the edge; after multiple verifications by the system, the canny operator can accurately extract the edge, and the effect can meet the requirements of the experimental system.

B. Find the straight line on the edge of the photo; as shown in Figure 4a.

C. Find the slope of the straight line in step B according to the straight line equation, and calculate the angle between the straight line and the vertical line, which is the inclination angle, and then perform rotation correction on the photo according to the included angle; the corrected photo is shown in Figure 4b Show.

(5) Add the gray value of each column of the corrected photo, take the row of pixels as the horizontal axis, and the gray value of the column as the vertical axis, and use the software to draw the coordinate map, as shown in Figure 4c; The value point is the position of the bright stripes of the Ronchi grating, and the pixel interval between adjacent bright stripes is the size of the Ronchi grating. Using the software on the computer side to process multiple bright stripes, the size of the image imaged by the microscope objective lens can be obtained, namely mean _of y3;

The Ronchi grating is more precise, and the engraving error is very small, and the center line of each bright line has the largest gray value. Using software to process multiple bright stripes, the average value _of y3 can be obtained, thereby reducing the error.

( ₆ ) Substitute y3 into the following formula to obtain the focal length f of the lens to be tested:

In the formula, L, m, V, f ₀ , y ₀ are all known quantities, where: y ₀ is the size of the grating, f ₀ is the focal length of the collimator, m is the magnification of the microscope objective lens, and L is the measured The distance between the lens and the electronically controlled zoom lens, V is the image distance of the electronically controlled zoom lens.

Replace the lens to be tested in the above method with a standard lens whose focal length is known to be 40 mm and 120 mm, and measure y3 according to the above method to be 33.37 and _200.5 pixel intervals respectively, and calculate the measured values of the lens according to the above formula (6), respectively are 40.034mm and 120.12mm, it can be seen that the measurement accuracy by the method of the present invention is very high, being 0.085% and 0.1% respectively.

Claims (4)

1. a kind of focal length of lens method of testing without mechanical movement, it is characterised in that comprise the following steps：

(1) LED/light source, Ronchi grating, parallel light tube, lens to be measured, electric control varifocal lens and microscope are successively set on survey Try on platform, Ronchi grating, parallel light tube, lens to be measured, electric control varifocal lens and microscope is successively set on LED/light source On emitting light path；

(2) by computer end control function generator, so that control high-voltage amplifier to be applied to the voltage on electric control varifocal lens, Oscillograph is scanned to the voltage being applied on electric control varifocal lens, and 0.1v step-scan is set to voltage, per stepping 0.1v just controls microscope to take a picture, so as to obtain a series of photos；

(3) computer end utilizes a kind of improved sharpness evaluation function based on grey scale difference, to pixel I (x, y) eight fields Difference is done, to point judges around each photo of acquisition in step (2), so as to obtain one photograph of definition highest Piece；

(4) computer end utilizes a kind of nonlinear filter median filtering method, to the definition highest one obtained in step (3) Photo carries out denoising, then carries out the correction process of image, concretely comprises the following steps：

A, using canny operators the edge of photo is detected, this method using two threshold test edges strong and weak value；

B, the straight line for finding its edges；

C, the slope for obtaining according to linear equation step B cathetus, and the angle between straight line and vertical line is calculated, as tilt Angle, then carries out rotation correction according to this angle to photo；

(5) gray value of each row of photo after correction is added, using the row of pixel as transverse axis, the gray value of row is as vertical Axle, the coordinate diagram drawn with software；Extreme point is Ronchi grating bright fringes position, and the pixel separation of adjacent bright fringes is The size of Ronchi grating, is handled a plurality of bright fringes with the software of computer end, can obtained through microcobjective imaging Size, i.e. y₃Average value；

(6) by y₃Focal length of lens f to be measured can be tried to achieve by substituting into following formula：

<mrow> <mi>f</mi> <mo>=</mo> <mfrac> <mi>L</mi> <mrow> <mo>(</mo> <mn>1</mn> <mo>+</mo> <mfrac> <mrow> <msub> <mi>mVy</mi> <mn>0</mn> </msub> </mrow> <mrow> <msub> <mi>f</mi> <mn>0</mn> </msub> <msub> <mi>y</mi> <mn>3</mn> </msub> </mrow> </mfrac> <mo>)</mo> </mrow> </mfrac> </mrow>

L in formula, m, V, f₀, y₀, it is known quantity, wherein：y₀For raster size, f₀For the focal length of parallel light tube, m is microcobjective Magnifying power, L is the distance of lens to be measured and electric control varifocal lens, and V is the image distance being imaged through electric control varifocal lens.

2. a kind of focal length of lens method of testing without mechanical movement according to claim 1, it is characterised in that step (3) Described in eight fields to pixel I (x, y) do difference, the position of eight neighborhood is shown below：

<mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <mi>x</mi> <mo>-</mo> <mn>1</mn> <mo>,</mo> <mi>y</mi> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow> </mtd> <mtd> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <mi>x</mi> <mo>,</mo> <mi>y</mi> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow> </mtd> <mtd> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <mi>x</mi> <mo>+</mo> <mn>1</mn> <mo>,</mo> <mi>y</mi> <mo>+</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <mi>x</mi> <mo>-</mo> <mn>1</mn> <mo>,</mo> <mi>y</mi> <mo>)</mo> </mrow> </mrow> </mtd> <mtd> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <mi>x</mi> <mo>,</mo> <mi>y</mi> <mo>)</mo> </mrow> </mrow> </mtd> <mtd> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <mi>x</mi> <mo>+</mo> <mn>1</mn> <mo>,</mo> <mi>y</mi> <mo>)</mo> </mrow> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <mi>x</mi> <mo>-</mo> <mn>1</mn> <mo>,</mo> <mi>y</mi> <mo>-</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow> </mtd> <mtd> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <mi>x</mi> <mo>,</mo> <mi>y</mi> <mo>-</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow> </mtd> <mtd> <mrow> <mi>I</mi> <mrow> <mo>(</mo> <mi>x</mi> <mo>+</mo> <mn>1</mn> <mo>,</mo> <mi>y</mi> <mo>-</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow> </mtd> </mtr> </mtable> </mfenced>

The improved sharpness evaluation function based on grey scale difference is：

<mrow> <mi>F</mi> <mo>=</mo> <munderover> <mo>&amp;Sigma;</mo> <mrow> <mi>M</mi> <mo>/</mo> <mn>2</mn> <mo>-</mo> <mn>50</mn> </mrow> <mrow> <mi>M</mi> <mo>/</mo> <mn>2</mn> <mo>+</mo> <mn>50</mn> </mrow> </munderover> <munderover> <mo>&amp;Sigma;</mo> <mrow> <mi>N</mi> <mo>/</mo> <mn>2</mn> <mo>-</mo> <mn>50</mn> </mrow> <mrow> <mi>N</mi> <mo>/</mo> <mn>2</mn> <mo>+</mo> <mn>50</mn> </mrow> </munderover> <mo>{</mo> <msub> <mi>G</mi> <mn>1</mn> </msub> <mo>+</mo> <msub> <mi>G</mi> <mn>2</mn> </msub> <mo>+</mo> <msub> <mi>G</mi> <mn>3</mn> </msub> <mo>+</mo> <msub> <mi>G</mi> <mn>4</mn> </msub> <mo>}</mo> </mrow>

Wherein：

G₁=| I (x, y)-I (x+1, y) |+| I (x, y)-I (x, y-1) |

G₂=| I (x, y)-I (x, y+1) |+| I (x, y)-I (x-1, y) |

G₃=| I (x, y)-I (x-1, y-1) |+| I (x, y)-I (x-1, y+1) |

G₄=| I (x, y)-I (x+1, y-1) |+| I (x, y)-I (x+1, y+1) |

In formula：I (x, y) be focal position gray value, I (x+1, y), I (x, y-1), I (x, y+1), I (x-1, y), I (x-1, Y-1), I (x-1, y+1), I (x+1, y-1), I (x+1, y+1) are respectively the gray scale of 8 pixels around adjacent with I (x, y) Value.G₁、G₂、G₃、G₄Respectively I (x, y) and two pixels of surrounding grey scale difference absolute value sum.

3. a kind of focal length of lens method of testing without mechanical movement according to claim 1, it is characterised in that the test side The applicable test device of method includes：LED/light source, Ronchi grating, parallel light tube, lens to be measured, electric control varifocal lens and microscope It is successively set on the emitting light path of LED/light source；High-voltage amplifier is connected on the electric control varifocal lens, high-voltage amplifier passes through Function generator is connected to computer end, provides different drive signals for high-voltage amplifier in computer end handling function generator, So as to drive the focal length continuously adjustabe of electric control varifocal lens；High-voltage amplifier is connected with oscillograph, and high pressure is detected on oscillograph The waveform of amplifier output；Microscope is connected to computer end, computer end be provided with voltage waveform on automatically scanning oscillograph, from And obtain the software of driving voltage on high-voltage amplifier, and to microscope the software that is handled into image.

4. a kind of focal length of lens method of testing without mechanical movement according to claim 1, it is characterised in that high voltage amplifier Device output voltage range lies prostrate for 0-200.