Introduction：

Electronic speckle-Shearing pattern interferometry is a new laser interference measuring technology which used to measuring off-plane displacement derivative field .It no only have many advantage of electronic speckle pattern interferometry ,but also have the advantage of optical path simple and have low requirement of measuring environment .Because the shear Electronic speckle pattern interferometry is used to measuring displacement derivative, therefore it is sensitive to defect loading of strain concentration when automatically eliminate the displacement of rigid body .So it is widely used in the area of nondestructive testing (NDT) This instrument use high-power green semiconductor laser as the light source .with the real-time processing software of electronic speckle pattern fringe, easy to operate and carry, can be used for locale measurement. Use phase-shift technology to analyze stripes, can the whole field date of the off-plane displacement derivatives field. 

Product model：TS-SS-P

Main Technical Specification and Dispositions：

Main Technical Specification：
1.Light source: Semiconductor laser (Green light) output power is 50mW, Wavelength is 532nm 

2. Focus lens: C interface lens, with 25mm focus lens

3.Camera：1280×1024 USB2.0 digital camera

4.Working Distance：400～1000mm

5. optical platform: 600mm×900mm

6. Image acquisition resolution: 1280×1024

7.Real-time stripe display speed: 25f/s

8.shear angle: 0°±5°continuously tunable

9.Software:  Fringe real-time display software, phase shift software

10. Demonstration specimen: uniformity load-bearing disc

11. Phase shifter：10nm

12. Phase shift control precision: 0.01V

Major Dispositions

Mainframe:1

25mm focus lens:1

50mW solid-state laser:1

400mm*900mm optical platform :1 set

Tripod:1

Phase shifter:1 set

Uniformity load-bearing disc specimen:1 set

Laptop:1

Fringe real-time display software, phase shift software: one set for each

Principle Diagram：

The basic principle of stereography is a combination of speckle photography and shear mechanism, which is based on the speckle photography,

By staggering the difference elements, the single-beam speckle into dual-beam speckle, consequently it has the characteristics of dual-beam speckle, i.e. it will produce interference between the original wave front and the dislocation wave front.

The principle of off-plane displacement gradient measurement is shown in Figure 2. The speckle field of object A after passed through shear-prism, polarizer and CCD objective will form two images of Δ dislocation and interference in the CCD target surface.

Displacement speckle light path

Displacement speckle interferometry optical path diagram

Operation Method:

A uniform white light as the light source irradiates on the surface of the measured object .in order to facilitate observation, we past the calibration paper (shown with "+" word) on the surface of the measured object. Adjusting  the object distance in order to make image clear while we observe the computer display screen, and then let the cross switch which is in optical path of the dislocation prism .

Close the white light source and open the laser power supply in order to have laser light. Adjust the extender lens, let the light uniform diffused on the surface of the specimen, and then take the calibration paper witch on the specimen away. we can get the off- plane displacement derivatives of the image after real-time subtraction between interference images before and after deformation.

Test case: aluminum honeycomb panel laser speckle detection experiments

This experiment has a honeycomb panel with aluminum honeycomb panel, has bought a thickness of 17.45 mm and 8.5 mm of honeycomb panel, 14.5 mm thick aluminum honeycomb panel size is: length (150 mm); Width (100 mm), has set a good outside. 8.5 mm thick aluminum honeycomb panel size is: length (250 mm); Width (200 mm), not with outside. As shown in figure:

The experimental steps:

1. Adjust the equipment to normal working state;

2. The honeycomb sandwich plate is fixed in the experimental stage, laser laser after beam expander beam expander from full cover sandwich board, adjust the shearing speckle position, make the CCD vision clear and complete coverage sandwich board;

3. With the method of heat load, heat source for high-power hair dryer, heating the honeycomb panel away from the surface micro deformation;

4. Natural cooling at room temperature, the cooling process of speckle interference fringe figure.

The experimental results and analysis

1, 14.5 mm thick aluminum honeycomb panel experimental results

You can see that the defective parts and not tested. From this analysis may be due to the honeycomb panel is too thick, or honeycomb paper and aluminum plate connection glue is too thin, cause even if removed honeycomb paper and aluminum plate connection, the result is not significantly affected. Therefore, the experimental results is not obvious.

2, 8.5 mm thick aluminum honeycomb panel experimental results

(1) in this part to the honeycomb panel produced for the defect of 33 mm long, measured graphics for: 

(2) in graphic parts to 48 mm honeycomb panel to create defects, measured graphics for:

After the two test results contrast, for honeycomb panel thickness is thinner, the experimental effect is obvious.

Note: if you want to would be able to detect the defect of the object under test, to meet upon loading (mechanical, thermal, high load audio or vacuum) material can produce not only from the surface displacement, and defects on both sides of the material to be able to produce from the surface displacement in different degrees, to detect the defect parts, size.

Range of application：

General surface deformation measurement; From the surface displacement measurement; In-plane strain measurement; Residual stress measurement; Defect detection; The sealing situation assessment; Gas leak detection...