{"id":47732,"date":"2021-03-18T13:19:19","date_gmt":"2021-03-18T17:19:19","guid":{"rendered":"https:\/\/seniordesign.digitalscholar.rochester.edu\/ece2021\/?p=84"},"modified":"2022-04-13T11:58:44","modified_gmt":"2022-04-13T15:58:44","slug":"non-contact-video-extensometer","status":"publish","type":"post","link":"https:\/\/www.hajim.rochester.edu\/senior-design-day\/non-contact-video-extensometer\/","title":{"rendered":"High Accuracy Displacement Measurement"},"content":{"rendered":"\n

<\/p>\n\n\n\n

Introduction<\/h2>\n\n\n\n

This project aims to measure small displacement with low cost but high accuracy. With only a magnified usb camera and a PC, the software can measure the displacement in micrometers. <\/p>\n\n\n\n

<\/p>\n\n\n\n

Set Up<\/h2>\n\n\n\n

An USB magnified camera, a PC, and a linear stage are used. <\/p>\n\n\n\n

\"\"<\/figure><\/div>\n\n\n\n

Camera<\/em><\/h4>\n\n\n\n

The USB magnified camera are used to capture videos for measurement. Videos will be processed by python which can work for both windows and IOS systems. In order to reach high precision measurement, we ordered digital microscope instead of normal one, so that it can capture more details and smaller range of sight. Also, digital microscopes are about only $30 ~ $50, so it’s really cheap and highly affordable for the high accuracy measurement.<\/p>\n\n\n\n

Also, as shown in the picture, the camera is placed in several boxes in order to make the camera parallel to the moving of the linear stage. This parallel placement can reduce angular distortions caused by a tilted camera, and therefore reduce calculated error in the end.<\/p>\n\n\n\n

Linear Stage<\/em><\/h4>\n\n\n\n

The linear stage is for compare and contrast. With the precision of 0.01 mm, the linear stage can move precisely and its movement will be counted as the real movement values. The movement of the linear stage will be tracked and measured by the software. All the precision rates are calculated through the difference between real values and the estimated values.<\/p>\n\n\n\n

For the convenience of test, a white paper is placed above the linear stage and will be moved together. This step is to keep the background of frames clean such that the software can track a distinct dot on it. As long as there are no other obvious lines or objects besides, the shape and size of dots will be perfectly recognized. <\/p>\n\n\n\n

<\/p>\n\n\n\n

User Interface<\/h2>\n\n\n\n

The software is developed through Python. Here is an example:<\/p>\n\n\n\n

\"\"<\/figure>\n\n\n\n

The “start” and “stop” buttons are used to start and stop recording. Whenever the “start” is clicked, the camera will tract the point shown in the frames captured, and record its coordinate. Whenever the “stop” is clicked, the camera will stop tracking the point, and record its coordinate after move. The change of coordinate will be converted to centimeters in the real world. <\/p>\n\n\n\n

<\/p>\n\n\n\n

Tic Control for the Linear Stage<\/em><\/h4>\n\n\n\n
\"\"<\/figure>\n\n\n\n

In order to control the linear stage, the Pololu Tic Control Center is used. This software is provided by Pololu<\/a>. The linear stage has 25000 steps and, for its 250 mm length, each step indicate 0.01 mm. <\/p>\n\n\n\n

The video below shows how these two software worked.<\/p>\n\n\n\n