Optical lineation scale works on the basis of Moire fringe formation principle. Moire fringe is a stripe of light and dark which is formed by crossing the lines on two grating scales under the irradiation of light source. These fringes have an amplification effect and can eliminate the effect of uneven grating spacing.
The formation of Moire stripes
When the line pattern on the indicating grating is placed at an Angle to the line pattern on the ruler grating, the line pattern on the two ruler will inevitably cross each other. Under the irradiation of the light source, due to the overlapping of black lines in the small area near the intersection point, the shading area is the smallest, the blocking effect is the weakest, and the cumulative effect of light makes this area appear bright band. On the contrary, the area farther from the intersection point, because the overlap of the opaque black lines of the two grating rules becomes less and less, the area of the opaque area gradually becomes larger, that is, the shading area gradually becomes larger, making the blocking effect stronger, only less light can pass through this area through the grating, so that this area appears dark band. These are almost perpendicular to the raster lines, and the alternating light and dark bands are Moire stripes.
Characteristics of Moire fringe
Amplification: When the grating is illuminated with a parallel beam, the distribution of light intensity through the moire fringe approximates the cosine function. Without the need of complex optical and electronic systems, the grating distance can be converted into the width of Moire fringes magnified several times by using the interference phenomenon of light.
Average effect: The Moire fringe is formed by the common interference of several grating lines, so the Moire fringe has an average effect on the grid distance error between individual grating lines, and can eliminate the influence caused by the uneven grating distance.
Moving correspondence: The movement of the Moire fringe corresponds to the relative movement between the two grating scales. When the two grating scales move relative to each other by a grating distance d, the Moire fringe moves correspondingly by a Moire fringe width W, the direction of which is perpendicular to the direction of the two grating scales moving relative to each other.
The calibration of optical linear scale is an important step to ensure its measuring accuracy. Here are the detailed calibration steps:
Preparatory work
Place the optical wire gauge horizontally or straight on the work surface.
Adjust the lens of the image measuring instrument to make the focal length clear.
First measurement
Adjust the image measuring instrument so that a certain scale line of the line measuring instrument is within the visual field of the image measuring instrument.
Record the corresponding coordinates of the scale line in the imaging window.
Second measurement
Adjust the image-measuring instrument again so that another scale of the line scale, such as an adjacent scale, is within the visual field of the image-measuring instrument.
Record the corresponding coordinates of the scale line in the imaging window.
Calculate the linear compensation coefficient
Calculate the corresponding length H of the image measuring instrument according to the coordinates of the two measurements.
According to the relationship between the practice scale L of the standard scale and the length H, the linear compensation coefficient a of the image measuring instrument is obtained, a=L/H.
Calibration of image measuring instruments
According to the linear compensation coefficient, any point in the image measuring instrument is corrected to obtain the corresponding coordinates after correction.
The operation steps of the optical line ruler are relatively simple, but attention to detail is required to ensure measurement accuracy. Here are the detailed steps:
Preparatory work
Ensure that the working environment is clean and free from vibration and interference.
Install the optical wire gauge on the measuring device and secure it.
Turn on device
Turn on the power supply of the measuring device and start the measuring system.
Adjust the parameters of the measuring equipment, such as focal length, light source brightness, etc., to meet the measurement needs.
Place the object under test
Place the object to be measured on the measuring platform and ensure its position is accurate.
Use a fixture or positioning device to hold the object in place and avoid movement.
Start measuring
Move the measuring head of the measuring device so that it touches the measuring point of the measured object.
Read the scale value of the measuring head on the optical wire scale and record it.
Data processing
According to the measured data, the length, diameter and other parameters of the measured object are calculated.
Analyze the error of measurement data to ensure the accuracy of measurement results.
End measurement
Turn off the power of the measuring device and return the measuring head to its position.
Clean the measuring platform and measuring equipment, keep it clean and tidy.
When using optical wire rule, the following points need to be paid attention to to ensure measurement accuracy and extend service life:
Keep clean
Clean optical lineation scales and measuring equipment regularly to avoid the accumulation of dust and dirt.
Use a clean cloth or paper towel to wipe the optical line ruler and avoid using corrosive cleaners.
Vibration avoidance
Place the measuring equipment on a smooth ground to avoid vibration and shock.
During the measurement process, avoid touching the measuring equipment and the measured object to avoid vibration.
Maintain temperature stability
Optical wire gauge is sensitive to temperature changes and should be placed in a stable temperature environment.
Avoid exposing the measuring equipment to high or low temperatures to avoid affecting the measurement accuracy.
Periodic calibration
Calibrate the optical wire rule regularly to ensure its measuring accuracy.
Calibrate using standard calibration tools and methods to avoid the accumulation of errors.
Proper use
When using the optical wire gauge, it should be operated in accordance with the requirements of the manual.
Avoid using too large or too small measuring force, so as not to damage the optical line ruler or affect the measurement accuracy.
Fifth, the application field of optical wire rule
Because of its high precision and stability, optical wire gauge has been widely used in many fields:
Machine tool manufacturing
In machine tool manufacturing, optical wire rule is used to measure the accuracy and positioning accuracy of machine tools.
The machining accuracy and product quality of the machine tool can be ensured by the measurement of the optical wire rule.
Precision measurement
In the field of precision measurement, optical lineation scales are used to measure tiny sizes and shape accuracy.
The high accuracy and stability of optical wire gauge make it an important tool for precision measurement.
Scientific research experiment
In scientific experiments, optical lineation scales are used to measure and record experimental data.
Accurate experimental data can be obtained through the measurement of optical lineation scale, which provides strong support for scientific research experiments.
Quality inspection
In the field of quality inspection, optical lineation scales are used to check the size and shape accuracy of products.
Through the measurement of optical wire scale, the quality of the product can be ensured to meet the standard requirements.
Vi. Summary
Optical line gauge is a kind of high precision measuring tool and has a wide range of applications. In this paper, the basic principle, calibration steps, operation steps and precautions of optical wire gauge are introduced in detail, hoping to help readers better understand and use optical wire gauge. When using optical wire rule, it is necessary to pay attention to maintaining cleanliness, avoiding vibration, maintaining temperature stability, regular calibration and correct use to ensure measurement accuracy and extend service life.
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