This section provides an overview for linear scales as well as their applications and principles. Also, please take a look at the list of 10 linear scale manufacturers and their company rankings.
Table of Contents
Linear Scales, also called Linear Encoders, are used to measure positions and distances in a straight line with high accuracy.
Linear Scales are classified into two types according to the standard of the distance traveled: the absolute type, which calculates the distance traveled from the absolute position, and the incremental type, which does not have an absolute position and calculates the distance traveled only by the distance traveled.
There are also two types of detection methods: electromagnetic detectors that use electromagnetic induction and optical detectors that read light from a light source by transmitting it through a code wheel, with the electromagnetic method being slightly more widely used.
Linear Scales are widely used in the fields of machine tools and semiconductor manufacturing, where precision measurement is required.
The electromagnetic Linear Scales are also used in more general applications due to their simple structure. A typical example is the digital caliper, a tool that measures the length of two points and displays the result digitally.
Electromagnetic Linear Scales use the principle of electromagnetic induction in physics.
The main scale and the detector each contain a coil, and when the distance between them changes, an electromotive force corresponding to the distance is generated.
The simple structure is resistant to contamination and can be used in many cases, but it is not suitable for environments where magnetic fields are generated.
Optical Linear Scales emit light from a light-emitting element and are detected by a light-receiving element located on the opposite side, with a fixed main scale and reticle grating between the light-emitting and light-receiving elements. Slits are cut in the main scale and the reticle grating, and the slits generate interference fringes, which are electrically converted to determine the position.
Optical Linear Scales are more accurate than electromagnetic Linear Scales and are less susceptible to magnetic fields, but they are also slightly larger and more susceptible to external light irradiation.
In recent years, there has been rapid progress in semiconductors, and the semiconductor industry has been developing with higher integration in accordance with Moore's Law. This progress in the semiconductor industry has spilled over into various electronic devices, and various products are becoming more electronically controlled and high-precision.
As integration and density continue to increase, it is important to achieve higher precision in position detection for manufacturing equipment that produces semiconductors and machine tools that manufacture mechanical parts with high precision.
Precise position control in semiconductor manufacturing equipment and machine tools requires an actuator to move an object and a detection method to detect the precise position of the actuator. Currently, laser interferometers and encoders are used for precise position detection.
In designing an actuator, it is common to configure an actuator based on linear motion in the three axes (X, Y, and Z) and spatial motion by combining these three axes. Therefore, Linear Scales are used for precise linear position detection. Scales and detectors are installed on the moving and fixed parts, respectively, to precisely detect the distance.
Linear Scales are widely used in precision equipment for machine tools and semiconductor manufacturing because they can measure positions with high precision.
Therefore, the mounting method and mounting accuracy are important when designing a scale in order to maintain its accuracy. The installation accuracy is described in each product and the manufacturer's instruction manual in order to achieve the performance of the linear scale. Regarding the mounting method, it is necessary for the designer to consider the structure of the device to which the linear scale is mounted.
As the accuracy of Linear Scales themselves is on the order of microns, for example, mounting accuracy of 1 mm or less is required for the distance between the sensor and the scale, yaw, roll, and pitch, respectively. it may be necessary to design and manufacture a precision jig for installation, or to manually adjust the scale during installation.
*Including some distributors, etc.
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