Imagine measuring distances with pinpoint accuracy without ever touching the object. Laser displacement sensors do just that, using laser technology to capture precise measurements of position, displacement, and more. In this article, you’ll learn about the principles behind these sensors, including laser triangulation and echo analysis, and discover their diverse applications in industries from manufacturing to electronics. Whether you’re interested in improving quality control or enhancing production efficiency, understanding laser displacement sensors could be a game-changer.
A laser displacement sensor is a measuring instrument that uses laser technology to measure the position, displacement, and other changes of a measured object. It consists of a laser, a laser detector, and a measuring circuit.
This type of sensor offers accurate, non-contact measurements and is capable of measuring displacement, thickness, vibration, distance, diameter, and other precise geometric measurements. The laser used in the sensor has excellent straightness characteristics.
Compared to ultrasonic sensors, laser displacement sensors have a higher level of accuracy. However, the laser generating device is relatively complex and large, limiting the range of applications for laser displacement sensors.
A laser displacement sensor is a non-contact device that precisely measures the position, displacement, and other dimensional changes of an object. It is widely employed in industrial applications to detect displacement, thickness, vibration, distance, diameter, and various geometric properties of materials and components.
The operating principle of laser displacement sensors can be categorized into two primary methods: laser triangulation and time-of-flight (TOF) analysis. Laser triangulation is typically utilized for high-precision, short-range measurements (usually up to 1 meter), while time-of-flight analysis is more suitable for long-range measurements (up to several hundred meters).
The following is a concise overview of these two measurement methods:
The sensor’s internal signal processing involves both analog and digital electronic components. The reflected light’s position on the receiving element is processed, analyzed by a microprocessor, and converted into a corresponding output value. This value is then used to adjust the laser emission and fine-tune the measurement, ensuring optimal performance across the sensor’s operating range.
To measure a component, place it in the designated position on the conveyor belt. The laser sensor, triggered by the laser scanner, will then detect and measure the component, finally determining its length.
Place multiple laser sensors in the direction of tilt of the workpiece to be measured and have one sensor directly output the measurement value. Furthermore, a software can be utilized to calculate the measurement value and display the result based on the received signal or data.
Use two laser scanners to position the components being measured between them and then obtain the data through the sensors to assess the accuracy and completeness of the component’s dimensions.
The laser transmitter projects a visible red laser onto the surface of the object being measured through a lens. The scattered laser light from the object’s surface then passes through the receiver lens and is detected by the internal CCD linear camera.
Based on the distance from the object, the CCD linear camera detects the light spot at different angles. Using this angle and the known distance between the laser and the camera, the digital signal processor calculates the distance between the sensor and the object.
The position of the beam in the receiving element is then processed by analog and digital circuits, and the corresponding output value is calculated by the microprocessor. The standard data signal is output proportionally in the analog window set by the user. If switching value output is selected, it will be activated within the set window and shut off outside of it.
Both the analog and switching outputs can have separate detection windows. The laser displacement sensor, using triangulation, can achieve maximum linearity of 1um with a resolution of 0.1um. For example, the ZLDS100 type sensor boasts a high resolution of 0.01%, high linearity of 0.1%, fast response of 9.4KHz, and the ability to perform in harsh environments.
The laser displacement sensor utilizes the principle of echo analysis to accurately measure distance. The sensor is comprised of a processor unit, echo processing unit, laser transmitter, laser receiver, and other components.
Each second, the laser transmitter sends one million laser pulses to the object being detected, which then returns to the receiver. The processor calculates the time it takes for the laser pulse to reach the object and return, allowing for the calculation of the distance value.
This value is determined by taking the average of thousands of measurements, using the pulse time method. Although the laser echo analysis method is suitable for long-distance detection, it has a lower accuracy compared to the laser triangulation method. The farthest detection distance it can reach is 250 meters.
Laser displacement sensors are widely used to measure various physical quantities including length, distance, vibration, speed, orientation, and more. These sensors have also found applications in flaw detection and monitoring of air pollutants.
A laser sensor is used to measure the thickness of metal sheets.
Detection of changes in thickness can assist in identifying wrinkles, small holes, or overlaps, thereby preventing machine failure.
Place the component to be measured in the designated position on the conveyor belt. The laser sensor will then detect the component and simultaneously measure it using the triggered laser scanner, finally determining its length.
Arrange multiple laser sensors in the direction of tilt of the workpiece to be measured. The measurement value can be directly outputted through one of the sensors. Additionally, a software program can be utilized to calculate the measurement value based on the signals or data and provide the result.
Place the measured components between two laser scanners, and then read out the data through the sensor to detect the accuracy and completeness of the component size.
The laser sensor is integrated into the production process of filling products. As the filling products pass through the sensor, it can accurately detect if they are filled to capacity. The sensor uses an advanced program of laser beam reflection on the surface to accurately determine if the filling of the products is up to standard and the quantity of the products.
First, you will require 2 to 3 laser displacement sensors for a combined measurement, as illustrated in the figure.
Next, place the three laser displacement sensors in a straight line, parallel to the production line, and determine the spacing between them based on the desired measurement accuracy.
Finally, make the object move in a direction that is parallel to the line of installation of the laser displacement sensors.
When the production line is aligned with the sensor’s installation line, the larger the difference in distance measured by the three sensors, the poorer the straightness of the object will be. Conversely, a smaller difference in distance measured by the three sensors indicates that the object is straighter.
You can calculate the percentage of straightness by taking into account the length of the object to be measured and the spacing between the three sensor installations, resulting in a quantifiable output signal.
With this setup, you have successfully achieved the goal of detecting the straightness of objects.
Resolving Power:
The resolution of an eddy current sensor can reach as high as 0.1mm, which is comparable to that of a laser displacement sensor.
Linearity:
The linearity of an eddy current sensor is typically low, around 1% of the measurement range. On the other hand, high-end laser displacement sensors boast a linearity of around 0.1%.
Measurement Conditions:
Eddy current sensors require the test object to be a conductive and non-magnetic material, such as aluminum or copper, but not iron.
Laser displacement sensors, on the other hand, are capable of measuring both magnetic and conductive objects.
The precision of capacitive displacement sensors is incredibly high, surpassing that of laser displacement sensors. However, their range is quite limited, usually less than 1mm. On the other hand, laser displacement sensors have a much wider range, with a maximum measurement range of up to 2 meters.
The measurement principle of an optical fiber displacement sensor is to determine the displacement of an object by detecting changes in the luminous flux and light intensity reflected from the object’s surface due to the displacement.
The sensor’s probe consists of a transmitting optical fiber and a receiving optical fiber.
For small objects, conventional non-contact displacement sensors are limited by the reflection area, resulting in poor measurement performance. However, the optical fiber displacement sensor can be designed with a very small probe (with a minimum diameter of 0.2mm), making it suitable for measuring small objects.
Additionally, it can be made in the form of linear transmission and reception.
The displacement value is calculated by measuring the degree of shielding of the object to the optical fiber during the displacement process, with an accuracy of up to 0.01um.
The maximum measuring range of the sensor is 4mm.
As the founder of MachineMFG, I have dedicated over a decade of my career to the metalworking industry. My extensive experience has allowed me to become an expert in the fields of sheet metal fabrication, machining, mechanical engineering, and machine tools for metals. I am constantly thinking, reading, and writing about these subjects, constantly striving to stay at the forefront of my field. Let my knowledge and expertise be an asset to your business.
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