Electronic

What is a Laser Displacement Sensor?how it works

Laser Displacement Sensor

Laser displacement sensors are sensors that utilize laser technology for measurement. It consists of a laser, a laser detector and a measuring circuit. Laser sensors are new measuring instruments. It can accurately measure the position, displacement and other changes of the measured object without contact.

Precision geometric measurements such as displacement, thickness, vibration, distance, diameter, etc. can be measured. The laser has the excellent characteristics of good straightness, and the laser displacement sensor has higher accuracy than the known ultrasonic sensor. However, the laser generating device is relatively complex and bulky, so it has strict requirements on the application range of the laser displacement sensor.

Fundamental

Laser displacement sensor can accurately and non-contact measurement of the position, displacement and other changes of the object to be measured, mainly used in the measurement of geometric quantities such as displacement, thickness, vibration, distance, diameter of the detected object.

According to the measurement principle, the principle of laser displacement sensor is divided into laser triangulation method and laser echo analysis method. The laser triangulation method is generally suitable for high-precision and short-distance measurement, while the laser echo analysis method is used for long-distance measurement. Two measurement methods of the principle of laser displacement sensor are introduced.

The light beam is processed by analog and Electronic digital processing at the position of the receiving element, after internal micro-processing analysis, and then calculates the corresponding output value, and then adjusts the output value, and emits a light to the object, and this time the beam The light can adjust the distance of the displacement.

use

1. Length measurement

Put the measured component on the conveyor belt at the specified position, the laser sensor detects the component and measures it at the same time with the triggered laser scanner, and finally the length of the component is obtained.

2. Check the uniformity

Put several laser sensors in a row in the inclined direction of the movement of the workpiece to be measured, and directly output the measurement value through one sensor. In addition, a software can be used to calculate the measurement value and read the result according to the signal or data.

3. Inspection of electronic components

Using two laser scanners, place the component under test between the two, and finally read the data through the sensor, so as to detect the accuracy and integrity of the size of the component.

triangulation

The laser transmitter shoots the visible red laser to the surface of the object to be measured through the lens, and the laser scattered by the surface of the object passes through the receiver lens and is received by the internal CCD linear camera. According to different distances, the CCD linear camera can see” this light. From this angle and the known distance between the laser and the camera, the digital signal processor can calculate the distance between the sensor and the object being measured.

At the same time, the beam is processed by analog and digital circuits at the position of the receiving element, and analyzed by the microprocessor to calculate the corresponding output value, and output the standard data signal proportionally within the analog window set by the user. If the switch output is used, it will be turned on within the set window and turned off outside the window. In addition, the detection window can be set independently for analog quantity and switch quantity output.

The maximum linearity of the laser displacement sensor using the triangulation method can reach 1um, and the resolution can reach the level of 0.1um. For example, the ZLDS100 type sensor can achieve 0.01% high resolution, 0.1% high linearity, 9.4KHz high response, and adapt to harsh environments.

echo analysis

Laser displacement sensors use the principle of echo analysis to measure distance to a certain degree of accuracy. The inside of the sensor is composed of a processor unit, an echo processing unit, a laser transmitter, and a laser receiver. The laser displacement sensor transmits one million laser pulses per second to the detection object through the laser transmitter and returns to the receiver. The processor calculates the time required for the laser pulse to meet the detection object and return to the receiver, thereby calculating the distance value , the output value is the average output of thousands of measurement results. It is measured by the so-called pulse time method. The laser echo analysis method is suitable for long-distance detection, but the measurement accuracy is lower than that of the laser triangulation method, and the longest detection distance can reach 250m.

Measurement application

Laser displacement sensors are often used for the measurement of physical quantities such as length, distance, vibration, speed, and orientation, as well as for flaw detection and monitoring of atmospheric pollutants.

1. Size determination: position identification of tiny parts; monitoring of the presence or absence of parts on conveyor belts; detection of material overlap and coverage; control of robot position (tool center position); device status detection; device position detection (through small holes); Liquid level monitoring; thickness measurement; vibration analysis; crash test measurement; automobile related tests, etc.

2. Thickness measurement of metal flakes and thin plates: Laser sensors measure the thickness of metal flakes (thin plates). Thickness change detection can help find wrinkles, small holes or overlaps to avoid machine failure.

3. Measurement of cylinder barrel, simultaneous measurement: angle, length, inner and outer diameter eccentricity, conicity, concentricity and surface profile.

4. Length measurement: put the measured component on the conveyor belt at the specified position, the laser sensor detects the component and measures it at the same time with the triggered laser scanner, and finally the length of the component is obtained.

5. Inspection of uniformity: put several laser sensors in a row in the inclination direction of the movement of the workpiece to be measured, and directly output the measurement value through one sensor. In addition, a software can be used to calculate the measurement value and read it according to the signal or data. The results.

6. Inspection of electronic components: Use two laser scanners to place the component under test between the two, and finally read the data through the sensor, so as to detect the accuracy and integrity of the size of the component.

7. Inspection of filling level on the production line: The laser sensor is integrated into the manufacturing of the filling product. When the filling product passes the sensor, it can detect whether it is full. The sensor can accurately identify whether the filling of the filling product is acceptable and the quantity of the product with the extension of the laser beam reflecting surface.

8. The sensor measures the straightness of the object: First, you need 2-3 laser displacement sensors for combined measurement, as shown in the figure. Then install the three laser displacement sensors on a line parallel to the production line, and determine the distance between the three laser displacement sensors according to the measurement accuracy you need. Finally, you need to make this one object run parallel to the laser displacement sensor mounting line. When the production line and the installation line of the sensor are parallel, the greater the distance difference measured by the three sensors, the worse the straightness of the object, and the smaller the distance difference measured by the three sensors, indicating the straightness of the object The better, you can establish a percentage of straightness according to the data of the length of the object you want to measure and the distance between the three sensor installations, so as to obtain a quantitative signal output, which has achieved the purpose of detecting the straightness of the object.

Motion Sensor Classification

Eddy Current Displacement Sensor

Resolution: The highest resolution of the eddy current sensor can reach 0.1um, which is basically equivalent to the laser displacement sensor

Linearity: The linearity of the eddy current sensor is generally low, about 1% of the range, and the high-end laser displacement sensor is generally 0.1%

Measurement conditions: The eddy current sensor requires the measured object to be a conductor and non-magnetic, that is, non-magnetic conductors, such as aluminum, copper, etc., but not iron; Measurable.

Capacitive displacement sensor

The accuracy of capacitive displacement sensor is very high, much higher than that of laser displacement sensor, but the range of capacitive displacement sensor is very small and generally less than 1mm, and the range of laser displacement sensor can be up to 2m.

Fiber Optic Displacement Sensor

The measurement principle of the optical fiber displacement sensor is to measure the displacement of the object by measuring the change of the luminous flux and light intensity reflected from the surface of the object due to the displacement. The probe consists of two parts: the transmitting fiber and the receiving fiber. For the displacement and vibration of very small objects, the conventional non-contact displacement sensor is limited by the reflection area, resulting in an unsatisfactory measurement effect, while the optical fiber displacement sensor can be made into a very small probe (minimum 0.2mm diameter) , In addition, it can be made into the form of linear transmission and reception, and the displacement value can be calculated by measuring the degree of occlusion of the optical fiber by the object during the displacement process. The accuracy can reach 0.01um, and the maximum range is 4mm.

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