Principle and Application of Laser Displacement Sensor

The laser displacement sensor can measure precise geometric measurements such as displacement, thickness, vibration, distance, and diameter. The laser has the excellent characteristics of good straightness, and the same laser displacement sensor has higher accuracy than the known ultrasonic sensor. However, the laser generating device is relatively complex and large in size, so the application range of the laser displacement sensor is more stringent.

Principle of Laser Displacement Sensor

Let me share with you a schematic diagram of a laser displacement sensor. The basic principle of a general laser displacement sensor is the optical triangulation method:

The semiconductor laser ① is focused on the measured object ⑥ by the lens ②. The reflected light is collected by the lens ③ and projected onto the CMOS array ④; the signal processor ⑤ calculates the position of the light spot on the array ④ by trigonometric function to obtain the distance to the object.

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

1. The principle of laser triangulation method of laser displacement sensor

The laser transmitter shoots the visible red laser to the surface of the measured object through the lens, and the laser reflected by 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 at different angles" "This light spot. Based on 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 measured object.

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

The highest linearity of the laser displacement sensor adopting 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.

2. Principle of Laser Echo Analysis Principle of Laser Displacement Sensor

The laser displacement sensor uses the principle of echo analysis to measure the distance to achieve 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 emits one million laser pulses per second through the laser transmitter to the detection object 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 to calculate 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 farthest detection distance can reach 250m.

Application description of the principle of laser displacement sensor

Laser displacement sensors are often used to measure physical quantities such as length, distance, vibration, speed, and orientation, and can also be used for flaw detection and monitoring of atmospheric pollutants.

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

2. Thickness measurement of thin metal sheets and plates: The laser sensor measures the thickness of thin metal sheets (thin plates). Detection of changes in thickness can help find wrinkles, small holes or overlaps to avoid machine malfunctions.

3. Measurement of the 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 designated position, the laser sensor detects the component and measures it simultaneously with the triggered laser scanner, and finally obtains the length of the component.

5. Uniformity inspection: Put several laser sensors in a row in the tilt direction of the workpiece to be measured, and directly output the measurement value through a sensor. In addition, you can also use a software to calculate the measurement value and read the result according to the signal or data. .

6. Electronic component inspection: Use two laser scanners to place the component under test between them, and finally read the data through the sensor to detect the accuracy and completeness of the component size.

7. Inspection of the filling level on the production line: The laser sensor is integrated into the production of the filling product. When the filling product passes the sensor, it can be detected whether it is full. The sensor uses the extended program of the laser beam reflection surface to accurately identify whether the filling product is qualified and the quantity of the product.

8. The sensor measures the straightness of the object: first you need 2-3 laser displacement sensors for combined measurement, and then install the 3 laser displacement sensors on a straight line parallel to the production line, and according to the measurement accuracy you need Determine the distance between the three laser displacement sensors. Finally, you need to make this object move in a direction parallel to the installation line of the laser displacement sensor. When the production line is parallel to the installation line of the sensor, the greater the difference between the distances measured by the three sensors, the worse the straightness of the object, the smaller the difference between the distances measured by the three sensors, indicating the straightness of the object The better, you can establish a straightness percentage based on the length of the object you want to measure, the distance between the three sensor installations and other data, so as to obtain a quantified signal output, which has achieved the purpose of detecting the straightness of the object.