Air gap tolerance optimization method for reflective photoelectric encoder

Abstract

The present invention provides a method for optimizing the air gap tolerance of a reflective photoelectric encoder. The method is characterized by comprising an LED module (1), a photodiode array (2), a code disk (3), and a current regulating circuit (4). The LED module comprises two LEDs of the same model, namely LED1 and LED2; the photodiode array comprises an incremental code channel photodiode array (21) and a light intensity indicating photodiode (22), wherein the light intensity indicating photodiodes are two identical photodiodes, namely PD1 and PD2; the incremental code channel photodiodes comprise two groups of PD arrays, namely PD3 and PD4; and the current regulating circuit (4) comprises a quartz resistance amplifier circuit (41) and a current control circuit (42). The present invention can be applied to optimizing the air gap tolerance of a reflective photoelectric encoder and can be widely used in industrial production, aerospace, medical treatment, precision instruments, experimental research, numerical control machine tools, and other fields.

Description

(1) Technical field

[0001] The present invention relates to a method for optimizing the air gap tolerance of a reflective photoelectric encoder, which can be widely used in medical positioning, laboratories, navigation, aerospace, industrial automation, robotics, CNC machine tools and other fields. It belongs to the field of photoelectric encoder technology. (2) Background technology

[0002] Reflective photoelectric encoders are widely used sensors for position detection and motion control, operating on the principle of photoelectric conversion. These devices typically utilize optical principles to achieve high-precision position measurement and convert the results into digital signals for further processing by computers or control systems. With the development of modern industry and automation technology, the demand for high-precision position detection equipment continues to increase. Due to their superior performance, reflective photoelectric encoders have attracted widespread attention in many fields, particularly in automated production lines, robotics, aerospace, and precision manufacturing, where their application prospects are particularly broad.

[0003] The core operating principle of a reflective photoelectric encoder relies on the emission and reception of light sources. When the encoder's transmitter emits light, it is reflected by the surface of the target object and returned to the photodetector. The detector converts the reflected light into an electrical signal, which is then used to measure the target's position. The advantages of this measurement method lie in its high precision and non-contact nature, enabling the encoder to accurately locate and monitor motion without disturbing the object being measured.

[0004] However, in the practical application of reflective photoelectric encoders, the air gap (i.e., the distance between the encoder and the target object) requires extremely high accuracy. Variations in the air gap directly affect the intensity and quality of the optical signal. Therefore, reflective photoelectric encoders typically require an extremely small air gap tolerance, typically only a few hundred microns. This precision requirement somewhat limits the encoder's application areas and increases the cost and complexity of air gap control. For example, in many environments requiring high-precision measurement, device motion and position detection must be performed under dynamic conditions. In such situations, maintaining the stability and consistency of the air gap is a highly challenging engineering task.

[0005] In existing technologies, most reflective photoelectric encoders use a single LED for optical signal acquisition. The use of a single light source results in uneven variations in the intensity of the optical signal received by the photodetectors at different locations, making it impossible to uniformly amplify the signal. This uneven optical signal reception limits the size of the air gap to a very small range, making the air gap tolerance extremely small. Furthermore, environmental changes during use, such as temperature, humidity, and vibration, can significantly affect the encoder's measurement accuracy, further complicating the variations in the optical signal and complicating the control of air gap accuracy.

[0006] To address these issues, the present invention proposes a novel method for optimizing the air gap tolerance of a reflective photoelectric encoder. This optimization method utilizes symmetrical LED placement and uniformly adjusts the optical power of two sets of LEDs through current control connected to light-intensity-sensing photodiodes. This design ensures that the intensity of the light signal received by the incremental channel photodiodes changes synchronously with air gap variations, significantly improving the air gap tolerance of the reflective photoelectric encoder. Specifically, the symmetrical placement of the LEDs within the encoder structure ensures that the light signals emitted by the two LEDs are evenly distributed across the photodetector when the air gap varies. This uniform light intensity distribution not only improves the signal-to-noise ratio but also reduces measurement errors caused by air gap variations, enabling the reflective photoelectric encoder to operate over a wider range of air gaps. Furthermore, this method improves the output signal quality, enabling the encoder to provide stable and reliable position information under varying air gap conditions. The synchronization of light intensity variations significantly improves the system's response speed under dynamic operating conditions, making the encoder more adaptable to high-speed motion applications. This innovation, combining advanced engineering design and optical technology, has made significant progress in achieving high-precision and reliable photoelectric measurement for reflective photoelectric encoders. For example, in the aerospace sector, accurate position detection is crucial, and optimized encoders can ensure the stability and safety of aircraft in complex environmental conditions. In industrial automation, with the continuous development of intelligent manufacturing, reflective photoelectric encoders will also become an important tool for achieving efficient production. (3) Summary of the invention

[0007] The present invention aims to provide a method for optimizing the air gap tolerance of a reflective photoelectric encoder. The system involved in the method comprises an LED module (1), a photodiode array (2), a code disk (3), and a current regulating circuit (4). The LED module comprises two LEDs of the same model, namely LED1 and LED2; the photodiode array comprises an incremental code channel photodiode array (21) and a light intensity indicating photodiode (22), wherein the light intensity indicating photodiodes are two identical photodiodes, namely PD1 and PD2; the incremental code channel photodiodes comprise two groups of PD arrays, namely PD3 and PD4; and the current regulating circuit (4) comprises a quartz-resistance amplifier circuit (41) and a current control circuit (42).

[0008] The object of the present invention is achieved like this:

[0009] LED1 and LED2 are symmetrically arranged on the reflective photoelectric encoder chip with the chip center as the symmetrical point. The incremental code channel photodiode (21) receives the light signal emitted by the LED module (1) and reflected by the code disk (3) at the middle position between LED1 and LED2. The light intensity indication photodiode (22) is placed at symmetrical positions on both sides of the LED module (1) near the outside of the reflective photoelectric encoder chip and is lower than the LED module (1). After the light emitted by the LED module (1) is irradiated by the light intensity indication photodiode (22), it is converted into a voltage signal through the quartz-resistance amplifier circuit (41). The voltage signal is transmitted to the current control circuit (42) to adjust the current of the LED module (1) so that the light power output by LED1 and LED2 is equal to the preset light power. The light signal emitted by the LED module (1) is reflected to the incremental code channel photodiode (2) via the code disk (3). Since the LED module (1) is relatively close to the code disk (3), the light intensity indication photodiode (22) is converted into a voltage signal through the quartz-resistance amplifier circuit (41). The voltage signal is transmitted to the current control circuit (42) to adjust the current of the LED module (1) so that the light power output by LED1 and LED2 is equal to the preset light power. The LED modules (1) are symmetrically arranged and the optical power of the LED module (1) is adjusted to be consistent, so the light intensity distribution on the incremental code channel photodiode (21) is nearly uniform; when the air gap changes, since PD1 and PD2 are located between LED1 and LED2, PD1 and PD2 receive the light of LED1 and LED2 at the same time. Since LED1 and LED2 are symmetrical, the light signals reflected back are also symmetrical. After being superimposed on PD1, the light intensity distribution of the light signal changes to a uniform distribution in the Y direction, and the light signal is greatly optimized. Moreover, due to the symmetry, the light intensity on PD1 and PD2 is completely consistent. When the air gap changes, the light intensity on PD1 and PD2 is always consistent, and the PD signal can be amplified using the same gain multiple, overcoming the disadvantage of the traditional single-LED reflective photoelectric encoder that when the air gap increases, the amplitude of the light signal received by the PD farther away from the LED decreases much more than that of the other PD, thereby greatly increasing the tolerance for the air gap.

[0010] The light beam emitted by the LED module (1) can be light of various wavelengths such as infrared light, blue light, and red light. The specific light source used should be determined according to the light sensitivity of the photodiode used.

[0011] The light intensity indicating photodiode (22) is used to receive the light intensity emitted by the LED module (1). Since the performance of LEDs varies after leaving the factory, there are differences in light power under the same current. The light intensity indicating photodiode (22) receives the light emitted by the LED module (1), and the photocurrent is converted into a voltage signal that can be used for comparison through the quartz-resistance amplifier circuit (41). Finally, the power supply current of LED1 and LED2 is adjusted through the current control circuit (42) so that their light powers are exactly the same, which can effectively optimize the light power difference problem caused by the dual LEDs.

[0012] The LED modules (1) are symmetrically distributed on the reflective photoelectric encoder chip, so that the light signals emitted by LED1 and LED2 are symmetrical when reflected by the code disk (3) to the incremental code channel photodiode (2). After the light signals are superimposed, the light signals received by the incremental code channel photodiode (2) are uniform in the Y direction.

[0013] The method for optimizing the air gap tolerance of a reflective photoelectric encoder according to claim 1 is characterized in that: the LED module (1) is symmetrically distributed on the reflective photoelectric encoder chip and the current is adjusted by the current control circuit (4) so ​​that the amplitude of the optical signals received on PD1 and PD2 are the same, and when the air gap changes, the amplitude change value of the optical signals on PD1 and PD2 is also equal. (IV) Description of the accompanying drawings

[0014] Figure 1 The invention is composed of an LED module (1), a photodiode array (2), a code disk (3), and a current regulating circuit (4). The LED module is composed of two LEDs of the same model, namely LED1 and LED2; the photodiode array is composed of an incremental code channel photodiode array (21) and a light intensity indicating photodiode (22); the light intensity indicating photodiode is two identical photodiodes, namely PD1 and PD2; the incremental code channel photodiode is composed of two groups of PD arrays, namely PD3 and PD4; and the current regulating circuit (4) is composed of a quartz-resistance amplifier circuit (41) and a current control circuit (42).

[0015] Figure 2 This is the light spot distribution diagram in the reflective photoelectric encoder example. The first left one is the light spot distribution diagram after the air gap continues to decrease relative to the original minimum position, and the second left one is the light spot distribution diagram after the air gap continues to increase relative to the original maximum air gap. It can be observed that the light signal distribution in the Y direction is nearly uniform.

[0016] Figure 3 It is the output signal of the reflective photoelectric encoder and the standard sinusoidal signal. 1 is the standard sinusoidal signal, 2 is the output signal after the air gap exceeds the original maximum air gap and continues to increase, and 3 is the output signal after the air gap exceeds the original minimum air gap and continues to decrease.

[0017] Figure 4 This is a specific image of the placement of various components on the surface of a reflective photoelectric encoder chip. The surface components are composed of an LED module (1) and a photodiode array (2). The LED module is composed of two LEDs of the same model, namely LED1 and LED2; the photodiode array is composed of an incremental code channel photodiode array (21) and a light intensity indication photodiode (22). The light intensity indication photodiodes are two identical photodiodes, namely PD1 and PD2, and the incremental code channel photodiodes are composed of two groups of PD arrays, namely PD3 and PD4. (V) Specific implementation methods

[0018] Example 1: Figure 1An embodiment of a method for optimizing the air gap tolerance of a reflective photoelectric encoder is provided. The method for optimizing the air gap tolerance of a reflective photoelectric encoder comprises an LED module (1), a photodiode array (2), a code disk (3), and a current regulating circuit (4). The LED module comprises two LEDs of the same model, namely LED1 and LED2; the photodiode array comprises an incremental code channel photodiode array (21) and a light intensity indicating photodiode (22), the light intensity indicating photodiodes being two identical photodiodes, namely PD1 and PD2; the incremental code channel photodiodes comprise two groups of PD arrays, namely PD3 and PD4; the current regulating circuit (4) comprises a quartz resistance amplifier circuit (41) and a current control circuit (42); LED1 and LED2 are symmetrically arranged on a reflective photoelectric encoder chip with the chip center as the symmetrical point. The light signals emitted by LED1 and LED2 are received by PD1 and PD2 respectively. After receiving the light signals, PD1 and PD2 generate photocurrents, which are respectively input into the quartz-resistance amplifier circuit (41) to be converted into voltage signals. The voltage signals corresponding to PD1 and PD2 are then respectively input into the current control circuit (42) to adjust the luminous power of LED1 and LED2 to a preset value. Through this step, the luminous power of LED1 and LED2 is made consistent. The symmetrical arrangement of the LEDs in the LED module (1) can make the light signals emitted by the two groups of LEDs reflected back by the code disk (3) When the reflective photoelectric encoder chip is mounted on the chip, the light signal received by the incremental code channel photodiode (21) is two groups of light signals with exactly the same X-axis distribution and opposite Y-axis distribution. The light signal of a single group of LEDs can be fitted into a linear straight line in the Y-axis direction. When the light signals emitted by the two groups of LEDs are superimposed on the same PD, the light signal received on the PD becomes uniformly distributed in the Y direction. Since PD3 and PD4 are between LED1 and LED2, and since the luminous power of LED1 and LED2 is set to the same value, the amplitude of the light signal superimposed on PD3 and PD4 is also the same. At this time, the air gap between the reflective photoelectric encoder chip and the code disk (3) is reduced. At this time, the light signal distribution received on the incremental code channel photodiode (21) is as follows: Figure 2 As shown on the left; On the contrary, the air gap between the reflective photoelectric encoder chip and the code disk (3) is increased, and the distribution of the light signal received on the incremental code channel photoelectric encoder (21) is as follows: Figure 2 As shown in the second left picture, it can be observed that when the air gap changes, the optical signal on the incremental code photodiode (21) is a high-quality uniform light spot, and the output signal output by this optical signal is as follows: Figure 3As shown in the 2nd and 3rd signals, it can be observed that there are only slight differences between the 2nd and 3rd signals and the standard sinusoidal signals, and the output signal quality is excellent. In summary, the photoelectric encoder of this embodiment achieves high-precision and high-reliability photoelectric measurement through innovative design and engineering technology. This photoelectric encoder based on a symmetrical LED module, due to its symmetrical structural layout, enables flexible response to changes in the external environment during the optical signal processing process, and is particularly suitable for a wide range of applications in the fields of industrial automation, robotics, and high-end photoelectric measurement. The present invention not only provides an effective solution to the problems encountered by traditional photoelectric encoders in applications, but also opens up new horizons and directions for the development of related technical fields.

Claims

1. A method for optimizing the air gap tolerance of a reflective photoelectric encoder, characterized by: The invention is composed of an LED module (1), a photodiode array (2), a code disk (3), and a current regulating circuit (4), wherein the LED module is composed of two LEDs of the same model, namely LED1 and LED2; the photodiode array is composed of an incremental code channel photodiode array (21) and a light intensity indication photodiode (22), the light intensity indication photodiode is two completely identical photodiodes, namely PD1 and PD2; the incremental code channel photodiode array (21) is composed of two groups of photodiode arrays, namely PD3 and PD4; the current regulating circuit (4) is composed of a quartz-resistance amplifier circuit (41) and a current control circuit (42); LED1 and LED2 are connected to the chip on the reflective photoelectric encoder chip. The light intensity indicating photodiodes (22) are placed symmetrically with the center as the symmetrical point. The incremental code channel photodiode array (21) receives the light signal emitted by the LED module (1) and reflected by the code disk (3) at the middle position between LED1 and LED2. The light intensity indicating photodiodes (22) are placed at symmetrical positions on both sides of the LED module (1) near the outside of the reflective photoelectric encoder chip and are located lower than the LED module (1). After the light emitted by the LED module (1) is irradiated to the light intensity indicating photodiode (22), it is converted into a voltage signal through the quartz-resistance amplifier circuit (41). The voltage signal is transmitted to the current control circuit (42) to adjust the current of the LED module (1), so that the light power output by LED1 and LED2 is equal to the preset light power. The light signal emitted by the LED module (1) is reflected by the code disk (3) onto the incremental code channel photodiode array (21). Since the LED module (1) is symmetrically arranged relative to the code disk (3) and the light power of the LED module (1) is adjusted to be consistent, the light intensity distribution on the incremental code channel photodiode array (21) is nearly uniform. When the air gap changes, since PD3 and PD4 are located between LED1 and LED2, PD3 and PD4 receive the light from LED1 and LED2 at the same time. Since LED1 and LED2 are symmetrical, the light signals reflected back are also symmetrical. After being superimposed on PD3 and PD4, the light intensity distribution of the light signal changes to a uniform distribution in the Y direction, and the light signal is optimized. Moreover, due to the symmetry, the light intensity on PD3 and PD4 is completely consistent. When the air gap changes, the light intensity on PD3 and PD4 is always consistent, and the photodiode signal can be amplified using the same gain multiple.

2. The air gap tolerance optimization method for a reflective photoelectric encoder according to claim 1, wherein: The light beam emitted by the LED module (1) includes various infrared lights, blue lights, and red lights that are adapted to the wavelengths received by the photodiode.

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