A high-precision grating micro-displacement sensor based on 90-degree phase-shift circuit

Abstract

The application belongs to the technical field of micro-displacement sensors, and particularly relates to a high-precision grating micro-displacement sensor based on a 90-degree phase-shifting circuit. The circuit system comprises a bias circuit, a 90-degree phase-shifting circuit and a ten-thousand-fold subdivision interpolation circuit. The optical circuit system is electrically connected with the bias circuit. The bias circuit is electrically connected with the 90-degree phase-shifting circuit. The 90-degree phase-shifting circuit is electrically connected with the ten-thousand-fold subdivision interpolation circuit. The phase-shifting circuit for locking phase provided by the application can lock the phase shift at 90 degrees when the frequency fluctuates. Even at a low frequency of 1HZ, the 90-degree phase shift can be stabilized. The application solves the problem that the input signal is not an ideal sine signal due to the assembly and machining errors of the high-precision grating micro-displacement sensor in the actual application process. The subdivision interpolation multiple is limited to ten thousand due to the amplitude error, bias error and phase error of the input sine signal.

Description

Technical Field

[0001] This invention belongs to the field of micro-displacement sensor technology, specifically relating to a high-precision grating micro-displacement sensor based on a 90-degree phase-shifting circuit. Background Technology

[0002] Optical displacement detection, as one of the mainstream nano- and micro-displacement detection technologies, boasts advantages such as high precision, high resolution, and immunity to electromagnetic interference. Among these, grating-type micro-displacement sensing technology, with its high resolution and strong resistance to electromagnetic interference, is widely used in semiconductor precision manufacturing and precision machining. For example, the precision stage in a lithography machine directly affects parameters such as feature size and overlay accuracy, and this stage is typically measured in real-time and fed back comprehensively by a linear displacement sensor. Simultaneously, the high precision and high integration characteristics of lithography systems place demands on linear displacement sensors with high resolution, small size, and strong anti-interference capabilities. In conclusion, improving the resolution and integration of precision displacement measurement is a key issue in the current development of the precision manufacturing industry.

[0003] Because the grating displacement sensor outputs a single-channel sinusoidal signal, and sinusoidal signals are symmetrical, the sensor's direction of movement cannot be directly determined from the amplitude of the sinusoidal signal output. Furthermore, due to the non-constant rate of change of the sinusoidal signal within one output cycle, and the presence of interference, noise, and errors, its displacement resolution cannot be very high. Therefore, a subdivision interpolation circuit is needed to obtain the displacement information from the sinusoidal signal and improve its resolution. However, the subdivision interpolation circuit requires two sine and cosine signals with a 90° phase difference to achieve subdivision.

[0004] In theory, using the arctangent method to subdivide two sine and cosine signals can achieve subdivision interpolation with infinite multiples. However, in practical applications, the input signals are not ideal sine and cosine signals. Due to errors in the manufacturing process and assembly of displacement sensors, the output sine and cosine signals contain amplitude errors, bias errors, and phase errors. The presence of these three errors is currently the main factor limiting the subdivision interpolation multiple, so it is necessary to improve it. Summary of the Invention

[0005] To address the technical problem of amplitude, bias, and phase errors in the output sine and cosine signals caused by errors in the manufacturing process and assembly of the aforementioned displacement sensors, this invention provides a high-precision grating micro-displacement sensor based on a 90-degree phase-shifting circuit. This sensor shifts the grating displacement signal by 90 degrees and expands the single-channel sine output into two orthogonal sine and cosine signals. After passing through a subdivision interpolation circuit, the amplitude and phase errors that may be introduced during testing can be suppressed, achieving high-resolution grating micro-displacement detection and further improving testing accuracy.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A high-precision grating micro-displacement sensor based on a 90-degree phase-shifting circuit includes an optical path system and a circuit system. The optical path system and the circuit system are electrically connected. The circuit system includes a bias circuit, a 90° phase-shifting circuit, and a 10,000x subdivision interpolation circuit. The optical path system is electrically connected to the bias circuit, which is electrically connected to the 90° phase-shifting circuit. The 90° phase-shifting circuit is electrically connected to the 10,000x subdivision interpolation circuit. The optical path system outputs a displacement signal, which passes sequentially through the bias circuit, the 90° phase-shifting circuit, and the 10,000x subdivision interpolation circuit. Finally, the 10,000x subdivision interpolation circuit outputs a high-resolution displacement signal.

[0008] The bias circuit includes a bias input terminal, a first chip, a second chip, a third chip, a fourth chip, a first sliding rheostat, and a bias output terminal. The input terminal is electrically connected to the first chip, the first chip is electrically connected to the second chip, and the second chip is electrically connected to the bias output terminal.

[0009] The first chip is electrically connected to the third chip and the fourth chip respectively through the first sliding rheostat.

[0010] The first chip uses an LF356M input operational amplifier, the second chip uses a PA241DW high-voltage power operational amplifier, and the third and fourth chips both use LM399H voltage reference IC shunts.

[0011] The 90° phase-shifting circuit includes a phase-shifting input terminal, an adder, a feedforward integrator, a feedback integrator, a second sliding rheostat, a first resistor, a second resistor, a first capacitor, a second capacitor, a third capacitor, a third resistor, a fourth resistor, a first phase-shifting output terminal, and a second phase-shifting output terminal. The phase-shifting input terminal is electrically connected to the negative input terminal of the adder through the second sliding rheostat. The negative input terminal of the adder is electrically connected to the output terminal of the adder through the first resistor. The output terminal of the adder is electrically connected to the negative input terminal of the feedforward integrator through the second resistor.

[0012] The negative input terminal of the feedforward integrator is electrically connected to the output terminal of the feedforward integrator through a first capacitor, and the output terminal of the feedforward integrator is electrically connected to the second phase-shifted output terminal.

[0013] The negative input terminal of the adder is electrically connected to the output terminal of the feedback integrator. The negative input terminal of the feedback integrator is electrically connected to the output terminal of the feedback integrator through a second capacitor. The negative input terminal of the feedback integrator is electrically connected to the output terminal of the feedback integrator through a third capacitor and a fourth resistor. The third capacitor and the fourth resistor are connected in series. The second capacitor is connected in parallel with the third capacitor and the fourth resistor. The negative input terminal of the feedback integrator is electrically connected to the second phase-shifted output terminal through the third resistor.

[0014] The 10,000-fold subdivision interpolation circuit uses the dedicated DSP interpolator iC-TW8 manufactured by IC-Haus, which is a general-purpose 16-bit Sin / Cos interpolator.

[0015] Compared with the prior art, the beneficial effects of this invention are:

[0016] The phase-locked phase-shifting circuit provided by this invention can lock the phase shift at 90 degrees when the frequency fluctuates, even at low frequencies of 1 Hz. Simultaneously, this invention expands one input into two outputs without altering the original input signal, and the amplitude and bias of the phase-shifted signal remain unchanged compared to the original signal; only the phase has changed by 90 degrees. This invention effectively solves the problem that in practical applications, the input signal is not an ideal sine or cosine signal due to assembly and manufacturing errors in high-precision grating micro-displacement sensors, thus achieving a subdivision interpolation factor of up to ten thousand times, which is limited by amplitude, bias, and phase errors in the input sine and cosine signals. Attached Figure Description

[0017] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0018] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0019] Figure 1 This is a flowchart of the present invention;

[0020] Figure 2This is a schematic diagram of the bias circuit of the present invention;

[0021] Figure 3 This is a schematic diagram of the phase-shifting circuit of the present invention;

[0022] Figure 4 This is a flowchart of the phase-shifting circuit of the present invention;

[0023] Figure 5 This is a schematic diagram of the interpolation circuit with a subdivision ratio of 10,000 times according to the present invention.

[0024] Wherein: 1 is the optical system, 2 is the circuit system, 3 is the high-resolution displacement signal, 201 is the bias circuit, 202 is the 90° phase shift circuit, 203 is the 10,000x subdivision interpolation circuit, IN1 is the bias input terminal, U1 is the first chip, U2 is the second chip, U3 is the third chip, U4 is the fourth chip, R11 is the first sliding rheostat, OUT1 is the bias output terminal, SIN is the phase shift input terminal, U1A is the adder, U1B is the feedforward integrator, U2A is the feedback integrator, R1 is the second sliding rheostat, R2 is the first resistor, R3 is the second resistor, C1 is the first capacitor, C2 is the second capacitor, C3 is the third capacitor, R4 is the fourth resistor, R5 is the fourth resistor, OUTA is the first phase shift output terminal, and OUTB is the second phase shift output terminal. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. These descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the claims of the present invention. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0027] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0028] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0029] In this embodiment, as Figure 1 As shown, optical path system 1 outputs a displacement signal, which sequentially passes through bias circuit 201, 90° phase shift circuit 202, and 10,000x subdivision interpolation circuit 203. Finally, 10,000x subdivision interpolation circuit 203 outputs a high-resolution displacement signal 3. Optical path system 1 converts displacement information into a standard sinusoidal signal and inputs it to the circuit system. The diffraction interference system is mainly affected by interference from ambient light sources and changes in the refractive index in the optical path. Changes in ambient light sources cause a shift in the bias level of the output signal. This shift in the bias level of the optical path output is eliminated by the bias circuit in the circuit system.

[0030] In this embodiment, as Figure 2 As shown, the bias circuit consists of an LF356M input operational amplifier, a PA241DW high-voltage power operational amplifier, an LM399H voltage reference IC shunt, and its bias voltage is adjusted by the first sliding rheostat R11.

[0031] In this embodiment, as Figure 3 , Figure 4 As shown, adder U1A can compare the input sine wave signal with the feedback signal that has been phase-shifted by 90 degrees and perform gain compensation. The amplitude of the signal with a 90-degree phase shift is adjusted by the ratio of the second sliding rheostat R1 to the first resistor R2. In actual operation, the amplitude can be controlled by the resistance value of the second sliding rheostat R1, so that the output amplitude is always consistent with the input amplitude.

[0032] U1B is a feedforward integrator. When a sinusoidal signal is input, the input voltage is a sinusoidal wave. If U1 = U m sinwt, then from the proportional-integral input-output formula (1), we can obtain

[0033]

[0034]

[0035] At this time, the output voltage of the integrator circuit is a cosine wave. The phase of U0 leads U1 by 90°, so the function of the proportional-integral circuit U1B is to shift the phase by 90 degrees. Moreover, by adjusting the ratio of the second resistor R3 to the first capacitor C1, the phase difference between the two output signals at different operating frequencies can still be maintained at 90°.

[0036] The feedback integrator U2A can be viewed as an active proportional-integral circuit, i.e., a loop filter, used to feed the output signal back to the input, thereby forming closed-loop control. When the frequency and amplitude of the input signal change, the phase difference between the two output signals always remains at 90°, similar to the principle of a phase-locked loop.

[0037] The second capacitor C2 and the third resistor R4 are used to control the phase shift angle. By adjusting their ratio, a phase shift of 0-180° can be achieved, but only a 90° phase shift is used in this embodiment. The third capacitor C3 and the fourth resistor R5 are used for high-frequency lead phase compensation and to reduce high-frequency gain, thereby preventing self-oscillation.

[0038] In summary, the feedback integrator U2A is a linear low-pass filter used to filter out high-frequency components and noise in the output voltage. It not only filters out high-frequency components, but more importantly, it affects important loop parameters such as phase noise and loop stability. Although the actual circuit of the feedback integrator is usually very simple, it has a significant impact on the performance of the entire circuit.

[0039] In this embodiment, as Figure 5 As shown, the 10,000x subdivision interpolation circuit 203 uses the dedicated DSP interpolator iC-TW8 manufactured by IC-Haus. The iC-TW8 is a general-purpose 16-bit Sin / Cos interpolator with advanced automatic calibration capabilities. This chip uses the arctangent method to subdivide two sine and cosine signals, and selects the subdivision factor and output mode through eight configuration resistors. It requires a single power supply (5V or 3.3V) and has no internal negative charge pump; therefore, effective subdivision interpolation can only be performed when the input signal voltage is greater than 0V. Because the phase-shifting circuit removes and compensates for phase and amplitude errors, the subdivision scheme used in this embodiment can achieve 10,000x subdivision. This subdivision interpolation factor can meet the resolution requirements of most sensors. Based on the grating's size parameters, the optical system output signal period is on the order of several hundred nanometers. After 10,000 subdivisions by the 10,000x subdivision interpolation circuit 203, the resolution of the high-resolution displacement signal 3 output by the grating micro-displacement sensor can reach the order of several hundred picometers.

[0040] The above description only illustrates the preferred embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention, and all such changes should be included within the protection scope of the present invention.

Claims

1. A high-precision grating micro-displacement sensor based on a 90-degree phase-shifting circuit, characterized in that: The system includes an optical path system (1) and a circuit system (2). The optical path system (1) and the circuit system (2) are electrically connected. The circuit system (2) includes a bias circuit (201), a 90° phase shift circuit (202), and a 10,000x subdivision interpolation circuit (203). The optical path system (1) is electrically connected to the bias circuit (201). The bias circuit (201) is electrically connected to the 90° phase shift circuit (202). The 90° phase shift circuit (202) is electrically connected to the 10,000x subdivision interpolation circuit (203). The optical path system (1) outputs a displacement signal. The displacement signal passes through the bias circuit (201), the 90° phase shift circuit (202), and the 10,000x subdivision interpolation circuit (203) in sequence. Finally, the 10,000x subdivision interpolation circuit (203) outputs a high-resolution displacement signal (3). The bias circuit (201) includes a bias input terminal (IN1), a first chip (U1), a second chip (U2), a third chip (U3), a fourth chip (U4), a first sliding rheostat (R11), and a bias output terminal (OUT1). The input terminal (IN1) is electrically connected to the first chip (U1), the first chip (U1) is electrically connected to the second chip (U2), and the second chip (U2) is electrically connected to the bias output terminal (OUT1). The 90° phase-shifting circuit (202) includes a phase-shifting input terminal (SIN), an adder (U1A), a feedforward integrator (U1B), a feedback integrator (U2A), a second sliding rheostat (R1), a first resistor (R2), a second resistor (R3), a first capacitor (C1), a second capacitor (C2), a third capacitor (C3), a third resistor (R4), a fourth resistor (R5), a first phase-shifting output terminal (OUTA), and a second phase-shifting output terminal (OUTB). The phase-shifting input terminal (SIN) is electrically connected to the negative input terminal of the adder (U1A) through the second sliding rheostat (R1). The negative input terminal of the adder (U1A) is electrically connected to the output terminal of the adder (U1A) through the first resistor (R2). The output terminal of the adder (U1A) is electrically connected to the negative input terminal of the feedforward integrator (U1B) through the second resistor (R3).

2. The high-precision grating micro-displacement sensor based on a 90-degree phase-shifting circuit according to claim 1, characterized in that: The first chip (U1) is electrically connected to the third chip (U3) and the fourth chip (U4) through the first sliding rheostat (R11).

3. A high-precision grating micro-displacement sensor based on a 90-degree phase-shifting circuit according to claim 1, characterized in that: The first chip (U1) uses an LF356M input operational amplifier, the second chip (U2) uses a PA241DW high-voltage power operational amplifier, and the third chip (U3) and the fourth chip (U4) both use LM399H voltage reference IC shunts.

4. A high-precision grating micro-displacement sensor based on a 90-degree phase-shifting circuit according to claim 1, characterized in that: The negative input terminal of the feedforward integrator (U1B) is electrically connected to the output terminal of the feedforward integrator (U1B) through a first capacitor (C1), and the output terminal of the feedforward integrator (U1B) is electrically connected to the second phase-shifted output terminal (OUTB).

5. A high-precision grating micro-displacement sensor based on a 90-degree phase-shifting circuit according to claim 1, characterized in that: The negative input terminal of the adder (U1A) is electrically connected to the output terminal of the feedback integrator (U2A). The negative input terminal of the feedback integrator (U2A) is electrically connected to the output terminal of the feedback integrator (U2A) through a second capacitor (C2). The negative input terminal of the feedback integrator (U2A) is electrically connected to the output terminal of the feedback integrator (U2A) through a third capacitor (C3) and a fourth resistor (R5). The third capacitor (C3) and the fourth resistor (R5) are connected in series. The second capacitor (C2) is connected in parallel with the third capacitor (C3) and the fourth resistor (R5). The negative input terminal of the feedback integrator (U2A) is electrically connected to the second phase-shifted output terminal (OUTB) through a third resistor (R4).

6. A high-precision grating micro-displacement sensor based on a 90-degree phase-shifting circuit according to claim 1, characterized in that: The 10,000-fold subdivision interpolation circuit (203) uses the dedicated DSP interpolator iC-TW8 manufactured by IC-Haus Corporation. The iC-TW8 is a general-purpose 16-bit Sin / Cos interpolator.

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