Michelson interference device and control method

Abstract

The invention discloses a Michelson interference device and a control method, and relates to the technical field of Michelson interferometers. The device comprises an interference unit, a detection unit, a first feedback unit, a second feedback unit and a control unit, the first feedback unit adopts an absolute grating ruler to measure position information of a moving mirror in the interference unit in real time, and the second feedback unit adopts an incremental grating ruler to output a sampling clock signal and speed information of the moving mirror in the interference unit. By introducing the first feedback unit and the second feedback unit, the actual position and speed information of the moving mirror in the interference unit can be measured in real time, the control effect of the moving mirror is improved, and meanwhile, the environmental adaptability of the Michelson interference device is also improved by using the grating ruler.

Description

Technical Field

[0001] The present invention belongs to the technical field of Michelson interferometers, and in particular relates to a Michelson interferometer device based on dual grating scale position and speed feedback and a control method. Background Art

[0002] The Michelson interferometer uses a beam splitter to split a beam of light into two, which then travel along two separate optical paths and then reunite at the beam splitter. When the two beams meet, they interfere with each other, forming alternating light and dark interference fringes on the screen as the moving mirror moves.

[0003] Therefore, the Michelson interferometer must have the movement of the moving mirror to complete the interference function. The traditional moving mirror position and speed control technology mainly uses the laser signal of the He-Ne laser to generate a cosine wave after passing through the interference system. The position and speed are read and controlled by analyzing this signal. However, the operating temperature of the He-Ne laser needs to be controlled within the normal temperature range to ensure stable output power and a long service life. Therefore, in order to make the product adapt to industrial environments with a wide temperature range, the laser needs to be placed in a constant temperature device, which will greatly increase the size, weight and complexity of the product. In addition, the position read by the He-Ne laser is actually the displacement of the moving mirror relative to the initial position. In applications in complex environments, as the initial position changes, when the actual position of the moving mirror deviates from the actual sampling interval, it will affect the correct sampling of the interference pattern. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the object of the present invention is to provide a Michelson interferometer device and control method based on dual grating scale position and velocity feedback, which is used to solve the problem in the prior art that the operating temperature of the Michelson interferometer is limited due to the use of HeNe laser, and the actual position of the moving mirror deviates from the actual sampling interval, thereby affecting the correct sampling of the interference pattern.

[0005] To achieve the above object, the technical solution of the present invention is: A Michelson interferometer comprises an interference unit, a detection unit, a feedback unit and a control unit, wherein the feedback unit comprises a first feedback unit and a second feedback unit.

[0006] The first feedback unit uses an absolute grating ruler to collect position information of the moving mirror in the interference unit.

[0007] The second feedback unit uses an incremental grating ruler to collect speed information of the moving mirror in the interference unit and provide an interference pattern sampling signal.

[0008] Optionally, the interference unit includes a motor, a moving mirror, a fixed mirror, a beam splitter, a lens, and a compensation mirror.

[0009] Optionally, the control unit receives feedback signals from the absolute grating ruler and the incremental grating ruler, and outputs a driving voltage for the motor according to a PID algorithm.

[0010] Optionally, the motor is a linear voice coil motor.

[0011] Optionally, the movable mirror can slide linearly on the guide rail after being connected to the slider via a bracket.

[0012] Optionally, the movable mirror and the fixed mirror are corner mirrors.

[0013] Optionally, the detection unit uses a mercury cadmium telluride long-wave infrared detector.

[0014] A method for controlling a Michelson interferometer device, wherein a moving mirror is controlled according to the Michelson interferometer device, and the method comprises the following steps: Step 1: The control unit determines the current working state. If it is a scanning state, it proceeds to step 2. Step 2: Determine whether the current scanning state is the first scanning. If so, proceed to step 3; otherwise, proceed to step 4. Step 3, reading the current position of the moving mirror by the absolute grating ruler, calculating the distance to the zero point of the optical path difference, if the distance is greater than zero, setting the scanning direction to reverse, and proceeding to step 5; otherwise, setting the scanning direction to forward, and proceeding to step 4; Step 4: Determine whether the current limit position has been reached. If not, set the forward target speed, calculate the output voltage using a PID algorithm, and the control unit outputs PWM to drive the linear voice coil motor. If the limit position has been reached, set the scanning direction to reverse, and proceed to step 1. Step 5: Determine whether the current limit position has been reached. If not, set a reverse target speed, calculate the output voltage using a PID algorithm, and output PWM to the linear voice coil motor using the control unit. If the limit position has been reached, set the scanning direction to forward, and proceed to step 1. Beneficial effects of the present invention: (1) Absolute and incremental grating scales are used to read the position and speed of the moving mirror, which improves the adaptability of the Michelson interferometer to the ambient temperature and reduces space costs; (2) The position of the moving mirror is read in real time by an absolute grating ruler, so that the moving mirror does not deviate from the correct sampling interval during the sampling process, ensuring the correct sampling of the interference pattern. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Shown is a block diagram of the composition of a Michelson interferometer device provided by the present invention.

[0016] Figure 2 Shown is a structural schematic diagram of a Michelson interferometer provided by the present invention.

[0017] Figure 3 Shown is a control flow chart of a Michelson interferometer provided by the present invention.

[0018] The reference numerals in the figures are: Interference unit 10, motor 101, moving mirror 102, fixed mirror 103, beam splitter 104, lens 105; Detection unit 20; Feedback unit 30, first feedback unit 301, absolute grating ruler 3011, second feedback unit 302, incremental grating ruler 3021; Control unit 40. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0020] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for understanding and reading by those familiar with this technology, and are not used to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modification of the structure, change in the proportional relationship, or adjustment of the size should still fall within the scope of the technical content disclosed by the present invention without affecting the efficacy and purpose that can be achieved by the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" quoted in this specification are only for the convenience of description and are not used to limit the scope of the implementation of the present invention. Changes or adjustments in their relative relationships should also be regarded as the scope of the implementation of the present invention without substantially changing the technical content.

[0021] The following embodiments are for illustration only and can be combined with each other, and are not limited to the contents presented in the following single embodiments.

[0022] For this example, please refer to Figures 1 to 3 The present invention provides a Michelson interferometer device and control method based on dual grating scale position and speed feedback.

[0023] like Figure 1 and Figure 2As shown, a Michelson interference device includes an interference unit 10, a detection unit 20, a feedback unit 30, and a control unit 40, the feedback unit includes a first feedback unit 301 and a second feedback unit 302.

[0024] In this embodiment, the first feedback unit 301 adopts an absolute grating ruler 3011 for collecting the position information of the moving mirror 102 in the interference unit 10. The absolute grating ruler can detect the absolute position of the moving mirror and the positive or negative offset of the moving mirror relative to the zero point when the interference device starts to power on, so that the controller can conveniently control the moving direction of the moving mirror. In addition, the absolute grating ruler can also provide a signal of the moving mirror passing through the zero point, and the resolution of the absolute grating ruler is 0.01 um.

[0025] In this embodiment, the second feedback unit 302 adopts an incremental grating ruler 3021 for collecting the speed information of the moving mirror 102 in the interference unit 10 and providing an interference pattern sampling signal, and the resolution of the incremental grating ruler is 2 nm.

[0026] In this embodiment, the interference unit 10 includes a motor 101, a moving mirror 102, a fixed mirror 103, a beam splitter 104, and a lens 105. Wherein, the infrared incident light is divided into two beams after passing through the beam splitter 104, one beam is incident to the fixed mirror 103, and the other beam is incident to the moving mirror 102. Since the reflected light of the moving mirror is parallel to the incident light, the reflected light returns to the beam splitter 104. The other beam reflected by the beam splitter 104 undergoes a similar process and also returns to the beam splitter 104. Due to the movement of the moving mirror 102, there is a path difference between the two beams, forming an interference light signal. The compensation mirror 106 is used to eliminate the path difference introduced by the beam splitter 104. The lens 105 is responsible for converging the interference light to the detection unit 20.

[0027] In this embodiment, the feedback signal of the absolute grating ruler 3011 adopts SSI protocol, conforms to the standard RS-422 interface, is converted into SPI signal which can be collected by the MCU through the RS422 level conversion chip, and the feedback signal of the incremental grating ruler 3021 is TTL differential signal. The two kinds of differential signals are transmitted in the form of square wave pulse signals with a phase difference of 90° electronic angle. The phase difference reflects the moving direction of the moving mirror. The control unit 40 receives the feedback signals of the absolute grating ruler 3011 and the incremental grating ruler 3021, and outputs the driving voltage of the motor according to the PID algorithm.

[0028] In this embodiment, the motor 101 adopts a linear voice coil motor. The voice coil motor has the advantages of high linearity and fast response, which improves the control ability of the moving mirror. The mechanical time constant of the selected voice coil motor is only 1.7 ms, and the response speed is relatively high, which can better cope with external disturbances.

[0029] In this embodiment, the movable mirror 102 is connected to the slider via a bracket and can slide linearly on the guide rail.

[0030] In this embodiment, the moving mirror 102 and the fixed mirror 103 use corner mirrors, which can make the incident light and the outgoing light parallel. Even if the three-dimensional corner mirror is slightly offset along the vertical direction of the guide rail during the movement of the moving mirror, it can still ensure that the incident light and the outgoing light are absolutely parallel. Therefore, there is no need for complex and delayed dynamic adjustments during operation, which improves the anti-interference ability.

[0031] In this embodiment, the detection unit 20 uses a mercury cadmium telluride long-wave infrared detector, which can convert the interference light signal into an electrical signal.

[0032] In this embodiment, the method includes the following steps: Step 1: The control unit 40 determines the current working state. If it is a scanning state, it proceeds to step 2. Step 2: Determine whether the current scanning state is the first scanning. If so, proceed to step 3; otherwise, proceed to step 4. Step 3: Read the current position of the moving mirror 102 through the absolute grating ruler 3011 and calculate the distance to the zero point of the optical path difference. If the distance is greater than zero, the scanning direction is set to reverse and the process proceeds to step 5. Otherwise, the scanning direction is set to forward and the process proceeds to step 4. Step 4: Determine whether the current limit position has been reached. If not, set the forward target speed, calculate the output voltage using the PID algorithm, and the control unit 40 outputs PWM to drive the linear voice coil motor 101. If the limit position has been reached, the scanning direction is set to reverse, and proceed to step 1. Step 5: Determine whether the current limit position has been reached. If not, set the reverse target speed, calculate the output voltage through the PID algorithm, and the control unit 40 outputs PWM to drive the linear voice coil motor 101. If the limit position has been reached, the scanning direction is set to forward, and enter step 1.

[0033] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A Michelson interferometer device, characterized in that: It comprises an interference unit (10), a detection unit (20), a feedback unit (30) and a control unit (40), wherein the control unit (40) is electrically connected to the detection unit (20) and the feedback unit (30), respectively; The interference unit (10) includes a motor (101), a movable mirror (102), a fixed mirror (103), a beam splitter (104), a lens (105), and a compensation mirror (106). The incident infrared light is split into two beams after passing through the beam splitter (104), one beam of light is incident on the fixed mirror (103), and the other beam of light is incident on the movable mirror (102); the light reflected by the movable mirror (103) is parallel to the incident light, and the reflected light returns to the beam splitter (104); the light reflected by the movable mirror (102) is parallel to the incident light, and the reflected light returns to the beam splitter (104); the movement of the movable mirror (102) forms an interference light signal; the compensation mirror (106) is used to eliminate the optical path difference introduced by the beam splitter (104); the lens (105) is used to converge the interference light to the detection unit (20); the motor (101) is used to drive the movable mirror (102) to move horizontally along the direction of the incident infrared light; The feedback unit (30) comprises a first feedback unit (301) and a second feedback unit (302); the first feedback unit (301) adopts an absolute grating ruler (3011) for detecting the absolute position of the moving mirror (103), the positive and negative offsets of the moving mirror (103) relative to the zero point, and the signal of the moving mirror crossing the zero point when the interference device starts to be powered on; the second feedback unit (302) adopts an incremental grating ruler (3021) for collecting speed information of the moving mirror (102) in the interference unit (10) and providing an interference pattern sampling signal; The control unit (40) receives feedback signals from the absolute grating ruler (3011) and the incremental grating ruler (3021) and controls the movement direction of the moving mirror (103).

2. A Michelson interferometer device according to claim 1, characterized in that: The absolute grating ruler (3011) The resolution of the absolute grating ruler (3011) is 0.01 μm; the resolution of the incremental grating ruler (3021) is 2 nm.

3. The Michelson interferometer device according to claim 1, wherein: The moving mirror (102) is connected to the slider via a bracket and can slide linearly on the guide rail.

4. The Michelson interferometer device according to claim 1, wherein: The moving mirror (102) and the fixed mirror (103) are corner mirrors.

5. The Michelson interferometer device according to claim 1, characterized in that: The feedback signal of the absolute grating ruler (3011) adopts the SSI protocol, conforms to the standard RS-422 interface, and is converted into an SPI signal that can be collected by the MCU of the control unit (40) through the RS422 level conversion chip.

6. The Michelson interferometer device according to claim 1, characterized in that: The feedback signal of the incremental grating ruler (3021) is a TTL differential signal that can be collected by the MCU of the control unit (40). The two differential signals are transmitted as square wave pulse signals with a phase difference of 90° electronic angle. The phase difference reflects the moving direction of the moving mirror.

7. A Michelson interferometer device according to any one of claims 1 to 6, characterized in that: The motor (101) is a linear voice coil motor.

8. A Michelson interferometer device according to any one of claims 1 to 6, characterized in that: The detection unit (20) uses a mercury cadmium telluride long-wave infrared detector for converting the interference light signal into an electrical signal.

9. A method for controlling a Michelson interferometer, according to any one of claims 1 to 8, characterized in that: The moving mirror is controlled, and the control method includes the following steps: Step 1: the control unit (40) determines the current working state, and if it is a scanning state, proceeds to step 2; Step 2: Determine whether the current scanning state is the first scanning. If so, proceed to step 3; otherwise, proceed to step 4. Step 3, reading the current position of the moving mirror (102) by the absolute grating ruler (3011), calculating the distance to the zero point of the optical path difference, if the distance is greater than zero, setting the scanning direction to reverse, and proceeding to step 5; otherwise, setting the scanning direction to forward, and proceeding to step 4; Step 4: determine whether the current limit position has been reached. If the limit position has not been reached, set the forward target speed, calculate the output voltage through the PID algorithm, and the control unit (40) outputs PWM to drive the linear voice coil motor (101); if the limit position has been reached, set the scanning direction to reverse, and proceed to step 1; Step 5: Determine whether the current limit position has been reached. If the limit position has not been reached, set the reverse target speed, calculate the output voltage through the PID algorithm, and the control unit (40) outputs PWM to drive the linear voice coil motor (101); if the limit position has been reached, set the scanning direction to forward, and enter step 1.

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