Thermal control system for adaptive deformable mirror of large-aperture voice coil motor

Abstract

The invention discloses a thermal control system of a large-aperture voice coil motor adaptive deformable mirror. The thermal control system comprises a large-aperture mirror surface, a voice coil motor actuating heating module, a temperature control module and a substrate, the voice coil motor actuating heating module is composed of a coil, an electromagnet, a connecting piece and a coil circuit element. Wherein the coil circuit element is used for supplying power, generating current to flow through the coil, heating the coil and pushing the electromagnet to move due to electromagnetic induction, and the connecting piece of the electromagnet and the mirror body is used for controlling the mirror body to move; the temperature control module comprises a cold column, a cold plate and a flow channel arranged in the cold plate, and the flow channel is of a single-inlet-double-channel-single-outlet structure. Wherein the cold column conducts heat of the coil into the cold plate, and a medium flowing in the runner takes away heat of the cold plate; when the structure is determined, a determined temperature difference exists between the fluid temperature of the flow channel inlet and the environment temperature, so that the overall temperature difference of the substrate is close to 0, and the overall temperature difference of the large-diameter mirror surface is close to 1; the substrate is used for fixing a coil circuit element, serves as a measurement reference of the movement deformation of the mirror body, does not make contact with other structures and is made of non-magnetic metal. According to the invention, the problem of thermal deformation caused by heat accumulation due to insufficient heat dissipation of a current large-aperture foundation telescope voice coil deformable lens can be solved.

Description

Technical Field

[0001] The invention belongs to the technical field of large-aperture adaptive astronomical telescopes, and in particular relates to a thermal control system for a large-aperture voice coil motor adaptive deformable mirror. Background Art

[0002] The turbulence in Earth's atmosphere causes random refraction of starlight as it passes through the atmosphere, blurring telescope images. With the urgent need for high-precision optical observation and control, adaptive optics technology has gradually gained attention.

[0003] In 1953, American astronomer Horace Babcock first proposed the concept of "adaptive optics," envisioning the use of dynamically corrected mirrors to compensate for atmospheric disturbances. In 1989, J.M. Beckers first proposed using an existing telescope secondary mirror as an adaptive secondary mirror. Compared to traditional fixed secondary mirrors, this approach offers the following advantages: improved correction efficiency, enabling direct wavefront correction, avoiding the introduction of aberrations from additional optical components while reducing light energy loss; improved image quality, simultaneous compensation for low- and high-order aberrations, achieving correction over a wide dynamic range; and, in conjunction with wavefront sensors, enabling ground-based telescopes to achieve resolutions approaching the theoretical limit (e.g., 0.02 arc seconds for an 8-meter telescope); and wide-band compatibility.

[0004] Currently, the most widely used deformable mirror technology is the piezoelectric deformable mirror. While it offers excellent precision, it is limited by the inherent properties of piezoelectric ceramics, including hysteresis, making it difficult to achieve both long actuator travel and high dynamic performance. To address this issue, the concept of the voice coil deformable mirror was proposed in the 1990s. Compared to piezoelectric deformable mirrors, it offers advantages such as large travel, high bandwidth, a non-contact mirror surface, and no hysteresis. The basic principle of a voice coil deformable mirror is that current passing through a coil generates a magnetic field. This magnetic field interacts with the magnetic field of a permanent magnet, causing the actuator to generate a thrust or pull force, which acts on the mirror surface, causing it to deform. Due to these advantages, voice coil motor-actuated deformable mirrors are becoming a widely used choice for large-aperture adaptive mirror systems.

[0005] As telescope mirrors continue to grow in size, the number of voice coil motor actuators required for active optical systems is growing exponentially. For example, the European Extremely Large Telescope (ELT) uses over 5,000 actuator units in its segmented mirror. Each actuator relies on an energized coil to generate electromagnetic actuation force. According to Joule's law, the coils inevitably generate Joule heating when continuously energized. When hundreds to thousands of actuators are densely distributed within a limited space, the cumulative effect of their heat power can lead to problems such as deformation of the adaptive mirror system itself, changes in the air seeing near the mirror, and degradation of material properties. Troy A. Rhoadarmer notes in his paper that the thermal deformation of the substrate must be kept within the approximately 25-micron operating range of the actuator and displacement sensor to ensure sufficient travel to compensate for atmospheric turbulence. Furthermore, the temperature difference between the substrate and the ambient environment must be kept within a few tenths of a degree Celsius to prevent thermal gradients from generating additional turbulence in the telescope's pupil plane. Therefore, how to solve the Joule heat accumulation of multiple actuators and reduce its impact on the system is a key issue in the voice coil deformable mirror of large-aperture ground-based telescopes.

[0006] Currently, the world's largest telescopes, including the MMT, LBT, VLT, and GMT, all use liquid-cooled cooling. This design employs a glass-ceramic substrate to support the actuator unit, followed by a metal heat sink behind the glass to dissipate heat. This heat sink is then cooled by refrigerant. However, there is a lack of thermal control systems for voice coil actuator deformable mirrors, both domestically and internationally.

[0007] Therefore, in order to meet the development of large-aperture ground-based telescopes, thermal control system structure design is urgently needed. Summary of the Invention

[0008] The purpose of the present invention is to provide a thermal control system for a large-aperture voice coil motor adaptive deformable mirror to solve the Joule heat accumulation problem of the current large-aperture ground-based telescope voice coil motor actuator.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] The thermal control system for a large-aperture voice coil motor adaptive deformable mirror of the present invention comprises: a large-aperture mirror, a voice coil motor actuation heating module, a temperature control module, and a substrate. The voice coil motor actuation heating module comprises a coil, an electromagnet, a connector, and a coil circuit element. The coil circuit element is used to supply power, generating current flowing through the coil to cause the coil to heat up, and simultaneously, due to electromagnetic induction, driving the electromagnet to move. The connector between the electromagnet and the mirror body is used to control the movement of the mirror body. The temperature control module comprises a cold column, a cold plate, and a flow channel arranged in the cold plate. The flow channel adopts a single-inlet, dual-channel, single-outlet structure. The cold column conducts heat from the coil to the cold plate, and the medium flowing in the flow channel removes heat from the cold plate. When the structure is determined, the fluid temperature at the flow channel inlet has a certain temperature difference from the ambient temperature, so that the overall temperature difference of the substrate is close to 0 and the overall temperature difference of the large-aperture mirror is close to 1. The substrate is used to fix the coil circuit element and also serves as a reference for measuring the movement and deformation of the mirror body. It does not contact other structures and is made of non-magnetic metal.

[0011] A further improvement of the present invention is that the bottom of the cold column is a special-shaped structure for more complete heat transfer with the coil, and its structural type includes but is not limited to structural changes based on increasing the heat conduction area.

[0012] A further improvement of the present invention is that the cooling column has good thermal conductivity, and the material types include but are not limited to metal, ceramic, carbon-based and semiconductor;

[0013] A further improvement of the present invention is that the channel types of the flow channel in the cold plate include but are not limited to annular, serpentine or microchannels, and can be single-layer or multi-layer.

[0014] A further improvement of the present invention is that the cooling medium passing through the flow channel is gas, water or an organic medium.

[0015] A further improvement of the present invention is that the flow channel has a flow channel inlet and a flow channel outlet, the positions of the flow channel inlet and the flow channel outlet can be adjusted, the number of inlet and outlet can be changed, and the flow directions of different flow channels can be the same or opposite.

[0016] A further improvement of the present invention is that thermal grease can be added between the coil and the cold column, and between the cold column and the cold plate, to eliminate air layers generated by incomplete contact during the installation process.

[0017] The working principle of the present invention is: a voice coil motor is used as the actuating unit of a large-aperture adaptive mirror, and a displacement sensor is arranged on the substrate as a reference for the moving distance of the mirror body. Therefore, the substrate needs to have good thermal stability and mechanical strength, and the temperature change of the substrate needs to be reduced in the thermal control system to ensure that the deformation of the substrate does not exceed the range of the displacement sensor. As an optical element, the mirror body needs to maintain good temperature uniformity and a small temperature difference with the ambient temperature. The mirror body material is microcrystalline glass, which has poor thermal conductivity. The substrate material is a non-magnetic metal with a low thermal conductivity coefficient, and there is an air layer between the coil heating element and the substrate, and between the electromagnets, which makes it more difficult to dissipate the heat of the coil heating element. The heat continues to accumulate and the temperature rises. Eventually, the heat will inevitably be transferred to the mirror body and the substrate, causing thermal deformation and affecting the performance of the telescope.

[0018] The present invention adopts a thermal control system structure that combines a cold column and a cold plate. When the surrounding thermal conductivity is low, due to the small thermal resistance of the cold column, the heat of the coil heating element is quickly transferred to the cold plate to achieve effective heat dissipation and prevent the local temperature of the substrate and the mirror body from rising.

[0019] The adaptive deformable mirror of the present invention is combined with optical calibration. A wavefront sensor is used in the telescope optical system to measure the mirror surface shape within a certain time interval and record the mirror surface shape at that time. The position at that time is used as the reference point of the displacement sensor, thereby avoiding the influence of temperature deformation and thermal deformation of the substrate on the mirror position measurement.

[0020] Beneficial Effects: The thermal control system for the adaptive deformable mirror using a large-aperture voice coil motor proposed in this invention utilizes a non-magnetic metal substrate. Compared to glass-ceramic substrates, this material is easier to process and maintain. Its relatively high thermal conductivity prevents localized temperature rise and ensures a more uniform substrate temperature. Although the thermal expansion coefficient increases, the gradual temperature change allows for repositioning through continuous calibration to coordinate with the measurement of mirror deformation.

[0021] In the present invention, the flow channel adopts a single inlet-dual channels-single outlet structure. "Dual channels" means that when the fluid falls vertically from the inlet into the bottom flow channel, it flows in two directions. Compared with the traditional single inlet-single channel-single outlet structure, the fluid can flow more fully in the cold plate, evenly carrying away the heat conducted from adjacent cold columns, and can reduce the temperature difference of the substrate to 1 / 7 of the traditional structure, which is more conducive to maintaining temperature uniformity.

[0022] In the present invention, the temperature difference between the fluid medium temperature and the ambient temperature is strongly correlated with the temperature change of the substrate and the mirror body, and the temperature rise and temperature difference change of the substrate and the mirror body can be obtained by controlling the temperature difference.

[0023] The thermal control system for a large-aperture voice coil motor adaptive deformable mirror proposed in this paper relies on heat conduction and convection to achieve effective heat dissipation. Simulation experiments have verified that it can maintain substrate temperature variations within 1°C and mirror body temperature variations within 2°C, effectively reducing thermal deformation of the mirror and substrate caused by temperature rise. Furthermore, the implementation is simple and easy to maintain, and the thermal control structure can be flexibly adjusted. By varying the structure and materials of the cold column and cold plate, as well as the flow channel structure and flow medium, the inlet cooling medium temperature and flow rate can be adjusted to optimize the heat dissipation design. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art; obviously, the drawings described below are some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0025] Figure 1 2 is a schematic structural diagram of a thermal control system for a large-aperture voice coil motor adaptive deformable mirror according to an embodiment of the present invention;

[0026] Figure 2 It is a schematic diagram of the central cross section of the thermal control system;

[0027] Figure 3 This is a schematic diagram of the voice coil motor actuation heating module;

[0028] Figure 4 It is a schematic diagram of the temperature control module;

[0029] In the figure, 1-cold column; 2-cold plate; 3-flow channel outlet 1; 4-flow channel; 5-substrate; 6-voice coil motor actuated heating module; 7-large-aperture mirror; 8-coil; 9-electromagnet; 10-connector; 11-coil circuit element; 12-flow channel inlet 1; 13-flow channel inlet 2; 14-flow channel outlet 2; 15-temperature control module. DETAILED DESCRIPTION

[0030] To make the purpose, technical effects, and technical solutions of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention are clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention. Based on the embodiments disclosed in the present invention, other embodiments obtained by ordinary technicians in this field without making any creative efforts should fall within the scope of protection of the present invention.

[0031] See also Figure 1-Figure 4The thermal control system of the large-aperture voice coil motor adaptive deformable mirror according to an embodiment of the present invention includes: a large-aperture mirror 7, a voice coil motor actuation heating module 6, a temperature control module 15 and a substrate 5.

[0032] The voice coil motor actuated heating module 6 is composed of a coil 8, an electromagnet 9, a connector 10, and a coil circuit element 11. The coil circuit element 11 is used to supply power, generating current to flow through the coil 8, causing the coil 8 to heat up. At the same time, due to electromagnetic induction, the electromagnet 9 is driven to move. The connector 10 between the electromagnet and the mirror body is used to control the movement of the large-aperture mirror 7.

[0033] The temperature control module includes a cold column 1, a cold plate 2, and a flow channel 4 arranged in the cold plate 2; wherein the cold column 1 transfers the heat of the coil 8 to the cold plate 2, and the medium flowing in the flow channel 4 removes the heat of the cold plate 1;

[0034] The substrate 5 is used to fix the coil circuit element 11 and serves as a measurement reference for the movement and deformation of the mirror body. It does not contact other structures and is made of non-magnetic metal.

[0035] The cold column 1 connects the coil 8 and the cold plate 2. Its bottom is a special-shaped structure, ensuring more efficient heat transfer with the coil 8. Its structural types include, but are not limited to, modifications that increase the heat transfer area. The cold column 1 has excellent thermal conductivity and is made of materials including, but not limited to, metals, ceramics, carbon-based materials, and semiconductors.

[0036] The flow channel 4 in the cold plate 2 adopts a single-inlet, dual-channel, single-outlet structure. Channel types include, but are not limited to, annular, serpentine, or microchannels, and can be single- or multi-layer. The cooling medium flowing through the flow channel 4 can be gas, water, or an organic medium. The flow channel inlets (flow channel inlet 12 and flow channel inlet 2 13) and the flow channel outlets (flow channel outlet 2 14 and flow channel outlet 1 3) are arranged above the cold plate 2. Their position can be adjusted, the number of inlets and outlets can be changed, and the flow directions of different flow channels can be the same or opposite. When the structure is fixed, the flow channel inlet fluid temperature has a certain temperature difference from the ambient temperature, which can ensure that the overall temperature difference of the substrate is close to 0 and the overall temperature difference of the large-diameter mirror is close to 1.

[0037] Thermal grease can be added between the coil 8 and the cold column 1, and between the cold column 1 and the cold plate 2, to eliminate the air layer generated by incomplete contact during the installation process.

[0038] In this invention, during the initial operation of the system, a cooling medium at a constant flow rate below ambient temperature is introduced through the flow channel inlet into the cold plate. Current is then passed through the coil, generating heat, which is rapidly transferred to the cold plate via the cooling column. The cooling medium flowing through the flow channel removes the heat transferred by the coil, preventing the heat from accumulating and transferring to the telescope body and substrate, potentially causing localized thermal deformation and impacting telescope performance. The flow channel can be optimized, and the inlet temperature and flow rate can be controlled in real time.

[0039] In summary, the present invention discloses a thermal control system for a large-aperture voice coil motor adaptive deformable mirror, comprising: a large-aperture mirror, a voice coil motor actuated heating module, a temperature control module, and a substrate; the voice coil motor actuated heating module is composed of a coil, an electromagnet, a connector, and a coil circuit element; wherein the coil circuit element is used to supply power, generating current to flow through the coil, causing the coil to heat up, and at the same time, due to electromagnetic induction, driving the electromagnet to move, and the connector between the electromagnet and the mirror body is used to control the movement of the mirror body; the temperature control module includes a cold column, a cold plate, and a flow channel arranged in the cold plate, the flow channel adopting a single-inlet-dual-channel-single-outlet structure; wherein the cold column conducts heat from the coil to the cold plate, and the medium flowing in the flow channel removes heat from the cold plate; when the structure is determined, the fluid temperature at the flow channel inlet has a certain temperature difference from the ambient temperature, so that the overall temperature difference of the substrate is close to 0 and the overall temperature difference of the large-aperture mirror is close to 1; the substrate is used to fix the coil circuit element and also serves as a reference for measuring the movement and deformation of the mirror body. It does not contact other structures and is made of non-magnetic metal. The present invention can solve the problem of thermal deformation caused by heat accumulation due to insufficient heat dissipation in the current large-aperture ground-based telescope voice coil deformable mirror.

[0040] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the same. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art may still modify or make equivalent substitutions to the specific implementations of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention to be approved.

Claims

1. The thermal control system of the large-aperture voice coil motor adaptive deformable mirror is characterized by: include: Large-aperture mirror, voice coil motor actuated heating module, temperature control module and substrate; The voice coil motor actuation heating module is composed of a coil, an electromagnet, a connector, and a coil circuit element. The coil circuit element is used to supply power, generating current to flow through the coil, causing the coil to heat up. At the same time, due to electromagnetic induction, the electromagnet is driven to move. The connector between the electromagnet and the mirror body is used to control the movement of the large-aperture mirror. The temperature control module includes a cold column, a cold plate, and a flow channel arranged in the cold plate. The flow channel adopts a single-inlet-dual-channel-single-outlet structure. The cold column transfers the heat of the coil to the cold plate, and the medium flowing in the flow channel removes the heat from the cold plate. When the structure is determined, the temperature of the fluid at the flow channel inlet has a certain temperature difference from the ambient temperature, so that the overall temperature difference of the substrate is close to 0 and the overall temperature difference of the large-diameter mirror is close to 1. The substrate is used to fix the coil circuit elements and serves as a measurement benchmark for the movement and deformation of the mirror body. It does not contact other structures and is made of non-magnetic metal.

2. The thermal control system for a large-aperture voice coil motor adaptive deformable mirror according to claim 1, characterized in that: The bottom of the cold column is a special-shaped structure for more complete heat transfer with the coil, and its structural types include but are not limited to structural changes based on increasing the heat conduction area.

3. The thermal control system for the large-aperture voice coil motor adaptive deformable mirror according to claim 1, characterized in that: The cold column has good thermal conductivity, and the material types include but are not limited to metal, ceramic, carbon-based and semiconductor.

4. The thermal control system for a large-aperture voice coil motor adaptive deformable mirror according to claim 1, characterized in that: The channel types of the flow channel in the cold plate include but are not limited to annular, serpentine or microchannels, and can be single-layer or multi-layer.

5. The thermal control system for a large-aperture voice coil motor adaptive deformable mirror according to claim 1, characterized in that: The cooling medium passing through the flow channel is gas, water or organic medium.

6. The thermal control system for the large-aperture voice coil motor adaptive deformable mirror according to claim 1, characterized in that: The flow channel has a flow channel inlet and a flow channel outlet. The flow channel inlet and the flow channel outlet are arranged above the cold plate. The position of the flow channel inlet and the flow channel outlet can be adjusted, the number of inlet and outlet can be changed, and the flow directions of different flow channels can be the same or opposite.

7. The thermal control system for a large-aperture voice coil motor adaptive deformable mirror according to claim 1, characterized in that: Thermal conductive silicone grease can be added between the coil and the cold column, and between the cold column and the cold plate, to eliminate air layers generated by incomplete contact during the installation process.

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