CN114791663B - A heat-absorbing and image-stabilizing lens for astronomical spectrometer cameras based on liquid lenses - Google Patents

Abstract

The invention discloses a heat-eliminating image stabilizing lens of an astronomical spectrometer camera based on a liquid lens, which comprises a fused quartz lens and a calcium fluoride lens, wherein an index matching liquid layer is filled between the fused quartz lens and the calcium fluoride lens, the front surface and the rear surface of the index matching liquid layer are respectively in direct contact with the fused quartz lens and the calcium fluoride lens, the fused quartz lens, the index matching liquid layer and the calcium fluoride lens form a lens triplet structure together, when the curvatures of the front surface and the rear surface of the index matching liquid are the same, the index matching liquid layer is used for eliminating reflection loss of a lens-air interface, and when the curvatures of the front surface and the rear surface of the index matching liquid are different, the index matching liquid layer is equivalent to a liquid lens. The heat-eliminating image-stabilizing lens can keep the imaging image quality of a camera stable under the change of a wide temperature range, and can solve the problem of spectrum line drift of a spectrometer caused when an astronomical optical telescope is observed in an environment with a large temperature difference of an address.

Description

A heat-absorbing and image-stabilizing lens for an astronomical spectrometer camera based on a liquid lens

technical field

The invention belongs to the technical field of astronomical optical instruments, and in particular relates to a heat-absorbing and image-stabilizing lens for an imaging spectrometer camera for an astronomical optical telescope based on a liquid lens.

Background technique

Astronomy is a science promoted by telescopes, and telescopes play an important role in promoting the development of astronomy. The astronomical telescope is the main tool for observing celestial bodies and capturing celestial body information. There are many astronomical instruments at the back end for processing observation signals. As one of the main terminal instruments of the optical telescope, the spectrometer decomposes the polychromatic light collected by the front end of the telescope into spectral lines and images them on the image plane of the detector. A typical astronomical spectrometer system usually includes an entrance slit, a collimating element, a dispersing element, a focusing element and a detector. Among them, the focusing element is a camera imaging system, which is divided into transmission type and reflection type. The transmission type camera includes a series of lenses, and the reflection type camera is composed of different mirrors.

With the design and construction of a new generation of larger-aperture telescopes, the number of medium-to-large astronomical observation spectrometers in the optical band continues to increase in the world, and the replacement time between new and old instruments is rapidly shortening, and the requirements for the precision of optical imaging are getting higher and higher. Optical telescopes are usually installed in high-altitude areas, where the atmosphere is thin, the seeing is good, and there are many clear nights, making them suitable for observation. However, the high-altitude observatory site has a large temperature difference and rapid temperature changes. As a result, the lens inside the spectrometer camera will generate thermal effects and thermal expansion, resulting in imaging drift and directly affecting the imaging effect of the spectrometer.

For the transmission camera system, there are two main methods that can effectively solve the drift of spectrometer imaging with temperature. One is to maintain the focus position through the positive and negative refractive index compensation of multiple sets of cemented lenses. This kind of camera requires a large number of lenses and a long lens barrel; the other is to install a temperature control system on the spectrometer as a whole to reduce the spectral line drift through constant temperature control. , but the structure of the temperature control system is complicated, which will make the overall structure of the spectrometer occupy more of the limited back-end space of the telescope. Therefore, there are fewer telescopes using this method, and it is not suitable for the transformation of old instruments.

Contents of the invention

In order to overcome at least one defect of the above-mentioned prior art, the present invention provides a heat-absorbing and image-stabilizing lens for an astronomical spectrometer camera based on a liquid lens.

To achieve the above object, the present invention provides the following technical solutions:

A heat-absorbing and image-stabilizing lens for an astronomical spectrometer camera based on a liquid lens, comprising a fused silica lens and a calcium fluoride lens, and a refractive index matching liquid is filled between the fused silica lens and the calcium fluoride lens to form a refractive index matching liquid layer, the front and rear surfaces of the refractive index matching liquid layer are in direct contact with the fused silica lens and the calcium fluoride lens respectively, and the fused silica lens, the refractive index matching liquid layer and the calcium fluoride lens together form a lens triplet structure. When the curvatures of the front and rear surfaces of the index matching liquid are the same, the refractive index matching liquid layer is used to eliminate the reflection loss of the lens-air interface; when the curvatures of the front and rear surfaces of the refractive index matching liquid are different, the refractive index matching liquid layer is equivalent to A liquid lens.

Further, the refractive index matching liquid is Cargille LL5610 laser liquid.

Further, the fused silica lens includes a first fused silica lens and a second fused silica lens, the refractive index matching liquid layer includes a first refractive index matching liquid layer and a second refractive index matching liquid layer, and the calcium fluoride The lens is interposed between the first fused silica lens and the second fused silica lens, the first refractive index matching liquid layer is filled between the first fused silica lens and the calcium fluoride lens, and the second The second refractive index matching liquid layer is filled between the fused silica lens and the calcium fluoride lens.

Further, the first fused silica lens and the second fused silica lens are spaced apart by an inner cylindrical ring, and the outer side of the lens triplet structure is clamped and limited by an outer cylindrical ring, and the fused silica lens and the inner cylindrical ring Both the contact position and the contact position between the fused silica lens and the outer cylindrical ring are provided with an isolation patch, the inner cylindrical ring indirectly contacts the fused silica lens through the isolation patch and exerts an axial force, and the outer cylindrical ring passes through the isolation patch. The patch is in indirect contact with the fused silica lens and applies an axial force.

Further, the inner cylindrical ring is an aluminum cylindrical ring, the outer cylindrical ring is a titanium cylindrical ring, and the isolation patch is a polyimide patch.

Further, an outer sealing ring is provided between the outer cylindrical ring and the fused silica lens, an inner sealing ring is provided at the junction of the calcium fluoride lens and the inner cylindrical ring, and a useful sealing ring is provided on the side wall of the inner cylindrical ring. The through hole through which the refractive index matching liquid flows, the outer sealing ring is used to seal the refractive index matching liquid and provide radial force to the fused silica lens, and the calcium fluoride lens is constrained by the inner cylindrical ring and the inner sealing ring.

Further, the outer sealing ring is a Parker 2-361 type O-ring, and the inner sealing ring is a Parker 2-159 type O-ring.

Further, the volume adiabatic of the adiabatic image stabilization lens satisfies:

Among them, ΔV _Ti , ΔV _Al , ΔV _CaF2 , ΔV _Silica and ΔV _O-ring are the corresponding volume changes of titanium, aluminum, calcium fluoride, fused silica and all sealing rings respectively, and substituting the coefficient of thermal expansion, we can get:

Among them, V _Ti , V _Al , V _CaF2 , V _Silica and _VO-ring are the corresponding volumes of titanium, aluminum, calcium fluoride, fused silica and all sealing rings respectively, α _Ti , α _Al , α _CaF2 and α _Silica are respectively is the linear thermal expansion coefficient corresponding to titanium, aluminum, calcium fluoride and fused silica, and β _O-ring is the volumetric thermal expansion coefficient of the sealing ring.

Compared with prior art, the beneficial effect of the present invention is:

Utilizing the heat-absorbing and image-stabilizing lens of the astronomical spectrometer camera based on the liquid lens of the present invention can realize that the imaging quality of the camera remains stable under wide temperature range changes, and can solve the problem of astronomical optical telescopes observing in environments with large site temperature differences. The problem of spectral line drift caused by the spectrometer.

Description of drawings

Fig. 1 is a structural schematic diagram of a heat-absorbing and image-stabilizing lens;

Fig. 2 is a schematic diagram of the optical path of the spectrometer camera optical system with a heat-absorbing and image-stabilizing lens;

Fig. 3 is a schematic diagram showing the variation of the refractive index of the refractive index matching liquid with temperature in the heat-absorbing and image-stabilizing lens;

Fig. 4 is a schematic diagram of the image quality of a spectrometer camera with an adiabatic image stabilization lens at different temperatures;

Marks in the figure: 1. Heat-absorbing and image-stabilizing lens; 101. First fused silica lens; 102. Second fused silica lens; 2. Calcium fluoride lens; 301. First refractive index matching liquid layer; 302. Second refraction 4. Inner cylindrical ring; 401. Through hole; 5. Isolation patch; 6. Outer cylindrical ring; 7. Outer sealing ring; 8. Inner sealing ring; 9. The third fused silica lens; 10. The fourth fused silica lens; 11, CCD.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings.

This embodiment provides a heat dissipation device that can keep the image quality of the camera stable under wide temperature range changes, and can solve the problem of spectral line drift of the spectrometer when the astronomical optical telescope observes in an environment with a large temperature difference at the site. Stabilized lens. In optics, the refractive index of fused silica (Fused Silica) increases with the increase of temperature, and the refractive index of calcium fluoride (CaF ₂ ) decreases with the increase of temperature, but the refractive index of the two changes slowly with temperature, while The refractive index of the Refractive Index Matching Fluid (RIMF for short) changes relatively quickly with temperature. The curvature and thickness of each lens are optimized through optical design simulation, and the phase change of fused silica and calcium fluoride lenses caused by thermal effects can be compensated by the refractive index matching liquid to achieve optical heat dissipation. Mechanically, the thermal expansion of the fused silica, calcium fluoride, refractive index matching liquid and lens spacer material inside the lens must match the thermal expansion of the mirror material outside the lens to achieve heat dissipation in the mechanical structure. Through optical and mechanical heat dissipation, the purpose of image stabilization of the spectrometer camera is finally achieved.

In this embodiment, a heat-absorbing and image-stabilizing lens of an astronomical spectrometer camera based on a liquid lens includes a fused silica lens and a calcium fluoride lens, and a thin layer of refractive index matching liquid is filled between the fused silica lens and the calcium fluoride lens. , forming a layer of refractive index matching liquid, the front and rear surfaces of the refractive index matching liquid layer are in direct contact with the fused silica lens and the calcium fluoride lens respectively, then the shape and curvature of the front and rear surfaces of the refractive index matching liquid are consistent with the contact lens surface, melting The quartz lens, the refractive index matching liquid layer and the calcium fluoride lens together form a lens triplet structure. When the curvature of the front and rear surfaces of the refractive index matching liquid is the same, it mainly plays the role of eliminating the reflection loss of the lens-air interface; when the curvature of the front and rear surfaces of the refractive index matching liquid is different, the refractive index matching liquid layer can be regarded as A lens, hence the name liquid lens. Specifically, as shown in Figure 1, the fused silica lens in this embodiment is provided with two pieces, namely a first fused silica lens 101 and a second fused silica lens 102, and the calcium fluoride lens 2 is sandwiched between the first fused silica lens 101 and the second fused silica lens 102, correspondingly, there are two layers of refractive index matching liquid in the whole lens group, that is, the layer between the first fused silica lens 101 and the calcium fluoride lens 2 is filled with the first refractive index matching liquid layer 301 , a second refractive index matching liquid layer 302 is filled between the second fused silica lens 102 and the calcium fluoride lens 2 . Refractive index matching liquid is often used between multiple optical devices, or on one or more outer surfaces of a single optical device to improve the optical performance of the interface in contact with air. The refractive index of the refractive index matching liquid should be consistent with that of the optical device itself. The refractive index is close to achieve the best effect of improving optical performance. The thickness of the refractive index matching liquid layer is usually millimeter to micron order. In this embodiment, the preferred Cargille LL5610 type laser liquid (Laser Liquid) is used as the refractive index matching liquid; this implementation Example preferably the central thickness h _Silica-1 of the first fused silica lens 101 is 16 mm; the central thickness h _Silica-2 of the second fused silica lens 102 is 18 mm; the central thickness h _CaF2 of the calcium fluoride lens is 46 mm; each layer of laser liquid The center thickness of _LaserLiquid is 0.065mm.

In order to make the fused silica lens, the refractive index matching liquid layer and the calcium fluoride lens form the lens triplet structure efficiently, this embodiment is further provided with an inner cylindrical ring 4 and an outer cylindrical ring 6 . Specifically as shown in Figure 1, the first fused silica lens 101 and the second fused silica lens 102 are spaced apart by the inner cylindrical ring 4, the outside of the lens triplet structure is clamped and limited by the outer cylindrical ring 6, and the fused silica lens and the inner cylinder The contact position of the ring 4 and the contact position of the fused silica lens and the outer cylindrical ring 6 are all provided with an isolation patch 5, and the inner cylindrical ring 4 indirectly contacts with the fused silica lens through the isolation patch 5 and exerts an axial force, and the outer cylindrical ring 6 The indirect contact with the fused silica lens through the isolation patch 5 applies an axial force. In this embodiment, the preferred lens material inside the lens is aluminum (Al) cylindrical ring as the inner cylindrical ring 4, the preferred polyimide (Polyimide, referred to as PI) patch as the isolation patch 5, and the preferred lens external lens material is titanium ( Ti) Cylindrical ring as outer cylindrical ring 6 . In this embodiment, the inner diameter φ _{Al_in} of the aluminum cylindrical ring is preferably 136 mm, the outer diameter φ _{Al_out} is 155 mm, the inner diameter φ _{Ti_in} of the titanium cylindrical ring is 155 mm, and the outer diameter φ _{Ti_out} is 163.7 mm.

In this embodiment, the outer sealing ring 7 and the inner sealing ring 8 are used to seal the refractive index matching liquid. Specifically as shown in Figure 1, the outer sealing ring 7 is arranged between the outer cylindrical ring 6 and the fused silica lens, the outer sealing ring 7 is used to seal the refractive index matching liquid and provide radial force to the fused silica lens, and the inner sealing ring 8 is arranged At the junction of the calcium fluoride lens 2 and the inner cylindrical ring 4, the calcium fluoride lens 2 is constrained by the inner cylindrical ring 4 and the inner sealing ring 8, and the side wall of the inner cylindrical ring 4 is provided with a seal for when the lens expands with heat and contracts with cold. The through hole 401 through which the refractive index matching liquid flows. In this embodiment, the preferred Parker 2-361 type O-ring is used as the outer sealing ring 7, and its cross-sectional diameter is 5.33 mm. The preferred Parker 2-159 type O-ring is used as the inner sealing ring 8, and its cross-sectional diameter is 2.62 mm. .

In order to realize the optical heat reduction of the heat dissipation and image stabilization lens, the camera optical system of the heat dissipation and image stabilization lens of this embodiment is simulated with Zemax software, including the heat dissipation and image stabilization lens 1 of the above-mentioned liquid lens-based astronomical spectrometer camera. The optical paths of the three fused silica lenses 9, the fourth fused silica lens 10, and the CCD 11 are shown in FIG. 2 . The parallel light beam with a diameter of 100 mm is incident on the athermal image stabilization lens 1, passes through the third fused silica lens 9 and the fourth fused silica lens 10, and forms an image on the target surface of the CCD 11. The refractive index of the fused silica on both sides of the heat-absorbing image stabilization lens increases with the increase of temperature, and the refractive index of calcium fluoride decreases with the increase of temperature, but the refractive index of the two changes slowly with temperature, while the refractive index of the laser liquid The change with temperature is relatively fast. The change of the refractive index of Cargille LL5610 laser liquid with temperature is shown in Figure 3. By optimizing the curvature and thickness of each lens, the phase change of the fused silica and calcium fluoride lenses due to thermal effects is compensated by the laser liquid. In the wide range of operating temperatures from -10°C to 30°C, the camera maintains excellent image quality. The root mean square value of the imaging spot radius of each field of view on the CCD11 target surface is shown in Figure 4. After optimization, the specific parameters of each component of the liquid lens are shown in Table 1. The height h _Ti of the titanium cylindrical ring is the desired value, which is calculated by volume abatement.

Table 1 Specific parameters of each component of the liquid lens, unit: mm.

In order to achieve heat dissipation in the mechanical structure of the liquid lens camera, the thermal expansion of the total volume of quartz, calcium fluoride, interlayer material aluminum, laser fluid and O-ring inside the lens must match the thermal expansion of the external mirror material titanium. When calculating volume heat dissipation, the volume of aluminum, the interlayer material inside the lens, is the actual volume of the inner cylindrical ring 4, and when calculating the volume of titanium, the outer lens material, titanium should be regarded as a cylinder instead of the actual volume of the outer cylindrical ring 6 . The laser liquid in this embodiment can flow through the through hole on the aluminum cylinder wall when thermal expansion occurs inside the lens, so the thermal expansion of the volume of the laser liquid will not act on the external mirror vector. Then the volumetric heat dissipation of the heat dissipation image stabilization lens needs to satisfy:

Among them, ΔV _Ti , ΔV _Al , ΔV _CaF2 , ΔV _Silica and ΔV _O-ring are the corresponding volume changes of titanium, aluminum, calcium fluoride, fused silica and all sealing rings respectively, and substituting the coefficient of thermal expansion, we can get:

Among them, V _Ti , V _Al , V _CaF2 , V _Silica and _VO-ring are the corresponding volumes of titanium, aluminum, calcium fluoride, fused silica and all sealing rings respectively, α _Ti , α _Al , α _CaF2 and α _Silica are respectively is the linear thermal expansion coefficient corresponding to titanium, aluminum, calcium fluoride and fused silica, and β _O-ring is the volumetric thermal expansion coefficient of the sealing ring.

According to the specific parameters of each element of the liquid lens in Table 1, the height of the external mirror vector titanium is calculated as h _Ti =57.2mm.

To sum up, in this embodiment, the heat dissipation and image stabilization lens of the astronomical spectrometer camera based on the liquid lens realizes optical heat dissipation by using a refractive index matching liquid to compensate the phase change of the lens due to temperature. The volumetric thermal expansion of the internal components of the lens matches the volumetric thermal expansion of the external lens vector to achieve heat dissipation in the mechanical structure. Through the athermalization of the optical and mechanical camera lens, the imaging quality of the camera can be kept stable under a wide temperature range.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (5)

1. The heat elimination image stabilization lens of the astronomical spectrometer camera based on the liquid lens is characterized by comprising a fused quartz lens and a calcium fluoride lens, wherein refractive index matching liquid is filled between the fused quartz lens and the calcium fluoride lens to form refractive index matching liquid layers, the front surface and the rear surface of each refractive index matching liquid layer are respectively in direct contact with the fused quartz lens and the calcium fluoride lens, the fused quartz lens, the refractive index matching liquid layers and the calcium fluoride lens jointly form a lens triplet structure, when the curvatures of the front surface and the rear surface of each refractive index matching liquid are the same, the refractive index matching liquid layers are used for eliminating reflection losses of a lens-air interface, and when the curvatures of the front surface and the rear surface of each refractive index matching liquid are different, the refractive index matching liquid layers are equivalent to one liquid lens;

the refractive index matching liquid is a Cargille LL5610 type laser liquid;

the fused quartz lenses comprise a first fused quartz lens and a second fused quartz lens, the refractive index matching liquid layer comprises a first refractive index matching liquid layer and a second refractive index matching liquid layer, the calcium fluoride lens is clamped between the first fused quartz lens and the second fused quartz lens, the first refractive index matching liquid layer is filled between the first fused quartz lens and the calcium fluoride lens, and the second refractive index matching liquid layer is filled between the second fused quartz lens and the calcium fluoride lens;

the first fused quartz lens and the second fused quartz lens are spaced apart through an inner cylindrical ring, the outer side of the lens triplet structure is clamped and limited through an outer cylindrical ring, isolation patches are arranged at the contact positions of the fused quartz lens and the inner cylindrical ring and the contact positions of the fused quartz lens and the outer cylindrical ring, the inner cylindrical ring is indirectly contacted with the fused quartz lens through the isolation patches and applies axial force, and the outer cylindrical ring is indirectly contacted with the fused quartz lens through the isolation patches and applies axial force;

the inner cylindrical ring is an aluminum cylindrical ring, and the outer cylindrical ring is a titanium cylindrical ring;

the specific parameters of the elements of the heat-eliminating image-stabilizing lens are as follows, and the units are as follows: the length of the air flow is in the range of mm,

h _Ti ＝57.2mm。

2. the liquid lens-based athermal image stabilization lens of an astronomical spectrometer camera of claim 1, wherein the isolation patch is a polyimide patch.

3. The astronomical spectrometer camera heat elimination and image stabilization lens based on a liquid lens according to claim 1 or 2, characterized in that an outer sealing ring is arranged between the outer cylindrical ring and the fused quartz lens, an inner sealing ring is arranged at the junction of the calcium fluoride lens and the inner cylindrical ring, a through hole for flowing an index matching liquid is arranged on the side wall of the inner cylindrical ring, the outer sealing ring is used for sealing the index matching liquid and providing radial force for the fused quartz lens, and the calcium fluoride lens is restrained by the inner cylindrical ring and the inner sealing ring.

4. A lens for eliminating heat and stabilizing images of an astronomical spectrometer camera based on a liquid lens according to claim 3, wherein the outer sealing ring is a Parker 2-361 type O-ring, and the inner sealing ring is a Parker 2-159 type O-ring.

5. The heat elimination and image stabilization lens of an astronomical spectrometer camera based on a liquid lens according to claim 4, wherein the volume heat elimination of the heat elimination and image stabilization lens satisfies the following:

wherein DeltaV _Ti ，ΔV _Al ，ΔV _CaF2 ，ΔV _Silica And DeltaV _O-ring The volume changes corresponding to titanium, aluminum, calcium fluoride, fused quartz and all sealing rings are substituted into the thermal expansion coefficients, so that the method is obtained:

wherein V is _Ti ，V _Al ，V _CaF2 ，V _Silica And V _O-ring Respectively titanium, aluminum, calcium fluoride and molten stoneCorresponding volumes of quartz and all sealing rings, alpha _Ti ，α _Al ，α _CaF2 And alpha _Silica Linear thermal expansion coefficients corresponding to titanium, aluminum, calcium fluoride and fused quartz respectively, beta _O-ring Is the volume thermal expansion coefficient of the sealing ring.

Images