Optical sensor for in-situ detection of dust in deep space

Abstract

An optical sensor for deep space cosmic dust in-situ detection comprises a system shell, a spherical cylindrical lens, a total reflection mirror, a diaphragm, a Powell prism and a semiconductor laser are installed in the system shell, and a laser shaping and collimating module is formed by the Powell prism and the semiconductor laser. A scattered light acquisition and photoelectric conversion module is formed by the Wetton cone array, the photodiode, the signal processing terminal and the band-pass filter, and a laser trap is arranged in front of the detection light curtain emitted from the spherical cylindrical lens; when dust particles entering the sensor from the opening of the shell penetrate through the detection sensitive area, scattered light is generated under laser irradiation, the scattered light passes through the band-pass filter and then is collected and converged by the Wetton cone, and then the scattered light is converted into an electric signal with certain intensity by the photodiode; after the electric signal is amplified and processed by the signal processing terminal, relevant information such as particle size of the particles can be inverted; the method has the advantages of non-contact, no damage to particle dynamic characteristics, large detection area, no additional external bias voltage, high detection precision and the like.

Description

Technical Field

[0001] The present invention relates to the field of deep space detection technology, and in particular to an optical sensor for in-situ detection of deep space cosmic dust. Background Art

[0002] Cosmic dust is tiny matter floating in the universe. It is a tangible solid particle with a diameter ranging from submicron to millimeter. Cosmic dust contains rich information about the evolution of the universe and celestial bodies. Studying the physical and chemical properties of cosmic dust, including spatial distribution, particle size distribution, and composition, is an important way to explore the evolution of the universe. At the same time, the existence of cosmic dust also brings many challenges and threats to human deep space exploration activities. For example, cosmic dust accumulates on the solar panels of spacecraft, which will weaken the ability of the panels to receive sunlight and have an adverse effect on the energy supply of the aircraft. Therefore, studying the characteristics of tiny dust in space has important scientific and engineering significance, making it one of the key contents that has been widely concerned in the current field of deep space exploration.

[0003] Dust particle detection technology based on light scattering theory is an effective technology for detecting the particle size and concentration of dust particles. Its working principle is: when dust particles pass through the detection light curtain, the dust particles scatter light under the illumination of the light curtain. By collecting and measuring the scattered light signal at a certain angle, the dust characteristics related to the scattered light signal can be inverted. At present, most dust particle detection technology solutions used for atmospheric dust detection are: based on the air pump exhaust method, the sampling airflow is used to drive the particles to be tested into the detection area, the particles to be tested are scattered with the detection light, and the scattered light is collected by a lens or a spherical reflector and converged on the photoelectric detector located at the conjugate image point of the detection area. A pulse electrical signal proportional to the scattered light intensity is obtained through photoelectric conversion. The amplitude of the pulse signal is positively correlated with the size of the particles, and the number of pulses corresponds to the number of particles. Based on the number of particles detected in the unit volume of the sampled gas, the concentration of the particles can be given (Publication No.: CN219870874U, Name: A dust particle counter with a high signal-to-noise ratio; Publication No.: CN 1570604A, Name: Micro-optical sensor for laser dust particle counter); This technical solution has the disadvantages of being dependent on the gas environment, having a small detection area, and having uneven distribution of the sampling laser beam intensity, and cannot be applied to deep space cosmic dust detection. The Rosetta spacecraft launched by the European Space Agency in 2004 carried a "particle collision analysis and dust collector system" based on the principle of laser scattering, which can detect the size, impulse, velocity and mass flux of dust particles. The device uses four lasers to form a detection light curtain with an area of ​​100mm×100mm, and is matched with six Winston cones placed in a staggered manner to cover the entire light curtain detection area, and is connected to a photodiode to realize the collection of scattered light and light flux measurement within a limited solid angle (Adv. Space Res. 29, 1165-1169, 2002); However, the design uses multiple lasers to splice to generate a laser detection light curtain, which not only leads to poor uniformity of the intensity spatial distribution of the laser detection light curtain, which seriously affects the accuracy of the dust particle parameter measurement, but also the measurement system structure is complex, and the weight and power consumption are difficult to control; In addition, the detection light curtain in the design is too wide, resulting in a too small semi-cone angle of the Winston cone used for scattered light collection, which reduces the collection efficiency of scattered light and seriously affects the lower limit of the dust particle size measurement. The lower limit of measurement verified by ground-based tests is 60 microns. In fact, during the flyby of Comet 67P, the particle sizes of the detected particle events were all above 80 microns (Astronomy & Astrophysics, Vol. 583, Article No. A13, 2015). Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide an optical sensor for in-situ detection of deep space cosmic dust, which has the advantages of non-contact, no destruction of particle dynamic characteristics, large detection area, no additional external bias, and high detection accuracy. It can effectively improve the uniformity of the intensity of the laser detection light curtain in spatial distribution, expand the lower limit of dust particle size measurement, and realize in-situ precise measurement of low-number concentration cosmic dust in deep space environment.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] An optical sensor for in-situ detection of deep space cosmic dust, comprising a system housing 10, a semiconductor laser 1 is fixed at the bottom of the system housing 10, a Powell prism 2 is arranged above the light outlet of the semiconductor laser 1, an aperture 3 is arranged above the Powell prism 2, the aperture 3 is installed on the side of the system housing 10, a total reflection mirror 4 is arranged above the aperture 3, the total reflection mirror 4 is installed on the internal dome of the system housing 10, a spherical cylindrical lens 5 is arranged on the reflected light path of the total reflection mirror 4, the spherical cylindrical lens 5 is fixed on the internal dome of the system housing 10, the optical axis of the spherical cylindrical lens 5 is collinear with the center line of the total reflection mirror 4, and the spherical cylindrical lens 5, the total reflection mirror 4, the aperture 3, the Powell prism 2 and the semiconductor laser 1 form a laser shaping and collimation module;

[0007] A Winston cone array 6 composed of a plurality of Winston cones is installed at offset positions on the left and right sides of the detection light curtain emitted from the spherical cylindrical lens 5. The Winston cone array 6 covers a parallelogram ABCD area, which is the detection sensitive area. The entrance direction of the Winston cone is 90° with the main optical axis of the laser. The Winston cone array 6 is fixed inside the system housing 10. A bandpass filter 8 is connected to the front of each Winston cone, and a photodiode and a signal processing terminal 7 are connected to the rear of each Winston cone. The photodiode and the signal processing terminal 7 include supporting circuits. The Winston cone array 6, the photodiode and the signal processing terminal 7, and the bandpass filter 8 form a scattered light collection and photoelectric conversion module.

[0008] A laser trap 9 is arranged in front of the detection light curtain emitted from the spherical cylindrical lens 5 . The laser trap 9 is fixed inside the system housing 10 and is colinear with the total reflection mirror 4 and the spherical cylindrical lens 5 .

[0009] The laser beam output by the semiconductor laser 1 is a pre-collimated elliptical Gaussian beam, with a central wavelength of about 980 nm and a positive and negative variation of no more than 20 nm. The modulation frequency of the semiconductor laser is adjustable, and the maximum modulation frequency is greater than 50 KHz.

[0010] The optical axis of the Powell prism 2 is coaxial with the laser beam. The Powell prism 2 is a cylindrical optical lens made of glass or quartz glass, including a Powell prism internal substrate 2-2. One side of the Powell prism internal substrate 2-2 is a Powell prism aspheric surface 2-1, and the other side of the Powell prism internal substrate 2-2 opposite to the Powell prism aspheric surface 2-1 is a Powell prism plane 2-3.

[0011] The Powell prism aspheric surface 2-1 has the surface formula:

[0012]

[0013] Where c is the curvature of the curve, C k is the cone coefficient, y and Z are the horizontal and vertical coordinates of the cross section of the surface curve respectively; the curve obtained by the above surface formula is translated along the x-axis perpendicular to the cross section to obtain the curved surface of the Powell prism; the parameters of the Powell prism must meet the condition 0.25<|c·C k |<50, that is, the absolute value of the product of the curvature and the cone coefficient must be between 0.25 and 50; the surface of the Powell prism aspheric surface 2-1 and the Powell prism plane 2-3 are both covered with a dielectric anti-reflection film.

[0014] The aperture 3 is a circular hole coated with a matte material, and the center position of the aperture is colinear with the optical axis of the laser beam.

[0015] The center of the total reflection mirror 4 is colinear with the optical axis of the laser beam, and the normal of the reflection mirror forms an angle of 45° with the optical axis of the laser beam, so that the incident laser beam is deflected by 90°; the substrate of the total reflection mirror 4 is glass or quartz glass, and the surface is coated with a high-reflectivity coating suitable for 45° reflection at the laser wavelength used.

[0016] The optical axis of the spherical cylindrical lens 5 is coaxial with the optical axis of the laser after reflection by the total reflection mirror; the spherical cylindrical lens 5 is a cylindrical optical lens made of glass or quartz glass, including a spherical cylindrical mirror internal glass 5-2, one side of the spherical cylindrical mirror internal glass 5-2 is a spherical cylindrical mirror spherical surface 5-1, and the other side of the spherical cylindrical mirror internal glass 5-2 opposite to the spherical cylindrical mirror spherical surface 5-1 is a spherical cylindrical mirror plane 5-3; the surfaces of the spherical cylindrical mirror spherical surface 5-1 and the spherical cylindrical mirror plane 5-3 are both covered with a dielectric anti-reflection film.

[0017] The Winston cone contained in the Winston cone array 6 is a non-imaging concentrator made of metal, including a Winston cone surface structure 6-2, the inner surface of the Winston cone surface structure 6-2 is provided with a Winston cone metal coating 6-1, the Winston cone metal coating 6-1 is a high reflective material suitable for the laser wavelength used, and the Winston cone surface structure 6-2 is a composite rotating parabola structure, and its cross-section is divided into two parts: the upper half is a part of the parabola of the parabola symmetry axis AF and the parabola focus F, and the lower half is a mirror image of the upper half relative to the optical axis; the outlet diameter of the Winston cone formed by the upper half and the lower half is d o , the inlet diameter is d i , the length is l; the maximum receiving angle of Winston cone is θ max =sin -1 (d o / d i );Define the incident angle θ of the light entering from the entrance of the Winston cone as the angle between it and the optical axis of the Winston cone, and the incident angle θ<θ max The light will be emitted from the Winston cone exit after multiple reflections; and the incident angle θ ≥ θ max The light will return from the entrance of the Winston cone through multiple reflections; the length l of the Winston cone satisfies the formula:

[0018]

[0019] The photodiode and signal processing terminal 7 are photodiodes that are sensitive to the wavelength of the laser used and can fully cover the exit of the Winston cone. When the photodiode is installed, its photosensitive surface is tightly connected to the exit of the Winston cone, and the electrical signal converted from the light scattering signal is amplified and denoised by the circuit of the signal processing terminal before output.

[0020] The bandpass filter 8 is a coated interference filter element on a quartz substrate, which is larger than the entrance diameter of the Winston cone. Its function is to selectively filter the wavelength of light, achieve transparency to light within a certain wavelength range around its central wavelength, and prevent the entry of light outside the wavelength range.

[0021] The laser trap 9 is coaxial with the optical axis of the reflected laser. The interior of the laser trap 9 is an optical absorption material that eliminates the laser based on the absorption effect.

[0022] The system housing 10 is made of metal, with a parallelogram opening on the top that is the same size as the detection photosensitive area, and the inner surface is coated with an extinction material suitable for the laser wavelength used.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention realizes the detection of dust particles based on the interaction between dust particles and shaped laser beams, and has the characteristics of non-contact, no destruction of particle dynamic characteristics, large detection area, no additional external bias, and high detection accuracy.

[0025] 2. The present invention adopts a laser shaping method based on Powell prism and spherical cylindrical lens, which can effectively improve the uniformity of the spatial distribution of the detection laser light curtain intensity, thereby achieving the effect of greatly improving the measurement accuracy of dust particle parameters.

[0026] 3. The present invention effectively achieves coverage of a large-area detection light curtain and limits the angle of the collected scattered light by adopting a Winston cone array to collect scattered light; by designing a Winston cone with a larger receiving angle, the collection efficiency of scattered light is improved, and the lower limit of dust particle size measurement is expanded, which can realize the on-site precise measurement of low-concentration cosmic dust in deep space environment.

[0027] 4. The present invention adopts a semiconductor laser as a laser light source, selects a photodiode as a scattered light detector, and sets a total reflection mirror structure, which is beneficial to the integration and miniaturization of optical sensors.

[0028] 5. By setting an aperture of appropriate size and coating the system housing with extinction material, the influence of stray light on detection can be suppressed, the background noise of the sensor can be effectively reduced, and the lower limit of the sensor's detection of extremely small dust particles can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of a three-dimensional structure of an embodiment of the present invention.

[0030] Figure 2 FIG. 4 is a cross-sectional view of a Powell prism according to an embodiment of the present invention.

[0031] Figure 3 4 is a cross-sectional view of a spherical cylindrical lens according to an embodiment of the present invention.

[0032] Figure 4 FIG. 4 is a cross-sectional view of a single Winston cone in a Winston cone array according to an embodiment of the present invention.

[0033] Figure 5 This is an intensity distribution diagram of the laser detection light curtain in the fast axis direction according to an embodiment of the present invention.

[0034] In the figure: 1-semiconductor laser, 2-Powell prism, 3-aperture, 4-total reflection mirror, 5-spherical cylindrical lens, 6-Winston cone array, 7-photodiode and signal processing terminal, 8-bandpass filter, 9-laser trap, 10-system housing; 2-1-aspherical surface of Powell prism, 2-2-internal substrate of Powell prism, 2-3-Powell prism plane; 5-1-spherical surface of spherical cylindrical mirror, 5-2-internal glass of spherical cylindrical mirror, 5-3-plane of spherical cylindrical mirror; 6-1-Winston cone metal coating, 6-2-surface structure of Winston cone. DETAILED DESCRIPTION

[0035] The technical solution of the present invention will be described clearly and completely below 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 creative work are within the scope of protection of the present invention.

[0036] like Figure 1 As shown, an optical sensor for in-situ detection of deep space cosmic dust includes a system housing 10, a semiconductor laser 1 is fixed at the bottom of the system housing 10, and the semiconductor laser 1 is used to generate a laser beam with a nearly collimated elliptical Gaussian distribution; a Powell prism 2 is arranged above the light outlet of the semiconductor laser 1, and the Powell prism 2 is used to shape the laser beam; an aperture 3 is arranged above the Powell prism 2, and the aperture 3 is installed on the side of the system housing 10 to prevent stray light from entering the detection area; a total reflection A reflector 4, a total reflector 4 is installed on the dome inside the system housing 10, and is used to deflect the laser path by 90°; a spherical cylindrical lens 5 is arranged on the reflected light path of the total reflector 4, and the spherical cylindrical lens 5 is fixed on the dome inside the system housing 10, and the optical axis of the spherical cylindrical lens 5 is collinear with the center line of the total reflector 4. The spherical cylindrical lens 5, the total reflector 4, the aperture 3, the Powell prism 2 and the semiconductor laser 1 form a laser shaping and collimation module, which together realize that the laser in the detection sensitive area is shaped into a nearly collimated detection light curtain with uniform intensity;

[0037] A Winston cone array 6 consisting of a plurality of Winston cones is installed at offset positions on the left and right sides of the detection light curtain emitted from the spherical cylindrical lens 5. The Winston cone array 6 covers the parallelogram ABCD area, i.e., the detection sensitive area, and the entrance direction of the Winston cone is 90° with the main optical axis of the laser. The Winston cone array 6 is fixed inside the system housing 10 and is used to collect particle scattered light within a certain angle range. A bandpass filter 8 is connected to the front of each Winston cone to filter out environmental stray light other than the working laser. A photodiode and a signal processing terminal 7 are connected to the rear of each Winston cone. The photodiode and the signal processing terminal 7 include supporting circuits for converting and processing the collected light scattering signal into a photoelectric signal. The Winston cone array 6, the photodiode and the signal processing terminal 7, and the bandpass filter 8 form a scattered light collection and photoelectric conversion module.

[0038] A laser trap 9 is provided in front of the detection light curtain emitted from the spherical cylindrical lens 5. The laser trap 9 is fixed inside the system housing 10 and is colinear with the total reflection mirror 4 and the spherical cylindrical lens 5 to absorb laser light and ensure the internal optical darkroom state.

[0039] The semiconductor laser 1 is a laser light source. In the embodiment, a semiconductor laser with a central wavelength of 976nm, a line width not exceeding 10nm, a peak power of 2.0W, a duty cycle of 50%, and a modulation frequency of 50KHz is used. Its fast axis divergence angle is 10mrad, the slow axis divergence angle is 5.1mrad, and the light spot is a nearly collimated elliptical Gaussian distribution; the fast axis direction is parallel to the side wall and bottom surface of the system housing 10, and the slow axis direction is perpendicular to the side wall of the system housing 10 and parallel to the bottom surface of the system housing 10; the fast axis waist width at the laser outlet is 18.4mm, and the slow axis waist width is 2.3mm.

[0040] The aperture 3 is a small round hole coated with a matte material, the center of the aperture is colinear with the main axis of the laser beam, in the embodiment, the aperture diameter φ=8mm, the material base is aluminum, and pine soot ink is coated for matte.

[0041] The center of the total reflection mirror 4 is colinear with the optical axis of the laser beam, and the normal of the reflection mirror forms an angle of 45° with the optical axis of the laser beam, so that the incident laser beam is deflected by 90°; the substrate of the total reflection mirror 4 is glass or quartz glass, and the surface is coated with a high-reflectivity coating suitable for 45° reflection at the wavelength of the laser used; the length and width of the total reflection mirror 4 in this embodiment are 60mm and 30mm respectively, and the substrate is H-K9L glass, and the surface is coated with a high-reflection dielectric film with a central wavelength of 976nm, and the reflectivity of the laser with a central wavelength of 976nm is greater than 99.5%.

[0042] The photodiode and signal processing terminal 7 are photodiodes that are sensitive to the wavelength of the laser used. In the embodiment, a PIN photodiode is used, and the photoelectric conversion efficiency at the central wavelength of 976 nm is greater than 0.6 A / W, and the photosensitive area is 18×18 mm. 2 , which can fully cover the exit of the Winston cone; when the photodiode is installed, its photosensitive surface is closely connected to the exit of the Winston cone, and the electrical signal converted from the light scattering signal is amplified, denoised, and output by the circuit of the signal processing terminal for inverting parameters such as the particle size of dust particles.

[0043] The bandpass filter 8 is a coated interference filter element on a quartz substrate, which functions to selectively filter the wavelength of light, achieve transmittance to light in a certain wavelength range around its central wavelength, and prevent the entry of light outside the wavelength range; in the embodiment, an interference bandpass filter with a central wavelength of 980nm and a half-width of 25nm is used, and the transmittance of the central wavelength laser is greater than 90%. The size is 50mm, which is larger than the entrance diameter of the Winston cone, and can effectively reduce the influence of non-working light sources on the photodiode and the signal processing terminal 7, reduce the optical noise of the sensor, and improve the measurement accuracy of the sensor.

[0044] The laser trap 9 is coaxial with the reflected laser optical axis. The laser trap 9 is composed of an absorption glass structure. When the laser enters the trap cavity, it will be reflected and absorbed multiple times by the inner wall of the cavity. The material used in the embodiment is absorption optical glass. The internal absorption rate of the glass is greater than 99%. The surface of the absorption optical glass is coated with an anti-reflection film, so that the laser penetrates into the glass and is absorbed in large quantities, and the surface reflectivity is less than 1%.

[0045] The system housing 10 is made of aluminum, and has a parallelogram opening on the top that is the same size as the detection photosensitive area to facilitate the entry of cosmic dust particles into the laser detection area; the interior of the system housing 10 is completely coated with an extinction material suitable for the laser wavelength used. In the embodiment, pine soot ink is used for extinction to reduce the impact of stray light on the sensor.

[0046] Reference Figure 2 The optical axis of the Powell prism 2 is coaxial with the laser beam. The Powell prism 2 is a cylindrical optical lens made of glass or quartz glass, including a Powell prism internal substrate 2-2. One side of the Powell prism internal substrate 2-2 is a Powell prism aspheric surface 2-1, and the other side of the Powell prism internal substrate 2-2 opposite to the Powell prism aspheric surface 2-1 is a Powell prism plane 2-3;

[0047] The Powell prism aspheric surface 2-1 has a surface formula:

[0048]

[0049] Where c is the curvature of the curve, C k is the cone coefficient, y and Z are the horizontal and vertical coordinates of the cross section of the surface curve respectively; the curve obtained by the above surface formula is translated along the x-axis perpendicular to the cross section to obtain the curved surface of the Powell prism; the parameters of the Powell prism must meet the condition 0.25<|c·C k <|50, that is, the absolute value of the product of the curvature and the cone coefficient must be between 0.25 and 50; the curvature of the Powell prism in the embodiment is 1 / 17.4mm -1 , the cone coefficient is -4.8 (the product meets the condition requirements), the center thickness of the lens is 20mm, and the radius of its plane is 10mm; the surface of the Powell prism aspheric surface 2-1 and the Powell prism plane 2-3 are both covered with a dielectric anti-reflection film, and have a transmittance greater than 99% for the laser with a central wavelength of 976nm; in the embodiment, the internal substrate 2-2 of the Powell prism is a high-transmittance glass H-K9L.

[0050] Reference Figure 3 , the optical axis of the spherical cylindrical lens 5 is coaxial with the optical axis of the laser after reflection by the total reflection mirror; the spherical cylindrical lens 5 is a cylindrical optical lens made of glass or quartz glass, including an inner glass 5-2 of a spherical cylindrical mirror, one side of the inner glass 5-2 of the cylindrical mirror is a spherical cylindrical mirror spherical surface 5-1, and the other side of the inner glass 5-2 of the cylindrical mirror opposite to the spherical cylindrical mirror spherical surface 5-1 is a spherical cylindrical mirror plane 5-3; in the embodiment, the center thickness of the spherical cylindrical lens is 20mm, the length and width of the plane are 50mm and 20mm respectively, and the focal length is 66mm; the surfaces of the spherical cylindrical mirror spherical surface 5-1 and the spherical cylindrical mirror plane 5-3 are both covered with a dielectric anti-reflection film, which has a transmittance greater than 99% for 976nm laser; in the embodiment, the inner glass 5-2 of the spherical cylindrical mirror is a high-transmittance glass H-K9L.

[0051] Reference Figure 4 The Winston cone contained in the Winston cone array 6 is a non-imaging concentrator made of metal, including a Winston cone surface structure 6-2. The inner surface of the Winston cone surface structure 6-2 is provided with a Winston cone metal coating 6-1. The Winston cone metal coating 6-1 is a highly reflective material suitable for the laser wavelength used, and is a gold film in the embodiment; the Winston cone surface structure 6-2 is a composite rotating parabola structure, and its cross-section is divided into two parts: the upper half is a part of the parabola of the parabola symmetry axis AF and the parabola focus F, and the lower half is a mirror image of the upper half relative to the optical axis; the outlet diameter of the Winston cone formed by the upper half and the lower half is d o , the inlet diameter is d i , the length is l; the maximum receiving angle of Winston cone is θ max =sin -1 (d o / d i);Define the incident angle θ of the light entering from the entrance of the Winston cone as the angle between it and the optical axis of the Winston cone, and the incident angle θ<θ max The light will be emitted from the Winston cone exit after multiple reflections; and the incident angle θ ≥ θ max The light will return from the entrance of the Winston cone through multiple reflections; the length l of the Winston cone satisfies the formula:

[0052]

[0053] In the embodiment, the maximum receiving angle of the Winston cone is θ max =19.5°, that is, the scattering angle range of the detected scattered particles is [70.5°, 109.5°]; the outlet diameter of the Winston cone d o The inlet diameter is 14.2 mm. i The length l of the Winston cone is 42.5mm, the length l of the Winston cone is 80.3mm, the wall thickness of the Winston cone is 1mm, and it is processed with a nickel metal substrate.

[0054] The spherical cylindrical lens 5 and the Powell prism 2 shape the nearly collimated elliptical Gaussian distribution light beam (fast axis waist width is 18.4mm, slow axis waist width is 2.3mm) emitted by the semiconductor laser 1 into a collimated light curtain with a width of 40mm in the fast axis direction and a thickness of 3mm in the slow axis direction, which is used as a sensor laser detection light curtain. Figure 5 This is the intensity distribution diagram of the laser detection light curtain in the fast axis direction. It can be seen that in the detection area, the laser spot distribution after shaping is relatively uniform and has obvious truncation.

[0055] The uniformity γ of the light curtain is defined as:

[0056]

[0057] Where E i is the light intensity value at each point in the light curtain, is the average light intensity value obtained from the statistics of each point on the light curtain, and N is the total number of light intensity measurement points in the light curtain; Figure 5 The uniformity of the laser detection light curtain in the width direction is 91.6%, which is greater than 90%; the intensity distribution in the slow axis direction remains unchanged and is still a nearly collimated Gaussian distribution.

[0058] The integration and miniaturization of the optical sensor are achieved by using a semiconductor laser 1 as a laser light source, using a photodiode and a signal processing terminal 7 as detectors of scattered light, and by providing a total reflection mirror 4.

[0059] The working principle of the present invention is: Figure 1The laser driving power source drives the semiconductor laser light source 1 to generate a modulated laser of a certain frequency. The laser beam is shaped by the optical system (Powell prism 2, aperture 3, total reflection mirror 4, spherical cylindrical lens 5) to form a collimated, large-area, uniformly distributed photosensitive detection area in the detection area; dust particles can enter the photosensitive detection area through the parallelogram opening just above the system housing 10. When the particles pass through the photosensitive detection area, they are illuminated by the incident laser light curtain and generate scattered light. The scattered light of some particles is filtered out by the bandpass filter 8 after the stray light other than the working wavelength is filtered out, and then collected and converged by the Winston cone array 6; the Winston cone not only plays the role of collection and convergence, but also has the key role of limiting the angle range of scattered light collection. Only when the incident angle is less than the maximum receiving angle of the Winston cone The light can be emitted from the exit of the Winston cone through multiple reflections, and the light with an incident angle greater than the maximum receiving angle of the Winston cone will return from the entrance of the Winston cone through multiple reflections; the particle scattered light emitted from the exit of the Winston cone is converted into an electrical signal of corresponding intensity by the photodiode and the signal processing terminal 7. Since the electrical signal intensity is proportional to the collected particle light scattering information, and the particle scattered light signal is proportional to the particle size, the electrical signal intensity finally obtained by the sensor can invert the particle size information of the dust particles; the laser beam is absorbed by the laser trap 9 at the end of the sensor, and the stray light inside the sensor is absorbed by the system housing 10 coated with pine soot ink, which suppresses the influence of stray light on the detection system, effectively reduces the background noise of the sensor, and improves the sensor's ability to detect extremely small dust particles.

[0060] The above-mentioned embodiment only expresses a preferred implementation mode of the present invention, and its description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the attached claims.

Claims

1. An optical sensor for in-situ detection of deep space cosmic dust, comprising a system housing (10), characterized in that: A semiconductor laser (1) is fixed at the bottom of a system housing (10); a Powell prism (2) is arranged above the light outlet of the semiconductor laser (1); an aperture (3) is arranged above the Powell prism (2); the aperture (3) is mounted on the side of the system housing (10); a total reflection mirror (4) is arranged above the aperture (3); the total reflection mirror (4) is mounted on the internal dome of the system housing (10); a spherical cylindrical lens (5) is arranged on the optical path of the reflected light of the total reflection mirror (4); the spherical cylindrical lens (5) is fixed on the internal dome of the system housing (10); the optical axis of the spherical cylindrical lens (5) is colinear with the center line of the total reflection mirror (4); the spherical cylindrical lens (5), the total reflection mirror (4), the aperture (3), the Powell prism (2) and the semiconductor laser (1) form a laser shaping and collimation module; A Winston cone array (6) consisting of a plurality of Winston cones is staggeredly installed on the left and right sides of the detection light curtain emitted from the spherical cylindrical lens (5), the Winston cone array (6) covers a parallelogram ABCD area, which is the detection sensitive area, and the entrance direction of the Winston cone is 90 degrees with the main optical axis of the laser; the Winston cone array (6) is fixed inside the system housing (10); a bandpass filter (8) is connected to the front of each Winston cone, and a photodiode and a signal processing terminal (7) is connected to the rear of each Winston cone, and the photodiode and the signal processing terminal (7) include a matching circuit; the Winston cone array (6), the photodiode and the signal processing terminal (7), and the bandpass filter (8) form a scattered light collection and photoelectric conversion module; A laser trap (9) is arranged in front of the detection light curtain emitted from the spherical cylindrical lens (5); the laser trap (9) is fixed inside the system housing (10) and is colinear with the total reflection mirror (4) and the spherical cylindrical lens (5).

2. The optical sensor according to claim 1, characterized in that: The semiconductor laser (1) outputs a laser beam which is a pre-collimated elliptical Gaussian beam, with a central wavelength of 980 nm and a positive and negative variation of no more than 20 nm. The modulation frequency of the semiconductor laser (1) is adjustable, and the maximum modulation frequency is greater than 50 kHz.

3. The optical sensor according to claim 1, characterized in that: The optical axis of the Powell prism (2) is coaxial with the laser beam. The Powell prism (2) is a cylindrical optical lens made of glass or quartz glass, and comprises a Powell prism internal substrate (2-2). One side of the Powell prism internal substrate (2-2) is a Powell prism aspheric surface (2-1), and the other side of the Powell prism internal substrate (2-2) opposite to the Powell prism aspheric surface (2-1) is a Powell prism plane (2-3). The aspheric surface of Powell prism (2-1) has the surface formula: Where c is the curvature of the curve, C k is the cone coefficient, y and Z are the horizontal and vertical coordinates of the cross section of the surface curve respectively; the curve obtained by the above surface formula is translated along the x-axis perpendicular to the cross section to obtain the curved surface of the Powell prism; the parameters of the Powell prism must meet the condition 0.25<|c·C k |<50, that is, the absolute value of the product of the curvature and the cone coefficient must be between 0.25 and 50; the surface of the Powell prism aspheric surface (2-1) and the surface of the Powell prism plane (2-3) are both covered with a dielectric anti-reflection film.

4. The optical sensor according to claim 1, characterized in that: The center of the total reflection mirror (4) is colinear with the optical axis of the laser beam, and the normal line of the reflection mirror forms an angle of 45° with the optical axis of the laser beam, so that the incident laser beam is deflected by 90°; the substrate of the total reflection mirror (4) is glass or quartz glass, and the surface is coated with a high reflectivity coating suitable for 45° reflection at the wavelength of the laser used.

5. The optical sensor according to claim 1, characterized in that: The optical axis of the spherical cylindrical lens (5) is coaxial with the optical axis of the laser after being reflected by the total reflection mirror; the spherical cylindrical lens (5) is a cylindrical optical lens made of glass or quartz glass, comprising a spherical cylindrical mirror inner glass (5-2); one side of the spherical cylindrical mirror inner glass (5-2) is a spherical cylindrical mirror spherical surface (5-1), and the other side of the spherical cylindrical mirror inner glass (5-2) opposite to the spherical cylindrical mirror spherical surface (5-1) is a spherical cylindrical mirror plane (5-3); the surfaces of the spherical cylindrical mirror spherical surface (5-1) and the spherical cylindrical mirror plane (5-3) are both covered with a dielectric anti-reflection film.

6. The optical sensor according to claim 1, characterized in that: The Winston cone contained in the Winston cone array (6) is a non-imaging concentrator made of metal, including a Winston cone surface structure (6-2), the inner surface of the Winston cone surface structure (6-2) is provided with a Winston cone metal coating (6-1), the Winston cone metal coating (6-1) is a high-reflectivity material suitable for the laser wavelength used, and the Winston cone surface structure (6-2) is a composite rotating parabola structure, the cross section of which is divided into two parts: the upper half is a part of the parabola of the parabola symmetry axis AF and the parabola focus F, and the lower half is a mirror image of the upper half relative to the optical axis; the outlet diameter of the Winston cone formed by the upper half and the lower half is d o , the inlet diameter is d i , the length is l; the maximum receiving angle of Winston cone is θ max =sin -1 (d o / d i );Define the incident angle θ of the light entering from the entrance of the Winston cone as the angle between it and the optical axis of the Winston cone, and the incident angle θ<θ max The light will be emitted from the Winston cone exit after multiple reflections; and the incident angle θ ≥ θ max The light will return from the entrance of the Winston cone through multiple reflections; the length l of the Winston cone satisfies the formula:

7. The optical sensor according to claim 1, characterized in that: The photodiode and signal processing terminal (7) are photodiodes that are sensitive to the wavelength of the laser used and can fully cover the outlet of the Winston cone. When the photodiode is installed, its photosensitive surface is closely connected to the outlet of the Winston cone, and the electrical signal converted from the light scattering signal is amplified and de-noised by the circuit of the signal processing terminal before being output.

8. The optical sensor according to claim 1, characterized in that: The bandpass filter (8) is a coated interference filter element on a quartz substrate, which is larger than the entrance diameter of the Winston cone and functions to selectively filter the wavelength of light, thereby achieving transparency for light within a certain wavelength range around its central wavelength and preventing light outside the wavelength range from entering.

9. The optical sensor according to claim 1, characterized in that: The laser trap (9) is coaxial with the optical axis of the reflected laser; the interior of the laser trap (9) is an optical absorption material, which eliminates the laser based on the absorption effect.

10. The optical sensor according to claim 1, characterized in that: The system housing (10) is made of metal, has a parallelogram opening on the top that is the same size as the detection photosensitive area, and the inner surface is coated with an extinction material suitable for the wavelength of the laser used.

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