MICRO-THRUST AND MICRO-IMPULSE APPLICATION DEVICE AND METHOD BASED ON LIGHT PRESSURE PRINCIPLE

Abstract

A micro-thrust and micro-impulse application device and method generates micro-thrust to a target by light pressure action from laser reflection. The device comprises a laser, a laser adjustment device, a beam splitter, a shutter, a reflector, and a laser power meter. Laser beam is generated by laser, adjusted by laser adjustment device, and divided into two paths by beam splitter. Laser in one path is measured at laser power meter; power measured determines magnitude for micro-thrust. In another path, it irradiates on the reflector on the target via shutter for generating micro-thrust. Light reflected by the reflector arrives at another laser power meter. Power of two laser paths are measured in real time by two laser power meters, acting micro-thrust is calculated by combining parameters including reflectivity and incident angle of laser irradiating the reflector, and light output power of the laser is adjusted in real time.

Claims

1. A micro-thrust and micro-impulse application device based on a light pressure principle, comprising: a laser configured to generate a laser beam; a beam splitter arranged on a light path of the laser, wherein the beam splitter comprises an included angle with the laser beam generated by the laser and divides the laser beam into two beams by transmission and reflection; a shutter arranged on a light path of the laser beam reflected by the beam splitter, wherein the shutter is configured to control on/off of the laser beam directed to a target; a reflector fixed on a surface of the target, wherein the reflector comprises an included angle with the laser beam reflected by the beam splitter; and a laser power meter, wherein the laser power meter further comprises a first laser power meter arranged on a light path of the laser beam transmitted through the beam splitter and configured to measure light output power of the laser in real time; and a second laser power meter arranged on a light path of the laser beam reflected by the reflector and configured to measure laser power reflected by the reflector.

2. The device of claim 1, further comprising a beam adjustment device arranged between the laser and the beam splitter, wherein the beam adjustment device is configured to adjust the laser beam emitted by the laser into parallel light or to adjust beam spatiotemporal distribution characteristics of the laser beam, or both, such that the laser beam is incident on the beam splitter.

3. The device of claim 2, wherein the beam spatiotemporal distribution characteristics comprises the polarization state and the phase of the laser.

4. The device of claim 2, wherein the beam adjustment device is configured to adjust a polarization state and a phase of the laser such that the laser beam is incident on the beam splitter.

5. The device of claim 1, wherein the output power of the laser is adjustable.

6. The device of claim 1, wherein the target is placed in a vacuum environment.

7. The device of claim 1, wherein the target is placed in a gas environment, and the gas environment effects little gas disturbance.

8. A method for applying a micro-thrust and a micro-impulse by the device according to claim 1, comprising: using the laser to enter the beam splitter at a set angle, respectively measuring power of reflected light and transmitted light passing through the beam splitter, and calculating reflectance and transmittance ratio of the beam splitter; preliminarily calculating the light output power of the laser and setting the laser according to magnitude of a required micro-thrust applied to the target, and setting an opening time and a closing time of the shutter according to a magnitude of the required micro-impulse; turning on the laser, calculating a laser beam power reflected by the beam splitter for applying the micro-thrust to the target by means of multiplying the reflectance and transmittance ratio of the beam splitter by the laser beam power measured from the first laser power meter; opening the shutter according to the set shutter opening time so that the laser beam is incident on the reflector and reflected; calculating the magnitude of the micro-thrust applied to the target in real time by measuring the power of the laser beam reflected by the reflector by the second laser power meter and according to the power measured by the first laser power meter and the second laser power meter, and judging whether the requirements are met, and if not, adjusting the light output power of the laser in real time; and after the set shutter closing time is reached, closing the shutter and turning off the laser.

9. The method of claim 8, wherein the magnitude of the micro-thrust applied to the target is
F(t)=√{square root over (F.sub.y.sup.2(t)+F.sub.x.sup.2(t))}, wherein F.sub.y(t)=F(t)cos α is the magnitude of a resolved component of a vector of the micro-thrust in a plane formed by the incident laser light and the reflected light in a direction perpendicular to a reflector surface and pointing towards the reflector: $F_y\left(t\right)=\frac{\left(k.Math.P_1\left(t\right)+P_2\left(t\right)\right).Math.\cos \theta }{c};$ and F.sub.x(t)=F(t)sin α is the magnitude of a resolved component of a vector of the micro-thrust in the plane formed by the laser incident light and the reflected light in a direction parallel to the reflector surface: $F_x\left(t\right)=\frac{\left(k.Math.P_1\left(t\right)-P_2\left(t\right)\right).Math.\sin \theta }{c},$ wherein k is the reflectance and transmittance ratio of the beam splitter; c is the speed of light in vacuum; θ is the incident angle of the laser beam at the reflector; a is the included angle between the direction of the micro-thrust and the normal of the reflector surface; P.sub.1(t) is the power of the laser beam transmitted through the beam splitter; and P.sub.2(t) is the power of the laser beam reflected by the reflector.

10. The method of claim 8, wherein the opening time t.sub.0 and the closing time t.sub.1 of the shutter satisfy:
I=∫.sub.t.sub.0.sup.t.sup.1F(t)dt, wherein I is the magnitude of the micro-impulse required, and the application position and direction of the micro-impulse are consistent with the application position and direction of the micro-thrust.

11. The method of claim 8, further comprising calculating the micro-thrust and the micro-impulse applied to the target according to the power measured by the first laser power meter and the second laser power meter, and the opening and closing time of the shutter, and applying the micro-thrust and the micro-impulse to a micro-thrust and micro-impulse measuring device and measuring its response so as to calibrate the micro-thrust and micro-impulse measuring device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Drawings are provided to clarify advantages and features of embodiments of the present invention; they should not be considered as limiting the scope of invention.

[0028] FIG. 1 shows the structure of the micro-thrust and micro-impulse application device based on the light pressure principle according to an embodiment of the present invention.

[0029] FIG. 2 shows the schematic diagram of the micro-thrust application based on the light pressure principle according to an embodiment of the present invention.

[0030] FIG. 3 is a flow chart showing the micro-thrust and micro-impulse application method based on the light pressure principle according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0031] The present invention is described in detail in the following embodiments in connection with the drawings. One of skilled in the art may modify the embodiments of the present invention as described herein without departing from the scope of protection of the invention.

[0032] The present invention provides a micro-thrust and micro-impulse application device and method based on a light pressure principle. The device and method control the magnitude of the micro-thrust applied to the target in real time by adjusting the light output power of the laser and control the magnitude of the micro-impulse applied to the target by the laser light pressure by means of controlling the light output time of the laser. Specific embodiments of the present invention is further described with reference to the drawings.

[0033] As shown in FIG. 1, a micro-thrust and micro-impulse application device based on a light pressure principle, which is a non-contact device, applies a micro-thrust to a target 001 by using a laser, where the target 001 can be placed in a vacuum environment, or a gas environment with a smaller influence from gas disturbance, so as to reduce the influence of an atmospheric disturbance thereon, so that the generated light pressure effect is more significant. The device of the present invention comprises:

[0034] a laser 101 configured for generating a laser beam; in an embodiment of the present invention, the output power of the laser is adjustable; the magnitude of a micro-thrust applied to the target 001 can be controlled by adjusting the light output power of the laser 101; and according to different selected laser powers, the device may not only provide a micro-thrust of less than the order of 10.sup.−21 N, but also achieve a micro-thrust of the order of 10 m N;

[0035] a beam splitter 102 which is arranged on a laser output light path of the laser 101, has an included angle with the laser beam generated by the laser 101, and divides the laser beam into two beams by reflection and transmission, wherein the reflection and transmission ratio of the beam splitter can be changed by adjusting the included angle; in an embodiment of the present invention, a beam adjustment device 107 is further arranged between the laser 101 and the beam splitter 102, wherein the beam adjustment device 107 is used for, after adjusting the laser beam emitted by the laser 101 into parallel light, being incident on the beam splitter 102; the beam adjustment device 107 can also be used for adjusting beam spatiotemporal distribution characteristics of the laser beam, including a polarization state and a phase of the laser, as needed;

[0036] a shutter 103 arranged on a light path of the laser beam reflected by the beam splitter 102 for controlling the on-off of the laser beam directed to the target 001; by controlling the opening and closing time of the shutter 103, the time when the laser passes through the shutter can be accurately controlled, and then the time when the micro-thrust is applied to the target 001 is controlled, so as to control the magnitude of the micro-impulse applied to the target 001; in an embodiment of the invention, the on-off time of the shutter is controllable to the order of microseconds, so that the device can apply micro-impulses down to the order of 10.sup.−28 Ns and up to the order of 100 Ns;

[0037] a reflector 104 fixed on the surface of the target 001; as shown in FIG. 2, the reflector 104 has an included angle with the laser beam reflected by the beam splitter 102, and the laser beam reflected by the beam splitter 102 is specularly reflected at the reflector 104 at a certain angle θ; in an embodiment of the invention, the reflectivity of the reflector 104 for the laser wavelength is higher than 99.9%, so that the thermal effect on the target 001 is negligible; and

[0038] a laser power meter including a first laser power meter 105 and a second laser power meter 106, wherein the first laser power meter 105 is arranged on a light path of a laser beam transmitted through the beam splitter 102, the laser beam transmitted through the beam splitter 102 irradiates on an optical power detection area of the first laser power meter 105, and the real-time power of the laser 101 can be measured by using the reflectance and transmittance ratio of the beam splitter; the second laser power meter 106 is arranged on a light path of a laser beam reflected by the reflector 104, the laser beam reflected by the reflector 104 irradiates on the optical power detection area of the second laser power meter 106, and the laser power reflected by the reflector 104 can be measured; in order to reduce the influence of the light reflected on the second laser power meter 106 re-irradiating on the target to generate an additional light pressure thrust, the distance between the second laser power meter 106, the target 001 and the reflector 104 should be kept far; when the space is limited, the influence can be reduced by adjusting the orientation of the second laser power meter 106 so that there is an included angle between the second laser power meter 106 and the reflected light of the reflector, or adding a reflector between the reflector 104 and the second laser power meter 106 so as to increase the light path distance, etc.; in an embodiment of the present invention, the beam is diffusely reflected at the second laser power meter 106, and the distance should not be less than 40 cm when the projection area of the thrust-applied object on a plane perpendicular to the direction of the reflected beam of the reflector 104 is 10 cm.sup.2. At this time, the laser power irradiated on the target 001 and the reflector 104 after the diffuse reflection at the second laser power meter is less than 0.1% of the total diffuse reflection optical power, and the light pressure thrust effect generated by this part of light is negligible.

[0039] As shown in FIG. 3, the method for applying a micro-thrust and micro-impulse by the device of the present invention comprises:

[0040] Step 301, calculating a reflection and transmittance ratio, calculating a reflection and transmittance ratio k of the reflector under the device setting conditions before the thrust is applied, and by means of the reflection and transmittance ratio, obtaining a reflected light power by multiplying the ratio by a reading of the first laser power meter when using the reflected light to generate a light pressure effect on the target; the reflection and transmittance ratio k is calculated by the method including: using a laser to obliquely enter a beam splitter at a certain incident angle, respectively measuring a power of reflected light and transmitted light passing through the beam splitter by using a high-precision power meter, and calculating and obtaining the reflectance and transmittance ratio k of the beam splitter corresponding to the incident angle;

[0041] Step 302, setting a laser and a shutter, preliminarily calculating a laser power level emitted by the laser according to the required applied micro-thrust, setting a light output power of the laser according to the calculated power, and then setting the opening time and the closing time of the shutter according to the magnitude of the required micro-impulse; the magnitude of the micro-thrust is

F(t)=√{square root over (F.sub.y.sup.2(t)+F.sub.x.sup.2(t))},

[0042] wherein F.sub.y(t)=F(t)cos α is the magnitude of a resolved component of a vector of the micro-thrust in a plane formed by the incident laser light and the reflected light in a direction perpendicular to the reflector surface and pointing towards the reflector, satisfying:

[00003]$F_y\left(t\right)=\frac{\left(k.Math.P_1\left(t\right)+P_2\left(t\right)\right).Math.\cos \theta }{c};$

and

[0043] F.sub.x(t)=F(t)sin α is the magnitude of a resolved component of a vector of the micro-thrust in the plane formed by the laser incident light and the reflected light in a direction parallel to the reflector surface, satisfying:

[00004]$F_x\left(t\right)=\frac{\left(k.Math.P_1\left(t\right)-P_2\left(t\right)\right).Math.\sin \theta }{c},$

[0044] k is the reflectance and transmittance ratio of the beam splitter; c is the speed of light in vacuum; θ is the incident angle of the laser beam at the reflector; a is the included angle between the direction of the micro-thrust and the normal of the reflector surface; P.sub.1(t) is the power of the laser beam transmitted through the beam splitter; and P.sub.2(t) is the power of the laser beam reflected by the reflector. Thus, in combination with the reflectivity of the reflector, the required light output power and the included angle of the laser can be derived.

[0045] In one embodiment of the present invention, the reflector installed on the target has a high reflectivity of more than 99.9%, so that the absorption of the laser beam by the reflector surface is small, the reflected optical power P.sub.2(t) being approximately equal to the incident light power kP.sub.1(t). At this time, the thrust

[00005]$F_x\left(t\right)=\frac{\left(k.Math.P_1\left(t\right)-P_2\left(t\right)\right).Math.\sin \theta }{c}$

of the light pressure in the direction parallel to the reflector surface is small and negligible. It is approximately considered that the thrust applied on the reflector surface is perpendicular to the reflector surface and points towards the target, and the magnitude thereof can be calculated according to F(t)=F.sub.y(t), wherein F.sub.y(t) refers to the magnitude of the component in the direction perpendicular to the reflector surface and pointing towards the reflector surface, and then the light output power of the laser is calculated according to the following formula:

[00006]$F\left(t\right)=\frac{\left(k.Math.P_1\left(t\right)+P_2\left(t\right)\right).Math.\cos \theta }{c},$

[0046] k is the reflectance and transmittance ratio of the beam splitter; c is the speed of light in vacuum; θ is the incident angle of the laser beam at the reflector; P.sub.1(t) is the power of the laser beam transmitted through the beam splitter; and P.sub.2(t) is the power of the laser beam reflected by the reflector; since the reflectivity of the reflector is relatively high, it can be considered that P.sub.2(t)=kP.sub.1(t), and then the light output power P(t) of the laser is preliminarily calculated as:

[00007]$P\left(t\right)=\left(1+k\right)\frac{\mathrm{cF}\left(t\right)}{2k\cos \theta },$

[0047] the opening time t.sub.0 and the closing time t.sub.1 of the shutter satisfy the following formula:

I=∫.sub.t.sub.0.sup.t.sup.1F(t)dt,

[0048] wherein I is the magnitude of the required micro-impulse, and the application position and direction of the micro-impulse are consistent with the application position and direction of the micro-thrust;

[0049] Step 303, turning on the laser, after turning on the laser, emitting the laser beam in parallel after the same passing through the beam adjustment device, and obliquely incidenting the laser beam on a beam splitter at a certain angle of incidence; dividing the laser into two beams by the beam splitter, wherein one beam reflected by the beam splitter is incident on a shutter, one beam transmitted through the beam splitter irradiates an optical power detection area of a first laser power meter, and a laser beam power k P.sub.1(t) for applying a micro-thrust can be obtained according to the real-time power P.sub.1(t) measured by the first laser power meter and the reflectance and transmittance ratio k of the beam splitter;

[0050] Step 304, opening the shutter: opening the shutter according to the opening time t.sub.0 set in the step 302, so that the laser beam for applying the micro-thrust is incident on the reflector fixed on the target and is partially reflected, and in the process of being incident and reflected, the laser photon generates the micro-thrust action on the target, so as to realize the application of light pressure on the target; measuring, by the second laser power meter, the power P.sub.2(t) of the laser beam reflected via the reflector, and calculating in real time the magnitude of the micro-thrust applied to the target:

[00008]$F\left(t\right)=\sqrt{F_y^2\left(t\right)+F_x^2\left(t\right)},\mathrm{where},F_y\left(t\right)=\frac{\left(k.Math.P_1\left(t\right)+P_2\left(t\right)\right).Math.\cos \theta }{c};\mathrm{and}{F}_x\left(t\right)=\frac{\left(k.Math.P_1\left(t\right)-P_2\left(t\right)\right).Math.\sin \theta }{c},$

[0051] judging whether the requirements are met, and if not, adjusting the light output power of the laser in real time; and

[0052] Step 305, turning off the device, after the closing time t.sub.1 calculated from the shutter closing time set in the step 302 is reached, closing the shutter to block the laser beam, so that the micro-thrust application process ends, and then the laser is turned off.

[0053] In the process of applying the micro-thrust, a laser irradiates a reflector arranged on the target according to the light pressure action principle. In one embodiment of the present invention, the direction of the thrust applied to the target is perpendicular to the surface of the reflector and points towards the target. In the process of applying the micro-thrust, the magnitude of the applied micro-thrust and micro-impulse is calculated by real-time power measurement. On one hand, the optical power of the laser can be adjusted in real time according to needs. On the other hand, the data of the applied thrust and micro-impulse is recorded, and the response of the target under the action of the micro-thrust and micro-impulse is recorded, which can be used for the calibration of the micro-thrust and micro-impulse measuring device.

[0054] In the present invention, the micro-thrust and micro-impulse application device and method based on a light pressure principle generates a micro-thrust to a target by the light pressure action from laser reflection. The device comprises a laser, a laser adjustment device, a beam splitter, a shutter, a reflector, and a laser power meter. A laser beam is generated by the laser, a laser characteristic is adjusted by the laser adjustment device, and then the laser beam is divided into two paths via the beam splitter. In one path, it arrives at a position of the laser power meter, and a measured power is used for determining the magnitude of laser power used for applying a micro-thrust. In the other path, it irradiates on the reflector installed on a target via the shutter, thereby generating a micro-thrust on the target. The light reflected by the reflector arrives at the other laser power meter. The powers of the two paths of lasers are measured in real time by using the two laser power meters, the micro-thrust acting on the target can be calculated by combining parameters such as a reflectivity and an incident angle of the laser irradiating the reflector, and then the light output power of the laser can be adjusted in real time according to the calculated micro-thrust to meet the requirements. It can be used to calibrate a high-precision micro-thrust and micro-impulse measuring device by recording the micro-thrust and micro-impulse data applied to the target and recording the response of the target under its action.