CN112230427B - System and method for reducing influence of undesired orders of optical diffraction device - Google Patents
System and method for reducing influence of undesired orders of optical diffraction device Download PDFInfo
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Abstract
The invention discloses a system and a method for reducing the influence of an unwanted order of an optical diffraction device, which belong to the field of optics and comprise the following steps: the optical diffraction device, the light beam focusing device and the aberration optical device are arranged along the optical path direction in sequence, and the aberration optical device is arranged between the image space focal planes of the optical generator and the light beam focusing device; the system adds a first optical aberration in the optical path through an aberration optical device, so that the quality of the light beam in the optical path is degraded; in the process of adopting the optical diffraction device to perform wavefront modulation on the incident beam, the second optical aberration which is mutually compensated with the first optical aberration is introduced into the light beam of the required order, so that the light field distribution of the required order is kept in a clear state, and the light field distribution of the non-required order is degraded by the increased first aberration, thereby effectively reducing the influence of the non-required order.
Description
Technical Field
The invention belongs to the field of optics, and particularly relates to a system and a method for reducing the influence of unwanted orders of an optical diffraction device.
Background
Optical diffraction devices are used in a wide variety of optical applications, such as laser processing, biological microscopy imaging, optical storage of information, and the like. Commonly used optical diffraction devices include gratings, acousto-optic deflectors, Spatial Light Modulators (SLMs), digital micro-mirror devices (DMDs), metamaterials, and Diffractive Optical Elements (DOEs), among others. The diffractive optical element can modulate optical parameters (phase and amplitude) of the wavefront of an incident light beam to change corresponding optical parameters of the wavefront of an outgoing light beam. Meanwhile, the size and spatial distribution of the modulation amount of the diffractive optical element can be designed in advance, so that the required optical field distribution is obtained.
Because of the flexible modulation of the wavefront, the optical diffraction device can perform a variety of functions in the optical system, such as beam splitting, deflection, scanning, focusing, aberration correction, beam shaping, and the like. Splitting, i.e. splitting one incident beam into multiple emergent beams; deflection is that the angle of the emergent light is deflected compared with the incident light; scanning, namely continuously changing the deflection angle of emergent light, so as to realize the scanning of light beams; focusing, namely focusing the emergent light through an optical diffraction device; the aberration correction means that the wavefront of the incident light is modulated to mutually offset the aberration in the optical system, so as to achieve the purpose of eliminating the aberration; beam shaping refers to shaping a beam into a desired special beam, such as a bessel beam, a laguerre-gaussian beam, a rayleigh beam, etc. Just because the optical diffraction device can realize rich functions, it is widely used in the optical field.
The optical diffraction device realizes the wave front modulation of the light beam by utilizing the diffraction of the light, however, the modulation realized by the actual optical device in the actual application can not be completely consistent with the required modulation, so that the modulation efficiency can not reach 100%, and the consumed energy can be dispersed to other diffraction orders. These diffraction orders due to non-ideal optical elements are often unwanted in practical applications, i.e. unwanted orders. These undesirable orders will have some adverse effects in applications such as in laser scanning, where these orders will create additional optical foci and in some additional areas optical focus scanning; when the laser is focused, in addition to producing a focal point at the designed location, additional focal points will be produced at other axial locations.
In practical use of the optical diffraction device, in order to eliminate the adverse effect of the unwanted orders, the light beam exiting the optical diffraction device is focused by a lens, and a Spatial Filter (SF) is placed at the focal plane to block the unwanted diffraction orders. When the SF is placed in the fourier plane, i.e. the focal plane of the focusing lens, the blocked light will not be transmitted. By designing the SF, only the desired diffraction order can be passed through, thereby eliminating the effect of the undesired order. However, when the desired order generated by the optical diffraction device coincides with the optical field distribution of the generated undesired order, the method of blocking the undesired order by SF will not be able to separate the desired order from the undesired order. In addition, when the optical field distribution generated by the optical diffraction device is changed, and the range through which the optical field distribution of the desired order passes overlaps with the undesired order, the method of blocking the undesired order using SF also fails.
Disclosure of Invention
In view of the above drawbacks or needs for improvement in the prior art, the present invention provides a system and a method for reducing the influence of an undesired order of an optical diffraction device, which aims to solve the technical problem in the prior art that when the optical field distribution of the desired order generated by the optical diffraction device coincides with the optical field distribution of the undesired order, the influence of the undesired order cannot be effectively reduced.
To achieve the above object, in a first aspect, the present invention provides a system for attenuating the effect of unwanted orders of an optical diffraction device, comprising: the optical diffraction device, the light beam focusing device and the aberration optical device are arranged along the optical path direction in sequence, and the aberration optical device is arranged between the image space focal planes of the optical generator and the light beam focusing device;
the light generator is used for providing a light source;
the aberration optical device is used for adding a first optical aberration in the optical path to cause the quality of the light beam in the optical path to be degraded;
the optical diffraction device is used for carrying out wavefront modulation on the incident beam to obtain emergent light; the wavefront modulation comprises a first wavefront modulation and a second wavefront modulation; the modulation distribution and the modulation amount corresponding to the first wavefront modulation are determined based on the function to be realized of the optical diffraction device; the second wavefront modulation is used to introduce a second optical aberration for the beam of the desired order; the second optical aberration and the first optical aberration compensate each other to achieve the effect of aberration correction;
the light beam focusing device is used for focusing emergent light to obtain light field distribution with reduced light power density of an undesired level.
Further preferably, the optical diffraction device includes: a grating, an acousto-optic deflector, an electro-optic deflector, a metamaterial material, a diffractive optical element, a digital micro-mirror device, or a spatial light modulator.
Further preferably, the functions to be realized by the above optical diffraction device include: beam splitting, beam deflection, beam scanning, beam focusing, aberration correction, or beam shaping is achieved.
Further preferably, the aberration optics is a cylindrical lens, a deformable mirror or a lens;
when the aberration optical device is a lens, the aberration optical device is placed offset from the optical axis, so that the light beam is incident on the edge of the lens, and astigmatism and coma are introduced.
Further preferably, the beam focusing device is an objective lens, a field lens or a spherical mirror.
Further preferably, the method for wavefront modulation of the optical beam by the optical diffraction device includes: modulating the amplitude of the incident light individually, modulating the phase of the incident light individually, or modulating both the amplitude and the phase of the incident light simultaneously.
Further preferably, the system for reducing the influence of the undesired orders of the optical diffraction device further comprises: a relay lens group with a spatial filter; the relay lens group is arranged between the optical diffraction device and the light beam focusing device, and the spatial filter is arranged between a front lens and a rear lens of the relay lens group and used for blocking zero-order light beams; the front lens is a lens which is in the relay lens group and the light beam reaches firstly along the light path direction; the rear lens is a lens which is in the relay lens group and the light beam finally reaches along the light path direction.
In a second aspect, the present invention provides a method for attenuating the effects of unwanted orders in an optical diffraction device, comprising the steps of:
s1, adding a first optical aberration in the optical path of the optical diffraction device to degrade the quality of the light beam;
s2, performing wavefront modulation on the light beam based on the optical diffraction device to obtain emergent light; the wavefront modulation comprises a first wavefront modulation and a second wavefront modulation; the modulation distribution and the modulation amount corresponding to the first wavefront modulation are determined based on the function to be realized of the optical diffraction device; the second wavefront modulation is used to introduce a second optical aberration for the beam of the desired order; the second optical aberration and the first optical aberration compensate each other to achieve the effect of aberration correction;
and S3, focusing the emergent light to obtain the light field distribution with the decreased optical power density of the unwanted order.
Further preferably, the method of adding the first optical aberration in the optical path includes: generating astigmatism by using a cylindrical lens; alternatively, aberrations are introduced based on irregular reflective surfaces of the deformable mirror; alternatively, the beam is made incident on the edge of the lens, introducing astigmatism and coma.
Further preferably, the method of wavefront modulation of an optical beam comprises: modulating the amplitude of the incident light individually, modulating the phase of the incident light individually, or modulating both the amplitude and the phase of the incident light simultaneously.
In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:
1. the invention provides a system and a method for reducing the influence of an unwanted order of an optical diffraction device, which lead the quality of light beams in an optical path to be degraded by adding a first optical aberration in the optical path, and lead a second optical aberration which is mutually compensated with the first optical aberration to the light beams of the wanted order in the process of carrying out wavefront modulation on incident light beams by the optical diffraction device, lead the light field distribution of the wanted order to keep a clear state, and lead the light field distribution of the unwanted order to be degraded by the added first optical aberration; since the optical power density of the undesired orders is reduced due to the existence of the first aberration, the adverse effect on the actual use of the optical diffraction device is reduced or even eliminated, and the optical power density of the desired orders is not reduced due to the second aberration, so that the desired function is still achieved. Therefore, even when the light field distribution of the required order is overlapped with the light field distribution of the non-required order, the system and the method provided by the invention can effectively reduce the influence of the non-required order.
2. When the function of the optical diffraction device is to split the light beam, the system and the method for reducing the influence of the unwanted orders of the optical diffraction device can improve the splitting number of the split beam. Because the split beam cannot be distributed in the region of the undesired order distribution when the undesired order has an effect. Therefore, when the space between the split beams is fixed, the distribution of the split beams is not influenced by the undesired order any more when the system and the method provided by the invention are used, and more split numbers can be provided, and the split number is increased by at least one time.
3. When the function of the optical diffraction device is to perform light beam scanning, the system and the method for reducing the influence of the unwanted orders of the optical diffraction device can improve the scanning range of beam splitting. Because when the order blocked by the spatial filter is a desired order in the prior art, the beam cannot scan the region blocked by the spatial filter, and thus the scanning range is limited. When the method and the system of the invention are used for removing the spatial filter or reducing the size of the spatial filter, the scanning range of the light beam can be improved.
4. The system for attenuating the effect of unwanted orders of an optical diffraction device provided by the present invention may further comprise a relay lens group with a spatial filter, since in general applications the zero order has higher energy than other unwanted orders and remains unchanged in the middle of the optical field distribution. The spatial filter can be used to block the zero order light when the optical power density of the zero order with aberrations is reduced to an extent that is still insufficient to counteract the adverse effects thereof. The spatial filter used to block the zero order light at this time can be fixed and only have the zero order spot size, with little effect on the light field distribution.
Drawings
FIG. 1 is a schematic diagram of a system for reducing the effect of unwanted orders in an optical diffraction device, according to example 1 of the present invention;
FIG. 2 is a schematic view of a conventional system configuration using an optical diffraction device according to embodiment 1 of the present invention;
FIG. 3 is a schematic diagram of a system configuration for reducing the effect of an unwanted order of an optical diffraction device by using the system proposed by the present invention in embodiment 1 of the present invention;
FIG. 4 is a one-dimensional graph of the optical field distribution obtained by using the prior art system for reducing the unwanted order effect of an optical diffraction device based on a spatial filter according to embodiment 1 of the present invention and the optical field distribution obtained by using the system according to the present invention;
fig. 5 is a schematic diagram of a system provided in embodiment 1 of the present invention and using a spatial filter to block the zeroth order diffracted light.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Examples 1,
A system for attenuating the effects of unwanted orders in an optical diffraction device, as shown in figure 1, comprising: an optical generator 1, an optical diffraction device 2, and a light beam focusing device 4, which are disposed in this order along the optical path direction, and an aberration optical device 3 disposed between image-side focal planes of the optical generator 1 and the light beam focusing device 4; specifically, in the present embodiment, the aberration optical device 3 is placed between the optical diffraction device 2 and the beam focusing device 4;
wherein, the light generator 1 is used for providing a light source; the light generator 1 may be a laser, a light emitting diode, a mercury lamp, a halogen lamp, or the like;
the aberration optical device 3 is used for adding a first optical aberration in the optical path to cause the quality of the light beam in the optical path to be degraded; specifically, the aberration optical device 3 may be any optical device capable of adding aberration in an optical path, and specifically may be a cylindrical lens, a deformable mirror, or a lens; cylindrical lenses can introduce astigmatism; the deformable mirror can form an irregular reflective surface to introduce various aberrations including spherical aberration, astigmatism, coma, trefoil, and the like; while placement of the lens offset from the optical axis introduces astigmatism and coma upon beam incidence at the lens edge. It should be noted that the first optical aberration is different from the aberration generated during normal use of the optical device and the optical element, and is the aberration added to the optical path by purposely placing an aberration optical device in the optical path.
The optical diffraction device 2 is used for carrying out wavefront modulation on incident beams to obtain emergent light; the method for wavefront modulation of an optical beam herein comprises: modulating the amplitude of the incident light individually, modulating the phase of the incident light individually, or modulating both the amplitude and the phase of the incident light simultaneously. The wavefront modulation comprises a first wavefront modulation and a second wavefront modulation; the modulation distribution and the modulation amount corresponding to the first wavefront modulation are determined based on the function to be realized of the optical diffraction device; the second wavefront modulation is used to introduce a second optical aberration for the beam of the desired order; the second optical aberration and the first optical aberration compensate each other to achieve the effect of aberration correction. Specifically, the optical diffraction device 2 is a type of optical device that functions by an optical diffraction effect, and specifically, may be a grating, an acousto-optic deflector, an electro-optic deflector, a metamaterial, a diffractive optical element, a digital micromirror device, or a spatial light modulator. The corresponding functions to be realized by the above optical diffraction device also include: the method is used for realizing beam splitting (splitting a beam into two or more beams), beam deflection (deflecting the angle of emergent light compared with incident light), beam scanning (continuously changing the deflection angle of emergent light to realize beam scanning), beam focusing (an optical diffraction device plays the same role as a lens), aberration correction (the wavefront of the incident beam is modulated to be mutually offset with the aberration in an optical system so as to achieve the purpose of eliminating the aberration) or beam shaping (shaping the beam into required special beams, such as Bessel beam, Laguerre-Gauss beam, Rayleigh beam and the like).
The light beam focusing device 4 is used for focusing emergent light to obtain light field distribution 6 with reduced light power density of an undesired level. The beam focusing device 4 may be any optical device capable of focusing a light beam, such as an objective lens, a field lens, a spherical mirror, etc. In this embodiment, the light beam 5 is focused by the beam focusing device 4, and the desired order produces the designed light field distribution 6 at the focal plane location of the beam focusing device 4, while the undesired order is blurred by the presence of aberrations. In particular, the light field distribution 6 may be any desired distribution of light energy, such as creating multiple optical foci, performing a scan of the optical foci, generating a special spot distribution (e.g., a bessel beam, a laguerre-gaussian beam, an airy beam, etc.). The optical power density of the degraded order is reduced, and adverse effects caused in practical application, such as crosstalk in microscopic imaging, damage to a non-processed region during laser processing, and the like, can be reduced.
It should be noted that, in this embodiment, the light beam 5 generated by the light generator 1 is diffracted by the optical diffraction device 2, and since the optical diffraction device 2 is not an ideal optical device, the diffraction efficiency cannot be 100%, and two or more diffraction orders are generated. Therefore, in order to reduce the effect of the unwanted order of the optical diffraction device, when designing the modulation of the optical parameters of the optical diffraction device 2, the aberration is added to the light beam 5 by changing the distribution of the modulation parameters, and is referred to as a second optical aberration (corresponding to the second wavefront modulation described above). Since only the desired order has the designed optical parameter modulation, only the desired order increases the aberration consistent with that designed. The light beam 5 exiting the optical diffraction device 2 passes through the aberration optical device 3. The aberration optical device 3 adds a large aberration for all diffraction orders, and the aberration is recorded as a first optical aberration; since the second optical aberration of the beam of the desired order can be mutually compensated with the first optical aberration, the aberration of the desired order is substantially corrected, while the undesired order, which is not corrected for aberration, still has a larger aberration.
By applying the system provided by the present invention, the light field distribution of the desired order remains sharp (i.e., consistent with the designed light field distribution), while the light field distribution of the undesired order is degraded by the added first aberration. For example, it was originally designed to scan a light beam by the optical diffraction device and then to scan an optical focus by focusing with a lens. Since the optical diffraction device may have defects such that the diffraction efficiency cannot reach 100%, diffracted light of other orders is generated, and thus a plurality of focal points are scanned simultaneously, optical focal point scanning is generated in some unnecessary or impossible areas. The system provided by the invention only maintains a clear optical focus for the required order, and the non-required order becomes a degraded optical focus due to aberration. Because the undesired orders are degraded by aberrations, the optical power density decreases, which can reduce or even eliminate the effect of the undesired orders in applications requiring higher optical power to produce light-to-substance interaction effects, such as laser processing, biological microscopy imaging, optical storage of information, and the like.
In order to further eliminate the influence of zero-order diffracted light, the system for reducing the influence of the undesired order of the optical diffraction device, provided by the invention, can further comprise: a relay lens group with a spatial filter; the relay lens group is arranged between the optical diffraction device and the light beam focusing device, and the spatial filter is arranged between a front lens and a rear lens of the relay lens group and used for blocking zero-order light beams; the front lens is a lens which is in the relay lens group and the light beam reaches firstly along the light path direction; the rear lens is a lens which is in the relay lens group and the light beam finally reaches along the light path direction.
To further illustrate the system for attenuating the effects of unwanted orders of an optical diffraction device provided in the book embodiments, the following is compared to prior art methods for attenuating the effects of unwanted orders of an optical diffraction device:
fig. 2 is a schematic diagram showing a configuration of a conventional system using an optical diffraction device. In this configuration, the optical diffraction device is a digital micromirror device 21 to achieve optical parameter modulation of the light beam 5; only the light beam 5 is shown in fig. 2 after passing through the digital micromirror device 21, and the incident light beam is not shown in the figure. The digital micromirror device 21 comprises a plurality of tiny mirrors, each tiny mirror can independently control the reflection angle, for example, the reflection angle is ± 12 °. The intensity modulation of the incident beam can be achieved by the digital micromirror device 21, i.e., the relative intensity is 1 at a reflection angle of 12 °; the relative intensity was 0 at a reflection angle of-12 °. One possible optical parameter modulation distribution can be realized by the dmd 21 in which a white area (relative intensity of 1) represents light that can be received by the lens 71 and a black area (relative intensity of 0) represents light that cannot be received by the lens 71 because it is reflected in the other direction. The optical parameter modulation profile 91 is a binary intensity grating, and the diffraction angle of the outgoing light can be changed by changing the grating period, thereby realizing the scanning of the light beam.
Since the dmd 21 is a binary intensity modulation device, the spatial distribution of the optical parameter modulation profile 91 required to achieve the beam scanning is:
wherein, TxAnd TyThe grating periods are in the x-direction and the y-direction, respectively, and n is an integer. Whereas the optical parameter modulation profile 91, which achieves beam deflection, should ideally have a phase profile as follows:
the efficiency of the optical parameter modulation of the light beam 5 by the digital micromirror device 21 cannot reach 100%, generating additional diffraction orders. In the binary intensity modulation of the light beam, the light beam exiting the dmd 21 has three levels, i.e., +1 level 51 (shown in bold), 0 level 52, and-1 level 53; where only the +1 order 51 produces the desired beam deflection, and both the 0 order 52 and the-1 order 53 are of undesired order. If the undesired orders are not blocked, these two orders will interfere with the beam scanning of the optical diffraction device. For example, when the digital micromirror device 21 is used for laser scanning imaging, the 0-level 52 always keeping the same position still will damage the imaged sample due to the accumulation of energy; the-1 order 53 also scans across the sample resulting in crosstalk of the signals.
Generally, to eliminate the effect of the undesired orders, a common approach in the prior art is to place a spatial filter 8 (dashed line in FIG. 2) in the focal plane position of the lens 71 in the embodiment shown in FIG. 2 to block the 0 order 52 and the-1 order 53. At this time, the lens 72 and the lens 71 form a relay lens group, and the optical parameter modulation distribution 91 on the digital micromirror device 21 can be imaged on the focusing lens 41, and the light field distribution 61 is recorded on the focal plane 42 of the focusing lens 41 by a camera through the focusing of the focusing lens 41, and as can be seen from the figure, the focusing light focus of the undesired orders (0 order 52 and-1 order 53) is still obvious except the focusing light focus of the desired diffraction order (+1 order 51).
The schematic configuration of the system for reducing the effect of the unwanted orders of the optical diffraction device by using the system of the present invention is shown in fig. 3. In this configuration, unlike the conventional configuration, the present invention adds a cylindrical lens 31 for increasing aberration, the focal length of which is f, after the optical diffraction device 21And the spatial filter 8 blocking the unwanted diffraction orders is removed. The first optical aberration is added in the optical path by inserting the cylindrical lens 31, so that the quality of the light beam is deteriorated; performing wavefront modulation on the light beam by using an optical diffraction device to obtain emergent light, wherein the wavefront modulation comprises first wavefront modulation and second wavefront modulation, and the distribution 92 of the wavefront modulation is shown in fig. 3; the modulation distribution and the modulation amount corresponding to the first wavefront modulation are determined based on the function to be realized by the optical diffraction device; the second wavefront modulation introduces a second optical aberration for the beam of the desired order; the second optical aberration and the first optical aberration compensate each other to achieve the aberration correction effect. The optical parameter modulation profile 92 compensates for an increased first aberration in the system, the increased aberration being designed to be a focal length-f2Astigmatism corresponding to the cylindrical lens of (3). But only the required +1 order 51 corresponds to a cylindrical lens focal length of-f2Can compensate for the increased first aberration, and the 0 th order 52 corresponds to an infinite cylindrical lens focal length, and the-1 st order 53 corresponds to a + f cylindrical lens focal length2. Therefore, in the configuration of the present invention, in the optical field distribution 62, the +1 order 51 is clearly visible after aberration correction and both the 0 order 52 and the-1 order 53 are deteriorated due to the aberration, which is manifested in a decrease in power density, and 1/5 in the optical field distribution where the resulting unwanted order optical power density is less than the desired order optical power density can effectively reduce the adverse effect of the unwanted order on the use of the optical diffraction device 2. It should be noted that the distance between the cylindrical lens and the optical diffraction device isd, focal length f1And f2The relationship between f2＝f1-d。
Further, in order to clearly compare the effect of the system provided by the present invention on reducing the unwanted order effect of the optical diffraction device with the system in the prior art based on reducing the unwanted order effect of the optical diffraction device by using the spatial filter, a one-dimensional graph of a light field distribution 61 obtained by using the system in the prior art based on reducing the unwanted order effect of the optical diffraction device by using the spatial filter and a one-dimensional graph of a light field distribution 62 obtained by using the system provided by the present invention are respectively drawn, as shown in fig. 4, wherein the light field distribution 61 is shown by a solid line, and the light field distribution 62 is shown by a dashed line. As can be seen from fig. 4, the required intensity of the +1 order 51 remains substantially unchanged, while the intensity of the undesired orders 0 order 52 and-1 order 53 is greatly reduced after the system proposed by the present invention is adopted; therefore, the system for reducing the influence of the unwanted orders of the optical diffraction device can effectively reduce the influence of the unwanted orders on the premise of keeping the intensity of the wanted orders basically unchanged.
It should be noted that, in order to further eliminate the influence of zero order diffracted light, the system for reducing the influence of the undesired order of the optical diffraction device proposed by the present invention may further include a relay lens group with a spatial filter; the relay lens group is arranged between the optical diffraction device and the light beam focusing device, and the spatial filter is arranged between a front lens and a rear lens of the relay lens group and used for blocking zero-order light beams; the front lens is a lens which is in the relay lens group and the light beam reaches firstly along the light path direction; the rear lens is a lens which is in the relay lens group and the light beam finally reaches along the light path direction. Specifically, fig. 5 is a schematic diagram of a system configuration employing the system proposed by the present invention and using a spatial filter to block the zeroth order diffracted light. The number of lenses in the relay lens group of the present embodiment is 2 (note that the number of lenses in the relay lens group is not limited to 2, and may be 2 or more), and this configuration is different from the configuration in fig. 3 in that a spatial filter 81 for blocking the zeroth order diffracted light is disposed between the relay lens group formed by the lens 72 and the lens 71. As can be seen from the figure, in the optical field distribution 63 obtained under this configuration, the zero order light is blocked from being visible, further reducing the effect of the unwanted orders of the optical diffraction device.
Examples 2,
A method for attenuating the effects of unwanted orders of an optical diffraction device, comprising the steps of:
s1, adding a first optical aberration in the optical path of the optical diffraction device to degrade the quality of the light beam; specifically, the method of adding the first optical aberration in the optical path includes: generating astigmatism by using a cylindrical lens; alternatively, aberrations are introduced based on irregular reflective surfaces of the deformable mirror; alternatively, the beam is made incident on the edge of the lens, introducing astigmatism and coma. It should be noted that the first optical aberration is different from the aberration generated during normal use of the optical device and the optical element, and is the aberration added to the optical path by purposely placing an aberration optical device in the optical path.
S2, performing wavefront modulation on the light beam based on the optical diffraction device to obtain emergent light; the wavefront modulation comprises a first wavefront modulation and a second wavefront modulation; the modulation distribution and the modulation amount corresponding to the first wavefront modulation are determined based on the function to be realized of the optical diffraction device; the second wavefront modulation is used to introduce a second optical aberration for the beam of the desired order; the second optical aberration and the first optical aberration compensate each other to achieve the effect of aberration correction; specifically, the method for wavefront modulation of the light beam includes: modulating the amplitude of the incident light individually, modulating the phase of the incident light individually, or modulating both the amplitude and the phase of the incident light simultaneously.
And S3, focusing the emergent light to obtain the light field distribution with the decreased optical power density of the unwanted order.
It should be noted that the method for reducing the influence of the unwanted order of the optical diffraction device may be a method for reducing the influence of the unwanted order of the optical diffraction device based on the system described in embodiment 1, and related technical solutions are the same as embodiment 1 and are not described herein again.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (7)
1. A system for attenuating the effects of unwanted orders in an optical diffraction device, comprising: the optical diffraction device, the light beam focusing device and the aberration optical device are arranged along the optical path direction in sequence, and the aberration optical device is arranged between the image space focal planes of the optical generator and the light beam focusing device; the aberration optical device is a cylindrical lens or a deformable mirror;
the light generator is used for providing a light source;
the aberration optical device is used for adding first optical aberration in the optical path to cause the quality of the light beam in the optical path to be degraded;
the optical diffraction device is used for carrying out wavefront modulation on incident beams to obtain emergent light; the wavefront modulation comprises a first wavefront modulation and a second wavefront modulation; the modulation distribution and the modulation amount corresponding to the first wavefront modulation are determined based on the function to be realized by the optical diffraction device; the second wavefront modulation is used to introduce a second optical aberration for the beam of the desired order; the second optical aberration and the first optical aberration compensate each other to achieve the effect of aberration correction; and when the aberration optical device is a cylindrical lens, the equivalent focal length-f of the second optical aberration2And the focal length f of the aberration optical device1Satisfies the following conditions: f. of2＝f1-d, wherein d is the distance of the aberration optics from the optical diffraction device;
the light beam focusing device is used for focusing the emergent light to obtain the light field distribution with the decreased light power density of the non-required level.
2. The system for attenuating the effects of unwanted orders in an optical diffraction device of claim 1, wherein the optical diffraction device comprises: a grating, an acousto-optic deflector, an electro-optic deflector, a metamaterial material, a diffractive optical element DOE, a digital micro-mirror device, or a spatial light modulator.
3. The system for attenuating the effects of unwanted orders on an optical diffraction device of claim 1, wherein the functions to be performed by the optical diffraction device comprise: beam splitting, beam deflection, beam scanning, beam focusing, aberration correction, or beam shaping is achieved.
4. The system for attenuating the effects of unwanted orders of an optical diffraction device of claim 1, wherein the beam focusing device is an objective lens, a field lens, or a spherical mirror.
5. A system for attenuating the effects of unwanted orders in an optical diffraction device as claimed in any one of claims 1 to 4, further comprising: a relay lens group with a spatial filter; the relay lens group is placed between the optical diffraction device and the beam focusing device; the spatial filter is positioned between the front lens and the rear lens of the relay lens group and used for blocking the zero-order secondary light beam; the front lens is a lens which is in the relay lens group and is reached by the light beam firstly along the light path direction; the rear lens is a lens which is in the relay lens group and the light beam finally reaches along the light path direction.
6. A method for attenuating the effects of unwanted orders in an optical diffraction device, comprising the steps of:
s1, adding a first optical aberration in the optical path of the optical diffraction device through the aberration optical device to degrade the quality of the light beam; the method of adding a first optical aberration in an optical path includes: generating astigmatism by using a cylindrical lens; alternatively, aberrations are introduced based on irregular reflective surfaces of the deformable mirror; or, the light beam is made to be incident to the edge of the lens, so that astigmatism and coma are introduced;
s2, performing wavefront modulation on the light beam based on the optical diffraction device to obtain emergent light; the wavefront modulation includes a first wavefront modulation and a second wavePre-modulation; the modulation distribution and the modulation amount corresponding to the first wavefront modulation are determined based on the function to be realized by the optical diffraction device; the second wavefront modulation is used to introduce a second optical aberration for the beam of the desired order; the second optical aberration and the first optical aberration compensate each other to achieve the effect of aberration correction; and when the aberration optical device is a cylindrical lens, the equivalent focal length-f of the second optical aberration2And the focal length f of the aberration optical device1Satisfies the following conditions: f. of2＝f1-d, wherein d is the distance of the aberration optics from the optical diffraction device;
and S3, focusing the emergent light to obtain the light field distribution with the decreased optical power density of the non-required level.
7. A method for attenuating the effects of unwanted orders in an optical diffraction device according to claim 6, wherein the method of wavefront modulating the light beam comprises: modulating the amplitude of the incident light individually, modulating the phase of the incident light individually, or modulating both the amplitude and the phase of the incident light simultaneously.
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