CN111175987A - Laser spot dissipation device, laser spot dissipation method and laser projection equipment - Google Patents
Laser spot dissipation device, laser spot dissipation method and laser projection equipment Download PDFInfo
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/48—Laser speckle optics
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B21/00—Projectors or projection-type viewers; Accessories therefor
- G03B21/14—Details
- G03B21/20—Lamp housings
- G03B21/2006—Lamp housings characterised by the light source
- G03B21/2033—LED or laser light sources
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
- G03B21/00—Projectors or projection-type viewers; Accessories therefor
- G03B21/14—Details
- G03B21/20—Lamp housings
- G03B21/208—Homogenising, shaping of the illumination light
Abstract
The invention discloses a laser speckle eliminating device, a laser speckle eliminating method and laser projection equipment. The transmission mode and the mode number of the optical fiber are changed due to the change of the equivalent refractive index of the cladding, so that a plurality of different independent speckle images which change along with time can be output at the output end of the optical fiber. Due to the persistence of vision effect of human eyes, the independent speckle images are superposed in the response range of the human eyes, so that the effect of inhibiting speckles can be achieved.
Description
Technical Field
The invention relates to the technical field of projection, in particular to a laser spot dissipation device, a laser spot dissipation method and laser projection equipment.
Background
With the development of projection display technology, the requirements of people on display are increasing day by day, and high-brightness, high-saturation and wide-field display becomes the basic requirements of display. The laser has the characteristics of high brightness, good monochromaticity and the like, so that the laser is used as a potential light source for next generation projection display. However, laser light has high coherence, and a scattering phenomenon is generated in a display process, so that laser speckle is formed. Due to the existence of laser speckle, the quality of the laser displayed image is seriously affected. Therefore, how to improve the laser speckle is a problem that needs to be solved by those skilled in the art.
Disclosure of Invention
The embodiment of the invention provides a laser speckle eliminating device, a laser speckle eliminating method and laser projection equipment, which are used for improving laser speckles.
Accordingly, an embodiment of the present invention provides a laser speckle-dispersing device, including: an optical fiber having a core and a cladding; the cladding includes: a refractive index adjusting material and a carrying substrate for carrying the refractive index adjusting material;
the laser speckle dissipating apparatus further comprises: a refractive index regulating member; the refractive index regulating and controlling component is used for controlling the refractive index of the refractive index regulating material to change along with time, so that the equivalent refractive index of the cladding changes along with the change of the refractive index regulating material; wherein the equivalent refractive index is related to the refractive index of the refractive index adjusting material and the refractive index of the carrier substrate.
Optionally, in an embodiment of the present invention, the carrier substrate has a filled void; the refractive index adjusting material is encapsulated in the filling gap.
Optionally, in an embodiment of the present invention, the optical fiber includes: a total internal reflection photonic crystal fiber; the bearing substrate is a cladding structure of the total internal reflection type photonic crystal fiber.
Optionally, in an embodiment of the present invention, the core is a single silica core, and the supporting substrate is a capillary.
Optionally, in an embodiment of the present invention, the refractive index adjusting material includes: a magnetic fluid; the refractive index regulating component is used for generating a magnetic field with the magnetic induction intensity changing along with time, and controlling the refractive index of the refractive index regulating material to change through the generated magnetic field; alternatively, the first and second electrodes may be,
the refractive index adjusting material includes: a liquid crystal or electrolyte; the refractive index regulating component is used for generating voltage which is loaded on the refractive index regulating material and changes along with time, and the refractive index of the refractive index regulating material is controlled to change through an electric field generated by the voltage.
Correspondingly, an embodiment of the present invention further provides a laser projection apparatus, including: the embodiment of the invention provides a laser speckle-dissipating device.
Optionally, in an embodiment of the present invention, the laser projection apparatus further includes: the laser spot dissipation device comprises a laser light source device positioned on the light inlet side of the laser spot dissipation device, a light valve modulation component positioned on the light outlet side of the laser spot dissipation device, and a projection lens positioned on the light outlet side of the light valve modulation component.
Correspondingly, an embodiment of the present invention further provides a laser speckle elimination method for a laser speckle elimination device provided by the embodiment of the present invention, including:
and driving the refractive index regulating and controlling component to control the refractive index of the refractive index regulating material to change along with time, so that the equivalent refractive index of the cladding changes along with the change of the refractive index regulating material.
Optionally, in an embodiment of the present invention, the refractive index adjusting material includes: a magnetic fluid; the driving of the refractive index adjusting and controlling component to control the change of the refractive index adjusting material along with time specifically comprises: driving the refractive index regulating component to generate a magnetic field with the magnetic induction intensity changing along with time, and controlling the refractive index of the refractive index regulating material to change through the generated magnetic field; alternatively, the first and second electrodes may be,
the refractive index adjusting material includes: a liquid crystal or electrolyte; the driving of the refractive index adjusting and controlling component to control the change of the refractive index adjusting material along with time specifically comprises: and driving the refractive index regulating and controlling component to generate voltage which is loaded on the refractive index regulating material and changes along with time, and controlling the refractive index of the refractive index regulating material to change through an electric field generated by the voltage.
Optionally, in an embodiment of the present invention, the driving the refractive index adjusting and controlling component to generate magnetic fields with different magnetic induction intensities specifically includes:
in a first preset cycle period, driving the refractive index regulating and controlling component to generate a magnetic field with the magnetic induction intensity increasing in sequence;
the driving of the refractive index adjusting member to generate a voltage that is applied to the refractive index adjusting material and varies with time specifically includes:
and in a second preset cycle period, driving the refractive index regulating and controlling part to generate voltages which are sequentially increased or decreased progressively.
The invention has the following beneficial effects:
according to the laser speckle eliminating device, the laser speckle eliminating method and the laser projection equipment provided by the embodiment of the invention, the cladding comprises the refractive index adjusting material and the bearing base material for bearing the refractive index adjusting material, and the refractive index of the refractive index adjusting material is adjusted and controlled by the refractive index adjusting part, so that the refractive index of the refractive index adjusting material is changed along with time, and the equivalent refractive index of the cladding is also changed along with time. The transmission mode and the mode number of the optical fiber are changed due to the change of the equivalent refractive index of the cladding, so that a plurality of different independent speckle images which change along with time can be output at the output end of the optical fiber. Due to the persistence of vision effect of human eyes, the independent speckle images are superposed in the response range of the human eyes, so that the effect of inhibiting speckles can be achieved.
Drawings
FIG. 1a is a schematic diagram of a conventional optical fiber;
FIG. 1b is a schematic view of the optical fiber shown in FIG. 1a transmitting light;
FIG. 2a is a schematic diagram of a simulation of the optical field distribution of light exiting the fiber with a cladding index of 1.435;
FIG. 2b is a schematic diagram of a simulation of the optical field distribution of light exiting the fiber with a cladding index of 1.436;
FIG. 2c is a schematic diagram of a simulation of the optical field distribution of light exiting the fiber when the cladding index is 1.437;
fig. 3 is a schematic structural diagram of a laser speckle-eliminating device according to an embodiment of the present invention;
FIG. 4a is one of the schematic structural views of the cross section along AA' shown in FIG. 3;
FIG. 4b is a second schematic structural view of the cross-section along AA' shown in FIG. 3;
fig. 5 is a schematic structural diagram of a laser speckle-eliminating device according to an embodiment of the present invention;
FIG. 6a is a schematic diagram of speckle simulation performed when the magnetic induction density is 0 Gs;
FIG. 6b is a schematic diagram of speckle simulation performed when the magnetic induction density is 469 Gs;
fig. 7 is a schematic structural diagram of a laser projection apparatus according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, specific embodiments of a laser speckle removing device, a laser speckle removing method and a laser projection apparatus provided by embodiments of the present invention are described in detail below with reference to the accompanying drawings. It should be understood that the preferred embodiments described below are only for illustrating and explaining the present invention and are not to be used for limiting the present invention. And the embodiments and features of the embodiments in the present application may be combined with each other without conflict. It should be noted that the sizes and shapes of the figures in the drawings are not to be considered true scale, but are merely intended to schematically illustrate the present invention. And the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.
When a coherent laser beam strikes a rough surface, light interference occurs between light reflected or transmitted from the rough surface, and thus, a granular spot having uneven intensity distribution is represented, which is called speckle. In laser displays, the presence of speckle will degrade image quality and must be suppressed.
Example one
As shown in fig. 1a and 1b, a general optical fiber generally includes: core 01 and cladding 02. In order that the light L1 incident on the core 01 can be transmitted by total reflection, the refractive index n of the core 0101Refractive index n greater than cladding 0202. According to the total reflection principle, the optical fiber has an incident critical angle theta (called incident critical angle for short) on the end face of the optical fibermaxWhen incident angle theta of incident light L1i1<θmaxThen, the corresponding light will be totally internally reflected at the interface between the core 01 and the cladding 02 and return to the core 01, and propagate in a zigzag manner (e.g., light L1'). When incident angle theta of incident light ray L2i2>θmaxAt this time, the corresponding light exits into the cladding and cannot propagate through the fiber (e.g., light L2').
The change in the refractive index of the cladding of the fiber affects the normalized frequency V of the fiber, and the transmission mode of the fiber is generally determined by the normalized frequency V of the fiber, so the change in the normalized frequency V affects the mode number M of the transmission mode of the multimode fiber. The mode number M of the transmission mode of the multimode step fiber meets the formula:
where λ represents the wavelength of light and a represents the core radius of the fiber. At V>2.405, the fiber is multimode, i.e., the larger V, the more transmission modes. And the contrast C after the N independent speckle images are superposed can satisfy the formula:
by the formula
It can be seen that the larger the number N of independent speckle images is, the smaller the speckle contrast will be. For multimode step fibers, the number of speckles across the fiber core end face is approximately equal to the number of modes of the transmission mode in the fiber, i.e., M ≈ N. Therefore, by adjusting the size of M, the size of N can be adjusted. And M is in turn in combination with n02Related, therefore, changes in the refractive index of the fiber cladding can affect the lightA change in fiber speckle. Taking the core directly at 62.5nm, the core refractive index at 1.456 as an example, and the cladding refractive indices at 1.435, 1.436, and 1.437, respectively, the optical field distribution of the light emitted from the fiber was simulated as shown in fig. 2a to 2 c. Fig. 2a is a schematic diagram showing a simulation of the optical field distribution of light emitted from the optical fiber when the cladding refractive index is 1.435, fig. 2b is a schematic diagram showing a simulation of the optical field distribution of light emitted from the optical fiber when the cladding refractive index is 1.436, and fig. 2c is a schematic diagram showing a simulation of the optical field distribution of light emitted from the optical fiber when the cladding refractive index is 1.437. As can be seen from fig. 2a to 2c, images with different light intensity distributions can be obtained by changing the refractive index of the cladding.
Generally, when the material of the cladding is large, the refractive index of the cladding can be approximately regarded as the equivalent refractive index of the cladding, and the equivalent refractive index n of the cladding0The formula can be satisfied:
wherein K represents the total number of kinds of materials contained in the clad layer, 1. ltoreq. k.ltoreq.K is an integer, SkRepresenting the total cross-sectional area of the kth material, nkRepresenting the refractive index of the kth class of materials. When the cladding has only one material, the equivalent refractive index n of the cladding0I.e. the refractive index of the material, for example the optical fibre shown in figure 1a, can be considered n0＝n02. Therefore, the number of transmission modes of the optical fiber is always fixed, so that the speckle pattern observed from the output end of the optical fiber is not changed along with time, the contrast of speckles is not reduced, and the speckle dissipation effect is not realized.
Based on this, as shown in fig. 3 to 4b, an embodiment of the present invention provides a laser speckle dispersing device, which may include: an optical fiber 10 having a core 11 and a cladding 12; wherein the cladding 12 may include: a refractive index adjusting material 121 and a supporting base material 122 for supporting the refractive index adjusting material. The laser speckle dissipating apparatus may further comprise: a refractive index regulating member 20; the refractive index regulating member 20 is used for controlling the change of the refractive index regulating material 121 with time, so that the equivalent refractive index of the cladding 12 is changed with the refractive index of the refractive index regulating material 121Change by change; wherein the equivalent refractive index is related to the refractive index of the refractive index adjusting material and the refractive index of the supporting substrate. In particular, the equivalent refractive index n0Refractive index n with refractive index adjusting material 1211And refractive index n of the supporting substrate 1222Satisfies the formula:
wherein S is1Represents the total cross-sectional area, S, of the refractive index adjusting material 1212Representing the total cross-sectional area of the carrier substrate 122.
According to the laser speckle removing device provided by the embodiment of the invention, the cladding comprises the refractive index adjusting material and the bearing base material for bearing the refractive index adjusting material, and the refractive index of the refractive index adjusting material is adjusted and controlled by the refractive index adjusting and controlling component, so that the refractive index of the refractive index adjusting material is changed along with time, and the equivalent refractive index of the cladding is also changed along with time. The transmission mode and the mode number of the optical fiber are changed due to the change of the equivalent refractive index of the cladding, so that a plurality of different independent speckle images which change along with time can be output at the output end of the optical fiber. Due to the persistence of vision effect of human eyes, the independent speckle images are superposed in the response range of the human eyes, so that the effect of inhibiting speckles can be achieved.
In specific implementation, the refractive index n of the core can be made to be total reflection1Greater than the equivalent refractive index n of the cladding0And, in order to secure the coupling efficiency and transmission efficiency of light in the optical fiber, n is required to be used1And n0The difference is 1 to 2 percent.
In one embodiment, as shown in fig. 4a and 4b, the carrier substrate has a filling gap; the refractive index adjusting material 121 is encapsulated in the filled space. Specifically, the filled voids, when not filled with the refractive-index adjusting material 121, may be micro-structured air holes or filled holes extending from the input end of the optical fiber to the output end thereof and provided in the cladding. Alternatively, the filling hole may be a closed filling hole provided in the cladding, which is not limited herein.
In one possible embodiment, the package of the total internal reflection photonic crystal fiberThe layer structure has a plurality of periodic air hole structures, so in practice, as shown in fig. 4a, the optical fiber may include: a total internal reflection photonic crystal fiber; the bearing substrate is a cladding structure of the total internal reflection type photonic crystal fiber. The refractive index adjusting material can be encapsulated in the air hole structure of the cladding structure of the total internal reflection type photonic crystal fiber. Wherein, the diameter of the fiber core in the total internal reflection type photonic crystal fiber can be 7 μm, the diameter of the air hole structure can be 2.57 μm, and the materials of the fiber core and the cladding structure can be SiO respectively2The refractive indices of the core and cladding structures may be 1.456, respectively. In addition, in practical applications, the total internal reflection type photonic crystal fiber is basically the same as that in the prior art, and is understood by those skilled in the art, and thus no further description is provided herein.
In another possible embodiment, the capillary has a void, and in particular, as shown in fig. 4b, the core can be configured as a single silica core, and the supporting substrate can also be a capillary. Thus, the refractive index adjusting material can be packaged in the gap between the capillary and the fiber core, and the combined optical fiber can form a multimode optical fiber. Wherein, the materials of the fiber core and the capillary can be SiO respectively2The refractive indices of the core and the capillary may be 1.456, respectively. In practical applications, the capillary tube is substantially the same as that in the prior art, and is understood by those skilled in the art, and will not be described herein.
In one possible embodiment, the magnetic fluid is also called magnetic liquid, ferrofluid or magnetoliquid, which has both the fluidity of a liquid and the magnetism of a solid magnetic material. The magnetic fluid is a stable colloidal liquid formed by mixing magnetic solid particles with the diameter of nanometer level (below 10 nanometers), base carrier liquid (also called medium) and a surfactant. The magnetic fluid shows magnetism when an external magnetic field acts. Therefore, when the magnetic induction intensity of the external magnetic field changes, the refractive index of the magnetic fluid can be changed. In particular implementations, the refractive index adjusting material may include: and (4) magnetic fluid. And the refractive index regulating member may be configured to generate a magnetic field in which magnetic induction intensity changes with time, and control the refractive index of the refractive index regulating material to change by the generated magnetic field. Taking the total internal reflection type photonic crystal fiber as an example, the magnetic fluid is encapsulated in the air hole structure of the cladding structure of the total internal reflection type photonic crystal fiber, and the refractive index regulating and controlling component is controlled to generate a proper magnetic field, so that the fiber is arranged in the magnetic field generated by the refractive index regulating and controlling component, and thus when the magnetic induction intensity of the magnetic field generated by the refractive index regulating and controlling component changes along with time, the refractive index of the magnetic fluid also changes along with time, and further the equivalent refractive index of the cladding structure can change. The volume ratio concentration of the magnetic fluid and the base carrier liquid affects the refractive index of the magnetic fluid, and the lower the volume ratio concentration is, the lower the refractive index is. Therefore, the appropriate magnetofluid volume ratio concentration needs to be set according to the condition that the difference between n1 and n0 is 1% -2%, so that the refractive index of the magnetofluid is smaller than that of the fiber core.
It should be noted that, in practical applications, the refractive index adjusting and controlling component may be a device capable of generating a magnetic field that changes with time, such as a magnetic field generating device and an electromagnetic induction device, which may be the same as the structure in the prior art, and will not be described herein again.
In another possible embodiment, the refractive index of the liquid crystal or electrolyte changes when the electric field strength of the electric field applied to it changes. In particular implementations, the refractive index adjusting material may also include: liquid crystals or electrolytes. The refractive index adjusting member may be configured to generate a voltage that is applied to the refractive index adjusting material and varies with time, and control the refractive index of the refractive index adjusting material to vary by an electric field generated by the voltage. Specifically, taking the cladding structure of the total internal reflection photonic crystal fiber as an example, as shown in fig. 4a, the refractive index adjusting material is liquid crystal, and the supporting substrate is total internal reflection photonic crystal fiber, so that the liquid crystal is filled and encapsulated in the air hole structure of the cladding structure of the total internal reflection photonic crystal fiber. The refractive index regulating part 20 is controlled to generate appropriate voltage, the voltage generates a corresponding electric field, so that the equivalent refractive index n0 of the cladding and the refractive index n1 of the fiber core meet the condition of 1% -2% of phase difference, the optical fiber 10 is arranged in the electric field generated by the refractive index regulating part 20, and the electric field intensity of the electric field generated by the refractive index regulating part 20When the degree changes, the refractive index of the liquid crystal changes. Thus according to the formula
As can be seen, the equivalent refractive index n of the cladding 120And will vary accordingly. Since n is0And the number of transmission modes and modes in the optical fiber are changed correspondingly, so that the number of independent speckle images output by the output end of the optical fiber is also changed. Due to the persistence effect of human eyes, the independent speckle images are superposed in the response range of the human eyes, so that the effect of inhibiting speckles can be achieved. In practical applications, the refractive index adjusting component may be a device capable of generating an electric field that changes with time, such as an electric field generating device, which may be the same as the structure in the prior art and is not described herein again.
The embodiment of the invention also provides a laser speckle eliminating method of the laser speckle eliminating device, which comprises the following steps: the driving refractive index regulating component controls the refractive index of the refractive index regulating material to change along with time, so that the equivalent refractive index of the cladding changes along with the change of the refractive index regulating material.
In particular implementations, the refractive index adjusting material includes: and (4) magnetic fluid. In the embodiment of the present invention, driving the refractive index adjusting member to control the change of the refractive index adjusting material with time may specifically include:
the refractive index regulating component is driven to generate a magnetic field with the magnetic induction intensity changing along with time, and the refractive index of the refractive index regulating material is controlled to change through the generated magnetic field.
Further, in specific implementation, the driving the refractive index adjusting member to generate magnetic fields with different magnetic induction intensities may specifically include:
and in a first preset cycle period, driving the refractive index regulating and controlling component to generate a magnetic field with the magnetic induction intensity increasing in sequence. In this way, the magnetic induction intensity of the magnetic field can be controlled to increase gradually in sequence, that is, the magnetic induction intensity of the magnetic field is controlled to increase gradually from the initial value in the first preset cycle period, the magnetic induction intensity of the magnetic field is controlled to increase gradually from the initial value in the second first preset cycle period, and the rest is analogized, which is not limited herein. Further, a certain time is required for the human eyes to receive the object, and the duration of the first preset cycle period can be the human eye receiving time. Specifically, the human eye reception time may be 1/24 second or less.
In one possible embodiment, the refractive index control member may be controlled to operate according to the following parameters: when the diameter of the fiber core is 16 mu m and the refractive index of the fiber core is 1.5, the refractive index regulating and controlling component is controlled to work under the condition of stepping 7Gs every 0.4ms or modulating voltage with the frequency of 24Hz, so that in a first preset cycle period, the refractive index regulating and controlling component is driven to generate a magnetic field with the magnetic induction intensity gradually increased from 0Gs to 700Gs, the magnetic induction intensity is modulated by stepping 7Gs, the refractive index of the magnetic fluid is changed from 1.46 to 1.48, and the mode number of the transmission mode of the optical fiber is increased along with the increase of the refractive index of the magnetic fluid. This may increase the number of independent speckle images output by the output end of the fiber. Due to the persistence effect of human eyes, the independent speckle images are superposed in the response range of the human eyes, so that the effect of inhibiting speckles can be achieved. And in a second first preset cycle period, enabling the refractive index regulating and controlling component to generate a magnetic field with the magnetic induction intensity gradually increased from 0Gs to 700Gs again according to the parameters, so that the magnetic induction intensity is modulated in a step of 7Gs, the refractive index of the magnetic fluid is changed from 1.46 to 1.48, and the mode number of the transmission mode of the optical fiber is increased along with the increase of the refractive index of the magnetic fluid. This may increase the number of independent speckle images output by the output end of the fiber. Due to the persistence effect of human eyes, the independent speckle images are superposed in the response range of the human eyes, so that the effect of inhibiting speckles can be achieved. Of course, in practical applications, the above parameters may be designed and determined according to practical application environments, and are not limited herein, because requirements for the step and the size of the magnetic induction intensity are different.
Taking the case that the carrying substrate is the cladding structure of the total internal reflection photonic crystal fiber as an example, the magnetic fluid is encapsulated in the carrying substrate, the refractive index of the fiber core 11 of the fiber 10 is 1.450, the wavelength of the laser light source is 671nm,the radius of the optical fiber is 62.5 μm, the refractive index of the magnetic fluid in a magnetic field-free environment at 20 ℃ is 1.44714 for example, as shown in fig. 5, the refractive index regulating component 20 is controlled to generate a suitable magnetic field so that the equivalent refractive index n0 of the cladding and the refractive index n1 of the fiber core satisfy the condition of a difference of 1% to 2%, the optical fiber 10 is arranged in the magnetic field generated by the refractive index regulating component 20, and the refractive index of the magnetic fluid also changes with time when the magnetic induction intensity of the magnetic field generated by the refractive index regulating component 20 changes with time. Laser is injected into the light inlet surface of the optical fiber through the laser light source device, the influence of the magnetic induction intensity on the mode number of the optical fiber transmission mode is detected, as shown in table 1, as can be seen from table 1, the refractive index of the magnetic fluid is reduced along with the increase of the magnetic induction intensity, and thus, according to a formula
As can be seen, the equivalent refractive index n of the cladding 120And correspondingly over time. Since n is0And the mode number of the transmission mode in the optical fiber is changed correspondingly, so that the output end of the optical fiber outputs independent speckle images changing along with time. That is, the more diverse the transmission mode, the better the speckle cancellation. Due to the persistence effect of human eyes, the independent speckle images are superposed in the response range of the human eyes, so that the effect of inhibiting speckles can be achieved. The refractive index change of the magnetic fluid is a change in refractive index at different magnetic induction intensities relative to the refractive index of the magnetic fluid when no magnetic field is applied, and the formula is the refractive index change of the magnetic fluid (refractive index of the magnetic fluid when no magnetic field is applied-refractive index of the magnetic fluid when a magnetic field of different magnetic induction intensities is applied)/refractive index of the magnetic fluid when no magnetic field is applied. The change in the number of transmission modes satisfies the formula: the change of the transmission mode number is the transmission mode number of the multimode optical fiber when the magnetic field with different magnetic induction intensity is added to the multimode optical fiber, and the transmission mode number of the multimode optical fiber when the magnetic field is not added.
TABLE 1
And aiming at the cladding structure of the bearing substrate which is the total internal reflection type photonic crystal fiber, the magnetofluid is packaged in the laser speckle-dissipating device of the bearing substrate, the fiber core of the laser speckle-dissipating device is directly 62.5nm, and the refractive index of the fiber core is 1.456. As shown in fig. 5, light L3 is transmitted to the light incident surface of the core 11 by the laser light source, and speckles generated by the laser speckle elimination device are simulated under the action of magnetic fields with magnetic induction intensities of 0Gs and 469Gs, respectively, as shown in fig. 6a and 6 b. Fig. 6a is a schematic diagram of simulating speckles when the magnetic induction intensity is 0Gs, and fig. 6b is a schematic diagram of simulating speckles when the magnetic induction intensity is 469 Gs. As can be seen from fig. 6a and 6b, the speckle images are different for different magnetic induction intensities. And experimental tests show that the speckle contrast can be reduced to below 4%, and the laser projection image display requirements can be met.
In particular implementations, the refractive index adjusting material includes: liquid crystals or electrolytes. In the embodiment of the present invention, the driving the refractive index adjusting member to control the change of the refractive index adjusting material with time specifically includes:
the refractive index regulating member is driven to generate a voltage which is applied to the refractive index regulating material and changes with time, and the refractive index of the refractive index regulating material is controlled to change by an electric field generated by the voltage.
Further, in an implementation, driving the refractive index adjusting member to generate a time-varying voltage applied to the refractive index adjusting material may specifically include:
and in a second preset cycle period, driving the refractive index regulating and controlling component to generate voltages which are sequentially increased or decreased progressively. This allows the voltage to be cyclically controlled to increase or decrease in sequence, thereby causing the electric field generated to vary with time. Taking the cyclic control voltage sequentially increasing as an example, the control voltage sequentially increases from the initial value in the first and second preset cyclic periods, the control voltage sequentially increases from the initial value again in the second and first preset cyclic periods, and the rest is similar to the above, which is not limited herein. Further, a certain time is required for the human eyes to receive the objects, and the duration of the second preset cycle period can be the human eye receiving time. Specifically, the human eye reception time may be 1/24 second or less. This makes it possible to change the refractive index of the liquid crystal by modulating the electric field intensity, and further to change the sum mode number of the transmission modes of the optical fiber according to the change in the refractive index of the liquid crystal. This can vary the number of independent speckle images output by the output ends of the fibers. Due to the persistence effect of human eyes, the independent speckle images are superposed in the response range of the human eyes, so that the effect of inhibiting speckles can be achieved.
Example two
An embodiment of the present invention further provides a laser projection apparatus, including: the embodiment of the invention provides a laser speckle dispersing device 100. The specific structure of the laser spot-dissipating device 100 is described in the first embodiment, and is not described herein.
In a specific implementation, as shown in fig. 7, the laser projection apparatus may further include: the laser speckle dispersing device comprises a laser speckle dispersing device 100, a laser light source device 200 positioned at the light inlet side of the laser speckle dispersing device 100, a light valve modulation component 300 positioned at the light outlet side of the laser speckle dispersing device 100, and a projection lens 400 positioned at the light outlet side of the light valve modulation component 300.
In particular implementation, the laser light source device 200 emits multi-primary-color laser light and is coupled to the incident surface of the optical fiber 10 of the laser speckle reduction device 100 to form incident light to the fiber core 11. The transmission mode number of the incident light in the fiber core 11 can be changed and emitted through the action of the laser speckle dispersing device 100, and then the emitted light is incident to the light valve modulation component 300, and enters the projection lens 400 after being modulated by the light valve modulation component 300 to the incident light with different colors, so that the image imaged by the projection lens 400 meets the requirement.
In one embodiment, the light valve modulating component 300 may be a Digital micromirror chip (DMD). The laser projection device provided by the embodiment of the invention can adopt a Digital Light Processing (DLP) framework, and the image signal is digitally processed, so that different colors of Light rays emitted by the laser Light source device in a time sequence are projected on the DMD chip, the DMD chip modulates and reflects the Light rays according to the Digital signal, and finally the Light rays are imaged on the projection screen through the projection lens.
In general, an illumination optical path is further provided in the light valve modulation section to perform compression shaping processing on an incident light beam. In specific implementation, the laser speckle-eliminating device can be arranged in the laser light source device, and also can be arranged in the illumination light path of the light valve modulation component, so that the speckle elimination of the laser beam can be realized.
It should be noted that other essential components of the laser projection apparatus are understood by those skilled in the art, and are not described herein nor should they be construed as limiting the present invention.
According to the laser speckle eliminating device, the laser speckle eliminating method and the laser projection equipment provided by the embodiment of the invention, the cladding comprises the refractive index adjusting material and the bearing base material for bearing the refractive index adjusting material, and the refractive index of the refractive index adjusting material is adjusted and controlled by the refractive index adjusting part, so that the refractive index of the refractive index adjusting material is changed along with time, and the equivalent refractive index of the cladding is also changed along with time. The transmission mode and the mode number of the optical fiber are changed due to the change of the equivalent refractive index of the cladding, so that a plurality of different independent speckle images which change along with time can be output at the output end of the optical fiber. Due to the persistence of vision effect of human eyes, the independent speckle images are superposed in the response range of the human eyes, so that the effect of inhibiting speckles can be achieved.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. A laser speckle-dissipating apparatus comprising: an optical fiber having a core and a cladding; wherein the cladding layer comprises: a refractive index adjusting material and a carrying substrate for carrying the refractive index adjusting material;
the laser speckle dissipating apparatus further comprises: a refractive index regulating member; the refractive index regulating and controlling component is used for controlling the refractive index of the refractive index regulating material to change along with time, so that the equivalent refractive index of the cladding changes along with the change of the refractive index regulating material; wherein the equivalent refractive index is related to the refractive index of the refractive index adjusting material and the refractive index of the carrier substrate.
2. The laser speckle-removing device of claim 1, wherein the carrier substrate has a filled void; the refractive index adjusting material is encapsulated in the filling gap.
3. The laser speckle dissipating apparatus of claim 2, wherein the optical fiber comprises: a total internal reflection photonic crystal fiber; the bearing substrate is a cladding structure of the total internal reflection type photonic crystal fiber.
4. The laser speckle dissipating device of claim 2, wherein the core is a single silica core and the carrier substrate is a capillary tube.
5. The laser speckle dissipating apparatus of any one of claims 1-4, wherein the refractive index adjusting material comprises: a magnetic fluid; the refractive index regulating component is used for generating a magnetic field with the magnetic induction intensity changing along with time, and controlling the refractive index of the refractive index regulating material to change through the generated magnetic field; alternatively, the first and second electrodes may be,
the refractive index adjusting material includes: a liquid crystal or electrolyte; the refractive index regulating component is used for generating voltage which is loaded on the refractive index regulating material and changes along with time, and the refractive index of the refractive index regulating material is controlled to change through an electric field generated by the voltage.
6. A laser projection device, comprising: the laser speckle dissipating apparatus of any one of claims 1-5.
7. The laser projection device of claim 6, wherein the laser projection device further comprises: the laser spot dissipation device comprises a laser light source device positioned on the light inlet side of the laser spot dissipation device, a light valve modulation component positioned on the light outlet side of the laser spot dissipation device, and a projection lens positioned on the light outlet side of the light valve modulation component.
8. A method for dissipating a laser spot of a laser speckle-eliminating device according to any one of claims 1 to 5, comprising:
and driving the refractive index regulating and controlling component to control the refractive index of the refractive index regulating material to change along with time, so that the equivalent refractive index of the cladding changes along with the change of the refractive index regulating material.
9. The laser speckle method of claim 8, wherein the refractive index adjusting material comprises: a magnetic fluid; the driving of the refractive index adjusting and controlling component to control the change of the refractive index adjusting material along with time specifically comprises: driving the refractive index regulating component to generate a magnetic field with the magnetic induction intensity changing along with time, and controlling the refractive index of the refractive index regulating material to change through the generated magnetic field; alternatively, the first and second electrodes may be,
the refractive index adjusting material includes: a liquid crystal or electrolyte; the driving of the refractive index adjusting and controlling component to control the change of the refractive index adjusting material along with time specifically comprises: and driving the refractive index regulating and controlling component to generate voltage which is loaded on the refractive index regulating material and changes along with time, and controlling the refractive index of the refractive index regulating material to change through an electric field generated by the voltage.
10. The method for dissipating the laser speckle as defined in claim 9, wherein the driving the refractive index adjusting member to generate magnetic fields with different magnetic induction strengths comprises:
in a first preset cycle period, driving the refractive index regulating and controlling component to generate a magnetic field with the magnetic induction intensity increasing in sequence;
the driving of the refractive index adjusting member to generate a voltage that is applied to the refractive index adjusting material and varies with time specifically includes:
and in a second preset cycle period, driving the refractive index regulating and controlling part to generate voltages which are sequentially increased or decreased progressively.
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