Laser reflector with speckle suppression function and laser projection chip

Abstract

The invention relates to a laser reflector with a speckle suppression function and a laser projection chip, the laser projection chip comprises a reflector, a mirror body of the reflector is provided with a multi-layer functional structure, and the multi-layer functional structure comprises a high-repetition composite film, a lower electrode layer, a phase modulation layer, an upper electrode layer and a protective layer from bottom to top; voltages with different intensities can be applied between the upper electrode layer and the lower electrode layer, so that a controlled electric field is formed in a space within the range of the upper and lower surfaces of the phase modulation layer; the applied voltage is set as a random signal, the refractive index of the phase modulation layer changes randomly, the phase of the reflected light changes randomly, the time coherence of the reflected light is damaged, and therefore speckles on a laser projection target surface are restrained. According to the invention, no extra speckle suppression device is needed, the corresponding functional layer is arranged on the surface of the mirror body, the dual functions of single-chip laser projection and speckle suppression are realized, the structure is very compact, the size is small, and the device is easy to apply in miniaturized three-dimensional imaging equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of light beam control devices, and in particular to a laser reflector and a laser projection chip with a speckle suppression function. Background Art

[0002] Structured light 3D imaging is an important 3D imaging method at present. In structured light 3D imaging, MEMS projection chip is a commonly used beam control device. Its function is to control the incident laser to form the required structured light and project it onto the target surface. Common structured light includes stripes, patterns, etc. In this scheme, the laser is projected onto the target surface. Due to the coherence of the laser, speckle will be generated, resulting in poor imaging effect. There are currently a variety of technical solutions to suppress the speckle problem. The principles of various solutions are all attributed to reducing the temporal coherence or spatial coherence of the projected laser beam.

[0003] For example, the invention with patent application number 201010100208.2 discloses a light source device for reducing speckle and a method for reducing speckle, which adds an optical diffuser in the light path and performs random vibration, and adds an additional random phase in the light path to suppress speckle. This solution is easy to implement and has a good speckle suppression effect, but it requires additional devices and needs to drive the homogenizing device, which is large in size, resulting in poor system integration and difficulty in miniaturization.

[0004] There are also technical solutions that use micromirror arrays to suppress speckle. For example, the invention with patent application number ZL201210512289.6 provides a binary phase modulator structure using a micromirror array. This solution requires the design and manufacture of arrayed micromirror devices, which significantly increases the difficulty of design and processing.

[0005] There are also technical solutions that use a combination of piezoelectric crystals and nanostructures to reduce speckle, which has a certain effect of suppressing speckle. For example, the invention with patent application number ZL202010120186.X provides a speckle suppression device that combines randomly distributed nanophase units with piezoelectric mirrors, but this solution is still a separate speckle suppression device that needs to be integrated with a laser projection chip, and is not easy to apply in scenarios with high requirements such as volume and power consumption; the nanophase units in this solution need to prepare randomly distributed nanounits, the contours of these nanounits are circular, rectangular or elliptical, and the characteristic size is smaller than the working band, and these units are three-dimensional structures with a certain height, which are difficult to process. Summary of the invention

[0006] In order to overcome the defects of the above-mentioned prior art, the purpose of the present invention is to provide a laser reflector and a laser projection chip with a speckle suppression function. No additional speckle suppression device is required. By setting a corresponding functional layer on the surface of the laser projection chip, the dual functions of single-chip laser projection and speckle suppression are achieved. The structure is very compact and the size is small, and it is easy to use in miniaturized three-dimensional imaging equipment.

[0007] In order to achieve the above object, the technical solution of the present invention is:

[0008] A laser reflector with a speckle suppression function comprises a mirror body 1-1, on which a multi-layer functional structure is arranged, from bottom to top, respectively, a high-reflection composite film 1-6, a lower electrode layer 1-5, a phase-adjusting layer 1-4, an upper electrode layer 1-3 and a protective layer 1-2; voltages of different strengths can be applied between the upper electrode layer 1-3 and the lower electrode layer 1-5, so that a controlled electric field is formed in the space within the upper and lower surfaces of the phase-adjusting layer 1-4.

[0009] The upper electrode layer 1-3 and the lower electrode layer 1-5 are one or more groups of electrodes, each group of electrodes is a planar mesh structure composed of transparent conductive films or nanowires; when there are multiple groups of electrodes, an insulating layer is set between each group of electrodes to insulate each other.

[0010] When an electrical signal is applied between the upper electrode layer 1-3 and the lower electrode layer 1-5, one or more groups of electrodes are selected at the same time, or one or more groups of electrodes are randomly selected at different times to enhance the randomness of the time series and spatial sequence of the light field, and reduce the coherence by phase superposition of the time series and / or spatial sequence, thereby effectively suppressing speckle.

[0011] The material of the phase adjustment layer 1-4 is a single layer or multilayer electro-optical material film whose refractive index can change with an external electric field. The phase adjustment layer 1-4 is a patterned array, which includes at least two or more units, and each unit responds differently to the same electrical excitation.

[0012] The materials of each unit of the phase modulation layer are different; or although they are the same material, the material of each unit area responds differently to the same electrical excitation after being processed.

[0013] The protective layer 1-2 is a single layer or a multi-layer combination of silicon oxide, silicon nitride, amorphous silicon, or PDMS, PMMA or a high temperature resistant adhesive material.

[0014] The high-reflective composite films 1-6 are single-layer or multi-layer silicon oxide, silicon nitride, titanium oxide, hafnium oxide, zirconium oxide, zinc sulfide, zinc telluride or composite materials thereof; each layer of the materials is alternately or sequentially stacked.

[0015] The manufacturing method of the phase-adjusting layer 1-4 is as follows: depositing one or more layers of electro-optical material thin film on the upper surface of the lower electrode 1-5, and then using laser to structurally modify the deposited thin film, so that the refractive index of the part illuminated by the laser light changes, thereby realizing an arrayed phase-adjusting layer.

[0016] The manufacturing method of the phase adjustment layer 1-4 is as follows: depositing a first phase adjustment layer material on the upper surface of the lower electrode 1-5, and then patterning the first phase adjustment layer material film; then depositing a second phase adjustment layer material, patterning it by photolithography, removing excess second phase adjustment layer material, and so on. The above process is repeated for multiple film layers, so that each unit in the patterned array responds differently to the same electrical excitation, and finally manufacturing an upper electrode layer 1-3 and a protective layer 1-2 on the phase adjustment layer 1-4.

[0017] A laser projection chip with a speckle suppression function comprises any one of the above-mentioned laser reflectors with a speckle suppression function.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) Since a multi-layer functional structure is directly arranged on the surface of the mirror body, voltages of different strengths are applied between the upper electrode layer 1-3 and the lower electrode layer 1-5, and a controlled electric field is formed in the space within the upper and lower surfaces of the phase-modulating layer 1-4, resulting in random changes in the phase of the reflected light and the destruction of the temporal coherence of the reflected light. The functions of beam projection and speckle suppression are realized on the same device, which has a high degree of integration and is easy to use in occasions with high requirements on volume and power consumption.

[0020] (2) Since the multi-layer functional structure for speckle suppression is directly integrated on the mirror body 1-1, the subsequent assembly process is avoided, which is beneficial to improving the consistency of the overall system and reducing the manufacturing difficulty;

[0021] (3) Since the upper and lower electrode layers are both transparent conductive films or planar mesh structures composed of nanowires, and the orientation adjustment layer is a graphic array structure, the key functions have low overall manufacturing difficulty and high reliability.

[0022] (4) By applying voltages of different strengths to the upper and lower electrode layers, the parameter changes of the phase modulation unit of the phase modulation layer in the speckle suppression structure can be controlled, so that the same chip can achieve the speckle suppression function in a variety of scenarios.

[0023] In summary, the present invention does not require additional speckle suppression devices. By setting a corresponding functional layer on the surface of the mirror body 1-1, the dual functions of single-chip laser projection and speckle suppression are achieved. The structure is very compact and small in size, and it is easy to use in miniaturized three-dimensional imaging equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a cross-sectional structural diagram of the present invention

[0025] Figure 2 This is the projection working principle diagram of the present invention

[0026] Figure 3 It is a schematic diagram of a device structure in which a phase modulation layer is composed of an array of two types of units and an upper and lower electrode layers are two groups of electrodes.

[0027] Figure 4 It is a schematic diagram of the technical route of the second method for producing the phase modulation layer.

[0028] Figure 5 Schematic diagram of the principle of achieving structural modification of the phase modulation layer by proximity exposure.

[0029] Figure 6 Schematic diagram of the principle of achieving structural modification of the phase modulation layer by projection exposure. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0031] like Figure 1 As shown, a laser reflector with speckle suppression function includes a mirror body 1-1, and a multi-layer functional structure is arranged on the surface of the mirror body 1-1, which includes, from bottom to top, a high-reflection composite film 1-6, a lower electrode layer 1-5, a phase-adjusting layer 1-4, an upper electrode layer 1-3 and a protective layer 1-2; voltages of different strengths can be applied between the upper electrode layer 1-3 and the lower electrode layer 1-5, and a controlled electric field is formed in the space within the upper and lower surfaces of the phase-adjusting layer 1-4.

[0032] The protective layer 1-2 is a single layer or a multi-layer combination of silicon oxide, silicon nitride, amorphous silicon, or PDMS, PMMA or a high temperature resistant adhesive material.

[0033] The high-reflective composite films 1-6 are single-layer or multi-layer silicon oxide, silicon nitride, titanium oxide, hafnium oxide, zirconium oxide, zinc sulfide, zinc telluride, etc. or composite materials of the above materials; each layer of material is alternately or sequentially stacked.

[0034] The upper electrode layer 1-3 and the lower electrode layer 1-5 are one or more groups of electrodes. Figure 3As shown, the upper electrode layer 1-3 and the lower electrode layer 1-5 are two groups of electrodes, each group of electrodes is a planar mesh structure composed of transparent conductive films or nanowires. The role of transparency is that when the reflector is working, incident light waves of a specific wavelength can pass through, and the transmittance should be higher than 50%; such a mesh structure can also keep the incident light at a high transmittance. When there are multiple groups of electrodes, an insulating layer is set between each group of electrodes to insulate each other. Each group of electrodes is arranged according to a set pattern, such as a strip array, a unidirectional array or a bidirectional array. In the bidirectional array setting, the shape of each unit in the array is circular, square, elliptical, triangular or other irregular shapes.

[0035] When an electrical signal is applied between the upper electrode layer 1-3 and the lower electrode layer 1-5, one or more groups of electrodes are selected at the same time, or one or more groups of electrodes are randomly selected at different times to enhance the randomness of the time series and spatial series of the light field, and reduce the coherence by phase superposition of the time series and (or) spatial series, thereby effectively suppressing speckle.

[0036] The material of the phase adjustment layer 1-4 is a single layer or a multilayer electro-optical effect material whose refractive index can change with an external electric field, such as the Bubble Kerr effect or the Kerr effect. Within the plane of the reflector; the phase adjustment layer 1-4 is a patterned array, and the array includes at least two or more units, such as Figure 3 As shown, the phase-modulation layer 1-4 is an array composed of two types of units, each unit responds differently to the same electrical excitation. According to the unit characteristics of the phase-modulation layer 1-4, the unit of the phase-modulation layer 1-4, together with the area of ​​other functional layers above and below the phase-modulation layer 1-4 that overlaps with the unit area, can be used together as a reflection unit of the reflector, that is, the array of the phase-modulation layer 1-4 divides the reflector into different reflection units.

[0037] The materials of each unit of the phase-modulating layer are different, and the phase delay generated after the reflected light wave is different; or although the materials are the same, the material of each unit area needs to respond differently to the same electrical excitation after processing.

[0038] There are two technical routes for manufacturing the phase modulation layers 1-4.

[0039] The first technical route:

[0040] After the lower electrode layer 1-5 is manufactured, one or more layers of electro-optical material film are deposited on the upper surface of the lower electrode 1-5, and then the deposited film is structurally modified by laser, and the refractive index of the part illuminated by light is changed, thereby realizing an arrayed phase modulation layer.

[0041] The method of adjusting the refractive index of materials by light irradiation is as described in the literature (Femtosecond laser-induced refractive index modification in multicomponent glasses. VRBhardwaj et al). The laser structural modification of the phase-modulating layer film is achieved by contact / proximity exposure or projection exposure, both of which can realize the illumination of specific areas of the target surface, that is, partially selected areas are illuminated, and the rest are not illuminated, that is, the structural modification is achieved. Contact and proximity exposure are used for larger unit scales (above 1um), and projection exposure is used for smaller unit scales (below 1um). The projection exposure technology is as described in the literature (lithography imaging system and projection exposure method thereof CN106933043A, optical projection lithography machine CN102944985A). Figure 5 The figure shows a schematic diagram of a method for adjusting the refractive index of a phase modulation layer material by using contact / proximity exposure; Figure 6 Schematic diagram of a method for adjusting the refractive index of a phase modulation layer material using projection exposure.

[0042] The second technical route:

[0043] like Figure 4 As shown, after the lower electrode layer 1-5 is manufactured, a first phase-modulating layer material is deposited on the upper surface of the lower electrode 1-5, and then the first phase-modulating layer material film is patterned; then a second phase-modulating layer material is deposited, patterned by photolithography, excess second phase-modulating layer material is removed, and surface protrusions are removed by polishing, and so on. If there are multiple film layers, the above process is repeated so that each unit in the patterned array responds differently to the same electrical excitation, and finally an upper electrode layer 1-3 and a protective layer 1-2 are manufactured on the phase-modulating layer 1-4 material.

[0044] The present invention also includes a laser projection chip with a speckle suppression function, including any one of the above-mentioned laser reflectors with a speckle suppression function. For example, the above-mentioned laser reflector with a speckle suppression function is connected to a supporting frame via a rotating shaft, and the rotating shaft is one group or two groups. When the rotating shaft is one group, the two sides of the reflector are directly connected to the supporting frame via the rotating shaft; when the rotating shaft is two groups, it also includes a moving frame. After the two sides of the reflector are connected to the moving frame via the rotating shaft, the two sides of the moving frame are respectively connected to the supporting frame via the rotating shaft.

[0045] The working principle of the present invention is:

[0046] like Figure 2As shown, the laser beam is incident on the surface of the reflector, passes through the protective layer 1-2, the upper electrode layer 1-3, the phase adjustment layer 1-4, and the lower electrode layer 1-5 in sequence, reaches the high-reflection composite film 1-6 and is reflected, and then passes through the lower electrode layer 1-5, the phase adjustment layer 1-4, the upper electrode layer 1-2, the protective layer 1-2 again and exits.

[0047] A voltage is applied between the upper electrode layer 1-3 and the lower electrode layer 1-5, so that a controlled electric field is formed in the space within the upper and lower surfaces of the phase modulation layer 1-4, and the intensity of the electric field is controlled by the applied voltage. When the applied voltage is set to a random signal, the refractive index of the phase modulation layer 1-4 changes randomly, resulting in a random change in the phase of the reflected light, and the temporal coherence of the reflected light is destroyed, so that the speckle on the target surface of the laser projection is suppressed.

[0048] At the same time, the mirror body 1-1 is arranged at a certain position away from the focus in the optical path, and the light spot at a certain point projected on the target surface comes from the superposition of multiple reflection units of the reflector. Since the phases of different reflection units are different, multiple phases are superimposed, thereby suppressing the speckle at this point, that is, the purpose of suppressing speckle by destroying the spatial coherence of the projected light field is achieved at the same time.

[0049] When applying an electrical signal, several groups of electrodes can be randomly selected, including selecting one or more groups at the same time, and randomly selecting one or more groups at different times, which further enhances the phase superposition of the time series and spatial series of the light field and further suppresses speckle.

[0050] In specific applications, different modes such as periodic signal and random gate electrode, periodic signal and fixed gate electrode, random signal and fixed gate electrode or random signal and random gate electrode can be selected according to actual needs.

[0051] like Figure 3 For example, the phase-adjusting layer 1-4 has two units 1-4A and 1-4B, the upper electrode has two groups 1-3A and 1-3B, and the lower electrode has two groups 1-5A and 1-5B. In operation, 1-3A and 1-5A, or 1-3B and 1-5B, or 1-3A, 1-3B and 1-5A, 1-5B can be selected according to the setting method. When different electrodes are selected, the phase-adjusting layer units between the corresponding electrodes are adjusted, and the refractive index of the phase-adjusting layer units between the electrodes that are not selected remains unchanged.

[0052] In summary, the speckle suppression function involved in the present invention is to change the phase of the light wave by changing the refractive index of different units of the phase modulation layer 1-4 under electric field excitation, and to achieve spatial coherence destruction by phase superposition of multiple units and time series superposition. There is no macroscopic or microscopic structural movement or structural deformation. At the same time, all functional layers are planar structures, and do not involve structures such as nanostructured phase units such as microcolumns and microholes. From the perspective of working principle, the nanostructured phase unit realizes phase modulation through the interaction between light waves and three-dimensional nanostructures, which is different from the phase modulation principle in the present invention; the light wave phase modulation in the present invention relies on the control of the material property of the refractive index of the phase modulation layer material, and does not rely on a specific two-dimensional or three-dimensional structure.

Claims

1. A laser projection chip with a speckle suppression function, comprising a reflector, the reflector comprising a mirror body (1-1), characterized in that: A multi-layer functional structure is arranged on the mirror body (1-1), which, from bottom to top, comprises a high-reflection composite film (1-6), a lower electrode layer (1-5), a phase-adjusting layer (1-4), an upper electrode layer (1-3) and a protective layer (1-2); voltages of different strengths can be applied between the upper electrode layer (1-3) and the lower electrode layer (1-5), so that a controlled electric field is formed in the space within the upper and lower surfaces of the phase-adjusting layer (1-4).

2. The laser reflector with speckle suppression function according to claim 1, characterized in that: The upper electrode layer (1-3) and the lower electrode layer (1-5) are one or more groups of electrodes, each group of electrodes is a planar mesh structure composed of transparent conductive films or nanowires, and when there are multiple groups of electrodes, an insulating layer is arranged between each group of electrodes to insulate each other.

3. The laser reflector with speckle suppression function according to claim 2, characterized in that: When an electrical signal is applied between the upper electrode layer (1-3) and the lower electrode layer (1-5), one or more groups of electrodes are simultaneously selected, or one or more groups of electrodes are randomly selected at different times, so as to enhance the randomness of the time sequence and space sequence of the light field, reduce the coherence by the phase superposition of the time sequence and / or space sequence, and effectively suppress the speckle.

4. The laser reflector with speckle suppression function according to claim 1, characterized in that: The material of the orientation adjustment layer (1-4) is a single layer or multiple layers of electro-optical material film whose refractive index can change with an external electric field. The phase adjustment layer (1-4) is a patterned array, which includes at least two or more units, and each unit responds differently to the same electrical excitation.

5. The laser reflector with speckle suppression function according to claim 4, characterized in that: The method for manufacturing the phase-adjusting layer (1-4) is as follows: depositing one or more layers of electro-optical material thin films on the surface of the lower electrode (1-5), and then using laser to structurally modify the deposited thin films, so that the refractive index of the part illuminated by the laser light changes, thereby realizing an arrayed phase-adjusting layer.

6. The laser reflector with speckle suppression function according to claim 4, characterized in that: The method for manufacturing the phase adjustment layer (1-4) is as follows: depositing a first phase adjustment layer material on the surface of a lower electrode (1-5), then patterning the first phase adjustment layer material film; then depositing a second phase adjustment layer material, patterning it by photolithography, removing excess second phase adjustment layer material, and so on, repeating the above process for multiple film layers, so that each unit in the patterned array responds differently to the same electrical excitation, and finally manufacturing an upper electrode layer (1-3) and a protective layer (1-2) on the phase adjustment layer (1-4).

7. The laser reflector with speckle suppression function according to claim 1, characterized in that: The materials of each unit of the phase modulation layer are different; or although they are the same material, the material of each unit area responds differently to the same electrical excitation after being processed.

8. The laser reflector with speckle suppression function according to claim 1, characterized in that: The protective layer (1-2) is a single layer or a multi-layer combination of silicon oxide, silicon nitride, amorphous silicon, or PDMS, PMMA or a high temperature resistant adhesive material.

9. The laser reflector with speckle suppression function according to claim 1, characterized in that: The high-reflection composite film (1-6) is a single layer or multiple layers of silicon oxide, silicon nitride, titanium oxide, hafnium oxide, zirconium oxide, zinc sulfide, zinc telluride or a composite material of the above materials; each layer of material is alternately or sequentially stacked.

10. A laser projection chip with speckle suppression function, comprising a laser reflection mirror with speckle suppression function as claimed in any of the above claims.

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