WO2022170669A1

WO2022170669A1 - Micro led color uniformity detection system

Info

Publication number: WO2022170669A1
Application number: PCT/CN2021/082851
Authority: WO
Inventors: 李念念; 洪志坤; 王锦; 郑增强; 欧昌东; 夏珉
Original assignee: 武汉精测电子集团股份有限公司; 武汉精立电子技术有限公司
Priority date: 2021-02-10
Filing date: 2021-03-24
Publication date: 2022-08-18
Also published as: CN112798234B; CN112798234A

Abstract

Disclosed in the present invention is a Micro LED color uniformity detection system, comprising a microlens array, a metasurface microlens array, and a detector element which are sequentially provided in an optical path direction of a Micro LED light source to be detected. The side of the microlens array close to the Micro LED light source is provided with a plurality of microlenses periodically arranged at intervals and having one-to-one correspondence to light-emitting units in the Micro LED light source, and each microlens modulates divergent light output by one light-emitting unit in the Micro LED light source into parallel light. The side of the metasurface microlens array away from the microlens array is provided with a plurality of metasurface structures periodically arranged at intervals and having one-to-one correspondence to the microlenses in the microlens array, which are used for separately projecting parallel light output by each microlens to different areas on a detection area array of the detector element. In the present invention, light of different chip units is sufficiently separated and focused on different positions of a photoelectric detector, such that the wavelength characteristics of each Micro LED chip unit can be independently detected, the advantage of high resolution is achieved, and the detection precision is improved.

Description

A Micro LED Color Uniformity Detection System

【Technical field】

The invention belongs to the technical field of equipment detection, and more particularly, relates to a Micro LED color uniformity detection system based on a metasurface microlens array.

【Background technique】

Micro LED technology is an LED miniaturization matrix technology. Compared with LCD and OLED, Micro LED has significant advantages in brightness, efficiency, resolution, reliability and response speed. After the mass transfer, in order to improve and ensure the yield of Micro LED displays, inspection technology will be an indispensable key step in the manufacturing process. The detection of ordinary LED mainly includes: emission wavelength, brightness, color uniformity, etc.

Due to the high chip integration of Micro LED, its size is less than 50μm, and the interval between two adjacent Micro LED chip units is only a few microns, so the light emitted by each chip unit will intersect with the light emitted by surrounding chip units. If the traditional spectrometer is used for detection, it is impossible to distinguish which chip unit the received signal is sent by, resulting in great errors in the detection results and low detection accuracy. Therefore, the vast majority of traditional LED detection technologies are no longer suitable for Micro LED detection. It is necessary to develop a real-time, fast, high-resolution and accurate detection technology to meet the current detection requirements of Micro LED chips.

[Content of the invention]

In view of at least one defect or improvement requirement of the prior art, the present invention provides a Micro LED color uniformity detection system, the purpose of which is to solve the problem that the resolution of traditional LED detection technology is low and cannot be applied to the detection of Micro LED.

In order to achieve the above purpose, according to one aspect of the present invention, a Micro LED color uniformity detection system is provided, comprising a microlens array, a metasurface microlens array and a detection system that are sequentially arranged along the optical path direction of the Micro LED light source to be detected. device;

The micro-lens array is provided with a plurality of micro-lenses arranged at periodic intervals and corresponding to the light-emitting units in the Micro LED light source on one side close to the Micro LED light source, and each of the micro-lenses is used to connect the Micro LED light source. The divergent light output by one of the light-emitting units is modulated into parallel light;

The metasurface microlens array is provided with a plurality of metasurface structures that are periodically spaced and corresponding to the microlenses in the microlens array on the side away from the microlens array, and are used to convert all the output values of each microlens. The parallel light is separately projected on different areas on the detection area array of the detection device.

Preferably, in the above-mentioned Micro LED color uniformity detection system, each metasurface structure in the metasurface microlens array is also used to disperse the parallel light output by the microlens, and output three primary colors of R, G, and B light. and project them separately at different positions in the same area of the detection area array;

Each of the metasurface structures includes three sub-wavelength columns with different sizes, and each of the sub-wavelength columns is used to selectively output one of the RGB monochromatic lights through phase modulation.

Preferably, the above-mentioned Micro LED color uniformity detection system,

The size of each of the subwavelength columns satisfies that the modulation phase for monochromatic light is 2π;

The arrangement of the subwavelength columns outputting monochromatic light of different colors is the same as the arrangement of the pixels in the detection device.

Preferably, in the above-mentioned Micro LED color uniformity detection system, the height of the sub-wavelength column is determined by the maximum wavelength of the detected wavelength band, the refractive index of air and the refractive index of the column material.

Preferably, in the above-mentioned Micro LED color uniformity detection system, the subwavelength columns in each of the metasurface structures are rectangular columnar structures with equal heights.

Preferably, in the above-mentioned Micro LED color uniformity detection system, each of the metasurface structures includes a subwavelength column for outputting R light, a subwavelength column for outputting B light, and two subwavelength columns for outputting G light column.

Preferably, in the above-mentioned Micro LED color uniformity detection system, the size of each of the micro-lenses is not less than the size of the beam output by a single light-emitting unit.

Preferably, in the above-mentioned Micro LED color uniformity detection system, the micro lens is a spherical crown structure protruding on the surface of the base.

Preferably, in the above-mentioned Micro LED color uniformity detection system, the distance between parallel lights projected by two adjacent light-emitting units on the detection area array of the detection device in the Micro LED light source is greater than one pixel;

In the Micro LED light source, the distance between different monochromatic lights projected by the same light-emitting unit on the detection area array of the detection device is greater than one pixel.

Preferably, the above-mentioned Micro LED color uniformity detection system further includes a controller;

The controller is electrically connected to the detection device, acquires parallel light or monochromatic light gathered on the detection area array of the detection device by each light-emitting unit in the Micro LED light source, and performs brightness detection and comparison to realize the color of the Micro LED light source Uniformity testing.

In general, compared with the prior art, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

(1) The Micro LED color uniformity detection system provided by the present invention adopts the micro lens array to modulate the divergent light emitted by each chip unit of the Micro LED light source into parallel light, and then separately projects the incident parallel light through the metasurface micro lens array In different areas on the detection area array of the detection device, the light of different chip units can be sufficiently separated and focused on different positions of the photodetector, so that the luminous intensity of each Micro LED chip unit can be detected, avoiding phase The light emitted by adjacent chip units overlaps each other; by comparing the luminous intensity of each Micro LED chip unit, the detection of the brightness uniformity of the Micro LED is finally realized, which has the advantage of high resolution and improves the detection accuracy.

(2) In the Micro LED color uniformity detection system provided by the present invention, each metasurface structure in the metasurface microlens array includes three subwavelength columns with different sizes, and each subwavelength column is used to select through phase modulation It is one of the RGB monochromatic lights that can output RGB monochromatic light, and its size satisfies the modulation phase of monochromatic light to be 2π; due to the different incident wavelengths of each color light in the incident parallel light, the output phases after modulation by different sub-wavelength columns are also different. Finally, the monochromatic light of different colors is focused on different positions of the photodetector, and the respective brightness and chromaticity of the different monochromatic light components contained in the light emitted by each Micro LED chip unit can be further detected. The wavelength characteristics of the LED chip unit finally realize the detection of the color uniformity of the Micro LED.

【Description of drawings】

1 is a schematic structural diagram of a Micro LED color uniformity detection system provided by an embodiment of the present invention;

2 is a schematic diagram of an optical path of a Micro LED color uniformity detection system provided by an embodiment of the present invention;

3 is a schematic diagram of a microlens array fabricated by a photoresist hot-melt molding method according to an embodiment of the present invention;

4 is a schematic diagram of the structural matching relationship of the Micro LED array, the microlens array, the metasurface microlens array, and the photodetector area array provided by an embodiment of the present invention;

5 is a schematic diagram of structural parameters of a phase modulation function provided by an embodiment of the present invention;

6 is a diagram of the dispersion distribution of light emitted by two adjacent light-emitting units in the Micro LED light source provided by the embodiment of the present invention on a 5*5 photodetector area array after passing through the system;

In all drawings, the same reference numerals denote the same technical features, specifically: 100-Micro LED light source, 101-light-emitting unit; 200-microlens array, 201-microlens, 202-substrate, 203-light Resist, 204-mask; 300-metasurface microlens array, 301-subwavelength column; 400-photodetector, 401-detection area array; 500-external power supply; 600-host computer.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

The traditional LED test is divided into photoluminescence test (PL) and electroluminescence test (EL). The former is detected by ultraviolet photoluminescence. The advantage is that the LED chip can be tested without damage and contact with the LED chip. For testing, generally only Micro LEDs with a chip size of 50 μm or more can be detected; the latter is detected by lighting. Although the chip may be damaged due to electrical contact, the detection accuracy is below 50 μm. As a specific example , In this embodiment, the Micro LED is detected by electroluminescence.

1 is a schematic diagram of the structure and composition of a Micro LED color uniformity detection system provided in this embodiment, including a microlens array 200, a metasurface microlens array 300 and a microlens array 200, a metasurface microlens array 300 and photodetector 400;

In this embodiment, the external power supply 500 is used to supply power to the Micro LED, and the lit Micro LED is the Micro LED light source 100 .

During the test, the Micro LED light source 100, the microlens array 200, the metasurface microlens array 300 and the photodetector 400 are respectively fixed by the carrier; in this example, a vacuum is used between the Micro LED light source 100 and the carrier Adsorption can ensure that the Micro LED light source 100 remains stable on the carrier, and the external power supply 500 must maintain voltage stability. The microlens array 200, the metasurface microlens array 300 and the photodetector 400 are all on the same axis, wherein the carriers of the microlens array 200 and the metasurface microlens array 300 are all clamped carriers, and the photodetector 400 is composed of It is composed of a CMOS industrial camera and a bi-telecentric lens, and a clamp-type carrier is also used to fix the photodetector 400 .

FIG. 2 is a schematic diagram of the optical path of the Micro LED color uniformity detection system provided in this embodiment. Referring to FIG. 2 , the microlens array 200 is mainly used to modulate the divergent light output by the Micro LED light source 100 into parallel light, which is close to the Micro LED light source. One side of the 100 is provided with a plurality of microlenses 201 that are periodically spaced and corresponding to the light emitting units 101 (ie, the Micro LED chips) in the Micro LED light source 100 one-to-one.

As an optional embodiment, the microlens array 200 includes a transparent substrate and a plurality of microlenses 201 protruding on the surface of the transparent substrate. The transparent substrate is used for transmitting the divergent light emitted by the Micro LED light source 100 and supporting a large number of microlenses 201. Each microlens 201 is used to modulate the divergent light output by a light-emitting unit 101 in the Micro LED light source 100 into parallel light. The beam size output by a single light-emitting unit 101. In the case of satisfying the above-mentioned dimensions, the shape of the microlens 201 is not specifically limited, and can be spherical, cuboid or other relatively regular shapes; for the consideration of the manufacturing process, in order to make the microlens array 200 easier to manufacture, this embodiment In an example, the microlenses 201 on the microlens array 200 are spherical crown structures protruding from the surface of the transparent substrate.

In a specific example, a common photoresist hot-melt molding method is used to fabricate the microlens array 200. The fabrication principle is shown in FIG. 3. First, a certain thickness of photoresist 203 is coated on the substrate 202, and then the UV exposure is performed under the mask 204 of the circular array, and after development, the photoresist structure of the cylindrical array is obtained, and the photoresist is heated to a molten state, and the surface tension transforms the cylindrical structure into a spherical crown structure, and finally the required preparation is obtained. The microlens array 200.

The side of the meta-surface micro-lens array 300 away from the micro-lens array 200 is provided with a plurality of meta-surface structures that are periodically spaced and corresponding to the light-emitting units 101 in the Micro LED light source 100. At the same time, on the meta-surface micro-lens array 300 The plurality of metasurface structures also have a one-to-one correspondence with the microlenses 201 in the microlens array 200, and the metasurface structures are subwavelength columns 301 whose side lengths are in the subwavelength order, and are used to output each microlens 201. The parallel light is projected separately into different areas on the detection area array 401 of the photodetector 400 .

The distance between the parallel lights projected on the detection area array 401 of the photodetector 400 by two adjacent light-emitting units 101 in the Micro LED light source 100 is greater than one pixel, so as to satisfy the minimum resolution of the photodetector 400 .

In this embodiment, the micro-lens array 200 is used to modulate the divergent light emitted by each light-emitting unit 101 of the Micro LED light source 100 into parallel light, and then the parallel light output by each micro-lens is separately projected by the metasurface micro-lens array 300 on the photodetector. Therefore, the light of different light-emitting units 101 can be sufficiently separated and focused on different positions of the photodetector 400, so that the light-emitting intensity of each Micro LED chip unit can be detected, By comparing the luminous intensity of each Micro LED chip unit, the detection of the brightness uniformity of the Micro LED is finally realized.

Further, in order to realize the detection of the color uniformity of the Micro LED, the structure of the metasurface microlens array 300 is optimized in this embodiment to achieve the effect of dispersion and light separation.

FIG. 4 is a schematic diagram of the structure matching relationship between the Micro LED array, the microlens array, the metasurface microlens array and the photodetector area array provided in this implementation. As shown in FIG. 4 , each metasurface structure in the metasurface microlens array 300 is shown in FIG. 4 . Each includes three sub-wavelength columns 301 with different sizes, and each sub-wavelength column 301 is used to selectively output one of RGB monochromatic lights through phase modulation, and the rows of sub-wavelength columns 301 that output monochromatic light of different colors. The arrangement is the same as the arrangement of pixels of the industrial camera detection area array 401 in the photodetector 400 .

As a specific example, the metasurface microlens array 300 includes a transparent substrate and a plurality of metasurface structures arranged at intervals on the surface of the transparent substrate, and the metasurface structures are periodically arranged according to the array structure of the light emitting units 101 in the Micro LED light source 100; The transparent substrate is used for transmitting the parallel light output by the microlens array 200 and supporting the metasurface structure. Among them, each metasurface structure is composed of three subwavelength columns 301 with different sizes arranged according to a certain period, and the arrangement method depends on the pixel point arrangement of the industrial camera detection area array 401 in the photodetector 400; The subwavelength columns 301 of each size selectively output one of the R, G, and B monochromatic lights through phase modulation, that is, each metasurface structure can disperse the parallel light corresponding to one light-emitting unit 101 to form R, G , B three primary color light.

In each metasurface structure, the heights of the subwavelength pillars 301 are all the same and are in the order of the detected wavelength, and only the length and width are used as variables, and the side lengths of the subwavelength pillars 301 are in the subwavelength order; in a specific example Among them, the material of the sub-wavelength column 301 is any one of silicon nitride, silicon dioxide, and amorphous silicon; the shape of the sub-wavelength column 301 is not specifically limited, because the light-emitting unit 101 in the Micro LED light source 100 and the photodetector The shapes of the pixels of the industrial camera detection area array 401 in the detector 400 are all rectangles. In order to better match the shape to improve the utilization rate of light, the subwavelength column 301 in this embodiment preferably adopts a rectangular columnar structure; the transparent base material It is silicon dioxide, and its structure also adopts a rectangular columnar structure.

The height of the sub-wavelength column 301 is jointly determined by the maximum wavelength of the detected wavelength band, the refractive index of air and the refractive index of the column material. In a specific example, the height h of the sub-wavelength column 301 satisfies:

In the above formula: n _s is the refractive index of silicon dioxide, which is taken as 3.41; n _i is the refractive index of air, which is taken as 1; the minimum height of the sub-wavelength column is determined by the maximum wavelength of the light wave λ=633nm, so the value of h is 263nm.

Since the transmittance of the sub-wavelength column 301 is related to its own size, in the case of a fixed height, by changing the length and width of the sub-wavelength column 301, three sub-wavelength columns 301 with different sizes are designed, respectively for the RGB three-color light. The band has a higher transmittance. By periodically arranging three rectangular columnar structures of different sizes, the monochromatic light output by the same microlens 201 in the microlens array 200 will generate different phases through the subwavelength columns 301 of different sizes in a metasurface structure. The phase modulation formula of the subwavelength column 301 is:

In the above formula,

represents the phase of the monochromatic light output by each subwavelength column, that is, the output phase of the monochromatic light; λ _d is the incident wavelength; focal length f is the distance from the focal point F to the center O of the metasurface; r _p is any point on the metasurface The distance from B to the center O of the metasurface, that is, r _p =OB; θ _f is the angle between the focal length f and the z-axis;

is the counterclockwise rotation angle of AO relative to the positive direction of the x-axis;

is the counterclockwise rotation angle of BO relative to the positive direction of the x-axis, and its three-dimensional schematic diagram is shown in Figure 5.

In this embodiment, the size of each sub-wavelength column 301 satisfies the modulation phase of monochromatic light to be 2π. Since the incident wavelength of each color light in the incident parallel light is different, modulation is performed by different sub-wavelength columns 301 with a modulation phase of 2π. Then, the phases of the outputs are also different, so as to achieve the effect of dispersive light splitting; since the modulation phases of the three sub-wavelength columns 301 in each metasurface structure are all 2π, the sub-wavelength columns 301 have a focusing effect, and finally the single-wavelength columns 301 of different colors The colored light is focused on different positions of the detection area array 401 of the photodetector 400 .

The distance between adjacent monochromatic lights projected by the same light-emitting unit 101 on the detection area array 401 of the photodetector 400 in the Micro LED light source 100 is greater than one pixel, so as to satisfy the minimum resolution of the photodetector 400 .

In addition, in order to match the pixel point arrangement of the industrial camera detection area array 401 in the photodetector 400, in this embodiment, each metasurface structure includes a subwavelength column 301 that outputs R light, and a subwavelength column 301 that outputs B light. The sub-wavelength columns 301 for light, and the two sub-wavelength columns 301 for outputting G light; the four sub-wavelength columns 301 are arranged in the manner of RGGB/BGGR. In one of the metasurface structures, the parameters of the four subwavelength pillars 301 are as follows: f = 25 μm, θ _f = 8°,

In this embodiment, the scattered light output by each Micro LED is decomposed into three primary colors of RGB through the metasurface microlens array 300, and the respective luminance colors of different monochromatic light components contained in the light emitted by each Micro LED chip unit can be further detected. By comparing the wavelength characteristics of each Micro LED chip unit, the detection of the color uniformity of Micro LED is finally realized.

As an optional embodiment, the above-mentioned Micro LED color uniformity detection system further includes a host computer 600; the host computer 600 is electrically connected with the photodetector 400, and obtains that each light-emitting unit 101 in the Micro LED light source 100 is focused on the photodetector 400 detects the luminous intensity of the light spot on the area array 401, and realizes the brightness uniformity detection of the Micro LED light source 100 through brightness detection and comparison; The respective brightness and chromaticity of the RGB monochromatic lights on the area array 401 are detected, and the wavelength characteristics of each light-emitting unit 101 in the Micro LED are detected and compared, so as to realize the color uniformity detection of the Micro LED light source 100.

The Micro LED color uniformity detection system provided in this embodiment is a micron-level detection system, so the following points need to be paid attention to during the operation:

(1) It needs to be carried out in a dark room to reduce the influence of stray light;

(2) The external power supply 500 for lighting the Micro LED light source 100 needs to be relatively stable;

(3) Since the structures of the microlens array 200 and the metasurface microlens array 300 are easily damaged, they should be clamped slowly and firmly when using a carrier to prevent damage to the device.

In a specific example, the Micro LED light source 100 has a 4×4 light-emitting area array, that is, it includes 4×4 LED chip units (light-emitting units 101 ), and each Micro LED chip unit is regarded as a point light source, and its diameter is 6μm, and the spacing between two adjacent Micro LED chip units is also 6μm. In order to match this structure of the Micro LED light source 100 , in this embodiment, the microlens array 200 is also a 4×4 array structure, that is, it includes 4×4 regularly arranged microlenses 201 . The diameter of a single microlens unit is is 8 μm, and the center distance of two adjacent microlenses 201 is 12 μm.

FIG. 6 is the dispersion distribution diagram of the light emitted by the two adjacent light-emitting units 101 in the Micro LED light source 100 provided in this embodiment on the 5*5 photodetector area array after passing through the system. Referring to FIG. 6 , the detection of the photodetector 400 The single pixel parameter of the area array 401 is 2.4 μm×2.4 μm, so the detection area array 401 with a size of 12 μm×12 μm contains 5×5 pixels. The light emitted by the Micro LED light source 100 is modulated into parallel light by the microlens array 200, and the beam diameter does not exceed 8 μm, and after dispersing light by the metasurface microlens array 300, the three-color light of each Micro LED chip unit (the center wavelength is 632nm respectively) , 533nm and 430nm) focused on a 12μm×12μm photodetector area array. Since the detection area array of the photodetector 400 includes 5×5 pixels, the imaging positions of monochromatic light of different wavelengths on the detection area array can be separated by at least one pixel size, so as to satisfy the requirements of the photodetector. Minimum resolution. It can be seen from Fig. 6 that the distance between the imaging positions of different colors of monochromatic light in a single Micro LED chip unit on the detection area array is larger than the size of one pixel, and the distance between the wavelength detection positions of two adjacent Micro LED chip units is the same. It is larger than the size of one pixel, so both meet the minimum resolution of photodetection.

Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention, etc., All should be included within the protection scope of the present invention.

Claims

A Micro LED color uniformity detection system, characterized in that it comprises a micro-lens array, a meta-surface micro-lens array and a detection device sequentially arranged along the optical path direction of the Micro LED light source to be detected;

The micro-lens array is provided with a plurality of micro-lenses arranged at periodic intervals and corresponding to the light-emitting units in the Micro LED light source on one side close to the Micro LED light source, and each of the micro-lenses is used to connect the Micro LED light source. The divergent light output by one of the light-emitting units is modulated into parallel light;

The metasurface microlens array is provided with a plurality of metasurface structures that are periodically spaced and corresponding to the microlenses in the microlens array on the side away from the microlens array, and are used to convert all the output values of each microlens. The parallel light is separately projected on different areas on the detection area array of the detection device.
The Micro LED color uniformity detection system according to claim 1, wherein,

Each metasurface structure in the metasurface microlens array is also used to disperse and split the parallel light output by the microlens, output R, G, and B primary color lights and separately project them on the detection area array. different locations in the same area;

Each of the metasurface structures includes three sub-wavelength columns with different sizes, and each of the sub-wavelength columns is used to selectively output one of the RGB monochromatic lights through phase modulation.
The Micro LED color uniformity detection system according to claim 2, wherein,

The size of each of the subwavelength columns satisfies that the modulation phase for monochromatic light is 2π;

The arrangement of the subwavelength columns outputting monochromatic light of different colors is the same as the arrangement of the pixels in the detection device.
The Micro LED color uniformity detection system according to claim 3, wherein,

The height of the sub-wavelength column is determined by the maximum wavelength of the detected band, the refractive index of air and the refractive index of the column material.
The Micro LED color uniformity detection system according to claim 3, wherein,

The subwavelength columns in each of the metasurface structures are rectangular columnar structures with equal heights.
The Micro LED color uniformity detection system according to claim 2, wherein each of the metasurface structures includes a sub-wavelength column for outputting R light, a sub-wavelength column for outputting B light, and two A subwavelength column that outputs G light.
The Micro LED color uniformity detection system according to claim 1 or 2, wherein the size of each of the micro-lenses is not smaller than the size of the beam output by a single light-emitting unit.
The Micro LED color uniformity detection system according to claim 7, wherein the microlens is a spherical crown structure protruding from the surface of the substrate.
The Micro LED color uniformity detection system according to claim 2, wherein the distance between the parallel lights projected by two adjacent light-emitting units in the Micro LED light source on the detection area array of the detection device is greater than one pixel ;

In the Micro LED light source, the distance between different monochromatic lights projected by the same light-emitting unit on the detection area array of the detection device is greater than one pixel.
The Micro LED color uniformity detection system according to claim 1 or 2, further comprising a controller;

The controller is electrically connected to the detection device, acquires parallel light or monochromatic light gathered on the detection area array of the detection device by each light-emitting unit in the Micro LED light source, and performs brightness detection and comparison to realize the color of the Micro LED light source Uniformity testing.