Diffractive optical element detection system

Abstract

A diffractive optical element detection system disclosed by the present invention comprises a wafer stage, a light path module and a light source assembly, the light path module and the light source assembly are arranged above the wafer stage, the light path module is provided with different specifications and can be detached and replaced, and an image sensor and a matched lens are arranged in the light path module; the light source assembly comprises a positive light source arranged on one side of the lens and a backlight light source embedded in the upper surface of the wafer carrier. The design is novel, the selection step of the light path module is systematized, the configuration selection and equipment debugging time is shortened, the compatibility of the detection system is improved, meanwhile, the detection equipment is greatly simplified, and the chip detection accuracy is improved in cooperation with a positive light source and a negative light source of the detection equipment.

Description

Technical Field

[0001] The present invention relates to the field of optical detection technology, and in particular to a diffraction optical element detection system. Background Art

[0002] Diffractive optical elements (DOE) can decompose electromagnetic waves into different spectra. By controlling the phase of the light beam, it can achieve beam shaping functions such as focusing, beam splitting, wavefront control and three-dimensional imaging. Diffractive optical elements are widely used in optical detection, optical communication, projection systems and laser marking. In the process of producing diffractive optical elements, it is necessary to detect the appearance defects of the produced components. As the size of DOE is getting smaller and smaller, computer vision detection is currently being developed to replace the detection method of artificial naked eyes. In order to meet the detection of different DOE sizes, it is currently developed into an electromechanically controlled automatic zoom optical detection system.

[0003] This type of optical inspection system has a limited zoom range. In order to inspect components of different size ranges, it is often necessary to purchase a complete set of inspection equipment. The equipment is relatively expensive, and the electronic control equipment requires frequent maintenance, which increases the company's production and maintenance costs. Summary of the invention

[0004] The purpose of the present invention is to solve the disadvantage in the prior art that for component detection in different size ranges, it is necessary to purchase a set of detection equipment with different configurations, which increases the production and maintenance costs of the enterprise, and to propose a diffractive optical element detection system.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A diffractive optical element detection system includes a wafer stage, an optical path module and a light source assembly arranged above the wafer stage, wherein the optical path module is arranged in different specifications and is removable, and an image sensor and a matching lens are arranged in the optical path module;

[0007] The light source assembly comprises a positive light source arranged on one side of the lens and a backlight light source embedded on the upper surface of the wafer carrier.

[0008] Preferably, the optical path module is completely replaceable.

[0009] A detection method for a diffractive optical element detection system comprises the following steps:

[0010] S1. Select the appropriate optical path module and perform system calibration;

[0011] S2, place the component to be inspected on the wafer stage and keep it in the center of the field of view of the optical path module;

[0012] S3. Capture images through image sensors and perform image analysis to ensure that image accuracy meets detection requirements.

[0013] Preferably, the system calibration described in S1 comprises the following steps:

[0014] S11. According to the parameters of the optical path module, adjust the distance between the lens and the wafer stage so that the field of view and focal length meet the optimal working distance of the lens until the clearest image is obtained;

[0015] S12, adjust the light source assembly to keep the light source stable so that the light beam is evenly irradiated to the surface of the component to be inspected;

[0016] S13, using the component to be tested for testing, repeating steps S11 and S12 until the image resolution meets the requirements.

[0017] Preferably, when the image sensor is used for detection in S3, images are taken using positive light source and backlight light source conditions respectively.

[0018] Preferably, the image analysis in S3 comprises the following steps:

[0019] S31, Image preprocessing and correction: denoising, adjusting brightness and contrast, and performing geometric and color correction to ensure that the image is clear and distortion-free;

[0020] S32, region segmentation and feature extraction: extract and identify regions through edge detection and region segmentation, and identify key features of the components to be inspected;

[0021] S33, Defect detection and quality verification: Compare and analyze defects in detection images and detect component defects.

[0022] A method for selecting an optical path module in a diffractive optical element detection system comprises the following steps:

[0023] K1. Define defect size and determine defect detection requirements;

[0024] K2. Select an image sensor with appropriate resolution according to the size of the component to be inspected and the defect detection requirements;

[0025] K3. Calculate the required lens magnification and determine the lens and objective lens combination based on the sensor size and the size of the area to be measured;

[0026] K4. Calculate the optimal working distance of the lens for chip detection according to the specifications of the selected lens and objective lens;

[0027] K5. Determine the depth of field according to the detection requirements to meet the focus compensation of the size of the component to be inspected;

[0028] K6, complete the selection of the optical path module, and install the optical path module in the detection system according to the optimal working distance in K4. Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. In the present invention, the detection system, through the design of the optical path module, does not need to design a complex three-axis motion system, which greatly simplifies the detection device and reduces the design and manufacturing cost. At the same time, through the design of the positive and negative light sources, the comprehensiveness of chip defect detection is effectively improved;

[0030] 2. The optical path module selection method proposed in the present invention is based on the chip size and defect detection accuracy, combined with the lens field of view and lens cost, which greatly improves the compatibility of the detection system and ensures good adaptability to detection of any size;

[0031] 3. The present invention systematizes the selection process of the optical path module, and can quickly screen out the appropriate optical path module configuration. Compared with the traditional detection lens, it saves the installation and debugging time of the equipment and improves the overall detection work efficiency.

[0032] The present invention has a novel design and systematizes the selection steps of the optical path module, thereby shortening the time for configuration selection and equipment debugging. While improving the compatibility of the detection system, it also greatly simplifies the detection equipment and improves the accuracy of chip detection by cooperating with the positive and negative light sources of the detection equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the structure of the detection system of the present invention.

[0034] Figure 2 Schematic diagram of the depth of field range during optical module detection.

[0035] In the figure: detection platform 1, wafer carrier 2, mounting frame 3, optical path module 4, positive light source 5, backlight light source 6. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0037] Embodiment 1

[0038] Reference Figure 1 and 2 A diffractive optical element detection system includes a wafer stage 2, an optical path module 4 and a light source assembly arranged above the wafer stage 2, wherein the optical path module is arranged in different specifications and can be replaced as a whole, and an image sensor and a matching lens are arranged in the optical path module 4;

[0039] The light source assembly includes a positive light source 5 disposed on one side of the lens and a backlight light source 6 embedded on the upper surface of the wafer carrier 2 .

[0040] In this embodiment, when the chip is inspected, the chip is placed on the wafer carrier 2, that is, above the backlight light source, and the chip is illuminated by the positive light source 5 above the chip and the backlight light source 6 below the chip respectively, and the chip is imaged and inspected in cooperation with the optical path module 4. The imaging quality is improved by the illumination of positive and negative light sources, and the comprehensiveness of chip defect detection is improved to ensure the ability to detect chip defects.

[0041] Embodiment 2

[0042] A detection method for a diffractive optical element detection system comprises the following steps:

[0043] S1, select a suitable optical path module 4 and perform system calibration;

[0044] S11, according to the parameters of the optical path module 4, adjust the distance between the lens and the wafer stage so that the viewing angle and focal length meet the optimal working distance of the lens until the clearest image is obtained;

[0045] S12, adjust the light source assembly to keep the light source stable so that the light beam is evenly irradiated to the surface of the component to be inspected;

[0046] S13, using the component to be tested for testing, repeating steps S11 and S12 until the image resolution meets the requirements.

[0047] S2, placing the component to be inspected on the wafer stage 2 and keeping it in the center of the field of view of the optical path module 4;

[0048] S3. Capture an image through an image sensor, and respectively use a positive light source 5 and a backlight light source 6 to capture an image, and then perform image analysis to ensure that the image accuracy meets the detection requirements.

[0049] The image analysis includes the following steps:

[0050] S31, Image preprocessing and correction: denoising, adjusting brightness and contrast, and performing geometric and color correction to ensure that the image is clear and distortion-free;

[0051] S32, region segmentation and feature extraction: extract and identify regions through edge detection and region segmentation, and identify key features of the components to be inspected;

[0052] S33, Defect detection and quality verification: Compare and analyze defects in detection images and detect component defects.

[0053] In this embodiment, the component to be inspected is illuminated by the positive light source 5 and the backlight light source 6 and imaged in cooperation with the optical path module 4, and the imaged pattern is analyzed to identify key features of the component to be inspected to detect component defects. By separately sampling, analyzing and comparing chip images under the positive light source 5 and the backlight light source 6, the defect detection rate can be greatly improved, and the detection capability and reliability of the detection results can be improved.

[0054] Embodiment 3

[0055] A method for selecting an optical path module in a diffractive optical element detection system comprises the following steps:

[0056] K1. Define defect size and determine defect detection requirements;

[0057] K2. Select an image sensor with appropriate resolution according to the size of the component to be inspected and the defect detection requirements;

[0058] K3. Calculate the required lens magnification and determine the lens and objective lens combination based on the sensor size and the size of the area to be measured;

[0059] K4. Calculate the optimal working distance of the lens for chip detection according to the specifications of the selected lens and objective lens;

[0060] K5. Determine the depth of field according to the detection requirements to meet the focus compensation of the size of the component to be inspected;

[0061] K6. Complete the selection of the optical path module and install the optical path module in the detection system according to the optimal working distance in K4.

[0062] Based on the above optical path module selection method, the selection process of the optical path module is illustrated as an example. For the selection of optical path modules with two chip sizes of 4×4mm and 7×7mm, the steps are as follows:

[0063] Step 1: First, define the defect. In the industry, the defect size is generally defined as occupying 10 pixels. In the present invention, in order to show the excellent detection effect of the lens module, the defect size is defined as occupying 2.5-4 pixels.

[0064] Step 2: Determine the resolution of the image sensor. The minimum defect detection size is 10μm. To ensure that the defect occupies at least 2.5-4 pixels, the resolution requirement should be less than 4μm per pixel. The pixel size of a 5-megapixel image sensor is 3.45μm, and the pixel size of a 20-megapixel image sensor is 2.4μm, both of which meet the resolution requirement.

[0065] Step 3: Calculate the lens magnification. The sensor size is 10×10mm (i.e., a standard 1-inch sensor). Based on the chip size and sensor size, the calculation method is as follows:

[0066] 4×4mm chip:

[0067] Considering the cost, 5 megapixels can meet the resolution requirement, so a 5 megapixel image sensor is selected. In order for the field of view to cover a 4×4mm area, the sensor size is 10×10mm, and the required magnification is:

[0068]

[0069] That is, a magnification of 2.5 times or less can meet the detection requirements. However, the number of pixels in the XY direction of a common 5-megapixel lens is 2440×2044 (i.e., resolution), and the common pixel size is 3.45μm. The following formula is used to calculate the lens field of view at different magnifications:

[0070]

[0071] For example, the X-direction field of view of a 2.5x lens is:

[0072]

[0073] The fields of view in the XY direction at 2.5x, 2x, and 1.5x lens magnifications are calculated as follows:

[0074] 2.5 times field of view X = 3.367mm; 2.5 times field of view Y = 2.817mm;

[0075] 2x field of view X=4.209mm; 2x field of view Y=3.521mm;

[0076] 1.5 times the field of view X=5.612mm; 1.5 times the field of view Y=4.694mm.

[0077] It can be seen that when selecting a 2.5x or 2x lens magnification, for a 4×4mm chip, the field of view in the Y direction is smaller than the chip size and cannot meet the chip detection requirements, while the field of view of a 1.5x lens can meet the detection requirements of a 4×4mm chip and slightly exceeds the chip size, leaving a tolerance for chip placement accuracy, reducing the difficulty of chip placement. At this time, the detection accuracy is 3.45μm / 1.5x=2.3μm, ensuring good detection accuracy. Therefore, a 5-megapixel image sensor and a 1.5x lens are the best choices for a 4×4mm chip. Obviously, under the same detection accuracy standard, this lens can also be used to detect chips within 4×4mm, such as chips from 1×1mm to 4×4mm.

[0078] 7×7mm chip:

[0079] For a 20-megapixel image sensor, the number of pixels in the XY direction is usually 3000, the pixel size is 2.4μm, and the XY lens field of view at 1x magnification is:

[0080]

[0081] The size is slightly larger than the 7×7mm chip, leaving a chip placement tolerance. For image sensors with less than 20 million pixels, the image sensor cannot completely accommodate the chip at 1x magnification, so it cannot meet the detection requirements. The 20 million pixel image sensor and 1x lens are the best choice for 7×7mm chips. Obviously, under the same detection accuracy standard, this lens can also be used for the detection of chips within 7×7mm, such as 4×4mm to 7×7mm chips. As for chips smaller than 4×4mm, for cost considerations, the aforementioned 5 million pixel image sensor and 1.5x lens can be selected.

[0082] Step 4: Determine the working distance:

[0083] In a 4×4mm chip, the working distance of a 5-megapixel lens with a 1.5x magnification is generally in the 50-100mm range;

[0084] In a 7×7mm chip, the working distance of a 20-megapixel 1x lens is generally in the range of 80-150mm.

[0085] Step 5: Determine the depth of field:

[0086] In a 4×4mm chip, the depth of field of a 5-megapixel lens with a 1.5x magnification is typically 0.4mm;

[0087] In a 7×7mm chip, the depth of field of a 20-megapixel 1x lens is typically 0.6mm.

[0088] like Figure 2 As shown, when the lens is installed, the working distance between the lens and the chip is set within the optimal depth of field range, which can ensure the best detection effect and maintain good detection capabilities when the chip thickness changes slightly.

[0089] Combined with the above selection steps, for the 4×4mm and 7×7mm chips, the final selection and configuration of the optical path module is: 4×4mm chip:

[0090] Image sensor: 5 megapixels

[0091] Lens magnification: 1.5 times

[0092] Pixel size: 3.45μm

[0093] Recognition accuracy: 2.3μm

[0094] Field of view XY: 5.6×4.7mm

[0095] Working distance: 50-100mm

[0096] Depth of field: 0.4mm7×7mm Chip:

[0097] Image sensor: 20 megapixels

[0098] Lens magnification: 1x

[0099] Pixel size: 2.4μm

[0100] Recognition accuracy: 2.4μm

[0101] Field of view XY: 7.2×7.2mm

[0102] Working distance: 80-150mm

[0103] Depth of field: 0.6mm

[0104] Through the selection method of the optical path module, the resolution of the image sensor and the magnification of the lens can be accurately matched to meet the requirements of chips of different sizes and different detection accuracy. While meeting the detection accuracy, the detection cost is effectively controlled, so that the detection system has good compatibility and can adapt to detection objects of different sizes. For chips within a certain size range, the same optical path module can be used for detection, such as 1×1mm to 4×4mm chips using 5 million pixel image sensors and 1.5 times lenses for detection; 4×4mm to 7×7mm chips using 20 million pixel image sensors and 1 times lenses for detection, and there is no need to change the focal length and working distance. Compared with traditional detection solutions, the optical path module does not need to adjust the working distance, magnification and focal length, the lens does not need to move up and down, and can ensure that the chip is completely in the imaging field of view, and does not require the stage to have the ability to move in a plane, which greatly simplifies the detection equipment and reduces the cost of the detection equipment.

[0105] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A diffractive optical element detection system, characterized in that: It includes a wafer stage, an optical path module and a light source assembly arranged above the wafer stage, wherein the optical path module is arranged in different specifications and is removable, and an image sensor and a matching lens are arranged in the optical path module; The light source assembly comprises a positive light source arranged on one side of the lens and a backlight light source embedded on the upper surface of the wafer carrier.

2. A diffractive optical element detection system according to claim 1, characterized in that: The optical path module is disassembled and replaced as a whole.

3. A detection method based on the diffractive optical element detection system according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1. Select the appropriate optical path module and perform system calibration; S2, place the component to be inspected on the wafer stage and keep it in the center of the field of view of the optical path module; S3. Capture images through image sensors and perform image analysis to ensure that image accuracy meets detection requirements.

4. The detection method according to claim 3, characterized in that: The system calibration described in S1 includes the following steps: S11. According to the parameters of the optical path module, adjust the distance between the lens and the wafer stage so that the field of view and focal length meet the optimal working distance of the lens until the clearest image is obtained; S12, adjust the light source assembly to keep the light source stable so that the light beam is evenly irradiated to the surface of the component to be inspected; S13, using the component to be tested for testing, repeating steps S11 and S12 until the image resolution meets the requirements.

5. A diffractive optical element detection system according to claim 3, characterized in that: When the image sensor is used for detection in S3, images are captured using positive light source and backlight light source conditions respectively.

6. A diffractive optical element detection system according to claim 3, characterized in that: The image parsing described in S3 includes the following steps: S31, Image preprocessing and correction: denoising, adjusting brightness and contrast, and performing geometric and color correction to ensure that the image is clear and distortion-free; S32, region segmentation and feature extraction: extract and identify regions through edge detection and region segmentation, and identify key features of the components to be inspected; S33, Defect detection and quality verification: Compare and analyze defects in detection images and detect component defects.

7. A method for selecting an optical path module in a diffractive optical element detection system according to any one of claims 1 to 6, characterized in that: The following steps are involved: K1. Define defect size and determine defect detection requirements; K2. Select an image sensor with appropriate resolution according to the size of the component to be inspected and the defect detection requirements; K3. Calculate the required lens magnification and determine the lens and objective lens combination based on the sensor size and the size of the area to be measured; K4. Calculate the optimal working distance of the lens for chip detection according to the specifications of the selected lens and objective lens; K5. Determine the depth of field according to the detection requirements to meet the focus compensation of the size of the component to be inspected; K6. Complete the selection of the optical path module and install the optical path module in the detection system according to the optimal working distance in K4.

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