White balance calibration ensures colorimeter measurement accuracy on a display, but changing of display luminance can cause spectral drift, leading to the need of recalibration. Mimicking a micro-LED or OLED panel and using a colorimeter, we compare color error sources, finding spectral drifts to be a major contributor to the error. This finding highlights the need for high-speed recalibration in mass production.
Flat-field correction (FFC) is essential for addressing relative illuminance roll-off in optical imaging systems, a calibration process that requires capturing an image of a uniform light source. In imaging systems capable of mimicking or measuring SPH, CYL, AXIS, such as those used for eye prescriptions, the number of images required to collect for FFC increases with each lens adjustment. We propose a numerical method that uses a few core images to synthesize FFC images for various configurations, reducing data requirements substantially. This method was validated on two imaging systems with differing optical alignment quality, achieving relative illuminance falloff of less than 2% with only 5% the amount of the original data.
A single optical system with features of both automatic calibration and multiple configurations has been developed for high-resolution wavefront measurements. With the configuration of fine measurements, the tester can scan a large area to obtain mapping data with detailed local wavefront information of the sample. The tester can also take a fast snapshot of wavefront measurement by using the configuration of coarse measurements.
Existing position sensors have limitations such as single function, limited range, slow speed, and low resolution. Emerging applications need sensors that work in variable and unpredictable environments with multiple dimensions. The proposed system offers advantages that outweigh these existing sensors. It has a unique design that combines optical imaging and laser techniques to provide a full capability of 6-dimensional sensing with only one sensor system, covering a wide range for both near and far fields with both high spatial and angular resolutions. The sensor can also easily extend its capability by modifying optics and laser or exploiting new optical components. In addition to the above six degrees of freedom, the sensor has potential to detect additional information such as the speed and acceleration of the target for both linear translation and rotation, by simply record the time lapse between events. Therefore, our technique has broad potential applications. It can also facilitate technical advances in metrology, biomedicine, and scientific research.
This paper discusses a methodology based on the free space depth measurement scheme facilitating the allocation of the real optical axis relative to the newly established datum resulting from the presence of a mechanical attachment. The methodology only requires depth data in one direction and the DUT does not need to be perfectly aligned with the sensor. This, in turn, enables an in-situ optical alignment capability in the mass-production environment, where position accuracy and repeatability are critical.
This paper discusses a high sensitivity quantitative method to efficiently detect the defect existence and allocate the impurity down to single micron level. This methodology by nature only enhances the defects within the signal path no matter on the optics surface, in the coating or inside the glass material, which fundamentally helps on high contrast optics like the AR/VR metrology lens which mimics human eye’s sensitivity, or deep space observation optics or biology imaging system.
This paper reviews an inspiration model for young talents in MLOptic corp.’s industrial education outreach program. With proper mindset training to focus on the end delivery through milestone-based essential necessaries allocation, proactively self-learning and logistic thinking capabilities can be greatly magnified independent of education level and age, significantly boosts the courage to explore unknown technical or non-technical challenges, promotes confidence and desires to self-grow into a technical expert. The logic to get things done naturally plants the seed of leadership and grows efficiently through more teamwork practice. An example was described to support this model.
MTF tests, one of the most important optical metrology tasks for AR/MR glasses, analyze the DUT’s (Device Under Test) optical resolution to provide quantitative feedback for design verification and manufacturing process control. Due to the immaturity of the whole design/fabrication technical chain, current diffractive AR glasses show strong angular resolution non-uniformity across the FOV, and the measurement’s angular accuracy and consistency significantly impact the test repeatability and reproducibility. This paper presents a novel optical calibration apparatus to enable absolute angular alignment/verification, which can be implemented with a small volume and easily fit into the metrology equipment.
This paper first reviews the practical optical calibration constrains of the optical metrology equipment Periscope, which measures AR/VR glass’s binocular disparity by providing the numerical measurement of non-parallelism between two eyes’ optical axes. A self-adaptive calibration methodology with close loop feedback to track on the calibration tool’s accuracy is proposed to precisely calibrate the parallelism of the periscope’s two optical sensing channels and efficiently verify this parameter periodically with consistency over time or instruments. A few implementation schemes, including a passive target, an active selfreferenced target, and two different sensitivity enhanced targets are discussed in depth to compare the performance contributors: accuracy, repeatability, and system complexity, which leads to the recommendations for different application scenarios. Beyond the AR/VR disparity measurement a potential application based on the same methodology is introduced to evaluate the precision motion system’s accuracy and tolerance.
With microLED panel technology quickly evolving to smaller pixel size and larger resolution, optical metrology is on-demand to support both design verification and process yield control by providing a solution with high resolving power high through-put and less calibration spectrum dependency. This paper reviews the trade-off between all conflicting factors, and discusses the calibration algorithm to remove the spectrum dependence, describes a novel imaging colorimeter which precisely attacks all above technology inconsistencies with the final goal of: single micron pixel resolving power by combination of optical resolution and digital imaging processing algorithm, large optical FOV to reduce number of frames to be captured for whole panel inspection, calibration algorithm to precisely transfer the true color and brightness information between NIST traceable light source without spectrum matching demand, and inherent final balanced high through-put image capturing.
To achieve user immersion experience and wearing comfort, AR/VR glass designer targeting general consumer market strives hard for larger FOV and smaller form factor. These ultimate goals cause challenges for mass production metrology due to geometrical conflicts and test cost inefficiency. Two imaging system designs are reviewed in this paper. Both resolve above practical issues of AR/VR glass optical resolution test by shifting the complexity of the lens design to a novel optical coupler. This coupler smartly remaps discrete angular field points onto a detector with minimum spatial gap. Proposed methodologies significantly decrease the metrology equipment cost for mass production.
Optical metrology provides direct feedback for AR/VR/MR design verification and manufacturability evaluation by imitating the human eye’s optical properties of resolution, color sensitivity and uniformity over large FOVs, self-adaption to focus location, brightness and contrast. This paper defines a generic, standardized optical metrology platform to efficiently integrate various optical metrology instruments into the platform’s global coordinate system by utilizing a specially designed active-optical calibration target to precisely map the optical entrance pupil of any optical metrology instrument and device under test (DUT) to a common reference point, providing effective data correlation. The platform can easily accommodate common AR/VR/MR optical metrology equipment for measurements of: MTF/contrast, color and brightness, virtual distance, angular FOV, and binocular alignment error; to provide a unified metrology platform for optical measurements.
High speed strobe based illumination scheme is one of the most critical factors for high throughput semiconductor defect inspection applications. HB LEDs are always the first and best options for such applications due to numerous unique advantages such as excellent spatial and temporal stability, fast responding time, large and linear intensity dynamic range and no heat issue for the extremely low duty cycle applications. For some applications where a large area is required to be illuminated simultaneously, it remains a great challenge to efficiently package a large amount of HB-LEDs in a highly confined 3D space, to generate a seamless illuminated area with high luminance efficiency and spatial uniformity. A novel 3D structured collimation lens is presented in this paper. The non-circular edge shape reduces the intensity drop at the channel boundaries, while the secondary curvatures on the top of the collimator lens efficiently guides the light into desired angular space. The number of the edges and the radius of the top surface curvature are control parameters for the system level performance and the manufacture cost trade-off. The proposed 3D structured LED collimation lens also maintains the benefits of traditional LED collimation lens such as coupling efficiency and mold manufacture capability. The applications can be extended into other non-illumination area like parallelism measurement and solar panel concentrator etc.
Semiconductor fabrication process defect inspection industry is always driven by inspection resolution and through-put. With fabrication technology node advances to 2X ~1Xnm range, critical macro defect size approaches to typical CMOS camera pixel size range, therefore single pixel defect detection technology becomes more and more essential, which is fundamentally constrained by camera performance. A new evaluation model is presented here to specifically describe the camera performance for semiconductor machine vision applications, especially targeting at low image contrast high speed applications. Current mainline cameras and high-end OEM cameras are evaluated with this model. Camera performances are clearly differentiated among CMOS technology generations and vendors, which will facilitate application driven camera selection and operation optimization. The new challenges for CMOS detectors are discussed for semiconductor inspection applications.
Semiconductor see-through-silicon metrology and inspection applications use traditionally InGaAs based cameras due to
perfect spectral sensitivity. But InGaAs cameras do not carry equivalent advantages as Silicon based imagers such as
pixel size, pixel array resolution and through-put etc. This paper first reviews the novel technologies which dramatically
enhance silicon imagers' sensitivity for this see-through silicon application. Inspection through-put is analyzed based on
multiple system implementation:, start-stop scan mode vs. continuous scan mode, 2D cameras vs. TDI line scan cameras,
against to traditional InGaAs camera based continuous scan platform. The simulation data shows that systematic
through-put based on 2D silicon cameras can be competitive to today's InGaAs system, while TDI line scan system can
be much faster than system based on near future's high resolution and high speed InGaAs cameras.
Dark-field defect inspection is an essential quality control method for the semiconductor fabrication industry, and it is broadly applied for micro particles detection in almost every fabrication process. Diode laser based dark-field illumination systems (LDFs) play a critical role in such illumination schemes due to its unique optical/mechanical properties. This paper discusses a complete LDF system model, includes the mathematical and optical descriptions of LDF system fundamentals. A series of trade-off curves are developed in this model, which describe system performance under different constraints. This model can either efficiently facilitate system design work for generic/unique applications, or can be used to evaluate existing LDF system performance.
KEYWORDS: Signal to noise ratio, Silicon, Image processing, Inspection, Sensors, Semiconducting wafers, Machine vision, Reflection, Imaging systems, Human vision and color perception
With semiconductor development processes hitting harder and harder on Moore's law to continuously scale down, high
density advanced packaging technologies become a promising alternate route to improve transistor density. Chip
integration IO/cm2 density jumps quickly by orders from 2D packaging of 102 to wire bonded chip stack of 103, to TSV
of 104~105 and to advanced 3D integration of 105 to 106. Starting with wire bonding and now prevailing with TSV, more
and more silicon layers are stacked up in 3D dimension to improve system density. A typical stacked wafer sample has
two wafers glued together with patterned area sandwiched in between. Outer surfaces can be polished or unpolished bare
silicon surface, or patterned surface.
By utilizing diffractive, refractive and graded-index optics technology, a miniature (1 mm x 1 mm x 2 mm) Computer-Tomography Imaging Spectrometer (CTIS) sensor has been designed with 16 independent optical channels working in a snap-shot mode for hyper-spectral imaging. The designed prototype covers a 400~700 nm wavelength range. One optical channel has been fabricated and characterized. By azimuthally rotating this optical channel along the optical axis and collecting different dispersed images to simulate the full sensor read-out, the full hyperspectral detection scheme has been demonstrated.
This course explains basic principles and applications of optical metrology for AR/VR/MR. A primary goal of the course is to reveal the logic of optical methodologies as being critical to the design verification and production yield improvement for this revolutionary consumer electronics product. The class will explore current AR/VR development challenges and how cutting-edge optical metrology technologies are used to boost this fast-growing industry. Out of this course the audience will be able to comfortably describe the fundamental demands of optical metrology for this industry and confidently define a solution path for a particular application.
This course explains basic principles and applications of Optical Metrology for AR/VR/MR. A primary goal of the course is to reveal the logic of optical methodologies being critical to the design verification and production yield improvement for this
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