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Precision-engineered telecentric lenses optimized for photovoltaic inspection, EL imaging, and automated crack detection systems.
Understanding the optical science behind defect-free photovoltaic manufacturing
Solar cells are among the most structurally sensitive semiconductor components in modern manufacturing. During production, transportation, and installation, photovoltaic (PV) cells are susceptible to micro-cracks — fractures often invisible to the naked eye yet capable of causing dramatic power output degradation over time. Studies indicate that even a single undetected crack can reduce a solar module's efficiency by up to 30%, and widespread micro-cracking across a panel can render it commercially unviable within a few years of deployment.
Traditional machine vision systems using standard lenses face critical limitations: perspective distortion, parallax error, and inconsistent magnification across the field of view. These optical imperfections make it extremely difficult to accurately identify and measure cracks at the micron scale — precisely where the most damaging defects reside.
This is where bi-telecentric lens technology becomes indispensable. A bi-telecentric (or double-telecentric) lens maintains telecentricity on both the object side and the image side, eliminating perspective error entirely and delivering consistent magnification regardless of object distance variation. The result is an imaging system capable of resolving crack widths as narrow as 2–5 µm across a full solar cell surface — enabling reliable automated defect classification at production line speeds.
In a standard lens system, objects at different depths appear at different magnifications — a fundamental problem when inspecting flat but slightly warped solar cells on a conveyor. Bi-telecentric lenses solve this by ensuring that the chief ray is parallel to the optical axis on both sides of the lens system. This means that even if a solar wafer is not perfectly flat, or if there is slight vibration in the production line, the image dimensions remain accurate and undistorted.
For Electroluminescence (EL) crack detection — the gold standard for identifying micro-cracks in crystalline silicon solar cells — bi-telecentric lenses provide the sharpest, most geometrically accurate images of the EL emission pattern. Cracks appear as dark lines interrupting the bright EL glow, and the telecentric imaging system ensures that these features are captured with consistent contrast and resolution across the entire cell area, from center to edge.
Combined with high-resolution CMOS sensors and AI-powered image analysis algorithms, bi-telecentric lens systems now achieve defect detection rates exceeding 99.5% in leading PV manufacturing facilities — a benchmark that conventional optical systems simply cannot match.
Technical superiority that translates directly into manufacturing yield and product reliability
Bi-telecentric design ensures that all points across the solar cell surface are imaged at identical magnification, eliminating the geometric distortion that causes false positives and missed defects in conventional lens systems.
With telecentric optics, dimensional measurements of crack length, width, and propagation direction achieve accuracy down to 1–2 µm — critical for classifying cracks by severity and predicting long-term degradation behavior.
The parallel chief ray geometry of bi-telecentric lenses enables perfectly uniform illumination across the entire field of view, maximizing contrast for EL, PL, and white-light inspection modalities used in PV quality control.
Solar wafers and cells often exhibit slight bow or warp. The extended depth of field in bi-telecentric lens systems maintains focus and measurement accuracy even when the object surface deviates by ±0.5mm from the nominal focal plane.
Optimized for integration with high-speed conveyor systems, Canrill bi-telecentric lenses support frame rates up to 200fps on large-format sensors, enabling 100% inline inspection without reducing throughput.
The geometrically perfect images produced by bi-telecentric lenses provide ideal training data for deep learning crack classification models, dramatically reducing the time required to achieve high-accuracy AI inspection deployment.
Market forces accelerating demand for advanced bi-telecentric optical inspection solutions
The photovoltaic industry is experiencing unprecedented growth. Global solar panel installations surpassed 500 GW annually in 2024, and projections suggest this figure will exceed 1 TW per year by 2030. At this scale, even a fraction-of-a-percent defect rate translates into billions of dollars in warranty claims, field failures, and reputational damage for manufacturers.
Leading solar manufacturers in China, Germany, the United States, and Southeast Asia are investing heavily in automated optical inspection (AOI) systems to maintain quality at gigawatt production volumes. Bi-telecentric lenses have emerged as the optical component of choice for these systems, replacing older telecentric or conventional lens designs that cannot meet the resolution and accuracy requirements of next-generation solar cell formats including M10 (182mm) and G12 (210mm) wafer sizes.
The integration of convolutional neural networks (CNNs) and transformer-based vision models into PV inspection workflows is fundamentally changing how cracks are detected and classified. Modern AI systems can distinguish between finger cracks, busbar cracks, edge cracks, and black core defects in real time — but only when fed with high-quality, geometrically accurate images. Bi-telecentric lenses are the enabling optical technology that makes this AI performance possible at production line speeds.
The industry transition from conventional PERC cells to advanced cell architectures including Heterojunction Technology (HJT), Tunnel Oxide Passivated Contact (TOPCon), and back-contact designs is creating new inspection challenges. These next-generation cells feature thinner wafers (120–150 µm), more complex metallization patterns, and greater sensitivity to mechanical stress — all of which increase the prevalence and severity of micro-cracks during manufacturing.
For HJT cells in particular, the amorphous silicon passivation layers are extremely sensitive to thermal and mechanical stress. Cracks that would be benign in a PERC cell can cause catastrophic delamination in an HJT module. This demands even higher resolution and sensitivity from inspection optics, driving adoption of high-magnification bi-telecentric lenses with larger format sensor compatibility.
As solar installations increasingly pair with battery energy storage systems (BESS), the long-term reliability of individual solar modules becomes even more critical. Cracked cells in a storage-coupled PV system can cause subtle output imbalances that accelerate battery degradation and create safety risks. This lifecycle perspective is pushing procurement teams at major solar developers to demand stricter incoming quality inspection standards — directly increasing demand for bi-telecentric lens-based inspection systems throughout the supply chain.
From wafer to module — comprehensive optical inspection coverage across the entire PV value chain
EL imaging is the most powerful technique for detecting micro-cracks in crystalline silicon solar cells. When forward-biased current is applied, intact cell areas emit near-infrared luminescence while cracked or inactive regions appear dark. Bi-telecentric lenses capture this EL emission pattern with uniform magnification and minimal vignetting, enabling precise mapping of crack location, length, and orientation across the full cell area — even for large-format M10 and G12 cells. Canrill's bi-telecentric lenses optimized for 900–1100nm NIR wavelengths deliver exceptional sensitivity for EL crack detection in both offline and inline configurations.
Before cells are even processed, incoming silicon wafers can be screened for bulk defects and surface damage using photoluminescence imaging. PL inspection at the wafer stage allows manufacturers to reject defective substrates before adding processing value — dramatically reducing waste. Bi-telecentric lenses provide the geometric accuracy needed to correlate PL defect maps with subsequent EL images, enabling root cause analysis of crack formation during cell processing steps such as laser scribing, screen printing, and sintering.
In addition to EL/PL imaging, white light automated optical inspection is used to detect surface defects including edge chips, paste printing defects, and visible cracks on the front and rear cell surfaces. Bi-telecentric lenses in white light AOI systems provide distortion-free imaging of the entire cell surface in a single shot, with resolution sufficient to detect cracks as narrow as 5 µm. The telecentric illumination geometry ensures consistent shadow contrast for raised defects, improving detection reliability for three-dimensional crack features that partially penetrate the cell thickness.
Cracks can form or propagate during the lamination process when cells are encapsulated in EVA or POE films under heat and pressure. Module-level EL inspection using bi-telecentric lens arrays is increasingly deployed after lamination to catch these process-induced defects before modules are framed and shipped. The large field of view requirements at module level (typically 1000mm × 2000mm) are addressed by multi-camera array systems, each equipped with a bi-telecentric lens to ensure seamless image stitching without magnification discontinuities at the field boundaries.
Advanced module designs using shingled cells and half-cut cell technology present unique inspection challenges. Shingled cells are laser-cut into narrow strips (typically 5–6mm wide) and overlapped like roof shingles, creating a dense array of potential crack initiation sites along cut edges. Half-cut cells reduce resistive losses but double the number of cells per module, increasing inspection complexity. Bi-telecentric lenses with high aspect ratio fields of view and sub-pixel resolution are essential for inspecting these high-density cell arrangements at production speed.
Bi-telecentric lenses are deployed in both inline (on-conveyor) and offline (sampled batch) inspection configurations. Inline systems demand lenses with short exposure time compatibility, vibration tolerance, and robust mechanical design for 24/7 production environments. Offline systems prioritize maximum resolution and sensitivity for detailed defect characterization. Canrill's bi-telecentric lens range covers both use cases, with C-mount, F-mount, and custom flange options enabling rapid integration into leading machine vision platforms from Cognex, Keyence, Basler, and Allied Vision.
As the first company in China to specialize exclusively in telecentric lens manufacturing and design, Canrill Optics brings over 15 years of deep optical engineering expertise to every solar cell inspection challenge. Our bi-telecentric lenses are engineered from the ground up for the demanding requirements of PV quality control — delivering the resolution, accuracy, and reliability that world-leading solar manufacturers depend on to protect their brand and maximize yield. From wafer inspection to module-level EL testing, Canrill provides the complete optical solution for every stage of your PV production line.
From manufacturing to creation — building the world's leading telecentric lens technology
Canrill Optics, established in 2009, is the first company in China to focus on the manufacturing and marketing of telecentric lenses and telecentric lens design. We are the only company in the world to build a complete supply chain with our own mechanical factory and optical factory dedicated entirely to industrial lenses.
Over the years, as a custom lens manufacturer, Canrill lenses have been upgraded through four generations of advanced technology and performance, earning the trust of clients worldwide. We have successfully partnered with world-famous brands including Samsung, Apple, LG, Huawei, Han's Laser, TSMC, and many leading solar manufacturers.
Our objective is to produce top-level lenses and become one of the leaders in telecentric technology. From manufacturing to creation, we are on the way.
Expert engineers and optical scientists dedicated to advancing telecentric lens technology
Since founding Canrill in 2009, Simon has been focused on building the world's leading manufacturer of telecentric lenses. Under Simon's leadership, Canrill has grown into a 100+ person company renowned in both China and overseas, with clients in over 40 countries.
Senior optical designer with 10+ years of experience in the design and inspection of telecentric lenses and illumination systems. Leads R&D for next-generation bi-telecentric solutions for solar cell and semiconductor inspection.
15+ years of experience in mechanical design for precision optical instruments. Oversees the development of robust lens housings and mounts optimized for demanding industrial inspection environments including PV manufacturing lines.
Internationally recognized certifications underpinning our commitment to optical excellence
Canrill ISO 9001
Lens Cone RoHS Certificate 1
Lens Cone RoHS Certificate 2
Lens Cone RoHS Certificate 3
Lens Cone RoHS Certificate
Explore our full range of high-precision telecentric lenses — engineered for PV inspection, semiconductor AOI, and precision measurement
