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Category: Application Notes

 

Fresnel Lens Topography

Machined Parts Inspection from CAD models using 3D profilometry

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FRESNEL LENS

DIMENSIONS USING 3D PROFILOMETRY

Prepared by

Duanjie Li & Benjamin Mell

INTRODUCTION

A lens is an optical device of axial symmetry that transmits and refracts light. A simple lens consists of a single optical component for converging or diverging the light. Even though spherical surfaces are not ideal shape for making a lens, they are often used as the simplest shape which glass can be ground and polished to.

A Fresnel lens consists of a series of concentric rings, which are thin parts of a simple lens with a width as small as a few thousandths of an inch. Fresnel lenses contain a large aperture and short focal length, with a compact design reducing the weight and volume of material required, compared to conventional lenses with the same optical properties. A very small amount of light is lost by absorption due to the thin geometry of the Fresnel lens.

IMPORTANCE OF 3D NON-CONTACT PROFILOMETRY
FOR FRESNEL LENS INSPECTION

Fresnel lenses are extensively employed in the automotive industry, lighthouses, solar energy and optical landing systems for aircraft carriers. Molding or stamping the lenses out of transparent plastics can make their production cost-effective. Service quality of Fresnel lenses mostly depends on the precision and surface quality of their concentric ring. Unlike a touch probe technique, NANOVEA Optical Profilers perform 3D surface measurements without touching the surface, avoiding the risk of making new scratches. The Chromatic Light technique is ideal for precise scanning of complex shapes, such as lenses of different geometries.


FRESNEL LENS SCHEMATIC

Transparent plastic Fresnel lenses can be manufactured by molding or stamping. Accurate and efficient quality control is critical to reveal defective production molds or stamps. By measuring the height and pitch of the concentric rings, production variations can be detected by comparing the measured values against the specification values given by the manufacturer of the lens.

Precise measurement of the lens profile ensures that the molds or stamps are properly machined to fit manufacturer specifications. Moreover, the stamp could progressively wear out over time, causing it to lose its initial shape. Consistent deviation from the lens manufacturer specification is a positive indication that the mold needs to be replaced.

MEASUREMENT OBJECTIVE

In this application, we showcase NANOVEA ST400, a 3D Non-Contact Profiler with a high-speed sensor, providing comprehensive 3D profile analysis of an optical component of a complex shape.

To demonstrate the remarkable capabilities of our Chromatic Light technology, the contour analysis is performed on a Fresnel lens.

The 2.3” x 2.3” acrylic Fresnel lens used for this study consists of 

a series of concentric rings and a complex serrated cross-section profile. 

It has a 1.5” focal length, 2.0” effective size diameter, 

125 grooves per inch, and an index of refraction of 1.49.

The NANOVEA ST400 scan of the Fresnel lens shows a noticeable increase in height of the concentric rings, moving outward from the center.

2D FALSE COLOR

Height Representation

3D VIEW

EXTRACTED PROFILE

PEAK & VALLEY

Dimensional Analysis of the Profile

CONCLUSION

In this application, we have showcased that the NANOVEA ST400 non-contact Optical Profiler accurately measures the surface topography of Fresnel lenses. 

The dimension of the height and pitch can be accurately determined from the complex serrated profile using NANOVEA analysis software. Users can effectively inspect the quality of the production molds or stamps by comparing the ring height and pitch dimensions of manufactured lenses against the ideal ring specification.

The data shown here represents only a portion of the calculations available in the analysis software. 

NANOVEA Optical Profilers measure virtually any surface in fields including Semiconductors, Microelectronics, Solar, Fiber Optics, Automotive, Aerospace, Metallurgy, Machining, Coatings, Pharmaceutical, Biomedical, Environmental and many others.


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Machined Parts QC

Machined Parts Inspection

Machined Parts Inspection from CAD models using 3D profilometry

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MACHINED PARTS

inspection from CAD model using 3D profilometry

Author:

Duanjie Li, PhD

Revised by

Jocelyn Esparza

Machined Parts Inspection with a Profilometer
Machined Parts Quality Control Profilometry

INTRODUCTION

The demand for precision machining able to create complex geometries has been on the rise across a spectrum of industries. From aerospace, medical and automobile, to tech gears, machinery and musical instruments, the continuous innovation and evolution push expectations and accuracy standards to new heights. Consequently, we see the rise of the demand for rigorous inspection techniques and instruments to ensure the highest quality of the products.

Importance of 3D Non-Contact Profilometry for Parts Inspection

Comparing properties of machined parts to their CAD models is essential to verify tolerances and adherence to production standards. Inspection during the service time is also crucial as wear and tear of the parts may call for their replacement. Identification of any deviations from the required specifications in a timely manner will help avoid costly repairs, production halts and tarnished reputation.

Unlike a touch probe technique, the NANOVEA Optical Profilers perform 3D surface scans with zero contact, allowing for quick, precise and non-destructive measurements of complex shapes with the highest accuracy.

MEASUREMENT OBJECTIVE

In this application, we showcase NANOVEA HS2000, a 3D Non-Contact Profiler with a high-speed sensor, performing a comprehensive surface inspection of dimension, radius, and roughness. 

All in under 40 seconds.

CAD MODEL

A precise measurement of the dimension and surface roughness of the machined part is critical to make sure it meets the desired specifications, tolerances and surface finishes. The 3D model and the engineering drawing of the part to be inspected are presented below. 

FALSE COLOR VIEW

The false color view of the CAD model and the scanned machined part surface are compared in FIGURE 3. The height variation on the sample surface can be observed by the change in color.

Three 2D profiles are extracted from the 3D surface scan as indicated in FIGURE 2 to further verify the dimensional tolerance of the machined part.

PROFILES COMPARISON & RESULTS

Profile 1 through 3 are shown in FIGURE 3 through 5. Quantitative tolerance inspection is carried out by comparing the measured profile with the CAD model to uphold rigorous manufacturing standards. Profile 1 and Profile 2 measure the radius of different areas on the curved machined part. The height variation of Profile 2 is 30 µm over a length of 156 mm which meets the desired ±125 µm tolerance requirement. 

By setting up a tolerance limit value, the analysis software can automatically determine pass or fail of the machined part.

Machine Parts Inspection with a Profilometer

The roughness and uniformity of the machined part’s surface play an important role in ensuring its quality and functionality. FIGURE 6 is an extracted surface area from the parent scan of the machined part which was used to quantify the surface finish. The average surface roughness (Sa) was calculated to be 2.31 µm.

CONCLUSION

In this study, we have showcased how the NANOVEA HS2000 Non-Contact Profiler equipped with a high speed sensor performs comprehensive surface inspection of dimensions and roughness. 

High-resolution scans enable users to measure detailed morphology and surface features of machined parts and to quantitatively compare them with their CAD models. The instrument is also capable of detecting any defects including scratches and cracks. 

The advanced contour analysis serves as an unparalleled tool not only to determine whether the machined parts satisfy the set specifications, but also to evaluate the failure mechanisms of the worn components.

The data shown here represents only a portion of the calculations possible with the advanced analysis software that comes equipped with every NANOVEA Optical Profiler.

 

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Comparing Abrasion Wear on Denim

Introduction

The form and function of a fabric is determined by its quality and durability. Daily usage of fabrics cause wear and tear on the material, e.g. piling, fuzzing, and discoloration. Subpar fabric quality used for clothing can often lead to consumer dissatisfaction and brand damage.

Attempting to quantify the mechanical properties of fabrics can pose many challenges. The yarn structure and even the factory in which it was produced can result in poor reproducibility of test results. Making it difficult to compare test results from different laboratories. Measuring the wear performance of fabrics is critical to the manufacturers, distributors, and retailers in the textile production chain. A well controlled and reproducible wear resistance measurement is crucial to ensure reliable quality control of the fabric.

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Mechanical Broadview Map Selection Tool

We’ve all heard the term, time is money. Which is why many companies constantly seek methods of expediting and improving various processes, it saves time. When it comes to indentation testing, speed, efficiency and precision can be integrated into a quality control or R&D process when using one of our Nanovea Mechanical Testers. In this application note, we will be showcasing an easy way of saving time with our Nanovea Mechanical Tester and Broad View Map and Selection Tool software features.

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Portability and Flexibility of the Jr25 3D Non-contact Profilometer

Understanding and quantifying a sample’s surface is crucial for many applications including quality control and research. To study surfaces, profilometers are often used to scan and image samples. A large problem with conventional profilometry instruments is the inability to accommodate for non conventional samples. Difficulties in measuring non conventional samples can occur due to sample size, geometry, inability to move the sample, or other inconvenient sample preparations. Nanovea’s portable 3D non-contact profilometers, the JR series, is able to solve most of these problems with its ability to scan sample surfaces from varying angles and its portability.

Read about the Jr25 Non-contact Profilometer!

Identifying Cohesive Failure of Screen Protectors with Acoustic Emission

In today’s age of information, handheld electronic devices are extremely common amongst consumers.  These portable multifunctional devices, however, can be quite expensive. To protect the fragile components, such as the glass interface, screen protectors can be used. How effective are the screen protectors? Using Nanovea’s Mechanical Tester’s Micro Module with an acoustic emission attachment, we can clearly identify critical loads at which the screen protector fails.

Identifying Cohesive Failure of Screen Protectors with Acoustic Emission

1000°C Brinell Hardness w/ T2000 Tribometer

Material properties, such as reactivity and strength, can drastically change at higher temperatures. This makes high temperature applications, (e.g. jet engines, fabrication chamber material, and even cookware) require careful material selection. Thus, it is important to understand how materials behave in different temperature conditions. The strength of a material can be measured by using the Nanovea T2000 Tribometer. To demonstrate this, a steel sample was used to conduct Brinell hardness testing from temperatures ranging from 25°C to 925°C.

1000°C Brinell Hardness w/ T2000 Tribometer

500nm Glass Step Height: Extreme Accuracy with Non-Contact Profilometry

Surface characterization are current topics undergoing intense study. The surfaces of materials are important since they are the regions where physical and chemical interactions between the material and environment occur. Thus, being able to image the surface with high resolution has been desirable, since it allows scientists to visually observe the smallest surface details. Common surface imaging data includes topography, roughness, lateral dimensions, and vertical dimensions. Identifying the load bearing surface, spacing and step height of fabricated microstructures, and defects on the surface are some applications that can be obtained from surface imaging. All surface imaging techniques, however, are not created equal.

500nm Glass Step Height: Extreme Accuracy with Non-Contact Profilometry

Progressive Tribology Mapping of Flooring

The traffic of human movement, movement of furniture, and other daily activities imposes constant degradation onto flooring. Flooring, usually comprised of wood, ceramic, or stone, must be able to handle the wear and tear they are designed for, whether residential or commercial applications. For this reason, most flooring have a layer that is supposed to be resistant to wear called a wear layer. The thickness and durability of the wear layer will depend on the type of flooring and the amount of foot traffic it will be receiving. Since flooring can have multiple layers (e.g. UV-coating, wear layer, decorative layer, glaze, and etc.), the wear rate through each layer can be very different. With Nanovea T2000 Tribometer with a 3D Non-Contact Line Sensor attachment, the progression of wear on a stone and wood flooring is closely observed.

Progressive Tribology Mapping of Flooring

Adhesiveness of Tape via Nanoindentation

The effectiveness of tape is determined by its cohesive and adhesive abilities. Cohesion is defined as the tape’s internal strength while adhesion is the tape’s ability to bond to its interacting surface. The adhesion of tape is influenced by numerous factors, such as exerted pressure, surface energy, molecular forces, and surface texture [1]. To quantify adhesion of tapes, nanoindentation with the Nanovea Mechanical Tester’s Nano Module can be conducted to measure the work required to separate the indenter from the tape.

Adhesiveness of Tape via Nanoindentation

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