In precision optics, clarity is everything. Whether you're designing a laser system for medical diagnostics, a high-resolution imaging device for aerospace, or a compact sensor for LiDAR, optical aberrations can be the silent performance saboteurs.
Among the most common culprits? Chromatic and spherical aberrations. Fortunately, achromatic lenses, which are commonly known as achromats, offer a powerful solution.
Understanding the Chromatic and Spherical Aberrations
Chromatic Aberration: The Color Splitter
Chromatic aberration occurs when different wavelengths of light fail to converge at the same focal point. This results in color fringing or distortions in high-contrast scenarios. This phenomenon is typically caused by light dispersion — slight variations in each material’s refractive index in an optical design. This leads to different colors being focused on different points. It’s especially problematic in broadband imaging systems and can severely degrade image quality.
Spherical Aberration: The Focus Flattener
Spherical aberration is caused by light rays passing through the edges of a spherical lens focusing at different points than those passing through the center. It can lead to blurred or distorted imaging, even if the lens is perfectly centered and aligned, since light rays will focus on different points depending on their positioning. This is less than ideal for precise optical imaging systems like microscopes, telescopes, and endoscopes that rely on clarity and high-resolution results
Achromats: The Optical Equalizers
This is where an achromatic lens comes in. Designed to minimize the effects of aberration, an achromatic lens is typically a doublet made by cementing together two types of lenses: one with a positive power and low refractive index (typically, crown glass) and one with a negative power and high refractive index element (flint glass).
These materials have different dispersion properties, allowing the lens to bring two wavelengths into the same focus. This dramatically reduces chromatic aberration.
The standard achromatic doublet configuration can correct chromatic and spherical aberrations most often with both crown and flint glass types.
While achromats are often designed to correct chromatic aberration, their doublet and triplet configurations also help minimize spherical aberration. By carefully selecting the curvature and spacing of each element, designers can optimize the lens for both color and shape.
Achromats typically are effective across a broad spectral range, from visible light to near-infrared and ultraviolet regions, and are designed in various configurations — such as doublets and triplets — making them versatile to a range of applications.
Ross has the largest selection of in-stock and custom achromatic doublets and triplets in the industry. Available in a wide variety of anti-reflection coatings, our achromats are designed to meet the most stringent tolerances in today’s cutting-edge electro-optical, imaging, and laser systems.
Applications Across Industries
Achromats are indispensable in industries where precision and clarity are non-negotiable:
Medical Imaging: In endoscopy and ophthalmology, achromats ensure sharp, color-accurate visuals for diagnostics and surgery. This clarity is necessary for accurate diagnostics, surgical precision, and patient safety.
Aerospace & Defense: From satellite optics to targeting systems, achromats help maintain resolution across extreme light and environmental conditions, where image reliability is mission-critical.
Scientific Research & Instrumentation: Microscopes and spectrometers rely on achromats to deliver accurate, high-contrast images to enable researchers to observe fine details and spectral data without distortions.
Laser Systems: Achromats are used to focus and shape beams with minimal distortion, critical in both industrial and medical laser applications.
LiDAR & Sensing: In autonomous systems, achromats help maintain signal integrity across wide spectral bands. Their use in LiDAR systems ensures accurate distance measurement and object detection.
Case Study: Custom Optics for Surgeons
A California-based medical device manufacturer specializing in ophthalmic surgery turned to Ross Optical for a precision optics solution. The challenge? Their product line, used in both eye surgery and post-operative exams, required high-performance singlets and achromatic doublets that met strict quality and cost constraints.
Ross Optical’s engineering team collaborated closely with the customer from the start, designing and producing custom optical components tailored to the device’s requirements. Ross not only delivered the required optics but also provided cost-saving recommendations that improved the overall product design and ensured quality with its 100% inspection.
Sourcing Considerations
While serving a vital role in optical systems, manufacturing achromats is complex, from material selection to precise alignment. When sourcing an achromat, there are several factors to consider:
Materials: The choice of optical glass directly impacts performance, manufacturability, and costs. It is crucial to confirm material availability early in the design phase and account for variability in refractive index, dispersion, and thermal expansion across materials.
Wavelength Range: Standard doublet achromats correct for two wavelengths, but custom designs can target broader ranges. Be sure to collaborate with an experienced supplier to tailor the achromat to your needs.
Coatings: Coatings are important to reduce aberrations. For example, Ross provides a wide range of anti-reflection coatings for their line of doublets and triplets. When sourcing, consider the type of coating, coating uniformity, and the supplier’s in-house coating capabilities to reduce delays and improve quality control.
SWaP: In applications like aerospace, laser, and handheld medical devices, compactness and weight are key. Micro achromats often provide optimized spherical and chromatic correction while keeping weight and size in mind.
Cost vs. Performance: While achromats offer a cost-effective alternative to more complex apochromatic or aspheric systems, the total cost should account for tolerance requirements, coating complexities, supplier capabilities, and lead time.
Ready to Source Smarter?
Understanding the nuances of achromat sourcing is only half the equation. Tolerance sensitivity can make or break your optical design. Don’t leave performance or cost to chance.
Achromatic lenses may be simple in concept, but their impact on optical performance is vital. By effectively reducing both chromatic and spherical aberrations, achromats enable sharper, more accurate imaging across a wide range of applications. Whether you're building the next generation of LiDAR sensors or refining a surgical laser system, achromats are a cornerstone of optical clarity.
Want to find the perfect achromat for your next project? Contact us at sales@rossoptical.com to find out more.
