A double concave lens—also known as a biconcave lens—is a type of optical lens that is thinner at the center than at the edges and curves inward on both surfaces. It’s designed to diverge light rays, meaning it causes parallel rays of light to spread apart after passing through.
Analogy: Think of a double concave lens like a valley between two hills—light rolls in from both sides, only to spread outward after passing through the dip.
When light enters a double concave lens, the curved surfaces cause the rays to refract away from the optical axis. This makes it ideal for applications requiring controlled light dispersion or beam expansion.
Mount the lens securely in an optical holder.
Align the optical axis with the light source using a laser pointer or collimated beam.
Adjust distance between the lens and detector until desired divergence is achieved.
Use anti-reflective coatings if light loss through reflection is a concern.
Tip: For optimal results, combine with convex lenses to control focal length and beam convergence.
[ Collimated Light ] → [ Double Concave Lens ] → [ Diverging Light Rays ]
| Parameter | Typical Range/Spec |
|---|---|
| Radius of Curvature | -10 mm to -100 mm |
| Focal Length | Negative values (e.g., -25 mm) |
| Transmission Range | 350 nm – 2500 nm (Visible to NIR) |
| Coating Options | AR (Anti-Reflective) for UV, VIS, NIR |
| Optical Material | BK7, Fused Silica, SF11 |
Risk: Incorrect alignment causes asymmetric light distortion.
Solution: Always align the optical axis perpendicular to the lens center.
Risk: Light intensity loss due to internal reflection.
Solution: Use AR coatings optimized for the working wavelength.
Risk: Thermal expansion in high-power lasers can crack lenses.
Solution: Choose fused silica for thermal stability.
| Industry | Application | Environment |
|---|---|---|
| Optical Engineering | Beam expanders, collimators | Clean lab or vacuum environment |
| Laser Systems | Divergence control for diode lasers | High-precision setup required |
| Medical Imaging | Negative lens group in microscopes | UV/NIR sensitive environments |
| Astronomy | Wide-angle field manipulation in telescopes | Extreme cold, minimal light |
| Education | Demonstration of refraction principles | Indoor classroom |
Strong: Controlled labs, optical benches, dry indoor setups.
Weak: Outdoor rugged environments, high-impact or dusty conditions.
Double concave lenses are embedded in light guide systems to diffuse and direct display projections toward the eye.
Used in optical simulators for pilot or medical training to recreate a natural field of view through divergence techniques.
Facilitates the expansion of laser beams to cover wider detection areas.
Example: A double concave lens with -30 mm focal length is often used to spread infrared beams in gas detection modules.
Double concave lenses are indispensable in systems where light divergence is essential. From laser beam shaping to medical imaging and AR interfaces, their ability to control, spread, and manipulate light with precision makes them a silent hero in the optics toolbox.
When used correctly and within defined parameters, they deliver consistent, high-performance outcomes across a range of industries.
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