Near Infrared (NIR)

In the world of imaging, sometimes the invisible makes information visible. Mirror-like silicon wafer becomes transparent, human tissue allows penetration, the behavior of data carrying fiber optics is observe, or long wavelength laser beams are analyzed - all with wavelengths beyond that which the human eye can see. The wavelength band just beyond the visible is known as Near Infrared (NIR). To effectively utilize the powers of NIR, modern optics must be adjusted accordingly.

When light strikes a glass surface, a portion is bounced back, thereby reducing the strength of the transmitted image. Apply this to a zoom lens with better than a dozen surfaces, and the result is a severe reduction in intensity. To counteract this, the zoom lenses are coated with materials that minimizes this cascading effect. Standard lenses are coated to minimize this effect when used in the visible wavelength range. These coatings are not very effective above 900 to 1000nm.

To serve the NIR market, Navitar offers selected versions of its Zoom 6000, 12X, and PE machine vision lenses that have been coated to improve transmission in the NIR. Refer to the diagrams below for comparative results. FOV and magnification remain the same, but other wavelength dependent parameters will change slightly.

The standard lens resolution limits are based on an assumed average wavelength of 500nm and is inversely proportional to wavelength (~3000 * NA). Therefore, substituting a wavelength of 1500nm will reduce the maximum resolution by a factor of 3. In practice, this means a reduction of contrast at the higher wavelengths.

Lens focal lengths shift slightly with wavelength, which impacts the Numerical Aperture (NA), which affects the DOF (.0005/NA^2). Generally, the NA reduces, which produces a greater DOF, along with a reduction in maximum resolution.

Standard NIR microscope objectives are usually lower in NA, also producing less maximum resolution.

In order to avoid untold complexity and confusion, the wizard does not revise calculations based on a unique wavelength. The simple factoring above provides an indication of expected variations in performance.

The wizard will process your request assuming the standard wavelength and output the standard product options, but will indicate the availability of NIR options if "NIR" was checked initially. A Navitar Rep will discuss the possibility of procuring a non-standard NIR product.

The more popular product models are readily available with the new coatings (Zoom 6000, 12X Zoom, or Precise Eye). Motorized models are not listed, but may be built to order. To obtain a motorized version or investigate the feasibility of a non-listed model, contact the appropriate Navitar Sales Representative for your area.

Transmission of Zoom 6000 Lens
Image: 6X Zoom NIR Chart


Transmission of Zoom 12X Zoom Lens
Image: 12X Zoom NIR Chart


Transmission of Precise Eye Lens
Image: Precise Eye NIR Chart