A apochromatic lens can be defined as a lens made up of two different types of lenses with different focal lengths that cancel out apochromatic or color distortion. Chromatic aberration lenses are typically made up of two optical components bonded together, usually a positive low-refractive index element and a negative high-refractive index element. Apochromatic Doublet lenses are typically made from a positive Crown glass lens with a positive optical focal length that decreases with increasing wavelength (towards the red), bonded to a weaker Flint glass lens with a negative optical focal length that also decreases with increasing wavelength (amplitude). Apochromatic lenses are a combination of concave and convex glass plates that focus different colors of wavelengths in the light onto the same plane. Each type of glass disperses colors differently, and they are put together to balance and produce clear images.
Since the on-axis performance of apochromatic lenses does not decrease with larger apertures, optical systems do not need to be “stopped down”. Stopping down refers to reducing the size of its aperture, for example, by using a pinhole or variable aperture, to improve overall performance. Using the entire aperture, apochromatic lenses and apochromatic lens systems are faster, more efficient, and more powerful than equivalent systems using a single lens.
Lenses designed to control apochromatic or image defects (optical defects that cause the focus of all colors to converge at the same focal point) in imaging are called apochromatic lenses. Apochromatic lenses are especially suitable for a range of applications including fluorescence microscopy, image relaying, inspection, and spectroscopy, and are widely used in multi-lens optical systems typically composed of multiple apochromatic lenses. Complex lens systems that eliminate apochromatic and other monochromatic image defects are also used in high-quality microscopes and photographic equipment.
What makes apochromatic lenses so important? Apochromatic lenses focus color onto the same point, allowing users to focus on the image. Apochromatic lenses produce sharper images compared to uncorrected single lenses, making them easier to view and more accurately perceive. They have revolutionized the way you image. Despite improvements in lens quality, apochromatic lenses remain a staple product for both scientific and non-scientific optical applications.