Overview and Working Principle of Achromatic Lens

07 Oct.,2024

 

Overview and Working Principle of Achromatic Lens

&#;. What is an achromatic lens?


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With the continuous development of science and technology, the optical industry is also booming, and optical lenses are used more and more widely. Today, let's learn the specific content and working principle of the most common achromatic lens.


An achromatic lens is a lens formed by cementing two optical components, a positive low refractive index and a negative high refractive index.


Compared to single-piece glass lenses, the cemented design of the double-piece lens provides the user with additional design freedom and further optimizes lens performance, so compared with the monolithic lens with equal diameter and focal length, achromatic lens has more obvious advantages.


Achromatic lens is made of concave and convex lenses made of two glasses with different optical properties. It is often used for convex lenses made of glass with small refractive index and large dispersion power, and concave lenses made of glass with large refractive index and small dispersion power.


Achromatic lenses generally can only superimpose the images and points of the two main colors of light that are considered to be the main ones, thereby eliminating the chromatic aberration of the two colors of light.


&#;. The working principle of achromatic lens


Chromatic aberration is caused by the difference in the dispersion and refractive index of light of different wavelengths in the glass, resulting in different focal points of light of different wavelengths, using the combination of different materials.


Achromatic lens has in various types of configurations, the common ones being positive achromats, negative achromats, triplet achromats, and aspheric achromats.


Note that an achromatic lens can be a doublet lens(two elements) or triplet (three elements), and the number of elements is independent of the number of rays corrected by the lens.


In other words, an achromatic lens in a doublet or triplet configuration can correct both red and blue light in the visible range.


&#;. What makes achromatic lenses important?


Because achromatic lenses focus the colors at the same point, they allow the user to fully focus the image. Compared with uncorrected singlet lens, achromatic lens can produce clearer image, which is easier to observe and obtain more accurate perception.

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Achromatic lenses revolutionized imaging when they were first introduced, and while the quality of lenses has continued to improve, achromatic lenses remain a staple in both scientific and non-scientific optical applications.


&#;. The advantages of achromatic lens components


Improved image quality: Achromatic lenses eliminate color banding, greatly improving image brightness and clarity, a fact that is especially true for polychromatic imaging.


Efficient light transmission: Unlike singlet lenses, the on-axis performance of achromatic lenses does not degrade with aperture size, allowing you to utilize the entire transparent aperture.


Cost-effective production: Although achromatic lenses can be improved, these lenses are much more expensive, and for most purposes, achromatic lenses provide a lot of correction, making them the most cost-effective way to obtain clear white light images.


To produce the desired color correction, achromatic lens manufacturers must use two or more types of optical glass, which have different amounts of wave dispersion.


Typically, the process involves concave lens elements with high dispersion and convex lens elements with low dispersion. The two lenses are mounted so that the deformation of one lens closely cancels the deformation of the other lens.


This type of achromatic lens is called an achromatic doublet lens and is the most common type of achromatic lens, although triplets also exist.

Achromatic Doublet - Optics Online

Achromatic doublet lenses ("achromat") are designed to eliminate chromatic and spherical aberrations inherent in singlet lenses.  When used on-axis,  an achromatic lens focuses an parallel input beam to a perfect "point", limited only by the effects of diffraction. This performance can be achieved over a broadband of wavelength.   Achromatic lenses can be used to collimate and focus laser beams.  They can also be used for high-quality imaging on-axis.  However,  the off-axis performance is significantly worse than the on-axis performance.  If your application requires good optical performance off-axis as well as on-axis,  multi-element lenses such as our digital imaging lenses are recommended.

For some applications it is desirable to have a high-quality lens with a lower f/# (for example,  collimating a diode laser with large divergence angle).  This can be done by adding a matching aplanatic meniscus lens to a doublet lens.  An aplanatic meniscus lens will shorten the focal length of the doublet lens (thus, lowering the F-num) without introducing additional spherical aberrations.

The following is the listing of our standard achromatic lenses.  They are all designed to achieve a wave-front aberration <1/4 wavelength.  You can also use lens design wizards to design custom achromatic lenses. Achromatic elements have a Minimum Order Quantity (MOQ) ranging from 100 to 1,000 units.

General Specifications:

Parameter Value Default unit mm Material Cemented crown and flint glasses Focal length tolerance +/-2% Diameter tolerance +0, -0.15mm Center thickness tolerance +/-0.25mm Centration 3 arc min Surface quality 40-20 Coating Single layer anti-reflection coating centered at 550nm

PN: ACH006-025 Description: Achromatic doublet lens, D=6.3, EFL=25 Diameter: 6.3 EFL: 25 BFL: 23.45 Tc1: 2.3 Tc2: 0.9 Tc: 3.2 Te: 2.73 Radius1: 12.37 Radius2: 11.16 Radius3: 32.17 Material1: BK7 Material2: SF5 Meniscus Lens: MNP006-048 Volume Price: $29.50 (MOQ Range Applies) Request Volume Quote

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