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Why use achromatic lenses?

来源:JUKA Optical 发布时间:2020-06-29 00:00:00 浏览量:3486

An achromatic lens is a lens composed of two optical components of positive low refractive index (Crown glass) and negative high refractive index (Flint glass). Compared with the single lens, the design of the double lens can provide users with additional design freedom and further optimize the lens performance. Therefore, the advantages of achromatic doublet lenses are more significant than single lenses of equal diameter and focal length. As the achromatic lens supplier, JUKA Optical can manufacture achromatic doublet lens, achromatic triplet lens and achromatic cylindrical lens. If you need achromatic optical lens, please contact JUKA Optical.

 

Achromatic lenses have various types of configurations, among which common ones are positive achromatic lenses, negative achromatic lenses, triplet achromatic lenses, and aspheric achromatic lenses. It should be noted that the achromatic lens can be doublet (two-element) or triplet (three-element), and the number of optical elements is independent of the amount of light corrected by the lens. In other words, achromatic doublet lenses and achromatic triplet lenses can both correct red and blue light in the visible range. Please refer to Figures 1 to 4 for various types of achromatic lenses.

 

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Illustrate

Dia: diameter
R: radius of curvature
ET: edge thickness
EFL: effective focal length
CT: center thickness
P: main point
BFL: back focus

 

Aspheric achromatic lens

 

Aspheric achromatic lens is a cost-effective lens with excellent chromatic aberration and spherical aberration correction function. It can meet the demanding imaging requirements of today's optical and vision systems in an economical way. With the assistance of aspheric achromatic lenses, the lens design of relay systems, condenser systems, high numerical aperture imaging systems, and beam expanders can be improved. Figures 5 and 6 compare achromatic lenses and aspherical achromatic lenses. Figure 5 shows the modulation transfer function (MTF) and transverse ray chromatic aberration diagram of TECHSPEC® achromatic lens with a diameter of 12.5mm and a focal length of 14mm. Figure 6 shows the modulation transfer function and transverse ray fan chromatic aberration diagram of the # 49-658 TECHSPEC ™ aspheric achromatic lens with a diameter of 12.5 mm and a focal length of 14 mm. As shown in the figure, the resolution performance of aspheric achromatic lenses is better than that of achromatic lenses.

 

Aspheric achromatic lenses are made of glass optical lenses cemented with photosensitive polymers. The photopolymer is only used on one side of the doublet lens, and is very easy to replicate in a short time, while providing the same flexibility as a specific multi-element assembly. Unlike glass elements, aspheric achromatic lenses have a smaller operating temperature range, between 20 ° C and 80 ° C. This temperature range limits the possibility of using antireflective coatings on aspheric achromatic lens surfaces. In addition, the material of the aspheric achromatic lens blocks the transmission of deep UV, making the lens unsuitable for some applications. Although this lens is not scratch resistant, it is extremely cost effective and easy to replace. In summary, this lens still has many advantages. Figure 7 shows the manufacturing process of aspheric achromatic lenses.

The role of achromatic lenses

 

1.Improve the imaging of polychromatic light
Achromatic lenses are far superior to simple multicolor "white light source" imaging lenses. The two optical elements that make up the achromatic lens are combined to correct the inherent chromatic aberration of the glass. Because it can eliminate chromatic aberrations that are difficult to solve, achromatic lenses are extremely cost-effective in terms of illumination and imaging of polychromatic light. See Figure 8 for an explanation of this concept.

 

2.Correct spherical aberration and on-axis coma
The correction degrees of freedom for spherical and coma aberrations enable the lens to achieve better on-axis performance at larger apertures. Compared with a simple lens, an achromatic lens can consistently provide a smaller spot size and more excellent imaging quality without reducing the clear aperture. Figure 9 shows how achromatic lenses correct longitudinal chromatic and spherical aberrations of axial objects. Figure 10 shows that the biconvex lens separates the white light source like a prism, making blue light more concentrated than red light. Figure 11 shows how the spherical aberration of the bi-convex lens is insufficiently corrected. The spherical aberration (SA) will vary with f / # and will also decrease with small apertures.

3.Clearer imaging
Since the on-axis performance of achromatic lenses is not reduced by using a larger clear aperture, it is not necessary to "shrink" the volume of the optical system. "Shrinking" the aperture refers to reducing the aperture of the lens, for example through a pinhole or aperture, to improve the overall performance of the lens. By making full use of the entire clear aperture, achromatic lenses and achromatic lens systems will achieve faster speeds, higher performance, and more powerful functions than equivalent systems using monolithic lenses.

 

As the achromatic lens supplier, JUKA Optical can manufacture achromatic doublet lens, achromatic triplet lens and achromatic cylindrical lens. If you need achromatic optical lens, please contact JUKA Optical.

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