The complexity of optical elements comes from the difference between simplified elements used for simulation and real optical elements that comes with limitation and defaults. Doublets are a way to minimise some optical default in your optical system, lets learn more about them.
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A doublet lens is a assembly of two lenses of different material cemented together. Every optical material is subject to chromatic dispersion, defined by their Vd value. This chromatic dispersion will cause scattering of a signal at different wavelengths. The objective of manufacturing a doublet lens is two use to “complementary” dispersing material to compensate the chromatic dispersion and have a resulting doublet lens with identical focusing power on it’s whole wavelength range. These lenses are also called : achromatic lens, meaning lens with no chromatic dispersion, achromatic doublet is also a common name. Achromatic doublets are usually made out of two kinds of glass : Flint glass and Crown glass. A concave lens will be made usually in Flint glass and a convex lens in Crown glass with similar radius of curvature so they can easily be cemented together. Flint glass are high refringent glass, meaning that they will cause a high scattering of light rays according to their wavelength. While Crown glass are low dispersion glass. It is easy to find is a glass is Flint or Crown as its name will include a “F” for Flint or a K for Crown (for example in the most common : N-BK7 ( Schott) or H-K9L (CDGM). Cementing of the two lenses to form the doublet, is done with very thin, optically neutral glue material and hardened with UV light. Positioning of both lenses during the cementing and the hardening of the cementing medium is the key factor to the success of the manufacturing of the achromatic lens. In order to increase optical transmission of the lens, it is not unusual to have a antireflect coating added on external surfaces after the cementing. Doublets improve the optical quality of a lens reducing both chromatic dispersion and spherical aberration. Their were first discovered in the XVIII century in England for telescopes applications. Currently many imaging applications in the visible are using doublets : Designing of a a doublet lens is not very difficult but need the experience of an optician to better understand the material possibilities and define the surface shapes of the two optics. Design deliverable will be a separate drawing including optical glass selection for each component and eventually an assembly drawing of the doublet that will state the coating requirements and may also request blackening of the doublet edge. optec are exported all over the world and different industries with quality first. Our belief is to provide our customers with more and better high value-added products. Let's create a better future together. Once the design completed, precision optics manufacturers with the experience and ability to assemble doublet lenses, will be able to quote for its manufacturing.What is a doublet lens ?
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In the realm of precision optics, achromatic lenses have become indispensable tools, allowing scientists, engineers, and photographers to achieve high-quality imaging and focus correction. These lenses are designed to minimize chromatic aberration, a common optical phenomenon that causes color fringing and reduces image sharpness. Achromatic lenses are widely used in various applications, from astronomical telescopes to high-resolution microscopes, ensuring that light dispersion is effectively corrected. In this article, we will delve into the principles, design, and applications of achromatic lenses, highlighting their vital role in advancing modern optics.
Chromatic aberration occurs due to the different wavelengths of light refracting at varying angles when passing through an optical lens. This dispersion leads to color fringing and reduces the sharpness and clarity of the resulting image. Blue light, with its shorter wavelength, is refracted more than red light, which has a longer wavelength. The result is a visible spectrum of colors at the edges of objects, making them appear blurred and distorted.
The quest to overcome chromatic aberration led to the development of Achromatic Lenses in the early 18th century. Famed mathematician and physicist Sir Isaac Newton was among the first to observe and attempt to correct this issue. However, it was not until the late 18th century that notable opticians such as John Dollond made significant progress in designing Achromatic Lenses.
Achromatic lenses are constructed using a combination of two or more lens elements made from different types of glass. Typically, a positive lens made from a crown glass and a negative lens made from a flint glass are combined to form an achromatic lens pair. The crown glass element has a lower refractive index, while the flint glass element has a higher dispersion rate. By carefully selecting the curvature and thickness of these elements, the lens designer can precisely cancel out the chromatic aberration at a specific wavelength or over a broad spectrum, depending on the application.
There are two main types of achromatic lenses: the achromatic doublet and the achromatic triplet. The achromatic doublet consists of two lens elements, while the achromatic triplet utilizes three. The triplet design offers better correction of chromatic aberration and spherical aberration, but it is more challenging to manufacture and align accurately.
Telescopes: Achromatic Lenses play a crucial role in astronomical telescopes, allowing astronomers to observe celestial objects with enhanced clarity and color fidelity.
Microscopes: In microscopy, Achromatic Lenses improve the resolution and minimize color distortion, enabling researchers to study minute biological structures with precision.
Photography: Achromatic Lenses are employed in high-quality camera lenses to produce sharp and well-defined images, free from chromatic aberrations.
Laser Systems: These lenses are used in laser systems to focus and direct laser beams without compromising their coherence and color purity.
While Achromatic Lenses significantly reduce chromatic aberration, they are not perfect. In some cases, residual chromatic aberration may remain, especially in lenses designed for broader spectral ranges. Additionally, Achromatic Lenses are sensitive to off-axis aberrations, which can impact image quality in wide-angle applications.
Achromatic Lenses have revolutionized the field of optics by mitigating the adverse effects of chromatic aberration, making them invaluable tools for achieving precise imaging and focus correction. Their impact can be seen across various domains, from space exploration to medical research. As technology continues to advance, Achromatic Lenses will undoubtedly play an essential role in shaping the future of precision optics and imaging applications.
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