The use of aspheric lenses has two major advantages: one is to improve the imaging quality of the entire optical system; the other is to reduce the weight and size of the finished product. Advantages include a reduced number of back reflections that occur in the system resulting in higher total light transmission, reduced system heating when some kilowatt-level high power light is transmitted, advanced process technology reduces damage to subsurface layers, the spherical surface is precisely polished to improve the collimation accuracy.

These values for the depth of field, and the distribution of intensities in the three-dimensional diffraction pattern, are calculated for incoherently illuminated (or emitting) point sources where the numerical aperture of the condenser is greater than or equal to that of the objective. In general, the depth of field increases, up to a factor of 2, as the coherence of illumination increases (as the condenser numerical aperture approaches zero). However, the three-dimensional point spread function (PSF) with partially coherent illumination can depart in complex ways from that so far discussed when the aperture function is not uniform. In a number of phase-based, contrast-generating modes of microscopy, the depth of field may turn out to be unexpectedly shallower than that predicted from the equation above and may yield extremely thin optical sections.

Depthof fieldphotography settings

World-class Nikon objectives, including renowned CFI60 infinity optics, deliver brilliant images of breathtaking sharpness and clarity, from ultra-low to the highest magnifications.

Aspherical lenses can be freely adjusted in curvature and shape as required, allowing them to provide higher optical efficiency. This makes them the preferred choice in many application areas, such as laser systems, lighting systems, and optical sensors.

Aspheric lenses, on the other hand, can be manufactured in a variety of curvatures as needed, so problems such as spherical aberration, distortion, and peripheral astigmatism can be better corrected, making them better adaptable to various imaging needs.

spheric lenses are commonly used in a variety of optical systems to reduce aberrations and improve image quality. Here are some additional types of aspheric lenses:

Aspheric lenses are unique lenses that have a non-spherical curvature. They are widely used because they can provide higher-quality imaging effects when compared with traditional spherical lenses. In this article by Noni, we will introduce what are aspheric lenses from their basic definition, compare them to spherical lenses, explain their working principles, and processing methods, list their advantages and disadvantages, and highlight their applications.

Aspheric lenses provide higher-quality imaging and are correct for issues such as spherical aberration, distortion, and peripheral astigmatism. This makes them particularly suitable for applications requiring high-precision imaging, such as astronomy, medicine, and industry.

Our use of aspheric grinding CNC machine tools to produce lenses results in larger sizes, improved surface quality, and better maintenance of the M-square value of the input beam when compared to corresponding molded aspheric lenses. This technology is particularly suitable for small-batch production and product prototype manufacturing, thereby meeting the needs of diverse industries.

Mainly used in projectors, amplifiers, spotlights, and other projection and lighting fields. Two condenser lenses of the same focal length can be combined to form a system with half the focal length of a single lens. Primarily used in high-efficiency illumination systems, aspheric condensers feature excellent aberration correction.

Conventional lenses also produce distortion in the peripheral region. This is due to the shape of the lens limiting how much light can be bent. In contrast, aspheric lenses can freely adjust the curvature as needed, thereby eliminating distortion.

Depthof fieldphotography formula

Both spherical and aspheric lenses are common lens types, and the main difference between them is the curvature of the lens.

Aspheric lenses are designed to better correct spherical distortion, but they are also prone to other types of optical distortion, such as lateral astigmatism and longitudinal astigmatism.

Depthof fieldphotography aperture

These lenses can focus light at short focal lengths that cannot be achieved with spherical lenses. Generally, it is made of B270-ultra-clear glass, so it is convenient to realize the manufacture of complex surfaces that are not easy to grind. The design condition of this type of lens is infinity conjugate, and the design wavelength is 587.6nm (yellow helium line). Condenser lenses concentrate light into a projection beam.

Aspherical lenses offer many advantages over traditional spherical lenses, such as a more natural field of view and thinner and lighter designs. However, aspherical lenses also have some disadvantages, including:

Axial resolution, like horizontal resolution, is determined only by the numerical aperture of the objective (Figure 2), with the eyepiece merely magnifying the details resolved and projected into the intermediate image plane. Just as in classical photography, depth of field is determined by the distance from the nearest object plane in focus to that of the farthest plane also simultaneously in focus. In microscopy depth of field is very short and usually measured in units of microns. The term depth of focus, which refers to image space, is often used interchangeably with depth of field, which refers to object space.

CNC grinding technology achieves sub-micron level precision in lens manufacturing and allows for more complex designs of aspheric lenses. Additionally, it provides higher production efficiency and superior surface quality compared to other methods, reducing production costs while enhancing lens performance.

Shallow depthof field

Aspheric lens CNC grinding is a highly precise processing method that utilizes CNC machine tools to cut and process aspheric lenses from bulk materials, producing lenses with exceptional shape and surface quality. This technique is widely employed in modern optical manufacturing due to its ability to produce high-precision aspheric lenses.

The human eye can normally accommodate from infinity to about 25 centimeters, so that the depth of field can considerably greater than that given by the equation above when one observes the microscope image through the eyepieces. On the other hand, a video sensor or photographic emulsion lies in a thin fixed plane so that the depth of field and axial resolution using those sensors are given by the parameters in the equation. In these cases, the axial resolution is defined by convention as one-quarter of the distance between the first minima, above and below focus, along the axis of the three-dimensional diffraction image produced by the objective.

Since aspheric lenses can freely adjust their curvature as needed, they can add relatively larger apertures while maintaining high imaging quality. This means that aspherical lenses can provide a larger field of view and a wider field of view in a smaller size, making them particularly suitable for photography and video applications that require high resolution.

For the case where customized aspheric lenses are required, factors such as development cost, sample cost, batch price, and delivery cycle also need to be considered.

Aspheric lenses require more precise measurements and positioning, thus requiring more skilled operators during fabrication, installation, and adjustment.

Peripheral astigmatism is a common lens problem that produces bright or dark spots in the peripheral areas. This is due to the shape of the lens so that light is scattered in different directions. Aspherical lenses can eliminate marginal astigmatism by adjusting the curvature, thereby improving imaging.

Depthof fieldphotography

The industrial field also requires high-precision imaging to ensure product quality and efficiency. Aspheric lenses can provide more accurate imaging in applications such as automated manufacturing, machine vision, and laser imaging, thereby increasing production efficiency and reducing costs.

Depthof fieldphotography examples

Aspheric lenses have a more complex surface shape, are more susceptible to contamination and damage, and may require more frequent cleaning and maintenance.

Medical imaging also requires high-precision imaging to ensure accurate diagnosis and treatment. Aspherical lenses are widely used in the field of medical imaging, such as intraocular lenses in eye surgery, X-ray imaging systems, and MRI machines.

The radius of curvature varies everywhere on one of the surfaces with a height from the optical axis to minimize spherical aberration. The other side is convex or flat.

In digital and video microscopy, the shallow focal plane in the target of the camera tube or CCD, the high contrast achievable at high objective and condenser numerical apertures, and the high magnification of the image displayed on the monitor all contribute to reducing the depth of field. Thus, with video, we can obtain very sharp and thin optical sections, and can define the focal level of a thin specimen with very high precision.

Noni is a leading custom optics production and development company with extensive experience in the industry of optical components and systems. Since our establishment in 2014, we have been committed to providing exceptional services to our clients worldwide. Our team comprises experts who have been in the optics field since 2008, ensuring that we deliver top-quality products and reliable services to meet our client’s diverse needs.

Spherical lenses produce spherical aberration in the peripheral region. This means that when light rays pass through the lens, they will be focused on different points due to different angles and positions, resulting in image distortion. Aspherical lenses can correct spherical aberration through complex curves, thus providing more accurate imaging effects.

If have particular specifications for aspheric lens or other optics in customization, or you need support in the R&D and manufacturing of tailored optics of higher accuracy and special sizes for your projects or applications, Noni is ready to be a reliable helper with our custom abilities to exceed your expectations via the one-package solution.

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While optical aspheric surface replication molding technology can achieve high precision and excellent surface quality, it may have limitations in terms of replication accuracy and surface quality. Therefore, it may not be suitable for all types of aspheric lens manufacturing needs. Nonetheless, when used appropriately, this technology serves as a valuable solution for various industries seeking to produce high-quality aspheric lenses efficiently and cost-effectively.

When selecting an aspheric lens, it is necessary to consider aspheric lenses’ advantages and disadvantages to determine which lens is most suitable for a specific application.  Based on our experience of decades, the key factors into consideration include volume, quality, and cost.  Here, you can check the requirements for different types of lenses as follows:

This article shows basic knowledge about aspheric lens and we hope it can not only offer you a complete explanation about what is a aspheric lens, but also give you some inspiration about its benefits and applications.

Spherical lenses have the same curvature, while aspheric lenses have different curvatures. Due to the fixed surface curvature of spherical lenses, they only provide the best image quality in certain situations. Specifically, spherical lenses provide optimal imaging when the object is located at the infinity of the spherical lens.

At high numerical apertures of the microscope, depth of field is determined primarily by wave optics, while at lower numerical apertures, the geometrical optical circle of confusion dominates the phenomenon. Using a variety of different criteria for determining when the image becomes unacceptably sharp, several authors have proposed different formulas to describe the depth of field in a microscope. The total depth of field is given by the sum of the wave and geometrical optical depths of fields as:

Due to its high-precision imaging and targeted design, aspheric lenses are widely used in many application fields. Some of these application areas include:

An aspheric lens is a type of lens that differs from the traditional spherical or cylindrical shape. It boasts complex and asymmetrical curves that allow it to correct common lens problems like distortion, peripheral astigmatism, and spherical aberration.

In short, an aspheric lens is a lens that provides higher-quality imaging. They adjust curvature and shape to correct problems such as spherical aberration, distortion, and peripheral astigmatism and have the advantages of greater precision, larger aperture, and improved efficiency. Due to its wide range of applications, aspheric lenses will be more and more widely used in the future.

Shallow depthof fieldphotography

Optical aspheric replication molding technology is a cost-effective and efficient method for manufacturing high-quality aspheric lenses. This technique involves transferring the surface of a master mold onto a base, resulting in the transformation of a spherical surface into an aspherical one. Unlike other aspheric surface processing methods, this technology requires minimal equipment and eliminates the need for substrate polishing, making it ideal for the mass production of sub-mirrors with identical specifications or spliced mirror surfaces.

Astronomy is one of the most widely used fields of aspheric lenses. Telescopes and astronomical telescopes require high-precision imaging to observe galaxies and stars, and aspheric lenses can correct spherical aberration and distortion to provide higher-quality imaging.

When considering resolution in optical microscopy, a majority of the emphasis is placed on point-to-point lateral resolution in the plane perpendicular to the optical axis (Figure 1). Another important aspect to resolution is the axial (or longitudinal) resolving power of an objective, which is measured parallel to the optical axis and is most often referred to as depth of field.

The greatest advantage of precision hot pressing is its ability to produce high-precision and smooth-surfaced aspheric lenses with sub-micron-level accuracy. Although the use of high-precision metal molds and materials that can withstand high temperatures and pressure may result in higher production costs. Furthermore, this method is ideal for producing relatively simple aspheric lenses due to the simplicity of their shapes.

Where d(tot) represents the depth of field, λ is the wavelength of illuminating light, n is the refractive index of the medium (usually air (1.000) or immersion oil (1.515)) between the coverslip and the objective front lens element, and NA equals the objective numerical aperture. The variable e is the smallest distance that can be resolved by a detector that is placed in the image plane of the microscope objective, whose lateral magnification is M. Using this equation, depth of field (d(tot)) and wavelength (λ) must be expressed in similar units. For example, if d(tot) is to be calculated in micrometers, λ must also be formulated in micrometers (700 nanometer red light is entered into the equation as 0.7 micrometers). Notice that the diffraction-limited depth of field (the first term in the equation) shrinks inversely with the square of the numerical aperture, while the lateral limit of resolution is reduced in a manner that is inversely proportional to the first power of the numerical aperture. Thus, the axial resolution and thickness of optical sections that can be attained are affected by the system numerical aperture much more so than is the lateral resolution of the microscope.

We provide off-axis paraboloid, ellipsoid, hyperboloid, and other aspheric lenses. At the same time, we can also provide aspheric lenses of various infrared materials, such as germanium, zinc selenide, zinc sulfide, and more.

Depth of focus varies with numerical aperture and magnification of the objective, and under some conditions, high numerical aperture systems (usually with higher magnification power) have deeper focus depths than do those systems of low numerical aperture, even though the depth of field is less (see Table 1). This is particularly important in photomicrography because the film emulsion or digital camera sensor must be exposed or illuminated in a plane that falls within the focus region. Small errors made to focus at high magnification are not as critical as those made with very low magnification objectives. Table 1 presents calculated variations in the depth of field and image depth in the intermediate image plane in a series of objectives with increasing numerical aperture and magnification.

Aspheric lenses have several advantages over conventional lenses, including improved accuracy in the light collection and the ability to eliminate spherical chromatic aberration. Additionally, they have a simple structure that can replace multi-lens systems, reducing weight, volume, and cost. Unlike traditional lenses, aspheric lenses have varying radii of curvature from the center to the surface’s edge. This unique feature enables them to eliminate errors that standard lenses cannot.

Precision hot pressing is a highly precise manufacturing method that enables the mass production of aspheric lenses with exceptional accuracy and surface quality. By placing the lens material into a heated metal mold and applying high pressure at elevated temperatures, this technique allows for complete control over the shape and surface quality of the resulting lenses.

This interchange of nomenclature can lead to confusion, especially when the terms are both used specifically to denote depth of field in microscope objectives. The geometric image plane might be expected to represent an infinitely thin section of the specimen, but even in the absence of aberrations, each image point is spread into a diffraction figure that extends above and below this plane. The Airy disk, a basic unit of the diffraction pattern produced by the microscope objective, represents a section through the center of the intermediate image plane. This increases the effective in-focus depth of the Z-axis Airy disk intensity profile that passes through slightly different specimen planes.

Due to their complex design and manufacturing process, aspheric lenses are usually more expensive than traditional spherical lenses.

Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.