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144:) allows more light to be captured than would be possible with other spherical lenses. This makes ball lenses particularly suited for coupling light from a laser to a fiber-optic cable or a detector, or from one fiber-optic cable to another, or for micro-optical systems. In addition, ball lenses are omnidirectional, which eases alignment of optical couplings over other types of lens because all that is necessary is to keep everything centered. Ball lenses for optical coupling are typically small, ranging from 5 millimeters down to as tiny as 110 micrometers, with focal lengths ranging from 100 to 250 micrometers. They tend to be made of high-quality
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just outside the surface. From there the light diverges, flipping both the right/left and the top/bottom axes. Thus, if the camera is too close to the ball lens, the background around the ball will be completely blurred. The further the camera lies from the ball lens, the better the background will come into focus.
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The first lenses were likely spherical or cylindrical glass containers filled with water, which people noticed had the ability to focus light. Simple convex lenses have surfaces that are small sections of a sphere. A ball lens is just a simple lens where the surfaces' radii of curvature are equal to
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A ball lens refracts light at the interface between its surface and its surroundings. Light from a collimated source is bent into a converging cone. The rays travel in straight lines within the lens, and then are bent again when they exit, converging to a focal point which is typically just outside
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Ball lenses are used by photographers to take novel extreme wide-angle photos. The ball lens is placed fairly close to the camera and the camera's own lenses are used to focus an image through it. The light is focused to a small spot at the output surface of the ball, and reaches its focal point
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is a ball lens that has a radially varying index of refraction that follows a certain profile. A Luneberg lens has foci outside the lens and can perfectly image a spherical object. Luneberg lenses designed for radio wavelengths are used in some radar systems and radio antennas.
240:, a scientific instrument which records the brightness of sunlight by burning the surface of a paper card bent around the sphere. The device, itself fixed, records the apparent motion and intensity of the sun across the sky, burning an image of the sun's motion across the card.
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For materials with refractive index greater than 2, objects at infinity form an image inside the sphere. The image is not directly accessible; the closest accessible point is on the sphere's surface directly opposite the source of light.
196:, however. A 3 mm ball lens can magnify an image 100 to 200 times, while a 1 mm ball will produce images 200 to 350 times larger than their actual size. In addition, because they are omnidirectional and have large
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In addition, a ball lens can be used on the output side of a fiber-optic cable to collimate the output back into a beam. In this way, two lenses placed back to back can be used to couple two cables to one another.
132:(BFL), the distance from the back surface of the lens to the focal point. Ball lenses have the shortest possible focal length for a given lens diameter (for a spherical lens). Due to the
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of light placed at the focal point will produce a collimated beam emanating from the opposite side of the lens, and the lens's large ratio of diameter to focal length (large
73:. For most glassy materials the focal point is only slightly beyond the surface of the ball, on the side opposite to where the rays entered. Ball lenses have extremely high
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Unlike other types of lens, the image-forming properties of a ball lens are omnidirectional (independent of the direction being imaged). This effect is exploited in the
220:. Ball lenses have found uses in many micro-imaging applications, ranging from electron microscopes to single-lens smart-phone microscopes to nano-microscopy.
136:, this allows light from a collimated beam to be focused to smaller diameters than could be achieved with other spherical lenses. Similarly, a
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they produce in a laser beam, they are ideally suited to focus nearly all of the light from a laser into an optical fiber core. The
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of the fiber and lens need to match. The fiber can usually be placed in direct contact with the ball, helping to ease alignment.
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with refractive indices ranging from 1.5 to 1.8. Higher indices produce a shorter focal length for a given size ball.
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used a small ball lens to create a single-lens microscope with 300Ă— magnification, allowing the first observation of
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Ball lenses are often used in fiber optics. Due to their short focal lengths and the subsequently small
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A ruby ball lens atop a green laser pointer. The 520 nm light is absorbed and remitted as red
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The focal length of a ball lens is a function of its refractive index and its diameter. The
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Advancements in
Optical Methods, Digital Image Correlation, & Micro- and Nanomechanics
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on both sides, and diameter equal to twice the radius of curvature. The same
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may be applied to analyze its imaging characteristics as for other lenses.
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used for making lenses have refractive indices between 1.4 and 1.6; only
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Ball lenses are rarely used for imaging applications due to their high
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for their focal length, ball lenses convert such images into
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Lin, Ming-Tzer; Furlong, Cosme; Hwang, Chi-Hung (2023).
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As a lens, a transparent sphere of any material with
357:. Cambridge University Press. pp. 256–257.
504:"Seven tips for awesome lensball photography"
252:Landscape photograph taken through a lensball
128:(EFL) of a ball lens is much larger than the
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370:Light and Optics: Principles and Practice
279:have a refractive index of 2 or higher (
402:. Vol. 4. Springer. pp. 1–10.
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212:as well as in the near field. In 1677,
518:– via australianphotography.com.
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69:) bends parallel rays of light to a
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208:effects and can be imaged in the
85:compared to conventional lenses.
428:Bond, Simon (22 December 2016).
372:. CRC Press. pp. 9-36–9-37.
23:A photograph through a ball lens
117:the radius of the lens itself.
430:"Create glass ball landscapes"
39:. Formally, it is a bi-convex
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415:Encyclopedia of reproduction
413:Skinner, Michael K. (2016).
355:Fundamentals of Micro-Optics
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434:Digital-photography-school
266:Extremely refractive glass
232:A Campbell–Stokes recorder
387:. CRC Press. p. 244.
368:Al-Azzawi, Abdul (2007).
238:Campbell–Stokes recorder
417:. Elsevier. p. 66.
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508:Australian Photography
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340:References
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