A lenticular lens is an array of magnifying lenses, designed so that when viewed from slightly different angles, different images are magnified.[1][failed verification – see discussion] The most common example is the lenses used in lenticular printing, where the technology is used to give an illusion of depth, or to make images that appear to change or move as the image is viewed from different angles.
Applications
Lenticular printing
Main article: Lenticular printing
Lenticular printing is a multi-step process consisting of creating a lenticular image from at least two existing images, and combining it with a lenticular lens. This process can be used to create various frames of animation (for a motion effect), offsetting the various layers at different increments (for a 3D effect), or simply to show a set of alternate images which may appear to transform into each other.
Corrective lenses
Lenticular lenses are sometimes used as corrective lenses for improving vision. A bifocal lens could be considered a simple example.
Lenticular eyeglass lenses have been employed to correct extreme hyperopia (farsightedness), a condition often created by cataract surgery when lens implants are not possible. To limit the great thickness and weight that such high-power lenses would otherwise require, all the power of the lens is concentrated in a small area in the center. In appearance, such a lens is often described as resembling a fried egg: a hemisphere atop a flat surface. The flat surface or "carrier lens" has little or no power and is there merely to fill up the rest of the eyeglass frame and to hold or "carry" the lenticular portion of the lens. This portion is typically 40 mm (1.6 in) in diameter but may be smaller, as little as 20 mm (0.79 in), in sufficiently high powers. These lenses are generally used for plus (hyperopic) corrections at about 12 diopters or higher. A similar sort of eyeglass lens is the myodisc, sometimes termed a minus lenticular lens, used for very high negative (myopic) corrections. More aesthetic aspheric lens designs are sometimes fitted.[2] A film made of cylindrical lenses molded in a plastic substrate as shown in above picture, can be applied to the inside of standard glasses to correct for diplopia. The film is typically applied to the eye with the good muscle control of direction. Diplopia (also known as double vision) is typically caused by a sixth cranial nerve palsy that prevents full control of the muscles that control the direction the eye is pointed in. These films are defined in the number of degrees of correction that is needed where the higher the degree, the higher the directive correction that is needed.
Lenticular screens
Screens with a molded lenticular surface are frequently used with projection television systems. In this case, the purpose of the lenses is to focus more of the light into a horizontal beam and allow less of the light to escape above and below the plane of the viewer. In this way, the apparent brightness of the image is increased.
Ordinary front-projection screens can also be described as lenticular. In this case, rather than transparent lenses, the shapes formed are tiny curved reflectors.
3D television
As of 2010, a number of manufacturers were developing auto-stereoscopic high definition 3D televisions, using lenticular lens systems to avoid the need for special spectacles. One of these, Chinese manufacturer TCL, was selling a 42-inch (110 cm) LCD model—the TD-42F—in China for around US$20,000.[3]
Lenticular color motion picture processes
Lenticular lenses were used in early color motion picture processes of the 1920s such as the Keller-Dorian system and Kodacolor. This enabled color pictures with the use of merely monochrome film stock.[4]
Angle of view of a lenticular print
The angle of view of a lenticular print is the range of angles within which the observer can see the entire image. This is determined by the maximum angle at which a ray can leave the image through the correct lenticule.
Angle within the lens
Sq3d-angle-refraction.gif
The diagram at right shows in green the most extreme ray within the lenticular lens that will be refracted correctly by the lens. This ray leaves one edge of an image strip (at the lower right) and exits through the opposite edge of the corresponding lenticule.
Definitions
R is the angle between the extreme ray and the normal at the point where it exits the lens,
p is the pitch, or width of each lenticular cell,
r is the radius of curvature of the lenticule,
e is the thickness of the lenticular lens
h is the thickness of the substrate below the curved surface of the lens, and
n is the lens's index of refraction.
Calculation
\( R=A-\arctan\left({p \over h}\right), \)
where
\( A=\arcsin \left({p \over 2r}\right), \)
h=e-f is the distance from the back of the grating to the edge of the lenticule, and
\( f=r-\sqrt{r^2-\left({p \over 2}\right)^2}. \)
Angle outside the lens
Lr3d-angle-indice.gif
The angle outside the lens is given by refraction of the ray determined above. The full angle of observation O {\displaystyle O} O is given by
O=2(A-I),
where I I is the angle between the extreme ray and the normal outside the lens. From Snell's Law,
\( I=\arcsin \left({n\sin(R) \over n_a}\right) , \)
where \( n_a \approx 1.003 \) is the index of refraction of air.
Example
Consider a lenticular print that has lenses with 336.65 µm pitch, 190.5 µm radius of curvature, 457 µm thickness, and an index of refraction of 1.557. The full angle of observation O {\displaystyle O} O would be 64.6°.
Rear focal plane of a lenticular network
The focal length of the lens is calculated from the lensmaker's equation, which in this case simplifies to:
F={r \over n-1}, \)
where F is the focal length of the lens.
The back focal plane is located at a distance BFD from the back of the lens:
\( BFD=F- {e \over n}. \)
A negative BFD indicates that the focal plane lies inside the lens.
In most cases, lenticular lenses are designed to have the rear focal plane coincide with the back plane of the lens. The condition for this coincidence is BFD=0, or
\( e={nr \over n-1}. \)
This equation imposes a relation between the lens thickness e and its radius of curvature r.
Example
The lenticular lens in the example above has focal length 342 µm and back focal distance 48 µm, indicating that the focal plane of the lens falls 48 micrometers behind the image printed on the back of the lens.
See also
Fresnel lens, a different 'flat' lens technology
Integral imaging
Microlens
References
"Lenticular, how it works". Lenstar.org. Archived from the original on 3 May 2016. Retrieved 25 May 2017.
Jalie, Mo (2003). Ophthalmic Lenses and Dispensing. Elsevier Health Sciences. p. 178. ISBN 0-7506-5526-7.
"Give Me 3D TV, Without The Glasses". Archived from the original on 13 February 2010. Retrieved 6 May 2010.
"Lenticular films on Timeline of Historical Film Colors". Archived from the original on 9 July 2014. Retrieved 29 June 2014.
Bartholdi, Paul (1997). "Quelques notions d'optique" (in French). Observatoire de Genève. Retrieved 19 December 2007.
Soulier, Bernard (2002). "Principe de fonctionnement de l'optique lenticulaire" (in French). Séquence 3d. Retrieved 22 December 2007.
Okoshi, Takanori Three-Dimensional Imaging Techniques Atara Press (2011), ISBN 978-0-9822251-4-1.
vte
Stereoscopy
Perception
Binocular rivalry Binocular vision Chromostereopsis Convergence insufficiency Correspondence problem Peripheral vision Depth perception Epipolar geometry Kinetic depth effect Stereoblindness Stereopsis Stereopsis recovery Stereoscopic acuity
Display
technologies
Active shutter 3D system Anaglyph 3D Autostereogram Autostereoscopy Bubblegram ChromaDepth Head-mounted display Holography Integral imaging Lenticular lens Multiscopy Parallax barrier Parallax scrolling Polarized 3D system Specular holography Stereo display Stereoscope Vectograph Virtual retinal display Volumetric display Wiggle stereoscopy
Other
technologies
2D to 3D conversion 2D plus Delta 2D-plus-depth Computer stereo vision Multiview Video Coding Parallax scanning Pseudoscope Stereo photography techniques Stereoautograph Stereoscopic depth rendition Stereoscopic rangefinder Stereoscopic spectroscopy Stereoscopic Video Coding
Product
types
3D camcorder 3D film 3D television 3D-enabled mobile phones 4D film Blu-ray 3D Digital 3D Stereo camera Stereo microscope Stereoscopic video game Virtual reality headset
Notable
products
AMD HD3D Dolby 3D Fujifilm FinePix Real 3D Infitec MasterImage 3D Nintendo 3DS
New 3DS Nvidia 3D Vision Panavision 3D RealD 3D Sharp Actius RD3D View-Master XpanD 3D
Miscellany
Stereographer Stereoscopic Displays and Applications
Hellenica World - Scientific Library
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