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Plane Mirrors
Published in Abdul Al-Azzawi, Light and Optics, 2018
Consider a point source of light placed a distance S in front of a plane mirror at a location O, as shown in Figure 8.2. The distance S is called the object distance. Light rays leaving the light source are incident on the mirror and reflect from the mirror. After reflection, the rays diverge, but they appear to the viewer to come from a point I located “behind” the mirror at distance S’. Point I is called the image of the object at O. The distance S’ is called the image distance. Images are formed in the same way for all optical components, including mirrors and lenses. Images are formed at the point where rays of light actually intersect at the point from which they appear to originate. Solid lines represent the light coming from an object or a real image. Dashed lines are drawn to represent the light coming from an imaginary image. Figure 8.2 shows that the rays appear to originate at I, which is behind the mirror. This is the location of the image. Images are classified as real or virtual. A real image is one in which light reflects from a mirror or passes through a lens and the image can be captured on a screen. A virtual image is one in which the light does not really pass through a mirror or lens but appears either behind the mirror or in front of the lens. The virtual image cannot be displayed on a screen.
Plane Mirrors
Published in Abdul Al-Azzawi, Photonics, 2017
Consider a point source of light placed a distance S in front of a plane mirror at a location O, as shown in Figure 8.2. The distance S is called the object distance. Light rays leaving the light source are incident on the mirror and reflect from the mirror. After reflection, the rays diverge, but they appear to the viewer to come from a point I located “behind” the mirror at distance S’ Point I is called the image of the object at O. The distance S’ is called the image distance. Images are formed in the same way for all optical components, including mirrors and lenses. Images are formed at the point where rays of light actually intersect at the point from which they appear to originate. Solid lines represent the light coming from an object or a real image. Dashed lines are drawn to represent the light coming from an imaginary image. Figure 8.2 shows that the rays appear to originate at I,which is behind the mirror. This is the location of the image. Images are classified as real or virtual. A real image is one in which light reflects from a mirror or passes through a lens and the image can be captured on a screen. A virtual image is one in which the light does not really pass through a mirror or lens but appears either behind the mirror or in front of the lens. The virtual image cannot be displayed on a screen.
Light Microscopy
Published in Thomas A. Barber, Control of Particulate Matter Contamination in Healthcare Manufacturing, 1999
In a compound magnifying system, magnification takes place in two or more stages. A second lens may be placed so that it produces a further magnified image of the real image produced by the double convex lens shown in Figure 10.3 The total magnification is the product of the magnification of the first lens and the second lens. This is the basic principle of a compound magnifying system. The analyst looks at the primary image with a lens that produces an enlarged secondary image or virtual image. The brain sees this virtual image, rather than the real image formed on the retina; there is no real image at the point where the virtual image appears to be (Figure 10.3).
Liquid crystal technology for vergence-accommodation conflicts in augmented reality and virtual reality systems: a review
Published in Liquid Crystals Reviews, 2021
Instead of correcting the refractive error of the eyes, another strategy for enhancing the image sharpness and solving the VAC challenge is to lower the spatial resolutions of the virtual image and the real object, which leads to the magnification of the virtual image and the image of the real object (optical zoom-in). An optical imaging system is said to be diffraction-limited when a point-source object is converted to an ideal point in the image plane thus, perfectly spherical waves propagate in the optical image system without wavefront aberrations (e.g. no refractive errors) [38]. In a diffraction-limited system, an object with fine details can be resolved. The typical contrast of the optical image system (equivalent to the resolving capability) as a function of spatial resolution is illustrated in Figure 23. The black solid line represents the contrast versus spatial resolution in a diffraction-limited image system. We consider the eyes as an example of a system with aberration (i.e. refractive errors), the contrast curve drops quickly, especially for the location of the high spatial resolution (green line in Figure 23). This means that an eye can see a blurred image when the image contains exquisite details. The typical engineering strategy for correcting the refractive error of the eye is to add corrected lenses or prescription lenses (i.e. compensation of focusing error) so that the green line is close to the black line. Another engineering strategy is to magnify the image or lower the spatial resolution of the images. Researchers have demonstrated this by implementing an optical zoom function in the AR system using two tunable LC lenses [43,44]. Two LC lenses are separated by a certain distance to achieve the optical zoom function (Figure 24). When the two LC lenses are turned off, the virtual image is set to coincide with a real object, as shown in Figure 24(a). When two LC lenses are operated together, the virtual image plane can be fixed, and the size of the virtual image is magnified, as shown in Figure 24(b). The experimental demonstrations in the literature are shown in Figure 24(c,d). This concept is also applicable for magnifying real objects when LC lenses are placed at appropriate locations. Furthermore, this concept can be transformed into a time-multiplexing foveated display with two virtual images at different magnifications.