Prior to use, carefully clean the optical flat and surface requiring measurement. The surface being measured must be reflective to view interference fringes. A monochromatic light source must be used to accurately determine flatness with an optical flat. Place a sheet of lens tissue onto the surface requiring inspection. Physically place the optical flat onto the lens tissue covering the surface requiring measurement. While relieving some of the optical flat weight, gently pull the lens tissue out from between the two surfaces. Place a finger on the center of the optical flat and press down to remove some of the air trapped between the surfaces. The visual curvature of the interference fringes (light bands), relative to a parallel straight reference line, indicate the high and low deviation from the flat plane. If one band crosses the reference line, the surface is one light band “out-of-flat”. If two bands cross the reference line, the surface is two light bands out-of-flat. The user’s judgement of the degree of band curvature is a drawback with this method of measurement. The initial light band pattern indicates the total deviation from the lapped plane and nothing about the direction of deviation (convex or concave). Additional technique with the optical flat must be employed to determine if the surface deviates up (convex) or down (concave).

Eugène Estanave experimented with integral photography, exhibiting a result in 1925 and publishing his findings in La Nature. After 1930 he chose to continue his experiments with pinholes replacing the lenticular screen.[11]

The camera obscura or pinhole image is a natural optical phenomenon. Early known descriptions are found in the Chinese Mozi writings (circa 500 BCE)[2] and the Aristotelian Problems (circa 300 BCE – 600 CE).[3]

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Up to a certain point, the smaller the hole, the sharper the image, but the dimmer the projected image. Optimally, the size of the aperture should be 1/100 or less of the distance between it and the projected image.

Lapmaster offers a standard line of round optical flats from 1” to 12” diameter supplied with a protective case. Each size optical flat is available in three accuracy’s, 1/2, 1/5 and 1/10 of a light band. The standard optical flats are accurate on both faces, but single side accurate optical flats are available by request. The accuracy simply indicates the actual measured flatness across the diameter of the optical flat. In other words, the optical flat accuracy is in fact the measured inaccuracy. The more accurate optical flats require greater manufacturing time and are thus more expensive.

According to inventor William Kennedy Dickson, the first experiments directed at moving pictures by Thomas Edison and his researchers took place around 1887 and involved "microscopic pin-point photographs, placed on a cylindrical shell". The size of the cylinder corresponded with their phonograph cylinder as they wanted to combine the moving images with sound recordings. Problems arose in recording clear pictures "with phenomenal speed" and the "coarseness" of the photographic emulsion when the pictures were enlarged. The microscopic pin-point photographs were soon abandoned.[10] In 1893 the Kinetoscope was finally introduced with moving pictures on celluloid film strips. The camera that recorded the images, dubbed Kinetograph, was fitted with a lens.

Pinholes (homemade or commercial) can be used in place of the lens on an SLR. Use with a digital SLR allows metering and composition by trial and error, and is effectively free, so is a popular way to try pinhole photography.[14]

This may be shortened to: d = 0.0366 f {\displaystyle d=0.0366{\sqrt {f}}} (When d and f in millimetres and λ = 550 nm = 0.00055 mm, corresponding to yellow-green.)

Pinhole cameras can be handmade by the photographer for a particular purpose. In its simplest form, the photographic pinhole camera can consist of a light-tight box with a pinhole in one end, and a piece of film or photographic paper wedged or taped into the other end. A flap of cardboard with a tape hinge can be used as a shutter. The pinhole may be punched or drilled using a sewing needle or small diameter bit through a piece of tinfoil or thin aluminum or brass sheet. This piece is then taped to the inside of the light-tight box behind a hole cut through the box. A cylindrical container with one end completely open, and the closed has a hole drilled in can then be made into a pinhole camera.

A pinhole camera is a simple camera without a lens but with a tiny aperture (the so-called pinhole)—effectively a light-proof box with a small hole in one side. Light from a scene passes through the aperture and projects an inverted image on the opposite side of the box, which is known as the camera obscura effect. The size of the images depends on the distance between the object and the pinhole.

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Ibn al-Haytham (965–1039), an Arab physicist also known as Alhazen, described the camera obscura effect. Over the centuries others started to experiment with it, mainly in dark rooms with a small opening in shutters, mostly to study the nature of light and to safely watch solar eclipses.[5]

Pinhole cameras with CCDs (charge-coupled devices) are sometimes used for surveillance because they are difficult to detect.

The term "pin-hole" in the context of optics was found in James Ferguson's 1764 book Lectures on select subjects in mechanics, hydrostatics, pneumatics, and optics.[7][8]

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Pinhole cameras can also be constructed by replacing the lens assembly in a conventional camera with a pinhole. In particular, compact 35 mm cameras whose lens and focusing assembly have been damaged can be reused as pinhole cameras—maintaining the use of the shutter and film winding mechanisms. As a result of the enormous increase in f-number, while maintaining the same exposure time, one must use a fast film in direct sunshine.

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Pinhole cameras can be constructed with a sliding film holder or back so the distance between the film and the pinhole can be adjusted. This allows the angle of view of the camera to be changed and also the effective f-stop ratio of the camera. Moving the film closer to the pinhole will result in a wide angle field of view and shorter exposure time. Moving the film farther away from the pinhole will result in a telephoto or narrow-angle view and longer exposure time.

Lapmaster provides a service for reconditioning used optical flats. The maximum capability is 16” diameter, but 12” diameter optical flats are the largest that can currently be certified. Lapmaster uses a 12” diameter “master optical flat” that has been certified for accuracy by NIST (National Institute for Standards and Testing. Large chips, fractures and deep surface damage cannot be repaired.

A common use of pinhole photography is to capture the movement of the sun over a long period of time. This type of photography is called solarigraphy. Pinhole photography is used for artistic reasons, but also for educational purposes to let pupils learn about, and experiment with, the basics of photography.

The interior of an effective pinhole camera is black to avoid any reflection of the entering light onto the photographic material or viewing screen.[13]

This 8-1/2” by 11” lint free cleaning tissue is sold in packs of 500 sheets. This is the best material for cleaning optical flats and to place between the optical flat and a polished surface during set-up for the measurement. This tissue will not scratch the optical flat or polished surface and will not leave any lint particles when carefully pulled from between the two surfaces.

Lapmaster offers two sizes of reflection stand for use with the CP style monochromatic light units. The smaller unit supports the CP-2 and a 6” diameter optical flat. The large reflection stand supports the CP-1 and the customers choice of 6”, 8”, 10” or 12” diameter optical flat.

In the 1970s, Young measured the resolution limit of the pinhole camera as a function of pinhole diameter[18] and later published a tutorial in The Physics Teacher.[19] Partly to enable a variety of diameters and focal lengths, he defined two normalized variables: resolution limit divided by the pinhole radius, and focal length divided by the quantity s2/λ, where s is the radius of the pinhole and λ is the wavelength of the light, typically about 550 nm. His results are plotted in the figure.

The reflection stand consists of a fabricated polypropylene plastic housing containing an angle adjustable glass-viewing mirror. The front and top surface of the case is made from clear acrylic plastic. The stand works by supporting an optical flat above a mirror that is angled towards the clear acrylic front viewing panel of the unit. The appropriate size monochromatic light unit is placed on a step integral in the reflection stand with the diffusing lens overhanging the clear acrylic top surface of the reflection stand. A component requiring measurement is placed on top of the optical flat with its polished surface in contact with the flat. The only stress on the component is caused by its own weight. The interference fringe pattern reflects down to the mirror and is viewed through the clear front panel.

Non-standard sizes (16” diameter maximum), shapes (square or rectangular) and “donut” type (flat has a hole machined in its center) optical flats are available from Lapmaster.

The first to apply wave theory to the problem was Lord Rayleigh in 1891. But due to some incorrect and arbitrary deductions he arrived at:[17]

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(Where d is the pinhole diameter, f is the distance from pinhole to image plane or “focal length” and λ is the wavelength of light.)

For a pinhole-to-film distance of 1 inch or 25.4 mm, this works out to a pinhole of 0.185 mm (185 microns) in diameter. For f= 50 mm the optimal diameter is 0.259 mm.

All objects radiate energy, but some wavelengths within the electromagnetic spectrum are invisible. Detectors in an infrared camera capture a particular range ...

The aba company was founded in 1898 under the name "Messwerkzeugfabrik Alig & Baumgärtel Aschaffenburg", hence the initials aba. Today, the aba Grinding Technologies is exclusively focused on the advancement and production of precision surface and profile grinding machines.

A reflection stand is a devise used to allow an inspector the ability to view interference fringe patterns of a measured surface that is placed on the top surface of the optical flat. This “upside down” procedure must be used when measuring a component that will be stressed and forced from its natural shape by the weight of the optical flat. Large diameter carbon graphite components with small cross section profiles are notorious for being extremely physically unstable. This is a prime example of an application that requires a reflection stand for accurate flatness measurement.

The best pinhole is perfectly round (since irregularities cause higher-order diffraction effects) and in an extremely thin piece of material. Industrially produced pinholes benefit from laser etching, but a hobbyist can still produce pinholes of sufficiently high quality for photographic work.

ELB-Schliff Werkzeugmaschinen GmbH has been producing surface and profile grinding machines for over 70 years. The company was founded by Edmund Lang in the city of Babenhausen which led to the name "ELB-Schliff".

OpticalFlatfilter

Founded in 1934, KEHREN is a well-established designer and builder of high-precision grinding machine tools and systems under the following categories: vertical grinding centers, vertical grinding centers with portal design, surface grinders with rotary tables and horizontal spindles, and surface grinders with dual rotary tables and vertical spindles.

Modern manufacturing has enabled the production of high quality pinhole lenses[12] that can be applied to digital cameras.

Exposures projected on to modern light-sensitive photographic film can typically range from five seconds up to as much as several hours, with smaller pinholes requiring longer exposures to produce the same size image. Because a pinhole camera requires a lengthy exposure, its shutter may be manually operated, as with a flap made of opaque material to cover and uncover the pinhole.

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An optical flat is a contact optical measurement device used in conjunction with a monochromatic light source to measure precision flat surfaces. Lapmaster optical flats are manufactured from high quality fused quartz.Fused quartz is used because it possesses an extremely low coefficient of thermal expansion and extremely high resistance to abrasion. Even with the hardness of fused quartz the optical flat must be handled and used very carefully to prevent damage and scratches. It is important to not slide or rotate the optical flat on any surface. Optical lens tissue and alcohol should be used to clean optical flats. Since the measurement resolution of an optical flat is a light band (.0000116” or .295 micron), components must be flatter than 15 or 20 light bands in order for the optical flat to be able to make the interference fringes visible. This is not normally a problem since most flatness requirements are to achieve single digit light bands. Proper inspection procedure dictates that the optical flat must be large enough to completely cover a surface that has a flatness specification.

Founded in Germany in 1804 by Mr. Peter Wolters, Peter Wolters has been producing lapping, polishing and fine grinding equipment since 1936. In 2019 Precision Surfacing Solutions acquired the division Wafer plant and service business for photovoltaic and special materials of Meyer Burger. Further Information can be found at www.precision-surface.ch

On the left-side of the graph, the pinhole is large, and geometric optics applies; the resolution limit is about 1.5 times the radius of the pinhole. (Spurious resolution is also seen in the geometric-optics limit.) On the right-side, the pinhole is small, and Fraunhofer diffraction applies; the resolution limit is given by the far-field diffraction formula shown in the graph and now increases as the pinhole is made smaller. In this formula, the radius of the pinhole is used instead of its diameter, that's why the constant is 0.61 instead of the more usual 1.22. In the region of near-field diffraction (or Fresnel diffraction), the pinhole focuses the light slightly, and the resolution limit is minimized when the focal length f (the distance between the pinhole and the film plane) is given by f = s2/λ. At this focal length, the pinhole focuses the light slightly, and the resolution limit is about 2/3 of the radius of the pinhole. The pinhole, in this case, is equivalent to a Fresnel zone plate with a single zone. The value s2/λ is in a sense the natural focal length of the pinhole.[citation needed]

The relation f = s2/λ yields an optimum pinhole diameter d = 2√fλ, so the experimental value differs slightly from the estimate of Petzval, above.

The depth of field is basically infinite, but this does not mean that no optical blurring occurs. The infinite depth of field means that image blur depends not on object distance but on other factors, such as the distance from the aperture to the film plane, the aperture size, the wavelength(s) of the light source, and motion of the subject or canvas. Additionally, pinhole photography can not avoid the effects of haze.

A pinhole camera effect can sometimes occur naturally. Small "pinholes" formed by the gaps between overlapping tree leaves will create replica images of the sun on flat surfaces. During an eclipse, this produces small crescents in the case of a partial eclipse, or hollow rings in the case of an annular eclipse. Disco balls can also function as natural reflective pinhole cameras (also known as a pinhead mirror).[21]

The f-number of the camera may be calculated by dividing the distance from the pinhole to the imaging plane (the focal length) by the diameter of the pinhole. For example, a camera with a 0.5 mm diameter pinhole, and a 50 mm focal length would have an f-number of 50/0.5, or 100 (f/100 in conventional notation).

Giambattista Della Porta wrote in 1558 in his Magia Naturalis about using a concave mirror to project the image onto paper and to use this as a drawing aid.[6] However, at about the same time, the use of a lens instead of a pinhole was introduced. In the 17th century, the camera obscura with a lens became a popular drawing aid that was further developed into a mobile device, first in a little tent and later in a box. The photographic camera, as developed early in the 19th century, was basically an adaptation of the box-type camera obscura with a lens.

Within limits, a small pinhole through a thin surface will result in a sharper image resolution because the projected circle of confusion at the image plane is practically the same size as the pinhole. An extremely small hole, however, can produce significant diffraction effects and a less clear image due to the wave properties of light.[15] Additionally, vignetting occurs as the diameter of the hole approaches the thickness of the material in which it is punched, because the sides of the hole obstruct the light entering at anything other than 90 degrees.

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The spacing between the lines in each element is equal to the thickness of the line itself. When the target is imaged, the resolution of an imaging system can ...

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Opticalflat

Due to the large f-number of a pinhole camera, exposures will often encounter reciprocity failure.[20] Once exposure time has exceeded about 1 second for film or 30 seconds for paper, one must compensate for the breakdown in linear response of the film/paper to intensity of illumination by using longer exposures.

Founded in Chicago in 1948 as a manufacture of lapping and polishing machines for the mechanical seal market, Lapmaster has grown to a worldwide solution provider for more than 20 industries like precision optics and advanced materials.

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The correct optimum can be found with Fraunhofer approximation of the diffraction pattern behind a circular aperture at:

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Related cameras, image forming devices, or developments from it include Franke's widefield pinhole camera, the pinspeck camera, and the pinhead mirror.

A method of calculating the optimal pinhole diameter was first published by Joseph Petzval in 1857. The smallest possible diameter of the image point and therefore the highest possible image resolution and the sharpest image are given when:[16]

The image of a pinhole camera may be projected onto a translucent screen for a real-time viewing (used for safe observation of solar eclipses) or to trace the image on paper. But it is more often used without a translucent screen for pinhole photography with photographic film or photographic paper placed on the surface opposite to the pinhole aperture.

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The first known description of pinhole photography is found in the 1856 book The Stereoscope by Scottish inventor David Brewster, including the description of the idea as "a camera without lenses, and with only a pin-hole".