Optical flat

OPTICAL FLAT
An optical flat is an optical-grade piece of glass lapped and polished to be extremely flat on one or both sides, usually within a few tens of nanometres (billionths of a meter).
They are used with a monochromatic light to determine the flatness (surface accuracy) of other surfaces, whether optical, metallic, ceramic, or otherwise, by interference.[1] When an optical flat is placed on another surface and illuminated, the light waves reflect off both the bottom surface of the flat and the surface it is resting on. This causes a phenomenon similar to thin-film interference. The reflected waves interfere, creating a pattern of interference fringes visible as light and dark bands.

The spacing between the fringes is smaller where the gap is changing more rapidly, indicating a departure from flatness in one of the two surfaces. This is comparable to the contour lines one would find on a map. A flat surface is indicated by a pattern of straight, parallel fringes with equal spacing, while other patterns indicate uneven surfaces. Two adjacent fringes indicate a difference in elevation of one-half wavelength of the light used, so by counting the fringes, differences in elevation of the surface can be measured to better than one micrometre.
Usually only one of the two surfaces of an optical flat is made flat to the specified tolerance, and this surface is indicated by an arrow on the edge of the glass.

Optical flats are sometimes given an optical coating and used as precision mirrors or optical windows for special purposes, such as in a Fabry–Pérot interferometer or laser cavity. Optical flats have uses in spectrophotometry as well.

1

Optik yassi optik darajadagi shisha bo'lagi bo'lib, bir yoki ikkala tomoni juda tekis bo'lib, odatda bir necha o'nlab nanometrlar (metrning milliarddan bir qismi) oralig'ida bo'ladi.

Ular monoxromatik yorug'lik bilan boshqa sirtlarning tekisligini (sirt aniqligini) optik, metall, keramik yoki boshqa yo'l bilan interferentsiya bilan aniqlash uchun ishlatiladi.[1] Optik yassi boshqa yuzaga qo'yilganda va yoritilganda, yorug'lik to'lqinlari tekislikning pastki yuzasida ham, u joylashgan sirtda ham aks etadi. Bu yupqa plyonka shovqiniga o'xshash hodisani keltirib chiqaradi. Aks ettirilgan to'lqinlar aralashib, yorug'lik va qorong'i chiziqlar sifatida ko'rinadigan interferentsiya chekkalari naqshini yaratadi.

Bo'shliq tez o'zgarib turadigan joylarda qirralarning orasidagi masofa kichikroq bo'lib, bu ikki sirtdan birida tekislikdan voz kechishni ko'rsatadi. Buni xaritada topish mumkin bo'lgan kontur chiziqlari bilan solishtirish mumkin. Yassi sirt teng oraliqda joylashgan tekis, parallel chekkalar namunasi bilan ko'rsatilgan, boshqa naqshlar esa notekis yuzalarni bildiradi. Ikki qo'shni chekka ishlatiladigan yorug'likning bir yarim to'lqin uzunligi balandligidagi farqni ko'rsatadi, shuning uchun chekkalarni hisoblash orqali sirt balandligidagi farqlarni bir mikrometrdan yaxshiroq o'lchash mumkin.

Odatda optik kvartiraning ikkita yuzasidan faqat bittasi belgilangan tolerantlik darajasida tekislanadi va bu sirt shisha chetidagi o'q bilan ko'rsatiladi.

Optik kvartiralar ba'zan optik qoplamaga ega bo'lib, maxsus maqsadlarda, masalan, Fabry-Pérot interferometrida yoki lazer bo'shlig'ida nozik nometall yoki optik oyna sifatida ishlatiladi. Optik kvartiralar spektrofotometriyada ham qo'llaniladi.

2

An optical flat is a precisely polished flat surface, used as a reference against which the flatness of an unknown surface may be compared. Edmund Optics offers both single surface and dual surface optical flats in either ZERODUR® or Fused Silica. The flatness of an optical flat is measured in fractions of a reference wavelength, 632.8nm. A λ/20 flat will have a maximum peak to valley deviation of 632.8/20 or 31.64nm. We offer several levels of flatness for our single surface flats: λ/4, λ/10, and λ/20. For our dual surface flats, ¼, 1/10 and 1/20 flatness are available.

WHAT AN OPTICAL FLAT SHOWS
When an optical flat's polished surface is placed in contact with a surface to be tested, dark and light bands will be formed when viewed with monochromatic light. These bands are known as interference fringes and their shape gives a visual representation of the flatness of the surface being tested. The surface flatness is indicated by the amount of curve and spacing between the interference fringes. Straight, parallel, and evenly spaced interference fringes indicate that the work surface flatness is equal to or higher than that of the reference surface.
APPLICATIONSMeasurement of the surface flatness of polished surfaces can be determined visually by comparing the variations between a work surface and the surface of an optical flat. Optical flats are versatile optical components used in many applications, such as: inspection of gauge blocks for wear and accuracy, as well as the testing of various components including windows, prisms, filters, mirrors, etc. They can also be used as extremely flat optical windows for demanding interferometry requirements.

Optik tekislik – bu aniq sayqallangan tekis sirt bo'lib, noma'lum sirtning tekisligini solishtirish mumkin bo'lgan mos yozuvlar sifatida ishlatiladi. Edmund Optics ZERODUR® yoki Fused Silica da bitta sirtli va ikki yuzali optik yassilarni taklif etadi. Optik tekislikning tekisligi mos yozuvlar to'lqin uzunligining 632,8 nm fraktsiyalarida o'lchanadi. L / 20 kvartirasi vodiydan 632,8 / 20 yoki 31,64 nm maksimal og'ish cho'qqisiga ega bo'ladi. Yagona yuza tekisliklarimiz uchun bir necha tekislik darajasini taklif qilamiz: l/4, l/10 va l/20. Ikki yuzli tekisliklarimiz uchun ¼, 1/10 va 1/20 tekislik mavjud.

OPTIK KAT NIMA KO'RSATILADI
Optik tekisning silliqlangan yuzasi tekshiriladigan sirt bilan aloqa qilganda, monoxromatik yorug'lik bilan ko'rilganda qorong'u va yorug'lik chiziqlari hosil bo'ladi. Ushbu bantlar interferentsiya chekkalari sifatida tanilgan va ularning shakli sinovdan o'tkazilayotgan sirt tekisligining vizual tasvirini beradi. Sirt tekisligi egri chiziq miqdori va interferentsiya chekkalari orasidagi masofa bilan ko'rsatiladi. To'g'ridan-to'g'ri, parallel va bir xil masofada joylashgan interferentsiya chekkalari ishchi sirt tekisligi mos yozuvlar yuzasiga teng yoki undan yuqori ekanligini ko'rsatadi.

QO'LLANILIShI Cilalangan yuzalarning sirt tekisligini o'lchash ish yuzasi va optik tekislik yuzasi o'rtasidagi o'zgarishlarni solishtirish orqali vizual tarzda aniqlanishi mumkin. Optik yassilar ko'plab ilovalarda qo'llaniladigan ko'p qirrali optik komponentlardir, masalan: o'lchov bloklarini aşınma va aniqlik bo'yicha tekshirish, shuningdek, derazalar, prizmalar, filtrlar, oynalar va boshqalarni sinash. Ulardan juda tekis sifatida ham foydalanish mumkin. Interferometriya talablari uchun optik oynalar.

4

An optical flat utilizes the property of interference to exhibit the flatness on a desired surface. When an optical flat, also known as a test plate, and a work surface are placed in contact, an air wedge is formed. Areas between the flat and the work surface that are not in contact form this air wedge. The change in thickness of the air wedge will dictate the shape and orientation of the interference bands. The amount of curvature that is shown by the interference bands can be used to determine the flatness of the surface. If the air wedge is too large, then many closely spaced lines can appear, making it difficult to analyze the pattern formed. Simply applying pressure to the top of the optical flat alleviates the problem.

The determination of the flatness of any particular region of a surface is done by making two parallel imaginary lines; one between the ends of any one fringe, and the other at the top of that same fringe. The number of fringes located between the lines can be used to determine the flatness. Monochromatic light is used to create sharp contrast for viewing and in order to specify the flatness as a function of a single wavelength.