Elektrikli ev aletlerinde arayüz aydınlatması tasarımı
Illuminated user interface design in home appliances
Yazar: MEHMET ALTUĞ
Danışman: PROF. DR. CEVAT ERDEM İMRAK
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Makine Mühendisliği Ana Bilim Dalı
Derece: Yüksek Lisans, 2015
Konu: Makine Mühendisliği = Mechanical Engineering

Özet:
Gelişen teknoloji ile insanlar hayatlarının birçok alanında makinalarla etkileşim içine girmektedir. Gün geçtikçe makinalarla geçen zaman yüzdesi de artmaktadır. İlk olarak sanayi alanında kendini gösteren makinalaşma, günümüzde özel ve ortak her yaşam alanına girmiş bulunmaktadır.Makinalarda insanlarla makinalar arasındaki etkileşimi sağlamak amacıyla bulunan sistemler arayüz olarak adlandırılmaktadır. İlk örnekleri basit kol ve düğme gibi mekanik sistemler olan makina arayüzleri evrimleşerek elektromekanik ve elektronik kontrol sistemlerine dönmüşlerdir. Ana görevi kontrol amaçlı girdileri makinaya iletmek olan arayüz sistemleri ilerleyen teknoloji ile kullanıcıya makinanın durumu ve devam etmekte olan fonksiyon hakkında bilgi veren görsel ve işitsel çıktılar da sağlamaya başlamışlardır.
Görsel çıktılar ilk örneklerde basit ışıklandırmalar olarak ortaya çıksa da, günümüzde şekil ve yazı ışıklandırmasından ekranlara kadar örnekleri bulunmaktadır. Bu tezin konusu olan elektrikli ev aletlerinin evlerimize girişinden itibaren şekil ve yazı ışıklandırmaları yaygın olarak kullanılmaktadır. Başta işleve yönelik tasarımlar yeterliyken, günümüzde arayüz aydınlatmasında görsel kaygılar da tasarımı etkilemektedir. Gelişen ve değişen optik elemanlar, tasarımda çeşitliliği sağlasalar da karmaşıklığı da yanlarında getirmektedirler.
Bu tezin ilk bölümünde makine-insan arayüzünün ne olduğu ve görevleri hakkında daha detaylı bilgi verilerek arayüz aydınlatma tarihi patent ve uygulama örnekleri ile anlatılmıştır. Arayüz aydınlatma tarihi 1900'lerin başında akkor lambaların kullanıldığı aydınlatılmış kutularla başlayıp LED'lerin kullanıldığı art aydınlatma örneklerine kadar gelişim göstermiştir. Bu zaman zarfında akkor, floresan lambalar, elektroışıma kaynakları ve LED'lerin kullanıldığı art ve kenar aydınlatma prensibine dayanan birçok örnek ortaya çıkmıştır.
Bir sonraki bölümde basit optik bilgisi verilerek önemli dört optik terimlerden bahsedilmiş, kırılma ve yansıma basitçe anlatılarak, toplam iç yansıma prensibi ve yansıma çeşitleri üzerinde durulmuştur. Toplam iç yansıma kırılmada bahsedilen Snell yasasına göre ışık çok yoğun ortamdan az yoğun ortama geçerken kırılma açısını 90 derece yapan geliş açısından fazla bir geliş açısına sahip ışının ortam değiştiremeden geldiği ortama geri dönmesi olayıdır. Bu prensip bir sonraki bölümde anlatılacak ışık taşıyıcıların görevini yerine getirmesini sağlayan prensiptir.Üçüncü bölümde arayüz aydınlatması tasarımında kullanılabilecek optik tasarım elemanları hakkında bilgi verilmiştir. Akkor lamba, floresan lamba, elektroışıma kaynakları, LED ve OLED olmak üzere 5 adet ışık kaynağı çeşidi tanıtılmıştır. Işık taşıyıcılar hakkında temel tasarım bilgileri verilmiştir. Düz ve konik reflektörlerden bahsedilerek eliptik, parabolik, hiperbolik ve küresel konik reflektörler üzerinde durulmuştur. Son olarak katkılı, Gauss ve prizmatik difüzörlerden bahsedilmiştir.
Dördüncü bölümde örnek olması açısından Arçelik In Love Gurme Çay Makinası'nın arayüz aydınlatması tasarımı çalışmasından bahsedilmiştir. Bu çalışmada tasarım temel konstrüksiyon sistematiği adımları kullanılarak yapılmıştır. Öncelikle firmanın istekleri sıralanarak bir istekler listesi oluşturulmuştur. İstekler listesinde dördü kesin üçü arzu tipi olmak üzere yedi istek sıralanmıştır. İstekler listesinde üç adet temel fonksiyon belirlenmiştir. Bunlar ışığın iletilmesi, ışığın dağıtılması ve ışık kaçaklarının sınırlandırılmasıdır. Işığın iletilmesi temel fonksiyonu için ışık taşıyıcı ve hava fonksiyon taşıyıcıları seçilerek çözüm matrisine eklenmiştir. Işığın dağıtılması temel fonksiyonu için çözüm matrisine eklenen fonksiyon taşıyıcılar katkılı, Gauss ve prizmatik difüzörlerdir. Işık kaçaklarının sınırlandırması temel fonksiyonu için seçilen fonksiyon taşıyıcılar ise toplam iç yansıma prensibi ve reflektördür. Fonksiyon taşıyıcıların oluşturduğu çözüm matrisinden iki çözüm elde edilmiş ve bu çözümler OptisWorks optik analiz programı ile analiz edilmiştir. Son olarak hedef kriterlere göre oluşturulan hedef büyüklükler matrisi ile çözümler puanlanmış ve en yüksek puanlı çözüm seçilmiştir.
Son bölümde örnek tasarım hakkında elde edilen sonuçlar üzerinden genelleme yapılarak elektrikli ev aletlerinde aydınlatma tasarımı hakkında öneriler sıralanmıştır.

Abstract:
People are interacting with machines in different fields of daily life because of developing technology. Percentage of time spend with machines is increasing day by day. Nowadays mechanization, which was first seen in the field of industry, is in all private or common living spaces of people.A system used in machines, which makes human-machine interaction possible, is called a human-machine user-interface. The first examples of user-interfaces are basic mechanical systems with levers and buttons. While the technology is developing user interfaces are also evolved to electromechanical or electronic control systems. At the beginning, the main and only role of a user-interface is to transmit control inputs given by user to machine. By evolution, now a user-interface can give information about current situation of a machine and ongoing function with visual and audial signals.
The first examples of visual signals given by a user-interface are simple lamps. For now this signals are in the form of illuminated symbols, words and electronic display monitors. Illuminated symbols and words are common methods for home appliances interfaces from the very first time they entered to our life. Functional designs are adequate for this type of illuminations at first examples but while time is passing esthetically worries are become more and more important for design. While developing optical design elements are bringing a design variety in illuminated user interface design for designer they bring confusion too.
In first chapter human-machine user-interface concept and the functions of human-machine interface are explained in detail. A brief history of user-interface illumination is recited with the help of patent and application examples. The evolution is started with basic illuminated box concept with incandescent lamps and reached at LED tiles. Some of the steps of this evolution are fluorescent lamp edge lighting, eggcrate display, LED dot matrix display; electroluminescent display and LED back lighting.
In second chapter basic optic knowledge is given. Four important optical terms for optics are explained. These are luminous intensity, luminous flux, luminance and illuminance. Reflection and refraction rules are recited and Snell's law, Fresnel loss and total internal reflection principle are emphasized. According to Snell's law multiplication of sine of incidence angle and refraction index of the medium that ray is in before refraction is equal to multiplication of sine of refraction angle and refraction index of the medium that ray is in after refraction. While refraction, some of the light rays are reflected and some of them are absorbed and this percentage is called Fresnel loss. While a ray wants to pass from a denser medium to a low-density one it will be reflected when its angle of incidence is higher than a critical angle, which is identified according to Snell's law. This situation is called total internal reflection.
In third chapter all optical design element that are necessary for illuminated user-interface design are explained. There are five light sources. Incandescent lamps are first and the older light sources. They are known as hot light sources because they transforms only 10% of the electric energy to light and rest of it to heat. Fluorescent lamps give light when negative ions hit the fluor layer. Negative ions are created by mercury inside the lamps so fluorescent lamps are not nature friendly and they are big in size. Electroluminescent sources give light by passing electrical current from a phosphor layer. They are cold sources. They can be very thin and can be in the form of a flexible panel but their luminous intensity is love and their service life is short. LEDs are small light sources that uses semiconductors and electroluminescent principle. They are efficient light sources. OLEDs are some kind of electroluminescent sources that use organic materials instead of phosphor. They are in the form of flexible panels. Lightguides are specially designed transparent parts that transport light according to total internal reflection principle. They can be made off any transparent material like plastics (PC, PMMA, and PET) and glass. Entrance surface of the lightguide must have a proper design to accept more light rays from light sources. There is two main type of reflectors, which are called planar and conical reflector. Conical reflectors have four types. Hyperbolic reflectors reflect light coming from their one focus, as it come from other focus. Parabolic reflectors reflect light coming from their focus, as parallel rays. Elliptical reflectors reflects light coming from their one focus and direct to their other focus. Spherical reflectors has two characteristic. They reflect light coming from their geometrical center, back in the same direction and they reflect light coming from their focus, as parallel rays. There is three types of diffusers. Opal diffusers are made by adding micro opaque particles to a transparent material while manufacturing. Gaussian diffusers are made by increasing the surface roughness of a transparent part. Prismatic diffusers are engineered surfaces with micro prismatic structure and are made with extrusion process as films.
In forth chapter a case study about the illuminated user interface design of Arçelik In Love Gurme Teamaker is done according to systematic construction principle. Geometric boundaries, minimum average luminance, homogeneous luminance distribution, limited light leakage, least part, easy to manufactured and least fitting are determined as the needs of design and the list of needs are prepared. Light transportation, light diffusion and leakage limitation are derived from list of needs as the primary functions of the design. Atmosphere and a solid transparent part is chosen as the function carriers for light transportation primary function. Opal, Gaussian and prismatic diffusers are chosen as function carriers for light diffusion primary function. Total internal reflection and planar reflector are chosen as function carriers for leakage limitation primary function. A solution matrix is made with all these function carriers to find combinations for solutions. Two design solution are derived from solution matrix. One of these is group of conical light guide with concave spherical entrance surface to increase the amount of light entered and increased roughness in exit surface to form a Gaussian diffuser. This design is a combination of solid transparent part, Gaussian diffuser and total internal reflection function carriers. Second design is a nine-eyed reflector with an opal diffuser sheet on the exit surface of it. This design is a combination of atmosphere, opal diffuser and reflector function carriers. After this step, 3D CAD models are made and optical simulations are done for two designs with OptisWorks add-in for SolidWorks, which is an add-in of Optis Corporation. According to solutions, both of the designs are suitable according to minimum average luminance with 922,259 cd/m² for first design and 640,503 cd/m² for second design at the lowest illuminated area of the word "normal". Homogeneity is measured as a ratio of average luminance to highest luminance at the area and it is seen that first design has a more homogeneous distribution then the second one. As it is observed from simulation results, leakage limitation of first design is suitable and limitation of leakage is more than needed in second design. After that, design criteria are derived from list of needs and a weight is given to them for a scoring of design alternatives. Design criteria gave a weight between zero and one and total of all weights is equal to one. Then a score from zero to ten is given to designs for all criteria. After scores are multiplied with the weight of the criteria and added designs have a comparison score from zero to ten. A design criteria score matrix is made with all these information. First design has a 6,3 comparison score and second design has a 4,5 comparison score.
In last chapter, results are discussed. According comparison scores in the case study first design is selected for application. First design has enough minimum average luminance and better homogeneous luminance distribution and leakage limitation then second design according to needs. It has only one part while the second one has two. It will be produced with injection process from polycarbonate material. It can be fixed between electronic cardboard and interface glass with the help of ribs at the back of the interface glass. According to results of case study, some suggestions are made below:
 Lightguides, which is using total internal reflection principle, are an effective method to transport light from one point to another.
 Entrance surfaces of the lightguides must have a suitable design to increase the amount of light entered, according to type of light source.
 Transparent polymer materials like PC or PMMA should be used to increase the producibility of lightguide parts.
 To increase the effect of total internal reflection conical lightguide design is suggested.
 Light sources with wider viewing angle are suitable for wide area illumination.
 Diffuser should be used to increase homogeneity. Lightguide exit surfaces can be designed as diffusive surfaces to reduce part number.
 For designs, which are narrow and have parts that have low heat resistance, cold and small light sources like LEDs should be used.
 To increase the efficiency of light source and direct the light as needed, usage of reflectors is suggested.