Apne LCD ya LED tv se phele bade box jese dikhne wale CRT tvs to use kiye hi honge. Starting mein ye tvs black white colors mein aate the, fir kuch time ke baad color tv bhi ana shuru ho gaye the.
CRT tv ki screen ek glass vacuum tube hoti hai. Aur screen ke inner surface pe chote chote phosphor dots hote hai, jo ek phosphorescent substance se bane hote hai, jo teen primary colors jese red, green, aur blue me light emit krte hai. Tube ke back side pe ek electrode laga hota hai. Jab iss electrode ko negative voltage di jaati hai, toh ye ek electron beam emit krta hai, jo seedha phosphor dots pe jaake strike hoti hai. Jisse phosphor dots glow krne lagte hai. CRT tv ke Tube mein ek deflection coil bhi lagi hoti hai, ye ek magnetic field create krke electron beam ko phosphor dots tak pohochane mein madad krti hai.
CRT tv screen per 525 scan lines hoti hai. Tube mein lagi ek electron gun phele odd lines draw krti hai, phir even lines, aur ye process 60 times per second pe hota hai. Uske baad hum teen glowing primary colors yani red, blue, aur green ko electron gun ke drawing process ke zariye ek continuous image ke roop me perceive karte hain. Jisse hume ek screen pe ek image show hoti hai.
History
Television ka invention 7th September 1927 ko hua, jab electronic television ko San Francisco mein pehli baar successfully demonstrate kiya gaya. Iska invention Philo Taylor Fransworth ne kiya tha, jo ek 21 saal ka inventor tha aur jab tak woh 14 saal ka nahi hua tab tak uske ghar mein electricity nahi thi.
Jab Fransworth high school mein tha, tab usne ek aise system ke bare mein sochna shuru kiya jo moving images ko capture kar sake aur unhe radio waves par code karke bhej sake, aur phir screen par wapas ek image mein transform kar sake.
1953-1955 ke beech television programming ne radio ke formats se kuch hatkar apni pehchaan banana shuru ki. 1980’s mein home video cassette recorders widely available ho gaye, jisne viewers ko programs ko record karne aur replay karne ki suvidha di.
1950s Mein Colour Television Ki Evolution
1950 mein, FCC (Federal Communications Commission) ne CBS ke color television aur unke broadcast standards ko commercial use ke liye approve kar diya. Lekin us waqt ke 12 million television sets mein se sirf kuch 24 sets hi CBS ke color signal ko receive kar sakte the, isliye kuch mahine baad hi CBS ne apne color broadcasts band kar diye.
Phir June 1951 mein, Sarnoff aur RCA ne apne naye color television system ko proudly unveil kiya. Is system ka design dichroic mirrors ka use karta tha, jo image ke blue, red, aur green components ko alag-alag karte the. Har component ko ek monochrome camera tube par focus kiya jaata tha. Har tube ek signal create karti thi jo image ke red, green, ya blue component ke corresponding hoti thi.
Receiver tube mein teen electron guns hote the, ek har primary color signal ke liye. Screen par chhote chhote triangles ka grid hota tha, har ek triangle ek specific primary color ke liye hota tha. Har 1/60 second mein poori picture scan ki jaati thi, teen color components mein separate ki jaati thi, aur transmit ki jaati thi; aur har 1/60 second mein receiver ke teen electron guns red, green, aur blue colors ko simultaneously paint karte the, left to right aur line by line.
RCA ka color system existing black-and-white sets ke saath compatible bhi tha. Yeh system color signals ko do signals mein convert karta tha: ek total brightness ya luminance signal (jisse “Y” signal kaha jaata tha) aur ek complex second signal jisme color information hoti thi. Y signal ek regular monochrome signal ke corresponding hota tha, isliye koi bhi black-and-white receiver is signal ko pick kar sakta tha aur color signal ko ignore kar sakta tha.
Also read: