Heliography, which means 'sun drawing', was developed by a French inventor Joseph Nicéphore Niépce (1765-1833). This was widely regarded as the origin of permanent photographs from nature in history. Firstly, workers need to prepare Bitumen of Judea, a kind of natural asphalt which could become less soluble when it had been left exposed to light dissolved in lavender oil that let hardened areas remained. Then coated it onto metal. After that, let the metal put out in direct sunlight. Finally, using solvent to rinse away the unhardened bitumen so that the picture will kept on the board everlastingly.

Daguerreotype - Earliest Widely Used

Heliography - Earilest Photographing

Heliography, which means 'sun drawing', was developed by a French inventor Joseph Nicéphore Niépce (1765-1833). This was widely regarded as the origin of permanent photographs from nature in history. Firstly, workers need to prepare Bitumen of Judea, a kind of natural asphalt which could become less soluble when it had been left exposed to light dissolved in lavender oil that let hardened areas remained. Then coated it onto metal. After that, let the metal put out in direct sunlight. Finally, using solvent to rinse away the unhardened bitumen so that the picture will kept on the board everlastingly.

Daguerreotype - Earilest Widely Used

Daguerreotype, the first imaging technology to come into widespread use, was named after his father Louis-Jacques-Mandé Daguerre (1787-1851), a painter who introduced the technology in 1839. To photograph a picture contains several procedures:

1. Manufacture a plate formed on a highly polished silver surface with copper substrate.
2. Eliminate all contamination and tarnish using a buff with rotten stone or velvet and then swab the surface with nitric acid.
3. Let the silver surface exposed to halogen fume, normally idoine fume.
4. Carry the plate to the camera in a light-tight plate holder, then expose to the picture in proper time and finally artist will get latent image.
5. Develop the latent image by heated mercury fume in a purpose-made developing box.
6. Fix the plate with a sodium thiosulfate so that the light sensitivity will be arrested.
   The photograph produced by this technology make the light sensing possible. However, it cost much time. To photograph a portrait, the plate needs to be exposed about half an hour, so many guests had to act as petrified for a long time.

The photograph produced by this technology make the light sensing possible. However, it cost much time. To photograph a portait the plate needs to be exposed about half an hour so many guests had to act as petrified for a long time.

Film - Faster and Easiler

Later, photographic film was invented and had been widely used for a long time before the birth of digital imaging. The film is a strip or a sheet with transparent plastic film base. One side of it contains gelatin emulsion with light-sensitive silver halide, normally silver bromide, crystals. Because film yields transparent negatives with light-dark or colors, artists need to develop the film to its opposites and finally receive the made-up articles they want. The size and amount of crystals determine the sensitivity, contrast and resolution of pictures. Films are also affected by physics of silver grain activity and random grain activity by photons. Latterly, color photograph was invented by photographic engineers. The principle of the works is to build at least three layers to make the crystals sensitive to different colors. Usually, blue-sensitive layer is on the top followed with the green and red layers and at present, practically a film contains 12 with more than 20 different kinds of chemical in each layers for chromatic imaging.

Charge-coupled device(CCD) Sensor - Digitization

Charge-coupled device (CCD) sensor was invented in 1969 at AT&T Labs by Willard S. Boyle and George E. Smith who were awarded the 2009 Nobel Prize for physics for their invention of this imaging semiconductor circuit. The pixels in this device are represented by p-doped MOS capacitors. The CCD sensor contains a photoactive region, which is an epitaxial layer of silicon, and a transmission region made of shift register. The operation mechanism is as follow. Firstly, capture imaging pictures in photoactive region. Then the photoactive region will accumulate an electric charge proportional to the light intensity at that location. After that, the transmission region will receive the signal and dump into a charge amplifier. Later, the charge signal will be converted into voltage and at last the information will be sampled, digitized and stored.

As for colorful CCD sensor, Bryce Bayer, working at Eastman Kodak, invented Bayer filter, a color filter array for arranging red-green-blue (RGB) color filters on a square grid of photo-sensors. A single square is composed of four pixels: one filtered red, one for blue and two for green, making colorful digital imaging possible.

To be brief, the creation of CCD sensor directly guided the design of digital camera so that users could store, edit and delete pictures as they wish, which opens a brand new world for photographing and design.

Biological Light Imaging System

Black-White Imaging