History of the Light Microscope
The origins of the microscope - from glass lenses
From ancient times, man has wanted to see things far smaller than could be perceived with the naked eye. Although the first use of a lens is a bit of a mystery, it's now believed that use of lenses is more modern than previously thought. However, it has been known for over 2000 years that glass bends light. In the 2nd Century BC, Claudius Ptolemy described a stick appearing to bend in a pool of water, and accurately recorded the angles to within half a degree. He then very accurately calculated the refraction constant of water.
During the 1st century AD (year 100), glass had been invented and the Romans were looking through the glass and testing it. They experimented with different shapes of clear glass and one of their samples was thick in the middle and thin on the edges.
They discovered that if you held one of these "lenses" over an object, the object would look larger. These early lenses were called magnifiers or burning glasses. The word lens is actually derived from the Latin word lentil, as they were named because they resembled the shape of a lentil bean.
Salvino D'Armate - the first eyeglasses (spectacles)
Around the same time, Roman philosopher Seneca (c. 4 BC - AD 65) described actual magnification by a globe of water. "Letters, however small and indistinct, are seen enlarged and more clearly through a globe of glass filled with water."
The lenses were not used much until the end of the 13th century when spectacle makers were producing lenses to be worn as glasses. Salvino D'Armate (c. 1258-1312) from Italy is credited for making the first eye glass, providing the wearer with an element of magnification to one eye.
The first man to combine two lenses is believed to have been Roger Bacon (c. 1214 - 1294), the English Franciscan monk, who studied the optical properties of lenses and mirrors (a study which eventually contributed to charges of 'witchcraft' against him). Bacon's investigations of the properties of the magnifying glass partly rested on the handed down legacy of Arab opticians; in particular, Basra born Ibn al-Haytham (Alhazen) (965 - 1039), known as the First Scientist. Ibn al-Haytham's Book of Optics (Kitâb al-Manâzir) laid the foundations for modern physical optics, transforming the way in which light and vision were understood. Ibn al-Haytham was in turn influenced by Ibn Sahl's 10th century study of the refraction of light, especially by lenses. Ibn Sahl (c. 940 - 1000) was a mathematician, physicist and optics engineer and was credited with first discovering the law of refraction, usually called 'Snell's law'. He used the law of refraction to derive lens shapes that focus light with no geometric aberrations.
Optical microscope invention and the first microscopes
It is widely believed that Dutch spectacle makers, Zacharias Jansen and his father Hans were responsible for making the first compound microscope in the late 16th century (Z Janssen c. 1580 - 1638). The microscope consisted of three draw tubes with lenses inserted into the ends of the flanking tubes. The eyepiece lens was bi-convex and the objective lens was plano-convex, a very advanced compound design for this time period. Focussing of this handheld microscope was achieved by sliding the draw tube in or out while observing the sample. The microscope was capable of magnifying images approximately 3 times when fully closed and up to ten times when extended to the maximum.
There has been some dispute however, as to whether German born, Hans Lippershey, was another possible inventor, who is credited with the invention of the first telescope.
Zacharias Jansen also claimed that he himself had designed the telescope at that time.