Ah microscopes. In days past getting enough illumination to see with them was a complex process involving a parabolic mirror, a light source such as a candle (for the old days) and lots of patience. In the 20th century microscopes with lights were developed, but such luxury! They were often expensive and prone to burning through expensive bulbs.
These days we are much luckier with our microscope choices. Almost every microscope in production has some kind of built-in illumination and the handful that don’t are used simply to demonstrate how microscopes without built-in lights work.
But there are sometimes many choices as to how to illuminate your microscope. We are going to cover a few of them and discuss their advantages and disadvantages. Let’s start at the bottom of the heap with:
Mirror Illuminated Microscopes:
A mirror illumination involves a small parabolic mirror that uses an outside light source (usually a light bulb on the ceiling or a desk lamp) to concentrate light up through the condenser lens and through the sample material. This is not easy as you must align the microscope with the light source and then angle the mirror just right to get the light to go through the condenser lens. This can get very frustrating, especially for young users.
- OLD SCHOOL!
- No batteries or power required.
- Very hard to use
- Requires outside light source
- Difficult to control light intensity
Prism Illuminated Microscopes
Something of an update of the mirror microscope is a prism illuminated microscope. Here instead of a parabolic mirror a prism is used. It still must be aimed at a light source, but no longer do you need to adjust the angle of anything as the prism uses internal reflection to send the light up through the sample. Had illuminated microscopes become so much more available prism microscope would have put a serious dent in mirror microscopes.
- Easier to use than mirror microscope
- No batteries or power required
- Still hard to use compared to an illuminated microscope
- Requires outside light source
- Provides less light due to lack of concentrating parabolic mirror.
Incandescent Illuminated Microscope:
Incandescent light is, or at least was the most prevalent kind of light bulb around, so it was only natural that some of the earliest illuminated microscopes would use them. Usually they were outside sources that could be placed right underneath the condenser lens, but soon there were microscopes with illuminators built in. Sometimes incandescent bulbs are labeled as Tungsten.
- Turns on immediately. No warm-up or adjusting a mirror
- Easy to design a dimming system into the microscope
- Lowest cost bulb design
- Shortest bulb life of any illuminated design
- Requires more power than most other bulb designs – very few incandescent microscopes will operate on batteries
- Heat produced by bulbs (can be a problem with live samples, etc)
Fluorescent Illuminated Microscopes:
With fluorescent bulbs becoming a common method of lighting offices, etc efficiently, many hoped to use them for microscope illumination. But it was not until compact fluorescent bulbs became common that microscopes would use them for illumination. This was fine for some microscope designs, but it failed for other designs as even the compact bulbs tended to take up a lot of space:
- Longer bulb life – Fluorescent bulbs have the 2nd longest lifespan of the light bulbs on this list
- Low power consumption
- Low heat production
- Large bulb size – very few microscope can accommodate the large bulbs
- Still need plug-in design as fluorescent bulbs need more power to start than most batteries can provide
- Cannot be dimmed or adjusted
- Bulbs can lose brightness over time
- Bulb may not turn on instantly.
Halogen Illuminated Microscopes
A variation on the incandescent bulbs, really. But with a halogen material in the bulb instead of a gas. Halogen bulbs can be brighter and last longer despite their smaller size.
- Instant-on, just like regular tungsten bulbs
- Brighter light at the same power consumption as incandescent bulbs
- Long life than incandescent bulbs
- Still a much shorter life than other bulb designs
- Heat production
- High power requirements
- Expensive bulbs
LED Illuminated MIcroscopes
- Very long bulb life – even long compared to Fluorescent Bulbs
- No heat produced by bulb
- Low power requirements – many LED microscopes can be powered with batteries
- Easily dimmable
- Instant on.
- Light color – many LEDs have a somewhat ‘cold’ light color compared to other bulbs.
- Hard to replace – LEDs may last longer than the microscope that uses them, but if the bulb does burn out it can be much harder to replace the bulbs than with other designs.
Not all lights are the same, mind you. Some LEDs are little pen-point things that are junky, especially compared to a 3 Watt LED bulb such as is found in the microscope shown above. But this list of advantages and disadvantages gives you some perspective on the various models.
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