Here’s something that isn’t much talked about, that I get a TON of questions about. Microscopes generally come with a few different types of microscope light source types, and most people don’t spend time in their day to day lives thinking about the different kind of light sources we have in the world. It’s no surprise that most people aren’t sure what the differences are between LED lighting, and halogen/tungsten lighting (which are the two most common kinds of microscope light sources for all intents and purposes of this blog) when it comes to microscope light. Sure, there are a few others like fluorescent lights and mercury bulbs, but those can be a bit more specialized, so we’re going to look in the broad scheme of things today.
Which kind of microscope light source is best? Which one do I need for application x, or application y? Why should I get one instead of the other? These are all questions we’re going to answer here to help quell the confusion. So, without further ado, here we go!
Microscope Light Sources: Halogen or LED?
Halogen (or tungsten) microscope light sources are by far the most common kinds of lighting systems available, although LED is making a quick rise as an alternative. They both emit light, of course, but what makes them different?
Halogen Microscope Light Sources
In terms of a microscope light source, halogen is great because (most of the time), the bulbs are easily replaced, and even more easily sourced when you need to buy more. Generally, you can even find other bulb wholesalers or specialty stores that can get you the bulb you need for your halogen microscope light.
These kinds of a microscope light give off light that is close in color temperature to sunlight, so they’re frequently called “daylight” bulbs. You’ll notice a halogen bulb gives off more of a yellow or off white color when they are ignited, which is a big sign that you are using a halogen microscope light source on your microscope. Being close to sunlight, halogen lights give off great color integrity, which basically means that the sample is going to show up as a true to color life image, like you would see if you were outside and your eyes were capable of seeing your sample without the aid of a microscope. Very good for microphotography, which demands accurate colors, as well as most research projects and applications. Here’s an example a wildly popular halogen microscope light source equipped microscope:
Halogen lights are considered a “hot” light source. This means quite simply that they emit heat when in use. This is both a benefit and a detriment to this kind of a microscope light source. It’s beneficial in a sense that certain applications do well with heat on the stage and sample, such as semen inspections where the sample needs to be kept live.But, the problem is you can’t control the amount of heat–it’s going to keep increasing up to a point. So if it gets too hot, you can still kill or dry off your sample. The downside is just that–other samples that don’t do well with heat will die off or dry up, so you have limited viewing time of the sample.
This is not to say samples lit by LED last forever either, but they do last a longer period of time with samples that can’t take heat.
LED Microscope Light Sources
LEDs are becoming more and more commonplace as microscope light sources for a number of reasons, but there are also drawbacks to using LEDs in a microscope light. The greatest advantage of LED microscope light sources, in my opinion, is that they last a very, very, very long time. Most LED bulbs are rated for the upwards of 40,000 light hours! Usually, this means your microscope is probably going to be outlasted by the bulb, as the likelihood to have an accident and break something are more likely than the bulb going out. Here’s an example of AmScope’s T340B-LED, an LED lit compound microscope:
Also, as mentioned above, LED microscope light sources are extremely low in heat emission. You can run an LED bulb for hours to days and it will still be cool to the touch, compared to about 15 minutes with a halogen causing mild to medium discomfort if touched. Even with its high light intensity, you won’t have a burning problem.
There are two major downsides with LEDs though, and for some people, they may be deal breakers. The first is that most LED lights on microscopes do not emit bright sunlight temperature light, or daylight–they’re more of a white with a slight blue tint to it. So this can sometimes discolor certain samples. So for microphotographers, this may be a point of concern.
The other major downside for LED microscope light sources is that often times, it’s not just a single LED bulb in a socket that can easily be replaced when it goes out. More often than not, microscope manufacturers have the LED(s) on a small circuit board array. So, as you might have guessed it by now, replacing a bulb can be a major pain in the rear end unless you are comfortable with solder and a soldering iron, as well as sourcing LED bulbs. Most people will have to send the microscope back for warranty service or repair if the LED goes out–and even then, only if it’s within the warranty period. Users outside of the warranty period will generally have to buy a whole new microscope, or pay for costly repairs with a specialist.
So what do I recommend for you? Well, it’s really up to your personal preference! I typically prefer halogen for units I own, but ideally, if I had an LED unit with an easily replaceable bulb, I would be set for life.
What microscope light source type do you think is best for your microscopy setup?
I bought my compound microscope less than a month ago. I chose halogen for two reasons: I read that some LED bulbs could produce UV. And this is really not good to look toward a bulb producing UV. So I asked Microscopenet if the LED used in their microscopes produced UV and the person answered that they did not know.
Second reason: Even when they say that the LED light can be replaced by ourselves, the LED bulb is not sold by the store selling the microscope using this LED bulb. And they are unable to tell us where those bulbs can be found. So… it is not really a bulb that we can change ourselves.
But the main problem with illumination is that it is not strong enough when we want to use darkfield. Most microscope have 20w bulbs (halogen or tungsten) or 3w LED. The ones using 30w halogen or the ones using 5w LED cost a lot more. So I have a 20w halogen. So what happens is when I put the darkdfield condenser up close to the slide, the background is black, but the sample does not receive enough light. So when using an oil darkfield condenser, the oil touches the slide only if it is placed right up close to the slide with the sample. So to get enough light, I need to lower the condenser, but then the oil does not touch the slide and the background is not black anymore, but I do see the bacteria (spirochetes) better because it receives more light. What people usually do is they add some light. They unplug the microscope, take off the halogen bulb, enter another stronger bulb in the hole left by the absent bulb, in a socket at the end of a wire, with the wire coming out under the microscope. This is what I will need to do because I want to use my oil darkfield condenser with oil and with the black background. Do you have other suggestions? And can you suggest some kind of bulb that will do the job?
Hello Sylvie! Unfortunately I don’t have any solutions for you on that issue. Most microscopes are rated for a specific heat level and wattage, so if you’re changing out the bulb, you’re most likely going to damage your unit. With that said, what microscope model do you have? For example, if you have a T490 from AmScope, you could technically use a 30w halogen bulb in the 20w unit. HOWEVER. I do not recommend doing this as you can damage the unit, as the heat output is something the unit is not prepared to handle (it does not have a fan like the 30w model does). This would be the only somewhat viable solution that I can think of. There’s no room to mount a stronger light under the condenser on most microscopes. Again, I don’t recommend it because you can damage your unit, but that would be the only thing I can think of that might help, besides spending the money on a more powerful unit.
ok. Thank you for your answer. I asked them (those who sold me the microscope) if I could put a 30w instead and they said no. So, I am not going to use the present system when I add light. One person chose to use a LED bulb, not in the socket of the microscope, but in another socket at the end of another wire that he sqeezed into the space where the bulb is (after taking it off). He gets very good results. And it does not produce heat. But I have not seen what bulb he is using, just the result on a video. I will let someone who can work securely with electricity do it for me but I need to choose the right bulb and I don’t really know what to choose since the microscope store does not sell LED bulbs. I will use a LED bulb that I will know does not produce UV… or if I don’t know, I have since had an idea: the camera stores sell little round pièces of glass that protect the camera against uv. They probably have one the right size to put on top of the light collector. I am not going to take away my illumination system that I have now, just add another one when I need. My microscope is OMAX M827-A1911BOIL at Microscopenet.
So far though, this is the only problem I get with my microscope and darkfield condenser. I like it a lot!
oops, there is a mistake in my comment. My microscope ends with A191BOIL not A1911BOIL