UV and IR Brightfield Setup

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CD394
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Joined: Sun Aug 02, 2020 2:52 pm

UV and IR Brightfield Setup

#1 Post by CD394 » Sun Aug 02, 2020 3:21 pm

Hello,
Newbie here. I have 5mm IR and UV LEDs (940nm,850nm,375nm,400nm) to setup with dichroic lenses and band pass filters. Is there a DIY multi LED fixture that I could possibly 3D print or craft to hold 4-5 LEDS so I can select. I was thinking of a 5mm fiber optic option if it exists, so I can use at oblique angles and under slides (for both transmitted and reflected setup).

Thank you for any feedback
Christian

MicroBob
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Re: UV and IR Brightfield Setup

#2 Post by MicroBob » Sun Aug 02, 2020 6:23 pm

Hi Christian,
there was a solution shown on photomacrography.net.
Whatever you do you need a good heat sink and a way to lead the heat away as the LEDs will probably runn fill power all the time in this setup.

Bob

Hobbyst46
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Re: UV and IR Brightfield Setup

#3 Post by Hobbyst46 » Sun Aug 02, 2020 6:25 pm

If the purpose is a fixture (in a row, or on the perimeter of a circle) of LEDs with a SINGLE fiber optic to shine above or below the slide, on a compound microscope, I have no direct solution but ideas, as follows:
1. 5mm LEDs are relatively to connect mechanically and electrically. All can be fed from a single power source, with an appropriate resistor (say 250 Ohm, but it really depends on the voltage source) and a multiport rotatory switch.
2. A 5mm fiber is too thick (IMO). The die of the 5mm LED is smaller than 5mm. A 1-2 mm fiber will transmit enough light. A thick fiber will not fit between the front end of the objective and the slide, anyway (unless it is the 4X or 10X, non-apochromat objective). Yet, you probably want a flexible, not rigid fiber.
3. So, I would try a 1-2mm fiber. 1mm I have used, 2mm - never. It can be a "bare" fiber, without the thick protective coating, so the outer diameter can be not much more than the optical diameter. And, what I suggest is that each of the LEDs has its own rigidly-connected (glued, see below) fiber.
4. If the LED has a "lens" dome, much light will be lost by inefficient coupling to the fiber. I would remove as much as possible of the dome, with a needle fine or grinder, very carefully, to preserve the die. The front end of the LED becomes a flat surface. Hone it with the finest emery paper or a honing powder so it becomes smooth and shiny. Then, cut the fiber - a square cut, so the end is perpendicular to the long axis, and epoxy the flat end of the fiber to the flat front of the LED, clamping them with a device that holds them co-axially. It is all much simpler to do than how it sounds. This way, a higher percentage of the light passes into the fiber.
5. Admittedly, the whole light fixture will resemble a large insect or spider (depending on the number of LEDs).

6. Such light sources tend to be very very bright, so take all safety precautions for your eye-sight; especially, UV light is dangerous.

P.S. there are plastic fiber optics and quartz fiber optics. Plastic are more flexible and easier to work on, yet quartz transmit better and for UV are (IMO) a must.

Heat effects from 5mm LEDs are usually very small, the power being <0.3W each.
Last edited by Hobbyst46 on Sun Aug 02, 2020 6:30 pm, edited 2 times in total.

MicroBob
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Location: Northern Germany

Re: UV and IR Brightfield Setup

#4 Post by MicroBob » Sun Aug 02, 2020 6:41 pm

Hi Doron,
you are right, if these are classic low power LEDs they won't produce much heat and won't connect well to a heat sink!

Hi Christian,
I expected you were using high power LEDs mounted e.g. on a star board. With classic small LEDs you should try whether the light output satisfies your needs before you spend time on the mechanical construction. For Epi fluorescence I use an 18W LED running at full power. For transmitted fluorescence a couple of Watt should do to get a visible image at low to medium magnifications.

Bob

Hobbyst46
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Joined: Mon Aug 21, 2017 9:02 pm

Re: UV and IR Brightfield Setup

#5 Post by Hobbyst46 » Sun Aug 02, 2020 9:38 pm

MicroBob wrote:
Sun Aug 02, 2020 6:41 pm
Hi Doron,
you are right, if these are classic low power LEDs they won't produce much heat and won't connect well to a heat sink!

Hi Christian,
I expected you were using high power LEDs mounted e.g. on a star board. With classic small LEDs you should try whether the light output satisfies your needs before you spend time on the mechanical construction. For Epi fluorescence I use an 18W LED running at full power. For transmitted fluorescence a couple of Watt should do to get a visible image at low to medium magnifications.

Bob
Yes, for epi-fluorescence 18W is not an exagarration. But if the OP will shine on the specimen from a distance of a few millimeters, AND-IF they are highly fluorescent, some emission could possibly be observed. In a darkened room.

CD394
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Joined: Sun Aug 02, 2020 2:52 pm

Re: UV and IR Brightfield Setup

#6 Post by CD394 » Sat Aug 08, 2020 12:02 am

Thank You MicroBob and Hobbyst46 for the thoughtful responses I'll be checking up your setups

Hobbyst46
- Is there a link or search term for this setup on macrophotography?

MicroBob
- I was thinking for reflective macroscopy as in this example http://www.microscopy-uk.org.uk/mag/ind ... dwir2.html

Thank You for any additional links.

Hobbyst46
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Joined: Mon Aug 21, 2017 9:02 pm

Re: UV and IR Brightfield Setup

#7 Post by Hobbyst46 » Sat Aug 08, 2020 6:49 am

CD394 wrote:
Sat Aug 08, 2020 12:02 am
Hobbyst46
- Is there a link or search term for this setup on macrophotography?
Sorry, not within my knowledge. I adopted the coupling idea from an unrelated field.

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