Cairn Dual OptoLED User manual

OPTOLED
Two channel LED illuminator
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Manual
The OptoLED power supply controls up to two OptoLED heads providing bright, stable illumination across
the visible, UV and IR range via a closed-loop photodiode feedback design. With sub-millisecond, vibration
free switching and intensity modulation, it’s suitable for fast, demanding imaging requirements as well as
routine fluorescence or transmitted light microscopy.
This manual provides guidance on setting up a new OptoLED system, operation via external control, and
installation and alignment on your microscope. The FuraLED and TwinLED dual LED couplings are also
included in this guide.
For the purpose of this manual, all words in bold blue refer to parts labelled in diagrams throughout this
document.
1. Important Safety Information: p.1
2. Setting up your hardware: p.2
2.1 Hardware connections: OptoLED power supply rear panel: p.2
2.2 Hardware connections: OptoLED power supply front panel: p.3
3. General Operation: p.4
3.1 Remote slider control (if applicable) : p.4
3.2 Optical Feedback: p.5
3.3 External triggering : p.7
3.3.1 TTL triggering: p.7
3.3.2 Analogue triggering: p.8
4. LED alignment on your microscope: p.8
4.1 Single port coupling: p.9
4.2 Dual port coupling: p.10
4.2.1 Installing filters and dichroic mirrors into Cairn filter cubes: p.10
4.3 Triple port / Quad port coupling: p.13
4.4 FuraLED / TwinLED coupling: p.13
1. Important Safety Information
The OptoLED can produce very intense illumination.
The LED heads should NEVER be viewed directly. When testing the LEDs, always shine them at a white
surface, such as a piece of paper and view the resultant reflection or fluorescence.
This is especially important with ULTRAVIOLET LEDs which will not appear bright to the human eye, but
can cause permanent damage if not used with care.

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2. Setting up your hardware
The OptoLED power supply is typically supplied with two operating channels, interchangeable LED
heads, an optional remote slider, coupling hardware for combining the LEDs and a suitable microscope
mount.
The power supplies have two identical control sections on the rear and front panels. Typically, the short-
est wavelength is connected to the left channel when viewing the front of the power supply, although all
LEDs will function on any channel of the OptoLED controller.
When supplied with a remote slider, however, ensure the LEDs are connected according to the coloured
LED stickers on the rear panel. This is due to the maximum current setting on the slider being set for
this corresponding LED.
2.1 Hardware connections: OptoLED power supply rear panel
1. Connect the power supply to the mains
2. Connect the LED to the LED head connector, ensuring the connector is screwed in place
for a secure connection.
3. If applicable, connect the remote slider to the REMOTE connector.
4. Turn the FEEDBACK switch ‘ON’. See section 3.2 (Optical Feedback) for further details of
this operating mode.
5. Ensure the switch next to EXT/LEVEL is ‘OFF’ by default. For further details of this
operating mode, refer to section 3.3.2 (Analogue triggering).
6. The MONITOR connector is not required for general operation.
Figure 1 : OptoLED power supply rear panel

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2.2 Hardware connections: OptoLED power supply front panel
1. Switch the red power button ON
2. Ensure the REMOTE / FRONT PANEL switch is set to FRONT PANEL unless you are using
a remote slider, in which case select REMOTE. If REMOTE is selected and this is not
connected on the rear panel, the LEDs will not come on under any operating conditions.
3. Turn the INTENSITY dial down to zero. This potentiometer has a 10-turn range,
which sets the LED drive current, providing the EXT/LEVEL switch is OFF on the rear of
the power supply (otherwise current is via an external voltage).
4. To test the unit, switch the OFF / AUTO / ON switch to ‘ON’ – the green LED ON indicator
should now be illuminated.
ENSURE YOU ARE NOT LOOKING DIRECTLY AT THE LED – ALWAYS VIEW THE
FLUORESECENCE ON A WHITE PIECE OF PAPER, as described in section 1.
5. Turn the INTENSITY dial to clockwise until you see light emitted from the corresponding
LED head. The current being applied to the LED head will be given on the adjacent
CURRENT display.
ENSURE YOU ARE NOT LOOKING DIRECTLY AT THE LED – ALWAYS VIEW THE
FLUORESECENCE ON A WHITE PIECE OF PAPER, as described in section 1.
6. All LEDs have different maximal drive currents, and once this limit is reached on the dial,
a protection feature triggers and the LED will transiently switch off and flash,
accompanied by the red OVERLOAD coming on.
If this occurs, turn the INTENSITY dial anticlockwise until the LED ON (green) indicator
stays green and the OVERLOAD (red) is no longer illuminated.
As general guidance on maximal current values – our highest rated LED heads are
currently white (both ‘cool’ and ‘warm’) at 3A and will overload at settings higher than
this value. By contrast, the 340nm UV LED will overload at >0.7A, so please take note of
the value on the current display accordingly, rather than using the 10-turn potentiometer
as an indicator of full range.
Feel free to contact us with specific questions regarding the maximal current for each
LED supplied with your OptoLED [e-mail]
Figure 2 : OptoLED power supply front panel

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3. General Operation
The OptoLED LED heads can be operated from either the controller front panel, the remote slider or
externally via TTL and/or an analogue voltage. The front panel control is described in section 2.2 and is
often used for continual illumination, such as checking cell transfections.
The remote slider offers a convenient microscope-side intensity control which overrides the front panel
controls.
The most common form of operation is via software control; although currently no dedicated OptoLED
USB operation is available, triggering on/off via 5V TTL provides fast LED switching and when used in
Feedback mode, an ultra-stable output shows the OptoLED’s true potential for quantitative imaging.
3.1 Remote slider control (if applicable)
Figure 3: OptoLED (optional) remote slider
1 Ensure the REMOTE / FRONT PANEL switch is set to REMOTE on the OptoLED power supply
front panel.
2 To test the unit, switch the OFF / AUTO / ON switch to ‘ON’ on the remote slider– the green
LED ON indicator should now be illuminated.
3 Slide the CURRENT slider up to increase intensity. The ‘MAX’ value is set prior to unit
shipping, and the LED will not overload providing the corresponding LED colour is connected
on this channel.
4 When using a remote slider with a variety of LEDs, the maximum current value can be
adjusted easily with guidance, so please contact us. If this preset is not adjusted, the overload
protection for the LED may be triggered below maximum on the slider, however, no damage
will be caused.

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3.2 Optical Feedback
When the FEEDBACK switch is set to ‘ON’ on the OptoLED rear panel, a feedback loop uses the output of
a photodiode amplifier built into the head to set the control voltage, rather than just the intensity dial or
slider. LED chip manufacturers and specifications vary, and when you factor in the influence of
temperature, LEDs tend to be less efficient as they get hotter.
A comparison of LED output both with and without feedback can be seen in figures 4 and 5.
Figure 4: 590nm LED optical output without Feedback enabled
The yellow trace shows a pulsed current going through the LED.
The timescale is 5ms/division, with the blue trace showing the optical output directly from the LED head,
obtained via the MONITOR BNC on the OptoLED rear panel.
The optical output declines during the ‘on’ period, due to temperature effects of the LED. (The 590nm
LED is a particularly pronounced example), again illustrating the differences between LED
manufacturers.

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Figure 5: 590nm LED optical output with Feedback enabled
Again, the timescale is 5ms/division, with the blue trace showing the optical output directly from the
590nm LED head.
With feedback enabled, the traces are now square. The thermal effect has a time course on the order of
milliseconds, whereas the optical feedback can be applied on a microsecond timescale, which is suffi-
ciently faster to deal with it completely.
When is Feedback not useful?
We would recommend switching Feedback on during general OptoLED operation, particularly consid-
ering the spectral output of an LED can also change with temperature. If you are pulsing an LED with
a very short duty cycle however, having Feedback enabled will limit the switching speed to ~10µs (vs.
<100ns with Feedback off), which incidentally is still fast enough for most applications.

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3.3 External Triggering
The OptoLED heads can be switched on or off, as well as the intensity being set by an external analogue
voltage via BNC connections on the rear panel. We also supply a data interface as an optional extra with
the system, plus the corresponding device drivers for a range of third-party acquisition software.
This combination is typically a Cairn boxed National Instruments USB device (details and connections of
the exact model will be provided with the unit), for which we have written our own Micro-Manager
drivers. Many other software packages also contain the National Instruments hardware drivers by de-
fault. Please contact us or refer to supplementary documentation for guidance installing and setting up
these devices.
3.3.1 TTL triggering
1. Connect GATE 1 on the rear panel of the OptoLED controller to a DIG I/O
channel of your data interface device via a BNC cable for each channel
respectively.
2. Switch the OFF / AUTO / ON switch to ‘AUTO’ on the front panel for each
channel.
3. If using a remote slider, ensure the REMOTE / FRONT PANEL switch is set to
REMOTE on the OptoLED power supply front panel and switch the
OFF / AUTO / ON switch on the remote to ‘AUTO’.
4. Ensure the INTENSITY dial (or slider on the remote) has been turned up
sufficiently to ensure light is emitted from the LED head.
5. When a TTL logic high (+5V) signal is given, the LED head should start emitting
light and the green LED ON indicator should now be illuminated.
6. Note: when solely using a TTL input, ensure the EXT/LEVEL switch is ‘OFF’ to
ensure the intensity is determined by the front dial.
Each OptoLED channel also has a second GATE input on the rear panel. When
connected to your imaging camera, this allows the LEDs to also be turned on
only when the camera is exposing and the relevant channel is selected in your
software, as the logic level will be low when the camera is reading out the
signal. This is a huge benefit for fluorescence microscopy, as damaging
phototoxicity is reduced, in addition to any motion artefacts.
7. To utilise this mode, connect GATE 1 to your data interface as described above,
plus connect GATE 2 to the ‘Expose Out’ BNC on your camera trigger cable.
8. Ensure OFF / AUTO / ON remains on ‘AUTO’
9. When using two channels, it’s advisable to connect both GATE 2 outputs to the
camera via a BNC T-piece, straight from the EXPOSE OUT output.
10. Now, when your camera goes live, or you are acquiring a stack of images, the
LED will appear to flash, signifying the low ‘down time’ during camera readout
at the end of the exposure.

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3.3.2 Analogue triggering
For intensity control in your software, the current provided to the OptoLED heads can be determined by
an analogue voltage. Often, this is used in combination with the TTL on/off triggering, therefore the
description below assumes the GATE inputs have already been determined.
1. Connect EXT/LEVEL on the rear panel of the OptoLED controller to an ANALOGUE OUT
channel of your data interface device via a BNC cable for each channel respectively.
2. Switch the adjacent EXT/LEVEL switch to ‘ON’.
3. Switch the OFF / AUTO / ON switch to ‘AUTO’ on the front panel for each channel.
(Or on the remote slider if available). *
4. Provide a TTL logic high in order to turn the LED on, plus an analogue voltage to
determine the intensity of light emitted. This voltage will vary depending upon the
maximal drive current of the head attached and will always match the current control on
the front panel. Therefore, there may be some trial and error with analogue voltages
applied when setting up this operating mode - too high and the overload protection will be
enabled, so reduce the voltage accordingly.
* If the only external operating mode is for analogue intensity (i.e. no additional TTL
inputs), switch the OFF / AUTO / ON switch to ‘ON’ to enable this mode.
Feel free to contact us with specific questions regarding the maximal current for each LED supplied with your
OptoLED [e-mail]
4. LED alignment on your microscope
Typically, the OptoLED is supplied with a microscope adapter and the means to mount either one, two,
three or four LEDs simultaneously. We also offer dedicated twin heads (namely the FuraLED and
TwinLED heads), which are all covered in this manual.
As we have adapters for a large range of microscopes, both past and present, they are not covered in
this document. Attaching them to your frame should be self-explanatory. If you are having issues,
however, please feel free to contact us!

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4.1 Single port coupling
1. Insert the OptoLED Head into the single port coupling, taking note of the notch section on
the outer casing.
2. Secure the LED Focus Adjustment screw within this notch on the LED head – this acts as
a safety measure, ensuring the LED cannot be easily removed during operation.
3. Move to a blank objective position on the microscope nosepiece and remove any cover
caps.
4. Ensure the relevant fluorescent filter cube is in position in the epi-fluorescent cube
turret.
5. Cover the objective aperture with small piece of white paper, or a centring tool provided
by your microscope manufacturer.
6. Loosen the LED Focus Adjustment screw and move the LED head in Z within the coupling
until the image of the LED comes into sharp focus on the piece of paper (Figure 7B).
7. Lock off this position by securing the thumb screw.
8. Centre the focussed image of the LED using the LED XY Adjustment screws (Figure 7C).
Figure 6: Single port coupling
A B C
Figure 7: Focussing and aligning the LED image at the back aperture of the objective
OptoLED Head
LED Focus Adjustment
LED XY Adjustment

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4.2 Dual port coupling
When mounting two LEDs, our dual port coupling includes a Cairn filter cube, which houses a dichroic
mirror (with suitable long pass characteristics) to reflect the LED of a shorter wavelength. Each LED has
individual X, Y and Z adjustments to ensure optimal illumination.
Figure 8: Cairn filter cube and filter removal tool
4.2.1 Installing filters and dichroic mirrors into Cairn filter cubes
Typically, the all Cairn multi-port couplings come supplied with appropriate excitation filters and dichroic
mirrors as per your specification. However, the Cairn filter cubes can be supplied empty and be easily
fitted in the lab, as per the instructions below.
Please contact us if you need any filter or mirror advice – we hold stock of all common Chroma filter
sets, often available for next day UK delivery.
Remove the 4 screws and
seperate the two halves.
Place the dichroic holder in
the recess
Remove the dichroic holder
Replace all the screws
1
4
2
3
5
6

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` ^
f
o
k
` ^
f
o
k
` ^
f
o
k
Turn the locking
ring anticlockwise
to remove it.
Carefully place
the recess.
Replace the locking
ring and rotate it
clockwise to secure.
Figure 9: Installing dichroic mirrors and filters in Cairn filter cubes
Please refer to specific guidance from your filter manufacturer for details on correct dichroic mirror
and filter orientation.

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Figure 10: Dual port coupling
1. Mount the LEDs in wavelength order, with the shortest wavelength closest to the rear of the
microscope frame.
2. Move to a blank objective position on the microscope nosepiece and remove any cover caps.
3. Ensure the relevant fluorescent filter cube is in position in the epi-fluorescent cube
turret.
4. Cover the objective aperture with small piece of white paper, or a centring tool provided by your
microscope manufacturer.
5. Follow the steps described in section 4.1 for alignment and focus adjustment of the
Long wavelength LED (2).
6. Remove the cube cover magnetic door to gain access to the Cairn filter cube, ensuring this contains
a suitable dichroic mirror and is in place within the dual port coupling.
7. Adjust the focus of the Short wavelength LED (1) by moving the LED head in Z within the coupling
and observing the image at the back aperture of the objective, as previously described
5. Lock off the LED Focus adjustment thumb screw.
6. Using the 1.5mm Hex key provided, adjust the position of the Short wavelength LED (1) via the
Reflected LED XY adjustment (note the magnetic door can remain in place). This mechanism tips
and tilts the Cairn cube housing the dichroic mirror, acting as a precise alignment tool for the
reflected pathway.
Short Wavelength LED (1)
Short Wavelength LED (2)
LED Focus Adjustment
LED XY Adjustment
Reflected LED XY adjustment
LED Focus Adjustment
Microscope Frame

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4.3 Triple port / Quad port coupling
When installing a triple port or quad port LED coupling to house three or four LEDs respectively, the
coupling will be an extension of the dual port configuration.
Always ensure the LEDs are in wavelength order, with the shortest closest to the microscope frame and
that suitable dichroic mirrors are present in the Cairn filter cubes with the shortest wavelength in the
fully reflected position and the longest in the fully transmitted position. Please also ensure that suitable
dichroic mirrors are fitted to the Cairn filter cubes.
The longest wavelength LED will have individual X, Y and Z controls and all reflected LEDs of shorter
wavelengths will have an individual Z control, with XY adjustment on the appropriate cube cover door as
described previously.
For quad port couplings, one dichroic mirror will reflect two LEDs, therefore both will move in XY
simultaneously. All LEDs have individual controls, however, so can be aligned and focussed.
appropriately.
We recommend aligning the LEDs in wavelength order, from shortest to longest.
4.4 FuraLED / TwinLED coupling
340nm
385nm
340nm LED
X&Y
adjustments
385nm LED
X&Y
adjustments
340nm LED
focus
385nm LED
focus
Figure 11: FuraLED dual LED coupling

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The FuraLED dual port coupling houses two UV LEDs (typically 340nm and 385nm for Fura-2, although
a Fura-8 variant is available), photodiodes providing optical feedback for each channel, excitation filters
and a dichroic mirror to combine the two wavelengths.
Similarly, the ‘TwinLED’ houses two non-UV LEDs for more general illumination, with the same
adjustments available for setup.
1. Move to a blank objective position on the microscope nosepiece and remove any
cover caps.
2. Ensure the relevant fluorescent filter cube is in position in the epi-fluorescent cube
turret.
3. Cover the objective aperture with small piece of white paper, or a centring tool
provided by your microscope manufacturer.
4. Turn on the 340nm OptoLED channel at a low intensity.
5. Using the 2.5mm hey key provided, adjust the 340nm LED focus until the image
of the LED comes into sharp focus on the piece of paper.
6. Centre the focussed image of the LED using the 340nm LED X & Y adjustment
screws, using the same hex key.
7. Repeat the steps above for X, Y and Z adjustment for the 385nm LED
4.5 Coupling variation – FuraLED in reflected position of dual port coupling
Figure 12: FuraLED and dual port coupling configuration
340nm
Transmitted LED
X&Y
adjustments
W.White
385nm
FuraLED
horizontal
adjustment
FuraLED
vertical
adjustment
Transmitted LED
focus
adjustment

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1. Align and focus the FuraLED 340nm and 385nm LEDs as per the previous
instructions in secion 4.4.
2. Align and focus the transmitted LED by referring to the previous instructions in
section 4.1.
3. Perform any final positional adjustment (moving both UV LEDs simultaneously)
via the dichroic mirror. Using the 1.5mm allan key provided, ensure both LEDs are
central using the FuraLED horizontal and vertical adjustments.
Please contact us if you have any questions or issues during OptoLED setup or operation and we will
be happy to help! [e-mail]