Guide/Converting a Miniscope V4 for a different fluorophore

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Part 1: Optical Configuration (Filters & Excitation)

This section covers how to use spectral viewers to check your fluorophore, choose the right excitation LED, and source the correct filters to get the best signal-to-noise ratio.

Identify Your Target Fluorophore

Changing the excitation wavelength starts with knowing your new indicator's spectral profile. Look up the excitation and emission peaks of your target fluorophore (like tdTomato, mCherry, or GCaMP) on FPbase.

Selecting the Excitation LED

We use and recommend the Lumileds LUXEON Z Color Line for its small footprint and high power output.

Choosing the Filter Set

You will need three specific optical components. We recommend ordering custom sizes to fit the V4 housing from Chroma.

Excitation Filter (EX): Cleans up the LED output, passing the peak wavelengths but cutting off sharply before the emission band. Size: 4x4x1.1 mm.
Dichroic Mirror (BS): Reflects the excitation light to the sample and passes the emission light to the sensor. The cutoff wavelength should sit exactly between your excitation and emission peaks. Size: 4x6x1 mm.
Emission Filter (EM): Blocks stray excitation light so only the pure fluorophore signal reaches the CMOS sensor. Size: 4x4x1 mm.

Part 2: Hardware Modification (Replacing the LED)

This section walks you through the physical modification of the Miniscope V4 PCB, in particular the excitation module. Using a hot air rework station and metallic tweezers, you will safely desolder the stock blue LED and reflow the new LUXEON Z LED onto the PCB without damaging surrounding components or lifting pads.

Required Tools

Hot air rework station with bent tips

We like the ATTEN ST-862D hot air gun soldering station with the bent tips.

Precision Metallic Tweezers

Flux (essential for clean SMD reflow)

Kapton Tape

Step-by-Step Instructions To Remove and Replace The LED

Step 1: Board Stabilization

Tape the excitation PCB onto a heat-resistant surface using Kapton tape so nothing shifts during rework:

Step 2: Rework Station Setup

Set the hot air rework station to 375°C with a very low air speed to avoid blowing away components:

Step 3: Desoldering the Stock LED

Apply flux, then hold the bent-tip air gun about 1.5 cm directly above the LED while moving it in circles. Once the solder melts, cleanly lift the LED away with the metallic tweezers.

Step 4: Soldering the New LED

Verify the LED polarity. Place the new LUXEON Z LED onto the pads and applying the same 375°C heat from 1.5 cm away until the solder reflows and the component aligns.

Step 5: Cleanup

Clean the board with isopropyl alcohol (IPA) to remove any residual flux before testing the LED and reassembling the housing.