How to Choose a Raman Camera

A Raman camera is a highsensitivity, lownoise, cooled scientific camera (typically a CCD or sCMOS) designed specifically for Raman spectroscopy and Raman imaging. Its core function is to capture the extremely weak Raman scattered light signal and convert it into analyzable spectral and image data.

A Raman camera is not an ordinary camera — it is the "eye" of a Raman spectrometer or Raman imaging system:

Signal source: The sample generates Raman scattered light when excited by a laser. This signal is extremely weak, typically only 10⁻⁶ to 10⁻¹⁰ of the incident light.

Dispersion and imaging: The Raman scattered light is dispersed by a monochromator or grating and then projected onto the camera's twodimensional photosensitive surface according to wavelength distribution.

Photoelectric conversion: The camera converts the optical signal into an electrical signal. One dimension corresponds to wavelength (spectrum), and the second dimension corresponds to the sample's spatial position, ultimately generating Raman spectra and Raman chemical images.

1. Detector Type

• Backilluminated CCD (Deep depletion CCD) – Highest sensitivity, extremely low noise. Suitable for weak signals, routine Raman, and 785nm nearIR. Currently the mainstream choice.

• Backilluminated sCMOS – Fast speed, large array. Suitable for fast imaging, mapping, and live samples, but noise is slightly higher than CCD.

• Frontilluminated CCD – Cheap, but low QE in nearIR. Not recommended for Raman.

2. Quantum Efficiency (QE) – Most Important

QE directly determines whether you can capture the Raman signal. Key wavelengths to check:

• QE at 532 nm

• QE at 785 nm (most common Raman wavelength – must be high)

• QE at 1064 nm (only needed for NIR Raman)

Acceptable standard:

• QE ≥ 70% at 785nm is considered good.

• Backilluminated deep depletion typically achieves 80–90%.

3. Cooling Temperature

Raman requires long exposure times. Cooling determines dark current level.

• Thermoelectric cooling: –50°C to –85°C (mainstream)

• Liquid nitrogen cooling: Below –100°C (ultrahigh sensitivity, bulky)

Selection guide:

• Routine Raman: –70°C is sufficient

• Weak signal / NIR Raman: –80°C to –85°C is more stable

4. Readout Noise & Dark Current

• Readout noise: Lower is better. Generally < 5 e⁻, excellent < 1 e⁻.

• Dark current: Decreases as cooling temperature drops. Determines whether long exposures are usable.

5. Pixel Size & Array Format

Must match the spectrometer slit and resolution:

• Too small pixels → higher noise

• Too large pixels → wasted resolution

Common choices:

• 13–16 μm – best fit for Raman spectrometers

• Array formats: 1024×256, 1024×1024, 2048×2048 are common

6. Spectral Response Range

Must match your laser wavelength:

• 532 nm excitation: cover 400–1100 nm

• 785 nm excitation: cover 800–1050 nm or wider

• NIR Raman: need high QE from 1000–1600 nm

For more information, please contact:

Email: optoskyphotonics@gmail.com

Web: www.optosky.net