Zyla's new sCMOS ZL41 Wave camera for physical sciences and astronomy

Andor has introduced a new addition to its popular Zyla line of sCMOS cameras. The new ZL41 Wave camera is specifically designed for scientific research in the physical sciences and astronomy.

What does it offer?

• Up to 82% quantum efficiency

• < 1 e- read noise

• Up to 100 fps

• 32-bit binning mode

• Spectroscopy modes

• Operation to ambient temperatures down to -20°C

Application

• Sky surveys

• X-ray or neutron tomography

• Quantum imaging

• Hyperspectral applications

• High resolution imaging

Read more about the new product on the product page HERE.

sCMOS vs CMOS cameras: what's the difference?

Camera technology continues to evolve and offer better sensitivity, resolution, and speed, which is helping today's scientists in many areas of research. Most modern imaging cameras are based on CMOS (Complementary Metal-Oxide-Semiconductor) sensors, while the once popular CCD (Charge Coupled Device) sensors are now limited to more specialized applications. CMOS cameras come in a wide range of sensor formats and price ranges. One also often sees some cameras labelled as scientific CMOS or sCMOS. So what are the differences between CMOS and sCMOS cameras? And what does this mean in terms of their imaging capabilities and intended use?

What is common to CMOS and sCMOS?

As the names suggest, both CMOS and sCMOS are based on the same sensor technology, namely the construction of complementary metal oxide semiconductor sensors. In short, sCMOS can be thought of as a higher-end, higher-performance CMOS.

What are the differences between CMOS and sCMOS?

The main difference between CMOS and sCMOS is that CMOS cameras are general purpose imaging cameras, while sCMOS cameras are designed specifically for scientific research applications that require accurate and precise signal intensity measurements. sCMOS cameras achieve higher imaging performance in several ways:

Sensors with high QE (quantum efficiency) and low noise for best sensitivity and signal detection.

Sensitivity - or the ability of the sensor to detect signals - is largely determined by the QE and fundamental noise characteristics of the sensor. QE describes how effective the sensor is at converting an incoming signal in the form of light (photons) into an electrical signal. Sensors also have a certain level of noise. Sources of noise are referred to as read noise (the noise of the sensor itself as it measures the signal and reads the value for each pixel) and dark current (thermal noise that occurs in the absence of any signal).

sCMOS sensors with back illuminated detection and thermal noise control

sCMOS sensors typically have a very low read noise of 1-2 e-, which means that the noise floor of the camera is very low and low level signals can be distinguished from the noise floor. CMOS sensors typically have higher read noise, which can be 6-8e- or higher. The read noise describes the measurement variation of the signal. The lower the deviation, the better - i.e. a read noise of 1e- means there is only 1e deviation in the measurement, while a read noise of 10e- means there is 10e deviation in the measurement.

The sCMOS sensors are usually cooled to reduce thermal noise. Imaging sensors are subject to thermal noise which, if not addressed, would increase the noise level of the camera and thus affect the detection limit of the camera. Sensor cooling is an effective way to control thermal noise and is often a key difference between CMOS and sCMOS cameras.

CMOS cameras have passive sensor cooling operating at ambient temperatures, which means that the heat generated by the sensor is dissipated through the metal housing of the camera. This is sufficient for general purpose imaging at short exposures and high signal levels. For fluorescence or spectroscopy applications where signal levels are much lower, or for longer exposures, this thermal noise is detrimental to imaging performance. In addition, the larger the sensor and the faster the camera operates, the more thermal noise needs to be controlled. At higher ambient temperatures or in enclosed spaces, thermal noise can be particularly problematic.

Quantitative accuracy and dynamic range

A key feature of sCMOS cameras is that they are optimised to allow the sensor to be used as an analytical tool for measuring light intensity. In the same way that calibration is performed for experiments, the camera is optimized to ensure that the response of each pixel across the sensor is as accurate as possible. As described above, each pixel of the CMOS-based sensor has its own per-pixel amplifier, with analog-to-digital conversion and line-by-line readout taking place in each column. This allows high frame rates and larger sensor formats to be achieved, replacing slower CCD-based cameras with a serial readout process. However, this means that there is very little variation in the response to light for each pixel and column. These differences are so small that only minimal corrections are necessary if there is sufficient light or the camera is not being used for measurement purposes. For applications where light levels are low or where experimental conditions need to be compared, precise optimization of the sensor is required.

CMOS cameras are designed to provide a good level of performance, enabling fast and easy high-volume production, all while keeping the cost low. sCMOS cameras use many more features of the built-in FPGA to correct for these small differences for individual operating modes. While this increases the price of the camera, it also ensures that the cameras can be used for quantitative measurements. Typically for sCMOS cameras, this specification is stated as the quantitative accuracy or linearity of the camera in the form of 99.7% linearity or 0.3% non-linearity. This specification may be omitted from CMOS camera specification sheets.

Another difference is dynamic range - the ability of the camera to capture both the faint and bright parts of an image in a single frame. Cheaper CMOS cameras often compromise on dynamic range, which means they are more prone to image saturation when processing images with weak and bright signal information. sCMOS cameras often have much wider signal processing capacity in some modes - usually described as 16-bit high dynamic range mode, rather than 8, 10 or 12-bit modes.

Scientific domains and camera capabilities

Many scientific domains such as life sciences, microscopy, astronomy and industrial imaging use both sCMOS and CMOS cameras. The requirements of the application determine which option is best.

• Applications that require excellent image quality, low noise and high sensitivity often choose sCMOS cameras. These include fluorescence imaging, single molecule imaging and super-resolution microscopy.
• For applications requiring high-speed imaging, such as particle tracking, high-speed industrial inspection or capturing fast biological processes, CMOS cameras are suitable.

Choosing between sCMOS and CMOS cameras

When deciding between sCMOS and CMOS cameras for your research, you need to consider the limitations of the experiment. CMOS cameras provide high-speed imaging within the constraints of a small budget, but sCMOS cameras are superior in sensitivity, low noise, and dynamic range. It is important to be aware of the strengths and weaknesses of each technology and compare them on a case-by-case basis with the specific conditions of your experiment.

Scientific cameras, such as the ZL41 Cell, have a high dynamic range but also a linear response to light. This means that the camera responds to the signal linearly, in proportion as the light level decreases to the sensitivity limit. This means that it is possible to quantify the signal and relate it to measurements. Industrial cameras are typically not configured this way and can suffer from non-linearity both at the lower limit and up to the saturation point. In addition, many cameras use multiple amplifiers in order to digitize the entire image information. If they are not configured correctly, skips in the detected signal can occur.

There is also an effect at the individual pixel level. With an sCMOS sensor, each pixel will have a different response to light. Scientific cameras will have efficient pixel maps that account for these differences. This means that it is possible to monitor light levels and when replacement is required.

Key Features:

• Knowledge of the basics: complementary metal oxide and semiconductor technology, common to both CMOS and sCMOS cameras, enables the conversion of light (photons) into an electrical signal.
• Sensitivity and signal-to-noise ratio: sCMOS cameras have very low noise, high quantum efficiency and therefore provide a significant sensitivity advantage over CMOS cameras. CMOS cameras offer a less favourable signal-to-noise ratio as they have higher noise levels and lower QE. Yet they still provide sufficient sensitivity for applications that have large amounts of light. In addition, they are available at much lower prices if the camera design, cooling or optimization is less complex.
• Speed and frame rate: One of the main features of CMOS cameras is the ability to record images at high frame rates. High read rates make them ideal for capturing dynamic events or objects in motion. Although slower than CMOS cameras, sCMOS cameras provide reasonable frame rates that are suitable for a wide range of scientific applications.
• Dynamic Range: sCMOS cameras are often praised for their wide dynamic range, which allows them to capture details in both the bright and dark parts of an experiment. They are therefore very useful in applications that require accurate capture of a wide range of intensities. Although CMOS cameras have good dynamic range, they may not be as capable as sCMOS cameras in this regard.
• Cost and availability: CMOS cameras are more affordable than sCMOS cameras, which is obviously an advantage. Because of their price, CMOS cameras are accessible to a wider range of consumers, especially those with limited resources or funds. On the other hand, sCMOS cameras are usually more expensive due to their higher performance characteristics.