The ORCA-Quest quantitative CMOS (qCMOS) camera with photon number resolving functionality is the leap in scientific camera evolution that transforms imaging into imagining (Fig. 1). With ultra-quiet, highly refined electronics, this camera is more than an image capture device; it is a precision instrument that unlocks the ability to investigate new photonic questions because it offers the quality and quantitative performance to detect meaningful data previously lost in the noise. The ORCA-Quest is the world's first camera to incorporate the qCMOS image sensor and to be able to resolve the number of photoelectrons. It features extremely low noise, high quantum efficiency, large area, and high-speed readout.
Figure 1. ORCA-Quest quantitative CMOS (qCMOS) camera
First, let’s be clear: as with any digital imaging device, what is being detected and measured are photoelectrons. Resolving individual photo(electro)ns has primarily been the domain of point detectors such as photomultiplier tubes (PMTs) and avalanche photodiodes (APDs). Photon counting is a measurement technique that relies on the properties of these detectors to indicate whether a photon (or two) has been detected with some level of certainty. But they cannot “count” photons much beyond the threshold of a binary yes or no. In Photon Number Resolving Mode, the ORCA-Quest quantitative CMOS (qCMOS) camera outputs actual counts of photoelectrons per pixel up to a max of 200 photoelectrons (Fig. 2). Single-photon sensitivity in a camera is not achieved through a single specification. To count these photoelectrons, the camera noise must be sufficiently smaller than the amount of photoelectron signal. Conventional sCMOS cameras achieve a small readout noise, but still larger than the photoelectron signal, making it difficult to count photoelectrons.
Figure 2. Comparison of photon number resolving capability
Simplistically, read noise is pixel variation in the conversion of a charge to a digital signal. Each pixel’s photoelectron charge must be detected, converted to voltage, amplified, and digitized. Each of these steps has error associated with it. Read noise is specified as electrons rms to capture in one number the most meaningful spec. But in a camera with 9.4 megapixels, the pixel-to-pixel variation in read noise across the sensor and/or in a single pixel over time can impact image quality and data analysis.
The ORCA-Quest quantitative CMOS (qCMOS) camera pushes that boundary even further and, as can be seen in Fig. 3, has a very narrow read noise distribution, minimizing the salt and pepper visual effect of noisy pixels that can also wreak havoc on computational techniques such as precision localization super-resolution. To detect weak light with a high signal-to-noise ratio, every aspect of the ORCA-Quest, from its sensor structure to its electronics, has been optimally designed. Not only the camera development but also the custom sensor development has been done with the latest qCMOS technology, resulting in extremely low noise performance of 0.27 electrons rms.
Figure 3. Readout noise comparison
A traditional, front-illuminated digital camera is constructed in a fashion similar to the human eye, with a lens at the front and photodetectors at the back. This traditional orientation of the sensor places the active area of the digital camera image sensor on its front surface. The matrix and its wiring reflect a portion of the input photons, and the active area can only receive part of the incoming photons. The reflection reduces the signal that is available to be captured. A back-illuminated sensor contains the same elements, but arranges the wiring behind the active area by flipping the silicon wafer during manufacturing, then thinning its reverse side so that light can hit the active area without passing through the wiring layer. This change can improve the chance of an input photon being captured from about 60% to over 90%.
Back-thinning CCDs for enhanced quantum efficiency (QE) has been done for decades, and EM-CCDs are an example of back-thinned technology becoming commonplace. There are two tradeoffs around back-thinning that are often underestimated: etaloning and impaired resolution as measured by the modulation transfer function (MTF). As with any transformative new product, clever new features take the headlines. But often it is the minimization of age-old nagging issues that frees up the technology for greatness.
Etaloning is a phenomenon that occurs when the incident light interferes with the reflected light from the back surface of the silicon and causes varying sensitivity. This is dependent on both the spatial and the spectral. In the case of an EM-CCD camera, it appears as a fringe pattern even with uniform monochrome light input, mostly in the IR. The quantitative CMOS (qCMOS) camera shows minimal etaloning compared to EM-CCD cameras (Fig. 4).
Figure 4. Etaloning comparison
The modulation transfer function (MTF) is a way to characterize resolution and performance. The MTF indicates how much of the object's contrast is captured in the image as a function of spatial frequency. Resolution is typically considered as the overall number of pixels and pixel size, but pixel structure can also play a role in functional resolution. Every pixel is expected to collect light only from an optically specified area. But if the incoming photons from that area create charge in an adjacent pixel, then there is crosstalk among the pixels and deterioration of resolution. By creating a deep trench isolation structure in the pixel design of the ORCA-Quest quantitative CMOS camera, crosstalk is minimized. This improvement is measured by calculating how many patterned lines of contrasting light and dark can be resolved in a given area. Compared to back-illuminated sCMOS and EM-CCD cameras, the ORCA-Quest shows noticeable improvement in MTF that will produce greater sharpness in images at all magnifications (Fig. 5).
Figure 5. MTF (modulation transfer function) comparison
Brad Coyle has been working in imaging for over 15 years. He joined Hamamatsu 6 years ago and is currently an OEM Camera Product Manager. His expertise includes camera and sensor technologies, and advanced imaging applications. In his spare time, he enjoys playing soccer, cooking, and hiking with his family.
It looks like you're in the . If this is not your location, please select the correct region or country below.
You're headed to Hamamatsu Photonics website for US (English). If you want to view an other country's site, the optimized information will be provided by selecting options below.
For modern websites to work according to visitor’s expectations, they need to collect certain basic information about visitors. To do this, a site will create small text files which are placed on visitor’s devices (computer or mobile) - these files are known as cookies when you access a website. Cookies are used in order to make websites function and work efficiently. Cookies are uniquely assigned to each visitor and can only be read by a web server in the domain that issued the cookie to the visitor. Cookies cannot be used to run programs or deliver viruses to a visitor’s device.
Cookies do various jobs which make the visitor’s experience of the internet much smoother and more interactive. For instance, cookies are used to remember the visitor’s preferences on sites they visit often, to remember language preference and to help navigate between pages more efficiently. Much, though not all, of the data collected is anonymous, though some of it is designed to detect browsing patterns and approximate geographical location to improve the visitor experience.
Certain type of cookies may require the data subject’s consent before storing them on the computer.
This website uses two types of cookies:
There are two ways to manage cookie preferences.
If you wish to restrict or block web browser cookies which are set on your device then you can do this through your browser settings; the Help function within your browser should tell you how. Alternatively, you may wish to visit www.aboutcookies.org, which contains comprehensive information on how to do this on a wide variety of desktop browsers.
Occasionally, we may use internet tags (also known as action tags, single-pixel GIFs, clear GIFs, invisible GIFs and 1-by-1 GIFs) at this site and may deploy these tags/cookies through a third-party advertising partner or a web analytical service partner which may be located and store the respective information (including your IP-address) in a foreign country. These tags/cookies are placed on both online advertisements that bring users to this site and on different pages of this site. We use this technology to measure the visitors' responses to our sites and the effectiveness of our advertising campaigns (including how many times a page is opened and which information is consulted) as well as to evaluate your use of this website. The third-party partner or the web analytical service partner may be able to collect data about visitors to our and other sites because of these internet tags/cookies, may compose reports regarding the website’s activity for us and may provide further services which are related to the use of the website and the internet. They may provide such information to other parties if there is a legal requirement that they do so, or if they hire the other parties to process information on their behalf.
If you would like more information about web tags and cookies associated with on-line advertising or to opt-out of third-party collection of this information, please visit the Network Advertising Initiative website http://www.networkadvertising.org.
We use third-party cookies (such as Google Analytics) to track visitors on our website, to get reports about how visitors use the website and to inform, optimize and serve ads based on someone's past visits to our website.
You may opt-out of Google Analytics cookies by the websites provided by Google:
We inform you that in such case you will not be able to wholly use all functions of our website.