Few technologies have impacted the scientific community – and non-scientific community for that matter – as much as digital imaging technology. From exotic, high-speed imaging systems to rugged machine vision systems to a vast array of sophisticated consumer devices, digital cameras are everywhere these days, documenting every aspect of this world we live and work in. Photonics Tech Briefs recently spoke with executives from four well-known imaging companies to get their perspectives on where imaging technology is today, and where it is going in the future.
Our roundtable panel members are Michael Bode, Ph.D., CEO of Ximea Corp.; Robert LaBelle, Ph.D., VP of Marketing for Photometrics and QImaging; Dany Longval, VP of Worldwide Sales for Lumenera; and Andrew Bridges, Director of Sales & Marketing for Photron.
Photonics Tech Briefs: What constitutes current state-of-the-art in high-speed imaging technology?
Dany Longval: There are two main factors that are driving state-of-the-art in high-speed imaging technology. The first is the frame rate at which cameras are capable of taking images. Over the past few years high-speed sensors, such as the Sony ICX674, combined with optimal engineering design, have enabled up to 53 fps at a high resolution. However, being able to capture the image is only one part of the challenge, which leads to the second factor – interface data rate transfer. Until recently, data transfer was limited to sub-5 GB/s speeds unless you were using a proprietary connection. With the introduction of USB 3.0, higher speed transfer of images at up to 5 GB/s to the computer for analysis and storage is possible.
Michael Bode: The question about state-of-the-art high speed imaging has multiple answers. For some applications, the focus is on the fastest exposure time. For these applications there are cameras that allow exposure times in the range of 100s of picoseconds. To allow recording with the highest frame rates, these cameras typically avoid the transfer of the images to a host computer, and record the image sequences directly to the memory of the camera, resulting in limited recording time. For cameras that use a host computer and need to transfer the imaging data for storage, the bottle neck is the transfer medium. Currently there are 4 competing interfaces that allow high speed imaging: Cameralink, Coaxpress, USB3, and PCIe.
Robert LaBelle: As CMOS noise and sensitivity improve, CMOS is now challenging scientific grade CCDs, even EMCCDs, in many difficult low light applications. A good example for scientific imaging are BAE’s sCMOS devices with over 100 frames per second (fps) at 4MP, and a noise floor of only a few electrons.
Andrew Bridges: Framing speed and camera size are probably the two key areas that are reflected in the latest generation of high speed cameras.
PTB: CCD or CMOS – which is the dominant technology today, and which has the most potential for the future?
Bridges: Definitely CMOS is the technology the high speed camera manufacturers are concentrating on. In addition to the greater number of CMOS fabrication facilities that exist worldwide, there is the obvious benefit of no blooming CMOS provides over CCDs. When a CCD pixel is overexposed, the electrons can ‘corrupt’ neighboring columns, resulting in blooming or tearing.
Longval: CMOS is the dominant technology by far but the market data needs to be analyzed carefully. CMOS is dominating consumer applications, but when it comes to industrial and scientific imaging there are applications that are better suited for CMOS and applications that are better suited for CCD. One area where CCD was dominant until recently had been in imaging moving objects because of the intrinsic global shutter nature of CCD sensors. With the introduction of global shutter capabilities, CMOS is now starting to close that gap. Another area where CMOS is closing the gap is with a technology called scientific CMOS. Scientific CMOS combines very low noise performance with high speed capabilities making it a good choice for a number of scientific imaging applications. However, the technology is relatively complex, difficult to use and very expensive.
LaBelle: CCDs are still preferred in long-stare scientific applications like Chemiluminescence due to near perfect photometry, high image quality, high sensitivity and low dark current. Over time, we see CMOS moving to the forefront across all scientific imaging applications as their limitations are addressed.
Bode: Overall, there is no question that CMOS has a far larger market share for area imaging sensors than CCD. In 2012, CMOS sensors had a 92% market share, due to the large consumer market, and the advantage that CMOS can be processed in the same manner as today’s microelectronics, leading to price advantages. CCD sensors typically produce the better images with lower noise, higher dynamic range and sensitivity. CMOS sensors require more electronics close to the active pixel area. This results in more “dead” area for light acquisition, which in turn leads to a sensitivity advantage for CCDs for similar sensors. Newer developments in CMOS technology use back-illuminated CMOS sensors that eliminate this sensitivity disadvantage. A new, exciting variant of CMOS are the sCMOS (scientific CMOS) sensors that combine very low noise with fast readout and high dynamic range, traditionally the strong points of CCD sensors.