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Previous Post. Next Post. Search Our Site: Need Help? Our experienced sales representatives will help you find the best solution for your application. It is fully possible to upgrade the existing architecture of a digital microscope with a miniaturized imaging system, taking up less space than the previous generation.
Just like the progression of smartphone imaging devices, miniaturized microscopes will only improve in terms of performance, size and versatility of application as sensors become better, smarter, more economical and smaller.
And that will mean a clear competitive advantage for biomedical imaging companies that adopt this technology sooner. Stefan Seidlein has been working for Jenoptik since in various positions in the field of Digital Imaging. As product manager, he currently focuses on the light microscope camera product portfolio and brings his entire digital imaging competence and experience to projects.
As a graduated technician with a focus on energy technology and process automation, he is fascinated by digitalization and the many opportunities it offers both individuals and Jenoptik. February , Stefan Seidlein. Biological imaging has evolved from a passive observational collector of descriptive pictures to a keen, versatile and quantitative analytical tool. Microscopic images of tissues and cells provide the basis for characterization and measurements of disease progression, live cell imaging, automated diagnostics, and a host of other activities in the life science and medical diagnostic laboratory.
Digital microscopes thus play a crucial role in the signal pathway between the biological sample of interest and the eyes of the scientist. The end of the line for CCD? As a result of this investment, we witnessed great improvements in image quality, even as pixel sizes shrank.
Therefore, in the case of high volume consumer area and line scan imagers, based on almost every performance parameter imaginable, CMOS imagers outperform CCDs. In machine vision, area and line scan imagers rode on the coattails of the enormous mobile phone imager investment to displace CCDs. For most machine vision area and line scan imagers, CCDs are also a technology of the past.
For machine vision, the key parameters are speed and noise. CMOS and CCD imagers differ in the way that signals are converted from signal charge to an analog signal and finally to a digital signal. In CMOS area and line scan imagers, the front end of this data path is massively parallel.
This allows each amplifier to have low bandwidth. By the time the signal reaches the data path bottleneck, which is normally the interface between the imager and the off-chip circuitry, CMOS data are firmly in the digital domain. In contrast, high speed CCDs have a large number of parallel fast output channels, but not as massively parallel as high speed CMOS imagers.
Hence, each CCD amplifier has higher bandwidth, which results in higher noise. To image in the near infrared to nm , imagers need to have a thicker photon absorption region. This is because infrared photons are absorbed deeper than visible photons in silicon. Most CMOS imager fabrication processes are tuned for high volume applications that only image in the visible. These imagers are not very sensitive to the near infrared NIR. In fact, they are engineered to be as insensitive as possible in the NIR.
Increasing the substrate thickness or more accurately, the epitaxial or epi layer thickness to improve the infrared sensitivity will degrade the ability of the imager to resolve spatial features, if the thicker epi layer is not coupled with higher pixel bias voltages or a lower epi doping levels.
Changing the voltage or epi doping will affect the operation of the CMOS analog and digital circuits. CCDs can be fabricated with thicker epi layers while preserving their ability to resolve fine spatial features. CCDs that are specifically designed to be highly sensitive in the near infrared are much more sensitive than CMOS imagers.
Since ultraviolet photons are absorbed very close to the silicon surface, UV imagers must not have polysilicon, nitride or thick oxide layers that impede the absorption of UV photons. Modern UV imagers are hence backside thinned, most with only a very thin layer of AR coating on top of the silicon imaging surface. Although backside thinning is now ubiquitous in mobile imagers, UV response is not. Many backside thinned imagers developed for visible imaging have thick oxide layers that can discolor and absorb UV after extended UV exposure.
Some backside thinned imagers have imaging surfaces that are passivated by a highly doped boron layer that extends too deep into the silicon epi, causing a large fraction of UV photogenerated electrons to be lost to recombination.
UV response and backside thinning are achievable in all line scan imagers, but not all area imagers. No global shutter area CCD can be backside thinned. The situation is better in CMOS area imagers, though still not without trade-offs. CMOS area imagers with rolling shutter can be backside thinned. Conventional CMOS global shutter area imagers have storage nodes in each pixel that need to be shielded when thinned, but only if these UV sensitive imagers will also be imaging in the visible.
There are other types of CMOS global shutter area imagers that do not have light sensitive storage nodes, but have higher noise, lower full well, rolling shutter, or a combination of these. Aside from area and line scan imagers, there is another important type of imager. Time delay and integration TDI imagers are commonly used in machine vision and remote sensing and operate much like line scan imagers, except that a TDI has many, often hundreds, of lines.
As the image of the object moves past each line, each line captures a snapshot of the object. TDIs are most useful when signals are very weak, since the multiple snapshots of the object are added together to create a stronger signal. The charge summing operation can be noiseless, but CMOS voltage summing cannot. When a CMOS voltage-domain TDI has more than a certain number of rows, the noise from the summing operation adds up to the point that it becomes impossible to match a charge-domain TDI.
The tradeoff is in speed and cost. For lower numbers of row summing, voltage-domain TDI summing can provide cost-effective high performance, but for the most challenging highest speed, lowest light applications, charge-domain CMOS TDI like that found in Teledyne's Linea HS cameras delivers the highest performance.
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