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IMAGE SENSORS


types of cellular structure captured in each half via special image-splitting optics, such as Hamamatsu’s W-View Gemini. Te images can then be super- imposed over each other to provide simultaneous dual-wavelength imaging. Te user can control the acquisition time of each sensor half independently of the other, and thereby correct for any intensity differences coming from the two fluorescent dyes, noted Dr Bader. While sCMOS sensors are ideal for life science


imaging, Diezemann commented that the new Sony IMX174 sensor is close to sCMOS sensors in terms of image quality, meaning it too can be used for these low light microscopy applications.


Looking to the future Te trend in microscopy imaging is for large sensors, 2/3-inch or one-inch sensors, to get a wide field of view and higher resolution. For machine vision, however, smaller sensors are preferable to keep the costs down. Diezemann said that the next two years will be


great for IDS and for other camera manufacturers. ‘Sony has a new sensor technology with smaller pixels in their roadmap; they’re going higher resolution, full HD, 4k cinema resolution and higher


Cmosis is moving


towards advanced CMOS technologies


frame rates, 200fps and more. With these sensors you can go into new applications and new markets, which couldn’t be solved years ago,’ he remarked. ‘It’s not possible at the moment to produce a very


small global shutter pixel. I expect that in one year there will be in mass production a global shutter pixel in the 3µm range. Tis means we would have full HD and 4k cinema resolution in cameras with a C-mount lens. Tis is very important for our market. Machine vision needs a small sensor, 2/3- inch or 1/2-inch is best, and we need small pixels, because everyone wants high resolution.’ Cmosis is moving towards advanced CMOS


technologies, according to Dr Hermans, which were originally developed for very small pixels used in mobile phone applications, and applying these to machine vision and other industrial and


SPEEDING UP CANCER ASSESSMENT


At Photonics West in San Francisco, which took place from 7 to 12 February, Adimec and LLTech were presenting a full frame optical coherence tomography (FFOCT) camera. The device was developed as part of the European CAReIOCA project to provide pathologists and surgeons with an endoscopic camera to speed up the assessment of cancerous tissue.


The CMOS sensor at the


heart of the camera was developed by Cmosis and according to Guy Meynants, CTO of the company, the sensor collects 20 times more photocharges than the sensors traditionally used for OCT applications. Kevin Van Esbroeck, Cmosis project manager for the sensor development for CAReIOCA, commented: ‘One of the key things for this application is having high speed in combination with a high full-well capacity and global shutter.’


The camera has been integrated into a handheld endoscope, which takes two images and analyses the difference between them. There is only a very slight difference in the optical signal


Skin sample imaged with the Cmosis CAReIOCA sensor (left) and a conventional OCT camera (right)


between the two images, explained Meynants, and so to get a good signal-to-noise ratio and detect the difference between these two images it requires a high full-well capacity.


The other aspect is the speed of the readout of the pixel array, which has to be fast enough to freeze any movement from either the patient or the surgeon. Sensors for OCT traditionally


have a full-well capacity of around 100,000 electrons, whereas the Cmosis sensor’s full-well capacity is two million, so 20 times higher. It has a large pixel, 12µm, in order to store enough charge inside the photodiode. The two-megapixel global shutter area scan sensor captures sequentially two full field interferometry


professional imaging applications. Kozik at Point Grey stated that industry


consolidation within the image sensor market ‘should help smaller companies increase innovation when compared to Sony, who has been the leader in this regard for many decades’. Tis has been the case in the last year, with On Semiconductor buying Truesense Imaging and Aptina, e2v purchasing AnaFocus, and Cmosis acquiring Awaiba. In terms of Sony’s new Pregius global shutter


CMOS sensors, most expect it will be a popular sensor for machine vision and scientific imaging.


images with different optical path lengths of the tissue. The calculated OCT image represents a slice of the tissue for analysis. Pathologists would normally


have to study cancerous tissue from a biopsy under the microscope. It is hoped, however, that this device will speed up the assessment of cancer cells by giving surgeons and pathologists faster and more detailed access to diagnostic data. Adimec and LLTech have integrated the camera into the FFOCT device. Now, according to Meynants, two hospitals are planning clinical trials using the instrument. The project partners are also analysing the OCT images to develop protocols to recognise certain cancer cells from the images.


Diezemann said: ‘Te CCD market is declining. I predict that there are less than 100 million CCD sensors produced worldwide. Sony knows that CCDs are declining and so the best way is to have the advantages of CCDs like colour reproduction and pixel performance, and to move that into a CMOS sensor. Sony has its own fabs and is the only company that can produce the silicon layer needed for this pixel performance.’ It will be interesting to see the uptake of Sony’s


technology and developments by other sensor manufacturers in the market. O


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