applications Microscopy
➤ The company now has
numerous customers in the MEMS, microelectronics and micro-optics markets. For example, one customer in the semiconductor industry needs to scan a full silicon wafer in a very short time, because the wafer is moving through the processing equipment at around 200mm/s. ‘At such speed, there is no time for stopping the wafer and stabilising the stage,’ says Emery. ‘We have to grab measurements on the fl y.’ The camera and stage are electronically synchronised and for such applications Lyncée Tec uses higher power lasers than for its standard systems in order to decrease acquisition time to a minimum. The cameras used for this application have speeds of
up to 50 frames per second, with acquisition times as short as four microseconds. ‘This would not be possible with conventional scanning technology,’ says Emery. ‘And DHM still has a sub- nanometer vertical resolution. This is crucial for our customers in the materials science industry who want to control height or depth of structures, roughness, and shape of critical nano- and micro- structures.’
Using computers the numerical
reconstruction process is very fast and happens in real time, enabling the customer to accept or reject a wafer without slowing down his production line. Emery believes the experience the company has now accumulated in designing and delivering systems to the materials
THE INSIDE VIEW ON ON DIGITAL HOLOGRAPHICS
Digital holographic microscopy is the only label-free microscopy technology available to life scientists that gives quantitative information about the objects under investigation. It can be used to look at transparent objects and has a resolution down to nanometres. It does not require expensive focusing objectives, because focusing is done by the software used to reconstruct the hologram. Built on traditional holography,
digital holography is a method of acquiring and processing holographic measurement data from interfering wave fronts. The scattered light from an object illuminated with a coherent light (usually a laser beam in the visible spectrum) interferes with the light from a reference source and is recorded on a CCD sensor. The image can then be numerically reconstructed as an object from the recorded measured data in a computer. Digital holography typically delivers 3D surface or optical thickness data, hence both visual and quantifi able information about the object. In transmission confi guration
mainly used in cell biology, this quantitative phase corresponds to the delay introduced by the transparent object relative to the
12 ElEctro optics l june 2011
DHM can be used in refl ection mode or transmission mode. Image courtesy of Lyncée Tec
DHM technology has many applications in the material science market, such as giving fast, robust analysis of this micro lens array. Image courtesy of Lyncée Tec
science industry will be valuable as the company builds up its clients in the life-sciences market. ‘At the moment we are selling
more into material science applications, but in the future
delay caused by the background. The delay depends on the object thickness and the optical density of the object. When the optical density is known, the delay is directly proportional to the object thickness. By adding the information from all pixels of an object, the object (for example a cell) volume can be calculated. In refl ection mode, the phase
image reveals the surface topography with a sub-nanometric vertical resolution.
This digital approach to
holography allows the application of computer based procedures at a level unreached in video- microscopy. In particular the DHM principle features software compensation of optical aberrations, digital image focusing and numerical compensation for sample tilt and environmental disturbances. This makes DHM technology a robust method for routine inspections at the nanometre and micrometre scale.
we expect life sciences to be our biggest market,’ says Emery. ‘DHM technology can give life scientists new insights into the complexity of cells and other relevant information which was not available until now.’ He realises that in the life- sciences market, scientists want automated software and features. ‘People don’t want measurements, they want information about their sample,’ he said. So Lyncée Tec is currently adding new modules to its products and enlarging the range of applications its products can be used for. The company manufactures standard and customised models of its products and also acts as an OEM supplier. A key component used in DHM equipment is the laser that is used to illuminate the sample and create the holographic image. Lyncée Tec currently uses laser diodes in its systems whereas PHI uses helium-neon gas lasers. ‘You can theoretically use any type of laser for this application, but our ultimate aim is to use laser diodes,’ says PHI’s Egelberg. ‘However, the price, performance and robustness of even the simplest He-Ne laser are hard to beat, and therefore we also have the option to use a He- Ne laser in our system. To have the same long-term performance in a diode laser the unit or instrument has to be optically, electrically and/ or thermoelectrically stabilised and with small niche markets for the specifi cations needed for digital
www.electrooptics.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36