Optical technologies from ZEISS

Work on a testing system for photomasks with optics from ZEISS

Work on a testing system for photomasks with optics from ZEISS

Microchips in the Spotlight

Light: The Basic Enabler of Modern Communication

Smartphones, cameras, laptops: without these electronic devices, life as we know it is practically unimaginable. Larger and larger volumes of data can now be stored and transmitted. Light forms the basis of modern information and communication technology.

Its applications extend from data transfer using optical fibers in fiber optic cables through the storage and processing of data on microchips.

ZEISS technologies play a key role in the manufacture of powerful microchips. In an exposure method known as lithography, focused light beams are used to generate tiny structures on the microchips. For this process, photomasks that contain all the information required to produce the final circuits must firstly be produced.In a procedure carried out inside a wafer scanner, light is transmitted through the photomask onto the "wafer" – a silicon disk with a photoactive lacquer.Using a ZEISS lens, the structures on the mask are demagnified by a factor of four.Following exposure, the wafer is developed like an analog film. The lacquer on the exposed parts of the wafer disintegrates during this process. As a result, these tiny areas are conductive, meaning that they can act as a basis for circuits.

ZEISS technologies are also used in process inspection in the semiconductor industry.As the photomasks contain all relevant data that has to be transferred onto the wafers, they must be free from any critical defects. This is the only way they can be used to make fully-functioning chips.Solutions from ZEISS allow defects on masks to be reliably analyzed and repaired with sub-nanometer accuracy. And all with the aid of light!

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Typical scene from the optical production area

Typical scene from the optical production area

Thin layers make all the difference

"Mirror, mirror on the wall..."

Practically every child has heard this question that Snow White's stepmother asked her magic mirror.Even if mirrors can only perform magic in fairy tales, they definitely have something magic about them: a thin layer of material is applied to glass and, abracadabra, we can see our own reflection!

The idea to apply an additional layer to a glass surface and therefore improve its optical properties led to the founding of a special field of optics.Thin optical layers determine whether light is transmitted or reflected.

As a key technology, they are a key component of any optical system and can be found practically everywhere in our daily lives.

On eyeglass lenses, in particular, they ensure that the wearer enjoys clear vision without reflections or prevent ultraviolet radiation from entering the eye.Even the rescue blanket in first aid kits is based on thin layer technology. Scientists also use these thin layers: in modern microscopes or in large telescopes.

ZEISS played a pivotal role in the ongoing enhancement of thin layer optics: in 1935 ZEISS scientists in Jena developed the "T-coating."This is still used to this very day to reduce irritating reflections and increase transmission on optical glass surfaces. To apply the layer, the desired material is first vaporized. It later precipitates on the substrate material and forms a solid layer in the micrometer to nanometer range. These thin layers determine the physical properties and fields of application of the substrate material coated with it.

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Classical ZEISS blink comparator

Classical ZEISS blink comparator

Major discoveries in a flip book

(Dwarf) Planet Pluto discovered with blink comparator from ZEISS

When physicist Carl Pulfrich developed his blink comparator at ZEISS in 1904, he had no idea of just how many important discoveries would be made with his invention.

The instrument makes it possible to switch quickly between two photographs.This is comparable to a flip book – but with only two pictures.If the two images show the same section of the sky at different times, for example, it is easier to distinguish differences between the photographs.In particular, this makes movements and brightness fluctuations visible.

In 1912, using the technology developed at ZEISS, Henrietta Swan Leavitt discovered the relation between the changes in the brightness of certain stars and their luminosity.The slower the brightness of a star changes, the more radiation it emits.However, not all of this radiation actually reaches the Earth.If the total calculable radiation is compared to that measured on the Earth, the difference can be used to determine the distance of the earth from that star.Edwin Hubble later used this method to calculate the distance to our neighboring galaxy Andromeda for the very first time.

Probably the most famous discovery with a ZEISS blink comparator was made in 1930: the young research assistant Clyde Tombaugh discovered the then ninth planet Pluto at the Lowell Observatory in Arizona (USA).He achieved this by comparing two photos that he had taken on 23 and 29 January.He saw that one of the supposed stars was moving in relation to the others. This is typical of planets.

Due to the increasing use of digital camera technology, the blink comparator has now largely lost its significance. Nowadays, it is almost only used for archive research or as a museum piece.

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The Alfred Jensch telescope observing the moon (source: Christian Högner, Thuringian State Observatory)

The Alfred Jensch telescope observing the moon (source: Christian Högner, Thuringian State Observatory)

Captured light from the universe

How the Tautenburg telescope captures light from alien worlds

Tautenburg, a small town around 15 kilometers to the northeast of Jena, has been home to Germany's largest optical telescope since 1960.The Alfred Jensch telescope, which was named after its ZEISS designer, is the most important observation instrument of the Thuringian State Observatory and is a real all-rounder.

It can be used in three different optical configurations.The telescope consists of both mirrors and lenses.The centerpiece of the system is a mirror two meters in diameter which collects the incident light for observation purposes.

When configured in what is known as the Schmidt mode, the telescope is particularly suitable for taking photographs of astronomical objects.Aberrations are reduced by a specially ground corrective lens at the telescope's aperture. In this setting the Tautenburg telescope is the world's largest Schmidt telescope.

The observation instrument can be additionally used for spectroscopy.Here, the light of the stars is broken down into its various components in order to find out more about their chemical composition. This mode is even useful for locating planets around other stars.

When the idea to build this telescope emerged, a universal telescope of this type had never existed before.Hans Kienle, Director of the Astronomical Observatory in Potsdam, awarded the contract to ZEISS in 1949. It took 11 years before the first observation was made in Tautenburg, during which our neighboring galaxy Andromeda was photographed.

Since then, the Thuringian telescope has repeatedly played a key role in modern astronomical research.

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Widefield fluorescence photograph of kidney cells with the ZEISS ApoTome 2 (source: Michael W. Davidson, Florida State University, USA)

Widefield fluorescence photograph of kidney cells with the ZEISS ApoTome 2 (source: Michael W. Davidson, Florida State University, USA)

Fluorescent cells

Fluorescence microscopes enabled detailed insights for biology and medicine

It was pure coincidence that ZEISS staff member August Köhler discovered fluorescence in 1904. He was working on an ultraviolet (UV) microscope when he observed a glow emanating from a crystal he was examining.

At first, it seemed to be an irritating side-effect, but Köhler then saw that it could be useful. In 1908 he presented the first microscope that used this effect in Vienna. Initially, the invention was used primarily by botanists and microbiologists. In the mid 1920s, this type of microscopy also made its way into medical research.

The principle is simple: certain dyes in a specimen - the fluorophores - are excited by high-energy radiation and can then radiate themselves. This glowing of the specimen is called fluorescence. It often occurs in the form of faint green or red light.

The Nobel Prize for Chemistry in 2008 marks a further milestone in fluorescence microscopy. Osamu Shimomura, Martin Chalfie and Roger Y. Tsien discovered the green fluorescent protein GFP in the jellyfish Aequorea victoria. Later they combined the GFP gene with other genes that form proteins. A glow then showed when an organism produced these proteins. As a result, scientists can use a light microscope to observe the activity of a protein in living cells live. For this purpose, ZEISS now offers laser scanning microscope systems that enable three-dimensional insights into these processes with high resolution and maximum protection of the specimen.

Modern fluorescence microscopy techniques such as photoactivated localization microscopy (PALM) can even use fluorescent proteins to circumvent the resolution limit of light microscopes postulated by Ernst Abbe.

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The ZEISS Planetarium in Jena (source: Sternevent GmbH)

The ZEISS Planetarium in Jena (source: Sternevent GmbH)

Heaven on earth

How Jena has influenced the history of planetariums

The Zeiss Planetarium in Jena opened on 18 July 1926, making it the world's oldest functioning planetarium.Thanks to its new projection technology from ZEISS, it is also now one of the world's most modern planetariums.

The idea to create an artificial sky was first thought of in the north of Germany during the 17th century.Up to 12 people could fit inside a giant, three-meter globe where they marveled at the gold-plated nails on the ceiling glimmering in candlelight,which recreated the constellations in the night sky.

Erhard Weigel, a scholar in Jena, heard about this new technology and built a similar system on the roof of the castle in Jena in 1661. The stars were created by holes in the outer wall of a five-meter dome.

This led Oskar von Miller, founder of the Deutsches Musem in Munich, to contact Dr. Walther Bauersfeld at Carl Zeiss in Jena in 1913 about the construction of a "rotatable star dome."However, it did not seem possible to build a large, heavy dome to move with the stars.Instead, Bauersfeld wanted the stars to move independently and designed a device on the basis of opto-mechanical light projection.The first projector from ZEISS incorporated 31 projectors to beam 4500 stars onto the inside of the dome. The first show was held in the Munich planetarium in 1923.

ZEISS in Jena continued to enhance the projector and installed a trial projector on the roof of the factory – also making it available for public shows.Almost 80,000 people visited the "Wonder of Jena" from August 1924 to January 1926.This popularity led to the construction of the current ZEISS planetarium.

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Step in the SMILE technique

Step in the SMILE technique

When light sharpens vision

Precise laser surgery corrects defective vision the gentle and fast way

Laser light and the eye – this can be a dangerous combination.That is precisely the reason why protective goggles have to be worn in many laser labs, and also why caution must be taken when using laser pointers.However, lasers can also be used to correct defects in our vision.

In laser surgery the corneal curvature of nearsighted and farsighted patients is modified using laser light - in just a few minutes and practically without pain. The result: the patient's surroundings are focused clearly and sharply on his or her retina again.

The most common method used worldwide to correct defective vision using a laser is the LASIK technique.Here a flap is made in the upper layer of the cornea and is then folded upwards.Under this the corneal curvature can then be modified.To achieve this, doctors use lasers that emit ultraviolet light in short pulses.This light has the power to vaporize corneal tissue at exactly the required spot and with exactly the amount required to ensure that the cornea receives the desired shape and the patient's defective vision is corrected.During this process the surrounding tissue is exposed to practically no heat. In Germany alone, around 130,000 patients undergo refractive surgery every year.

In collaboration with ophthalmologists from all over Germany, ZEISS has developed systems for the most modern method of laser surgery – the SMILE technique.This is an even gentler procedure: a lens-shaped disk, or lenticule, is cut out of the cornea without causing any damage to its surface.The laser strings together tiny bubbles and in this way severs the disk that is then removed through a tiny lateral incision.This changes the corneal curvature and the patient can see clearly again. Therefore, laser light and the eye can definitely also be a good combination.

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View of the cytoskeleton with PALM (source: S. Niwa, N. Hirokawa, University of Tokyo, Japan)

View of the cytoskeleton with PALM (source: S. Niwa, N. Hirokawa, University of Tokyo, Japan)

Exploring the cell interior with flashes of light

How glowing proteins help overcome the resolution limit of light microscopes

How are synapses between nerve cells generated? What role do proteins play in life-threatening diseases? All of these questions can be examined by super-resolution microscopy as this allows the imaging of structures measuring only 20 nanometers.

This lies beyond the resolution limit calculated by Ernst Abbe in the 19th century. The scientists Eric Betzig, Stefan Hell and William Moerner received the Nobel Prize for Chemistry for the development of this technology in 2014.

The method developed by Betzig and his colleague Harald Hess – photoactivated localization microscopy (PALM) – is particularly good for the examination of living cells. The ZEISS ELYRA microscope system incorporates this method. In PALM short flashes of light excite fluorescent proteins and make them glow - however, statistically only very few for each flash of light. Images are captured of these until the fluorescence of the images has strongly decreased. After this, a new flash of light excites other proteins.

Because – as defined by Abbe's resolution limit – dots of light that are too close to each other could not be separated from each other, it is always decisive that only very few proteins should always fluoresce. Proteins separated by a large distance, on the other hand, can be located with pinpoint accuracy, even if they initially seem to be distended due to diffraction effects. Algorithms are used to remove these effects mathematically. The frequent repetition of the technique makes every protein fluoresce once. If the single images area added to the calculated positions, an image of the complete cell is obtained. The addition means that the resolution limit of the single images is circumvented, and processes in the cell interior no longer remain a secret.

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Eye measurement with optical coherence tomography

Eye measurement with optical coherence tomography

Eye diseases in focus

Optical coherence tomography: how infrared radiation helps to identify tiny structures in the eye

The road from the lab to the doctor's practice was astoundingly short: it took only six years from the initial scientific description of Optical Coherence Tomography (OCT) to the market launch of the first products.

Today, ophthalmologists all over the world work with OCT systems from ZEISS for the examination of patients suffering from serious retinal diseases.The market success was preceded by the company's close collaboration with the US pioneers of OCT technology initiated in the 1990s.This partnership is in line with a tradition established by company founder Carl Zeiss: to develop products sharply focused on practical requirements by cultivating direct dialog with scientists.The market triumph of OCT technology is also an excellent example of the transfer of research and knowledge from science to industry that is often demanded these days.

As the optical equivalent of acoustic ultrasound technology, OCT delivers an image of the inner structure of a body part. Instead of using high, inaudible tones, however, OCT utilizes light in the infrared range similar to that used in heat lamps.In terms of resolution, light is far superior to sound: with OCT it is possible to distinguish between two points separated by a mere five thousandth of a millimeter – this corresponds to one tenth the thickness of a human hair. The ultrasound normally used on the eye until now achieves a resolution of only a few tenths of a millimeter.

OCT allows the ophthalmologist to detect abnormalities in the individual layers of the retina and on the macula – the point of sharpest vision in the eye. Such changes may be caused by diabetes or old age. In addition, OCT enables the doctor to detect changes to the retinal nerve fibers at an early stage and therefore diagnose the onset of glaucoma.

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Evaluation of the data from the ZEISS IOLMaster

Evaluation of the data from the ZEISS IOLMaster

Measuring the eye – without contact or pain

Optical biometry for enhanced visual performance

As the disease progresses, people suffering from cataract increasingly see their environment as if they were looking through a cloudy piece of glass or water spray. The term "cataract" comes from the Greek word for waterfall. If the condition is not treated, blindness may be the result.

The number of people afflicted by the condition is rising around the globe.However, cataract is relatively easy to treat.The replacement of the cloudy lens with an artificial lens is done on an outpatient basis and is the world's most frequently performed surgery.Almost 90 percent of patients enjoy excellent vision afterwards – many of them without any need for eyeglasses!Here it is essential to select the right artificial lens which requires exact measurement of the length of the eyeball, the corneal radius and the distance between the cornea and the lens.For the past 15 years, ZEISS has offered systems with which doctors can conduct these examinations in a non-contact and therefore painless manner – unlike measurement using ultrasound.The principle of "optical biometry" incorporated in these devices uses the phenomenon of interference, i.e. the superimposition of two light waves where their phase relationship remains constant. To achieve this, a laser is needed as a light source because light waves emitted by a filament bulb change their phase relationship very quickly and randomly.

Produced in Jena to this very day, the ZEISS IOLMaster is one of the most successful ophthalmology products of recent years. After more than 100 million IOL calculations worldwide, the system is now seen internationally as the industry's standard for the exact calculation of artificial lenses for cataract patients.

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