Driving Vision News presents an exclusive interview with Professor Khanh. Prof. Khanh presents his department with 40 students and 7 PhD doctoral students and his works include LED, Adaptive lighting, and Driver assistance systems.
He talks on his relation with car makers and worldwide lighting suppliers Tier 1 and 2 and presents the targets of the expert forum Delris in September at Darmstadt. He finishes the interview with discussion of LED headlamps in cars and in his laboratory.
Driving Vision News: Could you tell us about yourself, your education, career, and hobbies?
Professor Khanh:
I came to Germany in 1979 to study mechanical engineering and optical science. From 1986 to 1989 I worked for my PhD Thesis on optical spectroscopy. Then until 1999, I was laboratory leader in two companies in Berlin and Munich in the field of photometry, colourimetry and especially in UV-radiometry.
From 2000 to September 2006, I was project leader at Arnold & Richter in Munich, a company for cinema film camera, film scanner and digital film production. There, I was responsible for the technical development of optical parts in the world’s first digital cinema camera and LED-luminaires for illumination of TV and Cinema studios. Since October 2006, I am chair of the laboratory of lighting technology at the University of Darmstadt.
DVN: You arrived in Darmstadt 2 years ago, in difficult conditions, one year after Prof. Schmidt-Clausen left the department. How did you start?
Khanh: I’ve always been a startup builder and have had many chances in my career to build a new team working on a new field. In the same way, it was for me a chance to establish a new team of young doctoral students with high engagement. It was the reason why I came to Darmstadt.
DVN: How would you describe the University of Darmstadt and your department?
Khanh: The University of Darmstadt has many great departments for physical science; chemistry, biology, history and sociology, computer science, mechanical and electrical engineering. This was the world’s first department for electrical engineering, 125 years ago. The lighting laboratory in the University of Darmstadt’s department of electrical engineering is for the automotive lighting and is funded by a consortium of 12 companies (car markers and lighting product makers) for 5 years now, and the focus is research and development for this industry.
In Germany, we have 4 lighting laboratories at 4 universities. One laboratory has the focus on illuminating technology in indoor areas, one for daylight and ballast technology, one for OLED and testing of vehicles. In our laboratory in Darmstadt, the focus is vehicle lighting.
DVN: What is your feeling about vehicle lighting and its special community?
Khanh:. From the technological point of view, vehicle lighting has the most innovation degree and the most dynamic development. This special lighting combines optical technology like lenses and reflectors, coating and lamp technology; semiconductor technology like lasers, LEDs, CMOS, and CCD-sensors; mechanical and electrical engineering for display, signal transmission, and thermal management. 
Knowledge of human behaviour and visual physiology is strongly needed for lighting design and driver assistance.
In fact, this community is so special, because nearly all responsible managers and engineers for lighting programmes have high and fundamental knowledge on the main stream of lighting technology. Some of them came from the University of Darmstadt.
DVN: Coming back to your department, how many students do you have? How many companies are involved in your programmes? Where are the main lighting professors from?
Khanh: Today, I have about 40 students in my lecture hall and 6 diploma students. In my laboratory, I have 7 PhD doctoral students, one guest professor for mesopic research, one postdoctoral laboratory engineer, and a project engineer for renewable solar modules. In our programmes, 4 car makers, 2 lamp manufacturers and 5 headlamp makers are strongly and effectively involved. That means that we exchange weekly or monthly our ideas with the partners and make tests and studies for and with them. In the recent time, we have received an order for a study for 3 motorcycle manufacturers. It is new for us.
DVN: Which lighting companies do you work with, and how do you arrange it? Do you work with any non-German companies?
Khanh: Within the field of automotive lighting, we have a close relationship due the consortium I mentioned above. In the beginning, we were active and visited the automotive lighting companies and presented them with lighting concepts we made especially for them. 
Some companies accepted after a certain time our concepts and ideas. After our test programme with LED headlamps for many companies, we have the feeling that the automotive lighting industry has accepted us as competent partner. Since 1 year, some automotive companies have come to us with their own ideas and project planning. Further lighting companies come from the LED industry and street lighting, for which we are developing the LED street luminaries. This is a very fruitful time for us.
Yes, we are working with some well-known non-German Companies. One of them comes from your home country, we have tested their LED headlamp. With two Japanese companies we have a very intensive collaboration. For one of them, we are currently testing the LED headlamp and we plan with the other company to test its driver assistance system in the Spring of 2009.
DVN: You organize every 2 years the famous ISAL symposium. What can you tell us about recent trends and new forecasts for this important congress?
Khanh: ISAL 2005 had 450 attendees and ISAL 2007 had 546. I have a feeling that the trend from ISAL 2005 and ISAL 2007 is similar. The two main concentrations are LED technology, which was to the ISAL 2005 time in the conceptual period and at 2007 with the first LED headlamps on the LEXUS LS600h and Audi R8, and the driver assistance with AFL/AFS-idea.
In the next two or three years, we will have the following trends from my point of view:
• We will have LEDs with light efficacy of 70 lm/W in comparison to 50 lm/w of today’s automotive LEDs. This allows us on one side to develop headlamps with efficiency of more than 50% and in absolute numbers an effective luminous flux of 1100 lm, comparable to HID headlamps. Today, most LED headlamps have 600-800 lm in the beam. However, the first headlamps on the market are planned for high-class cars and limousines.
• AFS/AFL systems with dynamic bending light, city light or motorway light will be realized with LED technology in classical LED arrangements like Ostar from Osram.
• The next step will be light-based AFS/AFL system with LEDs in a matrix beam structure. Other ideas like marking light and glare-free high beam can also realized with LED matrix imaging.
I think that the big problem to be solved in the next future is not the headlamp technology but the camera and sensor technology. The future of driver assistance is dependent on the quality of sensors, sensor fusion and image processing. At this point, we should see the potential for ISAL to organise the discussion.
DVN: You are preparing a forum to go in depth on some technologies with a limited number of participants. Could give us more details of this forum?
Khanh: ISAL in its 2-year interval is internationally recognised as the ideal forum for discussing the latest developments in traffic lighting. The high number of presentations and participants allow a good overview over trends and research activities. Beside this conference platform, we need an expert symposium in a rather small frame with more time and room for a more profound discussion of current issues, with the focus on more visionary topics and discussion about related risks and opportunities. Therefore, and as a reaction to many requests from the automotive industry, we organise the expert forum DELRIS with a small group of about 80 invited experts and 15 invited speakers which will take place at 18th and 19th of September 2008 in Darmstadt.
This forum will have main 4 blocks with lighting systems for reducing the accidence rate, LED technology, driver assistance, and accidence analysis. In the block for LED technology, we will have three participants from Osram, Philips-Lumileds and Nichia. Osram’s participant is Dr. Illek, winner of the German Future prize in 2007 for thin-film-LED-technology. The participant in the driver assistance block is Prof. Isermann, who was selected some years ago as one of the 100 most popular men in the USA. He is my colleague here at Darmstadt, and is developing driver assistance systems for Continental AG in Germany.
DVN: Lighting systems and driver assistance systems are increasingly integrated or at least linked. Does your work extend to some driver assistance subjects?
Khanh: Yes, of course. We have a project for the dynamic cutoff line combining AFS with HID lamps and a camera and image processing system. We are testing the advantages of such a system against low beam and high beam systems. Our experience is that the quality and reliability of the AFS system is strongly dependent on the camera and image processing software.
DVN: Do you have relationship with other universities, labs or institutes?
Khanh: We visited the University of Michigan in April 2008 and the University of Kagawa in Japan in May 2008.
We have a very good relationship with Prof. Schandaon at Hungarian University in Vezprem, in the field of mesopic research.
DVN: What are the main subjects you’re presently studying?
Khanh: At the moment we are studying:
• The effect of the light source spectra on mesopic contrast, reaction time, and acuity to find out the best lamp spectra for headlamps,
• Light-based AFL and its advantages
• High beam assistance
• The advantages of LED headlamps. For this, we have very good relationship to the German, Japanese and French headlamp industries.
DVN: Do you still have studies focused on Xenon light? What percentage of your studies involves LED and other new technologies?
Khanh: More than 50% of our studies involve LED technology. Of my 7 PhD doctoral students, 5 of them are dealing with LED technology. We are intensively dealing with comparison of xenon, halogen, and LED headlamps, and our results are that xenon headlamps have advantages over halogen lamps in visibility distance, brightness, and homogeneity. We find that xenon lamps have equal or less discomfort glare than halogen lamps. For this study, which had duration of 6 months with many real tests on the outdoor area, we used many cars from Audi, Opel, and Mercedes. But we are not paid by these three companies; the results are objective and will be reported at the next SAE conference in 2009.
DVN: LED technology is arriving in headlamps very fast, with the Lexus LS600h, Audi R8, and Cadillac Escalade Platinum. What is your opinion of this technology with regards to seeing, discomfort glare, and disability glare?
Khanh: We are very happy to have the chance to test a lot of LED headlamps. In the same manner, we have the opinion that glare is strongly dependent on the construction of the headlamp and not on the lamp spectra. As mentioned above, the halogen lamps have more or similar discomfort glare than the xenon lamps. In our test, we do not see a systematic tendency of more glare with LED headlamps.
DVN: We will see you in Versailles for the VISION congress. Can you tell us about the paper Darmstadt will present and the message you will transmit to the automotive lighting community?
Khanh: We will be in Versailles with two presentations. The one will report on LED headlamp tests. The message will be that the technical and eye-physiological performances of the tested LED headlamps have exceeded the performance of halogen lamps and come close to that of HID headlamps. The interaction between the LED spectra and the material of the traffic signs has to be analysed, because traffic signs and road markings have a very good visibility if illuminated with LED headlamps.
The second presentation will deal with glare reduction for oncoming traffic with a dynamic cut-off line controlled by a camera system and image processing software. These are two of the most innovative topics in vehicle lighting and we will exchange our experiences with the community at your VISION congress.
