As a variety of makers develop a variety of high-resolution headlighting technologies including µLEDs, DMD, and LCS for advanced ADB, Koito are proposing an original solution based on a mechanical scanning system they call BladeScan.
The main principle is to use a rotating mirror to spread the light horizontally, resulting in efficiency over 35%, compared to under 15% with MEMS, for example, because of its extensive light waste.
Koito say their technology can be produced at low cost because the number of LEDs is low and it doesn’t require expensive special devices. There’s also the future potential to supplant the LEDs by laser diodes to improve intensity and luminance.
Principle of BladeScan
The rotative speed of the reflector is 6000 rpm, corresponding to a frequency of 200 Hz, so the synchronisation of the LEDs with the timing signal extracted from a DC brushless motor needs only a very short time to turn on or off: just 5 μsec (that is five one-millionths of a second!). Optical results are good with a sharp resolution of 0.1° , a flux of 700 lm, Imax of 55 kcd and beam spread of ±15°. Specific attention was given to the reliability of this mechanical system. The module has 12 LEDs and produces a high-definition ADB.
BladeScan in production
SOP was the middle of last year, and BladeScan was installed first on the Japan-market Lexus RX in August 2019, and very rapidly thereafter in the RX for the European-, UK-, and Australian markets. In comparison with the previous model, the three modules are small to save room for the fitting of the bladeScan module.
The night drive was done in an Infiniti equipped with a Bi-LED standard projection module (same as Renault Zoé) and the BladeScan module.
The night drive, done in dense traffic because between 7 and 8 pm, allowed for evaluation of the performance of the BladeScan ADB and also the other functions.
Very high performance: good homogeneity, wide spread, and an intense hot spot.
Unfortunately, the low aim angle severely limited seeing distance. The same car will be presented for the night drives at VISION, with a more appropriate aim angle.
It was difficult to evaluate the high beam because almost never in one hour we could use it; the traffic was too dense. Nevertheless, we did our best; our impression is that when the speed is higher than 80 km/h, the two modules (standard Bi-LED module and ADB) work together and the performance is great, but at lower speeds the high beam is weak.
ADB with BladeScan
ADB works at road speeds over 30 km/h and with the low beam of the standard module.
On a positive side, I was impressed by:
• the high resolution of the ADB: the width of the shadow was very close to width of the de-glared car, much better than a 12-segment matrix beam thanks to BladeScan’s resolution of about 0.1° versus 1°, and
• the freedom from “dancing light” effects: just smooth, unobtrusive movement of the light.
On the negative side of the ledger, I was disappointed by:
• slow movement of the shadow to track accurately the de-glared car on a curving road, so we don’t have the benefit of the ADB during this time, around one second.
• weakness of the intensity and light flux of the ADB when we passed a car. We clearly saw the low beam cutoff with hard darkness above it. It is probably because of a requirement from Lexus RX in order to make a balance between styling (module lens size) and performance. The car will be presented in the VISION night drives and Koito will update the headlamp in order to improve it by then.
• no light above the car, and no road marking possibility, compared to what we have seen with the 10- to 50-kilopixel µLED systems.
Before the night drive, I was skeptical of the scanning technology and the compactness of the module. After the night drive, I have an easier time believing in the potential of this technology, but it still poses some major developmental challenges. The quantity of light and the speed of the movement have to be improved. There is also the open question of its price; Koito say it will be somewhere in between matrix and µLED technologies.
Congratulations are in order for this nifty technology, let’s see how it will further develop!