Automatic headlight control Automatic headlight control

Automatic headlight control

Automatic headlight control is a function that automatically controls headlights, turning them on and off according to the ambient brightness.
In Japan, since April 2020, all new passenger vehicles are required to be equipped with this function, in order to improve safety (applicable from October 2021 to vehicles in continuous production). While some automobiles have been equipped with this function for some time, the legal obligation has added the criteria that “this function cannot be turned off while driving” and “the standards for brightness in the periphery to turn on the light must be clearly defined.” With these changes, sensors that detect brightness must now reach a higher level of sophistication.


For many years, Hamamatsu has been providing photosensors (illuminance sensors) for detecting brightness in the periphery, for use in automatic headlight control. We are capable of offering products that have both the optimal quality and characteristics.

Mechanism of automatic headlight control (application of illuminance sensors)

The automatic headlight control function detects brightness outside the vehicle with an illuminance sensor installed near the dashboard, in order to control when the lights turn on and off. It turns on headlights when the amount of light picked up by the illuminance sensor drops below a certain level.

Mechanism of automatic headlight control (application of illuminance sensors)

Recommended products

Illuminance sensors

Hamamatsu offers highly reliable illuminance sensors compliant with in-vehicle standards.


■ Features
・ Spectral response close to human eye sensitivity (sensitivity nearly limited to visible light)
・ Wide operating temperature range: -40 to +105 ℃(S11153-01MT)
・ Low price
・ Compact and lightweight
・ Strong resistance to electromagnetic induction noise
・ High reliability
・ Ideal for mass production

S9705 is a digital output sensor that converts illuminance into frequency.

S11153-01MT is an analog output sensor with spectral response close to human eye's sensitivity. It achieves a wide operating temperature range (-40 to +105 ℃).

Spectral response (S11153-01MT)

Graph showing spectral response (S11153-01MT)

Application examples of illuminance sensors

Display brightness adjustment

Illuminance sensors built into displays on speedometers and the like operate by detecting ambient brightness, in order to automatically adjust the brightness of the display. This makes it so the display has a brightness that feels “just right” to humans.

Auto anti-glare mirror

Illuminance sensors built into rear-view mirrors detect strong light (high beams) from following vehicles, in order to automatically adjust reflectance of the mirror and keep from dazzling drivers.

anti-glare rear view mirror

IC technology

We incorporate a photodiode and peripheral circuit into a single IC package, so it can contribute to reducing the number of parts and mounting space. We also offer custom support for this type of specification.

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