Method for measuring fine particulates and fine particulate sensor for determining the particle size of fine particulates

1. A method for measuring fine particulates in the vicinity of a motor vehicle with an optical receiving device,

wherein

at least one LED arranged inside the motor vehicle lights up an outside air region through a windscreen of the motor vehicle,

the optical receiving device is designed to capture the area under examination in a spatially localised manner and takes an intensity measurement in an area that is lit by the LED,

the intensities measured are analysed for diffraction patterns that depend on the size of the fine particulates,

the radiation emitted by the at least one LED is reflected at least in part by the windscreen, and

the light reflected by the windscreen is received and analysed for wetting of the windscreen by water droplets.

2. The method according to claim 1 , wherein two LEDs light up the outside air region with different wavelengths in the infrared range.

3. The method according to claim 1 , characterised in that the LED radiates into an area in front of a windscreen.

4. The method according to claim 1 , wherein the angle between the primary maximum and the first order maximum in the diffraction pattern is analysed.

5. The method according to claim 1 , wherein the amplitude of the first order maximum is analysed with regard to particle concentration.

6. The method according to claim 1 , wherein the light reflected by the windscreen is also received with the optical receiving device, which is also used to measure the intensities of the fine particulate diffraction patterns.

7. The method according to claim 6 , wherein the LEDs and/or the receiving device are switched on or off in at alternating points in time, so that receiving for analysis of diffraction patterns for fine particulates is carried out at one point in time and evaluation of the reflected light with regard to wetting of the windscreen is carried out at another point in time.

8. The fine particulate sensor according claim 6 , wherein at least one LED uses an optical system present in the rain-light sensor.

9. A fine particulate sensor for a motor vehicle having an optical receiving device,

wherein

the fine particulate sensor comprises at least one LED which lights up an area of outside air,

the optical receiving device is designed to capture an area that is lit by the LED in spatially localised manner,

the fine particulate sensor comprises an analysis device for analysing the diffraction patterns recorded by the optical receiving device, and

the fine particulate sensor is integrated in a rain-light sensor.

10. The fine particulate sensor according to claim 9 , wherein the fine particulate sensor comprises two LEDs.

11. The fine particulate sensor according to claim 9 , wherein the LEDs and the optical receiving device are directed toward a sample space.

12. The fine particulate sensor according to claim 9 , wherein two LEDs use a first optical system and that the optical receiving device uses a second optical system.

13. The fine particulate sensor according to claim 9 , wherein one central receiving device and a plurality of LEDs surrounding the optical receiving device in a ring formation are provided.

14. A motor vehicle having a windshield and a rain-light sensor with a housing and optical systems arranged behind the windshield that are directed toward the windshield,

wherein

a fine particulate sensor according to claim 9 is integrated in the rain-light sensor.