Sensor airflow apparatus

1. An apparatus comprising:

a housing defining a chamber and including a panel including an aperture;

a sensor fixed inside the chamber and having a field of view through a lens and the aperture;

an annular disc attached to the sensor concentrically around the lens and including a radially outer edge contactlessly exposed to the chamber, an annular slot defined by the disc, the slot extending at least 180° around the lens; and

wherein the disc includes a radially inner surface at which the disc is attached to the sensor.

2. The apparatus of claim 1 , wherein the slot extends at least 270° around the lens.

3. The apparatus of claim 2 , wherein the slot extends 360° around the lens.

4. The apparatus of claim 1 , wherein the disc includes a projection contacting the panel.

5. The apparatus of claim 4 , wherein the slot and the projection collectively extend 360° around the lens.

6. The apparatus of claim 4 , wherein the projection is shaped to block airflow from the chamber through the aperture other than through the slot.

7. The apparatus of claim 1 , wherein the disc includes a front surface extending along the slot and facing toward the panel, and the front surface slopes away from the panel from the radially inner surface to the radially outer edge.

8. The apparatus of claim 1 , wherein the disc includes a back surface facing away from the panel and extending from the radially inner surface to the radially outer edge, wherein the back surface is contactlessly exposed to the chamber.

9. The apparatus of claim 1 , further comprising a pressure source positioned to raise a pressure of the chamber above an atmospheric pressure.

10. The apparatus of claim 9 , wherein the pressure source is a blower.

11. The apparatus of claim 1 , wherein the disc is shaped to guide airflow from the chamber into an air curtain across the lens.

12. The apparatus of claim 1 , wherein the lens is convex.

13. The apparatus of claim 1 , wherein the aperture is circular.

14. The apparatus of claim 1 , wherein the panel has a cylindrical shape.

15. The apparatus of claim 1 , wherein the sensor is a first sensor, the apparatus further comprising a second sensor fixed inside the chamber.

16. The apparatus of claim 15 , wherein the aperture is a first aperture, the lens is a first lens, the panel includes a second aperture, and the second sensor includes a second lens defining a field of view oriented through the second aperture.

17. The apparatus of claim 16 , wherein the disc is a first disc, the slot is a first slot, and the radially outer edge is a first radially outer edge, the apparatus further comprising an annular second disc attached to the second sensor concentrically around the second lens and including a second radially outer edge exposed to the chamber, an annular second slot defined by the second disc and the panel extending at least 180° around the lens.

18. An apparatus comprising:

a housing defining a chamber and including a panel including an aperture;

a sensor fixed inside the chamber and having a field of view through a lens and the aperture;

an annular disc attached to the sensor concentrically around the lens and including a radially outer edge contactlessly exposed to the chamber, an annular slot defined by the disc, the slot extending at least 180° around the lens; and

wherein the slot extends at least 270° around the lens.

19. An apparatus comprising:

a housing defining a chamber and including a panel including an aperture;

a sensor fixed inside the chamber and having a field of view through a lens and the aperture;

an annular disc attached to the sensor concentrically around the lens and including a radially outer edge contactlessly exposed to the chamber, an annular slot defined by the disc, the slot extending at least 180° around the lens; and

wherein the disc includes a projection contacting the panel.

20. The apparatus of claim 19 , wherein the slot and the projection collectively extend 360° around the lens.