LIQUID DROPLET RECOGNITION APPARATUS, RAINDROP RECOGNITION APPARATUS, AND ON-VEHICLE MONITORING APPARATUS

• US 20100208060A1
• Filed: 01/26/2010
• Published: 08/19/2010
• Est. Priority Date: 02/16/2009
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: KOBAYASHI, Masanori, Hirai, Hideaki, Oouchida, Shigeru, Aoki, Shin
• Granted Patent: US 8,466,960 B2
• Time in Patent Office: Days
• US Class Current: 348/135
• CPC Class Codes: B60S 1/0844 including a camera
• CPC Class Codes: G01N 21/21 Polarisation-affecting properties G01N21/19 takes precedence
• CPC Class Codes: G06V 20/56 exterior to a vehicle by using sensors mounted on the vehicle

Abstract

Disclosed is a liquid droplet recognition apparatus for detecting liquid droplets attached to a front surface of a transparent member. The apparatus includes an image pickup apparatus that picks up a vertically polarized light image and a horizontally polarized light image at the front surface of the transparent member from a side of a rear surface of the transparent member; and a signal processing unit that determines whether the liquid droplets are attached to the front surface of the transparent member based on a polarized-light image ratio composed of the vertically polarized light image and the horizontally polarized light image picked up by the image pickup apparatus.

Claims

1. A liquid droplet recognition apparatus for detecting a liquid droplet attached to a front surface of a transparent member, the apparatus comprising:

an image pickup apparatus that picks up a vertically polarized light image and a horizontally polarized light image at the front surface of the transparent member from a side of a rear surface of the transparent member; and

a signal processing unit that determines whether the liquid droplet is attached to the front surface of the transparent member based on a polarized-light image ratio composed of the vertically polarized light image and the horizontally polarized light image picked up by the image pickup apparatus.

2. The liquid droplet recognition apparatus according to claim 1, wherein

the image pickup apparatus comprises:

a lens array having plural image pickup lenses on a same substrate;

a filter that is separated into two polarizer regions with transmission axes orthogonal to each other so as to correspond to light fluxes passing through the plural image pickup lenses of the lens array; and

an image pickup unit having a plurality of image pickup regions that pick up an image of a subject by receiving light passing through the respective polarizer regions of the filter, and

the vertically polarized light image is picked up by any of the plural image pickup regions of the image pickup unit and the horizontally polarized light image is picked up by another of the plural image pickup regions thereof.

3. The liquid droplet recognition apparatus according to claim 2, wherein

the signal processing unit comprises an image position correction unit that corrects a parallax positional shift between the vertically polarized light image and the horizontally polarized light image picked up by the plural image pickup regions.

4. The liquid droplet recognition apparatus according to claim 1, wherein

the image pickup apparatus comprises:

a image pickup lens;

a beam splitter that separates a light flux passing through the image pickup lens into two parallel light fluxes;

a filter that is separated into two polarizer regions with transmission axes orthogonal to each other so as to correspond to the two parallel light fluxes separated by the beam splitter; and

an image pickup unit that picks up an image of a subject by receiving light passing through the two polarizer regions of the filter, and

the vertically polarized light image is acquired by the light flux passing through one of the two polarizer regions of the filter and the horizontally polarized light image is acquired by the light flux passing through the other of the two polarizer regions thereof.

5. The liquid droplet recognition apparatus according to claim 2, wherein

the two polarizer regions of the filter have a multilayer structure in which a plurality of transparent materials with different refractive indexes are laminated together on a transparent substrate and have one-dimensional periodic irregularities repeatedly formed in one direction for the layers.

6. A raindrop recognition apparatus using the liquid droplet recognition apparatus according to claim 1, wherein

the image pickup apparatus is provided inside a vehicle and detects a raindrop attached to a front surface of a windshield of the vehicle.

7. The raindrop recognition apparatus according to claim 6, further comprising:

a light source that irradiates a region of the windshield of the vehicle with illumination light of a wavelength range not visible to a human eye to be picked up by the image pickup apparatus.

8. An on-vehicle monitoring apparatus comprising:

a light source;

a pair of image pickup apparatuses; and

a signal processing unit;

wherein the light source, the pair of image pickup apparatuses, and the signal processing unit are mounted on a vehicle;

the light source irradiates a windshield of the vehicle with a parallel light flux at an incident angle of Brewster'"'"'s angle,

one of the pair of image pickup apparatuses picks up an S-polarized light image and a P-polarized light image by receiving reflection light of the light flux irradiated from the light source to the windshield while picking up an image of a subject ahead of the vehicle,

the other of the pair of image pickup apparatuses picks up an image of the subject ahead of the vehicle, and

the signal processing unit has a raindrop detection processing unit and an external information processing unit,

the raindrop detection processing unit determining whether a raindrop is attached to the windshield based on a reflectance difference between the S-polarized light image and the P-polarized light image picked up by the one of the pair of image pickup apparatuses and

the external information processing unit calculating a distance to the subject based on the images of the subject ahead of the vehicle picked up by the one of the pair of image pickup apparatuses and the other of the pair of image pickup apparatuses.

9. The on-vehicle monitoring apparatus according to claim 8, wherein

the one of the pair of image pickup apparatuses comprises:

an image pickup lens;

a polarized light filter that is provided on an outgoing side of the light flux passing through the image pickup lens and has two polarizer regions where polarized light is separated by transmission axes orthogonal to each other and a region where the polarized light is not separated; and

an image pickup unit having a plurality of image pickup regions that pick up an image of a front surface of the windshield by receiving light passing through the respective regions of the polarized light filter, and

the one of the pair of image pickup apparatuses acquires the S-polarized light image from the light flux passing through one of the two polarizer regions of the polarized light filter and acquires the P-polarized light image from the light flux passing through the other of the two polarizer regions thereof.

10. The on-vehicle monitoring apparatus according to claim 8, further comprising:

another light source besides the light source;

wherein

the light source and the other light source irradiate different regions of the windshield of the vehicle with parallel light fluxes at an incident angle of Brewster'"'"'s angle,

the pair of image pickup apparatuses pick up S-polarized light images and P-polarized light images by receiving reflection light of the light fluxes irradiated from the light sources to the different regions of the windshield while picking up images of the subject ahead of the vehicle, and

the raindrop detection processing unit of the signal processing unit determines whether a raindrop is attached to the windshield based on a reflectance difference between the S-polarized light images and the P-polarized light images picked up by the pair of image pickup apparatuses.

11. The on-vehicle monitoring apparatus according to claim 8, further comprising:

another pair of image pickup apparatuses besides the pair of image pickup apparatuses, the pair of image pickup apparatuses being used for measuring a short distance and the other pair of image pickup apparatuses being used for measuring a long distance;

wherein

the external information processing unit of the signal processing unit calculates a distance to the subject based on the images of the subject ahead of the vehicle picked up by the pair of image pickup apparatuses for measuring the short distance and the other pair of image pickup apparatuses for measuring the long distance.