Face image capturing device and driver condition determination device

Patent metadata

Field	Value
Publication number	US-10019638-B2
Application number	US-201415104915-A
Country	US
Kind code	B2
Filing date	Dec 8, 2014
Priority date	Dec 18, 2013
Publication date	Jul 10, 2018
Grant date	Jul 10, 2018

Abstract

In a face image capturing device, a focal point of a fixed-focus in-vehicle camera is set to a position where a circle of confusion with respect to a foremost face position is larger than the circle of confusion with respect to a rearmost face position. The rearmost face position is where the driver's face is positioned when a driver's seat is moved to the rearmost limit. The foremost face position is where the driver's face is positioned when the driver's seat is moved to the foremost limit. When the focal point of the in-vehicle camera is set to the above position, the focal point can be moved rearward to reduce the blurring of a face image at the rearmost face position. Even if the blurring of the face image at the rearmost face position is increased, a driver condition can be accurately determined at all times.

First claim

The invention claimed is:

1. A driver condition determination device that is mounted in a vehicle capable of permitting a driver to adjust a position of a driver's seat-in a front-rear direction and is used to analyze a face image of the driver in order to determine a driver condition that affects driving of the vehicle, the driver condition determination device comprising:
a face image capturing device that is used to capture the face image of the driver from a front of the driver; and
a driver condition determination section that determines the driver condition by analyzing the face image captured by the face image capturing device, wherein
the face image capturing device includes an image sensor that generates image data of the face image,
the face image capturing device includes an imaging optical system that forms the face image on the image sensor,
the imaging optical system has a focal point fixed at a position where a circle of confusion with respect to a foremost face position is larger than a circle of confusion with respect to a rearmost face position, the rearmost face position being where the face of the driver is positioned when the driver's seat is moved to a rearmost limit, the foremost face position being where the face of the driver is positioned when the driver's seat is moved to a foremost limit,
the driver condition determination section normalizes the face image captured by the face image capturing device to a predetermined size and analyzes the normalized face image, and
the driver condition determination section enlarges the face image captured at the rearmost face position to the predetermined size as the normalizing the face image and analyzes the enlarged face image.

2. The driver condition determination device according to claim 1 , wherein the focal point of the imaging optical system is fixed at a position where a value of a modulation transfer function (MTF) at the foremost face position is smaller than a value of the MTF at the rearmost face position.

3. The driver condition determination device according to claim 1 , wherein the focal point of the imaging optical system is fixed at an intermediate position between the foremost face position and the rearmost face position or at a position farther away from the imaging optical system than the intermediate position.

4. The driver condition determination device according to claim 1 , wherein an f-number of the imaging optical system is set to a value not greater than 2.0.

5. The driver condition determination device according to claim 1 , wherein the driver condition determination section reduces the face image captured at the foremost face position to the predetermined size as the normalizing the face image and analyzes the reduced face image.

6. The driver condition determination device according to claim 5 , wherein the imaging optical system has the focal point fixed at the position where a circle of confusion of the reduced face image is equal in size to a circle of confusion of the enlarged face image.

Assignees

• Denso Corp

Inventors

• Omi Takuhiro

Classifications

• G03B3/02 Primary

  moving lens along baseboard · CPC title

• G06V20/597

  Recognising the driver's state or behaviour, e.g. attention or drowsiness · CPC title

• H04N23/611

  where the recognised objects include parts of the human body · CPC title

• H04N23/69

  Control of means for changing angle of the field of view, e.g. optical zoom objectives or electronic zooming · CPC title

• G06V10/255

  Detecting or recognising potential candidate objects based on visual cues, e.g. shapes · CPC title