Occupant detection apparatus

1. An occupant detection apparatus, comprising:

a photographing device configured to face a vehicle rear seat in a vehicle cabin for taking three-dimensional images; and

a control device that includes:

an information extracting section configured to extract image information corresponding to an upper area of a seat back of said vehicle rear seat from the three-dimensional images taken by said photographing device;

a division processing section configured to divide the information extracted by said information extracting section into regions corresponding to respective rear seat sitting areas for a plurality of rear-seat occupants; and

a derivation processing section configured to derive information about each rear-seat occupant in each rear seat sitting area by comparing extracted image information for each region to a state in which the sitting area is unoccupied.

2. The occupant detection apparatus of claim 1 , wherein the derivation processing section is configured to compare the extracted image information for each region to the unoccupied state by determining a difference between the extracted image information and the unoccupied state,

wherein the derivation processing section is further configured to compare the determined difference to a preset value to derive the information about each rear-seat occupant in each rear seat sitting area.

3. The occupant detection apparatus of claim 1 , wherein the extracted image information includes picture elements that correspond to objects imaged by the photographing device,

wherein the extracted image information includes distances that correspond to lengths between the imaged objects and the photographing device, and a frequency of picture elements that occur for each distance.

4. The occupant detection apparatus of claim 3 , wherein the derivation processing section is configured to compare the extracted image information by deriving a first histogram of the frequency of picture elements for each distance.

5. The occupant detection apparatus of claim 4 , wherein the derivation processing section is configured to derive a difference histogram by deducting a second histogram from the first histogram, wherein the second histogram corresponds to the state in which the seat area or rear seat is unoccupied,

wherein the derivation processing section is further configured to compare the difference histogram to a preset value to derive the information about each rear-seat occupant in each rear seat sitting area.

6. The occupant detection apparatus of claim 5 , wherein the derivation processing section includes a histogram computing section and a determination processing section,

wherein the histogram computing section is configured to derive the first histogram and the difference histogram,

wherein the determination processing section is configured to compare the difference histogram to the preset value to derive the information about each rear-seat occupant in each rear seat sitting area.

7. The occupant detection apparatus of claim 1 , wherein the information about each rear-seat occupant in each rear seat sitting area comprises the existence of a rear-seat occupant.

8. An operation device control system, comprising:

an occupant information detecting section configured to detect information about a rear-seat occupant sitting in a vehicle rear seat; and

an operation device configured to be actuated according to a detection result of said occupant information detecting section,

wherein said occupant information detecting section includes an occupant detection apparatus as claimed in claim 1 , wherein said operation device is configured to be actuated according to information derived by said occupant detection apparatus.

9. A seat belt system for installation in a vehicle, comprising:

an occupant detection apparatus as claimed in claim 1 ;

a seat belt configured to be worn by a rear seat occupant sitting in a vehicle rear seat to restrain the rear-seat occupant;

a seat belt buckle configured to be installed in a sitting area of said vehicle rear seat;

a tongue attached to said seat belt and configured to be latched with said seat belt buckle during a seat belt wearing state; and

an informing section configured to provide the position of at least one of said seat belt buckle and said tongue installed for each sitting area where an occupant is sitting, based on information derived by said occupant detection apparatus.

10. The seat belt system of claim 9 , wherein said informing section is configured to provide positions of said seat belt buckle and said tongue to the occupants of the sitting areas.

11. A seat belt system which is installed in a vehicle, comprising:

an occupant detection apparatus as claimed in claim 1 ;

a seat belt configured to be worn by a rear seat occupant sitting in a vehicle rear seat to restrain the rear-seat occupant;

a seat belt buckle configured to be installed in each sitting area of said vehicle rear seat;

a tongue attached to said seat belt and configured to be latched with said seat belt buckle during a seat belt wearing state;

a buckle detecting sensor configured to detect that said tongue is latched with said seat belt buckle; and

an output section configured to output the wearing of said seat belt installed in each sitting area where an occupant is sitting, based on information derived by said occupant detection apparatus and the detection result by said buckle detecting sensor.