Lighting system for use in vehicle cabin

A lighting system for use in a vehicle cabin comprises a step lamp arranged to a door, a foot lamp arranged to a seat and a seat lamp arranged to a roof. An ON-OFF circuit turns on the step, foot and seat lamps when the door is opened, and turns off these lamps when the door is closed. An arithmetic circuit controls the step, foot and seat lamps in luminance to obtain a gradual increase in brightness in order of the road and step, the floor and the seat.

BACKGROUND OF THE INVENTION 
The present invention relates to a lighting system for use in a vehicle 
cabin. 
With a vehicle, it is important that a passenger who will get in the 
vehicle in the dark or at night can quickly ensure his security in 
connection with the presence of an object on a seat, etc., and smoothly 
settle in a cabin of the vehicle. 
On the other hand, it is known that human eyes are easy to fix to a spot 
which is sufficiently lighter than its circumference. This is an ocular 
guide effect (see, for example, "Report of Fundamental Research on How 
Guide Lamp is Seen" published in 1984 by Lighting Society in Japan). It is 
also known that one obtains a sense of center when carrying out a space 
perception with a lighter spot as a center (see, for example, "Adjustment 
of Luminance in Living Room" by Sotaro MATSUDA published in 1966 at a 
meeting of Union of Kansai Branches of Electric and Related Societies). 
These effects are commonly applied to interior and exterior lightings. 
With a conventionally proposed lighting system for use in a vehicle cabin, 
however, when any door is opened, lamps such as a ceiling light, etc. turn 
on therewith to uniformly illuminate the entirety of the cabin, producing 
shadows by a structure, etc. in the cabin, resulting in impossibility to 
obtain optimal illumination range and illuminance. Additionally, the 
aforementioned ocular guide effect and sense of center which are favorable 
for the passenger when getting in are out of consideration. 
It is, therefore, an object of the present invention to provide a lighting 
system for use in a vehicle cabin which guides a passenger to a seat in 
providing a space perception with the seat as a center. 
SUMMARY OF THE INVENTION 
According to one aspect of the present invention, there is provided, in a 
method of controlling a lighting system for use in a cabin of a vehicle on 
a road, the vehicle having a door, a step, a floor, a roof and a seat, the 
lighting system including a step lamp arranged to the door, a foot lamp 
arranged to the seat and a seat lamp arranged to the roof: 
checking whether or not the door is opened; 
detecting brightness of the road and step, the floor and the seat when the 
door is opened and generating brightness indicative signals indicative of 
said brightness detected; 
determining luminances of the step lamp, the foot lamp and the seat lamp in 
response to said brightness indicative signals to obtain a gradual 
increase in brightness in order of the road and step, the floor and the 
seat and generating luminance indicative signals indicative of said 
luminances determined; and 
controlling the step lamp, the foot lamp and the seat lamp in response to 
said luminance indicative signals. 
According to another aspect of the present invention, there is provided, in 
a method of controlling a lighting system for use in a cabin of a vehicle 
on a road, the vehicle having first and second doors, steps, floors, roofs 
and seats, the lighting system including first and second step lamps 
arranged to the first and second doors, first and second foot lamps 
arranged to the first and second seats, and first and second seat lamps 
arranged to the first and second roofs: 
checking whether or not the first door is opened; 
detecting brightness of the road and first step, the first floor and the 
first seat when the first door is opened and generating brightness 
indicative signals indicative of said brightness detected; 
determining luminances of the first step lamp, foot lamp and seat lamp in 
response to said brightness indicative signals to obtain a gradual 
increase in brightness in order of the road and first step, the first 
floor and the first seat and generating first luminance indicative signals 
indicative of said luminances determined; and 
controlling the first step lamp, foot lamp and seat lamp in response to 
said first luminance indicative signals. 
According to still another aspect of the present invention, there is 
provided a lighting system for use in a cabin of a vehicle on a road, the 
vehicle having a door, a step, a floor, a roof and a seat, comprising: 
a step lamp arranged to the door; 
a foot lamp arranged to the seat; 
a seat lamp arranged to the roof; 
ON-OFF means for turning on said step lamp, said foot lamp and said seat 
lamp when the door is opened, and turning off said step lamp, said foot 
lamp and said seat lamp when the door is closed; 
a first sensor so constructed and arranged as to detect a brightness of the 
road and step and generate a road/step brightness indicative signal 
indicative of said brightness of the road/step detected; 
a second sensor so constructed and arranged as to detect a brightness of 
the floor and generate a floor brightness indicative signal indicative of 
said brightness of the floor detected; 
a third sensor so constructed and arranged as to detect a brightness of the 
seat and generate a seat brightness indicative signal indicative of said 
brightness of the seat detected; and 
arithmetic circuit means for controlling said step lamp, said foot lamp and 
said seat lamp in luminance in accordance with said step brightness 
indicative signal, said floor brightness indicative signal and said seat 
brightness indicative signal to obtain a gradual increase in brightness in 
order of the road and step, the floor and the seat.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to the drawings, the structure of a first preferred embodiment of 
the present invention will be described. 
Referring to FIGS. 1 and 2, a lighting system for use in a cabin of an 
automotive vehicle includes a step lamp 6 arranged to an arm rest 5 of a 
door 4 for illuminating at least one of a road 1 and a step 3 of a vehicle 
body 2, a foot lamp 10 arranged to a seat cushion 9 of a seat 8 at the 
front thereof for illuminating a floor 7 in a cabin, and a seat lamp 14 
arranged to a side roof rail 13 in the vicinity of a roof 12 for 
illuminating surfaces 9a and 11a of the seat cushion 9 and a seat back 11. 
It is to be noted that a reference numeral 14' designates a seat lamp 
arranged to a side roof rail 13', and corresponding to a door 4' opposite 
to the door 4. 
The lighting system further includes an ON-OFF circuit 32 arranged for 
turning on the lamps 6, 10 and 14 when the door 4 is opened, and turning 
off same when the door 4 is closed, a first sensor 17 arranged for 
detecting the brightness of the road 1 and the step 3, a second sensor 16 
arranged for detecting the brightness of the floor 7, a third sensor 15 
arranged for detecting the brightness of the surfaces 9a, 11a of the seat 
cushion 9 and the seat back 11, and an arithmetic circuit 34. 
The arithmetic circuit 34 controls the step, foot and seat lamps 6, 10 and 
14 in luminance when the door 4 is opened so that the brightness of the 
floor 7 is greater than that one of the road 1 and the step 3, and the 
brightness of the surfaces 9a, 11a of the seat cushion 9 and the seat back 
11 is greater than that one of the floor 7. Additionally, in a second 
preferred embodiment, the arithmetic circuit 34 controls in luminance the 
seat lamp 14' corresponding to the door 4' opposite to the door 4 as 
opened so as to be approximately half the luminance of the seat lamp 14 
corresponding to the door 4. 
Referring to FIG. 4, each of the seat lamps 14 and 14' includes a diverging 
lens portion 19 corresponding to a divergent illumination range 18 for 
lighting up the entirety of the seat 8, and a converging lens portion 20 
corresponding to a spot illumination range 21 for lighting up a part of 
the seat 8. The converging lens portion 20 is useful when a passenger (not 
shown) reads a book, etc., resulting in the increase in utility of the 
seat lamps 14 and 14'. It is to be noted that a reference numeral 22 
designates a rear pillar. 
Referring to FIG. 5, the step lamp 6 includes a red diverging lens portion 
23 for warning a driver in a follower vehicle (not shown) that the door 4 
is opened, and a transparent converging lens portion 24 for lighting up 
the road 1 and the step 3. The red diverging lens portion 23 is effective 
in decreasing a glare of the step lamp 6 which a passenger (not shown) 
will feel when looking same directly. It is to be noted that a reference 
numeral 25 designates an illumination range of the transparent converging 
lens portion 24 which lights up the road 1 as shown in FIG. 1. 
Referring again to FIG. 1, a door switch 27 is arranged to the vehicle body 
2 corresponding to the door 4. When the door 4 is opened, the door switch 
27 turns on the ON-OFF circuit 32 of the lamps 6, 10 and 14 related to the 
door 4, whereas when the door 4 is closed, the door switch 27 turns off 
the ON-OFF circuit 32. 
Referring to FIGS. 6 and 7, the operation of the first preferred embodiment 
will be described. 
First, it is checked whether or not the door switch 27 is turned on (step 
S1). If the answer at the step S1 is YES, the brightness of the road 1 and 
the step 3, the brightness of the floor 7, and the brightness of the 
surfaces 9a, 11a of the seat cushion 9 and the seat back 11 are detected 
by the sensors 17, 16 and 15 (step S2). Luminances L.sub.R, L.sub.F and 
L.sub.S of the step lamp 6, the foot lamp 10 and the seat lamp 14 are 
determined in response to the detected brightness to obtain a gradual 
increase in brightness in order of the road 1/the step 3, the floor 7, and 
the surfaces 9a, 11a of the seat cushion 9 and the seat back 11 (step S3). 
The step, foot and seat lamp 6, 10 and 14 are then controlled to have the 
determined luminances L.sub.R, L.sub.F and L.sub.S (step S4). 
Subsequently, it is checked whether or not the door switch 27 is turned 
off (step S5). If the answer at the step S5 is YES, the luminances 
L.sub.R, L.sub.F and L.sub.S are set to zero, that is, the lamps 6, 10 and 
14 are turned off (step S6). 
Referring to FIG. 2, there is shown a distribution of illuminance according 
to the first preferred embodiment. The illuminance of the road 1 is 10 lx 
in a portion just below the arm rest 5 of the door 4, and it decreases to 
5, 3 lx, . . . in accordance with a distance from the arm rest 5. Since 
only the seat lamp 14 (not shown) is turned on, the illuminance of the 
surface 9a of the seat cushion 9 is between 25 lx and 20 lx, whereas the 
illuminance of the surface 11a of the seat back 11 tends to decrease 
gradually from 20 lx to 10, 3, 2 lx, . . . 
With the foot lamp 10 (not shown) turned on, the illuminance of the floor 7 
is 20 lx in a portion just near the seat cushion 9, and it decreases to 15 
lx in a portion on the side of the front seat 26. Additionally, with the 
seat lamp 14 (not shown) turned on, the illuminance of the seat back 26a 
of the front seat 26 is between 10 lx and 5 lx on a back side thereof. 
As seen from FIG. 2, the brightness of the floor 7 is greater than that one 
of the road 1 and the step 3, and the brightness of the surfaces 9a and 
11a of the seat 8 is greater than that one of the floor 7, thus increasing 
an ocular guide effect toward the surfaces 9a and 11a of the seat 8, 
allowing the passenger to smoothly get in. Additionally, this allows the 
passenger to obtain a space perception with the surfaces 9a and 11a of the 
seat 8 as a center, producing a sense of center, resulting in a direction 
of hospitality to the passenger. 
Referring to FIG. 3, there is shown a distribution of illuminance according 
to the second preferred embodiment, i.e., the distribution of illuminance 
in the event the luminance of the seat lamp 14 (not shown) corresponding 
to the door 4 as opened is set to 100%, while the luminance of the seat 
lamp 14' and the step lamp 10' (not shown) corresponding to the door 4' 
opposite to the door 4 is set to 50%. The illuminance of the road 1 is 10 
lx in a portion just below the arm rest 5 of the door 4, and it decreases 
to 5, 3 lx, . . . in accordance with a distance from the arm rest 5. 
Since the luminance of the seat lamp 14 (not shown) is 100%, and that one 
of the seat lamp 14' (not shown) is 50%, the illuminance of the surface 9a 
of the seat cushion 9 is between 25 lx and 20 lx, whereas the illuminance 
of the surface 11a of the seat back 11 tends to decrease gradually from 20 
lx to 10, 3, 2 lx, . . . On the other hand, contrary to the first 
preferred embodiment as shown in FIG. 2, the illuminance of a surface 9a' 
of a seat cushion 9' on the side of the seat lamp 14' is between 10 lx and 
5 lx, while the illuminance of an arm rest 5' of the door 4' as closed is 
5 lx, indicating that the brightness is extended on the seat 8. 
Even with the step lamp 10' (not shown) turned on, the illuminance of the 
floor 7 is 20 lx in a portion just near the seat cushion 9 and it 
decreases to 15 lx in a portion on the side of the front seat 26, and the 
illuminance of the seat back 26a of the front seat 26 is between 10 lx and 
5 lx on the back side thereof. On the other hand, contrary to the first 
preferred embodiment, the illuminance of the floor 7' adjacent to the 
floor 7 is between 10 lx and 5 lx, indicating that the brightness is 
extended on the floors 7 and 7' the same as the seat 8. 
Additionally, the illuminance of a seat back 26a' of a front seat 26' on 
the side of the door 4' as closed is between 5 lx and 3 lx on the back 
side thereof, indicating that the brightness is extended also on the back 
sides of the seat backs 26a and 26a'. 
As seen from FIG. 3, the brightness of the floor 7 is greater than that one 
of the road 1 and the step 3, and the brightness of the surfaces 9a and 
11a of the seat 8 is greater than that one of the floor 7, thus increasing 
an ocular guide effect toward the surfaces 9a and 11a of the seat 8, 
allowing the passenger to smoothly get in. Additionally, this allows the 
passenger to obtain a space perception with the surfaces 9a and 11a of the 
seat 8 as a center, producing a sense of center, resulting in a direction 
of hospitality to the passenger. Further, the extension of the brightness 
allows the passenger to grasp largely a situation of the entirety of the 
seat 8 or that one of the vehicle, resulting in the increase in a sense of 
security when getting in.