U.S. patent application number 10/758550 was filed with the patent office on 2004-07-29 for capacitance sensor and detector using same for detecting object being caught by door.
This patent application is currently assigned to OMRON Corporation. Invention is credited to Kurumado, Yukinori, Nagayama, Keiichi, Okushima, Akihiro, Shoji, Shinichi, Sueyasu, Hiroyuki.
Application Number | 20040145378 10/758550 |
Document ID | / |
Family ID | 32732742 |
Filed Date | 2004-07-29 |
United States Patent
Application |
20040145378 |
Kind Code |
A1 |
Shoji, Shinichi ; et
al. |
July 29, 2004 |
Capacitance sensor and detector using same for detecting object
being caught by door
Abstract
A capacitance sensor with a directionality characteristic in the
direction of its detection surface is incorporated in a detector
for detecting an object that may be feared to or about to be caught
by a closing door such as a slide door of a vehicle. The
capacitance sensor has a main body enclosing detection electrodes,
an insulating material placed in between and a shield electrode
serving to provide the directionality. A water-repellant finish is
provided at least on a portion of the outer surface of the main
body including the detection surface for preventing water drops
from remaining or becoming larger. The detection surface may be
unevenly shaped with protrusions for making it difficult for water
drops to remain attached.
Inventors: |
Shoji, Shinichi; (Nagoya,
JP) ; Okushima, Akihiro; (Nishi-Kamo-Gun, JP)
; Sueyasu, Hiroyuki; (Kasugai, JP) ; Nagayama,
Keiichi; (Aichi-gun, JP) ; Kurumado, Yukinori;
(Nagoya, JP) |
Correspondence
Address: |
BEYER WEAVER & THOMAS LLP
P.O. BOX 778
BERKELEY
CA
94704-0778
US
|
Assignee: |
OMRON Corporation
|
Family ID: |
32732742 |
Appl. No.: |
10/758550 |
Filed: |
January 14, 2004 |
Current U.S.
Class: |
324/663 |
Current CPC
Class: |
E05Y 2800/40 20130101;
H03K 17/962 20130101; H03K 2217/960725 20130101; E05F 15/46
20150115; E05Y 2900/531 20130101 |
Class at
Publication: |
324/663 |
International
Class: |
G01R 027/26 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 16, 2003 |
JP |
2003-008292 |
Claims
What is claimed is:
1. A capacitance sensor having specified directionality, said
capacitance sensor comprising: detection electrodes; an insulating
material insulating said detection electrodes from each other; a
main body containing said detection electrodes and said insulating
material and having a detection surface defined by said
directionality; and a water-repellant finish over at least a
portion of said main body including said detection surface.
2. The capacitance sensor of claim 1 further comprising: a shield
electrode inside said main body, said shield electrode being open
toward said detection surface, said detection electrodes being
disposed inside said shield electrode; and a protective cover
covering said shield electrode and said detection electrodes.
3. A capacitance sensor having specified directionality, said
capacitance sensor comprising: detection electrodes; an insulating
material insulating said detection electrodes from each other; and
a main body containing said detection electrodes and said
insulating material and having a detection surface defined by said
directionality, said detection surface having unevenness.
4. The capacitance sensor of claim 3 further comprising: a shield
electrode inside said main body, said shield electrode being open
toward said detection surface, said detection electrodes being
disposed inside said shield electrode; and a protective cover
covering said shield electrode and said detection electrodes.
5. A detector for detecting an object being caught by a door, said
detector comprising: detection electrodes; an insulating material
insulating said detection electrodes from each other; a main body
provided on an open end part of said door, said main body
containing said detection electrodes and said insulating material;
a sensor circuit which, together with said sensor main body, forms
a capacitance sensor having specified directionality; wherein said
sensor main body includes a detection surface defined by said
directionality and a water-repellant finish is provided over at
least a portion of said sensor main body including said detection
surface.
6. The detector of claim 5 further comprising: a shield electrode
inside said main body, said shield electrode being open toward said
detection surface, said detection electrodes being disposed inside
said shield electrode; and a protective cover covering said shield
electrode and said detection electrodes.
7. A detector for detecting an object being caught by a door, said
detector comprising: detection electrodes; an insulating material
insulating said detection electrodes from each other; a main body
provided on an open end part of said door, said main body
containing said detection electrodes and said insulating material;
and a sensor circuit which, together with said sensor main body,
forms a capacitance sensor having specified directionality; wherein
said sensor main body includes an uneven detection surface defined
by said directionality.
8. The detector of claim 7 further comprising: a shield electrode
inside said main body, said shield electrode being open toward said
detection surface, said detection electrodes being disposed inside
said shield electrode; and a protective cover covering said shield
electrode and said detection electrodes.
9. A detector for detecting an object being caught by a door, said
detector comprising: detection electrodes; an insulating material
insulating said detection electrodes from each other; a main body
provided on an open end part of said door, said main body
containing said detection electrodes and said insulating material;
a sensor circuit which, together with said sensor main body, forms
a capacitance sensor having specified directionality; and means for
grounding said door; wherein said sensor main body includes a
detection surface defined by said directionality and said detector
further comprised means for grounding said door.
10. The detector of claim 9 further comprising: a shield electrode
inside said main body, said shield electrode being open toward said
detection surface, said detection electrodes being disposed inside
said shield electrode; and a protective cover covering said shield
electrode and said detection electrodes.
11. A detector for detecting an object being caught by a door, said
detector comprising: detection electrodes; an insulating material
insulating said detection electrodes from each other; a main body
provided on an open end part of said door, said main body
containing said detection electrodes and said insulating material;
a sensor circuit which, together with said sensor main body, forms
a capacitance sensor having specified directionality; wherein said
sensor main body includes a detection surface defined by said
directionality, said detection surface being at a position farther
protruding from an open end part of said door.
12. The detector of claim 11 further comprising: a shield electrode
inside said main body, said shield electrode being open toward said
detection surface, said detection electrodes being disposed inside
said shield electrode; and a protective cover covering said shield
electrode and said detection electrodes.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a capacitance sensor (or
capacitive sensor) for detecting an object that may be caught or is
likely to be caught by a closing slide door, say, of a vehicle.
[0002] Controller systems for a structure adapted to open and close
such as an electrically powered slide door of a vehicle are
provided with a safety feature for preventing an object such as a
person's body from becoming caught thereby. In the case of an
automatically closing mechanism adapted to automatically bring the
structure (hereinafter referred to as the door) to the fully closed
position even after the user stops its operation, this may be done
by detecting an object that is caught or likely to be caught and at
least stopping the operation of the automatically closing
mechanism. The motion of the door may also be reversed.
[0003] Prior art detectors used for such a purpose were either for
direct detection or for indirect detection. Indirect detection may
be made on the basis of operation data of the driver motor such as
its angular position and its rotary speed or the driving power.
Direct detection may be made by means of a sensor for detecting a
human body approaching or coming into contact with an open end
portion of the door. Indirect detection has problems in that it is
relatively difficult to quickly and reliably detect a caught object
at a load as low as possible. Direct detection is superior from the
point of view of reliability because an object of detection is
directly detected but since a pressure-sensitive switch has been
used as a sensor of this type, detection could not be made quickly
at a low load. This was because a pressure-sensitive switch
comprised a cable, say, of a conductive resin material adapted to
function when deformed by a pressure from the target object such
that an internal conductive member comes into a contacting
position. In other words, the switch can function only after the
target object comes into contact with a pressure of a certain
magnitude and the function of preventing the object from being
caught begins to work only at such point in time.
[0004] A sensor for generally detecting an approaching target
object without contacting it may be of an optical type, an
electromagnetic wave type or a capacitance type. Sensors of the
optical type have the problem that the detection area cannot be
defined along a curved end portion of a structure such as a door,
that is, there result so-called insensitive zones. With a sensor of
the electromagnetic type, it is difficult to limit the
directionality to the direction of approach to the open end portion
of the door and there is a high probability of an erroneous
detection. Capacitance-type sensors seem to be superior because
they can be easily attached to a curved end part, there is no
insensitive part and the directionality can be easily controlled.
The present inventors have been examining how to use a capacitance
sensor as a detector for an object caught or being caught by a
powered slide door, say, of a vehicle.
[0005] No prior art example is known to have shown the use of a
capacitance sensor for detecting an object caught by a powered
slide door of a vehicle. Japanese Patent Publication Tokkai
10-96368 has disclosed a detector using a capacitance sensor for a
door of a railroad passenger car. Japanese Patent Publication
Tokkai 2001-264448 has disclosed the use of a capacitance sensor
for detecting a person caught by a shutter. Japanese Patent
Publication Tokkai 2001-318162 has disclosed a pin ball machine
sensor with a high sensitivity for detecting a passing pin ball by
providing a plurality of pairs of capacitance-providing electrodes
and on the basis of differentials of signals corresponding to each
capacitance.
[0006] According to the studies by the present inventors, however,
capacitance sensors as described above cannot be used for a
structure such as a door because of the problems of the kinds to be
described below if there are water drops such as rain drops.
[0007] (A) When the door is at a positive potential, the sensor is
likely to function incorrectly, becoming switched on if a body part
such as a hand of a person merely approaches the outer side surface
of the door while water drops such as rain drops are attached to
it.
[0008] (B) If water drops become attached to the detection surface
of a capacitance sensor over its entire width, the sensor is likely
to function incorrectly, becoming switched on because of these
water drops. In the case of a sensor with a sectionally U-shaped
shield electrode with an opening on the side of the detection
surface in order to provide directionality as much as possible only
on the side of the detection surface, for example, a detection
signal is likely to be incorrectly switched on if water drops
become attached so as to span between both its end positions.
[0009] (C) If water drops become attached continuously from the
door to a portion of the detection surface, an error is likely to
result although water drops may not be attached all over the
detecting surface.
[0010] It is therefore an object of this invention to provide a
capacitance sensor which is not likely to function incorrectly even
in an environment where water drops such as rain drops fly around,
as well as a reliable detector using such a sensor for detecting an
object being caught by a door.
SUMMARY OF THE INVENTION
[0011] A capacitance sensor embodying this invention may be
characterized simply as having an outer surface with a
water-repellant finish at least on the detection surface of its
main body, or somewhat more in detail as having specified
directionality and comprising detection electrodes, an insulating
material insulating the detection electrodes from each other, a
main body containing the detection electrodes and the insulating
material and having a detection surface (to be defined below), and
a water-repellant finish over at least a portion of the main body
including the detection surface.
[0012] The main body may further include a shield electrode inside,
open toward the detection surface and holding the detection
electrodes inside, as well as a protective cover covering both the
shield electrode and the detection electrodes. A shield electrode
thus structured serves to significantly increase the directionality
and reduce the possibility of erroneous detection, say, when the
object of detection approaches somewhere else away from the
specified detection area.
[0013] In the above, the "detection surface" is the portion of the
sensor surface with increased sensitivity in order to limit the
direction in which a target object is to be detected, or its
directionality. "Water-repellant finish" means forming a surface
with a water-repellant material or covering a surface with a
water-repellant material which may be in the form of a membrane or
a layer, and this may be formed by a simple process of pasting a
silicon tape on a surface. The "outer surface" means the surface of
the sensor main body or the portion of the sensor having detection
electrodes such as the surface of a protective cover over the
sensor main body. If possible, it is desirable to have the
water-repellant finish all over the outer surface inclusive of side
surfaces which are not the detection surface.
[0014] With a capacitance sensor thus structured, water drops do
not become attached easily to its outer surface inclusive of the
detection surface and, even if they become attached, they are
dispersed quickly and flow down easily due to the water-repellant
surface property. Since large or continuous water drops which cause
erroneous operations are not generated, the possibility of
incorrect functioning of the sensor at least of the types (B) and
(C) described above is significantly reduced.
[0015] A capacitance sensor according to another embodiment of the
invention may be characterized similarly except that its detection
surface is formed so as to have unevenness, that is, not being flat
but having indentations or protrusions, or both. Such surface
shapes make it harder for water drops to remain attached,
preventing them in particular to become connected continuously
across the entire width of the detection surface. It now goes
without saying that the characteristics of the sensors of the first
and second embodiments may be combined together to gain some
synergistic effects.
[0016] Detectors according to this invention are primarily for
detecting a target object which may be caught or is likely to be
caught by a closing slide door, say, of a vehicle. Such an object
may be feared as being about to or likely to be caught by the door
because it is approaching the door and is herein simply referred
to, for the simplicity of description, as an "object being caught"
by a door. Detectors of this invention may be generally
characterized as comprising a capacitance sensor of this invention
such as described above including a sensor circuit and having its
main body provided on an open end part of the door.
[0017] In the above, the open end part of the door is that portion
of the door which, when closed, comes into contact with the
opposite portion of the door frame. With a detector thus formed,
the possibility of erroneous detection can be reduced especially
since water drops are unlikely to form a continuous body of water
on the peripheral portions of the sensor main body.
[0018] It is preferable to have the door grounded such that its
voltage may be prevented from becoming positive and water drops can
be more dependably prevented from remaining attached. The problem
(A) described above can be more reliably obviated. The grounding
may be accomplished merely by connecting to a component of the
vehicle kept generally at the ground potential.
[0019] It is also preferable to arrange the sensor main body such
that its detection surface will be at a position farther protruding
from the open end part of the door to which the main body is
attached. This further has the effect of more dependably preventing
water drops from becoming connected continuously over the entire
distance between the door and the detection surface.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a schematic drawing of a detector embodying this
invention with a capacitance sensor and portions of a vehicle on
which the sensor is set.
[0021] FIG. 2A is a schematic drawing of the inner structure of the
capacitance sensor of FIG. 1 and FIG. 2B shows the sectional shape
and dimensions of its main body.
[0022] FIG. 3A is a schematic diagram of the sensor circuit and
FIG. 3B is a wave diagram for showing its operations.
[0023] FIGS. 4A, 4B and 4C are other sectional shapes of the sensor
main body according to this invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The invention is described next by way of an example, which
is a detector for detecting by means of a capacitance sensor a
person (regarded as its object of detection) who has approached a
position within a region close enough, say, to a four-wheeled
automobile (vehicle) and may be feared to be in danger of becoming
caught by its sliding door. FIG. 1 shows a detector embodying the
invention with a capacitance sensor, together with portions of the
vehicle on which this sensor is set. FIG. 2A shows the structure of
the sensor inside its main body 1, and FIG. 2B is its sectional
view, showing an example of its sectional shape and dimensions.
[0025] In FIG. 2A, the sensor main body 1 is shown with its
detection surface (defining the direction of its directionality)
facing upward. The other surfaces facing in other directions are
therefore considered to be "insensitive surfaces". The main body 1
contains within itself a shield electrode 5 and detection
electrodes 6a and 6b. The shield electrode 5 may be made of an
aluminum foil, being cross-sectionally U-shaped with the opening in
the direction of the detection surface (in the upward direction in
FIG. 2A). The detection electrodes 6a and 6b may be made of a
copper foil and disposed inside the shield electrode 5. An
insulating material 2 with a low dielectric constant such as foamed
styrene fills the space between the detection electrodes 6a and 6b
inside the shield electrode 5. Another insulating material 3 with a
low dielectric constant such as a heat shrinkable tube serves as a
protective cover, covering the whole in a protective manner.
[0026] The main body 1 thus structured may be made sufficiently
compact and flexible and hence can be bent in the longitudinal
direction. Thus, as shown in FIG. 1, this sensor main body 1 can be
conveniently set on a slide door (a rear door) 10 of a vehicle
along its open end portion. The main body 1 is so oriented that the
opening part of the shield electrode 5 is in the direction of the
position where a person is likely to be caught by the slide door 10
such that the sensor has accordingly a high sensitivity in this
direction and is basically insensitive in the other directions.
[0027] Although FIG. 2A shows the sensor main body 1 as having an
approximately rectangular outer cross-sectional shape but it was
merely for the convenience of illustration. In reality, it may be
shaped as shown in FIGS. 1 and 2A, protruding in the direction of
the detection surface. Such a shape with a protrusion may be
obtained by causing the insulating material 3 to protrude only in
the direction of the detection surface. The dimensions of the
exterior of the main body 1 may be as shown in FIG. 2B with a width
of about 15 mm and a thickness of about 20 mm.
[0028] FIG. 1 shows the sensor main body 1 attached to the open end
part of the slide door 10 by means of a bracket 11. When the door
10 is closed, as shown in FIG. 1, its open end part nearly contacts
a front door 13 with a small gap left therebetween, while
sandwiching a pillar 12 connected to the main body of the vehicle.
A hem part 14 is formed on the open end portion of the slide door
10, protruding toward the front door 13. As the slide door 10 is
closed, its hem part 14 extends forward inside the front door 13
and overlaps therewith to close the vehicle door.
[0029] The sensor main body 1 is disposed inside the hem part 14
towards the interior of the vehicle and is attached to the front
end of the bracket 11, say, by means of a adhesive so as to
protrude still farther forward towards the front door 13 than the
hem part 14, say, by a distance equal to or greater than 3 mm, as
shown in FIG. 1.
[0030] As shown symbolically by broken lines in FIG. 1, the
external surface of the sensor main body 1 and its neighboring
surface portions (including the whole or parts on the side of the
sensor main body 1) of the bracket 11 and the hem part 14 are
covered with a silicon tape or the like to provide a
water-repellant finish.
[0031] The slide door 10, the front door 13 and the pillar 12 are
all grounded and at ground potential. Since power needs to be
supplied to an actuator (not shown) for moving the slide door 10
into a retracted position after it is closed, such a slide door
used to remain at a positive potential according to prior art
technologies. According to the present invention, a grounding wire
(as schematically shown in FIG. 1) is provided for electrically
connecting the body of the slide door 13 with a grounding conductor
normally disposed below the door such that the slide door 10, too,
remains at ground potential.
[0032] FIG. 3A shows the structure of a circuit (sensor circuit)
connected to the sensor main body 1 for driving the sensor and
carrying out signal processing operations. As shown, the sensor
circuit is provided with pulse drive circuits 21A and 21B
respectively for the detection electrodes 6a and 6b, integrating
circuits 22A and 22B, a differential circuit 23 and a wave
detection circuit 24.
[0033] Pulse drive circuit 21A comprises a switch SW-A1 which is
driven by a driver circuit (not shown) to switch the connection to
the detection electrode 6a at a fast rate. The switch SW-A1 has a
common terminal, a ground terminal and a DPA terminal, the common
terminal being connected to the detection electrode 6a, the ground
terminal being connected to the grounding conductor of the vehicle,
and the DPA terminal being connected to the inversion input
terminal of an operational amplifier 25A (to be explained
below).
[0034] As shown in FIG. 3B, the switch SW-A1 is switched
periodically at a fast rate from one to another among the GND
condition wherein the common terminal is connected to the ground
terminal, the Open condition where the common terminal is not
connected to either of them, and the DPA condition wherein the
common terminal is connected to the DPA terminal. In FIG. 3A,
symbol Ca indicates the capacitance due to a body part such as a
hand of a person which is an object of detection and the detection
electrode 6a.
[0035] Pulse drive circuit 21B comprises a switch SW-B1 which is
similar to the switch SW-A1 and of which the common terminal is
connected to the detection electrode 6b, the ground terminal is
connected to the grounding terminal of the vehicle and the DPA
terminal is connected to the inversion input terminal of another
operational amplifier 25B (to be explained below). The switch SW-B1
also operates as shown in FIG. 3B. In FIG. 3A, symbol Cb indicates
the capacitance between the body part and the detection electrode
6b.
[0036] Integrating circuit 22A is provided with the operational
amplifier 25a, a switch SW-A2 forming a return circuit of the
operational amplifier 25a, a capacitor Cfa and a power source
circuit 26A for supplying a pulse voltage to the non-inversion
input terminal of the operational amplifier 25A.
[0037] In the above, the capacitor Cfa is connected between the
output terminal (OUTPUT A) and the inversion input terminal of the
operational amplifier 25A. The switch SW-A2 is connected in
parallel with the capacitor Cfa and serves to open and close the
connection between the two terminals of the capacitor Cfa (that is,
between the output and inversion input terminals of the operational
amplifier 25A). The switch SW-A2 is driven by a driver circuit (not
shown) and is switched from an ON-condition to an OFF-condition, as
shown in FIG. 3B, while the switch SW-A1 is in Open condition
before being switched to the DPA condition. The output (PULS) from
the power source circuit 26A changes periodically as shown in FIG.
3B, switching from the GND level to the charging voltage Vr as the
switch SW-A2 changes from the ON-condition to the OFF-condition and
switching from the charging voltage Vr to the GND level after the
switch SW-A1 changes from the DPA condition to the Open
condition.
[0038] Integrating circuit 22B is similar to integrating circuit
22A, being provided with the operational amplifier 25b, a switch
SW-B2 forming a return circuit of the operational amplifier 25b, a
capacitor Cfb and a power source circuit 26B for supplying a pulse
voltage to the non-inversion input terminal of the operational
amplifier 25B.
[0039] In the above, the capacitor Cfb is connected between the
output terminal (OUTPUT B) and the inversion input terminal of the
operational amplifier 25B. The switch SW-B2 is connected in
parallel with the capacitor Cfb and serves to open and close the
connection between the two terminals of the capacitor Cfb (that is,
between the output and inversion input terminals of the operational
amplifier 25B. The switch SW-B2 operates like the switch SW-A2, as
shown in FIG. 3B. The output from the power source circuit 26B
changes like that from the power source circuit 26A, as shown in
FIG. 3B.
[0040] The differential circuit 23 is for calculating and
outputting the difference between the outputs (OUTPUT A and OUTPUT
B) from the operational amplifiers 25A and 25B. The wave detection
circuit 24 is for outputting a signal voltage V1 on the basis of
the output VO from the differential circuit 23. If the output VO
from the differential circuit 23 changes as shown in FIG. 3B, the
high-voltage portion of this waveform, or the output voltage VO
when it has stabilized after the switches SW-A2 and SW-B2 are
switched off, is outputted as the signal voltage V1.
[0041] If a dielectric body such as a person's hand approaches the
detection surface of a capacitance sensor thus structured, the
signal voltage V1 changes in a sensitive manner. Thus, a highly
sensitive detection is possible by comparing this signal voltage
with a specified threshold value. Since this sensor is of a
differential type, making use of a differential between signals
based on two detection electrodes, furthermore, it is not likely to
be affected by factors such as noise and it is basically possible
to carry out a highly reliable detection. It is to be noted that
this capacitance sensor is not only of a differential type but also
of a charge transfer type, transferring electric charges between
capacitors Cfa and Cfb and capacitors Ca and Cb.
[0042] If a capacitance sensor as described above is used in a
detector for detecting an object caught (and/or likely to be
caught) by a door, the following advantages can be obtained.
[0043] (1) A detection area may be defined along a curved open end
part of a door of a vehicle to eliminate the insensitive zones, and
since the directionality of the detector can be limited to the
direction of approach to the open end part, the possibility of an
erroneous operation is small.
[0044] (2) Since a dielectric object such as a person's hand can be
detected in a non-contacting manner, an object which has been
caught or is likely to become caught can be detected at an early
stage and a preventive measure such as stopping the closing motion
of the door or opening the door by a specified distance) can be
carried out by hardly generating any load due to the impact.
[0045] (3) Since a capacitance sensor of a differential
charge-transfer type is used, a highly sensitive detection against
noise is possible.
[0046] (4) Water-repellant finish is provided not only on the
sensor main body but also on surfaces around it. Water drops are
not likely to remain attached to such surfaces and if they become
attached, they become dispersed by the repelling force and are
likely to flow down without forming large or continuous drops that
would tend to cause erroneous operations due at least to problems
of the types (B) and (C).
[0047] (5) Since the detecting surface of the sensor main body is
made uneven and not flat, it is difficult for water drops to remain
attached. The possibility of water drops becoming attached so as to
form a continuous band across the detecting surface is reliably
reduced.
[0048] (6) Since the slide door is grounded, the voltage of the
door is reliably prevented from becoming positive and errors due to
problems of the type (A) are prevented.
[0049] (7) Since the detection surface of the sensor main body is
at a position farther protruding forward than the tip of the hem
part of the door, the possibility of rain drops becoming connected
all the way across from the door to the detection surface is
extremely small. For this reason, too, errors due to problems of
the types (B) and (C) are unlikely.
[0050] The example described above is not intended to limit the
scope of the invention. Many modifications and variations are
possible within the scope of the invention. For example, the
detection surface of the sensor main body 1 need not be a simple
protrusion but may be of any other uneven shape having protrusions
and/or indentations as shown in FIGS. 4A, 4B and 4C. In summary,
the invention provides sensors unlikely to make errors even in an
environment with water drops such as rain drops splashing around
and reliable detectors using such a sensor for detecting an object
caught or likely to be caught by a door.
* * * * *