U.S. patent application number 14/944815 was filed with the patent office on 2020-08-13 for laser radar, and light receiving method of laser radar.
The applicant listed for this patent is KABUSHIKI KAISHA TOYOTA CHUO KENKYUSHO. Invention is credited to Kazuo HASEGAWA, Tadashi ICHIKAWA, Daisuke INOUE, Akari NAKAO, Tatsuya YAMASHITA.
Application Number | 20200256995 14/944815 |
Document ID | 20200256995 / US20200256995 |
Family ID | 1000004986774 |
Filed Date | 2020-08-13 |
Patent Application | download [pdf] |
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United States Patent
Application |
20200256995 |
Kind Code |
A1 |
INOUE; Daisuke ; et
al. |
August 13, 2020 |
LASER RADAR, AND LIGHT RECEIVING METHOD OF LASER RADAR
Abstract
A laser radar device includes: a light source; a projection
light scanner that scans one part of light split off from emission
light of the light source, and that generates transmission light
for radiating onto a target object; an image forming section that
forms plural respective reception lights of the transmission light
reflected by respective locations of the target object into an
image on a single flat plane as plural image-formation points; an
optical receiver that is disposed at the plural image-formation
points, and that includes plural unit optical reception sections
for mixing each of the plural reception lights together with a
reference light and performing optical heterodyne detection; and a
reference light scanner that scans or distributes another light
split off from the emission light from the light source, and that
generates the reference light for radiating onto each of plural of
the unit optical reception sections.
Inventors: |
INOUE; Daisuke;
(Nagakute-shi, JP) ; ICHIKAWA; Tadashi;
(Nagakute-shi, JP) ; YAMASHITA; Tatsuya;
(Nagakute-shi, JP) ; NAKAO; Akari; (Nagakute-shi,
JP) ; HASEGAWA; Kazuo; (Nagakute-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KABUSHIKI KAISHA TOYOTA CHUO KENKYUSHO |
Nagakute-shi |
|
JP |
|
|
Family ID: |
1000004986774 |
Appl. No.: |
14/944815 |
Filed: |
November 18, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01S 7/4911 20130101;
G01S 17/34 20200101; G01S 7/4917 20130101 |
International
Class: |
G01S 17/34 20060101
G01S017/34; G01S 7/4911 20060101 G01S007/4911; G01S 7/4912 20060101
G01S007/4912 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 19, 2014 |
JP |
2014-234987 |
Claims
1. A laser radar device comprising: a light source; a projection
light scanner that scans one part of light split off from emission
light of the light source, and that generates transmission light
for radiating onto a target object; an image forming section that
forms a plurality of respective reception lights, from the
transmission light reflected by respective locations of the target
object, into an image on a single flat plane as a plurality of
image-formation points; an optical receiver including a plurality
of unit optical reception sections that are disposed at the
plurality of image-formation points, and that mix each of the
plurality of reception lights together with a reference light and
perform optical heterodyne detection; and a reference light scanner
that scans or distributes another part of the light split off from
the emission light of the light source, and that generates the
reference light for radiating onto each of the plurality of unit
optical reception sections, wherein each unit optical reception
section includes an optical multiplexer configured to superimpose
one of the plurality of reception lights onto the reference
light.
2. The laser radar device of claim 1, wherein the reference light
scanner switches between guiding and not guiding the another part
of the light using a plurality of optical switches provided between
the light source and the plurality of unit optical reception
sections, and generates the reference light for radiating onto the
plurality of respective unit optical reception sections.
3. The laser radar device of claim 2, wherein each of the plurality
of respective optical switches is provided at a respective one of
the plurality of unit optical reception sections.
4. The laser radar device of claim 2, wherein the plurality of unit
optical reception sections are disposed in an array on the optical
receiver, and the plurality of optical switches are provided
respectively at each row or at each column of the array.
5. The laser radar device of claim 1, wherein the reference light
scanner includes a plurality of light emitters that emit respective
distribution lights optically distributed from the other light so
as to correspond to the plurality of respective unit optical
reception sections, and the reference light scanner distributes the
other light and generates the reference light for radiating onto
the respective plurality of unit optical reception sections.
6. The laser radar device of claim 1, wherein each of the plurality
of respective unit optical reception sections further includes an
optical incidence section to which the reception light is incident,
and an optical detection element, the optical multiplexer
multiplexes the reception light from the optical incidence section
and the reference light, and the optical detection element receives
the light multiplexed by the optical multiplexer.
7. The laser radar device of claim 1, wherein: the reference light
scanner comprises a variable phase shifter that shifts a phase of
the other light split off from the emission light, according to an
external signal, and a reference light generator comprising a
plurality of unit reference light generators that each include a
light emitter for emitting light that has been phase shifted by the
variable phase shifter; and the reference light scanner controls a
direction of a wave front of multiplexed emission light emitted
from the plurality of light emitters by controlling a phase shift
amount in each of the plurality of variable phase shifters, and
scans the emission light by switching which of the plurality of
unit optical reception sections the emission light is radiated
onto.
8. The laser radar device of claim 7, wherein a plurality of the
unit reference light generators are disposed in an array on the
reference light generator, and the plurality of variable phase
shifters phase shift each row or each column of the array by a
determined amount.
9. The laser radar device of claim 1, further comprising a detector
that detects at least one of amplitude or phase of reception light
for each of the plurality of optical receivers based on a signal
optical-heterodyne detected by the optical receiver.
10. The laser radar device of claim 1, comprising a plurality of
sets of the image forming section and the optical receiver.
11. The laser radar device of claim 1, wherein each of the
plurality of respective unit optical reception sections mixes the
plurality of respective reception lights with a corresponding
reference light and performs optical heterodyne detection.
12. The laser radar device of claim 1, wherein each of the
plurality of respective unit optical reception sections mixes the
reference light with reception lights from a specific number of the
plurality of reception lights, and performs optical heterodyne
detection.
13. An optical reception method for a laser radar device that
comprises: a light source; a projection light scanner that scans
one part of light split off from emission light of the light
source, and that generates transmission light for radiating onto a
target object; and a reference light scanner that scans another
part of the light split off from the emission light of the light
source, and that generates reference light for radiating onto each
of a plurality of unit optical reception sections, wherein each
unit optical reception section includes an optical multiplexer
configured to superimpose one of the plurality of reception lights
onto the reference light, the optical reception method comprising:
forming an image on a single flat plane as a plurality of
image-formation points, from a plurality of respective reception
lights that are the transmission light reflected by respective
locations of the target object; and mixing each of the plurality of
reception lights with the reference light by superimposing each of
the plurality of reception lights onto the reference light and
performing optical heterodyne detection using the plurality of unit
optical reception sections disposed at the plurality of
image-formation points.
14. The laser radar device of claim 1, further comprising a
modulator configured to modulate the one part of the light scanned
by the projection light scanner.
15. The optical reception method of claim 13, wherein the laser
radar device further comprises a modulator, and the method further
comprises modulating, using the modulator, the one part of the
light scanned by the projection light scanner.
16. The laser radar device of claim 1, further comprising an
optical waveguide that distributes the another part of the light
split off from the emission light of the light source to the
respective unit optical reception sections, wherein the reference
light scanner scans or distributes the another part of the light
via the optical waveguide.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is based on and claims priority under 35
USC 119 from Japanese Patent Application No. 2014-234987 filed on
Nov. 19, 2014, the disclosure of which is incorporated by reference
herein.
BACKGROUND
Technical Field
[0002] The present invention relates to a laser radar device and an
optical reception method for a laser radar device.
Related Art
[0003] A laser radar device is a type of remote sensing technology
that employs light, and is a device in which the distance to a
faraway target object, properties of the target object, and the
like are analyzed by radiating light from pulse-emitting light
projector onto the target object, and measuring scattered light
that has been reflected by the target object and received by an
optical receiver.
[0004] Examples of such laser radar devices include a device
described by Japanese Patent Application Laid-Open (JP-A) No.
2000-338243. The laser radar device described by JP-A No.
2000-338243 includes an optical modulator that modulates laser
light from a continuous wave (CW) laser, an optical antenna that
radiates the modulated laser light toward a target (subject) as
transmission light and receives scattered light from the target, a
mixing means that mixes laser light from the CW laser that has been
split by a splitting means as local light, together with light
received from the optical antenna, and an optical detector that
detects the mixed light by optical heterodyne detection.
[0005] JP-A No. 2001-272334 describes a system that performs
two-dimensional optical heterodyne scanning detection. The
two-dimensional optical heterodyne scanning detection system
described by JP-A No. 2001-272334 includes a pixel array of arrayed
photodiodes produced on a semiconductor substrate, a
two-dimensionally arrayed photo-detector in which MOS transistors
that sequentially read signal charges of the pixel array are pixel
arrayed, a scanning section that scans the two-dimensional
photo-detector, and a wave detecting circuit that processes an
output signal from the two-dimensional detection device.
[0006] When two two-dimensional light waves having optical
frequencies that differ by an amount f are incident to the
two-dimensional photo-detector, a two-dimensional light intensity
distribution that varies with time at a frequency f is produced on
the two-dimensional photo-detector based on a heterodyne beat
signal, and the amplitude of the intensity distribution is detected
by the wave detecting circuit.
[0007] In a laser radar device according to conventional technology
such as that described in JP-A No. 2000-338243, a device is
generally required for scanning projected light or reception light.
There is generally a scanning means such as a mirror or a prism,
particularly at the targeted reception side, which is particularly
objected to in the present invention. Issues related to reliability
are liable to arise in such cases, since the mirror or prism
includes movable components. Moreover, there is also an issue in
configurations using a mirror or prism in that optical defects may
arise, leading to a reduction in reception sensitivity.
[0008] The two-dimensional optical heterodyne scanning detection
system described by JP-A No. 2001-272334 is a device that detects a
spatial beat signal using a low coherence light source, and
addresses high-speed reading of electrical charges based on light
intensity of incident light arising in a two-dimensional
photo-detector. Thus this device does not directly contribute to
enhancing reception sensitivity that is one attribute demanded in a
laser radar device.
SUMMARY
[0009] In consideration of the above issues, an object of the
present invention is to implement a laser radar device with which
high sensitivity measurements are possible and that is highly
reliable, and to implement an optical reception method for a laser
radar device of the same.
[0010] In order to achieve the above object, a laser radar device
of a first aspect of the present invention includes: a light
source; a projection light scanner that scans one part of light
split off from emission light of the light source, and that
generates transmission light for radiating onto a target object; an
image forming section that forms plural respective reception lights
of the transmission light reflected by respective locations of the
target object into an image on a single flat plane as plural
image-formation points; an optical receiver that is disposed at the
plural image-formation points, and that includes plural unit
optical reception sections for mixing each of the plural reception
lights together with a reference light and performing optical
heterodyne detection; and a reference light scanner that scans or
distributes another light split off from the emission light of the
light source, and that generates the reference light for radiating
onto each of the plural unit optical reception sections.
[0011] A second aspect of the present invention is the first
aspect, wherein the reference light scanner switches between
guiding and not guiding the other light using plural optical
switches provided between the light source and the plural unit
optical reception sections, and that generates the reference light
for scanning and radiating onto the plural respective unit optical
reception sections.
[0012] A third aspect of the present invention is the second
aspect, wherein plural respective optical switches are each
provided to plural of the unit optical reception sections.
[0013] A fourth aspect of the present invention is the second
aspect, wherein the plural unit optical reception sections are
disposed in an array on the optical receiver, and the plural
optical switches are each provided to each row or to each column of
the array.
[0014] A fifth aspect of the present invention is the first aspect,
wherein the reference light scanner includes plural light emitters
that emit respective distribution lights distributed from the other
light so as to correspond to the plural respective unit optical
reception sections, and the reference light scanner distributes the
other light and generates the reference light for radiating onto
the plural respective unit optical reception sections.
[0015] A sixth aspect of the present invention is the first aspect,
wherein the plural respective unit optical reception sections are
configured including an optical incidence section to which the
reception light is incident, an optical multiplexer that
multiplexes the reception light from the optical incidence section
and the reference light, and an optical detection element that
receives the light multiplexed by the optical multiplexer.
[0016] A seventh aspect of the present invention is the first
aspect, wherein: the reference light scanner includes a variable
phase shifter that shifts the phase of the other light according to
an external signal, and a reference light generator including
plural unit reference light generators that include a light emitter
for emitting light that has been phase shifted by the variable
phase shifter; and the reference light scanner controls the
direction of a wave front of multiplexed emission light emitted
from the plural light emitters by controlling the phase shift
amount in each of the plural variable phase shifters, and scans the
emission light by switching which of the plural unit optical
reception sections the emission light is radiated onto.
[0017] An eighth aspect of the present invention is the seventh
aspect, wherein plural of the unit reference light generators are
disposed in an array on the reference light generator, and the
plural variable phase shifters phase shift each row or each column
of the array by a determined amount.
[0018] A ninth aspect of the present invention is the first aspect,
further including a detector that detects at least one out of
amplitude or phase of the reception light for each of the plural
optical receivers based on a signal optical-heterodyne detected by
the optical receiver.
[0019] A tenth aspect of the present invention is the first aspect,
further including plural sets of the image forming section and the
optical receiver.
[0020] An eleventh aspect of the present invention is the first
aspect, wherein each of the plural unit optical reception sections
mixes the plural respective reception lights with a corresponding
reference light and performs optical heterodyne detection.
[0021] A twelfth aspect of the present invention is the first
aspect, wherein each of the plural unit optical reception sections
mixes the reference light with reception lights from a specific
number of the plural reception lights, and performs optical
heterodyne detection.
[0022] In order to achieve the above object, in an optical
reception method for a laser radar device of a thirteenth aspect of
the present invention, the laser radar device method includes: a
light source; a projection light scanner that scans one part of
light split off from emission light of the light source, and that
generates transmission light for radiating onto a target object;
and a reference light scanner that scans another light split off
from the emission light from the light source, and that generates
the reference light for radiating onto each of the plural unit
optical reception sections, wherein the optical reception method
includes: forming an image on a single flat plane as plural
image-formation points, from plural respective reception lights
that are the transmission light reflected by respective locations
of the target object; and mixing each of the plural reception
lights with the reference light and performing optical heterodyne
detection using the plural unit optical reception sections disposed
at the plural image-formation points.
[0023] According to the present invention, an advantageous effect
is exhibited of high sensitivity measurement being possible when
implementing a highly reliable laser radar device and an optical
reception method of a laser radar device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a block diagram illustrating an example of a
configuration of a laser radar device according to an exemplary
embodiment.
[0025] FIG. 2 is a diagram illustrating an example of a
configuration of an optical receiver according to a first exemplary
embodiment.
[0026] FIG. 3 is a block diagram illustrating an example of a
configuration of a laser radar device according to the first
exemplary embodiment.
[0027] FIG. 4 is diagram illustrating an example of a configuration
of an image-forming optical receiver according to the first
exemplary embodiment.
[0028] FIG. 5 is a diagram illustrating an example of a
configuration of an optical receiver according to a second
exemplary embodiment.
[0029] FIG. 6 is a diagram illustrating an example of a
configuration of an optical receiver according to a third exemplary
embodiment.
[0030] FIGS. 7A to 7C are diagrams illustrating an example of a
configuration of a unit optical reception section according to the
third exemplary embodiment.
[0031] FIG. 8 is a block diagram illustrating an example of a
configuration of a laser radar device according to the third
exemplary embodiment.
[0032] FIGS. 9A to 9C are diagrams illustrating an example of a
configuration of a unit optical reception section according to a
fourth exemplary embodiment.
[0033] FIG. 10 is a block diagram illustrating an example of a
configuration of a laser radar device according to a fifth
exemplary embodiment.
[0034] FIG. 11 is a block diagram illustrating an example of a
configuration of a laser radar device according to a sixth
exemplary embodiment.
[0035] FIG. 12 is a diagram illustrating an example of a
configuration of a reference light generator according to the sixth
exemplary embodiment.
[0036] FIG. 13 is a diagram for explaining operation of a reference
light generator according to the sixth exemplary embodiment.
[0037] FIG. 14 is a block diagram illustrating an example of a
configuration of a laser radar device according to a seventh
exemplary embodiment.
[0038] FIGS. 15A and 15B are block diagrams illustrating examples
of configuration of a terminal device according to an eighth
exemplary embodiment.
DETAILED DESCRIPTION
[0039] Detailed explanation follows regarding an exemplary
embodiment the present invention, with reference to the drawings.
First, explanation follows regarding basic configuration of a laser
radar device 10 according to the present invention, with reference
to FIG. 1.
[0040] The laser radar device 10 includes a transmitter 100, a
receiver 200, a narrow linewidth light source 12, and an optical
splitter 220. The transmitter 100 is configured including a
reference light scanner 102, a modulator 106, and a projection
light scanner 104. The receiver 200 is configured including an
image-forming lens 204, an optical receiver 202, a pre-amplifier
206, and a signal processor 208.
[0041] As an example, the narrow linewidth light source 12 is a
laser that generates CW light, and is a light source that generates
a transmission light Pout radiating from the transmitter 100, and
generates a reference light Pref for optical heterodyne
detection.
[0042] The transmitter 100 generates the transmission light Pout
for radiating toward a target object O. The modulator 106 of the
transmitter 100 modulates one part of light split off from the
light output of the narrow linewidth light source 12 by the optical
splitter 220, and supplies the modulated light to the projection
light scanner 104. Modulation by the modulator 106 is modulation to
acquire the correlation between reception light Pin that is
reflected (scattered) by the target object O and incident to the
receiver 200, and the transmission light Pout, and employs, for
example, modulation using a pseudorandom number pattern (PN
pattern), modulation using a sine wave, or the like. The projection
light scanner 104 of the transmitter 100 scans such that the light
modulated by the modulator 106 is radiated toward the target object
O.
[0043] The receiver 200 receives, as the reception light Pin, light
that is emitted from the transmitter 100 as transmission light Pout
and then reflected (scattered) by the target object O. The
image-forming lens 204 of the receiver 200 forms an image of the
target object O on the optical receiver 202 using the reception
light Pin. The optical receiver 202 is an optical reception element
provided with plural arrayed unit optical reception sections 210
that each include a photodiode 212 (see FIG. 2 etc.), and an image
of the target object O is formed on the surface of the optical
reception elements such that the optical reception elements
correspond to respective portions of the target object O. To
reflect this meaning, optical reception faces of each of the unit
optical reception sections 210 (photodiodes 212) are sometimes
referred to as "image-forming points", and the optical reception
element surface configured by the unit optical reception sections
210 is sometimes referred to as a "focal plane array".
[0044] In the laser radar device 10, reference light Pref that is
switching controlled by the reference light scanner 102 is incident
to each of the unit optical reception sections 210 (the photodiodes
212), together with reception light Pin corresponding to respective
portions of the target object O. The reference light scanner 102 of
the laser radar device 10 controls by switching whether or not the
reference light Pref is caused to be incident to each of the plural
unit optical reception sections 210. Namely, in the laser radar
device 10 of the present exemplary embodiment, reception light Pin
corresponding to respective portions of the target object O is
formed as an image on the focal plane array without scanning the
reception light Pin, and the reference light Pref is caused to be
incident to each image forming point while being switched (while
being scanned).
[0045] In the laser radar device 10, intermediate frequencies are
produced by interference between the reception light Pin and the
reference light Pref and optical heterodyne detection is performed
in each of the unit optical reception sections 210 (namely, on the
focal plane array). Namely, a beat signal of the reception light
Pin and the reference light Pref is output from each of the unit
optical reception sections 210 as an electrical signal. The
electrical signals output from the optical receiver 202 are sent to
the signal processor 208 through pre-amplifiers 206. In the signal
processor 208, specific arithmetic processing is performed on the
beat signal, and at least one out of amplitude or phase of the
reception light Pin corresponding to respective portions of the
target object O is detected. The distance to the target object O,
the travelling speed of the target object O, or the like, is
calculated from information indicating at least one out of the
detected amplitude or phase of the reception light Pin.
[0046] In this manner, in the laser radar device 10 according to
the present invention, configuration is made such that the
reception light Pin is input to the optical receiver 202 as
directly as possible (without passing through a scanner or the
like). Thus, in the laser radar device 10, the reception light Pin
reflected by the respective portions of the target object O is
formed as an image by the optical receiver 202 as a focal plane
array, and the reference light Pref is scanned so as to be caused
to be incident to each image-formation point. While the light
intensity of the reception light Pin is generally weak, the light
intensity of the reference light Pref can be amplified if
necessary; and the light intensity of the reference light Pref may
be made so as to always be constant. This enables high sensitivity
measurements in the laser radar device 10 according to the present
invention.
[0047] Although explanation follows regarding an example of a mode
in which the reference light scanner 102 in the laser radar device
10 is switching controlled (scanned) such that the reference light
Pref is sequentially incident to each of the unit optical reception
sections 210 (for example, so as to be incident to each row in
turn), there is no limitation thereto, and the switching control
may be performed such that the reference light Pref is incident in
whichever sequence. Moreover, it is not particularly necessary for
switching control to be performed such that the reference light
Pref is incident to one unit optical reception section 210 each
time, and switching control may be performed such that the
reference light Pref is incident to plural individual unit optical
reception sections 210 each time.
[0048] Moreover, although explanation is given in the exemplary
embodiments regarding examples of a mode in which optical
heterodyne detection is performed in a receiver with signals of
reception light Pin and reference light Pref that differ from each
other in terms of properties of modulation or the like, there is no
limitation thereto, and a mode may be employed in which homodyne
detection is performed with signals of reception light Pin and
reference light Pref having the same properties as each other.
First Exemplary Embodiment
[0049] Explanation follows regarding a laser radar device 10a
according to an exemplary embodiment, with reference to FIG. 2 to
FIG. 4.
[0050] First, explanation follows regarding an optical receiver
202a according to the present exemplary embodiment, with reference
to FIG. 2. As illustrated in (1) of FIG. 2, the optical receiver
202a includes plural of the unit optical reception sections 210
disposed in an array. The number of the unit optical reception
sections 210 that configure the optical receiver 202a is, as an
example, 50.times.50=2500 units. However, only 3.times.4=12 units
thereof are illustrated in (1) of FIG. 2.
[0051] As illustrated in (1) of FIG. 2, the reference light Pref
incident from one end of an optical waveguide 222 is switching
controlled between guiding and not guiding by an optical switch 216
illustrated in (2) of FIG. 2, and is distributed to the respective
unit optical reception sections 210. Reception light Pin
corresponding to each portion of the target object O is incident to
the photodiode 212 of each respective unit optical reception
section 210. The configuration of the optical switch 216 employed
by the optical receiver 202a according to the present exemplary
embodiment is not particularly limited, and any optical switch,
such as a thermo optical switch or a mechanical optical switch, may
be employed.
[0052] As illustrated in (1) of FIG. 2, in the present exemplary
embodiment, each of the unit optical reception sections 210 is
provided with an optical switch 216, and the optical switches 216
switching control whether or not the reference light Pref is caused
to be incident to each of the photodiodes 212 in the unit optical
reception sections 210. Namely, in the present exemplary
embodiment, the plural optical switches 216 configure the reference
light scanner 102 illustrated in FIG. 1.
[0053] Next, detailed explanation follows regarding the unit
optical reception section 210, with reference to (3) of FIG. 2. The
unit optical reception section 210 according to the present
exemplary embodiment includes the photodiode 212, a grating coupler
214, the optical switch 216, and an optical multiplexer 218.
[0054] The grating coupler 214 is configured by using periodic
refractive index modulation (an optical waveguide grating) provided
on the optical waveguide surface to efficiently incorporate the
reception light Pin into the optical waveguide 222. The grating
coupler 214 may also be employed in reverse in cases in which light
is caused to efficiently emanate from the optical waveguide 222
(see FIG. 12).
[0055] The photodiode 212 receives the reception light Pin
corresponding to respective portions of the target object O and the
reference light Pref that have been multiplexed by the optical
multiplexer 218, superimposes the two, and outputs an optical
heterodyne detected electrical signal.
[0056] The optical switch 216 switches as to whether or not the
reference light Pref is caused to be incident to the photodiode
212.
[0057] Next, explanation follows regarding the laser radar device
10a according to the present exemplary embodiment, with reference
to FIG. 3. The laser radar device 10a includes the narrow linewidth
light source 12, the transmitter 100, and a receiver 200a. The
narrow linewidth light source 12 and the transmitter 100 are
similar to those illustrated in FIG. 1.
[0058] The receiver 200a according to the present exemplary
embodiment is configured including three systems of the
image-formation optical receivers 224 each including a combination
of the same optical receiver 202a and the same image-forming lens
204. In the drawing, A, B, and C represent respective portions of
the target object O (labelled "real space" in FIG. 3), and light
reflected by the respective portions A, B, C are incident as the
reception light Pin to respective image-formation optical receivers
224-1, 224-2, 224-3.
[0059] The configuration of the three image-formation optical
receiver 224 systems configured by the receivers 200a is adopted in
order to allow the light intensity of reception light Pin to be
increased, and more preferably image-formation optical receivers
224 are laid out in an array may be employed by using a microlens
array as the image-forming lens 204. The number of image-formation
optical receiver 224 arrays is not limited to three systems; the
number may be set appropriately, and may, for example, be
approximately 7.times.7. Obviously, a mode employing a single
image-formation optical receiver 224 (for example, see FIG. 8) may
be adopted when the light intensity of reception light Pin is not
an issue.
[0060] FIG. 4 illustrates a configuration of one of the
image-formation optical receivers 224. The optical receiver 202a of
the image-formation optical receiver 224 is illustrated in FIG. 2,
and switching as to whether or not the reference light Pref is
caused to be incident to each unit optical reception section 210 is
performed by the optical switch 216.
[0061] With reference to FIG. 3 again, the received electrical
signals that were output from the three image-formation optical
receivers 224 are input to the three signal processors 208 of the
respective unit optical reception sections 210 (labelled "A group",
"B group", and "C group" in FIG. 3) after combination in the
respective unit optical reception sections 210.
[0062] The processing by the signal processor 208 may be processing
by a separate reception circuit 240 for each of the image-formation
optical receivers 224 (labelled "Type I" in FIG. 3), or may be
processing by a single reception circuit 240a on the collective
outputs of the image-formation optical receivers 224 (labelled
"Type II" in FIG. 3).
[0063] As described above, the laser radar device 10a according to
the present exemplary embodiment scans the reference light Pref for
mixing with the reception light Pin to perform optical heterodyne
detection, such that high sensitivity measurement is possible, and
such that a laser radar device having high reliability can be
implemented.
Second Exemplary Embodiment
[0064] Explanation follows regarding the laser radar device 10
according to the present exemplary embodiment, with reference to
FIG. 5. The present exemplary embodiment is a mode that employs an
optical receiver 202b as the optical receiver 202 of the laser
radar device 10 illustrated in FIG. 1.
[0065] As illustrated in FIG. 5, the optical receiver 202b employs
optical receivers 210a that are obtained by removing the optical
switch 216 from the unit optical reception section 210 in place of
the unit optical reception sections 210 of the optical receiver
202a illustrated in (1) of FIG. 2.
[0066] The optical receiver 202a illustrated in (1) of FIG. 2 is a
mode that switches as to whether or not the reference light Pref is
caused to be incident to each of the photodiodes 212; however, in
the optical receiver 202b a mode is adopted in which the optical
switches 216, disposed at a left end, switch as to whether or not
the reference light Pref is caused to be incident to each of the
arrayed photodiodes 212. Namely, the optical switches 216 disposed
at the left end of the optical receiver 202b in the present
exemplary embodiment configure the reference light scanner 102
illustrated in FIG. 1. Note that although explanation is given
regarding an example in which switching is performed in row units
of the arrayed photodiodes 212 in the present exemplary embodiment,
there is no limitation thereto, and switching may be performed in
column units.
[0067] In the optical receiver 202b according to the present
exemplary embodiment, it is necessary to separate the signals of
photodiodes 212 that are in the same row using electrical circuits
subsequent to the pre-amplifier 206; however, the number of the
optical switches 216 can be reduced.
Third Exemplary Embodiment
[0068] Explanation follows regarding a laser radar device 10b
according to an exemplary embodiment, with reference to FIG. 6 to
FIG. 8. The present exemplary embodiment is a mode that employs an
optical receiver 202c as the optical receiver 202, by employing a
receiver 200b as the receiver 200 of the laser radar device 10
illustrated in FIG. 1.
[0069] As illustrated in (1) of FIG. 6, in place of the unit
optical reception sections 210a of the optical receiver 202b
illustrated in FIG. 5, the optical receiver 202c employs unit
optical reception sections 210b that each integrate together a
photodiode (PD) and a transimpedance amplifier (TIA) serving as a
pre-amplifier. Configuration in which whether or not the reference
light Pref is caused to be incident to the photodiodes PD is
implemented by switching, using the optical switches 216 disposed
at the left end of the optical receiver 202c in row units of the
unit optical reception section 210b laid out in an array, is
similar to that of the optical receiver 202b illustrated in FIG.
5.
[0070] Explanation follows regarding a specific configuration of
the unit optical reception section 210b, with reference to FIG. 7A
to FIG. 7C. As illustrated in FIG. 7A, each of the unit optical
reception sections 210b includes a photodiode 250 and a TIA 252
that have been monolithically integrated together. The photodiode
250 is a photodiode that employs germanium (Ge) as a material, and,
as illustrated in FIG. 7A, reception light Pin is caused to be
incident thereto through a rear face (the substrate side). As
illustrated in FIG. 7B, the reference light Pref is guided through
the optical waveguide 222, and, after being split by the optical
splitter 220, is caused to be incident from a front face of the
photodiode 250, through a grating coupler 254 disposed at a leading
end portion of the optical waveguide 222. The reception light Pin
and the reference light Pref are mixed together by a photoelectric
converter of the photodiode 250, and optical heterodyne detection
is performed.
[0071] Explanation follows regarding an example of a specific
configuration of each of the unit optical reception sections 210b,
with reference to FIG. 7C. The photodiode 250 is formed on a
substrate 274 of silicon (Si), and is configured including a P-Si
region 262, a P+Si region 260, a Ge layer 258, and an N-type Ge
layer 256. Herein, the P-Si region represents a region of Si doped
with a low concentration of P-type impurities, and the P+Si region
represents a region of Si doped with a high concentration of P-type
impurities.
[0072] The TIA 252 is configured including an N-Si region 266
formed on the Si substrate 274, a P-Si region 270 and an N+Si
region 264 formed within the N-Si region 266, and a P+Si region 268
and an N+Si region 272 formed within the P-Si region 270.
[0073] An SiO.sub.2 layer 276 is formed to an upper portion of the
photodiode 250 and the TIA 252, and the optical waveguide 222 and
the grating coupler 254 are formed within the SiO.sub.2 layer 276.
The photodiode 250 and the TIA 252 are each connected to, for
example, an electrode 278 formed from aluminum (Al) or the
like.
[0074] FIG. 8 illustrates the laser radar device 10b that employs a
receiver 200b (the optical receiver 202c). The optical receiver
202c illustrated in FIG. 8 is a cross-section of the optical
receiver 202c illustrated in (1) of FIG. 6, as viewed along the
direction of the white arrow S illustrated in (1) of FIG. 6, and
four units of the unit optical reception section 210b are disposed
along a direction facing into the page. The optical switches 216
switch whether or not the reference light Pref is caused to be
incident to the photodiode 250 for each of the four units.
[0075] The reception light Pin corresponding to the each portion of
the target object O is guided by the image-forming lens 204, and is
incident to the respective photodiode 250 of the unit optical
reception section 210b. The reception light Pin and the reference
light Pref are mixed together according to the switching control by
the optical switch 216, and optical heterodyne detection is
performed.
[0076] The present exemplary embodiment employs the photodiode 250
that uses Ge, and is therefore a mode particularly applicable to,
for example, cases in which a laser in a long wavelength region
(for example, 1.55 .mu.m) is employed in the narrow linewidth light
source 12 (for the transmission light Pout and the reference light
Pref).
Fourth Exemplary Embodiment
[0077] Explanation follows regarding the laser radar device 10
according to an exemplary embodiment, with reference to FIG. 9A to
FIG. 9C. The present exemplary embodiment is a mode in which the
unit optical reception section 210b of the optical receiver 202c of
the laser radar device 10b illustrated in FIG. 8 is replaced by a
unit optical reception section 210c. Configuration other than that
of the unit optical reception section 210c is similar to that of
FIG. 8, and explanation therefore is omitted. Explanation follows
here regarding the configuration of the unit optical reception
section 210c.
[0078] As illustrated in FIG. 9A, the unit optical reception
section 210c is obtained by replacing the photodiode 250 of the
unit optical reception section 210b illustrated in FIG. 7A to FIG.
7C with a photodiode 250a. The TIA 252 is configured similarly to
the TIA illustrated in FIG. 7.
[0079] FIG. 9C illustrates an example of a specific configuration
of the unit optical reception section 210c. The photodiode 250a of
the unit optical reception section 210c is configured including an
N-Si region 282 formed on an Si substrate 286, and an N+Si region
280 and a P+Si region 284 formed within the N-Si region 282.
[0080] An SiO.sub.2 layer 288 is formed on the photodiode 250a and
the TIA 252. The optical waveguide 222 is formed within the
SiO.sub.2 layer 288, and the grating coupler 254 is formed at a
leading end portion of the optical waveguide 222. Moreover, for
example, the electrode 278 that is formed from aluminum (Al) or the
like is connected to each of the photodiode 250a and the TIA
252.
[0081] The reference light Pref is caused to be incident to the
photodiode 250a through the optical waveguide 222 and the grating
coupler 254. The reception light Pin here differs from that of the
unit optical reception section 210b illustrated in FIG. 7 in that
the reception light Pin here is caused to be incident from the
front face of the photodiode 250a.
[0082] The present exemplary embodiment employs a photodiode 250a
using Si, and is therefore a mode particularly well suited to cases
in which a laser in the visible spectrum is employed in the narrow
linewidth light source 12 (for the transmission light Pout and the
reference light Pref).
Fifth Exemplary Embodiment
[0083] Explanation follows regarding a laser radar device 10c
according to an exemplary embodiment, with reference to FIG. 10.
The present exemplary embodiment is a mode in which the
image-forming lens 204 of the laser radar device 10b illustrated in
FIG. 8 is replaced by a wide-angle lens 204a and an image-forming
lens 204b. The optical receiver 202c is similar to that illustrated
in FIG. 8, and explanation thereof is therefore omitted.
[0084] In the present exemplary embodiment, the wide-angle lens
204a is employed as part of the image-forming lenses. As
illustrated in FIG. 8, there are limitations to the visible angle
(image angle) in cases in which a single image-forming lens 204 is
employed, and the reception light Pin sometimes cannot be
adequately captured from a wide region target object O. The present
exemplary embodiment has an increased visible angle due to the
wide-angle lens 204a, and is therefore a mode effective for
capturing reflected light even from wide region target objects
O.
Sixth Exemplary Embodiment
[0085] Explanation follows regarding a laser radar device 10d
according to an exemplary embodiment, with reference to FIG. 11 to
FIG. 13. As illustrated in FIG. 11, the present exemplary
embodiment is a mode that employs a reference light generator 290
as the reference light scanner 102 illustrated in FIG. 1, and
employs a receiver 200d as the receiver 200.
[0086] Explanation follows regarding an example of a configuration
of the reference light generator 290 according to the present
exemplary embodiment, with reference to FIG. 12. As illustrated in
(1) of FIG. 12, the reference light generator 290 is configured
including plural (3.times.4=12 units in the example illustrated in
FIG. 12) of a unit reference light generator 230. The reference
light Pref from the narrow linewidth light source 12, which has
been split by the optical splitter 220 illustrated in (2) of FIG.
12, is then distributed by the optical waveguide 222 and guided to
each of the unit reference light generators 230. Note that there is
no limitation to 12 units as the number of unit reference light
generators 230 disposed in the reference light generator 290, and
an appropriate number thereof may be disposed according to, for
example, the light intensity required for the reference light
Pref.
[0087] As illustrated in (3) of FIG. 12, each of the unit reference
light generators 230 includes a grating coupler 214 and an optical
phase shifter 234. The optical phase shifter 234 is provided for
changing the phase of the reference light Pref, and, in the present
exemplary embodiment, is configured so as to be capable of changing
the phase of the reference light Pref incident to each unit
reference light generator 230. The grating coupler 214 causes the
reference light Pref, which has been phase-adjusted using the
optical phase shifter 234, to emanate toward an optical receiver
202d.
[0088] Explanation follows regarding operation principles of the
reference light generator 290 according to the present exemplary
embodiment, with reference to FIG. 13. As illustrated in FIG. 13,
in the reference light generator 290 according to the present
exemplary embodiment, the phase of the unit reference light
generators 230 is changed column-by-column. Namely, in the example
illustrated in FIG. 13, the phase of the unit reference light
generators 230-1 for the unit reference light generators 230
present in the same column as each other is adjusted to
.DELTA..phi.=0.degree.. Similarly, the phase is adjusted to
.DELTA..phi.=10.degree. for unit reference light generators 230-2
of unit reference light generators 230 present in the same column
as each other, the phase is adjusted to .DELTA..phi.=20.degree. for
unit reference light generators 230-3 of unit reference light
generators 230 present in the same column as each other, and the
phase is adjusted to .DELTA..phi.=30.degree. for unit reference
light generators 230-4 of unit reference light generators 230
present in the same column as each other.
[0089] In the reference light generators 290 that have been phase
adjusted in this manner, as illustrated in FIG. 13, reference light
Pref1, reference light Pref2, reference light Pref3, and reference
light Pref4 respectively emitted from the column 230-1, the column
230-2, the column 230-3, and the column 230-4 of the unit reference
light generators propagate with time offsets to each other. Wave
fronts formed by the reference light Pref1, the reference light
Pref2, the reference light Pref3, and the reference light Pref4 of
such time offset propagate out as WP1, WP3, WP3, and so on.
[0090] It is possible to freely adjust the direction X in which the
wave fronts WP propagate by adjusting the phase .DELTA..phi. of
each of the unit reference light generators 230. Accordingly,
adjusting the phase .DELTA..phi. of each of the unit reference
light generators 230 to control the emission direction X of the
reference light Pref, scans the position of the reference light
Pref on the surface of the optical receiver 202d, and enables the
reference light Pref to be mixed with the reception light Pin
corresponding to respective portions of the target object O.
[0091] In the laser radar device 10d according to the present
exemplary embodiment, there is no need to scan the reference light
Pref in the optical receiver 202d since the reference light Pref is
scanned in the reference light generator 290. Thus, in contrast to
each of the exemplary embodiments above, there is no need to
dispose optical switches in the optical receiver 202d, and the
optical receiver 202d is fundamentally configured by photodiodes
212 (or, alternatively, by using the unit optical reception section
210b or the unit optical reception section 210c). This thereby
enables the optical receiver 202 to be more simply configured.
[0092] Note that there is a low number of the unit optical
reception sections 210 included in the optical receiver 202, and in
cases in which, for example, the arithmetic processing load in the
signal processor 208 is low, there is not always a need to scan the
reference light Pref using switching control. There is no need to
provide the optical phase shifter 234 in such cases, and it is
sufficient for the reference light Pref distributed by the optical
waveguide 222 to be emitted from the grating coupler 214 and
emanate toward the corresponding unit optical reception section
210.
Seventh Exemplary Embodiment
[0093] Explanation follows regarding a laser radar device 10e
according to an exemplary embodiment, with reference to FIG. 14.
The laser radar device 10e is obtained by replacing the optical
receiver 202d with an optical receiver 202e, by replacing the
receiver 200d of the laser radar device 10d illustrated in FIG. 11
with a receiver 200e. The scanning of the reference light Pref is
accordingly performed by the reference light generator 290.
[0094] The optical receiver 202e is configured by plural arrays of
unit optical reception sections 210e. This differs from the optical
receiver 202d in that plural reception lights Pin from among the
reception lights Pin corresponding to respective portions of the
target object O are input to a single photodiode of each of the
unit optical reception sections 210e.
[0095] In the optical receiver 202e according to the present
exemplary embodiment, plural input signals incident to the
photodiodes of the unit optical reception section 210e need to be
separated using an electrical circuit subsequent to the
pre-amplifier 206; however, the number of the unit optical
reception sections 210e can be reduced.
[0096] Note that configuration in which plural reception lights Pin
from among the reception lights Pin corresponding to respective
portions of the target object O are input to a single photodiode of
the unit optical reception sections 210 is not limited to
application to the present exemplary embodiment, and such a
configuration may be applied to each of the above exemplary
embodiments.
Eighth Exemplary Embodiment
[0097] Explanation follows regarding a terminal device according to
an exemplary embodiment, with reference to FIG. 15A and FIG. 15B.
The present exemplary embodiment is a mode in which a laser radar
device according to one of the above exemplary embodiments is
applied to a tablet terminal device and a wearable terminal device
that serve as examples of a terminal device.
[0098] The laser radar device according to the above exemplary
embodiments is capable of measuring with high sensitivity the
distance to a target object, the properties of the target object,
and the like, and is capable of vibration mapping, namely,
visualization of vibrations, by applying such high sensitivity
measurement characteristics. The present exemplary embodiment is a
mode in which the laser radar device according to the present
invention is applied to a terminal device for visualizing
vibrations in this manner.
[0099] FIG. 15A illustrates a tablet terminal device 500 according
to the present exemplary embodiment. As illustrated in FIG. 15A,
the tablet terminal device 500 includes a sensor 502, a
microprocessor 504, a touch sensor 506, a display section 508, and
an audio playback/recording section 510.
[0100] The sensor 502 is configured by a laser radar device
according to each of the above exemplary embodiments, and is, for
example, a sensor that detects sounds up to 20 kHz, namely, sounds
perceptible to the human ear. The touch sensor 506 and the display
section 508 configure a so-called touch panel. The audio
playback/recording section 510 records and plays back detected
sound. The sensor 502, the touch sensor 506, the display section
508, and the audio playback/recording section 510 are each
connected to the microprocessor 504.
[0101] In the tablet terminal device 500 according to the present
exemplary embodiment configured as described above, sound of a
touched position of the display section 508 can be detected with
high sensitivity, and the detected sound can be recorded and played
back.
[0102] FIG. 15B illustrates a wearable terminal device 550
according to the present exemplary embodiment. As illustrated in
FIG. 15B, the wearable terminal device 550 includes a sensor 552, a
microprocessor 554, and an audio playback/overlap display section
556. The wearable terminal device 550 is, for example, configured
as a spectacles-type wearable terminal device.
[0103] The sensor 552 is configured by a laser radar device
according to the above exemplary embodiments, and is a sensor that
detects sound, particularly sound that is imperceptible to the
human ear. The audio playback/overlap display section 556
visualizes the detected sound, and displays the visualization
together with an image of the target object on a display section
provided to the wearable terminal device (not illustrated in the
drawings). The sensor 552 and the audio playback/overlap display
section 556 are each connected to the microprocessor 554.
[0104] The wearable terminal device 550 according to the present
exemplary embodiment, is, for example, worn by an operator in a
factory, and is a particularly effective terminal device in, for
example, cases in which abnormal sound inaudible to the operator is
detected.
[0105] Here, each of the above exemplary embodiments make no
particular reference to the mode by which the unit optical
reception section 210 or the unit reference light generator 230 is
integrated. The configurations of these sections may be achieved by
integrating together individual respective optical components, and
the optical waveguide-type optical receiver 202 or the reference
light generator 290 may be integrated by integrating the respective
optical components together using optical waveguide technology.
[0106] Namely, for example, taking the optical receiver 202a (FIG.
2) as an example, the optical receiver 202a may be configured by
combining the individual components of the photodiode 212, the
grating coupler 214, the optical switch 216, and the optical
multiplexer 218; or the photodiode 212, the grating coupler 214,
the optical switch 216, and the optical multiplexer 218 may be
configured as an optical waveguide-type optical receiver 202a that
has been fabricated using optical waveguide technology.
[0107] The respective configurations of the laser radar devices
according to each of the above exemplary embodiments are not
limited to only these laser radar devices, and appropriate
combinations may be made thereof. For example, although an example
is given in which the optical receiver 202c illustrated in FIG. 6
is configured to switch the reference light Pref between guiding
and not guiding for each row unit of the arrayed unit optical
reception sections 210b, the optical switches 216 may be
respectively provided for each of the unit optical reception
sections 210b, and the optical receiver 202c may be configured to
switch whether or not the reference light Pref is caused to be
incident to each of the unit optical reception sections 210b
similarly to as in the optical receiver 202a illustrated in FIG.
2.
[0108] Moreover, in the above exemplary embodiments, as an example
of integration of the transmitter 100 and the optical receiver 200
according to the present exemplary embodiment, explanation has been
given regarding an example of a mode in which the reference light
Pref supply section (the optical waveguide 222 and the grating
coupler 254) of the reference light scanner 102 and the unit
optical reception section 210 are integrated (see FIG. 7, FIG. 9).
However, there is no limitation thereto, and various other modes of
integration may be applied. For example, a mode may be employed in
which integration is achieved by subdividing and integrating into
an integrated circuit corresponding to the transmitter 100 and an
integrated circuit corresponding to the receiver 200, illustrated
in FIG. 1. Namely, a mode may be employed in which the whole of the
reference light scanner 102 is integrated by inclusion in the
transmitter 100, and the optical receiver 202, the pre-amplifier
206, and the signal processor 208 are integrated by inclusion in
the receiver 200. As the mode of mixing the reception light Pin
with the reference light Pref in such cases, for example, a mode
may be employed in which the reference light Pref distributed by
the optical waveguide 222 of the reference light generator 290
illustrated in FIG. 12 is emitted from the grating coupler 214
without passing through the optical phase shifter 234, and emanates
toward the corresponding unit optical reception section 210.
* * * * *