U.S. patent application number 15/410902 was filed with the patent office on 2017-05-11 for object information acquiring apparatus and laser apparatus.
The applicant listed for this patent is CANON KABUSHIKI KAISHA. Invention is credited to Koichi Suzuki.
Application Number | 20170127949 15/410902 |
Document ID | / |
Family ID | 50943119 |
Filed Date | 2017-05-11 |
United States Patent
Application |
20170127949 |
Kind Code |
A1 |
Suzuki; Koichi |
May 11, 2017 |
OBJECT INFORMATION ACQUIRING APPARATUS AND LASER APPARATUS
Abstract
An object information acquiring apparatus is used which
includes: a laser medium; a temperature controlling unit for
controlling a temperature of the laser medium; an excitation unit
for exciting the laser medium; a control unit for controlling the
temperature controlling unit and the excitation unit; a probe for
receiving acoustic waves that are generated when an object is
irradiated with a laser beam from the laser medium; and a
processing unit for acquiring characteristic information relating
to the object from the acoustic waves, wherein the control unit
does not operate the excitation unit until the temperature of the
laser medium falls within a predetermined range.
Inventors: |
Suzuki; Koichi;
(Kodaira-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CANON KABUSHIKI KAISHA |
Tokyo |
|
JP |
|
|
Family ID: |
50943119 |
Appl. No.: |
15/410902 |
Filed: |
January 20, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
14306390 |
Jun 17, 2014 |
9585570 |
|
|
15410902 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01S 3/115 20130101;
H01S 3/1305 20130101; H01S 3/042 20130101; A61B 5/0095 20130101;
H01S 3/1625 20130101; H01S 3/092 20130101; A61B 5/14542 20130101;
H01S 3/0407 20130101; H01S 3/1633 20130101; H01S 3/1317 20130101;
H01S 3/1636 20130101; H01S 3/106 20130101; H01S 3/0404
20130101 |
International
Class: |
A61B 5/00 20060101
A61B005/00; H01S 3/04 20060101 H01S003/04; H01S 3/042 20060101
H01S003/042; H01S 3/092 20060101 H01S003/092; H01S 3/115 20060101
H01S003/115; H01S 3/16 20060101 H01S003/16; A61B 5/145 20060101
A61B005/145; H01S 3/131 20060101 H01S003/131 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 26, 2013 |
JP |
2013-133910 |
Claims
1.-8. (canceled)
9. A laser apparatus, comprising: a laser medium; temperature
controlling means configured to control a temperature of the laser
medium; excitation means configured to excite the laser medium;
control means configured to control the temperature controlling
means and the excitation means; first temperature measuring means
configured to measure a first temperature of the laser medium; and
second temperature measuring means configured to measure a second
temperature of a substance which is circulated near the laser
medium for heating the laser medium, wherein the control means is
configured to control the excitation means based on the first
temperature and the second temperature.
10. The laser apparatus according to claim 9, wherein the control
means is configured not to activate the excitation means until the
first temperature reaches a first predetermined value.
11. The laser apparatus according to claim 10, wherein the first
predetermined value is 80 degrees Celsius.
12. The laser apparatus according to claim 9, wherein the control
means is configured not to activate the excitation means until the
second temperature reaches a second predetermined value.
13. The laser apparatus according to claim 12, wherein the second
predetermined value is larger than 20 degrees Celsius and smaller
than 80 degrees Celsius.
14. The laser apparatus according to claim 10, wherein the control
means is configured to activate the temperature controlling means
for heating the laser medium until the first temperature reaches
the first predetermined value.
15. The laser apparatus according to claim 9, wherein the
temperature controlling means includes a circulator circulating the
substance near the laser medium, and heating means heating the
substance circulating within the circulator.
16. The laser apparatus according to claim 15, wherein the control
means activates the heating means until the temperature of the
laser medium becomes stable, and activates the excitation means
after the temperature of the laser medium is stabilized.
17. The laser apparatus according to claim 9, wherein the control
means is configured to control so that peaks of power consumption
between the heating means and the excitation means do not
overlap.
18. The laser apparatus according to claim 9, further comprising:
light intensity measuring means configured to measure a light
intensity of a laser beam, wherein the control means is configured
to activate the excitation means after the light intensity of the
laser beam for a prescribed period becomes stable within a
predetermined range.
19. The laser apparatus according to claim 10, wherein a power
consumption to flow to the heating means after the second
temperature reaches a second predetermined value and until the
first temperature of the laser medium reaches a first predetermined
value, is smaller than a power consumption to flow to the heating
means until the second temperature reaches the second predetermined
value.
Description
RELATED APPLICATIONS
[0001] This application is a divisional of application Ser. No.
14/306,390, filed Jun. 17, 2014. It claims benefit of that
application under 35 U.S.C. .sctn.120, and claims benefit under 35
U.S.C. .sctn.119 of Japanese Patent Application No. 2013-133910
filed on Jun. 26, 2013. The entire contents of each of the
mentioned prior applications are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] Field of the Invention
[0003] The present invention relates to an object information
acquiring apparatus and a laser apparatus.
[0004] Description of the Related Art
[0005] Conventionally, photoacoustic apparatuses which cause an
object to be irradiated with pulsed light, receive the
photoacoustic waves generated inside the object with a probe, and
image the form or function inside the object have been researched
considerably in the medical field. As a pulse light source of the
photoacoustic apparatus, a high-output solid-state laser is used.
In order to stabilize the amount of pulsed light of the solid-state
laser, it is necessary to stabilize the temperature inside the
pulse light source.
[0006] Thus, proposed is a laser apparatus that performs a
warming-up operation until the temperature inside the pulse light
source becomes stable. Patent Literature 1 discloses an apparatus
that performs a warming-up operation when the apparatus is turned
ON, and determines a correction coefficient of the laser output
command value after the temperature inside the light source falls
within a predetermined range.
[0007] Moreover, a circulator for stabilizing the temperature
inside the light source during emission is proposed in Patent
Literature 2. With the circulator of Patent Literature 2,
stabilization of the laser output is sought by circulating and
supplying, to a laser oscillation unit, a cooling medium that is
controlled for causing the temperature to be constant.
[0008] Moreover, flash lamps are often used as the excitation
source of the solid-state laser. By performing Q-switching after
causing the flash lamp to emit light and exciting the laser medium,
sudden laser oscillation is generated to output a strong laser beam
known as a giant pulse.
[0009] Patent Literature 1: Japanese Patent Application Laid-Open
No. 2005-251855
[0010] Patent Literature 2: Japanese Patent Application Laid-Open
No. H11-097769 (1999-097769)
SUMMARY OF THE INVENTION
[0011] In Patent Literature 1, when the inside of the light source
is cold, the time spent on the warming-up operation for heating the
inside will be long. When the flash lamp is caused to emit light
during that period, it may not be possible to obtain the required
output due to the wear of the flash lamp, and the life of the light
source may become shortened.
[0012] In Patent Literature 2, while the laser is stabilized based
on the temperature control of the cooling medium, there is no
description regarding the reduction of wear of the flash lamp
during the warming-up operation.
[0013] The present invention was devised in view of the foregoing
problems, and an object of this invention is to provide a laser
apparatus capable of reducing the wear of the flash lamp.
[0014] The present invention provides an object information
acquiring apparatus, comprising:
[0015] a laser medium;
[0016] temperature controlling means configured to control a
temperature of the laser medium;
[0017] excitation means configured to excite the laser medium;
[0018] control means configured to control the temperature
controlling means and the excitation means;
[0019] a probe configured to receive acoustic waves that are
generated when an object is irradiated with a laser beam from the
laser medium; and
[0020] processing means configured to acquire characteristic
information relating to the object in use of the acoustic
waves,
[0021] wherein the control means does not operate the excitation
means until the temperature of the laser medium falls within a
predetermined range.
[0022] The present invention also provides a laser apparatus,
comprising:
[0023] a laser medium;
[0024] temperature controlling means configured to control a
temperature of the laser medium;
[0025] excitation means configured to excite the laser medium;
and
[0026] control means configured to control the temperature
controlling means and the excitation means,
[0027] wherein the control means does not operate the excitation
means until a temperature of the laser medium falls within a
predetermined range.
[0028] According to the present invention, it is possible to
provide a laser apparatus capable of reducing the wear of the flash
lamp.
[0029] Further features of the present invention will become
apparent from the following description of exemplary embodiments
with reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is a block configuration diagram in Embodiment 1;
[0031] FIG. 2 is an operational flowchart in Embodiment 1;
[0032] FIG. 3 is a block configuration diagram of the laser power
source in Embodiment 1;
[0033] FIG. 4 is a block configuration diagram of the temperature
control mechanism in Embodiment 1;
[0034] FIG. 5 is an operational flowchart of the laser emission in
Embodiment 1;
[0035] FIGS. 6A and 6B are diagrams showing the time change of the
temperature and power consumption in Embodiment 1;
[0036] FIG. 7 is a block configuration diagram in Embodiment 2;
and
[0037] FIG. 8 is an operational flowchart in Embodiment 2.
DESCRIPTION OF THE EMBODIMENTS
[0038] The preferred embodiments of the present invention are now
explained with reference to the appended drawings. However, the
size, material, shape and relative arrangement of components
described below are to be suitably changed depending on the
configuration and various conditions of the apparatus to which the
present invention is to be applied, and these embodiments are not
intended to limit the scope of the present invention to the
following descriptions.
[0039] The object information acquiring apparatus of the present
invention includes an apparatus that uses the photoacoustic effect
of receiving acoustic waves generated in an object by causing that
object to be irradiated with light (electromagnetic waves), and
acquiring the object information as image data.
[0040] The object information acquired in the foregoing case
indicates the generation source distribution of the acoustic waves
that are generated based on light irradiation, the initial sound
pressure distribution in the object, the light energy absorption
density distribution derived from the initial sound pressure
distribution, the absorption coefficient distribution, or the
concentration information distribution of substances configuring
the tissues. The concentration information distribution of
substances is, for example, the oxygen saturation distribution or
oxidized/deoxygenated hemoglobin concentration distribution or the
like.
[0041] The acoustic waves referred to in the present invention are
typically ultrasound waves, and include elastic waves referred to
as sound waves, ultrasound waves, and acoustic waves. In
particular, the acoustic waves that are generated based on the
photoacoustic effect are referred to as photoacoustic waves or
photoacoustic ultrasonic waves. An acoustic detector (for instance,
a probe) receives the acoustic waves that were generated or
reflected in the object.
[0042] The present invention is unique in being able to reduce the
wear of the flash lamp of the laser apparatus. Accordingly, the
present invention can be applied not only to an object information
acquiring apparatus, but can also be deemed an invention that is
related to a laser apparatus. Moreover, the present invention can
also be deemed the control method of these apparatuses or the
program for causing an information processing apparatus to execute
the foregoing control method. In the ensuing explanation, a light
source controller is described as a representative example of the
laser apparatus.
Embodiment 1
[0043] In Embodiment 1, the flash lamp does not emit light until
the temperature sensor near the flash lamp falls within a
predetermined range.
[0044] (Apparatus Configuration)
[0045] FIG. 1 is a block configuration diagram of the light source
controller (laser apparatus) in this embodiment. The function and
operation of the respective blocks are explained below.
[0046] A laser controller 101 controls a laser power source, a
laser head and an optical system. The laser controller 101 can
receive operations from a user, and can also work under the command
of a higher-level controller by being connected thereto. The laser
controller corresponds to the control means of the present
invention.
[0047] A laser power source 102 is a variable voltage power source
that supplies an electric charge to a capacitor 110. The laser
power source 102 has the function of supplying an electric charge,
at a constant current, to the capacitor 110 until the
inter-terminal voltage of the capacitor 110 reaches a preset
voltage based on a command from the laser controller 101. Moreover,
the laser power source 102 has the function of notifying to the
laser controller 101 a voltage that is proportional to the
inter-terminal voltage of the capacitor 110.
[0048] A pulse-forming network 103 accumulates the electric charge
from the laser power source 102, and generates a high current pulse
for causing a flash lamp 116 to emit light. The pulse-forming
network is referred to as "PFN" in the ensuing explanation.
[0049] A laser optical system 104 indicates a laser head and an
optical system comprising a flash lamp for exciting the laser
medium. The laser optical system (and laser head) can output a
plurality of wavelengths.
[0050] A processor 105 is mounted on the laser controller 101, and
controls the various sensors and actuators of the laser power
source 102, the PFN 103, and the laser optical system 104 (and
laser head). The processor 105 is a semiconductor chip configured
from a micro controller and peripheral circuits, and performs
emission control, changes parameters such as the light intensity
and wavelength, sets and monitors the laser power source voltage,
performs shutdown during an abnormality and the like based on
software running on the chip. Moreover, the processor 105 performs
control for starting, suspending and stopping the operation of the
laser power source 102 and a temperature control mechanism 128.
[0051] A commercial power supply 106 is a power source of AC 200 V
that is input to the laser controller 101. The AC 200 V of the
commercial power supply 106 is converted into a DC voltage by the
DC power supply not shown inside the laser controller 101, and used
for activating the processor 105. Moreover, the commercial power
supply 106 is distributed to the laser power source 102 and the
temperature control mechanism 128 via the laser controller 101.
[0052] A laser power supply unit 107 is a circuit for supplying the
commercial power supply 106 to the laser power source 102 based on
a signal from the processor 105, and is configured from a relay and
an output connector. By controlling the short-circuit and release
of the relay from the processor 105, the activation and stopping of
the laser power source 102 can be controlled.
[0053] A temperature control power supply unit 108 is a circuit for
supplying the commercial power supply 106 to the temperature
control mechanism 128 based on a signal from the processor 105, and
is configured from a relay and an output connector. By controlling
the short-circuit and release of the relay from the processor 105,
the activation and stopping of the temperature control mechanism
128 can be controlled.
[0054] A discharge circuit 109 is a circuit for discharging the
electric charge accumulated in the capacitor 110, and is configured
from a relay and a current limiting resistor. The electric charge
of the capacitor 110 can be discharged by short-circuiting the
relay based on a control signal from the processor 105.
[0055] A capacitor 110 accumulates the electric charge for causing
the flash lamp 116 to emit light. A high-voltage, large-capacity
film capacitor or the like is used as the capacitor 110.
[0056] A coil 111 shapes the pulsed current waveform from the
capacitor.
[0057] A thyristor 112 controls whether to cause the electric
charge of the capacitor 110 to flow to the flash lamp 116 in the
laser optical system 104 based on a control signal from the
processor 105.
[0058] An igniter 113 applies a high voltage to the flash lamp 116
based on a control signal from the processor 105, and forms a
conducting path. The igniter circuit is configured from a high
voltage DC-DC converter and a current limiting resistor.
[0059] A simmer circuit 114 is a circuit for causing a constant
standby current to flow to the flash lamp 116 in order to maintain
the conducting path formed in the flash lamp 116. The simmer
circuit 114 is configured from a constant current circuit and a
backflow prevention diode.
[0060] A high voltage relay 115 blocks the thyristor 112 from the
flash lamp 116 while the igniter 113 is applying a high voltage to
the flash lamp 116. As a result of the processor 105 sending a
control signal to the thyristor 112 in a state where a standby
current is flowing to the flash lamp 116 and the high voltage relay
is short-circuited, the electric charge of the capacitor 110 is
transferred to the flash lamp 116, and the flash lamp 116 emits
light.
[0061] The flash lamp 116 emits excitation light for exciting the
laser medium. The flash lamp corresponds to the excitation means of
the present invention.
[0062] Reference numeral 117 to reference numeral 121 are
components configuring the laser resonator.
[0063] A laser medium 117 is a crystal such as YAG, titanium
sapphire, or alexandrite disposed near the flash lamp. In this
embodiment a case of using alexandrite is explained. An alexandrite
laser yields higher luminous efficiency and greater optical output
at a temperature that is higher than normal temperature. Thus, the
temperature of the laser medium needs to be maintained at a
temperature that is higher than normal temperature. Thus, the
temperature control mechanism 128 uses a circulator and causes a
fluid substance such as water of approximately 80 degrees Celsius
to circulate near the laser medium so as to maintain the required
temperature for obtaining sufficient optical output.
[0064] Reference numeral 118 is a reflecting mirror.
[0065] A wavelength switching mechanism 119 is configured from a
birefringent filter and an activating motor. The birefringent
filter can be operated and one resonating wavelength can be
selected among a plurality of wavelengths based on a control signal
from the processor 105. This embodiment explains a case of
selecting one wavelength from two types of wavelengths. These
wavelengths are hereinafter respectively referred to as a first
wavelength and a second wavelength in the ensuing explanation. When
a laser apparatus capable of generating a plurality of wavelengths
is applied to an object information acquiring apparatus, the
substance concentration in the object can be acquired as
characteristic information.
[0066] The electrooptic element 120 performs Q-switching based on a
control signal from the processor 105.
[0067] Reference numeral 121 is an output mirror.
[0068] A wavelength sensor 122 is mounted on the wavelength
switching mechanism 119, and outputs to the processor 105 a signal
indicating the currently selected wavelength. A high level voltage
is output when the position of the wavelength switching mechanism
119 is at a position corresponding to the first wavelength, and a
low level voltage is output when the position of the wavelength
switching mechanism 119 is at a position corresponding to the
second wavelength.
[0069] The beam splitter 123 branches a part of the laser beam that
was output via the output mirror 121, and causes that branched
laser beam to enter an actinometer 124. However, most of the light
takes a straight line and enters the shutter 125. The actinometer
corresponds to the light intensity measuring means of the present
invention.
[0070] The actinometer 124 is a circuit for measuring the energy
for each pulse notifying the result to the processor 105, and is
configured from a pyroelectric sensor or a photodiode and an
amplifier circuit.
[0071] A shutter 125 switches to impellent selection between
whether to output the laser beam outward based on a control signal
from the processor 105 or not.
[0072] A memory 126 is a nonvolatile memory for storing various
setting parameters. For example, let it be assumed that a
correspondence relation of the voltage to be output by the laser
power source 102 and the light intensity output by the light source
is calibrated in advance for each wavelength, and stored in the
memory 126. Consequently, when the user designates the light
intensity and wavelength to be output, the processor 105 can
estimate and set the voltage to be set in the laser power source
102.
[0073] A switch 127 is a switch with a key that is used for
activating the light source.
[0074] A temperature control mechanism 128 is a mechanism for
stabilizing the temperature near the laser medium. The temperature
control mechanism 128 comprises a pump for circulating water of a
constant temperature in the chassis housing the laser medium 117
and the flash lamp 116. The temperature control mechanism 128
internally comprises an electrothermal heater, a cooling fan, a
thermometer, and a temperature controller. The temperature
controller measures the temperature of the circulating water using
a thermometer, and controls the water temperature to be maintained
at 80 degrees using a heater and a cooling fan. When the water
temperature is around 20 degrees as with the room temperature
immediately after activation, the water is heated to 80 degrees
with the electrothermal heater. During the laser emission, a part
of the energy of the flash lamp turns into heat and the water
temperature attempts to reach 80 degrees or higher, but control is
performed using a cooling fan so that the water temperature does
not considerably exceed 80 degrees. The temperature control
mechanism corresponds to the temperature controlling means of the
present invention.
[0075] A lamp house 129 is a housing that houses the flash lamp 116
and the laser medium 117 near each other in a single housing. By
disposing the flash lamp 116 and the laser medium 117 near each
other, the excitation light of the flash lamp is efficiently
absorbed by the laser medium, and energy that is lost as heat can
be reduced.
[0076] A temperature sensor 130 is mounted on the lamp house. As
the temperature sensor, used may be a thermocouple, a thermistor,
an infrared temperature sensor or the like. A signal from the
temperature sensor 130 is input to the processor 105. The processor
controls the operation of the temperature control mechanism 128 and
the laser power source 102 based on temperature information.
Specifically, the temperature control mechanism 128 is activated
but the laser power source 102 is not activated until the
temperature of the laser medium nears 80 degrees. Once the
temperature is stabilized near 80 degrees, the laser power source
is activated to emit light from the flash lamp, and the actinometer
124 is used for confirming whether the light intensity is stable.
Subsequently, while the operation of the temperature control
mechanism 128 is continued until the object to be actually
irradiated with the laser is set up, the emission of the flash lamp
is stopped, and a simmer current is caused to flow. After the setup
of the object is complete, the laser power source is activated and
light is emitted from the flash lamp, the actinometer 124 is used
for confirming the light intensity is stable, and the object is
thereby irradiated with the laser.
[0077] (Processing Flow)
[0078] FIG. 2 is an operational flowchart of the activation and
operation of the light source upon using the laser controller of
the present invention.
[0079] When the user turns on the switch 127 attached to the laser
controller, in step S201, the processor 105 sends a control command
to the temperature control power supply unit 108, and starts
supplying the commercial power supply 106 to the temperature
control mechanism 128. The operation of the temperature control
mechanism 128 is thereby started, and the heating of water by the
electrothermal heater is started. In other words, the
electrothermal heater corresponds to the heating means of the
present invention.
[0080] Subsequently, in step S202, the processor 105 reads the
signal from the temperature sensor 130 and calculates the
temperature.
[0081] Subsequently, in step S203, the processor 105 determines
whether the temperature of the temperature sensor 130 is within a
predetermined range. A predetermined range in this embodiment is a
case where the temperature is 80 degrees or higher. When the
temperature is 80 degrees or higher (S202=YES), it is determined
that the laser medium 117 has been sufficiently warmed, and the
routine proceeds to step S204. Meanwhile, when the temperature is
lower than 80 degrees (S202=NO), the routine returns to step S202,
and, after the lapse of a given period of time, a signal of the
temperature sensor 130 is once again read and the temperature is
calculated.
[0082] Subsequently, in step S204, the high voltage power source is
turned ON. In other words, the processor 105 sends a control
command to the laser power supply unit 107, and starts supplying
the commercial power supply 106 to the laser power source 102. The
laser power source is thereby activated.
[0083] Subsequently, in step S205, the laser controller 101
controls the laser power source 102, the PFN 103 and the laser
optical system 104, and thereby emits a laser. The operational flow
of laser emission will be described later.
[0084] Note that, in step S205, the processor 105 keeps the shutter
125 closed to prevent the laser beam from being output outside the
laser optical system 104. A part of the laser beam is input to the
actinometer 124.
[0085] Subsequently, in step S206, the processor 105 sends a signal
to the actinometer 124, reads the light intensity value for each
pulse, and stores the result in the memory of the processor
105.
[0086] Subsequently, in step S207, whether the light intensity
value of a prescribed period is stable within a predetermined range
is confirmed. When a state where the light intensity is within a
predetermined range continues (S207=YES), the warming-up is deemed
complete since the pulsed light is sufficiently stable, and the
routine proceeds to step S208. Meanwhile, when the light intensity
does not fall within a predetermined range within a predetermined
time (S207=NO), it is determined that the pulsed light cannot be
stabilized even when sufficient warming-up is performed, and the
routine proceeds to step S215.
[0087] In step S208, the laser controller 101 enters a standby
state since the warming-up is deemed complete. A control command is
sent to the laser power source 102 and the PFN 103, and the
charge/discharge of the capacitor 110 and the emission of the flash
lamp 116 are stopped. Meanwhile, a control command is sent to the
simmer circuit 114, and a standby current is caused to flow to the
flash lamp 116.
[0088] Subsequently, in step S209, the laser controller 101 stands
by until the object is prepared. The preparation of an object
refers to the user setting up an object at a position to be
irradiated with a laser beam, setting the irradiation position and
number of pulses, and giving an instruction for starting the laser
irradiation. The processor 105 proceeds to step S210 upon receiving
a laser irradiation start instruction from the switch 127 or an
higher-level controller.
[0089] In step S210, the laser controller 101 controls the laser
power source 102, the PFN 103 and the laser optical system 104, and
thereby emits a laser as in step S205.
[0090] Subsequently, in step S211, the processor 105 sends a signal
to the actinometer 124 and reads the light intensity value for each
pulse, and stores the result in the memory of the processor 105.
Subsequently, in step S212, whether the light intensity value of a
prescribed period is stable within a predetermined range is
confirmed as in step S207. When it is determined that the pulsed
light is stable (S212=YES), the routine proceeds to step S213.
Meanwhile, when it is determined that the pulsed light cannot be
stabilized even upon performing sufficient warming-up (S212=NO),
the routine proceeds to step S215.
[0091] Subsequently, in step S213, the processor 105 sends a
control command to the shutter 125, and opens the shutter.
[0092] Subsequently, in step S214, the laser is emitted for
irradiating the object. In addition, after a laser of a pre-set
number of pulses is emitted, the laser power source 102 and the
temperature control mechanism 128 are stopped, and the processing
is ended.
[0093] Meanwhile, in step S215, the processor 105 notifies an error
to the user and the higher-level controller to the effect that the
light intensity cannot be stabilized, and thereafter stops the
laser power source 102 and the temperature control mechanism 128,
and ends the processing.
[0094] (Structure of Laser Power Source)
[0095] FIG. 3 is a block diagram showing the internal structure of
the laser power source 102.
[0096] A power source 301 is a power source of AC 200 V supplied
from the laser power supply unit 107.
[0097] An AC-DC converter 302 converts the AC 200 V into a direct
current.
[0098] An inverter 303 converts the direct current into an
alternating current.
[0099] A transformer 304 boosts the voltage from the inverter.
[0100] A power source controller 305 turns ON/OFF the FET not shown
in the inverter, and controls the DUTY ratio of the inverter output
in order to output a constant current to the PFN 103.
[0101] A voltage dividing resistor 306 divides the voltage that was
boosted with the transformer 304, and feeds back the divided
voltage to the power source controller.
[0102] A signal 311 that is fed back by the voltage dividing
resistor 306 is referred to as a feedback signal. Moreover, an
output start signal 307, a voltage setting signal 308, an output
completion signal 309, and a monitor signal 310 are interfaces
between the power source controller and the laser controller.
[0103] The output start signal 307 is a one-bit digital signal,
and, when the laser controller 101 is outputting a high level, the
power source controller 305 operates the inverter 303 and supplies
a constant current to the PFN 103. Meanwhile, when the laser
controller 101 of FIG. 1 is outputting a low level, the power
source controller 305 stops the inverter 303.
[0104] The voltage setting signal 308 is an analog signal in the
range of 0 V to 10 V, and is used for setting the amount of
electric charge to be accumulated in the capacitor 110. The
electric charge is supplied to the capacitor 110 in the PFN 103
until the inter-terminal voltage of the capacitor 110 becomes a
voltage that is proportional to the voltage of the voltage setting
signal 308. The power source controller 305 activates the inverter
303 and charges the capacitor 110 when the voltage of the feedback
signal 311 is smaller than the input voltage from the voltage
setting signal 308. Meanwhile, the power source controller 305
stops the inverter 303 when the voltage of the feedback signal 311
is equal to or greater than the voltage of the voltage setting
signal 308.
[0105] The output completion signal 309 is a one-bit digital
signal, and is a signal indicating whether the electric charge is
being accumulated in the capacitor 110, or whether the charging is
complete. When the voltage of the feedback signal 311 is smaller
than the voltage of the voltage setting signal 308, the power
source controller 305 determines that charging is being performed,
and changes the output completion signal to a high level.
Meanwhile, when the voltage of the feedback signal 311 is equal to
or greater than the voltage of the voltage setting signal 308, the
power source controller 305 determines that the charging is
complete, and changes the output completion signal 309 to a low
level.
[0106] The monitor signal 310 is an analog signal in the range of 0
V to 10 V, and a voltage that is proportional to the inter-terminal
voltage of the capacitor 110 is output from the laser power source
102 to the laser controller 101. The power source controller 305
performs noise reduction and impedance conversion based on the
voltage of the feedback signal 311, and outputs the result to the
laser controller 101.
[0107] (Structure of Temperature Control Mechanism)
[0108] FIG. 4 is an internal block configuration diagram of the
temperature control mechanism 128.
[0109] A water tank 401 is a container for storing water.
[0110] A temperature controller 402 controls the water temperature
to be a preset temperature.
[0111] An electrothermal heater 403 heats the water. The current of
the electrothermal heater can be controlled from the temperature
controller 402.
[0112] A water level gauge 404 measures the water level in the
water tank 401.
[0113] A water pipe 405 supplies water from the water tank 401 to
the lamp house 129. In addition, water returns to the water tank
401 from the lamp house 129 via the water pipe 406.
[0114] A thermometer 407 measures the water temperature in the
water pipe 405.
[0115] The temperature controller 402 monitors the water
temperature of the water pipe 405 by referring to the measurement
result of the thermometer 407. The thermometer corresponds to the
temperature measuring means of the present invention.
[0116] Moreover, a pump 408 circulates water through the path of
the water tank 401, the water pipe 405, the flash lamp 116, and the
water pipe 406.
[0117] A flow meter 409 measures the flow rate of water in the
water pipe 406.
[0118] A pressure gauge 410 measures the water pressure in the
water pipe 405. The temperature controller 402 monitors the values
of the water level gauge 404, the flow meter 409, and the pressure
gauge 410, displays a warning when the water level is outside a
predetermined range, and stops the pump 408. Moreover, in the
foregoing case, the temperature controller 402 communicates with
the laser controller 101 and notifies an error.
[0119] Moreover, a fan 411 cools the water of the water pipe 406.
The rotation of the fan can be controlled with the temperature
controller 402. The temperature controller 402 reads the value of
the thermometer 407, and performs feedback control of the current
of the electrothermal heater 403 and the rotation of the fan 411 so
that the value coincides with the temperature setting value from
the laser controller 101. As the control algorithm, PID control is
performed based on a measurement error between the temperature
setting value and the thermometer 407.
[0120] As described above, the temperature control mechanism 128
performs temperature control of the laser medium by controlling the
water temperature when the flash lamp 116 and the laser medium 117
are stored in the lamp house 129.
[0121] (Processing Flow of Laser Emission)
[0122] FIG. 5 is a diagram showing the operational flowchart of
laser emission. This diagram is the operational flow when the laser
controller repeatedly emits pulsed light.
[0123] In step S501, the processor 105 sets the output. In other
words, the processor 105 reads the light intensity and wavelength
set by the user, and sets the voltage value in the laser power
source 102. Let it be assumed that the relation of the light
intensity and the voltage is recorded in the memory 126. Moreover,
the processor 105 sends a control command to the wavelength
switching mechanism 119 based on the wavelength set by the user,
and selects the birefringent filter for outputting the set
wavelength. When the operation of the wavelength switching
mechanism is complete, the wavelength sensor 122 outputs to the
laser controller 101 a signal indicating the selected wavelength.
Moreover, in step S501, the processor 105 reads the number of
repetitions of the pulsed light set by the user, and internally
stores that number.
[0124] Subsequently, in step S502, the processor 105 sends a
control signal to the simmer circuit 114, and starts outputting a
current from the simmer circuit. However, since a conducting path
is not formed in the flash lamp 116 at this stage, the simmer
current will hardly flow to the flash lamp 116.
[0125] Subsequently, in step S503, when a conducting path is not
formed in the flash lamp 116, the processor 105 sends a control
signal to the igniter circuit 113, and applies a high voltage to
the flash lamp 116. This operation is referred to as "ignition".
Consequently, the flash lamp 116 is discharged, a conducting path
is formed therein, and the current output from the simmer 114 flows
to the flash lamp 116. Note that whether a conducting path is
formed in the flash lamp is determined based on whether the simmer
circuit 114 is causing a simmer current to flow to the flash
lamp.
[0126] Subsequently, in step S504, the processor 105 sends a
control signal to the discharge circuit 109, and releases the relay
of the discharge circuit. Consequently, the positive-side terminal
and the negative-side terminal of the capacitor 110 are released,
and an electric charge can be accumulated in the capacitor 110.
[0127] Subsequently, in step S505, the processor 105 sends a
control signal to the laser power source 102, and causes a constant
current to be output to the capacitor 110. Consequently, an
electric charge is accumulated in the capacitor 110 at a constant
ratio, and the inter-terminal voltage of the capacitor 110 will
rise. The laser power source 102 stops the current output at the
time that the inter-terminal voltage of the capacitor 110 reaches
the voltage that was set in step S501.
[0128] In step S506, the processor 105 sends a control signal to
the relay 115, and short-circuits the connection between the
thyristor 112 and the flash lamp 116.
[0129] Subsequently, in step S507, the processor 105 sends a
control signal to the thyristor 115 and turns ON the thyristor.
Consequently, the gap from the capacitor 110 to the flash lamp 116
is connected via the coil 111. The electric charge accumulated in
the capacitor 110 flows to the flash lamp 116, and light is emitted
from the flash lamp 116. When the electric charge accumulated in
the capacitor 110 runs out, the thyristor 115 is turned OFF.
Moreover, the light from the flash lamp 116 is absorbed by the
laser medium 117, and the laser medium 117 excited.
[0130] Subsequently, in step S508, the processor 105 sends a
control signal to the Q-switch driver circuit not shown several 100
microseconds after the excitation, and reduces the loss of the
Q-switch (QSW), which was theretofore in a state of great loss, to
be a small loss. This is performed by changing the inter-terminal
voltage of the electrooptic element from a high voltage to a low
voltage. Consequently, sudden laser oscillation will occur, and a
giant pulse is output from the output mirror 121.
[0131] Subsequently, in step S509, it is determined whether the
laser emission for the number of times set in step S501 is
complete. When complete (S509=YES), the routine proceeds to step
S510. Meanwhile, when incomplete (S509=NO), the routine proceeds to
step S505, and an electric charge is once again accumulated in the
capacitor 110.
[0132] In step S510, the processor 105 closes the shutter 125 and
sends a control signal to the relay 115, and releases the thyristor
112 and the flash lamp 116. Moreover, the processor 105 sends a
control signal to the discharge circuit 109, and short-circuits the
terminals of the capacitor 110 via the current limiting resistor in
the discharge circuit. The electric charge remaining in the
capacitor 110 is thereby discharged.
[0133] (Timing of Operation and Emission Period)
[0134] FIG. 6A is a diagram showing the time change of the
temperature near the lamp house 129 detected with the temperature
sensor 130 and the operating time of the flash lamp 116. FIG. 6B is
a diagram showing the time change of the laser emission power
supplied to the laser power source 102 and the temperature control
power supplied to the temperature control mechanism 128.
[0135] Foremost, the operational flow from the warming-up to the
irradiation of the object with a laser, and the temperature of the
lamp house 129 and the emission time of the flash lamp 116 are
explained with reference to FIG. 6A.
[0136] In FIG. 6A, a graph 601 shows the time change of the
temperature near the lamp house 129. The vertical axis represents
the temperature, and the horizontal axis represents the time. A
graph 602 shows the operating time of the flash lamp 116. The graph
shows that operation in the vertical axis is a high level, and no
operation in the vertical axis is a low level. The horizontal axis
represents the time.
[0137] At time t601, the laser controller 101 starts the
warming-up. Time t601 corresponds to step S201 of FIG. 2. At this
stage, the temperature near the lamp house 129 is around 20 degrees
(TEMP1), which is the same as the room temperature.
[0138] When the temperature control mechanism 128 starts the
operation in step S201, the temperature controller 402 starts
applying electricity to the electrothermal heater 403 since the
value of the thermometer 407 is lower than the preset temperature
of 80 degrees (TEMPS). Consequently, the water in the water tank
401 is heated, supplied to the flash lamp 116 by the pump 408, and
the temperature of the lamp house thereby gradually increases.
[0139] The time that the scale reading of the thermometer 407
basically reaches the preset temperature is referred to as t602.
From time t602 onward, the temperature controller 402 controls the
current of the electrothermal heater 403 so as to maintain the
water temperature at the preset temperature. At this stage the
water temperature is approximately 80 degrees, but since it takes
time for heat to be transmitted to the lamp house 129, the scale
reading of the temperature sensor 130 will be a value (TEMP2) that
is lower than 80 degrees.
[0140] While the water of the preset temperature is being
circulated, heat will be sufficiently transmitted to the lamp house
129, and, at time t603, the value of the temperature sensor 130
exceeds the preset temperature. Then, the routine proceeds to the
processing of step S204, and the power source of the laser power
source 102 is turned ON. The laser medium 117 and the flash lamp
116 are housed in the lamp house 129, and, since the temperature of
the laser medium 117 is stable at 80 degrees at this stage, it is
determined that the preparation for laser emission is complete.
[0141] At time t604, the laser emission and the light intensity are
confirmed based on step S205 and step S206. When the light
intensity is stable after emitting the laser for a predetermined
number of pulses, the emission of the flash lamp is stopped in step
S208 and step S209, and flash lamp stands by until the preparation
of the object is complete.
[0142] When the preparation of the object is complete at time t606,
the laser emission and the light intensity are confirmed based on
step S210 and step S211. When the light intensity is stable after
emitting the laser for a predetermined number of pulses, the object
is irradiated with the laser in step S213 and step S214.
[0143] After emitting the laser for a predetermined number of
pulses, the flash lamp is stopped at time t607.
[0144] As described above, the only time that the flash lamp emits
light during the operation from the warming-up to the laser
irradiation is only between time t604 and time t605, and between
time t606 and time t607. The flash lamp 116 does not emit light
during the heating time of the laser medium 117 (t601 to t603) and
the preparation time of the object (t605 to t606), which take time.
It is thereby possible to reduce the wear of the flash lamp, and
extend the life of the flash lamp.
[0145] Moreover, during the period from time t603 to time t607, the
temperature of the laser medium 117 is maintained near the preset
temperature by the circulating water from the temperature control
mechanism 128.
[0146] (Timing of Operation and Power Consumption)
[0147] Moreover, the present invention yields an effect of being
able to reduce the peak of power consumption, even though it takes
time to perform the warming-up, in comparison to the case of
simultaneously activating the excitation means and the temperature
controlling means during the warming-up. This effect is now
explained with reference to FIG. 6B.
[0148] In FIG. 6B, a graph 603 shows the power consumption of the
temperature control mechanism 128, and a graph 604 shows the power
consumption of the laser power source 102. The vertical axis
represents the power consumption, and the horizontal axis
represents the time. Note that, in FIG. 6B, the origins of the
vertical axis of the graph 603 and the graph 604 are displaced for
easier viewing.
[0149] From time t601 to time t602, power is mainly consumed by the
electrothermal heater 403 that heats the water of the water tank
401 of the temperature control mechanism 128. Since the difference
between the water temperature (TEMP1) and the preset temperature
(TEMPS) is considerable immediately after the operation of the
temperature controller 402 is started, the temperature controller
402 attempts to heat the water quickly by causing a large current
to flow to the electrothermal heater 403. As the water temperature
gradually rises and the difference with the target temperature
decreases, the current that is caused to flow to the electrothermal
heater 403 by the temperature controller 402 becomes smaller. The
power consumption of the graph 603 also decreases accordingly.
[0150] From time t602 to time t603 and from time t605 to time t606,
in order to maintain the water temperature at the temperature
setting value, the temperature controller 402 causes a small
current to flow to the electrothermal heater 403 and the fan 411.
Moreover, the pump 408 is operated to maintain the circulation of
water. During these periods, the power consumption is basically
constant and lower than during the heating of water.
[0151] From time t604 to time t605 and from time t606 to time t607,
since a part of the energy becomes heat when the flash lamp 116
emits light, the lamp house 129 is heated. In order to cool the
lamp house 129 and maintain a constant temperature, the temperature
controller 402 performs control in which the current consumption of
the fan 411 increases and, therefore, the power consumption of the
temperature control mechanism 128 will slightly increase.
[0152] Meanwhile, the power consumption of the laser power source
102 is zero since a power source is not supplied from the laser
power supply unit 107 between time t601 and time t603.
[0153] From time t603 to time t604, while the power source
controller 305 and the AC-DC converter 302 are operated, the
inverter 303 and the transformer 304 are not operated and in an
idle state. The power consumption during this period slightly
increases.
[0154] From time t604 to time t605 and from time t606 to time t607,
the operation according to the routine shown in FIG. 5 is
performed. In other words, the inverter 303 and the transformer 304
are operated for causing the flash lamp 116 to emit light,
charge/discharge is performed to the capacitor 110, and the igniter
circuit 113 and the simmer circuit 114 are also operated. During
this period, the power consumption of the laser power source 102
will increase.
[0155] From time t605 to time t606, the charge/discharge to the
capacitor 110 is not performed. However, in order to cause the
flash lamp 116 to emit light as soon as the preparation of the
object is complete, the simmer circuit 114 is activated, and a
simmer current is caused to flow. Thus, while the power consumption
will increase for the amount of causing the simmer current to flow
in comparison to the idle state, the power consumption is lower in
comparison to the case of causing the flash lamp to emit light.
[0156] As shown in the graph 603 and the graph 604, the time (t601
to t602) when the power consumption of the temperature control
mechanism 128 is great and the time (t604 to t605 and t606 to t607)
when the power consumption of the laser power source 102 is great
do not overlap. It is thereby possible to lower the peak of power
consumption of the overall light source apparatus, and enable the
downsizing of the power source system and reduction of costs.
[0157] Moreover, upon heating the laser medium 117, preferably,
most of the power that can be supplied from the commercial power
supply 106 to the light source is assigned to the temperature
control mechanism 128, and most of the power that can be used
during the laser emission is assigned to the laser power source
102. It is thereby possible to obtain a high laser beam output with
less commercial power supply equipment.
[0158] Note that, in this embodiment, while the temperature control
and the temperature measurement were collectively performed in the
lamp house 129 housing the flash lamp 116 and the laser medium 117,
the present invention is not limited thereto. For example, in a
configuration where the laser medium and the flash lamp are
separated, the present invention can be applied by individually
performing the temperature control and the temperature
measurement.
[0159] Moreover, while this embodiment explained a case of causing
a simmer current to flow to the flash lamp 116 while the object is
being prepared, the operation to be performed during the
preparation is not limited thereto. When the preparation time of
the object is long, the simmer current may once be stopped, and the
igniter may be operated once the preparation is complete to perform
a discharge. It is thereby possible to reduce the power consumption
during the preparation period.
[0160] Moreover, while this embodiment explained a case of not
emitting light from the flash lamp until the temperature sensor 130
rises to a preset temperature, it is also possible to operate only
the temperature control mechanism partway, and subsequently perform
the temperature control and flash lamp emission simultaneously. For
example, the temperature controlling means is operated until
reaching a temperature (TEMP2) that is lower than the preset
temperature, and the flash lamp may emit light from t602 to t603.
While this will increase the wear of the flash lamp, the time
required until the lamp house 129 is heated can be shortened.
Moreover, the flash lamp emission can also be started from a
temperature between TEMP1 and TEMP2.
[0161] Moreover, while this embodiment determined that the
temperature of the laser medium is table when the temperature is
equal to or greater than the threshold in step S203, the
determination method of whether the temperature is stable is not
limited to the simple comparison of thresholds. For example, it is
also possible to determine that the temperature of the laser medium
is stable when a state in which the temperature sensor is within a
range of 80 degrees to 85 degrees continues for a given period of
time or longer.
[0162] Moreover, while this embodiment determines that the light
intensity is stable when a state where the light intensity is
within a certain range continues for a given period in step S212,
the method of determining whether the light intensity is stable is
not limited thereto. For example, it is also possible to calculate
the average value and scattering of the light intensity during a
certain period, and determine that the light intensity is stable
when the average value is within a certain range and the scattering
is not greater than a given value.
[0163] Moreover, while this embodiment performs the electrification
and blockage of the power source by the laser power supply unit 107
and the temperature control power supply unit 108 as the method of
realizing the start and stop of operations of the laser power
source 102 and the temperature control mechanism 128, and
activation/stopping method is not limited thereto. For example, a
separate control line may be provided to the power source
controller 305 and the temperature controller 402, and the
operation start/stop control may be realized by sending a control
signal from the processor 105.
[0164] Moreover, in this embodiment, while the temperature control
mechanism 128 controlled the water temperature by subjecting the
electrothermal heater 403 to PID control, the method of controlling
the water temperature is not limited thereto. For example, it is
also possible to use a heat pump in substitute for the
electrothermal heater to further improve the efficiency, and to
further reduce power consumption.
[0165] As explained above, the light source controller (laser
apparatus) of the present invention can reduce the wear of the
flash lamp and extend of the life of the flash lamp by causing the
flash lamp not to emit light until the laser medium is heated.
Moreover, in comparison to the case of simultaneously activating
the excitation means and the temperature controlling means during
the warming-up, the peak of power consumption of the overall light
source can be reduced, the power source system can be downsized,
and costs can be reduced.
Embodiment 2
[0166] An example of a system in which a light source controller
(laser apparatus) is applied to a photoacoustic apparatus (object
information acquiring apparatus) is now explained as Embodiment 2
of the present invention.
[0167] (Apparatus Configuration)
[0168] FIG. 7 is a block configuration diagram of the photoacoustic
apparatus. In FIG. 7, since a laser controller 701, a laser power
source 702, a PFN 703, a laser optical system 704, and a
temperature control system 705 respectively correspond to the laser
controller 101, the laser power source 102, the PFN 103, the laser
optical system 104, and the temperature control mechanism 128 of
Embodiment 1, the detailed explanation thereof is omitted.
[0169] An object 706 is the target to be measured by the
photoacoustic apparatus, and is a part of the test subject's body.
Here, the object is a breast as a part of the living body. The
light projection unit 707 irradiates the measurement segment of the
object with pulsed light.
[0170] A light projection unit 707 includes an optical system for
expanding the light emitted from the laser optical system at a
predetermined magnification, and adjusting the density and
irradiation region of the irradiation light. The transmission of
light from the laser optical system 704 to the light projection
unit 707 is performed via a bundle fiber or space transmission.
[0171] A light absorber 708 represents a segment with significant
light absorption that exists within the object and, for example,
corresponds to a newborn blood vessel caused by breast cancer in
the present case. When the light absorber 708 is irradiated with
pulsed light, photoacoustic waves 709 are generated based on the
photoacoustic effect.
[0172] A probe 710 internally comprises an oscillator for receiving
the photoacoustic waves 709. The oscillator is configured by
arranged ultrasonic sensor elements such as PZT or CMUT in an
array, and converts photoacoustic waves 709 into electrical
signals. These electrical signals are referred to as photoacoustic
signals.
[0173] A receiving circuit 711 receives the photoacoustic signals
from the probe 710. The receiving circuit 711 is configured from a
preamplifier, an A/D converter, a receiving memory, and an FPGA.
The photoacoustic signals are amplified with the preamplifier,
converted into a digital value with the A/D converter, and then
input to the FPGA. FPGA performs signal processing such as noise
reduction processing and phasing. The photoacoustic signals that
were subject to signal processing in the receiving circuit are
stored in a memory not shown. The data stored in the memory is
referred to as the photoacoustic signal data.
[0174] A controller 712 controls the operation of the overall
photoacoustic apparatus. The controller 712 is configuring from an
image processing circuit of a personal computer or a GPU. The image
processing circuit reads the photoacoustic signal data and performs
image reconfiguration processing, generates an image indicating the
absorption coefficient distribution relative to the pulsed light of
the object 706, and displays the generated image on a display 714.
The controller corresponds to the processing means of the present
invention. The display corresponds to the display means of the
present invention.
[0175] A user interface 713 is a block for the user to set the
operating conditions of the photoacoustic apparatus or giving an
operation start instruction. The user interface 713 is configured
from a keyboard, a mouse, a button switch and the like. As the
operating conditions, there are the measurement range of the object
706 and the measurement time of the photoacoustic signal. Moreover,
as the operation instruction, there is the start of photography or
end of photography of the object.
[0176] The display 714 is a display device for displaying the
diagnostic image and notifying the status of the photoacoustic
apparatus to the user.
[0177] The controller 712 is connected to the laser controller 701
via a communication cable 715, and is used for setting the laser
irradiation parameters, giving irradiation instructions, monitoring
the status, and so on.
[0178] As the irradiation parameters, there are the number of
pulses, light intensity and wavelength of the laser beam that is
used for irradiating the object 706. The user can set the
irradiation parameters via the user interface 713. Moreover, as the
contents of the irradiation instructions, there are the start of
warming-up and start of laser irradiation, and the user can control
the operation of the light source via the user interface.
[0179] Moreover, as the monitoring of the statue, there is the
monitoring of the value of the irradiation light intensity for each
pulse measured by the actinometer 124. When this light intensity is
transmitted to the controller 712 via the communication cable 715,
the signals can be corrected. Moreover, the status of the processor
105 can be transmitted to the controller 712 and displayed on the
display 714.
[0180] (Processing Flow)
[0181] FIG. 8 is a flowchart showing the operational flow of
Embodiment 2 of the present invention.
[0182] In step S801, the laser controller 701 is causes to start
the warming-up. Upon performing the warming-up, the laser
controller 701 performs step S201 to step S209 of FIG. 2, activates
the temperature control system 705, and stabilizes the temperature
of the laser optical system 704. As with Embodiment 1, light is not
emitted from the flash lamp 116 until the temperature of the laser
medium 117 is stabilized at a high temperature. It is thereby
possible to reduce the wear of the flash lamp.
[0183] Moreover, an instruction is issued to the laser power source
702 and the PFN 703, and a laser beam is emitted in a state where
the shutter 125 is closed, and whether an error is notified is
confirmed. The light source is thereby stabilized and the
preparations for starting the irradiation of the object 706 are
made. When an error was not notified while the laser controller 701
was performing the warming-up in step S802 (S802=NO), the routine
proceeds to step S803. When an error was notified (S802=YES), the
routine proceeds to step S811.
[0184] In step S803, the user sets the photographing parameters
through the user interface 713, and waits to give the irradiation
start instruction. During this period, the user sets the object 706
at a position where light can be irradiated using a holding
mechanism not shown. Since the object 706 is a part of the human
body, it may take time until preparations for photography are
complete for changing, other diagnosis, medical examination, and so
on. In the foregoing case, while much time is required for step
S803, since the laser controller 701 has stopped the emission of
the flash lamp in step S208, the wear of the flash lamp can be
suppressed.
[0185] Subsequently, in step S804, the controller 712 reads the
photographing parameters and stores them in the internal memory. As
the photographing parameters, there are the irradiation range of
the object 706 to be irradiated with the laser beam, and the list
of wavelengths of the laser beam to be irradiated. In this
embodiment, the two wavelengths of 756 nm and 797 nm are selected
as the irradiation wavelengths, and 100 pulses each are to be
irradiated with the respective wavelengths. In the foregoing case,
756 nm is the first wavelength, and 797 nm is the second
wavelength.
[0186] Subsequently, in step S805, the controller 712 sends to the
laser controller 701 the irradiation parameters pertaining to the
light source among the photographing parameters. The irradiation
parameters sent to the laser controller 701 the first time are the
wavelength (756 nm) and the number of irradiations (100
pulses).
[0187] Subsequently, in step S806, the controller 712 sends an
instruction to the laser controller 701 for starting the
irradiation of the laser beam. Consequently, pulsed light of 756 nm
is irradiated 100 times for irradiating the object 706 according to
the routine of step S210 to step S214 of FIG. 2. In step S212
midway during the routine, when it is determined that the light
intensity cannot be stabilized even when sufficient warming-up is
performed, in step S214, an error is notified from the laser
controller 701 to the controller 712.
[0188] In step S807, the controller 712 determines whether an error
was notified. When an error was not notified (S807=NO), the routine
proceeds to step S808. When an error was notified (S807=YES), the
routine proceeds to step S811.
[0189] In step S808, the receiving circuit 711 performs signal
processing such as amplification, A/D conversion and noise
reduction to the photoacoustic signals obtained as a result of the
probe receiving the photoacoustic waves 709 that are generated for
each irradiation of the pulsed light, and thereafter stores the
results in the internal memory.
[0190] In step S809, the controller 712 determines whether the
acquisition of the photoacoustic signals based on all designated
irradiation parameters is complete. When incomplete (S809=NO), the
routine returns to step S805, and the subsequent irradiation
parameters are designated to the laser controller 701. In this
embodiment, while the first irradiation was based on the wavelength
of 756 nm, since the irradiation based on the wavelength of 797 nm
has not yet been performed, the routine returns to step S805, and
the number of irradiations based on the wavelength of 797 nm is set
to 100 times. After the acquisition of the photoacoustic signal
based on both wavelengths of 756 nm and 797 nm, the routine
proceeds to step S810 (S809=YES).
[0191] In step S810, the controller 712 reads the photoacoustic
signal data stored in the memory, performs image processing such as
image reconfiguration processing and scan conversion processing,
displays the photoacoustic image on the display 714, and then ends
the processing. Here, it is also possible to display photoacoustic
images of a plurality of wavelengths next to each other according
to the user's instructions via the user interface 713, or estimate
the oxygen saturation of the blood hemoglobin based on the
difference in the light absorption distribution for each wavelength
and displaying the result.
[0192] Meanwhile, when an error was not detected by the laser
controller 701 during the warming-up and the laser light
irradiation, in step S811, an error message is displayed on the
display 714 for warning the user. Subsequently, in step S812, the
controller 712 sends an instruction to the laser controller 701,
and stops the laser power source 702, the PFN 703, the laser
optical system 704, and the temperature control system 705.
[0193] As described above, emission of the flash lamp is reduced
during the warming-up process and the photography standby process,
which take time, in the operational flow of the photoacoustic
apparatus in order to reduce the wear of the flash lamp. It is
thereby possible to reduce the frequency of replacing the flash
lamp, and provide a photoacoustic apparatus with low maintenance
cost and high availability.
[0194] As described above, according to the present invention, the
number of emissions of the flash lamp during the warming-up
operation can be minimized. It is thereby possible to reduce the
wear of the flash lamp and extend the life of the light source.
[0195] While the present invention has been described with
reference to exemplary embodiments, it is to be understood that the
invention is not limited to the disclosed exemplary embodiments.
The scope of the following claims is to be accorded the broadest
interpretation so as to encompass all such modifications and
equivalent structures and functions.
[0196] This application claims the benefit of Japanese Patent
Application No. 2013-133910, filed on Jun. 26, 2013, which is
hereby incorporated by reference herein in its entirety.
* * * * *