OPTICAL SCANNING OBSERVATION APPARATUS AND METHOD FOR ADJUSTING IRRADIATION PARAMETER OF PULSED LASER LIGHT

An optical scanning observation apparatus includes a laser light source driver configured to emit pulsed laser light of different wavelengths sequentially from a plurality of laser light sources, a scanning unit, a laser light detector, an image processor, and a controller configured to control the laser light source driver so that a detection signal obtained by irradiation of the pulsed laser light of one wavelength and outputted from the laser light detector does not have a detection signal generated by irradiation of the pulsed laser light of a different wavelength substantially mixed therein.

TECHNICAL FIELD

The present disclosure relates to an optical scanning observation apparatus for optically scanning an object and a method for adjusting an irradiation parameter of pulsed laser light.

BACKGROUND

An optical scanning observation apparatus that obtains a color image of an observation target using red (R), green (G), and blue (B) laser light sources is known. Spectroscopic methods include a continuous light method for using a mixed wave of RGB continuous output as irradiation light, splitting detected light with a spectral filter, and measuring with a plurality of detectors; a frame sequential method for switching the RGB irradiation every frame and detecting with one detector; and a pixel sequential method (time-division modulation method) for switching the RGB irradiation every pixel and detecting with one detector. For example, see patent literature (PTL) 1.

The frame sequential method and time-division modulation method do not require a spectroscope and detectors corresponding to each color and are therefore useful for reducing size and cutting costs. On the other hand, the time-division modulation method can acquire images of each RGB color within the same frame, yielding the advantage of no color flicker due to movement of the field of view, as occurs with the frame sequential method.

CITATION LIST

Patent Literature

SUMMARY

An optical scanning observation apparatus according to one aspect includes:

a laser light source driver configured to emit pulsed laser light of different wavelengths sequentially from a plurality of laser light sources:

a scanning unit configured to irradiate the pulsed laser light on an object to scan the object;

a laser light detector configured to sequentially detect light obtained from the object by sequential irradiation of the pulsed laser light;

an image processor configured to generate an image of the object based on a detection signal outputted from the laser light detector; and

a controller configured to control the laser light source driver so that a detection signal obtained by irradiation of the pulsed laser light of one wavelength and outputted from the laser light detector does not have a detection signal generated by irradiation of the pulsed laser light of a different wavelength substantially mixed therein.

In the optical scanning observation apparatus, the controller may be configured to adjust an irradiation parameter of the plurality of laser light sources through the laser light source driver.

In the optical scanning observation apparatus, the controller may be configured to judge, in an adjustment mode for adjusting the irradiation parameter, whether a detection signal outputted from the laser light detector during a predetermined sampling period falls within a predetermined range relative to the predetermined sampling period.

In the optical scanning observation apparatus, when the detection signal outputted from the laser light detector during the predetermined sampling period is outside of the predetermined range relative to the predetermined sampling period, the controller may be configured to change an irradiation parameter of each pulsed laser light of at least one wavelength so that the detection signal falls within the predetermined range.

In the optical scanning observation apparatus, the irradiation parameter may be at least one of an irradiation command timing or a pulse width.

A method for adjusting an irradiation parameter of pulsed laser light according to a first aspect includes:

driving a laser light source to emit pulsed laser light from the laser light source;

irradiating the pulsed laser light on an object to scan the object:

detecting light obtained from the object by irradiation of the pulsed laser light; and

adjusting an irradiation parameter of the pulsed laser light, when a detection signal obtained in the detecting during a predetermined sampling period is outside of a predetermined range relative to the predetermined sampling period, so that the detection signal falls within the predetermined range.

A method for adjusting an irradiation parameter of pulsed laser light according to a second aspect includes:

driving a plurality of laser light sources to emit pulsed laser light of different wavelengths sequentially from the plurality of laser light sources;

irradiating the pulsed laser light on an object to scan the object;

detecting light obtained from the object by sequential irradiation of the pulsed laser light; and

adjusting an irradiation parameter of each pulsed laser light of at least one wavelength, when a detection signal obtained in the detecting by irradiation of the pulsed laser light of one wavelength has mixed therein a detection signal generated by irradiation of the pulsed laser light of a different wavelength, to reduce mixing of the detection signals.

In the method for adjusting an irradiation parameter according to the second aspect, the irradiation parameter of each pulsed laser light of at least one wavelength may be adjusted when a detection signal obtained in the detecting during a predetermined sampling period is outside of a predetermined range relative to the predetermined sampling period.

In the method for adjusting an irradiation parameter according to the first or second aspect, the irradiation parameter may be at least one of an irradiation command timing or a pulse width.

DETAILED DESCRIPTION

In general, RGB laser light sources have different response characteristics. In greater detail, the length of time from the timing at which the laser light source receives an irradiation command (irradiation command timing) until the timing at which laser light is actually irradiated onto an object (actual irradiation timing) differs between the RGB laser light sources. InFIG. 15, the dashed RGB circles indicate virtual irradiation areas of RGB colored laser light if laser light of each color were irradiated onto an object simultaneously with the irradiation command timing, whereas the solid RGB circles indicate actual irradiation areas of RGB color laser light on an object. In the time-division modulation method, the actual irradiation areas of the RGB colors during a scan are shifted by relatively different amounts from the detection (sampling) area of the RGB pixels by the detector because of different response characteristics among the RGB laser light sources, as illustrated inFIG. 15. This causes color leaking, in which the actual irradiation area of one color spreads into a plurality of adjacent pixel sampling areas, leading to reduced image quality.

Embodiments are described below with reference to the drawings.

First Embodiment

First, with reference toFIGS. 1 to 4B, a first embodiment of an optical scanning observation apparatus according to the present disclosure is described.FIG. 1is a block diagram schematically illustrating the configuration of an optical scanning observation apparatus according to the first embodiment. InFIG. 1, an optical scanning observation apparatus10is configured as an optical scanning endoscope apparatus and includes a scope20, a control device body30, and a display40.

First, the configuration of the control device body30is described. The control device body30includes a memory39, a controller31that controls the optical scanning observation apparatus10overall, a laser light source driver32, laser light sources33R,33G33B (also collectively referred to hereinafter as “laser light source33”), a combiner34, a drive controller38, an optical detector35, an analog-digital converter (ADC)36, and an image processor37.

The light sources33R.33Q33B emit pulsed laser light of R, G and B wavelengths (hereinafter also simply “colors”) in accordance with the control signal (irradiation command) from the laser light source driver32. For example, diode-pumped solid-state (DPSS) lasers or laser diodes may be used as the laser light sources33R,33G,33B.

The memory39holds an irradiation parameter table50, such as the one in Table 1 below, storing an irradiation parameter (an irradiation timing t in this example) of pulsed laser light for each wavelength (R, G, B) of pulsed laser light from the laser light sources33R,33G,33B.

The irradiation timings tR, tG, tBof the colors R, G, B are parameters stipulating the irradiation command timing of each color (the timing at which the laser light sources33R,33G,33B receive the irradiation command from the laser light source driver32). In this example, the irradiation timings tR, tG, tBof the colors indicate the amount of time by which to speed up or delay the initial value of the irradiation command timing of each color (i.e. a time shift for the initial value of the irradiation command timing) and are set by performing, in advance, a method for adjusting an irradiation parameter of pulsed laser light (hereinafter also simply “method for adjusting an irradiation parameter”) using the optical scanning observation apparatus10, as described below. In this example, the initial value of the irradiation command timing of each color is set to the irradiation command timing of each color for the case of irradiating pulsed laser light at constant time intervals (irradiation period) TEin a predetermined irradiation order (in the order R, G, B).

The method for adjusting an irradiation parameter is used at a time other than a regular scan for observing an object100, such as when shipping the produced optical scanning observation apparatus10, at the time of maintenance, or immediately before a scan. For the sake of convenience, the mode of the optical scanning observation apparatus10when performing the method for adjusting an irradiation parameter is referred to as “adjustment mode”, and the mode of the optical scanning observation apparatus10when performing a normal scan for observing the object100is referred to as “scanning mode”.

The irradiation parameter may, for example, be adjusted manually in the optical scanning observation apparatus10only at the time of product shipment, in which case the system of the shipped optical scanning observation apparatus10need not include the “adjustment mode”.

By controlling the laser light source driver32using the set irradiation command timings, the controller31can perform control so that a detection signal obtained by irradiation of pulsed laser light of one of the wavelengths of R, G, or B and outputted from the optical detector35does not have a detection signal generated by irradiation of pulsed laser light of a different wavelength substantially mixed therein, as described below. Here, “not substantially mixed therein” refers to the signal of detected laser light of another wavelength being less than 5%.

The laser light source driver32sequentially emits R, G, B pulsed laser light from the laser light sources33R,33G,33B in accordance with the control signal from the controller31. During one scan, the laser light source driver32repeatedly switches between the wavelengths of R, G, B light from the laser light source33in a predetermined irradiation order (such as the order R, G B) in accordance with the irradiation command timing of each color.

As used here, “one scan” refers to one scan, in order to capture one image (one frame), from the starting point to the ending point of a predetermined scan path, such as a spiral.

The pulsed laser light emitted from the laser light sources33R,33G33B passes through optical paths joined coaxially by the combiner34and is incident as illumination light on a light-transmission fiber11, which is a single-mode fiber.

The combiner34may, for example, be configured using a fiber multiplexer, a dichroic prism, or the like.

The laser light sources33R,33G,33B and the combiner34may be stored in a housing that is separate from the control device body30and is joined to the control device body30by a signal wire.

Pulsed laser light incident on the light-transmission fiber11(scanning unit) from the combiner34is guided to the tip of the scope20and irradiated onto an object100. At this time, by driving the actuator21(scanning unit) of the scope20by vibration, the drive controller38of the control device body30drives the tip of the light-transmission fiber11by vibration. As a result, the illumination light (pulsed laser light) emitted from the light-transmission fiber11scans the observation surface of the object100in2D over a predetermined scan path. Light such as reflected light or scattered light that is obtained from the object100due to sequential irradiation with the pulsed laser light is received at the tip of a light-receiving fiber12, which is constituted by a multi-mode fiber, and is guided through the scope20to the control device body30.

In this example, the light-transmission fiber11and the actuator21constitute a scanning unit that irradiates pulsed laser light from the laser light source33onto the object100to scan the object100.

Through the light-receiving fiber12, the optical detector35(laser light detector) sequentially detects (samples) light obtained from the object100by sequential irradiation of R, G, B pulsed laser light and outputs an analog detection signal every irradiation period TEof pulsed laser light.

The period for the optical detector35to sample R, G B light obtained from the object100is referred to below as the “sampling period”. The time length of the sampling period in scanning mode is set to be the same as the irradiation period TE. As described below, the sampling period in adjustment mode is set when performing the method for adjusting an irradiation parameter.

The ADC36converts the analog detection signal from the optical detector35to a digital detection signal and outputs the result to the image processor37.

In the first embodiment, the detection signal outputted from the optical detector35via the ADC36is accumulated in any storage device (such as the memory39of the control device body30or a non-illustrated external storage device).

The image processor37stores the detection signal, sequentially input from the ADC36, corresponding to each wavelength sequentially in any storage apparatus (not illustrated) in association with the respective irradiation command timings and scanning positions. Information on the irradiation command timing and scanning position is obtained from the controller31. The controller31calculates information on the scanning position along the scan path from information such as the amplitude and phase of vibration voltage applied by the drive controller38. Instead of calculating the information on the scanning position, the controller31may store therein, in advance, a table stipulating the relationship between the scanning time and the scanning position in correspondence with predetermined scanning conditions. The controller31may then read information on the scanning position from the table and transmit the information to the image processor37.

In this example, the scanning position information of each color can be applied as is even when the irradiation command timing of each color is adjusted (corrected).

After completion of scanning or during scanning, the image processor37generates an image signal after performing image processing as necessary, such as enhancement, γ processing, and interpolation, based on each detection signal input from the ADC36and displays an image of the object100on the display40.

Next, the configuration of the scope20is described.FIG. 2is a schematic overview of the scope20. The scope20includes an operation part22and an insertion part23. The light-transmission fiber11, the light-receiving fiber12, and wiring cables13that extend from the control device body30are each connected to the operation part22. The light-transmission fiber11, light-receiving fiber12, and wiring cables13pass through the insertion part23and extend to a tip24(the portion within the dashed line inFIG. 2) of the insertion part23.

FIG. 3is a cross-sectional view illustrating an enlargement of the tip24of the insertion part23in the scope20inFIG. 2. The tip24of the insertion part23of the scope20includes the actuator21, projection lenses25aand25b, the light-transmission fiber11that passes through the central portion, and a plurality of light-receiving fibers12that pass through the peripheral portion.

The actuator21drives a tip11cof the light-transmission fiber11by vibration. The actuator21includes a fiber holding member29fixed to the inside of the insertion part23of the scope20by an attachment ring26and piezoelectric elements28ato28d(seeFIGS. 4A and 4B). The light-transmission fiber11is supported by the fiber holding member29, and the portion of the light-transmission fiber11from a fixed end11asupported by the fiber holding member29to the tip11cis an oscillating part11bthat is supported to allow oscillation. The light-receiving fiber12is disposed to pass through the peripheral portion of the insertion part23and extends to the end of the tip24. A non-illustrated detection lens is also provided at the tip of each fiber in the light-receiving fiber12.

Furthermore, the projection lenses25aand25band the detection lenses are disposed at the extreme end of the tip24of the insertion part23in the scope20. The projection lenses25aand25bare configured so that laser light emitted from the tip11cof the light-transmission fiber11is irradiated on the object100and substantially concentrated. The detection lenses are disposed so as to capture light that is reflected, scattered, or the like by the object100due to laser light concentrated on the object100, and to concentrate and combine the captured light on the light-receiving fiber12disposed behind the detection lenses. The projection lenses are not limited to a double lens structure and may be structured as a single lens or as three or more lenses.

FIG. 4Aillustrates the vibration driving mechanism of the actuator21of the optical scanning observation apparatus10and illustrates the oscillating part11bof the light-transmission fiber11.FIG. 4Bis a cross-sectional view along the A-A line inFIG. 4A. The light-transmission fiber11passes through the center of the fiber holding member29, which is shaped as a quadratic prism, and is fixed and held by the fiber holding member29. The four sides of the fiber holding member29respectively face the ±Y direction and the ±X direction. A pair of piezoelectric elements28aand28cfor driving in the Y direction are fixed onto the sides of the fiber holding member29in the +Y direction, and a pair of piezoelectric elements28band28dfor driving in the X direction are fixed onto the sides in the ±X direction.

The wiring cables13from the drive controller38of the control device body30are connected to the piezoelectric elements28ato28d, which are driven by application of voltage by the drive controller38.

Voltage of equivalent magnitude and opposite polarity is always applied across the piezoelectric elements28band28din the X direction. Similarly, voltage of equivalent magnitude and opposite polarity is always applied across the piezoelectric elements28aand28cin the Y direction. One of the piezoelectric elements28band28ddisposed opposite each other with the fiber holding member29therebetween expands and the other contracts, causing the fiber holding member29to flex. Repeating this operation produces vibration in the X direction. The same is true for vibration in the Y direction as well.

The drive controller38can perform vibration driving of the piezoelectric elements28band28dfor driving in the X direction and the piezoelectric elements28aand28cfor driving in the Y direction by applying vibration voltage of the same frequency or vibration voltage of different frequencies thereto. Upon vibration driving of the piezoelectric elements28aand28cfor driving in the Y direction and the piezoelectric elements28band28dfor driving in the X direction, the oscillating part11bof the light-transmission fiber11illustrated inFIGS. 3, 4A, and 4Bvibrates, and the tip11cis deflected. Hence, the pulsed laser light emitted from the tip11csequentially scans the surface of the object100over a predetermined scan path.

Next, the first embodiment of the disclosed method for adjusting an irradiation parameter of pulsed laser light is described with reference toFIGS. 5 and 6. InFIG. 5, the dashed R circle indicates a virtual irradiation area of R laser light if R laser light were irradiated simultaneously with the R irradiation command timing, whereas the solid R circle indicates the actual irradiation area of R laser light on an object. As described above, the irradiation parameter t of pulsed laser light from the laser light sources33R,33G,33B (in this example, irradiation timings tR, tG, tB) is adjusted by performing the method for adjusting an irradiation parameter of pulsed laser light using the optical scanning observation apparatus10in adjustment mode.

In the first embodiment, pulsed laser light of one color among R, G B is emitted while scanning over a predetermined scan path, the occurrence of color leaking is detected during each R, G B sampling period, and the irradiation parameter of the color is adjusted if color leaking has occurred. This process is repeated for the three colors. Any object may be used as the object100, such as a white board.

First, the R, G, B sampling periods in adjustment mode are set to be the same as the sampling periods used in scanning mode to acquire an image of R, G, B pixels (step S11). The “sampling period” in the present disclosure is determined by the sampling frequency and timing.

As illustrated inFIGS. 5 and 6, the laser light source driver32outputs an irradiation command to the laser light source33R upon reaching the R irradiation command timing during a scan, thereby causing R pulsed laser light to be emitted (step S12, laser light source driving step). The pulsed laser light from the laser light source33R is irradiated onto the object100and scanned over the object100(scanning step) by the light-transmission fiber11and the actuator21(scanning unit). Light obtained from the object100is detected by the optical detector35in the sampling period TRfor the R pixel and in the subsequent sampling periods TG, TBof the G pixel and the B pixel (optical detection step).

Next, it is judged whether the detection signals outputted from the ADC36in the sampling periods TR, TG, TBare within predetermined ranges for the sampling periods TR, TG, TB(step S13). The actual irradiation area (solid circle) of the R pixel is ideally contained within the R sampling area (scan area). If at least a portion of the actual R irradiation area is present in the sampling area of another color (G, B), then R color leaking has occurred. Therefore, the detection signal is preferably as high as possible in the R sampling period TRand preferably as low as possible in the G, B sampling periods TG, TB. From this perspective, in the example inFIG. 6, the predetermined range of the R sampling period TRis a range of a predetermined value SRor greater, and the predetermined ranges of the G, B sampling periods TG, TBare ranges of predetermined values SG, SBor less.

For example, the threshold (predetermined value SR) of the aforementioned predetermined range of the R sampling period TRmay be 90% of the R peak amount of light, and the thresholds (predetermined values SG, SB) of the aforementioned predetermined ranges of the G, B sampling periods TG, TBmay each be 5% of the R peak amount of light. The R peak amount of light can, for example, be acquired by changing the R irradiation parameter in all steps.

When at least one of the detection signals in the sampling periods TR, TG, TBis outside of the aforementioned predetermined ranges (S13: No), then the R irradiation timing tRis changed (step S14), and the changed irradiation timing tRis stored in the irradiation parameter table50of the memory39. The R irradiation timing tRis further adjusted by subsequently repeating steps S12to S14until all of the detection signals in the sampling periods TR, TG, TBrespectively fall within the aforementioned predetermined ranges (adjustment step). The irradiation timing tRis preferably changed in step S14taking into consideration the detection signal in the sampling period TRin the preceding step S13.

On the other hand, when all of the detection signals in the sampling periods TR, TG, TBrespectively fall within the aforementioned predetermined ranges in step S13(S13: Yes), the process proceeds to step S15, and a similar process as for R in steps S12to S14is performed for G. Specifically, the laser light source driver32outputs an irradiation command to the laser light source33G upon reaching the G irradiation command timing, thereby causing G pulsed laser light to be emitted (step S15). Subsequently, light obtained from the object100is detected by the optical detector35in the G sampling period TGand in the subsequent B, R sampling periods TB, TR. When at least one of the detection signals outputted from the optical detector35through the ADC36in the sampling periods TR, TG, TBis outside of predetermined ranges for the sampling periods TR, TG, TB(S16: No), then the G irradiation timing tGis changed (step S17). The G irradiation timing tGis further adjusted by subsequently repeating steps S15to S17until all of the detection signals in the sampling periods TR, TG, TBrespectively fall within the aforementioned predetermined ranges. Here, as in the case of R, the detection signal is preferably as high as possible in the G sampling period TGand preferably as low as possible in the B, R sampling periods TB, TR. Hence, in the example inFIG. 6, the predetermined range of the G sampling period TGis a range of a predetermined value SGor greater, and the predetermined ranges of the B, R sampling periods TB, TRare ranges of predetermined values SB, SRor less.

For example, the threshold (predetermined value SG) of the aforementioned predetermined range of the G sampling period TGmay be 90% of the G peak amount of light, and the thresholds (predetermined values SB, SR) of the aforementioned predetermined ranges of the B, R sampling periods TB, TRmay each be 5% of the G peak amount of light. The G peak amount of light can, for example, be acquired by changing the G irradiation parameter in all steps.

Subsequently, a similar process as for R and G is performed for B (steps S18to S20).

Adjustment of the irradiation parameter (irradiation timings tR, tG, tB) of each color R, G, B is completed by the above process.

FIGS. 7 and 8represent the performance of the optical scanning observation apparatus10in scanning mode after adjustment of the irradiation parameters. In the time chart inFIG. 7, the “control signal (R)”, “control signal (G)”, and “control signal (B)” respectively indicate the timings at which an irradiation command (control signal) is outputted from the laser light source driver32to the R, G B laser light sources33R,33G33B, and the “detection signal” indicates the detection signal outputted from the optical detector35in the sampling period in scanning mode. In the outline inFIG. 8, the dashed circles indicate virtual irradiation areas at the irradiation command timings, whereas the solid circles indicate the actual irradiation areas.

In this example, the responsiveness of the G laser light source33G is the slowest and the responsiveness of the B laser light source33B is the fastest among the laser light sources33R,33G,33B. Accordingly, the G irradiation command timing is set earlier than the initial value by the irradiation timing tG, and the B irradiation command timing is set later than the initial value by the irradiation timing tB(tG>tR>tB, and tR=0).

Consequently, the actual R, G, B irradiation areas (solid circles inFIG. 8) do not overlap and are contained within the respective color sampling areas, as illustrated inFIG. 8. Furthermore, the value of the detection signals generated by irradiation of R, G, B pulsed laser light are nearly uniform, as illustrated inFIG. 7. The detection signal obtained by irradiation of pulsed laser light of one wavelength is therefore prevented from having a detection signal generated by irradiation of pulsed laser light of a different wavelength substantially mixed therein, and color leaking is reduced. Image quality thus improves.

Second Embodiment

Next, a second embodiment of the disclosed method for adjusting an irradiation parameter of pulsed laser light is described with reference toFIGS. 9 and 10, focusing on the differences from the first embodiment. The optical scanning observation apparatus10described above with reference toFIGS. 1 to 4Bis used in the below-described second embodiment of a method for adjusting an irradiation parameter.

In the second embodiment of a method for adjusting an irradiation parameter, R, G, B pulsed laser light is emitted sequentially while scanning along a predetermined scan path. When a detection signal obtained by irradiation of pulsed laser light of one wavelength has a detection signal generated by irradiation of pulsed laser light of another wavelength mixed therein, an irradiation parameter of each pulsed laser light of at least one wavelength is adjusted to reduce the mixing of detection signals.

First, the R, G, B sampling frequencies in this adjustment mode are set to be twice the sampling frequencies used in the scanning mode. Furthermore, periods TR1, TG1, TB1corresponding to the central half of a pixel in each of the R, G, B pixel sampling periods in the scanning mode and periods TR2, TG2, TB2corresponding to half of a pixel and spreading into the sampling periods of adjacent pixels of two colors in the scanning mode are alternately set (step S31).

As illustrated inFIGS. 9 and 10, the laser light source driver32sequentially outputs irradiation commands to the laser light sources33R,33G,33B during a scan on the basis of the irradiation parameter t (irradiation timings tR, tG, tB) stored in the irradiation parameter table50in the memory39to cause R, G, B pulsed laser light to be emitted sequentially (step S32, laser light source driving step). Step S32is performed continuously while the following steps S33to S38are performed. The pulsed laser light from the laser light source33is irradiated onto the object100and scanned over the object100(scanning step) by the light-transmission fiber11and the actuator21(scanning unit). Light obtained from the object100is detected by the optical detector35in the sampling periods TR1, TR2, TG1, TG2, TB1, TB2(optical detection step). The detection signals outputted from the optical detector35in the sampling periods TR1, TR2, TG1, TG2, TB1, TB2are converted from analog to digital by the ADC36.

Next, it is judged whether the detection signals in the sampling period TR1corresponding to the central half of the R pixel and in the following sampling period TR2spreading into the R pixel and the G pixel are both within respective predetermined ranges for the sampling periods TR1, TR2(step S33). Ideally, the central portion in the scanning direction of the R irradiation area (the peak portion in the laser waveform) is the central portion in the scanning direction of the area of the sampling period TR1, and the overlap between the R and G irradiation areas in the area of the sampling period TR2spreading over the edges in the scanning direction of the R, G irradiation areas (the valley portion in the laser waveform) is preferably as small as possible. Color leaking occurs if the center in the scanning direction of the R irradiation area deviates from the center in the scanning direction of the area of the sampling period TR1. Consequently, overlap between the R irradiation area and the irradiation area of another color (G, B) causes detection signals generated by irradiation of pulsed laser light of a plurality of colors to mix. Therefore, the detection signal is preferably relatively high in the sampling period TR1and preferably relatively low in the sampling period TR2. From this perspective, in the example inFIG. 10, the predetermined range of the sampling period TR1is a range of a predetermined value SR1or greater, and the predetermined range of the sampling period TR2is a range of a predetermined value SR2or less.

For example, the threshold (predetermined value SR1) of the aforementioned predetermined range of the sampling period TR1may be 90% of the peak amount of light, and the threshold (predetermined value SR2) of the aforementioned predetermined range of the sampling period TR2may be 10% of the peak amount of light.

When at least one of the detection signals in the sampling periods TR1, TR2is outside of the aforementioned predetermined ranges (S33: No), then the R irradiation timing tRis changed (step S34), and the changed irradiation timing tRis stored in the irradiation parameter table50of the memory39. The R irradiation timing tRis further adjusted by subsequently repeating steps S33to S34until both of the detection signals in the sampling periods TR1, TR2respectively fall within the aforementioned predetermined ranges (adjustment step).

On the other hand, when both of the detection signals in the sampling periods TR1, TR2respectively fall within the aforementioned predetermined ranges in step S33(S33: Yes), the process proceeds to step S35, and a similar process as for R in steps S33to S34is performed for G. Specifically, it is judged whether the detection signals in the sampling period TG1corresponding to the central half of the G pixel and in the following sampling period TG2spreading into the G pixel and the B pixel are both within respective predetermined ranges for the sampling periods TG1, TG2(step S35). Here, as in the case of R, the detection signal is preferably relatively high in the sampling period TG1and preferably relatively low in the sampling period TG2. Hence, in the example inFIG. 10, the predetermined range of the sampling period TG1is a range of a predetermined value SG1or greater, and the predetermined range of the sampling period TG2is a range of a predetermined value SG2or less.

For example, the threshold (predetermined value SG1) of the aforementioned predetermined range of the sampling period TG1may be 90% of the peak amount of light, and the threshold (predetermined value SG2) of the aforementioned predetermined range of the sampling period TG2may be 10% of the peak amount of light.

When at least one of the detection signals in the sampling periods TG1, TG2is outside of the aforementioned predetermined ranges (S35: No), then the G irradiation timing to is changed (step S36), and the changed irradiation timing tGis stored in the irradiation parameter table50of the memory39. The G irradiation timing tGis further adjusted by subsequently repeating steps S35to S36until both of the detection signals in the sampling periods TG1, TG2respectively fall within the aforementioned predetermined ranges (adjustment step).

Subsequently, a similar process as for R and G is performed for B (steps S37to S38).

Adjustment of the irradiation parameter t (irradiation timings tR, to, tB) of each color R, G, B is completed by the above process.

According to the second embodiment, the detection signals obtained in the periods TR1, TG1, TB1corresponding to the central half of a pixel can be increased above a predetermined value, and the detection signals obtained in the periods TR2, TG2, TB2corresponding to half of a pixel and spreading into two sampling periods can be reduced below a predetermined value, thereby reducing overlap between adjacent irradiation areas of wavelengths of light. This reduces color leaking and improves image quality.

Third Embodiment

Next, a third embodiment of the disclosed method for adjusting an irradiation parameter of pulsed laser light is described with reference toFIGS. 11 and 12, focusing on the differences from the first embodiment. The optical scanning observation apparatus10described above with reference toFIGS. 1 to 4Bis used in the below-described third embodiment of a method for adjusting an irradiation parameter.

In the third embodiment of a method for adjusting an irradiation parameter, as in the second embodiment, R, G, B pulsed laser light is emitted sequentially while scanning along a predetermined scan path. When a detection signal obtained by irradiation of pulsed laser light of one wavelength has a detection signal generated by irradiation of pulsed laser light of another wavelength mixed therein, an irradiation parameter of each pulsed laser light of at least one wavelength is adjusted to reduce the mixing of detection signals.

First, the R, G, B sampling periods in adjustment mode (and therefore the frequency and timing) are set to be the same as the sampling periods used in scanning mode (step S51).

As illustrated inFIGS. 11 and 12, the laser light source driver32sequentially outputs irradiation commands to the laser light sources33R,33G,33B during a scan on the basis of the irradiation parameter t (irradiation timings tR, tG, tB) stored in the irradiation parameter table50in the memory39to cause R, G, B pulsed laser light to be emitted sequentially (step S52, laser light source driving step). Step S52is performed continuously while the following steps S53to S65are performed. The pulsed laser light from the laser light source33is irradiated onto the object100and scanned over the object100(scanning step) by the light-transmission fiber11and the actuator21(scanning unit). Light obtained from the object100is detected by the optical detector35in the sampling periods TR1, TG1, TB1(optical detection step). The detection signals outputted from the optical detector35in the sampling periods TR1, TG1, TB1are converted from analog to digital by the ADC36.

Next, it is judged whether the detection signal in the R sampling period TR1is within a predetermined range for the sampling period TR1(step S53). The actual R irradiation area (solid circle) is ideally contained within the sampling area (scan area) of the R pixel. Accordingly, the detection signal is preferably relatively high in the sampling period TR1. From this perspective, in the example inFIG. 12, the predetermined range of the sampling period TR1is a range of a predetermined value SR1or greater.

For example, the threshold (predetermined value SR1) of the aforementioned predetermined range of the sampling period TR1may be 90% of the peak amount of light.

When the detection signal in the sampling period TR1is outside of the aforementioned predetermined range (S53: No), then the R irradiation timing tRis changed (step S54), and the changed irradiation timing tRis stored in the irradiation parameter table50of the memory39. The R irradiation timing tRis further adjusted by subsequently repeating steps S53to S54until the detection signal in the sampling period TR1falls within the predetermined range of the sampling period TR1(adjustment step).

On the other hand, when the detection signal in the sampling period TR1falls within the aforementioned predetermined range in step S53(S53: Yes), the process proceeds to step S55, and a similar process as for R in steps S53to S54is performed for G (steps S55to S56).

Subsequently, a similar process as for R and G is performed for B (steps S57to S58).

Next, the R, G, B sampling periods in adjustment mode are moved (in this example, delayed) by half a pixel from the sampling periods in scanning mode (step S59). It is then judged whether the detection signal in the R sampling period TR2is within a predetermined range for the sampling period TR2(step S60). Ideally, the overlap between R and G irradiation areas is as small as possible in the area of the sampling period TR2that spreads into the R and G irradiation areas. Accordingly, the detection signal is preferably relatively low in the sampling period TR2. From this perspective, in the example inFIG. 12, the predetermined range of the sampling period TR2is a range of a predetermined value SR2or less.

For example, the threshold (predetermined value SR2) of the aforementioned predetermined range of the sampling period TR2may be 10% of the peak amount of light.

When the detection signal in the sampling period TR2is outside of the aforementioned predetermined range (S60: No), then the R irradiation timing tRis changed (step S61), and the changed irradiation timing tRis stored in the irradiation parameter table50of the memory39. The R irradiation timing tRis further adjusted by subsequently repeating steps S60to S61until the detection signal in the sampling period TR2falls within the aforementioned predetermined range of the sampling period TR2(adjustment step).

On the other hand, when the detection signal in the sampling period TR2falls within the aforementioned predetermined range in step S60(S60: Yes), the process proceeds to step S62, and a similar process as for R in steps S60to S61is performed for G (steps S62to S63).

Subsequently, a similar process as for R and G is performed for B (steps S64to S65).

Adjustment of the irradiation parameter t (tR, tG, tB) of each color R, G, B is completed by the above process.

In addition to the effects of the second embodiment, the third embodiment makes it unnecessary to change the substrate of the control device body30, which could be necessary in the second embodiment when setting the sampling frequency in adjustment mode to twice the sampling frequency in scanning mode.

This disclosure is not limited to the above-described embodiments, and a variety of modifications may be made.

In the above-described examples, the irradiation parameter t may include the pulse width of the R, G, B pulsed laser light in addition to, or instead of, the irradiation timing of the R, G, B pulsed laser light.

In each of the above-described examples, a portion or all of the steps in the method for adjusting an irradiation parameter may be performed in response to human operation of the optical scanning observation apparatus10or may be programmed and performed automatically by the optical scanning observation apparatus10.

FIG. 13illustrates an optical scanning observation apparatus10configured to allow execution of a program that includes a portion or all of the steps of the method for adjusting an irradiation parameter. The optical scanning observation apparatus10inFIG. 13differs from the optical scanning observation apparatus10inFIG. 1in that the controller31includes an irradiation parameter adjuster52. The irradiation parameter adjuster52adjusts the irradiation parameter by executing the aforementioned program stored in a storage device, such as the memory39, and stores the adjusted irradiation parameter in the irradiation parameter table50within the memory39.

The actuator21of the light-transmission fiber11is not limited to use of piezoelectric elements. For example, a permanent magnet fixed to the light-transmission fiber11and coils for generation of a deflecting magnetic field (magnet coils) that drive the permanent magnet may be used instead. The following describes a modification to the actuator21with reference toFIGS. 14A to 14C.FIG. 14Ais a cross-sectional view of the tip24of the scope20,FIG. 14Bis an enlarged perspective view of the actuator21inFIG. 14A, andFIG. 14Cis a cross-sectional view along a plane perpendicular to the axis of the light-transmission fiber11, illustrating a portion including the coils62ato62dfor generation of a deflecting magnetic field and the permanent magnet63inFIG. 14B.

At a portion of the oscillating part11bof the light-transmission fiber11, the permanent magnet63, which is magnetized in the axial direction of the light-transmission fiber11and includes a through-hole, is joined to the light-transmission fiber11by the light-transmission fiber11being passed through the through-hole. A square tube61, one end of which is fixed to the attachment ring26, is provided so as to surround the oscillating part11b, and flat coils62ato62dfor generation of a deflecting magnetic field are provided on the sides of the square tube61at a portion thereof opposing one pole of the permanent magnet63.

The pair of coils62aand62cfor generation of a deflecting magnetic field in the Y direction and the pair of coils62band62dfor generation of a deflecting magnetic field in the X direction are each disposed on opposing sides of the square tube61, and a line connecting the center of the coil62afor generation of a deflecting magnetic field with the center of the coil62cfor generation of a deflecting magnetic field is orthogonal to a line connecting the center of the coil62bfor generation of a deflecting magnetic field with the center of the coil62dfor generation of a deflecting magnetic field near the central axis of the square tube61when the light-transmission fiber11is disposed therein at rest. These coils are connected to the drive controller38of the control device body30via the wiring cables13and are driven by drive current from the drive controller38.

Furthermore, the scanning unit is not limited to oscillating the tip of an optical fiber. For example, an optical scanning element such as a MEMS mirror may be disposed along the optical path from the laser light source33to the object.

The optical scanning observation apparatus of the present disclosure may also be configured as an optical scanning microscope.