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1> JSTQE-CON-BP2019-07475-2018 <Application of scan-less two-dimensional
confocal microscopy based on a combinationof confocal slit with wavelength/spaceconversion
Eiji Hase, Takeo Minamikawa, Shuji Miyamoto, Yasuhiro Mizutani, Tetsuo Iwata,
Hirotsugu Yamamoto, and Takeshi Yasui
Abstract—Confocal laser microscope (CLM) has been widelyused in the fields of the non-contact surface topography,
biomedical imaging, and other applications, because theconfocality gives two-dimensional (2D) optical-sectioning or threedimensional (3D) imaging capability with the depth selectivity.
Combination of line-focused CLM with one-dimensional (1D)
spectral encoding CLM enables us to obtain the 2D confocal image
without the need for the mechanical scanning. So-called scan-less
2D CLM is a unique imaging modality, however, there are no
attempts to apply for practical application. In this paper, weconstructed scan-less 2D CLM with the image acquisition time of
0.23 ms, the lateral resolution of 1.2 µm, the depth resolution of 2.4µm, and apply it for different kinds of application to evaluate its
practical potential.
Index Terms—Biomedical imaging, Microscopy.

I. INTRODUCTIONCONFOCAL laser microscopy (CLM) [1] has been widelyused in the field of biomedical imaging, non-contact
surface topography, and other applications thanks to thebenefit of the noninvasiveness, the optical sectioning capability,
and the stray light elimination. Usual CLMs are based on apoint-scanning measurement. This is because a pinhole for apoint light-source, a focal point of the objective lens, and apinhole before a detector must have a conjugate relationship toeach other. Therefore, a two-dimensional (2D) image has to beacquired by a mechanical scanning of the focal point while
maintaining the conjugate configuration. The mechanicalscanning by a galvanometer mirror, polygon mirror, or MEMS
(Micro Electro Mechanical System) mirror leads to the image
acquisition rate of several to a few tens frames per seconds (fps)[2, 3, 4]. The combination of a Nipkow disk with a micro-lensarray boosts the image acquisition rate up to 1000 fps [5,6].
However, these mechanical scanning systems are susceptible to
E. Hase and S. Miyamoto were with the Graduate school of Advanced
Technology and Science, Tokushima University, Tokushima 770-8506, Japan(email: hase@spring8.or.jp; shuujimiyamoto@gmail.com). T. Minamikawa, T.
Iwata, and T. Yasui are with the Graduate school of Technology, Industrial andSocial Sciences, Tokushima University, Tokushima 770-8506, Japan (email:minamikawa.takeo@tokushima-u.ac.jp;
iwata@tokushima-u.ac.jp;
yasui.takeshi@tokushima-u.ac.jp). Y. Mizutani is with the Graduate School ofenvironmental disturbances, such as mechanical or acoustic
vibration. Requirement for the stable experimental condition,such as an optical table, often limit the application of CLM
inside the lab. To widely expand its application fields outside
the lab, the mechanical scanning must be omitted from CLM.
Line-field CLM [7] is a one interesting approach toeliminate the one-dimensional (1D) mechanical scanning. In
this method, the laser beam is focused on a sample as a line
beam, and the line beam reflected from a sample passes througha confocal slit before the detection. This slit gives theconfocality for the whole line image, and then the reflected lightis captured as the confocal 1D image in real time by a 1D
imaging sensor (line sensor). However, this approach still needs
additional mechanical scanning of the line beam across the line
illumination. Another interesting approach is the use of 1D
spectral encoding (1D-SE) CLM [8,9]. In 1D-SE CLM, arainbow line beam is formed by a combination of a broadbandspectral light and a diffraction grating, and then are irradiatedon the sample as the line beam of the rainbow spectrum. This
result in an encoding of 1D image information onto the rainbow
spectrum. Finally, the 1D image is decoded from the spectrum
acquired by a multi-channel spectrometer without themechanical scanning. However, as well as the line-field CLM,
additional 1D mechanical scanning needs to acquire the 2D
image.
If the line-field CLM and the 1D-SE CLM are orthogonallycombined, 1D image information of each coordinates areindividually and orthogonally developed in the 2D plane. By
using the multi-channel spectrometer equipped with the 2D
imaging sensor, the confocal 2D image can be decoded from aspectral line image, composed of 1D spatial dimension and 1D
spectral dimension, without the need for any mechanicalscanning. The image acquisition rate of this approach is limited
by not the mechanical scanning but the frame rate of the 2D

Engineering, Osaka University, Osaka 565-0871, Japan. (email:mizutani@mech.eng.osaka-u.ac.jp). H. Yamamoto is with the Center for
Optical Research and Education, Utsunomiya University, Tochigi 321-8585,
Japan (email: yamamoto@opt.utsunomiya-u.ac.jp). All authors are with JST,
ERATO, MINOSHIMA Intelligent Optical Synthesizer Project, 2-1,
Tokushima 770-8506, Japan. (Corresponding author: Takeshi Yasui)

> JSTQE-CON-BP2019-07475-2018 <imaging sensor, which is achieved up to Mfps in the state-of-art
complementary metal oxide semiconductor (CMOS) camera.
Such scan-less 2D CLM has a high potential as CLM due tothe fast image acquisition rate and the high robustness to theenvironmental disturbances [10]. However, its potential ofconfocal 3D or volume imaging has not been fully investigatedfrom the viewpoint of practical applications. In this paper, we
expand the scan-less 2D CLM into confocal 3D imaging byhelp of a piezoelectric-transducer (PZT) scanner for objective
lens, and then apply it for three applications, namely biomedical
imaging of tissue specimen, plant monitoring, and nondestructive inspection of electronic board.
II. PRINCIPLE
Figure 1 shows a principle of operation for the scan-less 2D
CLM based on a combination of line-field CLM with 1D-SE
CLM. In this figure, while the optical axis is defined as a Z
coordinate, the horizontal and vertical directions in the 2D
plane normal to the optical axis are respectively corresponding
to X and Y coordinates. The X and Y coordinates are used foreach 1D imaging by 1D-SE and line-field CLMs, respectively.
The circular beam shape of a broadband-spectral laser light isconverted into a line shape along the Y coordinate by the beamshaping optics, composed of a cylindrical lens and a lens. The
wavelength disperser disperses each wavelength component at
different angle along the X coordinate depending on the
wavelength. This results in a formation of “vertical rainbow"
composed of the same wavelength component along the Y
coordinate and the different wavelength components along the
X coordinate. After passing thorough an objective lens, thedemagnified vertical rainbow is illuminated on a sample. This
enables to encode the 2D information of the sample on thevertical rainbow at one-shot.
The back-reflected vertical rainbow from the sample
inversely propagates the same optical components, and eachwavelength component is spatially overlapped again. The
resulting line-shape beam passes through a confocal slit for theconfocality of the 1D image along the Y coordinate. Then, thespectral line image, or the spatio-spectral image, is measured as
an image with the wavelength dimension along the X coordinate
and the spatial dimension along the Y coordinate by a multichannel spectrometer equipped with a 2D imaging sensor. Since
this spatio-spectral image is corresponding to the demagnified
vertical rainbow on the sample, the confocal 2D image of theFig. 1. Principle of operation of the proposed method.

2
sample can be decoded without the need for mechanicalscanning system.
III. EXPERIMENTAL SETUP
Figure 2 shows a schematic diagram of the experimental
setup. A broadband-spectral laser (Spectra-Physics, Inc., Santa
Clara, CA, USA, InSight DeepSee, λC = 780 nm, Δλ = 10 nm,
Pmean = 900 mW) was used for the light source of scan-less 2D
CLM. The output light was line-focused on a diffraction grating(G, Thorlabs, Inc., Newton, NJ, USA, GR25-1208, groove
density = 1200 groove/mm, blaze wavelength = 750 nm) by apair of a cylindrical lens (CL, f = 200 mm) and a lens (L1, f =200 mm) after passing through a spatial filter and a beam
expander (BE). The direction of the focused line on the grating
was orthogonal to the groove direction. Each wavelengthcomponent of the light source was diffracted at different angles
depending on the wavelength and then was focused on thesample by the combination of relay lenses (L2, f = 200 mm; L3,
f = 200 mm) and the objective lens (OL, NA = 0.95,
Magnification = 60). This results in the illumination of thevertical rainbow with a field of view (FOV) of 68 µm × 156.2µm on the sample plane. Although the vertical rainbow isillustrated as a visible rainbow color for easy understanding, its
actual color is considerably monochromatic in the near-infrared
region. The reflected or scattered light at the sample inversely
propagated the same optical path including the objective lens,
the relay lenses, and the diffraction grating, leading to theinverse process of 1D-SE. Such the inverse 1D-SE process
recovers the horizontally line-focused light on the grating again.
After reflected by a beam splitter (BS), the horizontally linefocused light was converted as the vertically line-focused lightand then passes through the incident slit of a multi-channeledspectrometer (Princeton instruments, Inc., Trenton, NJ, USA,
Acton SP2300) equipped with a CMOS camera (Thorlabs, Inc.,
Newton, NJ, USA, DCC1545M, 1280×1024 pixels, pixel size
= 5.2 µm square, bit depth = 10 bit, frame rate = 22 fps). The
incident slit of the multi-channel spectrometer can be used forthe confocal slit for the line-field CLM, too. Thus, the width of
the incident slit determines not only the spectral resolution but

Fig. 2. Experimental setup for scan-less 2D CLM. CL: cylindrical lens, BS:beam splitter, G: grating, L: lens, OL: objective lens, M: mirror.

> JSTQE-CON-BP2019-07475-2018 <also the confocality for the X and Z coordinates. We here set theslit width to be 60 μm by taking into account of the central
wavelength of the light source, the NA of the objective lens, andthe magnification of the lens before the incident slit. This slit
width is corresponding to the spectral resolution of 0.1 nm. In
this way, the spectral line image was acquired by thespectrometer and the camera. Scanning the depth position of asample with the PZT-driven OL scanner (Physik Instrumente,GmbH, Karlsruhe, Germany, P-721, travel range = 100 µm)
enables us to acquire 3D confocal imaging of the sample.

3
resolution, δX_λ, is estimated to be 0.5 μm. Since the theoretical
δX value was larger than the δX_λ value, the former is a dominantfactor of the X lateral resolution in the present system. In thisway, the lateral resolution of the system is mainly determinedby the diffraction limit in the same manner as usual optical
microscopy. Difference of lateral resolution between thetheoretical value and the experimental value is due to theimperfectly filling NA in the objective lens and/or the residual
aberration.

IV. RESULTS
A. Imaging performance
We first evaluated the lateral resolution for the X and Y
coordinates in the constructed scan-less 2D CLM. A
commercialized 1951 USAF resolution test chart with anegative pattern (Edmond Optics, Barrington, NJ, USA, #38256) was placed at the focal position of the objective lens as atest sample. Figure 3(a) shows the confocal 2D image of the test
chart (image size =156.2 µm × 68.0 µm, exposure time of
CMOS camera = 0.23 ms) measured by the scan-less 2D CLM
system. In this image, X and Y coordinates were corresponding
to the line images obtained by 1D-SE CLM and the line-field
CLM, respectively. The fringe pattern along the horizontal
direction in Fig. 3(a) is due to the interference between thetransmitted light and the multiple reflection light in the beam
splitter. We extracted the amplitude profile across the patternedge along a green line and a blue line in Fig. 3(a), and thencalculated their differential curves [see green plots and blue
plots in Figs. 3(b) and 3(c)]. These plots were considerably
noisy due to the low signal-to-noise ratio (SNR). To reduce theinfluence of such nose in the profile, we first calculated themoving average of the differential curves in Figs. 3(b) and 3(c),and then performed the curve fitting analysis using a Gaussianfunction [see a green line and a blue line in Figs. 3(b) and 3(c)].
We here defined the lateral resolution in X and Y coordinates(δX and δY) as a full width of half maximum (FWHM) for thedifferential curves of them. The resulting lateral resolution wasdetermined to be 1.2 μm for δX and 1.2 μm for δY. From thediffraction limit of light, theoretical δX and δY values were given
by [7,8,11]𝜆(1)
𝛿𝑋 = 0.48
𝑁𝐴
0.61𝜆
(2)
𝛿𝑌 =
𝑁𝐴
where λ is a typical wavelength of light and NA is a numericalaperture of OL. Due to use of the confocal slit with theconfocality along the X direction and without the confocality
along the Y direction, the theoretical δX value was smaller than
the theoretical δY value. From λ = 780 nm and NA = 0.95 in thepresent system, theoretical δX and δY values were estimated to
0.4 μm and 0.5 μm, respectively. We have to further consider
the contribution of the spectral resolution in the spectrometer tothe X lateral resolution because the X-line image is encoded on
the optical spectrum in 1D-SE CLM. X dimension of FOV (=156.2 µm) in Fig. 3(a) was corresponding to the spectral rangeof 773 nm to 788 nm with a spectral resolution of 0.1 nm.
Therefore, the X lateral resolution determined by the spectral

Fig. 3. (a) Scan-less 2D confocal image of the test chart (image size = 156.2µm × 68.0 µm). Green and blue lines show the extracted portion for evaluationof the lateral resolution in X and Y directions. Differential curves of theextracted edge profile along (b) X direction and (c) Y direction. The plots
indicate the experimental value, whereas the line indicate the curve fitting
results with a Gaussian function.

We next evaluated the depth resolution δZ along Z coordinate.
To this end, we measured the total signal intensity for 2 pixels
by 2 pixels around the center of image when the Z position of
the sample was moved at a step of 2 µm within the range of -18
μm to +18 µm. Red plots in Fig. 4 shows the depth profile ofthe signal intensity with respect to Z position. For comparison,
the depth profile is indicated as green plots in the same graphwhen the confocal slit was fully opened. Comparison between
them clearly indicated the sharp confocality along the depth
direction. From the curve fitting analysis with a Gaussianfunction, the experimental δZ value was 2.4 µm from FWHM ofthe red depth profile. Let here us consider theoretical δZ value
given by [7,8,11]

Fig. 4. Depth profile of scan-less 2D CLM. Red and green plots show theexperimental depth profile with and without the confocal slit. Red and green
lines indicate the corresponding to curve fitting results with a Gaussianfunction.

> JSTQE-CON-BP2019-07475-2018 <𝛿𝑧 = 0.88

𝜆𝑛 − √𝑛2 − 𝑁𝐴24(3)

where n is a reflective index of the medium between OL and thesample. Substituting 780 nm for λ, 0.95 for NA, and 1 for n, we
obtained δZ = 1.0 μm. Difference of depth resolution between
the theoretical value and the experimental value is due to theimperfectly filling NA in the objective lens and/or the residual
aberration similar to the lateral resolution.
We next performed depth-resolved confocal imaging, orvolume imaging, of a standard sample with known dimension.
to evaluate the imaging performance of the proposed system.
We here used a transparent scotch tape (thickness ≈ 46 µm) asa standard sample with known thickness. To make a twolayered structure, two pieces of scotch tapes were attachedorthogonally to each other at a slide glass as shown in Fig. 5(a).
Movie 1 shows a series of depth-resolved 2D confocal images
when the Z position of OL was scanned within the depth rangeof around 50 µm at 1.4 Hz. Figures 5(b) and 5(c) show two
typical images (camera exposure time = 21 ms, frame rate = 18fps) at different Z positions (Z = 0 µm and 45.1 µm),
respectively. While the surface of the first-layer scotch tape was
focused at Z = 0 µm, that of the second-layer scotch tape was
focused at Z = 45.1 µm Difference of Z position between themwas 45.1 µm, which is in good agreement with the specificationof this tape. In this way, the depth-resolved confocal 2D image
correctly reflects the 3D surface profile of the sample. The
image contrast of the Figs. 5 (b) and (c) were sufficient todiscriminate both layers of the transparent tape. Considering thehigh transparency in biological samples such as tissues and cells,
this result implies that the proposed microscopy has a potential
for 3D imaging of practical biomedical applications.

leaf as a plant sample. Figures 6(a) and 6(b) shows the opticalphotograph of the sample and its microscopic image (image size
= 156.2 µm × 68.0 µm). Although the microscopic image wasobtained by a normal optical microscope (Magnification = 20,
NA = 0.42), it is difficult to observe the distribution of stomata
in the tomato leaf due to the non-confocality. Figure 6(c) showsa sketch of leaf cross section. We here tried to acquire depthresolved 2D confocal images from the side of upper epidermis.
Movie 2 shows a series of depth-resolved 2D confocal images
when the Z position of OL was scanned within the depth rangeof 40 µm at 0.5 Hz. Figure 6(d) shows three typical images atdifferent Z positions (Z = 0 µm, 10 µm, and 30 µm). At Z = 0µm, as the leaf surface was out of focus, no structure appearedin the image. At Z = 10 µm, while guard cells were focused asbright regions, the stoma appeared as a black region of verticaloval inside guard cells, indicating the stoma opening. At Z = 30
µm, upper epidermis and/or palisade mesophyll were visualized
as compartments. In this way, scan-less 2D CLM enables us tovisualize 3D structure of leaf plant with high contrast images inreal time.

Fig. 6. (a) Optical photograph of a tomato leaf. (b) Microscopic image of thetomato leaf (Magnification = 20, NA = 0.42). (c) Sketch of the leaf crosssection. (d) Depth-resolved 2D confocal images of the tomato leaf (image size
= 156.2 µm × 68.0 µm).
Fig. 5. Reflection imaging of the two-layered cellophane tape. (a) Schematic
drawing of the two-layered cellophane tape. A blue rectangle is the measured
portion. (b) Reflection image at objective position = 0 μm (c) Reflection
image at objective position = 45.1 μm (image size = 156.2 µm × 68.0 µm).

B. Observation of plant leaf
Non-invasive observation of plant leaf is required for healthmonitoring of crops because dynamics of the plant leaf isclosely related with the activity of living crops [12]. For
example, stoma plays an important role to maintain internal
environment by continuously exchanging gases with theatmosphere and diffusing water vapor through stoma fortranspiration [13]. Therefore, opening and closing of stoma is agood indicator for the plant growth and health. One potential
application of the scan-less 2D CLM is in an observation ofplant leaf in situ. As a demonstration, we here used a tomato

C. Imaging of biological tissue
Staining method is a powerful tool in histopathology [14].
For the correct diagnosis with histopathology, a thin layer oflesion (typical thickness ≈ 5 µm) has to be appropriately
extracted from a thick specimen of biopsy tissue before thestaining. However, if a position of the sliced specimen isinappropriate, it might be the wrong diagnosis. Opticalsectioning imaging capability with the micrometer depth
selectivity in the scan-less 2D CLM has a potential to find an
application as a sample pre-processing tool in thehistopathology.
To investigate a potential for such application, we
demonstrated imaging of biological tissues. In thisdemonstration, to enlarge FOV, a lower-NA OL (NA = 0.25)
was used for the scan-less 2D CLM. Using this system, δx of

> JSTQE-CON-BP2019-07475-2018 <5

13.9 μm, δY of 2.4 μm, and δZ of 29.4 μm were achieved in theimage size of 1.18 mm × 0.28 mm. Figure 7(a) shows the
Hematoxylin-Eosin (HE) stained image of a sliced rat’s skinsample (thickness = 5 µm). The enlarged view of the blue
rectangle region in Fig. 7(a) is show in Fig. 7(b). The HE
staining method enables the selective visualization of muscle
tissue and extracellular matrix as pink color. In Fig. 7(b),muscle cells enveloped by fibrous connective tissue wereclearly observed in the whole of image. We next measured thesame sample by using the proposed method. Figures 7(c) and7(d) show a comparison of the scan-less 2D image without andwith confocal slit. While the tissue was visualized with someblur in Fig. 7(c) due to non-confocallty, Fig. 7(d) the enhances
the image contrast due to the stray light elimination rather thanthe depth selectivity in the confocality. More importantly, theimage quality in Fig. 7(b) is similar to that in Fig. 7(d); each
unit of the muscle fiber bundles were clearly distinguished in
the image.

Fig. 8. (a) Optical photograph of an electric circuit board. The blue rectangle
shows the measured region. (b) Depth-resolved scan-less 2D confocal images
at z = -150, 450, and 600 µm. (c) 3D confocal image reconstructed by a seriesof depth-resolved scan-less 2D confocal images.

V. DISCUSSION
Fig. 7. (a) HE stained image of a rat’s skin specimen. (b) Magnified image(image size = 0.84 mm × 0.28 mm) of a blue rectangle region in Fig. 7(a). MC;
muscle cell, FCT; fibrous connective tissue. Scan-less 2D confocal images(image size = 1.18 mm × 0.28 mm) of the rat’s skin (c) without and (d) withthe confocal slit.

D. Non-destructive inspection of electric board
Finally, we measured an electric circuit board by the same
lower-NA OL. as a demonstration for the non-destructive
inspection in industrial filed. Figure 8(a) shows an opticalphotograph of the measured sample. The measured region was
the electrode of the chip capacitor. We acquired a series of 2D
confocal images (image size = 1.18 mm by 0.28 mm, exposure
time = 9.15 ms, frame rate = 22 fps) when the sample position
was axially scanned at a step of 50 µm from Z = -150 µm to Z
= 900 µm. Figure 8(b) shows typical 2D confocal images at two
different Z positions. At Z = -150 µm, no signal appeared due
to out of focus for the sample. The image signal started toappear from Z = 0 µm, indicating the sample surface (notshown). The surface structure of the electrode of the chipcapacitor was clearly observed with high image contrast at Z =450 µm, whereas that of the electric board was observed at Z =600 µm. We then reconstructed the volume image of thissample from a series of the depth-resolved 2D image. Figure8(c) and Movie 3 show the reconstructed volume image,indicating the detailed 3D structure of the electric board. The
total acquisition time of this volume image was 525 ms.

We achieve the scan-less 2D CLM with the 0.23-ms
acquisition time, the 1.2-µm lateral resolution, and the 2.4-µm
depth resolution. We here compare this performance with thatof the previous researches. Table 1 summarizes the imagining
performance of the proposed method and other CLMs. There isno significant difference of lateral resolution and depth
resolution among them because they depend on the diffraction
limit of OL rather than the scanning method or the scan-lessmethod. The two former methods have the confocality for X, Y,
and Z axes while the three later methods have the confocality
for X and Z axes; however, the lateral resolution for X and Y
axes were almost similar to each other. Advantage ordisadvantage of those methods are highlighted in the frame rate.
Although the four former methods can achieve higher frame
rate than the proposed method, the requirement for themechanical scanning may hamper the practical application of
CLM mentioned in the introduction. The frame rate of 2D
image in the proposed method is limited by the camera frame
rate, and the present frame rate remained at 22 fps by use ofusual CMOS camera. However, one can use mega-fps CMOS
camera now [15]. In other words, the proposed method has apotential to achieve mega-fps CLM. Such high frame ratecannot be achieved by other CLMs in principle. This
comparison implies a high potential of the proposed system forpractical CLM applications.
We next discuss the acquisition rate of volume imaging. In
usual CLM, the acquisition rate is limited by the lateralscanning, the depth scanning, and/or the camera frame rate.
Thanks to 2D scan-less capability based on a combination of
the line-field CLM and the 1D-SE CLM, the present system

> JSTQE-CON-BP2019-07475-2018 <6

does not need the lateral scanning. The acquisition rate of thepresent system was limited by the PZT-driven OL scanner (scanrate ~ a few Hz) rather than the camera frame rate (= 22 fps).
On the other hand, the moderate image contrast was obtainedeven with the exposure time of 0.23 ms [see Fig. 3(a)]. If a faster
depth scanner and a higher-frame-rate camera are used for thescan-less 2D CLM, the acquisition rate of volume imaging will
be further increased. Fortunately, there is still space to increase
the scan rate of depth scanner and the frame rate of camera. For
example, usual PZT-driven OL scanners have a resonant
frequency of a few hundred Hz; use of a lightweight OL withthe limited stroke will further increase its depth scan rate. Also,
combination of OL with a focus-tunable lens will be useful forthe fast depth scanning. Regarding the camera frame rate, thestate-of-art CMOS camera can boost the frame rate up to 106
fps [15]. Use of these approaches enables us to achieve thevideo-rate volume imaging of moving objects with micrometerspatial resolution; this will find new applications not only inbiomedical application but also industrial inspection.
Finally, we discuss expansibility of the proposed system forscan-less confocal fluorescent microscopy because thefluorescent microscopy is an important imaging modality inbiomedical application. Unfortunately, the present systemcannot be directly applied for the scan-less confocal fluorescentimaging because it depends on the one-to-one correspondence
between the space and the wavelength. Conversion of theexcitation light into the fluoresce by a sample cancels the
spectral information and hence lose the one-to-one
correspondence. However, use of wavelength sweeping light[16] or an intensity-modulated broadband-spectrum light [17]enables the scan-less confocal fluorescent imaging.
TABLE IIMAGING FEATURE OF SEVERAL CLM APPROACHES
Pont scanning

Area scanning(Nipkow)

Line-field

1D-SE

ProposedmethodConfocal
opticsPinholePinhole array

Slit

Slit

Slit

Confocality

X, Y, Z

X, Y, Z

X, Z

X, Z

X, Z

2D imageacquisition

2D
scanning

1D
scanning

1D
scanning

1D
scanning

2D
scan-less

Frame rate of
2D image1 ~ 200 fps

1000 fps

191 fps

30 fps

22 fps(depending on
camera)Lateralresolution

X: 0.2 µm
Y: 0.2 µm

X: 0.2 µm
Y: 0.2 µm

X: 0.7 µm
Y: 0.7 µm

X: 0.78 µm
Y: no data

X: 1.2 µm
Y: 1.2 µm

Depthresolution

0.3 µm

0.6 µm

3.3 µm

2.3 µm(theoretical)

Z: 2.4 µm

Reference[1-4][5, 6][6][7, 8]

VI. CONCLUSIONSIn this paper, we developed a scan-less 2D CLM by the
combination of line-field CLM with the 1D-SE CLM, andfurther expanded it to 3D confocal imaging, or volume imaging,by help of a PZT-driven OL scanner. After the evaluation of theimaging performance, we provided a proof-of-principle
demonstration for three potential applications. Thesedemonstrations imply a high potential of the proposed system
for these practical applications. If the scan-less 2D CLM can be
integrated as a hand-held or endoscope CLM by help of acompact light source (e.g. LED or SLD) and fiber optics, its
robust and simple characteristics will find the clinicalapplications including the intraoperative diagnosis.
ACKNOWLEDGMENT
This work a was supported by grants for the Exploratory
Research for Advanced Technology (ERATO) MINOSHIMAIntelligent Optical Synthesizer (IOS) Project (JPMJER1304)
from the Japanese Science and Technology Agency and a
Grant-in-Aid for Scientific Research (A) No. 15H02026 from
the Ministry of Education, Culture, Sports, Science, andTechnology of Japan.
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[1]

> JSTQE-CON-BP2019-07475-2018 <Eiji Hase was born in Tokushima, Japan,
in 1989. He received the B.S., M.S. and
Ph.D. degrees in engineering from
Tokushima University, Tokushima, Japan,
in 2012, 2014 and 2017.
From 2014 to 2017, he was a Research
Associate with the JST, ERATO,MINOSHIMAIntelligent
OpticalSynthesizer Project. Since 2017, he has
been a Research Scientist with the Research and Utilization
Division, Japan Synchrotron Radiation Research Institute, Sayo,Japan, and a Visiting Associate Professor with the Graduate
School of Technology, Industrial and Social Sciences,
Tokushima University. His research interests include
Biomedical imaging and Biomechanical analysis using
femtosecond laser and synchrotron X-ray.
Dr. Hase was a recipient of The Optical Society of Japan Best
Presentation Award in 2016, The Japanese Society for Medical
and Biological Engineering Symposium Award in 2016, The
International Society for Optical Engineering (SPIE) BiOS2016
in Photonics West 2016 Student Poster Awards in 2016, andSPIE Structured light 2018 Best Paper Award. He is a memberof SPIE.
Takeo Minamikawa was born in Ibaraki,
Japan, in 1983. He received the B.S., M.S.
and Ph.D. degrees in engineering from
Osaka University, Osaka, Japan, in 2006,
2008 and 2010.
From 2010 to 2013, he was a Research
Fellowship for Young Scientists withJapan Society for the Promotion of
Science. From 2013 to 2015, he was an Assistant Professor with
Department of Pathology and Cell Regulation, Graduate Schoolof Medical Science, Kyoto Prefectural University of Medicine.
Since 2015, he has been an Associate Professor with
Department of Mechanical Science, Division of Science andTechnology, Graduate School of Technology, Industrial andSocial Sciences, Tokushima University, Tokushima, Japan. He
is the author of two book chapters, more than 30 articles, andmore than 15 inventions. His research interests include Raman
microspectroscopy and optical-frequency-comb. He holds threepatents.
Dr. Minamikawa’s awards and honors include The Japan
Society for Precision Engineering Best Presentation Award in
2016, The Japanese Society of Pathology Poster Presentation
Award in 2015, and Funai Foundation for Information
Technology Research Award in 2011. He is a member of the
Optical Society of America (OSA), the Japan Society ofApplied Physics, the Optical Society of Japan, the Laser Societyof Japan, the Japan Society of Mechanical Engineers, the Japan
Society for Precision Engineering.

7
Shuji Miyamoto was born in Tokushima,
Japan, in 1992. He received the B.S., M.S.
degree in mechanical engineering from
Tokushima University, Tokushima, Japan,
in 2015, 2017. From 2014 to 2017, hestudied about Nonlinear Optics under Prof.
Takeshi Yasui, Tokushima University. His
research was about Dual-optical-comb
spectroscopy and Scan-less confocal microscope using
broadband light source. From 2017, he has been an Engineer
with the SCREEN Semiconductor Solutions Company Limited,
Shiga, Japan.
Mr. Miyamoto was a recipient of The Japanese Society for
Medical and Biological Engineering Branch Conference Young
Researcher Award in 2016.

Yasuhiro Mizutani obtained his Ph.D.
degree in mechanical engineering from
Tokyo university of Agriculture &Technology, Tokyo, Japan, in 2008. He
has also BE and ME degrees in nuclear
engineering form Osaka university in1997 and 1999, respectively.
From 1999 to 2003, he joined as a
researcher at Panasonic Corporation. Then, from 2003 to 2009,
he worked as a research associate in the Department of
Mechanical systems engineering at Tokyo university ofAgriculture & Technology, Japan. He joined the University ofTokushima, Japan, in 2009 as an associate professor. He iscurrently an associate professor at Osaka university from 2015.
Prof. Mizutani's research interests include interferometry,polarimetry, 3D surface measurement, optical trapping, and 3D
lithography. In these areas, he has published over 100 papers inrefereed international journals and conferences. He is a memberof SPIE and OSA.

Tetsuo Iwata received the Ph.D. degree in engineering from
Osaka University, Osaka, Japan, in 1984.
From 1984 to 1998, he worked in JASCO Corporation, Japan.
He is currently a Professor in the Graduate School ofTechnology, Industrial and Social Sciences, Tokushima
University, Tokushima, Japan.
Prof. Iwata’s research interests include Fluorescentmeasurement and spectroscopy.

Hirotsugu Yamamoto received the Ph.D. degree in
information science and technology from the University ofTokyo, Tokyo, Japan, in 2008.
From 1996 to 2014, he worked in Tokushima University,
Japan. He is currently an Associate Professor in the Graduate
School of Engineering, Utsunomiya University, Utsunomiya,
Japan.
Prof. Yamamoto’s research interests include Information
optics.

> JSTQE-CON-BP2019-07475-2018 <Takeshi Yasui received the first Ph.D.
degree in engineering from the Universityof Tokushima, Tokushima, Japan, in
1997, and the second Ph.D. degree inmedical science from the Nara Medical
University, Yagi, Japan, in 2013.
From 1997 to 1999, he worked as a
Post-Doctoral Research Fellow in the
National Research Laboratory of Metrology, Japan. He waswith the Graduate School of Engineering Science, Osaka
University from 1999 to 2010, and was briefly with the
University of Bordeaux I in 2007 and 2012, and with the
University of Littoral Côted'Opale in 2010 as an Invited
Professor. He is currently a Professor in the Graduate School ofTechnology, Industrial and Social Sciences, Tokushima
University, Tokushima, Japan, Vice Director of Research
Support in the same university since 2016, and an Invited
Professor in the Graduate School of Engineering Science,
Osaka University, Toyonaka, Japan. His research interests
include THz instrumentation and metrology, second-harmonicgeneration microscopy, and optical frequency comb.
Prof. Yasui is a member of the Optical Society (OSA), The
International Society for Optical Engineering (SPIE), the Japan
Society of Applied Physics, the Optical Society of Japan, theLaser Society of Japan, the Japanese Society for Medical andBiological Engineering, and the Japan Society of MechanicalEngineers. He received the Award for the Most Promising
Young Scientist from the Optical Society of Japan in 1998, theSakamoto Award from the Japan Society of Medical
Electronics and Biological Engineering in 2006, the Optics
Paper Award from the Japan Society of Applied Physics, andthe Funai Award from the Japan Society of MechanicalEngineers in 2009, the Original Paper Award from the Laser
Society of Japan in 2013.

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