Hamamatsu News 2-2014 - page 6

News 2014 Vol. 2
6
R&D Interview
How did you solve the problems you faced in trying to cut costs?
Shibayama:
Mini-spectrometers (MS series) utilize a glass lens as the
medium for transmitting light. Glass offers the advantage of providing
the required accuracy for the spectrometers if the dimensional
accuracy of the glass itself is maintained. However, the cost of glass
lenses is high, so we had to give up on glass lenses and find a
substitute to meet demands for lower cost.
Yokino:
In the MS series, mini-spectrometers, a grating is formed
on the glass lens by nanoimprinting. However, if the nanoimprinting
failed, the glass lens would then be unusable causing the problem
of higher costs. So instead of forming a grating on the glass lens, we
re-evaluated the possibility of fabricating the grating as a separate
unit. This would allow eliminating glass to fabricate the grating and
would also prove effective in lowering the cost.
What type of sensor is used in the micro-spectrometer?
Yokino:
The micro-spectrometer uses an image sensor integrated
with an input slit. Using this type of sensor allows us to reduce the
spectrometer to a fingertip size. After the incident light is diffracted
by the grating, short wavelength light reaches a position very close
to the input slit. If the slit is separated from the sensor, extremely fine
positioning is required, because failing to achieve this fine positioning
degrades spectral performance. The slit integrated with the sensor
does not create this positioning problem.
Shibayama:
We also added a cutoff filter (see note) to this image
sensor integrated with the input slit. When fabricating the mini-
spectrometers (MS series), we mounted an image sensor on the
glass wiring board which had metal wiring and formed the cutoff
filter on this glass wiring board. However, in the case of the micro-
spectrometer, we gave up on glass and utilized a hollow space to
convey the light, so directly forming a cutoff filter for the image
sensor in this way was an indispensable part of the process.
Ito:
Besides the basic function that the image sensor receives light,
the image sensor itself has an added value as it includes an input slit
and a cutoff filter. Having both image sensor technology and MEMS
technology is our unique advantage.
Note: Cutoff filter is a filter that cuts off stray light components such
as multiple reflected light and diffraction order light other than the
measurement light.
Providing specifications ideal for customer
application development work
What kind of applications do you foresee for micro-spectrometers?
Ito:
We are currently receiving requests for applications involving
color, such as portable colorimeters and the checking of colors in
printed material, etc. The advance from mini-spectrometers (MS series)
to micro-spectrometers has also increased inquiries for handheld
medical devices which are related to POC (Point of Care) tasks.
Utilizing a small, low priced but highly reliable package that does not
allow moisture penetration has proved successful.
Hikita:
Our position is that we should assist customers to develop
spectrometer applications for providing consumer electronic products.
We therefore believe that our main role is to provide the specifications
needed by customers to make spectrometer applications a reality.
Can you also produce custom designs to meet customer needs?
Ito:
We first verify the customer’s requested specifications and the
estimated quantity and if the project is likely to require an adequate
number of products, then we can come up with a design that matches
the requirements. When we receive a request, our engineers will then
start discussions while still at an early stage.
Possibilities offered by
new applications through
miniaturizing spectrometers
Simple color measurements
using smart phones
Color adjustment of
color printer
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