2.4
2.4 Operating
Operating Principle
Principle
2 - 6
2 - 6
2.4
2.4 Operating
Operating Principle
Principle
Figure 2-6 shows the optical system
Figure 2-6 shows the optical system of the Model U-2810
of the Model U-2810
Spectrophotometer.
Spectrophotometer.
The white light emitted from the light source is fed to
The white light emitted from the light source is fed to the Seya-
the Seya-
Namioka mount monochromator utilizing a concave diffraction
Namioka mount monochromator utilizing a concave diffraction
grating (with a grating constant of
grating (with a grating constant of 1/600 mm, a
1/600 mm, a blaze wavelength
blaze wavelength
of 250 nm and a diffraction area of 20
of 250 nm and a diffraction area of 20 mm
mm
×
×
25 mm), where it is
25 mm), where it is
transformed
transformed into
into a m
a monochromatic
onochromatic beam.
beam. The
The beam
beam sent
sent from
from
the monochromator passes through the filter, is
the monochromator passes through the filter, is reflected by the
reflected by the
toroidal mirror, and is then
toroidal mirror, and is then separated into reference beam and
separated into reference beam and
sample beam by the grating mirror.
sample beam by the grating mirror.
The two beams which have passed through the sample
The two beams which have passed through the sample
compartment are focused by lenses and irradiated into the
compartment are focused by lenses and irradiated into the
detectors, where they are converted into electric
detectors, where they are converted into electric signals.
signals.
This optical system has the
This optical system has the following features.
following features.
(1)
(1) The
The Seya-Namiok
Seya-Namioka
a mount
mount optical
optical system
system utilizing
utilizing Hitachi’s
Hitachi’s
reputable concave diffraction grating realizes a
reputable concave diffraction grating realizes a
monochroma
monochromator featuring a high
tor featuring a high energy efficiency and a low
energy efficiency and a low
stray light level.
stray light level.
(2)
(2) The b
The beam i
eam is sep
s separated
arated by us
by using a
ing a grating
grating mirror
mirror rather
rather than
than
a rotating mirror like in
a rotating mirror like in the conventional double beam
the conventional double beam
spectrophotom
spectrophotometer.
eter. This
This structure
structure serves
serves to
to eliminate
eliminate the
the
moving parts, thus realizing a stable
moving parts, thus realizing a stable and reliable
and reliable
monochromator.
monochromator.
(3)
(3) The
The optical
optical systems
systems at the
at the sample
sample beam
beam and
and reference
reference
beam sides are absolutely the same, t
beam sides are absolutely the same, thus enabling
hus enabling
acquisition of stable data.
acquisition of stable data.
The electric signal converted from an
The electric signal converted from an optical signal is amplified,
optical signal is amplified,
A/D-converted a
A/D-converted and then LOG- con
nd then LOG- converted with softwar
verted with software to provide
e to provide
absorbance
absorbance data.
data. The re
The result o
sult of measu
f measurement
rement is ou
is output to
tput to the
the
monitor and printer (see Fig.
monitor and printer (see Fig. 2-7).
2-7).
2.4.1
2.4.1 Optical
Optical System
System
2.4.2 Signal
2.4.2 Signal
Processing and
Processing and
Control System
Control System
