FIELD OF INVENTION:
The present invention is directed to a system of quantitative measurement of surface
brightness of any metal/nonmetal by the reflection of light from the thin sheet strip surface
by the method of comparison with the reflectance value of plane of mirror. In the present
system of measurement when the power is made on, the light rays emitted from LEDs are
adapted to fall on a plane mirror/test strip and get reflected which in turn is allowed to fall
on a convex lens which is refracted to a light dependent resistance (I.DR). Depending upon
the intensity of light the resistance of LDR changes and in turn the current in electronic
circuit changes which is measured by a digital multimeter. The system is low cost and
provides for accurate measurement. It is light weight and easy to handle with very easy
maintenance.
BACKGROUND AND PRIOR ART:
It is known that the electrolytic tin deposition on cold rolled sheet in steel plants for better
surface appearance in selective applications are normally carried out in cold rolling mill
(CRM). It has been, however, an accepted practice for such processes that, the assessment
of the brightness of the electrolytic tin plate is done by visual inspection which is highly
subjective in nature and varies largely from person to person resulting in inconsistent and
erratic assessment due to human error and perceptual variability. It is because of this
variable factors in the conventional process of visual inspection and subjective assessment,
the final acceptance standards are hardly maintained and about 12 % of fresh stock of.
electrolytic tin plate has to be diverted to seconds grade in a particular year, due to dull and
dirty appearance of the surface of the said stock.
It was therefore a persistent need in cold rolling mills to develop a device that would
measure the surface brightness of any metal/nonmetal thin strip and in particular
brightness of cold rolled thin electrolytic tin plate/sheet to facilitate quantitative assessment
of surface brightness following a standard and reduce variability in assessment.
The early stages of the present invention made use of the fundamental principle of physics
by measurement of intensity of reflected light from bright surfaces and comparing the value
in terms of a plane mirror as standard. However, such measure of brightness as
proportional to change in current in a LDR circuit suffered from erratic and inconsistent
readings. The input supply to the electronic circuit involved in such measurement was also

not regulated or controlled, resulting in fluctuations and erroneous conclusions about
measurement of surface brightness. To avoid the limitations of the earlier measurement
process, the reflectometer device of the present invention was developed for steady and
reliable quantitative measurement of brightness of steel/ other thin sheet surfaces.
OBJECTS OF THE INVENTION:
The basic object of the present invention is therefore to develop a device incorporating
electronic system/reflectometer to carry out quantitative measurement of brightness of
reflecting surface of thin sheet of steel/metal/nonmetal, in particular for measurement of
brightness of electrolytic tin plate surface.
A further object of the present invention using electronic system/ reflectometer for
quantitative measurement of surface brightness, to make use of comparison of intensity of
reflected light from the testpiece surface with respect to a mirror as a standard of 100.
A further object of the present invention using electronic system/ reflectometer for
quantitative measurement of surface brightness, to use a preferred arrangement in
selective numbers of Light Emitting Diodes(LEDs) providing the source of light and also a
predefined arrangement of a specified number of Light Dependent Resistances(LDRs) to
sense the intensity of light reflected from the test piece surface.
Yet another object of the present invention is to pass the light from said LEDs to pass
through a convex lens with guide and a frosted glass sheet so that the light rays incident on
the LDRs placed within the focal length of the said lens for intended measurement of
brightness of surface are uniformly illuminated and do not receive any direct light rays from
the LEDs.
A still further object of the present invention using electronic system/ reflectometer for
quantitative measurement of surface brightness of metal/nonmetal thin sheets, is to provide
a precision regulated power supply to various subsystems after proper rectification and
regulation to maintain steady required supply voltage and current without fluctuation, such
that the measurement become consistent, accurate and reliable.
Yet another object of the present invention using electronic system/ reflectometer for
quantitative measurement of surface brightness, to enable said system to provide means for

selectively control the numbers of LEDs used as light source in a specified arrangement, to
achieve variable illumination.
A further object of the present invention using electronic system/ reflectometer for
quantitative measurement of surface brightness, to provide in the said system/subsystem a
brightness controller means to adjust the initial reading to 100, as and when necessary, to
set as standard.
A further object of the present invention using electronic system/ reflectometer for precise
and accurate quantitative measurement of surface brightness of metal/nonmetal thin sheet,
such that the device is cheap, light weight and user friendly with easy and inexpensive
maintenance.
SUMMARY OF THE INVENTION:
It is therefore the basic aspect of the present invention to develop an
electronic system/reflectometer for measuring surface brightness of thin sheet/strip of
metal/nonmetal comprising:
a light tight enclosure having at one end means to measure the light intensity reflected from
a mirror /test piece positioned at its other end;
said means to measure the reflected light intensity comprising:
(i) Light Emitting Diodes (LEDs) adapted to provide light of appropriate illumination;
(ii)Light Dependent Resistances (LDRs) adapted to sense the intensity of reflected light
from a test piece/sheet surface, and favour measurement of surface brightness by
measuring variation in voltage across a resistance in corresponding LDR circuit due to
variation in intensity of reflected light from said test piece compared to a standard mirror
surface;
(iii)an eye piece with a convex lens adapted to converge the incident light rays from the
LEDs after reflection from the test piece/mirror surface within its focal length for
advantageous sensing by the LDRs located at central place of LEDs to favour best reception

of light after reflection from test surface and refraction through the convex lens and no
direct light from the LEDs.
According to a further aspect of the present invention said electronic system/reflectometer
for measuring surface brightness of thin sheet/strip of metal/nonmetal comprising:
a frosted glass plate having suitable central opening to accommodate the lens casing,
advantageously placed in front of the LEDs mounted on PCB to facilitate incidence of
diffused light on to the LDRs; and
a potentiometer type of brightness controller to adjust the initial reading to 100, for
comparison to take place with respect to a standard illumination, for the intended
measurement of surface brightness of test strip.
According to a further aspect of the present invention said electronic system/reflectometer
for measuring surface brightness of thin sheet/strip of metal/nonmetal wherein significant
fluctuation in the value of brightness of test piece due to unregulated power supply to the
sensor circuit was stabilized incorporating means for regulated power supply, comprising :
i) Modification to input power supply circuit to control the fluctuation to achieve precise,
accurate and consistent reading for surface brightness;
ii) Voltage measurement system adopted as a means to measure brightness, instead of
current measurement with digital multimeter. ^
iii) The frosted glass sheet is provided in front of LEDs and LDR PCB to have uniform
diffused light falling on test piece.
According to yet another aspect of the present invention, a preferred embodiment of said
electronic device/reflectometer for measurement of surface brightness, make use of 20
numbers of high intensity LEDs as source of light, connected in parallel with individual
supply resistance to 12 volt DC through a potentiometer, instead of series connection, to
prevent stoppage of light supply in case any of these diodes fails.
. According to yet another aspect of the present invention, said electronic
device/reflectometer for measurement of surface brightness of thin sheets/strip, said
specified arrangement and numbers of LEDs and LDRs, include twenty numbers of said LEDs
assembled on a PCB with equal spacing around a two inch diameter circular space at center,

meant for mounting of six numbers of said LDRs very close to each other in a circular
manner to sense reflected light rays of equal intensity and located within the focal length of
the said convex lense.
According to a further aspect of the present invention, said electronic device/reflectometer
for measurement of surface brightness of thin sheets/strip, providing means for intended
measurement of surface brightness by measuring and displaying the milli volts generated
across a specified resistance in the LDR circuit of the system and displayed through four
numbers of seven segment display units.
According to a further aspect of the present invention, said electronic device/reflectometer
for measurement of surface brightnesa of thin sheets/strip, providing means for accuracy
verification by successive disconnection of LEDs, one at a time, starting with ten numbers
and brightness measured for each illumination, with and without adjusting the initial reading
of mirror( to set to 100); reasonable consistency in test piece brightness reading was
observed with at least five numbers of LEDs.
According to a further aspect of the present invention, said electronic device/reflectometer
for measurement of surface brightness of thin sheets/strip, for accuracy of measurement to
be maintained, the lens and mirror are to be cleaned at least once in a month and the
numbers of LEDs working in order need to be checked.
The present invention and its objects and advantages are described in greater details with
reference to accompanying figures and non-limiting exemplary illustrations.
BRIEF DESCRIPTION OF FIGURES:
Figure 1: Showing the outside of an electronic system/ Reflectometer of present invention
at initial stage of development with uncontrolled power supply.
Figure 2: Showing the inside of a Reflectometer of present invention at initial stage of
development.
Figure 3: Illustrates the schematic block diagram of modified reflectometer with precision
regulated power supply, according to present invention.
Figure 4: Illustrates the circuit diagram for the precision regulated power supply for
reflectometer showing the components used.

Figure 5: Illustrates the Circuit diagram foMight supply system of reflectometer comprising
20 numbers high intensity LEDs connected in parallel, showing the components used.
Figure 6: Illustrates the circuit diagram for the light sensors (LDRs) and precision
instrumentation amplification unit, with component list.
Figure 7: Illustrates four numbers of seven-element display units with AD/decoder/driver
unit, showing the components used.
DETAILED DESCRIPTION WITH REFERENCE TO ACCOMPANYING FIGURES:
Reference is first invited to accompanying Figure 1 of the electronic system/reflectometer
developed in the present invention at early stage. The reflectometer was a box type device
within which the basic electrical circuit comprising electronic components and other
elements used for measurement of surface brightness were housed. It is a box of dimension
45cm x 20cm x 18cm approximately, having weight of 2kgs.The box is provided with the
essential gadgets of the instruments for its operation and control ^viz the slot provided at top
of the box for inserting a test piece/thin strip of suitable size for measuring its brightness.
Also, there is an on/off switch to connect the instrument with 220v AC input on the front
portion of the box, an LED indicator for indicating the connection status of the instrument, a
light intensity controller for adjusting initial reading as needed and the display unit where
the brightness reading is obtained through a digital multimeter. The box is also provided
with a fuse and cable with socket for electrical connection.
Reference is now invited to the accompanying Figure 2 illustrating the inside view of the
reflectometer of the present invention developed at an early stage. It is apparent from the
view that the whole circuit is placed inside a light tight box at one end and a plane mirror
fixed vertically at the other end. The PCB for the LEDs and the LDRs are placed at an
intermediate place and a frosted glass sheet with a central opening of 1.5 inch to passage of
the lense casing of the eye piece with a convex lens used to converge the incident diffused
light rays within its focal length, being the place where the LDRs are mounted on PCB. A
narrow slot/passage is provided very close to the mirror to insert the test piece of thin sheet
about 0.26 to 0.3mm thick, having overall size of 18cmx20cm vertically for surface
brightness measurement. The instrument is capable of measuring surface brightness of any
metallic/nonmetallic thin sheets by method of comparison with the reflectance value of a
plane mirror whose brightness has been considered as standard value of 100. When the
power is made on, the light rays emitting from the LEDs fall on the said plane mirror being
fixed just opposite to the LEDs, and get reflected. The reflected light rays fall on a convex

lens which after refraction fall on a LDR placed within the focal length of the said convex
lens. Depending on the intensity of the incident light rays, the resistance of the LDR
changes and the resistance value becomes high for low intensity light and vice versa. When
the resistance value of LDR changes in the corresponding electrical/electronic circuit, flow of
current also changes. This current is measured in microampere by a digital multimeter as an
indicator of surface brightness in comparison with the same value for the plane mirror( i.e.
100) initially obtained with necessary adjustments.
The present invention made use of the fundamental principle of physics by measuring the
intensity of reflected light from rays from the bright surfaces and comparing the value in
terms of a plane mirror considered as standard. However, such measure of brightness as
proportional to change in current in a LDR circuit suffered from erratic and inconsistent
readings. The input supply to the electronic circuit involved in such measurement was also
not regulated or controlled at initial stage of development, resulting in fluctuations and
erroneous conclusions about measurement of surface brightness. To avoid the limitations of
the measurement process observed initially, the electronic system/reflectometer of the
present invention was developed for steady, accurate and reliable quantitative
measurement of brightness of steel/ other thin sheet surfaces.
Reference is now invited to Figure 3, that illustrates the reflectometer of the present
invention incorporating the modifications in the present stage of development to achieve
fluctuation free readings for quantitative measurement of surface brightness of test
piece/strip of thin metal/nonmetal sheet with accuracy, precision, consistency and
reliability.
According to a preferred embodiment of the modified version of the reflectometer of the
present invention as illustrated in figure 3 as block diagram, the electronic system
comprises various subsystems/units with independent functional features, such as (a) the
power supply system for precisely regulated power supply as required by other functional
units in the total system; (b) the light supply system for intended surface brightness
measurement based on the basic principle of comparison of reflected light from the said
surface with respect to a mirror as standard, as demonstrated in the Stage-1 of the
invention;(c) the light sensor and display unit for precise and consistent
measurement/readings for the test piece surface brightness.
The power supply system receives 220volt AC as input to a step down centre tap
transformer to transform it to an output of 12-0-12 AC, 500 milli ampere for use to get

necessary voltage and current after rectification and regulation. The voltage regulator IC-
7812 and IC-7805 are used to get steady and fluctuation free working voltage for different
circuits. From 12 volts DC supply, variable voltage is given to LED circuit for getting variable
iliumination. A supply of 5 volt DC is made to the LDR circuit, precision instrumentation
amplifier (CA-741 i.e. operational amplifier) circuit. A supply of +/- 5 volts supply is made
to the Analog to Digital (AD)/Decoder/Driver stage of display unit. 5 volt DC is also supplied
to seven segment display units. Power supply circuit showing components used with
specification/value, is illustrated in accompanied Figure 4.
The power supply system consist of a step down transformer(Xl) of rating 220V AC
input/12-Q-12V AC, 500mA output; D1,D2,D3 are diodes IN 4007; CI is the capacitor of
rating 2200mf/35V;C2 and C3 are capacitors with rating of 10mf/25 V; C4 is a capacitor
having the rating of 1000mf/25V;Zl is a zenor of rating 5.1V/500mw; Fl is a fuse of lOOma
rating; Resistances Rl and R2 of ratings 470 ohm/0.5w;VR is a potentiometer of rating
10K/10 turns;Tl is a transistor-2N 3055; Two Voltage regulators used are IC1-7812-12V
and IC2-7805-5V;Sl and S2 are On/Off switches Double Pole Double Throw Type.
The safety aspect of the power supply circuit is ensured by protecting the system with the
components like AC connection cord with inlet rubber grommet, double pole double
throw(DPDT) for On/Off switch, glass tube type fuse of rating 100 milli ampere, power
supply status indicator with LED and the transformer is well insulated from the cabinet.
The light supply system of the reflectometer according to the present invention and the
related electrical circuit is illustrated in the accompanying Figure 5. This system comprise of
twenty numbers high intensity Light Emitting Diodes(LEDs) for supplying required light for
measurement of surface brightness. These LEDs are connected in parallel instead of series
connection to prevent stoppage of light emission from LEDs in case any of the LEDs fails.
The LEDs connected in parallel with individual supply resistance to 12 volt DC through a
potentiometer of rating 10 killo ohms/10 turns, linear, to get very minor control over light
brightness to achieve steady initial reading of '100' in the display unit, when mirror
reflection is considered and the reading is not coming exactly 100. These LEDs are
assembled on a PCB with equal spacing around a two inch diameter circular place
circumferentially, at centre of which is also the place meant for fixing the LDRs. A frosted
glass plate having a hole of 1.5 inch diameter at centre for the passage of lens casing/eye
piece, is placed in front of the LED PCB to get uniform diffused light to be incident on the
reflecting surface of mirror/test-piece. The LEDs of high intensity type is used for the
reasons like-(a) LEDs consume less power and generate less heat,(b) Smaller size and

durable,(c) light emitted from the LEDs are unidirectional and as such can be
advantageously used to direct the reflected light as required.
The light sensing and precision amplification unit of the reflectometer/electronic system is
illustrated in the accompanying Figure 6. The sensor unit comprise of six numbers of Light
Dependent Resistances(LDRs) assembled in parallel very close to each other in circular
manner to ensure the fall of reflected light rays from the test piece after refraction through
the convex lens with uniform intensity. An eye piece with convex lens is used. LDRs are
placed inside the lens casing such that no direct light from the LEDs fall on the LDRs. Power
is supplied to the LDRs from 5 volt DC through a resistance R-7 of value 2 kiilo ohms.
Voltage developed across the resistance R-7 is amplified by three stage operational
amplifier(IC 1, IC 2, IC 3- CA-741 OP. AMP). This unit works on 5 volt DC coming from
regulated power supply system. Output of this unit(A,B) is given to pin no. 30 and 31 of IC-
1 (ICL-7107) i.e. Analog to Digital(AD)/Decoder/Driver IC.
Four numbers of seven-element display units (LT-542) with AD/Decoder/Driver unit(IC 1-
ICL7107), showing the other components used, as illustrated in Figure7. These display
units are used for display of milli volts generated across the resistance R-7 in the LDR
circuit. A potentiometer (RV-1) of resistance 1 killo ohm is used for calibration to get more
than 100 milli volts output. The circuit also uses capacitors Cl-220pf,Ceramic;C2,C3-
lmf/35V,Electrolytic;C4-4.7mf/10V, Tantalum, C5-0.47mf/10v-Tantalum; Resistances used
are R1,R3-100K, 0.5 w, metal film; R2-330K,0.5w,mer.al film; R4,R5-4K7, 0.5w, metal film
and IC 2-2.7 V, regulated IC.
The method of measuring the brightness of a testpiece utilizing the reflectometer of the
present invention, first the input power supply is provided to the instrument by connecting
with the 3 pin, 5 ampere socket with cable and proper earthing and switching on the power.
As the power to the device is made on, the red indicator lamp starts glowing. Wait for a few
minutes till the reading on display is found to become steady for reflection from plane
mirror. Adjust the brightness control switch to get exact '100', if the initial reading does not
show '100'. After getting initial reading set to 100, insert the test piece of size 18cm x 20
cm, vertically into the slot provided in the device. The sample for the test purpose must
have its surface essentially absolutely flat to facilitate even reflection of light rays. A waiting
time of at least 1 minute is allowed for the reading to become steady, which is the milli volts
reading obtained in the LDR circuit as already described, proportionate to the intensity of

the incident light sensed by the LDRs. This reading gives the percent brightness of the test
piece surface. The test piece is then removed from the slot. Now check the initial reading
again which should come back to '100'. The reading again comes back to '100', confirming
that the light and the sensor units are working in order.
The present invention directed to measurement of surface brightness of thin
metal/nonmetal sheet is further described to illustrate its accuracy and consistency of
measured values with the help of the following examples.
EXAMPLES:
According to another preferred embodiment of the present invention, the accuracy and
consistency was verified and ascertained by conducting experiment with the same
reflectometer device having light supply source/system with 10 numbers of LEDs at
starting. The initial brightness was kept at x100'. Then the test piece brightness was found
94%. The same experiment was repeated by disconnecting the LEDs one by one, without
adjusting the initial brightness of mirror to '100'. Result of the experiment obtained as the
test piece brightness as percent of initial reading for different level of illumination with
gradually reducing numbers of LEDs, is shown in TABLE -I herein below.

It was established from the experiment and the results obtained, that there is consistency in
test piece brightness readings up to 5 numbers of LEDs used as light source and without
adjusting the initial brightness reading to '100'; Also the result obtained was erratic with

further lesser number of LEDs. Thus at least 5 LEDs should be used as light source to
achieve consistency in brightness readings using this reflectometer instrument of the
present invention.
In another experiment following the same method was carried out as the earlier one but
with the initial reading obtained for reflection from mirror surface adjusted to '100' for all
alternative numbers of LEDs in each test run. The resulting bright ness data for the test
piece brightness is illustrated in TABLE-II below.

Data obtained in this experiment clearly shows that the observed values of surface
brightness is consistent upto 3 numbers of LEDs used as light source and with illumination
below that level, the results obtained was found to be erratic.
Hence it is concluded based on the findings of the above experiments, that irrespective of
the adjustments in the initial brightness reading (set to 100) with mirror as the reflecting
surface, there is consistent brightness reading obtained for the test piece using the
reflectometer with at least 5 numbers of LEDs glowing, to facilitate accurate sensing by the
LDR and display units.

We claim:
1. An electronic system/reflectometer for measuring surface brightness of thin sheet/strip
of metal/nonmetal comprising:
a light tight enclosure having at one end means to measure the light intensity reflected from
a mirror /test piece positioned at its other end;
said means to measure the reflected light intensity comprising:
(i) Light Emitting Diodes (LEDs) adapted to provide light of appropriate illumination;
(ii)Light Dependent Resistances (LDRs) adapted to sense the intensity of reflected light
from a test piece/sheet surface, and favour measurement of surface brightness by
measuring variation in voltage across a resistance in corresponding LDR circuit due to
variation in intensity of reflected light from said test piece compared to the mirror surface.
(iii)An eye piece with a convex lens adapted to converge the incident light rays from the
LEDs after reflection from the test piece/mirror surface within its focal length for
advantageous sensing by the LDRs located at central place of LEDs to favour best reception
of light after reflection from test surface and refraction through the convex lens and no
direct light from the LEDs;
said LEDs assembled on a PCB with substantially equal spacing around a central circular
space circumferentially, the inner space of which is provided for mounting of said LDRs close
to each other in a circular manner to sense reflected light rays of equal intensity and located
within the focal length of the said convex lens.
2. An electronic system/reflectometer for measuring surface brightness of thin sheet/strip of
metal/nonmetal as claimed in claim 1 comprising :
a frosted glass plate having suitable central opening to accommodate the lens casing,
advantageously placed in front of the LEDs mounted on PCB to facilitate incidence of
diffused light on the test piece uniformly; and

a potentiometer type of brightness controller to adjust the initial reading to 100, for
comparison to take place with respect to a standard illumination, for the intended
measurement of surface brightness of test strip.
3. An electronic system/reflectometer for measuring surface brightness of thin sheet/strip
of metal/nonmetal as claimed in anyone of claims 1 or 2 comprising means for regulated
power supply comprising :
i) input power supply circuit adapted to control the fluctuation to achieve precise,
accurate and consistent reading for surface brightness;
ii) Voltage measurement system adapted to measure brightness, instead of current
measurement in digital multimeter.
iii) provision of frosted glass sheet in front of LEDs and LDR PCB to have uniform
diffused light falling on test piece.
4. An electronic system/reflectometer for measuring surface brightness of thin
sheet/strip of metal/nonmetal as claimed in anyone of claims 1 to 3 comprising said
electronic system for measurement of surface brightness, obtained of 20 numbers of
high intensity LEDs as source of light, connected in parallel with individual supply
resistance to 12 volt DC through a potentiometer, adapted to avoid problems of any
single diode failure.
5. An electronic system/reflectometer for measuring surface brightness of thin
sheet/strip of metal/nonmetal as claimed in anyone of claims 1 to 4 comprising means
for accurate and consistent measurement of surface brightness by measuring and
displaying the milli volts generated across a specified resistance in the LDR circuit of the
system.
6. An electronic system/reflectometer for measuring surface brightness of thin
sheet/strip of metal/nonmetal as claimed in anyone of claims 1 to 5 comprising means
for display of the brightness reading through segmented display units based on signals
generated in LDR sensor and amplifier circuit.

7. An electronic system/reflectometer for measuring surface brightness of thin
sheet/strip of metal/nonmetal as claimed in anyone of claims 1 to 6 comprising means
for accuracy verification by successive disconnection of LEDs, one at a time, starting
with ten numbers and brightness measured for illumination with each combination of
glowing LEDs, with and/or without adjusting the initial reading of mirror( to set to 100).
8. An electronic system/reflectometer for measuring surface brightness of thin
sheet/strip of metal/nonmetal as claimed in anyone of claims 1 to 7 comprising
providing means for accuracy verification wherein for reasonable consistency in test
piece brightness reading providing at least five numbers of LEDs, with or without
resetting the initial brightness reading for mirror surface to 100.

ABSTRACT

AN ELECTRONIC SYSTEM FOR MEASURING SURFACE BRIGHTNESS OF THIN SHEET/STRIP
OF METAL/NONMETAL.
An electronic system for measuring surface brightness of any metal/nonmetal thin sheet
strip surface by comparing the intensity of reflected light from the said surfaces. The
brightness percent is compared with that of a plane mirror surface considered as
standard(lOO). Light Emitting Diodes (LED) connected in parallel and mounted on a printed
circuit board(PCB), are the light source. A frosted glass sheet is placed in front of LEDs PCB
such that diffused light fall uniformly on test piece. The test piece of 18cm x 20 cm is
inserted in the slot provided on the top side of a light tight box, ahead of said mirror placed
at one end. The reflected light rays from surface of sheet pass through an eye piece with a
convex lens. Intensity of the incident light ray, results in change in voltage across a
resistance in the LDR circuit, and is read in milivolts by four numbers seven segment display
unit as a measure of brightness of the test surface. A potentiometer type brightness
controller sets the initial reading to 100, with mirror standard.