D
`
`United States Patent [191
`Beha
`
`[11] Patent Number:
`[45] Date of Patent:
`
`4,870,264
`Sep. 26, 1989
`
`[54] DEVICE FOR OPTICALLY MEASURING
`THE SHADING 0F TRANSLUCENT PANES
`[76] Inventor:
`Christian Beha, Fohrentalstrasse 6,
`D-7804 Glottertal, Fed. Rep. of
`German
`y
`_
`[21] Appl' No" 224’152
`[22] Filed:
`Jul. 26, 1988
`[gé] 1m. (64 ..................................... 3531315152353;
`1
`l
`- - - - - - - - - - - - - - -
`' ' ' "250 208 ’209 578‘
`[58]
`‘e d of catch """"""""""" " 356/ 24‘; 222’ 224i
`/ ’
`’
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`3,941,487 3/1976 Ehret et al. ....................... .. 356/244
`3,989,948 11/1976 Allington ...................... .. 250/578
`4,037,972 7/1977 Pross ........ ..
`, 356/206
`4,236,826 12/1980 Yamanishi ..................... .. 356/432
`Primary Examiner-David C. Nelms
`Assistant Examiner-William L. Oen
`Attorney, Agent, or Firm-Mason, Fenwick 8: Lawrence
`
`ABSTRACT
`[57]
`A device for measuring the shading of a translucent
`pane having an exterior side and an interior side com
`prising ?rst and second photoelectric sensors for mea
`suring'unattenuated daylight, each of the sensors having
`h t
`'t'
`f
`d
`‘t
`1
`‘t' 't
`b
`a p o osensi ive sur ace an a spec ra sensi 1v1 y su -
`stantially corresponding to the spectral sensitivity of the
`hunlllan eye and generating an outgutlsignal ptroportional
`to t e intensity 0 t e measured ay ight, a irst mount
`mg elementfor mountingthe ?rst sensor on the exterior
`surface with the photosensitive surface of the ?rst sen
`sor facing away from the exterior surface, a second
`mounting element for mounting the second sensor on
`the interior surface with the photosensitive surface of
`the second sensor facing the interior surface, a housing,
`and an electronic circuit disposed in the housing and
`electrically connected to the ?rst and second sensors for
`calculating the difference of the output signals of the
`?rst and second sensors, calculating the ratio of the
`difference to the signal from the ?rst sensor, and dis
`playing the ratio as a reference value.
`
`14 Claims, 5 Drawing Sheets
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`HIIIIIIIIIIIHHH
`HZ/ LCD - DispLag
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`Magna 2040
`TRW v. Magna
`IPR2015-00436
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`US. Patent Sep.26, 1989
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`MADE IN ‘PL-GERMANYJ
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`1
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`DEVICE FOR OPTICALLY MEASURING THE
`SHADmG OF TRANSLUCENT PANES
`
`FIELD OF THE INVENTION
`The invention relates to a device for measuring the
`shading of transparent panes or other pane-shaped ob
`jects, especially for measuring the shading of the panes
`of a motor vehicle.
`
`4,870,264
`2
`a separate light source, which permits measurement
`over a wide range of light intensity, which has a spec
`tral sensitivity which corresponds to the spectral sensi
`tivity of the human eye, which has sufficient accuracy,
`is designed as a pocket device, requires no external
`power source, and has a digital display, and which
`permits measurements to be made from outside the
`vehicle.
`
`SUMMARY OF THE INVENTION
`According to the invention a device is provided
`which has two photosensors, one of which is applied to
`the outside of the vehicle and the other, to the inside.
`The photosensors simultaneously measure the unattenu
`ated daylight outside the vehicle pane and the attenu
`ated daylight produced by the shading of the vehicle
`panel, inside the vehicle. The two photelectric sensors
`have a spectral sensitivity which corresponds to the
`spectral sensitivity of the human eye. Hence, the attenu
`ation of the light intensity by the shading of the vehicle
`pane is measured that is effective with respect to the
`human eye.
`The device measures daylight and therefore does not
`require any light source of its own. The power con
`sumption of the device is correspondingly low, so that
`the device requires no external power source and can be
`powered by a battery.
`The photoelectric sensors of the device are con
`nected by cables to a small portable housing which
`contains the electronic circuit for comparing the light
`intensities measured by the two sensors and for the
`display. The two sensors are fastened by suction cups to
`the inside and outside of the pane. In this manner, the
`sensors can be mounted simply and reliably to the pane
`without the user of the device having to climb into the
`vehicle.
`Since the device measures the unattenuated intensity
`of daylight at the outside of the pane and uses it as a
`reference value, the device is independent of the light
`intensity of the daylight, in other words, of the bright
`ness at any given time. When the brightness of daylight
`fluctuates greatly, only the ampli?cation factor of the
`device need be changed.
`Of course, the device can be used for purposes other
`than measuring the shading of motor vehicle panes. It is
`equally suitable for measuring the shading of any trans
`parent pane-shaped objects.
`Further features and advantages of the invention will
`be apparent from the description which follows with
`reference to the drawing.
`
`BRIEF DESCRIPTION OF THE DRAWING
`FIG. 1 shows a view of the housing of the device
`approximately full size,
`FIG. 2 is an enlarged section through the photoelec
`tric sensor to be mounted on the outside of the motor
`vehicle pane,
`.
`FIG. 3 shows a drawing of the sensor to be mounted
`on the inside of the vehicle pane,
`FIG. 4 is a block diagram of the device, and
`FIGS. 5, 5A and 5B show the schematic of the de
`vice.
`DESCRIPTION OF PREFERRED EMBODIMENT
`The device in the embodiment shown in the‘drawing
`is used to measure the shading of motor vehicle panes
`that are coated with a shading ?lm.
`
`10
`
`PRIOR‘ ART
`US. Pat. No. 4,037,972 (Pross) describes a pocket
`device for measuring the transparency of a liquid to test
`its composition. A cell containing the liquid is inserted
`in the light path between a light source and a photoelec
`tric element of the device. A second photoelectric ele
`ment in the device serves as a reference for measuring
`the unattenuated intensity of the light source. A differ
`ential ampli?er compares the light intensity measured
`by the true photoelectric elements.
`US Pat. No. 4,236,826 (Y amanishi) describes a de
`vice for measuring the optical characteristics of a pane
`shaped object, especially its optical density. The subject
`is placed in the light path between a ?ashlamp source
`and a photodiode. The exponential decrease in light
`intensity from the ?ashlamp source is used to measure
`the optical density.
`German Patent Application 27 57 196 describes a
`device for measuring the re?ection and transmission of
`a pane-shaped object. The object is placed between
`30
`photometer spheres and traversed by a beam from a
`light source. One photometer sphere measures the re
`?ected intensity while the other measures the the trans
`mitted intensity.
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`BACKGROUND OF THE INVENTION
`Films are available on the American market which
`can be applied to the panes of a motor vehicle to shade
`said panes. The automobile owner can thus provide any
`shade for his vehicle panes. However, there are legal
`guidelines ‘in the US. for the shading permitted on
`motor vehicle panes. To enable the police to maintain
`these guidelines, a device is required which can measure
`the shading of vehicle panes. For this purpose, the de
`vice must not require an external power source, must be
`lightweight and portable, and must be easy to use. In
`addition, the device must permit rapid reliable measure
`ment without the policeman using the device having to
`get into the vehicle.
`The devices known from the prior art are not suitable
`for this purpose. These devices require a separate light
`source which has a high energy consumption so that it
`requires an external power source. In addition, in these
`known devices, the pane must be located between the
`light source and the photoelectric element of the device
`so that the known devices are suitable only for measur
`ing small samples. Finally, the attenuation of the trans
`mitted light in the range of the spectrum that corre
`sponds to the spectral sensitivity of the human eye is
`critical for the effect of the shading of the motor vehicle
`panes. Known devices measure an “objective” attenua
`tion of the light in the pane while “subjective” attenua
`tion for the human eye is important for measuring shad
`ing of the motor vehicle panes.
`
`45
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`OBJECT OF THE INVENTION
`The object of the invention is therefore a device for
`measuring the shading of panes, which does not require
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`located in front of the latter, are located in the immedi
`To measure the shading, one photoelectric sensor is
`ate vicinity of the vehicle pane when rubber suction cup
`placed outside the vehicle pane and the other, inside.
`118 is fastened to the latter. Cable 116 connected to
`The externally mounted sensor F1 measures the inten
`photodiode 122 is brought out rearward from sensor
`sity of the illumination of the daylight striking the panel
`receptacle 120 and held in place by means of a locking
`as a reference value. The internally mounted sensor F2
`measures the brightness of the daylight passing through
`screw 128.
`FIG. 4 shows the schematic diagram of the device
`the pane and the shading ?lm. The attenuation of the
`and the measurement principle. The light intensities
`daylight passing through and hence the shading of the
`measured by outer sensor F1 and inner sensor F2 are
`pane is calculated from the two measured values.
`sent to a subtracter 130 which determines the difference
`The device has a housing 110 as shown in FIG. 1.
`between the two measured values. The differential
`Housing 110 contains a digital LC display 112 for dis
`playing the measured shading. The housing also con
`value and the measured value of outer sensor F1 are fed
`as a reference value to a multiplier 132. Multiplier 132
`tains a rotary knob switch 114 used to turn off the de
`calculates the percentage attenuation of the light on
`vice and to set different light intensities for the daylight.
`passing through the shaded vehicle pane. The attenua
`Housing 110 is connected by cable 116 with one exter
`tion value, present in the form of voltage, is converted
`nal photoelectric sensor F1 and one internal photoelec
`into a digital value by an analog/digital converter 134
`tric sensor F2. FIG. 1 shows housing 110 on a scale of
`and the value is then displayed on LC display 112.
`1:1.
`FIG. 5 shows the entire circuit of the device in detail.
`In FIG. 2, outer photoelectric sensor F1 (and in FIG.
`The device is powered by a 9-volt battery with a
`3, inner photoelectric sensor F2) are shown on an en
`capacity of 0.5 Ah. With a current draw of approxi
`larged scale in an axial section. The sensors can use
`mately 15 mA for the entire circuit, the device has a
`photodiodes or phototransistors. In the embodiment,
`maximum operating time of approximately 10 hours. If
`sensors F1 and F2 each have a silicon-PN-planar photo
`diode (Telefunken model BPW21). These photodiodes
`it takes about 30 seconds for one measurement, approxi
`mately 1200 measurements can be made with one bat
`have an integrated ?at window with built-in color cor
`tery. This means that the device requires no external
`rection ?lter. The color correction ?lter adjusts the
`sensitivity of the photodiode to the sensitivity of the
`power source, is easy to handle, and can be used for a
`very long time without changing batteries.
`human eye in the visible range of the spectrum.
`In order to generate the required negative voltage of
`According to the legal provisions applicable in the
`-9 V from the supply voltage of +9 V of the battery,
`U.S., a police officer may not enter a vehicle during the
`21 negative voltage source 136 is provided. The circuit of
`measurement. However, in order to ensure an exact
`negative voltage source 136 is known and uses a mono
`measurement, the two sensors F1 and F2 must be
`lithic CMOS voltage converter (Intersil ICL 7662).
`mounted on the vehicle pane so that their light entrance
`To generate an exact reference voltage for monitor
`angles match. For this purpose, sensors F1 and F2 are
`ing and calibrating the device, a reference voltage
`mounted on suitably long cables 116; in addition, sen
`source 138 is provided which uses a reference diode
`sors F1 and F2 can be attached to the pane with rubber
`(National Semiconductor LM 336) as the reference
`suction cups. The two sensors F1 and F2 are mounted
`element.
`so that the outer circumferences of their respective
`To generate the voltage signals corresponding to the
`suction cups are aligned. This ensures that the angles of
`individual light intensities, which can then be processed
`incidence for the light are as similar as possible for both
`40
`further, a current-voltage converter 140 is used. The
`sensors and also that externally mounted sensor F1 does
`photodiodes (model BPWZl) of the two photoelectric
`not shade internally mounted sensor F2.
`sensors F1 and F2 are operated without bias voltage
`As FIG. 2 shows, photoelectric sensor F1, which is to
`with one operational amplifier (op amp) each (i LM
`be mounted externally, has a cup-shaped rubber suction
`324), wired as a current-voltage converter. The op amps
`cup 118 mounted externally on the vehicle pane. A
`45
`convert the short circuit current generated by the indi
`sensor receptacle 120 is mounted on the back of suction
`vidual photodiodes, which is proportional to the inten
`cup 118; photodiode 122 with the color correction ?lter
`sity of the illumination, by means of built-in feedback
`is mounted in sensor receptacle 120 and covered on the
`resistors R1 to R6 into a corresponding voltage. In
`side for which the light enters by a diffusing disk 124.
`Diffusing disk 124 homogeneously distributes the inci
`order to ensure that the device will be usable at all times
`of day, the entire range of possible illumination intensi
`dent light ?ux over photodiode 122. In addition, using
`diffusing disk 124_lowers the spectral sensitivity of pho
`ties from 400 to 200,000 lux is covered. Three feedback
`resistors with values of 390 k!) (R1 to R4), 39 k0 (R2 to
`todiode 122. Photodiode 122 therefore reacts to
`changes in the light ratio and slight angle changes be
`R5) and 6.2 k!) (R3 to R6) can be switched in alternated
`by means of rotary knob switch 114. These different
`tween the two sensors F1 and F2 with less sensitivity. In
`feedback resistors provide measurment ranges for illum
`addition, diffusing disk 124 absorbs the UV radiation in
`ination intensities from 400 lux to 3500 lux, from 3500
`the daylight to a large extent ‘so that photodiode 122
`lux to 35,000 lux, and from 35,000 lux to 200,000 lux.
`with its color correction filter is even better adapted to
`The two output voltage signals from current-voltage
`the sensitivity of the human eye. Cable 116 which leads
`to housing 110 is connected to photodiode 122 held in
`converter 140 are fed to subtracter 130. Subtractor 130
`forms a difference of the voltages from the two sensors
`sensor receptacle 120 by means of a photodiode holder
`F1 and F2 by means of an op amp } LM 324. Output AF
`126.
`~
`of subtracter 130 is fed to multiplier 132 while the out
`FIG. 3 shows sensor F2 to be fastened on the inside of
`put of the op amp of outer sensor F1 is fed as a reference
`the vehicle pane. Sensor F2 also has a rubber suction
`value through a voltage follower 142 to multiplier 132.
`cup 118 for fastening to the vehicle pane. However, in
`Voltage follower 142 which has an op amp l LM 324
`sensor F2 sensor receptacle 120 extends into rubber
`suction cup 118 so that photodiode 122 fastened by
`ensures that the output of the op amp of outer sensor F1
`means of photodiode holder 126 and diffusing disk 124
`is not too heavily loaded.
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`second mounting means for mounting said second
`Multiplier 132 calculates the value ‘AF/F 1X 100 with
`sensor means on the interior side of the pane with
`the aid of an analog multiplier (RC 4200) made by the
`said photosensitive surface of said second sensor
`Raytheon Company. This multiplier multiplies the input
`means facing the interior side;
`currents corresponding to voltage signals AF and 100
`a housing; and
`and divides them by the input current corresponding to 5
`electronic circuit means disposed in said housing and
`the voltage signal F1. Voltage signal 100 is generated by
`electrically connected to said ?rst and second sen
`a voltage divider and an op amp 1 LM 324. A trim pot
`sor means for calculating the difference of said
`Tr 1 wired into the voltage divider is used for adjust
`output signals of said ?rst and second sensor means,
`ment. The output current from the multiplier is con
`calculating the ratio of the difference of said output
`verted by an op amp OP07. into a corresponding output
`signals to said signal from said ?rst sensor means,
`voltage. A voltage divider with a trim pot TR2 is used
`and displaying the ratio as a reference value.
`to adjust the o?'set of the op amp.
`2. The device of claim 1, each of said ?rst and second
`The output voltage from multiplier 132 is fed to A/D
`sensor means comprising a photoelectric element hav
`converter 134 which converts the analog voltage value
`ing color correction ?lter means for adjusting the spec
`into a digital value. The A/D converter is a 3% position
`tral sensitivity of said photoelectric element to the spec
`monolithic A/D converter of the ICL 7106 type made
`tral sensitivity of the human eye.
`by Intersil. This A/D converter is a CMOS A/D con
`3. The device of claim 2, said photoelectric element
`verter in which all the required active elements such as
`comprising a photodiode.
`the BCD 7-segment decoder, driver stages for the dis
`4. The device of claim 1, each of said ?rst and second
`play, reference voltage, and clock are all on one chip.
`sensor means having a diffusing disk in front of said
`A/D converter 134 drives LC display 112 which con
`photosensitive surface.
`sists of an SP521 LC display.
`5. The device of claim 1, said ?rst and second mount
`If an illumination intensity range is selected while
`ing means each comprising a rubber suction cup.
`measuring using rotary knob switch 114 that results in
`6. The device of claim 1, said electronic circuit means
`overdriving the input ampli?er, LC display 112 shows a
`comprising:
`.
`?ashing “+” symbol. An overdrive display 144 is used
`a subtractor having an input and generating an output
`signal, said subtractor input receiving said input
`for this purpose. If the input stage of the current-voltage
`signals from said ?rst and second sensors;
`converter 140 exceeds a voltage level of 5.5 V, over
`drive display 144 generates a clock frequency by which
`a multiplier having an input and generating an output
`signal, said multiplier input receiving said output
`the display segments with a “+” symbol are controlled.
`signal from said subtractor and said output signal
`The overdrive display consists of a comparator and a
`pulse generator. The comparator is formed by an op
`from said ?rst sensor; and
`an analog-to-digital converter having an input and
`amp i LM 324 which is wired as a voltage-controlled
`generating an output signal, said converter input
`switch (Schmitt trigger) by means of a feedback to the
`receiving said output signal from said multiplier.
`inverting input. The output of the comparator controls
`7. The device of claim 6 said electronic circuit means
`the pulse generator which is in the form of a square
`comprising an LC display disposed in said housing and
`wave generator using an inverting voltage-controlled
`having an input, said display input receiving said output
`switch. The minus input of an op amp 1 LM 324 is
`signal from said analog-to-digital converter.
`connected to a capacitor C4 for this purpose which is
`8. The device of claim 1, further comprising ?rst and
`charged and discharged through a resistor R32 by the
`second ampli?er means for amplifying said output sig
`ampli?er output. The output amplitude of the square
`nals of said ?rst and second sensor means, respectively,
`wave generator is fed via a voltage divider to the input
`each of said ?rst and second ampli?er means having a
`of an EX-OR element (CD 4030) which controls the
`switchable ampli?cation factor.
`“+” character on LC display 112.
`9. The device of claim 8, further comprising a rotary
`If the supply voltage from the battery drops below
`knob switch operatively connected to said ?rst and
`7.5 V the display “Lo Bat” appears at the upper left of
`45
`second ampli?er means, said ampli?cation factors of
`LC display 112. This is produced by a comparator cir
`said ?rst and second ampli?er means being commonly
`cuit 146 with an op amp i LM 324. The value of +5 V
`switchable by said rotary knob switch.
`is used as the reference voltage. The second input volt
`10. The device of claim 8, further comprising:
`age divider is dimensioned so that a voltage value of + 5
`an overdrive display disposed in said housing and
`V is applied to the minus input of the op amp below a
`overdrive circuit means electrically connected to said
`supply voltage of 7.5 V. If the voltage drops below this
`overdrive display and said ?rst and second ampli
`value, the op amp changes its output voltage and con
`?er means for controlling said overdrive display as
`trols the “L0 Bat” segment of ‘LC display 112 through
`soon as said ?rst and second ampli?er means are
`the EX-OR element (CD 4030).
`overdriven.
`11. The device of claim 10, said overdrive display
`I claim: _
`1. A device for measuring the shading of a translucent
`comprising ?ashing segments of and LC display con
`pane having an exterior side and an interior side, com
`trolled by said overdrive circuit means.
`prising:
`12. The device of claim 1, further comprising. a bat
`frst and second photoelectric sensor means for mea
`tery disposed in said housing, said electronic circuit
`suring unattenuated daylight and attenuated day
`means being powered by said battery.
`light, respectively, and generating an output signal
`13. The device of claim 12, further comprising:
`proportional thereto, each of said sensor means
`a low battery display disposed in said housing and
`having a photosensitive surface and a spectral sen
`comparator circuit means for comparing the voltage
`sitivity substantially corresponding to the spectral
`of said battery with a minimum voltage and activat
`sensitivity of the human eye;
`' ing said low battery display as soon as the battery
`voltage drops below the minimum voltage.
`?rst mounting means for mounting said ?rst sensor
`14. The device of claim 1, said housing being pocket
`means on said exterior side of the pane with said
`sized.
`photosensitive surface of said ?rst sensor means
`facing away from said exterior side;
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`* i * * *
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