Electronic sunglasses

Electronic sunglasses of the transmittance-varying type including liquid crystal panels employing the electro-optical effect and a solar cell used as a power source. The electronic sunglasses include a voltage detecting circuit having such a hysteresis characteristic so as to output a signal for changing transmittance of the liquid crystal panel from a high mode to a low mode at at least high predetermined voltage or illumination, and changing transmittance from a low mode to a high mode at at least a low voltage or illumination. The sunglasses also include a first switch which operates at at least two switch positions, one switch position having a first stage of illumination at less than 20,000 Lux and a second stage of illumination at 20,000 Lux or greater at which transmittance is changed from a high mode and another switch position disabling the voltage detecting circuit. Also included is a second switch which operates to change transmittance from a high mode to a low mode independently of the set voltage value in the voltage detecting circuit according to the hysteresis effect.

BACKGROUND OF THE INVENTION 
The present invention relates generally to electronic sunglasses, and, in 
particular, to transmittance-varying sunglasses which employ the 
electro-optical effect of a liquid crystal material and a solar cell which 
serves both as a power source for driving the liquid crystal and as a 
sensor for detecting the quantity of ambient light. 
The provision of transmittance-varying sunglasses using a liquid crystal 
material has been proposed in various publications. The general concept 
has been illustrated in, for example, in FIG. 1 of Japanese Patent First 
Publication No. Showa 48-98846, FIG. 3 of Japanese Patent First 
Publication No. Showa 51-124936, FIG. 1 of Japanese Utility Model First 
Publication No. Showa 62-127524, FIGS. 5 and 7 of Japanese Patent First 
Publication No. Showa 62-40425, FIG. 1 of Japanese Utility Model First 
Publication No. Showa 55-95106, FIG. 1 of Japanese Utility Model First 
Publication No. Showa 59-178618, and FIG. 1 of Japanese Utility Model 
First Publication No. Showa 62-109137. As has been understood from these 
examples, such electronic sunglasses are composed of a liquid crystal 
panel serving as a transmittance-varying section, a power source, a 
driving circuit, a control circuit, and an optical detecting section. 
However, these prior art constructions have proved less than completely 
satisfactory for the following reasons. 
Considering transmittance-varying sunglasses employing the electro-optical 
effect of liquid crystal and using a solar cell as a power source, the 
prior art sunglasses include a circuit for detecting an electromotive 
force of the solar cell and switching the transmittance mode according to 
the amount of ambient light. In the case where the operating illumination 
of the liquid crystal panel is the same as the stopping illumination, the 
received illumination is often varied according to the changing 
orientation of a user and obstacles which screen the light from the sun 
rays, resulting in frequent switching of the liquid crystal panel from an 
operation mode to a stop mode or vice versa and varying transmittance of a 
lens. This frequent variation is a great annoyance to a user. 
It is very important to set an illumination at which transmittance is 
varied. Hence, unless the illumination is properly set, the change of 
transmittance is not performed in a preferable illumination, resulting in 
annoyance to a user. To set the illumination properly, the prior art 
devices provide a means for varying the resistance value in a circuit, 
which makes it possible to set an illumination. Yet, it is very 
troublesome to arrange a variable resistor according to the environment in 
which the sunglasses are used. No constructions have been proposed for 
setting a user-friendly illumination at which transmittance is changed. 
Further, in the case of setting a proper illumination, in some conditions, 
it may be desirous to make transmittance lower below the set illumination 
to change the transmittance from a high mode to a low mode or to make 
transmittance higher over the set illumination to change the transmittance 
from a low mode to a high mode. This means that it is insufficient to 
provide the change of transmittance at the two stages of a high mode to a 
low mode or vice versa of the received illumination. This is a relevant 
shortcoming to be overcome. 
Except for the system for switching the liquid crystal panel on or off at 
the set illumination as mentioned above, there have been other systems for 
arranging transmittance by continuously changing a voltage applied to the 
liquid crystal panel according to the quantity of outside light and for 
arranging transmittance by changing a ratio of an on time to an off time 
during one period of a pulse to be applied to the liquid crystal according 
to the quantity of outside light. These systems, however, are not 
effective in some conditions. For example, an uneven density appears on 
the liquid crystal panel by changing dependency on a view point based on 
the change of a voltage applied to the liquid crystal. When, for example, 
a user drives through the woods by car, that is, the quantity of ambient 
light is abruptly and frequently changed, the transmittance is frequently 
changed. This frequent change is a great annoyance to the user. 
Accordingly, it is desired to provide electronic sunglasses which are 
capable of preventing frequent change of transmittance, allowing proper 
setting of the set illumination according to the situation with one touch, 
and changing transmittance according to a user's will. 
SUMMARY OF THE INVENTION 
Generally speaking, in accordance with the present invention, electronic 
sunglasses of the transmittance-varying type including liquid crystal 
panels employing the electro-optical effect and a solar cell used as a 
power source, are provided. The electronic sunglasses include a voltage 
detecting circuit having such a hysteresis characteristic so as to output 
a signal for changing transmittance of the liquid crystal panel from a 
high mode to a low mode at at least a high predetermined voltage or 
illumination, and changing transmittance from a low mode to a high mode at 
at least a low voltage or illumination. The sunglasses also include a 
first switch which operates at at least two switch positions, one switch 
position having a first stage of illumination at less than 20,000 Lux and 
a second stage of illumination at 20,000 Lux or greater at which 
transmittance is changed from a high mode to a low mode and another switch 
position disabling the voltage detecting circuit. Further, the sunglasses 
include a second switch which operates to change transmittance from a high 
mode to a low mode independently of the set voltage value in the voltage 
detecting circuit according to the hysteresis effect. 
Accordingly, it is an object of the present invention to provide improved 
electronic sunglasses. 
Another object of the present invention is to provide electronic sunglasses 
which are capable of preventing frequent change of transmittance. 
A further object of the present invention is to provide electronic 
sunglasses which permit proper setting of the set illumination in a simple 
fashion. 
Yet another object of the present invention is to provide electronic 
sunglasses in which transmittance can be changed according to a user's 
desire. 
Still other objects and advantages of the invention will in part be obvious 
and will in part be apparent from the specification. 
The invention accordingly comprises the features of construction, 
combinations of elements, and arrangement of parts which will be 
exemplified in the constructions hereinafter set forth, and the scope of 
the invention will be indicated in the claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
When determining the difference between illumination at which transmittance 
is switched on and illumination at which transmittance is switched off, 
there is employed a system for dividing a voltage of a solar cell, 
detecting a voltage set by a voltage detecting circuit, and driving the 
liquid crystal thereby. Such system may be used with a system which 
includes a capacitor connected with the voltage detecting section of the 
voltage detecting circuit in parallel for delaying the transmittance from 
a low mode to a high mode on time and taking a difference between the 
illuminations at which transmittance is varied, as well as a system for 
making the operating voltage of the voltage detecting circuit hysteretic. 
For defining a proper illumination at which transmittance is changed from a 
high mode to a low mode, the illumination is measured and the way of use 
is researched in several locations as set forth in Table 1 below. 
TABLE 1 
______________________________________ 
PLACE WEATHER ILLUMINATION 
______________________________________ 
Inside of Automobile 
Clear 6,000 Lux 
Inside of Automobile 
Cloudy 1,000 Lux 
Inside of Tunnel 50 Lux 
Inside of Automobile 
Clear (direct 
15,000 Lux 
sun) 
Skiing Ground Clear 80,000 Lux 
Skiing Ground Cloudy 15,000 Lux 
Lift Stop Clear 5,000 Lux 
Lift Stop Cloudy 8,000 Lux 
______________________________________ 
The foregoing researched results indicate that the using condition in a car 
is quite different from the condition on a skiing ground so that the 
single illumination does not conform to any one place. The table also 
indicates that the proper illumination at which transmittance is changed 
from a high mode to a low mode is less than 20,000 Lux in driving a car 
and 20,000 Lux or more in the skiing ground. In case the user is looking 
out of the car window in driving a car, the transmittance has to be 
changed at a relatively low illumination. In case of setting high 
illumination, the transmittance is not changed in a glaring place. On the 
other hand, in case of setting a low illumination on the skiing ground, 
the irregular reflection of sun rays on snow serves to change 
transmittance even on a cloudy day. For achieving convenient and practical 
electronic sunglasses, the set illumination is required to change in any 
used places. 
The present invention may provide an additional switch for disabling the 
switching circuit. For example, when the user drives a car through woods 
or through a city, that is, where illumination is abruptly changed, the 
difference of illumination between a shady spot and a sunny spot is quite 
large. This results in causing the sunglasses to switch on and off. This 
would be quite annoying to a user. In such places, it is convenient for a 
user to disable the switching circuit as desired. 
The illumination at which transmittance is changed from a low mode to a 
high mode should be preferably 6,000 Lux or less. If the illumination at 
which transmittance is changed from a low mode to a high mode is 6,000 Lux 
or less, the difference between the on illumination and the off 
illumination becomes quite sufficient, thereby causing a time lag about 
the change of transmittance. Hence, the frequent change of transmittance 
is prevented in the spot at which illumination is changed instantly. The 
change of the set illumination can be easily realized by the change of a 
resistance value in the circuit. 
The switch for changing transmittance from a high mode to a low mode or 
vice versa irrespective of the set voltage value in the hysteresis area 
can be realized by a switch for short-circuiting or opening a resistance 
which serves to divide a voltage in the voltage detecting circuit. 
In case of setting a voltage value for detecting the operation of the 
liquid crystal panel at a high mode, setting a voltage for detecting the 
stop thereof at a low mode, and using the solar cell output for a sensor, 
the illumination at which the liquid crystal panel is operated is made 
higher and the illumination at which it is stopped is made lower. 
The difference between the operating illumination and the stopping 
illumination brings about no change of the liquid crystal panel against 
the small change of illumination based on the orientation of a user when 
the sunglasses are operated. Hence, the illumination is not kept switched 
on and off, resulting in being an annoyance to a user. Like the stopping 
case, the difference between the operating illumination and the stopping 
illumination brings about no annoying on-and-off switching of 
illumination. 
FIG. 1 shows the operation-stopping state of electronic sunglasses 
according to the present invention. The liquid crystal panel is operated 
at the high illumination value (b), then changing transmittance from a 
high mode to a low mode. Next, in case of reducing the quantity of outside 
light, the low transmittance is kept to the lower illumination value (a). 
When the illumination reaches the low value, the transmittance is changed 
from a low mode to a high mode. That is, the orientation of illumination 
change depends on the path of transmittance, resulting in giving a 
hysteresis characteristic. 
As shown in FIG. 1, there exist high and low transmittances at a given 
illumination. By providing a switch for switching a voltage applied to the 
voltage detecting circuit (c), the voltage which is higher than the high 
set voltage value or lower than the low set voltage value is forcibly 
applied, thereby the transmittance is changed to a lower or higher state. 
In FIG. 1, a point where the transmittance of the liquid crystal panel is 
high shows the case where the liquid crystal panel is in the standing 
condition and the transmittance from the outside is large. On the other 
hand, a point where the transmittance is low shows the case where the 
liquid crystal panel is in the working condition and the transmittance 
from the outside is small. If an illumination from the outside increases 
more than a high set value (b) when the liquid crystal panel is in the 
standing condition, the condition switches to the working condition from 
the standing condition. If the illumination from outside decreases lower 
than a low set value (a) when the liquid crystal panel is in the working 
condition, the condition switches to the standing condition from the 
working condition. 
As discussed above, in the electronic sunglasses according to the present 
invention, the high set voltage (b) for turning the liquid crystal panel 
from the standing condition to the working condition is differentiated 
from the low set voltage (a) for switching from the working condition to 
the standing condition, thereby actuating the liquid crystal panel by a 
hysteresis characteristic by means of the passes between (a) and (b) of 
FIG. 1. By actuating the liquid crystal panel by the hysteresis 
characteristic, it is possible to obtain the stable working condition and 
standing condition without any reaction with a movement of the user's line 
of sight and a little variation of the solar rays. 
Further, when the illumination from outside belongs to an environmental 
illumination, which is the voltage between (a) and (b), the voltage whose 
value is more than high set voltage (b) or whose value is less than low 
set voltage (a) is applied to the liquid crystal panel by force, thereby 
switching the liquid crystal panel from the standing condition to the 
working condition when the value is higher than the high set value, and, 
switching from the working condition to the standing condition by force 
when the value is lower than the low set value. As described above, the 
condition of the liquid crystal panel is switched by force in addition to 
the basic mode, thereby providing improved electronic sunglasses in which 
it is possible to exhibit the advantageous feature of sunglasses even in 
the case where the illumination from outside varies greatly. 
Hereinafter, the detailed description will be directed to embodiments of 
the present invention. It is noted, however, that the present invention is 
not limited to these embodiments. 
EMBODIMENT 1 
FIG. 2 is a view showing the outer appearance of a first embodiment of the 
invention. Electronic sunglasses, generally indicated at 100, include a 
solar cell 1, right and left lenses 2 with a liquid crystal cell, a switch 
3 for switching a set illumination, and a touch switch 4 for forcibly 
switching the illumination on. 
FIG. 3 is a circuit diagram showing the circuitry used in this embodiment. 
The circuit includes solar cell 1, lens 2 with a liquid crystal cell, a 
set illumination-switching switch 3, a touch switch 4, a voltage detecting 
circuit 5, an oscillating circuit 6, a liquid crystal driving circuit 7, 
voltage detecting resistors 8 and 9, a power source protective capacitor 
10, a capacitor 11 for delaying the timing of switching transmittance, and 
resistors 12 and 13 for giving hysteresis to the operating voltage of the 
voltage detecting circuit. 
The oscillating circuit 6 is a CR oscillating circuit and includes NAND 
gates 14, 15, a capacitor 16, and a resistor 17. Liquid crystal driving 
circuit 7 includes NAND gates 18, 19 for controlling an output and 
inverters 20 and 21. The construction of voltage detecting circuit is 
well-known and is not described here in detail. The power source 
protective capacitor 10 is coupled in parallel to the circuit. 
The electromotive force of solar cell 1 is divided by resistor 8 and 
resistor 9 connected in parallel to voltage detecting circuit 5. The 
detecting level of the voltage detecting circuit 5 is set as about 3V. If 
the voltage applied to the voltage detecting resistor 9 does not attain a 
level of about 3V, an output signal 22 becomes an off signal (L) and an 
equi-phase (L) voltage is applied to the liquid cell 2, resulting in 
disabling the liquid crystal cell 2. When the applied voltage exceeds 
about 3V of the voltage detecting level, the output signal 22 of the 
voltage detecting circuit 5 becomes an on signal (H), thereby the reverse 
phase a.c. signal of the oscillating circuit is applied to the liquid 
crystal cell. 
A driving frequency should be preferably several tens to several hundreds 
Hz defined by the resistor 17 and the capacitor 16. 
Since the resistors 12 and 13 bring about a hysteresis state in the voltage 
detecting circuit, they are used for making a difference between 
illuminations at which transmittance is changed from a high mode to a low 
mode and vice versa. The resistor is switched by the switch 3, thereby 
changing the illumination at which transmittance is changed from a high 
mode to a low mode. Further, the switch 3 provides a stable spot for 
grounding the voltage detecting circuit for disabling the circuit. 
The capacitor 11 serves to keep the circuit operated for a while even if 
the outside illumination is changed from a high mode to a low mode. This 
is effective in preventing the frequent change of transmittance of the 
lens, resulting in putting no annoyance to a user. 
The power source protective capacitor 10 should be about several tens .mu., 
it is used for removing noises and ripples supplied to the power source. 
The output of the solar cell is changed by the outside illumination as well 
as influenced by its outside mounted position. The present embodiment uses 
an amorphous silicon solar cell consisting of cell elements connected in 
series at the seven stages, the area of which is 0.8 cm.sup.2. Since the 
output of the solar cell is influenced by its outside mounted position, in 
general, it is difficult to define the values of the voltage detecting 
resistors 8, 9 and the resistors 12, 13. The present embodiment defines 
the resistor 12 as 1M.OMEGA., the resistor 13 as 480 k.OMEGA., the voltage 
detecting resistors 8 and 9 respectively as 220 k.OMEGA. and 1M.OMEGA. in 
a manner to allow the circuit to operate when the outside illumination is 
15,000 Lux or 40,000 Lux. 
The liquid crystal panel is designed as follows. The liquid crystal panel 
comprises a film substrate made of a synthetic resin including an 
electrode surface made of an ITO film, which substrate is subject to 
orientation treatment and nematic liquid crystal having a proper amount of 
added right-spinning chirality material. .DELTA.n (refractive anisotropy) 
is 0.07g sealed to keep the distance 7.mu. between the substrates together 
with a gap agent being scattered. The rubbing direction of the opposite 
substrate forms an angle of 110.degree.. Then, light-polarizing plates are 
pasted from both sides in a manner to allow the absorption axes of these 
plates to match to the rubbing direction of the substrate. The absorption 
axis of the front light-polarizing plate is built in a sunglass frame in a 
manner to allow the right eye of the axis to be in parallel to the left 
eye of the axis. 
Since the liquid crystal panel obtained above is weak in strength and 
easily damaged in using the panel as the transmittance-varying section of 
the sunglasses, polycarbonate plates whose thickness is 0.5 mm are 
connected on both sides of the panel with an ultraviolet rays hardening 
type adhesive agent. On the non-adhesive outside surface of the 
polycarbonate plate is provided a hard coat layer for hardening. 
The transmittance-varying section designed as mentioned above has a 
transmittance of 8.11% when a voltage is applied (5V static) and 35% when 
no voltage is applied. 
The electronic sunglasses are designed by incorporating the above-mentioned 
lens section connected with the liquid crystal panel and circuit section 
into a frame. 
Researching the on-off illumination as changing the outside illumination, 
for the on illumination, the illumination is 14800 Lux when the resistor 
12 is switched on and it is 42,000 Lux when the resistor 13 is switched 
on. For the off illumination, the illumination is 2,500 Lux. And, in case 
of using the touch switch, the resistor 8 is short-circuited in a manner 
to allow the user to turn on the circuit at the off illumination or more. 
EMBODIMENT 2 
The second embodiment is designed to operate switching of an operating 
illumination by varying the resistor 8 in embodiment 1. This embodiment is 
basically the same as embodiment 1 except that the resistor 12 for giving 
hysteresis to the voltage detecting circuit is defined as 1M.OMEGA. and 
the resistor 8 can be selected from 150k.OMEGA. and 230k.OMEGA.. FIG. 4 
shows the circuit diagram of embodiment 2. Like elements from FIG. 3 are 
numbered alike. 
Researching the on-off illumination as changing the quantity of outside 
light, when the resistor 8 is defined as 150k.OMEGA., the transmittance is 
changed from a high mode to a low mode at 10,000 Lux and from a low mode 
to a high mode at 5,000 Lux. When the resistor 8 is defined as 
230k.OMEGA., these changes are done at 30,000 Lux and 6,000 Lux, 
respectively. 
EMBODIMENT 3 
This embodiment employs a lens made of diethylene glycol visallyl carbonate 
resin in place of a flat polycarbonate plate whose thickness is 0.5 mm. It 
is denoted as a transmittance-varying section contained in a lens. The 
lens is produced by a thermal polymerization method. The lenses are pasted 
on an objective side and an eye side of the liquid crystal panel, thereby 
providing the degrees as a whole. The lens pasted on the objective side 
has a convex curvature radius of 13 cm, an indefinite concave curvature 
radius (that is, plane), and a central thickness of 5 mm. The lens 
connected on the eye side has an indefinite convex curvature radius, a 
convex curvature diameter of 10 cm, and a central thickness of 1 mm. The 
degrees of the transmittance-varying section designed as mentioned above 
were measured as -1,14 diopters. 
Like embodiment 1, this transmittance-varying section and the circuit are 
incorporated in a frame, resulting in a pair of sunglasses. 
As mentioned above, according to the present invention, the set 
illumination is changed with one touch according to the circumstances 
under which the sunglasses are used. The illumination is switched on and 
off by the high set voltage and the low set voltage so as to make the 
circuit hysteretic. The invention provides a switch for forcibly changing 
the transmittance in the range, resulting in providing no disgusting 
repetition of changing the transmittance from a high mode to a low mode or 
vice versa. Hence, the change of transmittance is performed according to a 
user's demand. Further it goes without saying that the present invention 
may be applied to not only electronic sunglasses but also to an electronic 
sunvisor and to an electronic shield of a motorcycle, for example. 
It will thus be seen that the objects set forth above, among those made 
apparent from the preceding description, are efficiently attained and, 
since certain changes may be made in the above constructions without 
departing from the spirit and scope of the invention, it is intended that 
all matter contained in the above description or shown in the accompanying 
drawings shall be interpreted as illustrative and not in a limiting sense.