Shutter synchronization circuit for stereoscopic systems

A shutter synchronization circuit for a stereoscopic system, which comprises a CPU, a main memory, a VGA graphic card, a monitor, a RS 232 interface circuit, an interrupt controller, a timer and an external shutter synchronizer with RS 232 interface; the circuit is to be used in personal computers; by using the RS 232 interface and the external shutter synchronizer with RS 232 interface, the switching of the LCD shutter and the vertical synchronization scanning signal of the VGA graphic card can be in synchronization. By using a hardware system of a stereoscopic image, a user can see a stereoscopic scene instead of a plane image.

BACKGROUND OF THE INVENTION 
As a result of the highly developed technology and the multi-medium time 
approaching, the technique of three-dimensional stereoscopic system has 
been used gradually in personal computers; particularly, a stereoscopic 
display device has become one of the peripheral equipment of the personal 
computers because of stereoscopic image being widely used. Currently, a 
low cost and simple LCD shutter eye-glasses together with a hardware 
equipment can be emerged out of various types of stereoscopic image 
devices, and they can easily be accepted by the general consumers. To have 
a stereoscopic image, the basic theory therefor is that the LCD shutter 
switching of the LCD shutter eyeglasses for a user can be in 
synchronization with the vertical synchronization scanning signal of a VGA 
drawing card; such technique can be done by means of a shutter 
synchronization circuit; however, the circuit of the conventional 
technique is either too complicated because of using a lot of parts which 
will increase the manufacturing cost, or such circuit being built in the 
main frame of a computer, i.e., the main frame has to be disassembled 
before to install such circuit; therefore, the design and manufacture for 
such a shutter synchronization circuit of a stereoscopic system will cause 
a quite number of difficulties, which should be improved. 
SUMMARY OF THE INVENTION 
This invention relates to a shutter synchronization circuit for a 
stereoscopic system, and particularly to a simple circuit designed for 
obtaining a synchronization between the LCD shutter switching and the 
vertical synchronization scanning signal of a VGA drawing card. 
The prime object of the present invention is to provide a shutter 
synchronization circuit by using a simple circuit to form into an external 
shutter synchronizer with RS 232 interface, and by combining a software 
program in a main memory, or a hardware device built in a main frame; the 
electronic circuit of the external shutter synchronizer with RS 232 
interface can be furnished separately, or can be furnished in connectors 
of the RS 232 interface, or in some peripheral equipment, such as a mouse 
controller, a keyboard or a control rod so as to overcome the inconvenient 
and complicated problems usually existed in the conventional circuit of 
the kind, and also to have the LCD shutter switching of the LCD shutter 
eye-glasses become synchronized with the display of the left and right 
images. 
Another object of the present invention is to provide a shutter 
synchronization circuit for a stereoscopic system, in which an interrupt 
controller is installed the main frame to receive a vertical 
synchronization interrupt signal out of a VGA drawing card; by using such 
signal, an interrupt request signal is sent to the main memory; by means 
of a software or a hardware device, the LCD shutter switching and the 
display of the left and right images can be in synchronization as desired. 
Still another object of the present invention is to provide a shutter 
synchronization circuit for a stereoscopic system, in which the main frame 
is added with an interrupt controller and a timer; the timer is used for 
constantly generating a signal by means of approximate and synchronous to 
a vertical synchronization scanning signal of VGA drawing card, and the 
aforesaid signal is sent to the interrupt controller to generate an 
interrupt signal, which is then sent to the main memory; further, by using 
a software or a hardware device, the LCD shutter switching and the display 
of the left and right images can be synchronized such other.

DETAILED DESCRIPTION 
Referring to FIG. 1, the embodiment of the present invention is shown with 
a perspective view, which comprises a main frame 10, a monitor 20, a VGA 
drawing card 12, a RS 232 interface circuit board 14, an external shutter 
synchronizer with RS 232 interface 30, and a wire-type LCD shutter 
eye-glasses 40. The main frame 10 together with the external shutter 
synchronizer with RS 232 interface 30 are used to enable the display time 
of the left picture and the right picture on the monitor 20 to be in 
synchronization with the LCD shutter switching of the wire-type LCD 
shutter eye-glasses 40 so as to provide a stereoscopic image for visual 
pleasure. 
Referring to FIG. 2, it is a block diagram of the embodiment-1 according to 
the present invention, showing the operation thereof, and it comprises a 
CPU 11, a main memory 50, a VGA drawing card 12, a monitor 20, an external 
shutter synchronizer with interface RS 232 30, a LCD shutter 42, and a RS 
232 interface 52. First, CPU 11 will have the left and right image data 
sent, through the main memory 50, to a display memory 121 of the VGA 
drawing card 12; then, the controller 122 of the VGA drawing card 12 will 
have the data of the left and right images converted, by means of RAMDAC 
123, into RGB analog signals, and these RGB analog signals are sent out 
into the monitor 20 alternatively; the monitor 20 will have the left and 
right images displayed on a screen respectively. In order to have the 
switching of the left and right LCD shutters 42 on the LCD shutter 
eye-glasses synchronized with the display time of the left and right 
images, the vertical retrace detecting program 58 of the application 
program 56 in the main memory 50 must first detect the vertical retrace 
condition (which is to be provided by the controller 122 of the VGA 
drawing card). If the scanning of the VGA drawing card 12 is under the 
vertical retrace condition, the vertical retrace detecting program 58 will 
send an output signal to the RS 232 interface 52; the RS 232 interface 52 
will, through DTR or RTS pin, send out a shutter switching signal to the 
external shutter synchronizer with RS 232 interface 30; by using the 
aforesaid signal, the external shutter synchronizer with RS 232 interface 
30 will actuate the LCD shutter driver 32, which will send out a LCD 
shutter driving signal to drive the LCD shutter 42 so as to have the 
switching of the LCD shutter in synchronization with the left and right 
image display time. Since synchronization between the switching of the LCD 
shutter 42 and the left and right image display are done by means of a 
software program, such method is referred to as a software type of 
synchronization. 
Referring to FIG. 3, the embodiment-2 according to the present invention is 
shown with a block diagram, of which the difference from the embodiment-1 
is that an interrupt controller 53 is added, and further a vertical 
synchronization interrupt program 55 is added to the application program 
56. The transmission and display procedure of the left and right image 
data are the same as that of the embodiment-1, and therefore no 
description is given. First, the controller 122 of the VGA drawing card 12 
sends out a vertical synchronization interrupt signal, which then passes 
through a computer bus-bar interface to trigger the interrupt controller 
53 (interrupt system) in the computer. According to the interrupt request, 
CPU 11 will transfer the program-execution control from the application 
program 56 to the vertical synchronization interrupt program 55; through 
the RS 232 interface 52, the vertical synchronization interrupt program 55 
will provide an output of shutter switching signal (via DTR or RTS pin) to 
the external shutter synchronizer with RS 232 interface 30. By means of 
such signal, the external shutter synchronizer with RS 232 interface 30 
will trigger the LCD shutter driver 32 to generate an output of LCD 
shutter driving signal to drive the LCD shutter so as to enable the LCD 
shutter 42 switching synchronously with the display of the left and right 
images. Since the switching of the LCD shutter 42 and the display of the 
left and right images are taking place synchronously by means of a 
hardware interrupt controller 53 (interrupt system) to perform such 
operation, it is referred to as a hardware type of synchronization. 
Referring to FIG. 4, it is a block diagram of another hardware type of 
synchronization embodiment according to the present invention; it is 
different from the embodiment-1 by adding an interrupt controller 53 and a 
timer 57; further, the application program 56 is added with a vertical 
retrace blanking program 51; the techniques for transmission and display 
of the left and right image data are the same as the embodiment-1, and 
therefore no description therefor are given. According to the embodiment, 
a computer timer 57 uses a frequency being approximately and synchronously 
to a vertical synchronization scanning signal of VGA drawing card to 
generate constantly an output signal sent to the interrupt controller 53 
for generating a interrupt signal constantly. According to the interrupt 
request, the CPU 11 will transfer the program-execution control from the 
application program 56 to the vertical retrace interrupt program 51; then, 
the vertical retrace interrupt program 51 can detect the vertical retrace 
condition (the vertical retrace is to be provided by means of the 
controller 122 of the VGA drawing card 12). If the VGA scanning is under a 
vertical retrace condition, the vertical retrace interrupt program 51 will 
through the RS 232 interface 52, send out a shutter switching signal (via 
DTR or TRS pin) to the external shutter synchronizer with RS 232 interface 
30, which will use such signal to trigger the LCD shutter driver 32 to 
send out a LCD shutter driving signal to actuate the LCD shutter 42 so as 
to have the CD shutter 42 switching and the display of the left and right 
images synchronized. 
The power supply and input signal for the external shutter synchronizer 
with RS 232 interface 30 are to be furnished by the pin of the RS 232 
interface 52; the electronic circuit thereof can be provided separately or 
included in the connectors of the RS 232 interface 52, or the circuit can 
also be furnished in the peripheral devices, such as a mouse controller, a 
control rod, or a keyboard. Further, the function of the RS 232 interface 
52 can be replaced with an output interface of a printer for receiving a 
shutter switching signal from the main memory to send the signal to the 
external shutter synchronizer with RS 232 interface 30; simultaneously, a 
power supply can be provided for the external shutter synchronizer with RS 
232 interface 30. 
Referring to FIG. 5, it illustrates a circuit block diagram of the external 
shutter synchronizer with RS 232 interface, and it includes a power supply 
301, an interface RS 232 buffer 302, a shutter switch 303 and a shutter 
controller 304; if the DTR of the RS 232 interface is used for supplying 
power to the external shutter synchronizer with RS 232 interface 30, the 
pin RTS will provide the external shutter synchronizer with RS 232 
interface 30 with a shutter switching signal, and vice versa. The power 
supply 301 of the external shutter synchronizer with RS 232 interface 30 
includes a voltage stabilizer and filter circuit, of which the function is 
to provide an output out of the DTR of the RS 232 interface for supplying 
a D.C., power for the external shutter synchronizer with RS 232 interface 
30. The RS 232 interface buffer 302 is used for isolating the RS 232 
interface 52 from the external shutter synchronizer with RS 232 interface 
30 so as to prevent from interference, i.e., the shutter switching signal 
out of the pin RTS of the RS 232 interface 52 would not have distortion as 
a result of the existence of the external shutter synchronizer with RS 232 
interface 30; therefore, the RS 232 interface buffer 302 will send a 
signal to the shutter controller 304. The shutter switch 303 includes a 
shutter manual switch 306 and a shutter condition indicator 305, and the 
function thereof is to enable or disable the output of a LCD shutter 
driving signal manually; if an enable function is required, the shutter 
manual switch 306 will send out an "enable" signal to the shutter 
controller 304; if a disable function is required, the shutter manual 
switch 306 will send out a "disable" signal to the shutter controller 304 
have an output of a LCD shutter driving signal or not in accordance with 
an enable or disable signal; finally, the shutter controller 304 will send 
an enable or disable signal to the shutter condition indicator 305, and 
then a user can know, through the shutter condition indicator 305, the 
using condition of the shutter eye-glasses. The shutter controller 304 
includes a LCD shutter driving signal generator 307 and a control circuit 
308; the prime function of the shutter controller 304 is to receive a 
shutter switching signal out of the RS 232 interface buffer 302; then, the 
shutter switching signal is used to trigger the left and right LCD 
shutters; simultaneously, the shutter controller 304 also sends out a 
driving signal so as to have the switching of the left and right LCD 
shutter become synchronized with the display of the left and right images. 
By means of the enable/disable signals out of the shutter switch 303, the 
LCD shutter can be determined whether it is to be driven or not. 
Referring to FIG. 6, it illustrates the various input and output signals of 
the external shutter synchronizer with interface RS 232; if the RTS sends 
out a shutter switching signal through the RS 232 interface buffer 302, 
and if the shutter switching signal is in high state, it indicates a 
period of time that the VGA displays the left image (.DELTA.t stands for 
the scanning time for a single image). When the shutter switching signal 
is in low state, it indicates a period of time that VGA displays the right 
image, and vice versa. When the driving voltage of the LCD shutter is at 
zero, it indicates the shutter being in a transparent state. When the 
driving voltage (the rectangular driving signal of LCD shutter) is 
activated, it indicates the shutter being in shutoff state, and vice 
versa. Moreover, the rectangular driving signal of LCD shutter out of the 
LCD shutter driving signal generator 307 and the enable/disable signal out 
of LCD shutter generated are sent to the control circuit 308 respectively. 
If the LCD shutter signal is in "enable" state, and the shutter switching 
signal is in high state, the control circuit 308 will send a LCD driving 
signal to the right LCD shutter so as to have the right LCD shutter set in 
shutoff state, while the zero voltage will be sent to the left LCD 
shutter, and the left LCD shutter will be set in transparent state; 
therefore, a user wearing the LCD shutter eye-glasses can only see the 
left image through the left eye, while the right eye sees nothing. 
Likewise, if the LCD shutter signal is in "enable" state, and the 
shutter-switching signal is in low state, the control circuit 308 will 
send a LCD driving signal to the left LCD shutter so as to have the left 
LCD shutter set in shutoff state, while the zero voltage will be sent to 
the right LCD shutter, and the right LCD shutter will be set in 
transparent state; therefore, a user wearing the LCD shutter eye-glasses 
can only see the right image through the right eye, while the left eye 
sees nothing. If it is in "disable" state, the control circuit 308 will 
send a zero voltage to the left and right shutters simultaneously so as to 
have the left and right LCD shutters all set in transparent state. 
Therefore, a user wearing the LCD shutter eye-glasses can see the left and 
right images through two eyes, i.e., it is similar to a condition of not 
wearing LCD shutter eyeglasses, and the LCD shutter eye-glasses have no 
effect to user's sight. 
In brief, the present invention can have the switching of the LCD shutter 
of the LCD shutter eye-glasses synchronized with the display of the left 
and right images by using an external shutter synchronizer with RS 232 
interface designed with a simple circuit and using a software program 
together with a hardware device. The present invention not only can 
overcome the problems of a conventional complicated circuit and 
inconvenience of use thereof, but also can change the position of circuit 
of the external shutter synchronizer with RS 232 interface, if necessary; 
therefore, it can reduce the manufacturing cost, and can provide more 
convenience during use so as to have more economical features.