CN101819476A - Alternating current pointing light pen, multi-light-pen identification device and method of multi-light-pen identification - Google Patents

Abstract

The invention discloses an AC pointing light pen, a multi-light pen identification device and a multi-light pen identification method. The shell of the AC pointing light pen is provided with an alternating light control circuit, the alternating light control circuit is electrically connected with the power management circuit and the light source respectively, and the contact switch is close to the switch of the alternating light control circuit. The transmitting device and the receiving device of the multi-light pen recognition device are on the same side of the writing screen or are separated on both sides. The transmitting device includes the first and second pointing light pens, and the first pointing light pen is an AC pointing light pen; A camera and a signal processing circuit; the camera lens is aligned with the normal line of the screen; the signal processing circuit includes an amplifier circuit, a high-speed comparison circuit and an identification control circuit connected in series, and the identification control circuit includes a multi-light pen identification module. The advantages of the present invention are: (1) the AC pointing light pen can be obtained by adding an alternating light control circuit on the basis of the existing direct current pointing light pen, and the structure is simple. (2) The multi-light pen recognition device can quickly identify the multi-light pen.

Description

Communication pointing light pen, multi-light pen recognition device and multi-light pen recognition method

technical field

The invention relates to an AC pointing light pen, a multi-light pen recognition device and a multi-light pen recognition method, which can realize accurate distinction when multiple pointing light pens are used at the same time, and the multi-light pen recognition device and multi-light pen recognition method can be applied to multiple pointing pens In a system operated by multiple users at the same time, such as an interactive electronic whiteboard.

Background technique

Multi-light pen recognition technology is widely used in many fields. For example, in a large-screen interactive electronic whiteboard system used by multiple users, one of the key technologies is multi-light pen recognition.

With the development of human-computer interaction technology, people pay more and more attention to multi-user operation, and more and more products support multi-user simultaneous operation. For example, in a large-screen command system, it is often necessary to realize multi-person command at the same time. For the current common single-pointing light pen device, it cannot meet the needs of multi-user operation. On the other hand, for the same user, multiple pointing light pens can also be used in combination, such as two pointing light pens, one of which is fixed on the operation object, and the other light pen draws a circle around it, then the operation can be realized. The rotation of the object, or the movement of two light pen points in different directions on the same operation object, can realize the stretching or compression of the operation object, etc. These operation effects are simpler and more convenient than using a single pointing light pen, and have a wide range of possibilities. Application prospect.

At the present stage, there is no convenient and accurate multi-light pen recognition device, and the present invention fills up the technical vacancy in this respect.

Contents of the invention

The technical problem to be solved by the present invention is to provide a recognition device for multiple light pens, which can recognize each other when multiple pointing light pens exist at the same time.

The technical solution adopted by the present invention to solve its technical problems is: the AC pointing light pen mainly includes a pen case, a battery, a power management circuit, a contact switch and a luminous body, the battery is electrically connected to the power management circuit, and the luminous body includes a light source The light-emitting end of the light source is fixedly connected with the light guide rod, the other end of the light source is fixedly connected with the touch switch, and the front end of the pen case is provided with an opening matching the illuminant, and the illuminant is placed in the opening In the hole, the front end of the light guide rod is placed outside the pen case, and the battery, power management circuit and contact switch are placed in the pen case, wherein an alternating light control circuit is also provided in the pen case, the The alternating light control circuit is electrically connected with the power management circuit and the light source respectively, and the contact switch is close to the switch of the alternating light control circuit.

In the present invention, the multi-light pen recognition device using the above-mentioned AC pointing light pen mainly includes a transmitting device, a receiving device and a writing screen. The device includes a first pointing light pen and a second pointing light pen, and the receiving device includes a video camera and a signal processing circuit electrically connected to each other; the lens of the video camera is aligned with the normal line of the writing screen; the signal processing circuit includes sequentially connected amplifying circuit, a high-speed comparison circuit and an identification control circuit, the identification control circuit includes a multi-light pen identification module; the first pointing light pen is an AC pointing light pen.

Further, the second pointing light pen of the present invention is a DC pointing light pen.

Further, the second pointing light pen of the present invention is an AC pointing light pen.

Further, the alternating period or duty cycle of the second pointing light pen and the first pointing light pen in the present invention are different.

Further, the recognition control circuit of the present invention includes a camera drive module and a multi-light pen recognition module, the camera drive module is electrically connected to the camera, and the multi-light pen recognition module is electrically connected to a high-speed comparison circuit.

The present invention uses the above-mentioned multi-light pen identification device to carry out the method for multi-light pen identification mainly comprising the following steps:

(1) The camera starts to work;

(2) Contact the first pointing light pen and the second pointing light pen with the writing screen at the same time, so that the light sources of the first pointing light pen and the second pointing light pen start to emit light, and the first pointing light pen emits alternating light;

(3) The light emitted by the first pointing light pen and the second pointing light pen is incident on the camera and converted into an electrical signal;

(4) video camera inputs described electrical signal into the amplifying circuit of signal processing circuit to amplify, and the amplified electrical signal is input to the multi-light pen identification module of identification control circuit through high-speed comparison circuit;

(5) the multi-light pen identification module detects the positions of the first pointing light pen and the second pointing light pen, and obtains the number of detected pointing light pens in the scanning cycle of the same camera;

(6) In two adjacent scanning periods of the camera, if the multi-light pen recognition module detects a single pointing light pen in one of the scanning periods, and detects two pointing light pens in the other adjacent scanning period, then execute step;

(7) If the multi-light pen identification module detects two pointing light pens in the scanning period of a camera in the step and the position of one pointing light pen is closer to the single pointing light pen detected in the adjacent scanning period than the position of the other pointing light pen For the position of the pointing light pen, the pointing light pen closer to the single pointing light pen is a direct current pointing light pen, and the other pointing light pen is an AC pointing light pen.

Further, in the present invention, the alternating period of the first pointing light pen is 2-3 times the scanning period of the camera, and the duty ratio of each alternating period is 1:1-2.

Compared with prior art, the beneficial effect of the present invention is:

(1) The AC pointing light pen of the present invention can be obtained only by adding an alternating light control circuit on the basis of the existing DC pointing light pen, and the structure is simple.

(2) For the multi-light pen recognition device, the prior art usually adopts the method of combining two pointing light pens with different brightness. In this method, due to the aberration of the camera optical system, the same pointing light pen at the edge position and the middle position of the screen cannot be detected. The resulting image is different, which may easily cause misjudgment when the multi-light pen is recognized. However, the present invention adopts the method of combining the AC pointing light pen with other pointing light pens (DC pointing light pen or AC pointing light pen), and will not be affected by the aberration of the camera optical system during identification, and can quickly identify different pointing light pens with high recognition accuracy , It is not easy to misjudgment.

Description of drawings

Fig. 1 is the structural representation of the communication pointing light pen of the present invention;

Fig. 2 is a working principle diagram of the multi-light pen recognition device of the present invention;

Fig. 3 is a structural schematic diagram of a DC light pen in the multi-light pen recognition device of the present invention;

Fig. 4 is a structural principle block diagram of the signal processing circuit in the identification device of the present invention;

Fig. 5 is when the alternating cycle of the first pointing light pen of the present invention is 2 times of the scanning cycle of the CCD camera, the duty ratio of the alternating cycle is 1: 1, and the alternating jump point of the AC pointing light pen and the starting point of the CCD scanning cycle Schematic diagram of the distribution of the pointing light pen image after the CCD scanning output signal passes through the amplification circuit and the high-speed comparison circuit during synchronization;

Fig. 6 is when the alternating period of the first pointing light pen of the present invention is 3 times of the CCD scanning period, and the duty ratio is 1:2 under the situation that the CCD scanning output signal passes through the amplifying circuit and the distribution situation of the pointing light pen image after the high-speed comparison circuit schematic diagram,

Wherein, (a) is that the first pointing light pen is on the right side of the DC pointing light pen and the multi-light pen recognition module only detects the AC light pen image once every three CCD scanning cycles; The left side of the light pen and the multi-light pen identification module only detects the AC light pen image once every three CCD scanning cycles; (c) is the first pointing light pen is on the right side of the DC pointing light pen and the multi-light pen recognition module detects every three CCD scanning cycles The situation of two AC light pen images; (d) is the situation where the first pointing light pen is on the left side of the DC pointing light pen and the multi-light pen recognition module detects the AC light pen image twice every three CCD scanning cycles;

Fig. 7 is a working principle diagram of the multi-light pen recognition module in the recognition control circuit of the present invention.

Detailed ways

As shown in FIG. 1 , the AC pointing light pen includes a luminous body, a contact switch 13 , an alternating light control circuit 17 , a power management circuit 14 , a battery 15 and a pen case 16 . Wherein the illuminant includes a light guide rod 11 and a light source 12 , and the front end of the illuminant is placed outside the pen case 16 . The front end of the pen case 16 is provided with an opening matching the size of the illuminant. The illuminant is placed in the opening and can move along the axial direction of the opening; the battery 15, the power management circuit 14, the alternating light control circuit 17 and the contact switch 13 are placed in the pen case 16; the battery 15 and the power management The circuit 14 is connected; the alternating light control circuit 17 is connected with the power management circuit 14 and the light source 12 respectively; the light-emitting end of the light source 12 is fixedly adhered to the light guide rod 11; 13 is close to the switch of the alternating light control circuit 17, as the illuminant can move along the axial direction of the opening, the switch of the alternating light control circuit 17 can be opened or closed under the action of the contact switch 13.

The multi-light pen recognition device using the above-mentioned AC pointing light pen in the present invention is shown in FIG. Wherein, the first pointing light pen 1 is an AC pointing light pen, which emits AC light 6 when in contact with the writing screen 3; The lens of the camera 4 is aligned with the normal direction of the writing screen 3 to image the entire screen. The light generated by the contact of the AC pointing light pen and the DC pointing light pen with the writing screen 3 is incident on the camera 4 , and the camera 4 is connected to the signal processing circuit 5 .

For the first pointing light pen 1 (that is, the AC pointing light pen), what the contact switch 13 usually adopts is a spring. The function of the alternating light control circuit 17 is to control the light source 12 of the AC pointing light pen 1 to generate alternating light. As an embodiment of the present invention, the alternating light control circuit 17 is a square wave generating circuit. The core of the square wave generating circuit is an MSP430 single-chip microcomputer produced by Texas Instruments and a field effect tube. The model of the single-chip microcomputer is M430F1232. The battery 15 adopts a No. 7 dry cell with a voltage of 1.5V. The core of the power management circuit 14 is a power management chip produced by ON Semiconductor, the model is NCP1400ASN33T1, which can increase the input voltage of the dry battery 1.5V to 3.3V output, and provide operating voltages for the MSP430 single-chip microcomputer and the light source 12 respectively. The light source 12 of the AC light pen adopts an infrared semiconductor laser with a power of 5mw. Using the infrared light source can reduce the interference of ambient light, thereby improving the stability and precision of the system. In addition, for the light emission of the AC pointing light pen 1, in addition to the light 6 in the form of a square wave, the alternating light control circuit 17 of the present invention can also be a sine wave generating circuit to generate light in alternating forms such as sine, or other alternating forms of light .

When the AC pointing light pen 1 is in contact with the screen 3, the light guide rod 11 and the light source 12 push the spring to close the switch of the square wave generating circuit 17, and the single-chip microcomputer starts to work under the voltage provided by the power management circuit 14, and the single-chip microcomputer calls two delays alternately function, in different delay times, the I/O port of the microcontroller outputs high and low levels respectively, and the ratio of the delay time of these two delay functions is the duty cycle of the square wave. The I/O port of the microcontroller is connected to the gate of the field effect tube of the square wave generating circuit, the drain of the field effect tube is connected to the negative pole of the light source through a current limiting resistor, the positive pole of the light source is connected to 3.3V voltage, and the source of the field effect tube The pole is grounded, and the model of the field effect tube is 2N7002, so that the alternating high and low levels of the I/O port are used to control the on-off of the field effect tube, so that the AC pointing light pen 1 emits alternately bright and dark AC light 6 .

For the DC pointing light pen, as shown in Figure 3, the difference between it and the AC pointing pen is that there is no alternating light control circuit 17, and the power management circuit 24 is directly connected to the light source 22, and the contact switch 23 is close to the switch of the power management circuit 24. When the DC pointing light pen is in contact with the screen 3, the light guide rod 21 and the light source 22 push the spring 23 to close the switch of the power management circuit 24, and the power management circuit 24 provides a constant working voltage to the DC pointing light source 22, and the DC pointing light pen emits Light with constant brightness7.

As an embodiment of the present invention, in the multi-light pen recognition device of the present invention, the camera 4 can be a linear CCD camera, and the CCD chip is usually placed along the horizontal direction. The CCD chip can adopt the linear array CCD produced by SONY Company, the model is ILX511. As shown in FIG. 4 , the signal processing circuit 5 includes an amplifier circuit 53 , a high-speed comparison circuit 52 and an identification control circuit 51 connected in series in sequence. The recognition control circuit 51 further includes a CCD drive module 511 and a multi-light pen recognition module 512 . The core of the identification control circuit 51 is a CPLD chip produced by Altera Company, and the adopted model is EPM1270T144. The amplifying circuit 53 can adopt the operational amplifier chip TL084 to realize reverse amplification. The high-speed comparison circuit 52 can adopt a comparator chip produced by Linear Technology Corporation, the model is LT1016, and the high-speed comparison circuit 52 can convert analog signals into digital signals that can be processed by CPLD. Both the CCD driver module 511 and the multi-light pen recognition module 512 are realized by programming in the CPLD chip by using the Verilog hardware description language. Write the CCD driver module 511 according to the driving waveform in the CCD chip data sheet, and connect it with the CCD camera. The multi-pointing light pen identification module 512 is connected with the high-speed comparison circuit 52 . If the above-mentioned CCD camera has its own drive, then the identification control circuit 51 does not need to be provided with a CCD drive module 511 .

The working process of the CCD-based multi-light pen recognition device of the present invention mainly includes the following main steps:

1. The output signal of the CCD driver module 511 is input to the CCD camera, and the CCD camera starts to work.

2. When the first pointing light pen 1 (for the AC pointing light pen) and the second pointing light pen 2 (for the DC pointing light pen) were operating on the screen 3 at the same time, the first pointing light pen 1 sent the AC light 6 whose brightness was in the form of a square wave, The second pointing light pen 2 emits direct current light 7 with constant brightness.

3. The light emitted by the first pointing light pen 1 and the second pointing light pen 2 passes through the light guide rod 11 and the light guide rod 21 to form two light spots on the writing screen 3, and is scanned by the CCD camera to complete the conversion from optical signal to electrical signal .

4. The scan output signal of the CCD is amplified in reverse by the amplifying circuit 53 on the signal processing circuit 5, and then through the high-speed comparison circuit 52, is converted into a digital signal that can be processed by the identification control circuit 51, and is output to the multi-light pen identification of the identification control circuit 51 Module 512.

5. The multi-pointing light pen recognition module 512 analyzes the input signal and recognizes the multi-pointing light pens.

The multi-light pen recognition module 512 realizes the principle of multi-light pen recognition as follows: the CCD chip in the CCD camera is installed in the horizontal direction, and the two light spots formed by the AC pointing light pen and the DC pointing light pen on the writing screen 3 pass through the optical system of the CCD camera 4 to form images On the CCD chip, and these two are like two bright lines in the vertical direction, if the positions of the two pointing light pens in the horizontal direction are different, the two bright lines are parallel to each other, and both are perpendicular to the linear array CCD chip Intersection means that the output signal of the CCD is a voltage drop corresponding to the position of the two bright lines, and the time axis of the CCD output signal corresponds to the position in the direction of the CCD chip. It can be seen that the position of the pointing light pen on the screen 3 corresponds to the intersection position of the bright line and the CCD. The time N to the bright line represents this position) then the identification of the two pointing light pens on the screen 3 can be realized.

If the scanning period of the linear array CCD is T, the square wave duty ratio of the AC pointing light pen is 1:1, and the alternating period is 2T, the transition point of the square wave is synchronized with the starting point of the linear array CCD scanning period, and the DC pointing light pen and The AC pointing light pen does not move on the writing screen 3, and the intersection positions of the two bright lines and the CCD are always unchanged, that is, N1=N2. By analyzing the output signal of the CCD, as shown in Figure 5, the positions of the detected bright lines are divided into two cases: N1 and N3, where N1 corresponds to the bright lines P1, P2, P4, and P5, and N2 corresponds to the bright lines P3 and P6. There is always a bright line at position N1, and it can be determined that this position N1 corresponds to the position where the DC pointing light pen 2 is in contact with the screen; while the bright line at position N3 only appears alternately in the T2 and T4 cycles, and position N3 corresponds to the contact between the AC pointing light pen and the screen s position. At this time, the pointing light pen can be recognized within two scanning cycles, realizing the rapid recognition of the multi-light pen.

In the present invention, if the square wave duty ratio of the first pointing light pen 1 is adjusted to 1:2, and the alternating period is correspondingly adjusted to 3T, the multi-light pens can also be quickly identified. At this time, the duration of the high level is T, and the duration of the low level is 2T. The principle is as follows: 1 indicates that a bright line is detected in the scanning period of the CCD, and 0 indicates that no bright line is detected. According to the difference between the comparison voltage and the square wave jump time relative to the starting time of the CCD scanning period, there will be 100100100...or 110110110...these two situations, that is, the two states of 100 or 110 appear cyclically. When the light pen is on the left side of the AC pointing light pen, the CCD output signal has two possible situations (a) and (c) as shown in Figure 6; when the DC pointing light pen is on the right side of the AC pointing light pen, the CCD output signal is as shown in Figure 6 There are two possible cases (b) and (d) shown. Wherein, (a) is that the AC pointing light pen is on the right side of the DC pointing light pen and the multi-light pen recognition module only detects the AC light pen image once every three CCD scan cycles; (b) is that the AC pointing light pen is on the left side of the DC pointing light pen and The multi-light pen recognition module only detects the AC light pen image once every three CCD scanning cycles; (c) is that the AC pointing light pen is on the right side of the DC pointing light pen and the multi-light pen recognition module detects the AC light pen twice every three CCD scanning cycles (d) is the situation where the AC pointing light pen is on the left side of the DC pointing light pen and the multi-light pen recognition module detects the AC light pen image twice every three CCD scan cycles; no matter what the situation is, three consecutive CCD scan cycles In two adjacent scanning periods, the multi-light pen identification module 512 detects a single pointing light pen in one scanning period, and detects two pointing light pens in another adjacent scanning period. Considering that the pointing light pen will inevitably move during use, but because the CCD scanning period is very small, as an embodiment of the present invention, it is set to 5 ms. limited, so it can be assumed that in adjacent CCD scanning periods, the detected position of the same pointing light pen does not change much. The position is closer to the position of the single pointing light pen detected in the adjacent scanning period, because the position of the single pointing light pen must be the position of the DC pointing light pen, so the pointing light pen of the two pointing light pens that is closer to the position of the single pointing light pen is DC Pointing light pen, another pointing light pen is communication pointing light pen. If the comparison voltage of the high-speed comparator circuit 52 is smaller than the amplified voltage value output by the CCD and amplified by the charge accumulated at the brightest point of the bright line within the time T/2, misjudgment during the light pen recognition process can be further avoided.

In the multi-light pen recognition module 512, the CCD output signal passing through the amplification circuit 53 and the high-speed comparison circuit 52 is detected. Due to the reverse amplification and high-speed comparison, the electrical signal corresponding to the bright line position is a high level. Considering that only multi-light pen recognition is required, the position of detecting the bright line can be simplified to the position of detecting the rising edge of the high level. At the beginning of the scanning cycle of the CCD, the clock frequency of the CCD output pixels is counted, and the value M in the counter represents the number of pixels, that is, the position in the direction of the CCD chip.

When the square wave duty ratio of the AC pointing light pen is 1:2 and the alternating period is 3T, the working process of the multi-light pen identification module 512 is shown in Figure 7, and the counter I and counter II start counting when the CCD scanning period begins. If no high level is detected, wait until the end of the CCD scanning cycle, counter I and counter II are cleared, and then start the detection of the next cycle; if a high level is detected, counter I stops counting and continues to detect high level, If the high level is detected again, that is, there are two bright lines in this scanning period, the counter II stops counting at this time, and the value M1 in the counter I and the value M2 in the counter II are saved, corresponding to the first bright line respectively and the position of the second bright line, and add 1 to the cycle number m of two bright lines in the same scan cycle, then wait until the end of the CCD scan cycle, counter I and counter II are cleared, and start the detection of the next cycle; if there is no If a high level is detected again, that is, there is only one bright line in this cycle, then a judgment is made. If two bright lines are not detected in a cycle before the CCD scanning cycle, that is, m=0, then it is still impossible to judge. Wait until the CCD At the end of the scanning period, counter I and counter II will start the detection of the next period; if m is not 0, save the value M3 in counter I of this scanning period, and at this time the identification of two pointing light pens can be realized: when |M3 When -M1|<|M3-M2|, it can be considered that M3 and M1 are the position of the same pointing light pen, and M3 is the position of the bright line when there is only one bright line in the CCD scanning cycle, and the corresponding position must be the position of the DC pointing light pen 2 , so M1 is also the position of the DC pointing light pen 2, and M2 is the position of the AC pointing light pen; otherwise, it can be considered that M3 and M2 are the same pointing light pen position, and M2 must correspond to the position of the DC pointing light pen, so M1 corresponds to the AC pointing light pen The position of the light pen, M2 corresponds to the position of the DC pointing light pen. So far, we have realized the recognition of two pointing light pens when they are used at the same time.

When the camera adopts a linear array CCD camera and the coordinates of the two pointing light pens are the same in the horizontal direction, the bright lines of the two pointing light pens overlap and cannot be distinguished. At this time, a linear array CCD camera can be added, and the normal direction of the screen is The rotation axis is rotated 90 degrees relative to the original CCD camera, so that the two pointing light pens can be distinguished in the vertical direction.

As another embodiment of the present invention, the second pointing light pen 2 may also be an AC pointing light pen. In addition, in order to realize simultaneous operation by more users, the number of AC pointing light pens can be increased. For the above two cases, it is necessary to meet the requirement that the alternating periods or duty ratios of the various AC pointing light pens are different. Similar to the case where the second pointing light pen 2 is a DC pointing light pen, the two AC pointing light pens with different alternating periods or duty ratios have different distributions of the AC pointing light pen images detected in the camera output signal. The specific value of the period or duty cycle and the distribution of the detected AC pointing light pen images can distinguish multiple AC pointing light pens.

Claims (8)

1. alternating current pointing light pen, comprise a shell (16), battery (15), electric power management circuit (14), touch switch (13) and luminophor, described battery (15) and electric power management circuit (14) are electrically connected, described luminophor comprises light source (12) and lamp guide (11), the luminous end of light source (12) is fixedlyed connected with lamp guide (11), the other end of light source (12) is fixedlyed connected with touch switch (13), the front end of shell (16) is provided with the perforate that is complementary with luminophor, described luminophor places this perforate, the front end of described lamp guide (11) places outside the shell (16), described battery (15), electric power management circuit (14) and touch switch (13) place in the shell (16), it is characterized in that: also be provided with alternation light control circuit (17) in described the shell (16), this alternation light control circuit (17) is electrically connected with electric power management circuit (14) and light source (12) respectively, and touch switch (13) is close with the switch of alternation light control circuit (17).

2. multi-light-pen identification device that uses the described alternating current pointing light pen of claim 1, it is characterized in that: comprise emitter, receiving trap and write screen (3), described emitter and receiving trap place the same side of writing screen (3) or be placed in writes the both sides of screen (3), described emitter comprises first pointing light pen (1) and second pointing light pen (2), and described receiving trap comprises the video camera (4) and the signal processing circuit (5) of mutual electrical connection; The normal of the alignment lens screen (3) of described video camera (4); Described signal processing circuit (5) comprises amplifying circuit (53), high speed comparator circuit (52) and the recognition control circuit (51) of series connection successively, and described recognition control circuit (51) contains many light pens identification module (512); Described first pointing light pen (1) is an alternating current pointing light pen.

3. multi-light-pen identification device according to claim 2 is characterized in that: described second pointing light pen (2) is the direct current pointing light pen.

4. multi-light-pen identification device according to claim 2 is characterized in that: described second pointing light pen (2) is an alternating current pointing light pen.

5. multi-light-pen identification device according to claim 4 is characterized in that: described second pointing light pen (2) is different with the alternating cycles or the dutycycle of first pointing light pen (1).

6. multi-light-pen identification device according to claim 2, it is characterized in that: described recognition control circuit (51) comprises camera driver module (511) and many light pens identification module (512), camera driver module (511) is electrically connected with video camera (4), and many light pens identification module (512) is electrically connected with high speed comparator circuit (52).

7. a method of using the described multi-light-pen identification device of claim 3 to carry out many light pen identifications is characterized in that comprising the steps:

(1) video camera (4) is started working;

(2) with first pointing light pen (1) and second pointing light pen (2) simultaneously with write screen (3) and contact, so that the light source of first pointing light pen (1) and second pointing light pen (2) begins luminous, described first pointing light pen (1) sends interchange light, and described second pointing light pen (2) sends direct current light.

The light that (3) first pointing light pens (1) and second pointing light pen (2) send incides video camera (4) and converts electric signal to;

(4) video camera amplifies the amplifying circuit (53) that described electric signal is input to signal processing circuit, and the electric signal after the amplification is input to many light pens identification module (512) of recognition control circuit (51) through high speed comparator circuit (52).

(5) many light pens identification module (512) detects the position of first pointing light pen (1) and second pointing light pen (2), and obtains the number of the interior detected pointing light pen of scan period of same video camera (4);

(6) in adjacent two scan periods of video camera (4), if many light pens identification module (512) detects single pointing light pen in a scan period therein, and in another adjacent scan period, detect two pointing light pens, then execution in step (7);

(7) if the position that detects two pointing light pens and one of them pointing light pen in the scan period of the video camera (4) of many light pens identification module (512) in step (5) than the position of the position of another pointing light pen detected single pointing light pen in more approaching adjacent scan period, that pointing light pen of then more approaching single pointing light pen position is the direct current pointing light pen, and another pointing light pen is an alternating current pointing light pen.

8. method of carrying out the identification of many light pens according to claim 7 is characterized in that: the alternating cycles of described first pointing light pen (1) is 2～3 times of scan period of described video camera (4), and the dutycycle of each described alternating cycles is 1: 1～2.

Images