Using video in wireless laser positioning equipment design (1)

With the CCD (Charge Coupled Device) is becoming more and more widely applied to industrial, military and civilian sectors.

CCD camera as a device for front-end image sensor combined with other hardware circuit under test image information for quick sampling, transmission and application of data processing systems are increasingly affected by the people's attention. This article describes a device with a CCD camera video signal processing equipment, mainly for the projection screen coordinates of the target point measurement and cursor positioning.

1. overall design scheme of the system

System design as shown in Figure 1, laser pen transmitter to be logging screen dots are CCD devices receive, CCD device output video signal to the synchronization separation circuit and shaping circuitry.

Use synchronization separation circuit, you can get from a video signal line synchronization signals and field synchronization signals and even and odd rows of the synchronization signals, and field synchronization signal was sent to count circuit. Video signal after shaping circuit after optical signal, the signal will be sent to count circuit, count circuit processing output light point of two-dimensional position information, this information is processed by the microprocessor by serial transmission to a computer, computer software programming cursor positioning and simulate mouse single double-click function.

Figure 1 circuit overall chart

2. system hardware circuit design

2.1 shaping circuit

As shown in Figure 2, the CCD camera device 1 output video signals are delivered directly to the operational amplifier 4 zoom, operational amplifier 4 output signal way as voltage comparator input of a 7, and the other one was sent to maximum hold circuit 5 and a maximum of 5 primarily include holding circuit voltage follower 5, capacitor C1, voltage tube Dz1 three devices, when the signal from a voltage follower 5A continuous output, since the existence of the diode D1, capacitor C1 continually charging, voltage increase, until the signal the arrival of the maximum value, then C1 voltage is increased to a maximum value, then a signal arrives as its voltage to increase the voltage of the capacitor at both ends, and thus no longer charging voltage capacitor remains unchanged.

When shown field synchronization signal comes, voltage tube Dz1 RP breakover, electric capacity to quickly discharge, and then have the signal from the output voltage follower 5A, capacitance and start recharging. With this design, you can from each field in the video signal of the strongest signal, and set this value through the output voltage follower 6 to the voltage comparator 7 of another input, voltage comparator 7 output signal is extracted from the video signal from the optical signal, and the optical signal the existence of such characteristics: for each field in the video signal, the signal only if the current value is greater than the previous signal, the signal output is terminated, the output is a low level. Video signal maximum value, the optical signal output at all times maintain a low level. In Figure 2, voltage follower 6 equivalent of a high input impedance component, you can prevent excessive discharge capacitor C1. Power supply VCC provides a clamping voltage.

　　

Figure 2 Schematic diagram of plastic circuit details

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