Abstract: This article in synthesizes several traditional the array CCD actuation successions to have the method to be superior, in the shortcoming foundation, proposed one kind based on monolithic integrated circuit’s new array CCD driving circuit, unifies model of commonly used chip TCD1500C, introduced this method concrete realization in detail.
Key word: Monolithic integrated circuit; Array CCD; Succession
Introduction
The different factory, the different model’s CCD actuation succession is different, to the different performance, the different application situation’s volume, the cost, the flexible request is in addition different, therefore has had the numerous actuation succession production method, mainly has the direct digital circuit to actuate, the monolithic integrated circuit mouth actuation, the EPROM actuation, the special-purpose IC actuation and so on commonly used actuation succession production method. But they have the logical design to be more complex, the debugging difficulty, the flexibility to be bad, to actuate the clock low status shortcoming.
This article in synthesizes each actuation succession method in the foundation, proposed one kind based on monolithic integrated circuit’s new driving circuit. This electric circuit use independent clock source produces the precise clock pulse, uses programmable fixed time counts the method which the chip and the monolithic integrated circuit control unify, causes the electric circuit to produce stably, precise, the high speed drive pulse, this circuit structure is simple, the debugging is convenient, the CPU occupancy rate was low, reduced system’s overall cost, moreover had the good flexibility, only needed to change the actuation software to be possible to apply in the different CCD chip, suited in the commercial measurement use.
The driving circuit composes basically
Mainly has the electric circuit, the frequency dividing circuit, the control circuit, the pulse-duration modulation electric circuit based on monolithic integrated circuit’s new array CCD driving circuit by the pulse and so on to be composed, as shown in Figure 1.
Usually the clock pulse may be from following way: Monolithic integrated circuit XTAL end, ALE end, independent pulse source. And is from time the XTAL end, obtains the pulse frequency after the frequency dividing circuit to limit; Is from the ALE end the pulse, in the monolithic integrated circuit visits the exterior memory’s time loses, the precision is affected; But is from the independent pulse source the pulse because of its independence but the precision is high, and produces the pulse frequency may the free choice, the stability be good, therefore this driving circuit selects the independent pulse source.
The frequency dividing circuit may select D the trigger /JK trigger, like 74LS(HC)74, 74LS(HC)76, bring the setting, the reset end, easy to control; May also select the counter, like 74LS(HC) 163 (may initialize), 8253 (2MHZ programmable), 82(C) 54 (10MHZ programmable). For ease of debugs and increases system’s flexibility, this driving circuit selects has high frequency 82C54, it includes 3 16 subtraction counters, 6 workings. And working 2:00, plays the frequency generator the role, the CLK end input pulse causes the counter to reduce 1, the counter reduces to 1:00 stops the counting, and causes the OUT end to output negative pulse; The way 3 square wave-form oscillator function, before [(N 1)/2] counts completes, is the high level, to addition [(N-1)/2] counts when outputs the low level.
The control circuit is mainly composed of monolithic integrated circuit AT89C51 and the logical gate. At89C51 highest operating frequency reaches 24MHz, contains the 4KB Flash memory. Uses in 82C54 the initialization, the control counter impulse make-and-break, the counter start, stopping and completing in the system other duties.
The pulse-duration modulation electric circuit mainly by the resistive-capacitive circuit, the monostable circuit (for example 74LS/HC123) is composed. This electric circuit mainly uses in adjusting between each drive pulse the phase relation. 74LS(HC)123 is may trigger the monostable trigger again. In trigger pulse’s rise along (meets the B end) or the drop along (meets a end) under the function, outputs Q is the high level, after passing through time delay Tw, outputs Q to return to the low level; If outputs high level period, the trigger pulse arrives, then the high level from this moment time delay Tw, if therefore trigger pulse in high level period arrives unceasingly, then the high level is going by the unlimited time detention, namely the output to be the high level; When the external connection resistance is R, and time electric capacity C>1000pF, Tw=0.45 * R *C.
Figure 1 driving circuit schematic diagram
Figure 2 system diagram
System example
System composition
This system uses in surveying in the propeller rotation process paddle blade’s polarization angle. Because the propeller has the rigidity, not only in its rotation process has swinging, and has the vibration, beats the angle survey to need to gather its transient state in the propeller rotation process the position, uses CCD the image formation characteristic, the propeller transient state’s positional information through the CCD image formation, the light signal transforms into the electric charge signal, passes through the signal processing electric circuit, transforms for the digital signal, transmits to the CPU processing. System diagram as shown in Figure 2.
In system’s photo source may select the active photo source or the natural light, according to tests factor overall evaluations and so on scene environment, installment space, volume; The optical system may act according to tests the scene the size request and the field of view request, according to geometrical optics formula computation designation; CCD selects Japanese Toshiba Corporation’s TCD1500C, the measuring accuracy and the resolution is very high, in has the driver and the sampling maintains the electric circuit, the output may take directly except the amplitude modulation pulse ingredient video signal, and only needs 3 group driving signals: SH, PHI, RS; The signal processing electric circuit uses to the CCD output video signal carries on processing and so on filter, enlargement, binaryzation, sampling, is advantageous for the DSP processing; The main processor uses digital signal processor DSP, it is one kind of high performance monolithic integrated circuit, the internal structure uses the improvement the Harvard structure, has many data, the address bus, may simultaneously visit the data and the program memory, its multistage depth assembly line, may load in advance reaches eight levels of instructions much, the instruction execute speed may reach 300MIPS~10GIPS (to have parallel CPU), widely applies in the test, the signal processing, the communication and so on big operand domain, may take cooperates the processor (large-scale system), may also take the main processor (middle and small scale system), and has SP, SPI, DMA, PCI, the USB connection, may also with the superiorMachine and lower position machine communication.
Actuation example
* the actuation succession requests and realizes
TCD1500C actuation succession as shown in Figure 3-(a), its operating frequency ≤8MHz, takes fF=1MHz, fRS=2MHz, TSH≥(5340 64 12)/2ms. Its Chinese Library 3-(b) succession realizes by Figure 1-(b), by the monolithic integrated circuit compulsion setting, satisfies the electric charge to shift to the shift register; Figure 3-(c) the succession realizes by Figure 1-(d), Re selects the precise adjustable resistance, Ce>1000pF, the delay time decided by formula Tw=0.45 * R *C, may also observe the modulation on the oscilloscope.
The driving circuit work process is as follows: When on electricity initial, in the control and frequency dividing circuit’s monolithic integrated circuit AT89C51 phase should interrupt, to each control pin hypothesis original state level. Then carries on the initialization to the 82C54 counter, establishes 82C54 the working: The timer 1 and the timer 2 work in the way 3 (square wave-form oscillator), the timer 2 work in the way 4 (software triggering way), and read in the starting value, then 89C51 waited for that main engine’s instruction - starts to survey, then makes 82C54 to start to work, produces the drive pulse. After producing a complete integral cycle drive pulse, 89C51 stops producing the drive pulse, waits for main engine’s instruction. When the CCD first video signal is effective, after signal processing electric circuit’s a series of processing, may carry on A/D under the synchropulse function to the output video signal to transform, also after may use the radio impulse counting binaryzation the pulse width, the data which will obtain through the communication gives main engine processing, the result which the main engine will survey stores the memory or passes to superior PC machine directly, then sends to 89C51 starts to order, the actuation next video signal, so moved back and forth until the conclusion.
* driving circuit’s software programming
The pulse has the electric circuit to produce the 4MHz square-wave pulse, it through Figure 1-(b) frequency dividing circuit’s two frequency divisions, obtains the 1MHz square-wave pulse. Shown in Figure 1-(b) the succession through the P1.1 control, thus produces the f pulse; The timer 0 counter impulses are from have the f pulse first frequency divider’s output (2MHz), its counting starting value > (5340 64 12)ms, thus produces the SH pulse; Through takes f the timer 1 counter impulse, counting starting value =2, receives the OUT1 output the pulse-duration modulation electric circuit then to obtain again the RS pulse. Hence, the CCD work needs the drive pulse obtains completely.
89C51 has the drive pulse subprograms to see the website (www.eaw.com.cn)
Figure 3 TCD1500C drive pulse succession
Conclusion
This driving circuit synthesized the direct digital circuit to actuate the method to have the high driving frequency and the monolithic integrated circuit mouth actuation method flexible characteristic, but also had the hardware circuit to be simple, the cost was low, the software programming nimble, might facilitate directly characteristics and so on acceptor processor control, moreover in actual use stable reliable, had certain use value.
Reference
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