CN1343069A - Optical sensor amplifier for projection video display - Google Patents

Abstract

A processor for a photo sensor signal in a projection display device, comprises a photosensor S1-S8 generating a sensor signal having a current component indicative of projected raster illumination. The sensor signal includes a scan related crosstalk voltage component. A differential amplifier U280 generates an output signal responsive to the sensor signal. The sensor current component is converted to an amplified sensor voltage component and the crosstalk voltage component is differentially amplified. The sensor voltage component has a greater magnitude than the crosstalk voltage component in the output signal.

Description

Be used for the optical sensor amplifier that projection video shows

Technical field

The present invention relates to video-projection and show the field, particularly produce Signal Processing to the detection of projected image with to the light that when having unwanted interference signal, occurs.

Background technology

In projection video showed, the physical location of cathode-ray picture tube can cause raster distortion how much.The cathode ray tube that use has fluorescence dignity crooked, concave surface and have an intrinsic magnification ratio in the optical projection path can aggravate this raster distortion.Projected image is made of three raster, and these three raster need be watched on the screen aligned with each other at one.Three projected images accurate overlapping need to be regulated a plurality of waveforms, with the compensation geometric distortion and be convenient to the stack of three projected images.Yet a plurality of waveforms of manual-alignment are required great effort very much in manufacture process, and if do not use complicated testing equipment just can't to set up or be provided with in user locations.A kind of auto convergence system that can simplify the aligning in the manufacture process and be convenient to regulate in user locations can adopt grating edge measurement determine raster size and convergence in peripheral display screen position.Yet under having the situation of interference signal, for example have when moving under the scanning correlated frequency of high-frequency energy, this auto convergence system can face some problems.Processed and when producing collimating marks signal M in interference signal as light, misoperation will take place under typical situation.The photosensor signal of this mistake causes the auto convergence failure.These unwanted interference signals are high frequency voltage source normally, can capacitive be coupled to the low-signal levels circuit, and this circuit is associated with the detection and the amplification of the sensor signal that the projection mark image produces.The capacitive coupled signal picks up usually may betide and is positioned near the adjacent circuit of photosensor signal amplifier.So amplifier amplifies required sensor signal and unwanted interference with high-gain, so that interference signal amplitude becomes suitable with required sensor signal even surpasses required sensor signal.The integrated circuit that utilization comprises a plurality of separation algorithm amplifiers may aggravate capacitive coupling cross-interference issue.These a plurality of amplifier sections usually are used to amplify the convergence signal with remarkable high-frequency content.Therefore, utilize this operational amplifier part that high-gain amplifies, desired as optical sensor signals that is used for, making it is responsive for the unwanted signal that is coupled via for example relevant with conductor with the circuit that is connected to optical sensor signals amplifier stray capacitance.Therefore, during aiming at automatically, unwanted, high-frequency content signal has enough amplitudes and hinders reliable mark to generate the detection of sensor signal.The result that unreliable marker edge detects be possible errors finish auto convergence, cause assembling mistake.For guaranteeing that reliable mark detects, require to improve the ratio of optical sensor signals and interference or noise.For example, the selection that interference signal is had an optical sensor signals of minimum multiplication factor is amplified can provide the sensor signal of increase and the ratio of interference.

Summary of the invention

A kind of projection display that has the grating edge transducer, this display is vulnerable to the interference of self-scanning coherent signal, and these signals comprise high-frequency energy, influence the ratio of sensor signal and interference.An optical sensor signals processor that is used in the projection display equipment, this processor comprises the optical pickocff that produces sensor signal, this sensor signal has the current component of expression projection grating illumination.This sensor signal comprises the crosstalk voltage component that scanning is relevant.Differential amplifier response sensor signal produces output signal.The sensor electrical flow component is converted into the sensor voltage component of amplification, and the crosstalk voltage component is amplified by difference.The sensor voltage component has the big amplitude of crosstalk voltage component in the specific output signal.

Description of drawings

Fig. 1 is a kind of simplification front view of projection video display.

Fig. 2 is the simplified block diagram that comprises a kind of video image projection display equipment of feature of the present invention.

The schematic diagram of Fig. 3 A is represented a numerically controlled current source, sensor signal detector and a sensor signal processor of the present invention.

The schematic diagram of Fig. 3 B is represented another kind of sensor signal processor of the present invention.

Fig. 4 A, 4B, 4C, 4D and 4E analog representation are in the processing that exists under the situation of ambient light interference sensor signal.

Fig. 5 analog representation the response of processor 280 of the present invention and the amplitude of 280A when input current is 50 microamperes to frequency.

Fig. 6 analog representation the response of processor 280 of the present invention and the 280A amplitude when the amplitude of input interference signal is 1 volt to frequency.

Embodiment

Fig. 1 represents a kind of front view of video-projection display device.This projection display comprises a plurality of cathode ray tubes, and raster-scanned image projects on the screen 700.Casing supports and round screen 700, and provides one slightly less than the picture-display-region 800 of screen.Dotting a border area that is hidden in casing C inside and according to the work of the overscanning of employing shown in the regional OS pattern time, is illuminated on the screen 700 by raster-scanned image.The position vicinity of optical pickocff is in the periphery that hidden border area is inner and watch the screen 700 of regional 800 outsides.Yet, also can produce one with the image of the raster scan of projection and be presented at that not to be suspended on casing inner or by casing local hidden screen or lip-deep picture.This picture display process is called as orthographic projection and shows.In the orthographic projection configuration, the position of optical pickocff still is in unhidden position of adjacent screen periphery as mentioned above.In the application that operates in orthographic projection and back projection demonstration of outomatic convergence correcting system hereinafter described all is identical.

Represented eight transducers among Fig. 1, they are positioned on the angle at screen edge and are middle.These locational transducers can be measured a kind of test pattern of electron production, top pixel value square M for example, so that determine picture width and height and some geometric error, for example rotation, crooked, trapezoidal, pincushion or the like, thus the display image that should overlap each other on whole screen area is aimed at.Three projection of color images separately level and vertical direction on all carry out measurement, thereby obtain at least four ten eight measured values.

Below to explain the operation of measurement and alignment system with reference to Fig. 2, represent an a kind of part of raster scan video projected display among the figure with the form of block diagram.With three cathode ray tube R, G and B form the monochrome image of raster scan in Fig. 2, understand coalescence by lens combination separately and form single display image 800 on screen 700.Each cathode ray tube of representing among the figure all has four coil groups, is used to provide level and vertical deflection and level and vertical convergence.Drive the horizontal deflection coil group with a horizontal-deflection amplifier 600, drive the frame deflector coil group with a vertical deflection amplifier 650.Level and vertical deflection amplifier are all driven by the deflection waveform signal, control the amplitude and the waveform of deflection waveform signal by data/address bus 951, and synchronous with the selected signal source that will show.The amplifier 610 and 660 that for example provides the convergence correction waveform signal drives each level and vertical convergence yoke 615 and 665 of green channel respectively.Correction signal signal GHC and GVC can be considered to represent DC and AC to assemble signal, for example static state and dynamic convergence.Yet these functional attributes can be simplified, and for example revise all addresses, measuring position with same numerical value or side-play amount, move whole grating and reach a kind of tangible static convergence or centering regulating effect.Similarly, also can produce a kind of dynamic convergence effect by the location address of revising a particular measurement position.Can use-case in full-weighted-voltage D/ A converter 311 and 312 changes the digital value of reading from memory 550, therefrom produces the correction signal signal GHC and the GVC of green channel.

An input shows signal selector utilizes bus 951 to select for example a broadcast video signal and the shows signal that the SVGA computer produces between two signal source IP1 and IP2.Video display signal RGB obtains from the information of display video selector and electron production, for example can on screen display generator 500, make up subscriber control information, show and set up and registration signal, and the message that produces from the order of the controller 301,900 that is connected with 951 by bus 302 and 950 of response.In the process of automatic sensitivity calibration or convergence aligning, controller 900 sends order by data/address bus 302 to controller 301, instruction video generator 310 produces an exemplary green channel calibration video test signal AV, it comprises an exemplary black level signal that has rectangular block M, and rectangular block M has predetermined video amplitude value.Controller 900 and 301 is gone back locating piece M, by determining level and the vertical exemplary sensor S1 that regularly shines, perhaps by the motion scan grating, perhaps comprises a part of raster of this tag block M, show within the grating piece M is positioned at scanning.Green channel test signal AV from IC300 output and amplifier 510 with green channel output signal combination from screen display generator 500.Like this, be connected to exemplary green cathode ray tube GCRT, and can comprise the calibration video test signal AV that signal that demonstration source video and/or OSD produce and/or IC300 produce from the output signal of amplifier 510.

Controller 301 is also carried out a program that comprises various algorithms that is stored in the program storage 308.For the ease of initialization adjusting is set, controller 301 is exported a numeric word D on data/address bus 303, and bus is connected to a controlled current source 250.This numeric word D representative is produced and is offered a transducer specific currents of sensor detector 275 by current source 250.

For the ease of regulating and aim at the image of three kinds of colors, produce in the manner described above and set up piece M and be connected to exemplary green CRT.In Fig. 1, express test pattern piece M near transducer S1, as indicated above, the tag block that can produce in order to a vision signal internal timing of overscanning optical grating projection shines each transducer, perhaps by making tag block M illuminate transducer S1 the raster location.Utilize the input of certain shows signal, computer display formats signal for example, all are scanned the zone and can be used to signal and show basically, thereby just can greatly avoid using the operation of overscanning grating.When using a computer the display format signal operation, the grating overscanning is limited in a specified little percentage for example 1%.Therefore, under these are zero overscanning state substantially, can locate by the grating of piece M and illuminate exemplary sensor S1.Obviously, the combination that utilizes video timing signal and grating location or provisional grating to amplify can help the irradiation of each transducer.

Each transducer produces an electron stream, and it can conduct with the exposure intensity that incides on the transducer roughly linearly.Yet the exposure intensity on each transducer is owing to multiple reason has very big variation, and for example, the fluorophor brightness of each CRT might be different, also may be different on lens and optical path between three monochromatic coloured images.Along with wearing out of each CRT, fluorophor brightness meeting descends, and also has by the time in addition, and dust may be deposited in the optical projection path, thereby reduces the exposure intensity on the transducer.Variation between each transducer in sensitivity and intrinsic spectral sensitivity thereof also can cause the variation in sensor current source.

Referring to Fig. 2, produce an exemplary green video piece M with control logic 301 instruction video generators 310, it has an initial non-peak video value, and is positioned at one substantially on level background black or black.Can in each color channel, produce the video blocks that similarly has non-peak video value, its on screen simultaneously and overlapping real estate give birth to, be white image piece of generation on the background of black substantially at one.So just can produce an exemplary green block M and be coupled to green CRT with video generator 310 by amplifier 510.Produce green block M with a microcontroller 301 control of video generators 310 in a level and vertical screen position, shine a specific transducer, for example transducer S1 with the green light that piece M sends.Irradiated transducer can produce one because the electric current that light produces is as described below through the pulse Isen shown in processing generation Fig. 2 of amplifier U280.

Utilize the very big sensor current of 100 pairs of above-mentioned differences of the current loop shown in Fig. 2 to carry out useful compensation, calibration and measurement owing to the light generation.Represented a sensor processor in circuit block 200, its details as shown in Figure 3A.In brief, produce reference current Iref with a numerically controlled current source, that its output state is become is low there not being to offer under the situation of transducer irradiation the bias current Isw of sensor detector 275 as detector 275, and it is no luminous or do not have an irradiation sensor states that this state is used to representative.When transducer when for example S1-S8 is illuminated, handle because the electric charge that light produces forms negative-going pulse Isen with the output at amplifier 280.Negative pulse Isen shifts constant reference current Iref, makes switching current Isw reduction and causes sensor detector 275 to be turn-offed.During by pulse-off, suppose that output is high at detector 275, nominal supply voltage just, being used to representative has illumination or irradiated transducer.The output of sensor detector 275 is the direct impulse signals 202 on the input that is connected to digit convergence IC 300.The rising edge sampling of pulse signals 202 stops level and vertical speed rate counter, so that counting is provided, is used for determining by the position of the transducer of illumination in measuring matrix.

Increase by means of control reference current Iref comes the measuring transducer electric current, when sensor detector 275 switches to the expression transducer and loses irradiation till.Cause detector 275 to indicate that reference current value that transducer loses irradiation and just represented the brightness degree that incides on the transducer.Therefore, this electric current just can be used as transducer and the color specified threshold is handled and stored.Reference current value to different transducers and the storage of different color also is different, but to switch all be to occur in the half that the irradiation value drops to the Isen switching value of measurement equally to detector.

Fig. 3 A has represented the transducer processing block 200 of Fig. 2 in detail, and transducer processing block 200 comprises numerically controlled current source 250, sensor detector 275 and optical pickocff amplifier 280.Current source 250 produces the controlled current flow Iref that amplitude is determined by digital control word D.Data word D is by controller 301 generations and comprise 8 parallel data signal D0-D7 that represent minimum to highest significant position respectively.Each data bit is by the resistance R 1 that is connected in series, and R3, R5, R7, R10, R13, R16 and R19 are connected to corresponding PNP transistor Q1, Q2, Q3, Q4, Q5, Q6, the base stage of Q7 and Q8.Each transistorized emitter is connected to a positive supply+V, and each collector electrode is connected to the emitter of a PNP current source transistor Q9 by each resistance.The electric current that can come oxide-semiconductor control transistors Q9 to send so just with the resistor network that the numeral of emitter resistance R22 and combination in parallel is selected.Current switch transistor collector resistance R 2, R4, R6, R8 and R9, R1 1 and R12, R14 and R15, R17 and R18, the selected resistance value of R20 and R21 increases progressively according to binary sequence.For example, the parallel connection of resistance R 20 and R21 combination approximately is 400 ohm, and resistance combination R17 and R18 approximately are 800 ohm.All the resistance R 22 when all crystals pipe all ends of 200 ohm during conducting produces selects between 100 kilohms at all crystals pipe so just to utilize numeric word D0-D7.Numeric word D0-D7 has the magnitude of voltage of 3.3 volts of zero-sums, chooses resistance when data bit has zero volt magnitude of voltage, and do not choose resistance when this has 3.3 volts of values.So just can determine the amplitude of the reference current Iref that produces on the transistor collector with the base potential of resistance R22 and transistor Q9.

The electric current I ref that numeral is determined is coupled to the base stage of transistor Q10 by resistance R 26, makes this transistor turns.The grounded emitter of transistor Q10, and collector electrode is connected to the amplifier that the emitter of NPN transistor Q11 constitutes a cascode amplifier (cascode) connection.The base stage of a voltage divider bias transistor Q11 who constitutes with resistance R24 and R23.Resistance R 24 is connected to positive supply, and resistance R 23 is connected to ground.When the not conducting of knot of the Base-Emitter of transistor Q11, the node of resistance R 23 and R24 with the base bias of transistor Q9 and Q11 to about 1.65 volts.The collector electrode of transistor Q11 produces one and is used to refer to transducer S1 irradiating state, just has or the output signal 202 of unglazed photograph, this signal is connected to a digit convergence integrated circuit (IC) 300, its model is STV2050 for example, perhaps is connected to the input of a microprocessor.

The sensor detector 275 of Fig. 3 A in the following manner.The base stage that reference current Iref is connected to transistor Q10 is as switching current Isw, but in case when transducer when for example S1-S8 is labeled piece M and shines, by resistance R 27, R28 and capacitor C 4, C3 shifts this reference current Iref, forms sensor current Isen.Switching current Isw makes transistor Q10 conducting and saturated, forces collector electrode to reach about 50 millivolts nominal earthed voltage Vcesat.Therefore, nominally the emitter of transistor Q11 is just tied ground connection by the saturated collector emitter of transistor Q10, and transistor Q11 conducting makes its collector electrode reach 100 millivolts of nominal voltages or (Q3 Vcesat+Q4 Vcesat).The collector electrode of transistor Q11 forms output signal 202, and its nominal zero volt expression is unglazed according to sensor states, and nominal supply voltage is represented irradiated transducer.

Saturated along with transistor Q10, the emitter to base voltage of transistor Q11 is because the effect of resitstance voltage divider R23 and R24 drops to about 0.7 volt of voltage that the saturation voltage by the Base-Emitter junction voltage of transistor Q11 and transistor Q10 constitutes from 1.65 volts of nominals.Because the base stage of current source transistor Q9 and cascode transistor Q11 connect together, the biasing on the base stage of current source transistor Q9 also can drop to 0.7 volt of nominal.This variation of transistor Q9 base potential can cause constant current Iref to increase about three times.

The operation of optical pickocff amplifier frame 280 below will be described.Yet when transducer when for example S1 is illuminated by the tag block of a projection, favourable amplitude and the frequency response meeting handled by amplifier frame 280 form negative current pulse Isen.Because reference current Iref is constant, the electric current I sen of illuminated transducer shifts from the base current of transistor Q10 (Isw), causes this transistor to end.When transistor Q10 ended, transistor Q11 was cut off, and causes its collector electrode to rise to supply voltage, produced the output signal 202 of 3.3 volts of amplitudes of nominal of an illuminated transducer of indication.As mentioned above, transistor Q10 and Q11 by the time, the base bias of current source transistor Q9 is got back to by the definite current potential of resitstance voltage divider (R23 and R24), its result can make the amplitude of constant current Iref descend about 66%.Like this, the decline of reference current Iref just can be for stopping to detect and indication sensor turn-offs or unglazedly sets up a low switch thresholding according to state, thereby advantageously keep or lock the state of illuminated transducer.

It below is the mode of operation of optical pickocff amplifier frame 280.As mentioned above, optical pickocff S1-S8 be arranged on display screen 700 around, and can be connected to single amplifier for example on the U280 with parallel-connection structure, perhaps be connected to corresponding amplifier separately.Yet, the in parallel or selection that connects transducer is not separately had much influences for the quality of the signal to noise ratio of optical sensor signals.

The ambient illumination of display screen and optical pickocff may be a sunlight, and incandescent lamp or fluorophor lamp produce.Typical ambient illumination produces the low frequency waveform signal that slowly changes, and representative drops on sunlight or the artificial light that the intermittence on projection screen and the transducer is blocked.The optical sensor signals that this surround lighting produces comprises that the DC component of a variable amplitude adds a low frequency component.The existence of artificial light can produce the broadband noise frequency spectrum of the extend into mhz frequencies scope relevant with supply frequency.Though the sunlight component may be to eliminate easily, its relevant low frequency variations can cause loss or the weakening by the useful sensor signal of the measurement markers M generation of projection.Fig. 4 A has simulated the sensor signal that is subjected to hypographous sunlight and artificially lighting unnecessary irradiation influence in the process of measuring projection mark M.The waveform that selection is used for simulating shade or intermittent sunlight has triangular waveform, and the peak-peak amplitude is 3 milliamperes, and frequency is approximately 2Hz.The high frequency noise components of representing with cross-hauling is superimposed upon on the triangular waveform.Fig. 4 B represents to produce with CRT and the sensor signal of the corresponding needs of mark M of projection.The cycle that the mark of simulation derives from signal is selected as 4 milliseconds, so that four marks of each display field are measured.The peak value that the mark of simulation derives from sensor signal is 50 microamperes, and the rise time approximately is 50 microseconds, and be 1 millisecond the fall time of nominal.So just can find out that unwanted signal is very disadvantageous with the ratio of the amplitude of useful signal, ratio approximately is 60: 1.

The sensor signal that is input to amplifier U280 include with and the unwanted signal component add the induced signal that other are external.The amplitude of unwanted signal component has been covered the intermittence flash of light of projection measurement piece M greatly.As mentioned above, slowly the low frequency signal that changes may be to be covered by the surround lighting in various sources to produce, the black clouds of Bian Huaing for example, and the motion of bushes or tree, perhaps or even the shadow.Typical broadband noise source is artificial light sources or sunlight.

Since having confirmed the useful and ratio unwanted signal amplitude approximately is 60: 1, optical sensor signals is coupled to amplifier frame 280 eliminates the unwanted signal component basically by signal processing.Represented eight optical pickocff S1 that are connected in parallel to S8 in frame 280, reflector separately is by a low pass filter coupling, and addition on a low-impedance node that forms on the operational amplifier U280 input, and the amplifier model is TLO82 for example.In Fig. 3 A, represented a spuious or parasitic capacitance Cs being connected in series with interference voltage source Vinf.This interference signal source among the figure is in tying of sensor emission device, yet, the interference signal of this electric capacity of ubiquity and coupling in the interconnection of transducer.Constitute a low pass filter with ferrite inductor FB1 that is connected in series and the capacitor C1 that is connected to ground.Stray capacitance Cs and capacitor C1 ratio numerically can decay by radio frequency interference, sweep frequency signal significantly or may cause amplifier U280 misoperation even cause coupling that the high pressure picture tube electric arc component of parts damages produces or the voltage Vinf of induction.

When any optical pickocff was illuminated, one because the electric current that light produces Iill for example flow to low pass filter from ground by the transistorized collector emitter knot of irradiated optical pickocff.The sensor signal current of low pass is provided for the inverting input of operational amplifier U280, and converts low-impedance voltage at output.Feedback resistance R29 is connected to inverting input from amplifier out, produces one and the proportional output voltage of optical pickocff input current.The normal phase input end of amplifier is connected to by the voltage source for example-0.6 volt that is connected voltage divider generation that resistance R 30 between negative 12 volts power supplys and zero volt or the earth potential and R31 constitute.Amplifier U280 is determined with the capacitor C2 that is connected in parallel by feedback resistance R29 to the gain of sensor current, is " height ".This amplifier gain forces the very approaching voltage that equals on the normal phase input end of the voltage on the inverting input, for example negative 0.6 volt.Like this, the voltage on inverting input is used to setover optical pickocff S1 to S8, the voltage constant that each collector emitter is tied.Form a low-impedance voltage pattern that the DC coupling forms of sensor signal at the output of amplifier U280, and its negative amplitude is shone the increase of sensor current just along with transducer and is increased.The negative supply voltage that amplitude is bigger is provided for amplifier U280, so that enough the amplifier allowance (headroom) or the output signal amplitude of oscillation are arranged, the big electric current that produces owing to light that the surround lighting of allowance high level causes produces big negative signal voltage.The ohmic value of feedback resistance R3 is to determine like this, allow the detector 275 of back can differentiate the current impulse that 50 microamperes mark for example derives from, can linearly amplify for example 3 milliamperes the electric current relevant simultaneously with surround lighting, thus the loss of avoiding amplifier overload and feedback loop control and desired signal component to be followed.Feedback resistance R29 and a capacitor C2 are connected in parallel, and select feedback so that frequency to be provided, and the amplifier high frequency response of amplifier U280 are limited in the cut-off frequency of about 58KHz.This high frequency feedback is dwindled the bandwidth of amplifier valuably, thereby reduces the extraneous signal that picks up in unwanted noise and the sensor signal.Fig. 4 C represents the output of amplifier U280, can see little zigzag required marking signal pulse in the drawings.

The output of amplifier U280 is coupled to a load resistance R28 who is connected to ground by capacitor C3 by AC.Capacitor C3 and resistance R 28 constitute the first of a high pass filter.The node of capacitor C3 and resistance R 28 is also connected to capacitor C4, and it and resistance R 27 are connected in series and constitute the second portion of high pass filter.The DC component of the first filter segment filtering environmental light signal because the cut-off frequency of its about 60Hz, can obviously reduce the amplitude of the signal component of the slow variation relevant with the variable shade irradiation of display screen.Yet for example the positive or negative pulse that is produced by useful tagging of flash can be coupled to second filter stage.Negative sense because the voltage peak that light produces is produced by tag block M, the emergent pupil that tag block M is considered to the lens seen on periodic scan and each sensing station is the flash of light that the small size fluorophor on border is produced.Although the nominal frequency of this measurement markers flash of light is 60Hz, its fast rise time and fall time are than the cycle much shorter of 60Hz frequency.Select the time constant of the first high pass filter level, eliminate or obvious the minimizing, thereby prevent detector 275 overloads because the capacitor C3 that the slow variation of surround lighting level causes charges and the influence of discharging current.Generally speaking, feedback amplifier U280 and the configuration of output high pass filter provide a kind of pass band filter characteristic with about 60Hz low-frequency cutoff and about 60KHz high frequency limit.

Expression amplitude frequency response curve in Fig. 5, curve A is represented the optical sensor signals response of feedback amplifier U280, and it is to measure on second filter segment between capacitor C4 and the resistance R 27 when 50 microamperes of sensor current pulses are provided to inverting input.In Fig. 6, curve A is represented the response of feedback amplifier U280 when standing the interference signal of 1 volt of amplitude, and interference signal is by the inverting input that is capacitively coupled to of one 10 picofarad.

The signal through amplification and bandpass filtering from capacitor C3 forms the negative voltage pulse at resistance R 28 two ends.These potential pulses are coupled by AC by capacitor C4 and are converted to current impulse by resistance R 27.Fig. 4 D represents these the required potential pulses on capacitor C4 and resistance R 27 nodes.Capacitor connected in series C4 and resistance R 27 have constituted the second portion of high pass filter level.Capacitor C4 stops DC electric current I ref and is charged to the base potential of detector transistor Q10.Appear at the base stage that all is coupled to transistor Q10 through the positive and negative pulse in the sensor signal of filtering.Positive pulse by the base emitter junction clamp of transistor Q10, and causes transistor Q10 to end from the negative current pulse meeting of deriving from the mark irradiation of the transducer diverted current of constant current Iref by resistance R 26.As indicated above, when transistor Q10 ends, on the collector electrode of transistor Q11, form the logical one value, and form the output signal 202 shown in Fig. 4 E, its magnitude of voltage of 3.3 volts is represented the mark irradiation of transducer.Therefore the amplifier with bandpass shape of the present invention can be eliminated unwanted surround lighting component substantially from optical sensor signals, can set up automatically when screen is subjected to the surround lighting irradiation thus.

Represented that in the circuit of Fig. 3 B one is coupled to high-frequency interferencing signal Vhf on the transducer signal amplifier U280A via exemplary cross-talk mechanisms Css.If this crosstalk components is exaggerated, the transducer signal to noise ratio is reduced, and can in subsequent conditioning circuit, cause the false mark of assembling to detect.According to configuration of the present invention,, utilize the common mode inhibition of operational amplifier just can eliminate this crosstalk signal basically as long as be coupled to the differential input end of amplifier U280.In Fig. 3 B, adopted the Component Design identical, and new parts and numerical value are represented with three numeral numbers with Fig. 3 A.For example 20 ohm resistance R 320 has been adopted in the connection of common mode input, and it is connected between the differential input end of amplifier U280A.The value of bias voltage voltage divider resistance R 300 and R310 is than having increased a factor 2 among Fig. 3 A.The work of this configuration of the present invention is as follows.

High-frequency crosstalk interference signal Vhf shown in Fig. 3 B is coupling in for example between the terminals of adjacent of other amplifier section (not shown) that the TLO82 type IC that comprises amplifier U280A encapsulates by exemplary stray capacitance Css.In addition, between adjacent circuit-board conductors or be coupled in the circuit of inverting input of optical pickocff amplifier U280A and also can crosstalk.The beneficial effect of resistance R 320 is the common mode input signals of normal phase input end formation that a big chunk interference signal are coupled to amplifier U280A.Two inputs are applied substantially the same signal produce an output signal Vo, thereby reduce the amplitude of the crosstalk components Vx that produces by signal Vhf greatly.Yet although attempt two inputs are maintained identical current potential around the feedback of amplifier U280A, resistance R 320 has constituted the part of an attenuator at normal phase input end, to guarantee that two inputs are different.This difference produces negative-feedback signal on inverting input, it partly is coupled to normal phase input end and forms positive feedback, produces a signal peak effect.

The capacitor voltage divider institute dividing potential drop that amplifier U280 is constituted by capacitor Css and C1 the signal gain of crosstalk signal Vhf, for the demonstration numerical value shown in Fig. 3 B, this gain is between 1 to 2 for interference signal in the 30KHz scope.The amplification open-loop gain value that being used for cutting apart the capacitor Cs of interference signal Vinf and capacitor voltage divider that C1 constitutes in the circuit arrangement of this yield value than Fig. 3 A provides reduces significantly.The value of coupling resistance R320 is to select according to the input voltage offset specification of amplifier U280A.The offset voltage of amplifier U280A is exaggerated according to the ratio of the attenuator that forms on normal phase input end, this ratio be parallel resistance R300 and R310 divided by common mode coupling resistance R320, [(R300//R310)/R320].For example, according to the resistance value shown in Fig. 3 B, this ratio approximately is 70: 1, for input off-set voltage for example+/-5 millivolt, operational amplifier can amplify 70 times with this shifted signal, produces approximately at the inverting input of amplifier U280A+/-350 millivolts variation.This is very important for the bias voltage on the optical pickocff S1-S8 being maintained between 0.5 to 3 volt.Because the feedback effect of operational amplifier can attempt two inputs are maintained identical current potential, will form this bias voltage at inverting input.Therefore, inverting input will be followed the tracks of the voltage of normal phase input end.As mentioned above, because the result of decay, the amplifier output voltage swing that this skew causes is bigger than the swing on the normal phase input end.Yet this offset voltage that is exaggerated is unimportant, because low-pass filter capacitance C3 can stop the DC component of amplifier out.The voltage divider that constitutes with voltage divider R300 and R310 forms negative 0.8 volt specified optics sensor bias voltage.Select this bias value to provide enough allowance or head room to keep the transistorized bias voltage of optical pickocff more than 500 millivolts.

Employing is coupled to the resistance R 29 of inverting input and the parallel connection combination of capacitor C2 provides negative feedback from the output of amplifier U280A.This feedback forces the voltage at common-mode resistance R320 two ends to be substantially zero, and therefore, the voltage magnitude of interference signal Vinf equally also can reduce.Because the voltage that feedback produces at common-mode resistance R320 two ends is zero substantially, has stopped sensor current Iill basically, and flow through feedback resistance R29 effectively, at sensor signal voltage Vs of output generation of amplifier U280A by resistance R 320.

Fig. 5 represents a kind of amplitude frequency response curve, the optical sensor signals response of the feedback amplifier U280A that the second filter section office of curve B representative between capacitor C4 and resistance R 27 wherein records, and the input pickup current impulse is 50 microamperes.The curve B of Fig. 6 is represented the response of feedback amplifier U280A when being subjected to influencing by the interference signal that 10 picofarads are capacitively coupled to 1 volt of amplitude of inverting input.

Study respectively indicate A in Fig. 5 and 6 curve as can be seen, the processing configuration of circuit 280 approximately is 2: 1 or 6dB for sensor signal with the ratio provide is provided.Therefore, although the circuit 280 of Fig. 3 A can suppress the transducer response to surround lighting well, pick up with sensor device, can suffer damage because of the ratio minimum of sensor signal but provide the ability that reliable projection mark detects, shown in curve A among Fig. 6 with interferences.The processing configuration of circuit 280A of the present invention is to utilize the common mode input to suppress interference signal to pick up, and provide feedback valuably with coupling resistance R320, as shown in the useful and unwanted signal curve of representing on the curve B in Fig. 5 and 6, this feedback makes the amplitude frequency response reach the highest.Comparison curves B as can be seen, the high frequency response of the logical processing configuration of band is reduced to about 8KHz from about 60KH significantly, this location exceeds the interference signal relevant with scanning of the logical scope of band of the processing configuration of circuit 280A.Resistance R 320 also provides positive feedback from output for normal phase input end by resistance R 29 except being used for the coupling of common mode input.This positive feedback produces a kind of resonance or peak effect in about 7KHz place in the logical frequency range of band, compare with circuit 280 useful signal to be increased about 2.5 times.The curve B of Fig. 5 has shown the useful conversion that 50 microamperes of sensor input signals is transformed into the output signal of about 53 millivolts of amplitudes.Compare with the effect of circuit 280, with respect to interference signal, it is about 1/3rd that final output voltage amplitude drops to, perhaps 3 millivolts.Reduction processor bandwidth is also introduced the ratio that the logical peak value of band can advantageously improve desired signal and undesired signal.Response curve B shown in the comparison diagram 5 and 6 as seen, the sensor signal that circuit 280A provides and the ratio of interference approximately are 16: 1 or 24dB.

The present invention can guarantee the ratio of best sensor signal and interference is offered detector 275 in conjunction with the band-pass response spike of the common mode inhibition of interference voltage signal and generation thereof is carried out electric current to this combination of voltage transformation to sensor current signal.With respect to the description that the configuration shown in Fig. 3 A is done, the sensor signal that coupling is used to detect is constant basically, but has exempted the high-frequency crosstalk interference greatly, keeps the good inhibitory action to ambient illumination simultaneously.

Claims (14)

1. the optical sensor signals processor in the projection display equipment, described processor is characterised in that:

Optical pickocff (S1-S8) produces the sensor signal (Iill) with current component of representing projection grating illumination, and described sensor signal comprises scanning related cross-talk component of voltage (Vinf);

Difference is amplified (U280), be used to respond described sensor signal (Iill) and produce output signal (Vo), described sensor electrical flow component is converted into the sensor voltage component (Vs) of amplification, described crosstalk voltage component is amplified by difference, and wherein said sensor voltage component (Vs) has than the big amplitude of described crosstalk voltage component (Vx) in the described output signal (Vo).

2. processor as claimed in claim 1, the order of magnitude that it is characterized in that described sensor voltage component (Vs) is greater than the relevant crosstalk voltage component (Vx) of described scanning.

3. processor as claimed in claim 1 is characterized in that described output signal (Vo) is coupled and is used for providing negative feedback at first input end, described sensor current (Iill) is converted to the described voltage (Vs) of described output.

4. processor as claimed in claim 1 is characterized in that described output signal (Vo) is coupled and is used for providing negative feedback at first input end, provides positive feedback at second input.

5. processor as claimed in claim 1 is characterized in that described output signal (Vo) is coupled and is used for providing positive feedback at second input.

6. processor as claimed in claim 5 is characterized in that controlling according to the described positive feedback that puts on described second input frequency response of described amplifier (U280A).

7. processor as claimed in claim 5 is characterized in that controllably making described amplifier (U280A) frequency response maximum according to the described positive feedback that puts on described second input.

8. convergence measurement equipment that is subject to signal cross-talk influence that is included in the projection display equipment, described measuring equipment is characterised in that:

Be used to respond the optical pickocff (S1-S8) that incident light produces sensor current signal (Iill) near being positioned at projection screen (700) edge;

Interference voltage signal source (Vinf); And

The amplifier with first and second inputs (U280A) of differential setting, only described first input end is coupled to described optical pickocff (S1-S8), be used to amplify described sensor current signal (Iill), and described first and second inputs are coupled to described interference voltage signal (Vinf) as the common-mode signal input

Described amplifier (U280A) amplifies described sensor current signal (Iill) and described interference voltage signal (Vinf), with the output signal (Vo) that is formed for measuring, described output signal (Vo) has sensor signal component (Vs), and interference signal component (Vx), the amplitude of wherein said sensor signal component (Vs) is obviously greater than the amplitude of described interference signal component (Vx).

9. measuring equipment as claimed in claim 8 is characterized in that described sensor signal component (Iill) and described interference signal component (Vinf) have the signal amplitude ratio of at least one order of magnitude.

10. measuring equipment as claimed in claim 8, it is characterized in that described first input end is coupled to the output of described amplifier (U280A) through feedback resistor (R29), is used for amplifying described sensor signal (Iill) according to the value negative feedback of described resistor (R29).

11. measuring equipment as claimed in claim 8, it is characterized in that described first input end is the inverting input that is coupled to the output of described amplifier (U280A) through feedback resistor (R29), be used to amplify described sensor current signal (Iill), to form voltage signal (Vs) at described output.

12. measuring equipment as claimed in claim 8 is characterized in that described interference signal (Vinf) is coupled to described second input through resistor (R320), to form described common mode input signal.

13. measuring equipment as claimed in claim 8 is characterized in that (R29 R320) is coupled to described second input that is used for positive feedback through feedback resistor for the output of described amplifier (U280A).

14. measuring equipment as claimed in claim 8, (R29, value R320) is got extreme value according to the feedback resistor that is coupled to described second input that is used for positive feedback to it is characterized in that the frequency response of described amplifier (U280A).

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