According to 35 U.S.C.119 (e), the application requires the U.S. Provisional Patent Application sequence number No.60/404 of submission on August 13rd, 2002,156 priority.
Background technology
In recent years, there is one type semiconductor equipment, is known as digital micromirror device (DMD), comprise the removable micro-reflector of a plurality of independences that is arranged in the rectangular array.Latch therein under the control of respective drivers unit of a bit, each micro-reflector is that the limited radian of the 10-12 ° of order of magnitude rotates along the typical case.During the bit that latched before applying " 1 ", driver makes its micro-reflector unit rotational that is associated to primary importance.On the contrary, be applied to actuator unit before the bit " 0 " that latchs make actuator unit that the micro-reflector that it is associated is turned to the second place.By between light source and projecting lens, suitably locating DMD, when by its respective drivers unit rotational during to primary importance, the independent micro-reflector of each of DMD will reflex on the display screen from the rays pass through lens of light source, thereby illuminates the independent pictures element (pixel) in the display.When turning to its second place, each micro-reflector reflects light away from display screen, makes corresponding pixel present dark.An example of this DMD equipment is from Texas Instrument, the DLP of Dallas Texas
TMThe DMD of optical projection system.
At present, adopted the optical projection system of the DMD of the above-mentioned type to keep " unlatching " (promptly therebetween by the independent micro-reflector of control, turn to its primary importance) and micro-reflector maintenance " closing " therebetween is (promptly, turn to its second place) the duty factor compared of the time interval, control the brightness (illumination) of each pixel.。For this reason, the optical projection system of this present DMD type changes the duty ratio of each micro-reflector by the state according to pulse in the sequence of pulse width segment, uses pulse width modulation control pixel brightness.Each pulse width segment comprises the pulse train of various durations.The state of each pulse in the pulse width segment (that is, each pulse is to open or close) has determined that micro-reflector is held open or closes in the duration of this pulse.In other words, the width summation of the pulse in the pulse width segment of opening (being activated) is big more, and the duty cycle of each micro-reflector is just long more.
In the TV projection system of using DMD, frame time shows that promptly the time between the consecutive image is depended on selected television system at interval.The frame time interval that the current TSC-system formula of using in the U.S. needs 1/60 second, and the eurovision standard has been used 1/50 second frame time interval.At present, typically, DMD type TV projection system is by realizing colored the demonstration at each frame time simultaneously or in a sequence projection red, green and blue of interim image.Typical sequence DMD type optical projection system has been used the motor driven color wheel in the light path that is inserted in DMD.Color wheel has the primary color windows of a plurality of separation, and the typical case is a red, green and blue, thereby during the continuous time interval, red, green and blue light can drop on the DMD respectively.In order to realize colour picture, in the time interval, red, green and blue light must drop on the DMD last time at least at each successive frame.If only produce red, green and blue images and each expend frame time at interval 1/3, then between generation has the discernable colored color of interrupting of motion, can postpone by time of occurrence.At present, the DMD system has reduced the delay between the color thus by each color being divided into several time intervals and solving this problem according to the time-interleaved described time interval.
Be subjected to the infringement of transient motion profile by a small margin thereby have the pulse width modulation optical projection system that a plurality of images that produce each primary colours in each frame time interim produce the above-mentioned type of colour pictures through regular meeting, for example with scene in motion or those profiles of being associated of beholder's eyes.Such puppet resembles the variation that is derived from the light pulse distribution of passing different display cycle parts.
United States Patent (USP) 5,986,640 disclose a kind of by cutting apart the scheme that the highest significant bit in the pulse width segment sequence between two or more time adjacent segment (time interval) reduces motion outline.Although this scheme is used to reduce profile, it can not eliminate the profile in all transition.In addition, come partition bit can increase the number of times that must carry out addressing, increased the bandwidth that realizes that this addressing is required thus each pixel according to the mode that is enough to reduce profile.
Therefore, need a kind of operating impulse width modulated technique for displaying that is used for,, overcome the problems referred to above of prior art simultaneously to reduce motion outline.
Embodiment
Fig. 1 shows application report " the veneer DLP that publishes June calendar year 2001 in Texas Instrument
TMThe optical projection system optics " in the present pulse width modulated display system 10 of open type, at this it is merged reference.System 10 comprises the lamp 12 of the focus that is positioned at paraboloidal reflector 13, and paraboloidal reflector 13 reflexes to integrator rod (integrator rod) 15 from lamp by color wheel 14 with light.Motor 16 rotary color wheel discs 14 are so that be provided with an independently red, green and blue primary color windows between lamp 12 and integrator rod 15.In exemplary embodiments shown in Figure 2, color wheel 14 has red, green and blue color windows 17 relative respectively on diameter
1With 17
4, 17
2With 17
5And 17
3With 17
6Therefore, when motor 16 during according to the color wheel 14 of counter clockwise direction rotation diagram 2, red, green and blue light can arrive the integrator rod 15 of Fig. 1 according to the order of RGBRGB.In practice, motor 16 is with sufficiently high speed rotary color wheel disc 14, so that 1/60 second frame time interim, each in the red, green and blue light arrived integrator rod five times, has produced 15 width of cloth coloured images in the frame time interval.Exist and to be used for providing continuously three primary colors each other mechanism.For example, colored (scrolling) mechanism (not shown) that rolls also can be carried out this task.
With reference to figure 1, when its during by one in the continuous red, green and blue color window of color wheel 14, integrator rod 15 will focus on from the light of lamp 12 on one group of relay optics 18.Relay optics 18 is separated into a plurality of collimated light beams that arrive folding mirror 20 with light, and folding mirror 20 arrives beam reflection on total internal reflectance (TIR) prism 23 by one group of lens 22.TIR prism 23 reflexes to digital micro-mirror (DMD) 24 with collimated light beam, and for example the DMD equipment of being made by Texas Instrument is used for optionally reflexing to projecting lens 26 and screen 28.
DMD24 adopts has the form of the semiconductor equipment that is arranged on a plurality of individual mirrors (not shown) in the array.As an example, the DMD that is made and sold by Texas Instrument has the reflection mirror array that 1280 row are taken advantage of 720 row, has produced 921,600 pixels of the dependent picture that projects on the screen 28.Other DMD can have different speculum settings.As previously mentioned, be latched in the state of the binary bits in the actuator unit before the response, under the control of respective drivers unit (not shown), each micro-reflector among the DMD rotates relevant limited radian.Each micro-reflector rotates respectively and depends on that the latched bit that is applied to actuator unit is first and second positions of " 1 " or " 0 ".When being diverted its primary importance, each micro-reflector light is reflexed in the lens 26 and screen 28 on, to illuminate corresponding pixel.When each micro-reflector kept turning to its second place, corresponding pixel presented dark.Each micro-reflector reflexes to time interval (micro-reflector duty cycle) on the screen 28 by projecting lens 26 with light and has determined the brightness of pixel therebetween.
Standalone Drives unit among the DMD24 receives the drive signal from the drive circuit 30 of type known in this field, described drive circuit is with paper " High Definition DisplaySystem Based on Micromirror Device ", and the circuit described in the R.J.Grove et al.InternationalWorkshop on HDTV (in October, 1994) (being merged reference at this) is an example.Drive circuit 30 produces the drive signal that is used for the DMD24 actuator unit according to the pulse width segment sequence 31 that is added to drive circuit by processor.Each pulse width segment comprises the pulse train of various durations, and the state of each pulse has determined that micro-reflector is held open or closes in the duration of this pulse.Typically, in a pulse width segment (sometimes being known as least significant bit or LSB) but in the shortest energy impulse that can occur (promptly, the 1-pulse) have duration of 15 microseconds, and each the big pulse in the section has the duration of the integral multiple in the LSB time interval.In fact, each pulse in the pulse width segment and its state have determined in the corresponding arteries and veins it is that a bit in unlatching or the digital bit stream of closing is corresponding.The be activated pulse of (unlatchings) of a bit " 1 " expression, and a bit " 0 " is represented by the pulse of deexcitation (closing).
By wherein showing the following example of Fig. 1 midfield sequence system of each primary colours, can understand the motion outline Method for minimization of present principles well according to five pulse width segment.Each pulse width segment has the overall width of 51 LSB, therefore each sequence of five pulse width segment has the total pulse widths of 255 LSB, thus, have the given color of 15 milliseconds of duration for each LSB (1-pulse) typical case, can make each pixel have one of 256 intensity levels.Therefore, the pulse width segment of each 51LSB has 765 milliseconds duration.
Table 1 shows in each of five sections that comprise pulse width sequence, the setting of LSB.
Table 1
Section |
Pulse duration (LSB) |
Section 1 |
7 4 13 2 13 6 6 |
Section 2 |
7 7 13 1 13 4 6 |
Section 3 |
7 4 13 2 13 6 6 |
Section 4 |
7 7 13 1 13 4 6 |
Section 5 |
7 4 13 2 13 6 6 |
According to present principles, the adjacent minimum effective bit (that is, the 1-pulse) at brightness changes when one or more other pulses become activation, makes the motion outline minimum by number and the width minimum that makes the pulse that becomes deexcitation.In fact, in order to increase pixel brightness, selected pulse in activating one or more sections, thereby at each pixel brightness boundary place in succession, another still unactivated big duration pulse (promptly, in the embodiment of demonstration is the 13-pulse, or the combination of pulse, for example 7-pulse and 6-pulse) become activation.In addition, when reaching previous pixel brightness boundary, the big duration pulse of each that is activated before (or combination of pulse) keeps activating.To become activation and be called " thermometer code " pulse with each the big duration pulse (or combination of pulse) that reaches given pixel brightness boundary, this is because in case be activated, this thermometer code pulses keeps activating, simultaneously also according to mercurial thermometer in the similar mode of mercury, on this pixel brightness boundary, increase pixel brightness.(when reaching particular temperature level, the increase of response temperature, mercury continues to be elevated on this level).According to the width (that is, the duration) of each pulse in each section, given pulse width segment can have a plurality of thermometer code pulses.
Fig. 3-6 shows the pulse diagram of pulse width segment sequence in the mode of combination, and described pulse width segment sequence has been represented to be among the intensity level #0-#255 the corresponding pixel at given color of each.In an illustrated embodiment, select section 3 to be activated as its thermometer code pulses first section, wherein along with pixel brightness is increased on this boundary, being activated keeps activating with each thermometer code pulses that reaches pixel brightness boundary.As shown in Figure 3, reach intensity level #1 and need activate the 1-pulse.Because section 3 does not have the 1-pulse in this example, activate the 1-pulse in the section 2.In order to reach pixel brightness level #2, at this intensity level place, the 2-pulse in the section 3 becomes activation, the 1-pulse deexcitation in the section 2.In order to reach pixel brightness level #3, the 2-pulse in 1-pulse in the section 2 and the section 3 becomes activation.
In order to reach intensity level #4, at this intensity level place, the 4-pulse in the section 3 becomes activation, the pulse deexcitation of Ji Huoing before.In order to reach pixel brightness level #5 each in the #12, select one of 4-pulse, 2-pulse and 6-pulse (first) in the section 3, and the 1-pulse in the section 2 becomes activation.Reach intensity level 13# (having constituted first pixel brightness boundary), all other pulses at this pixel brightness level place of deexcitation by the 13-pulse (first) that activates in the section 3.
In order to reach intensity level #14, activate the 1-pulse in the section 3, the 13-pulse (first) in the section 3 keeps activating.Therefore, on first pixel brightness boundary (intensity level #13), the 13-pulse (first) in the section 3 keeps activating.Therefore, the 13-pulse (first) in the section 3 has constituted first thermometer code pulses in becoming the section of activation.1-pulse in by keeping the 13-pulse activation in the section 3 and activate that 4-pulse, 2-pulse and 6-pulse (first) from section 3 select one and the section 2 has realized each among intensity level #14 one #25.At intensity level #26 place (having constituted second pixel brightness boundary), the 13-pulse (second) in the section 3 becomes activation, and the 13-pulse (first) in the same section keeps activating.At pixel brightness level #27, two the 13-pulses (first and second) in the section 3 all keep activating, now the 1-pulse activation in the section 2 at this intensity level place.Therefore, the 13-pulse (second) in the section 3 has constituted second thermometer code pulses in becoming the section of activation.
By keeping two the 13-pulses (first and second) in the section 3 to activate, and activate one that selects in of selecting in 7-pulse, 4-pulse, 2-pulse and the 6-pulse from section 3 and the 7-pulse from section 2,1-pulse and the 4-pulse, realized each among the intensity level #28-#61.At intensity level #37 place, activate 7-pulse and 6-pulse (second) in the section 3, along with the increase of pixel brightness level, these pulses all keep activating.Therefore, 7-pulse and 6-pulse (second) have constituted combination temp meter code pulse together in the section 3.Notice that at pixel brightness level #51 place, all pulses in the section 3 become activation.Along with the pixel brightness level increases more than intensity level #51, except the 2-pulse in the section 3, all pulses of other in this section all keep activating.
With reference to figure 4, to locate at pixel brightness level #62 (having constituted adjacent more high pixel brightness boundaries), other all pulses in 13-pulse (first) in the section 2 and the section 3 except the 2-pulse all become activation.In order to reach pixel brightness level #63, activate the 1-pulse in the section 2, all other pulses in 13-pulse (first) in the section 2 and the section 3 except the 2-pulse all keep activating.Therefore, the 13-pulse (first) in the section 2 becomes first thermometer code pulses in this section that is activated.
By the pulse of selection in the activation section 2 and the 2-pulse in the section 3, the further increase that has realized pixel brightness is to reach one of intensity level #63-#74 of Fig. 4, the thermometer code pulses (being 13-pulse (first)) that activated before in its stage casing 2 keeps activating, and all pulses of other in the section 3 keep activating.In order to reach intensity level #75, all pulses in thermometer code pulses that is activated before in the 13-pulse (second) in the section 2, this section and the section 3 except the 2-pulse become activation.Therefore, when reaching relevant pixel brightness boundary, the 13-pulse (second) in the section 2 has constituted second thermometer code pulses in this section that is activated, and increases more than the pixel brightness boundary at this at pixel brightness, keeps activating.
As now understood, in case be activated to reach relevant pixel brightness boundary, for adjacent more high pixel intensity level, big pulse of each in each section (for example 13-pulse) or concentrated combination (for example 7-pulse and the 6-pulse (second) in the section 3) the maintenance activation that comprises the pulse of big duration pulse.Therefore, according to present principles, each this pulse (or combination of pulse) has constituted thermometer code pulses.In the reality, each thermometer pulse has enough big characteristic (that is, having the sufficiently long duration), therefore in case be activated to reach pixel brightness boundary, pulse keeps activating at this intensity level place more than pixel brightness boundary, has limited the pulse sum in the section simultaneously.In other words, at given pixel brightness boundary place, along with pixel brightness is increased on this boundary, single thermometer code pulses (or this pulse combined that comprises thermometer code pulses) becomes and is activated and keeps activating.On the contrary, be reduced to given pixel brightness boundary, have only single thermometer code pulses to become deexcitation, also do not have the thermometer code pulses of deexcitation to keep activating, up to having reached adjacent lower pixel brightness boundary for pixel brightness.Yet, each thermometer code pulses in each section should be not excessive, so that when being activated or during deexcitation, the increment of pixel brightness changes (promptly, it is more senior that pixel brightness is increased to the next one, or pixel brightness is reduced to next even lower level) tangible transition can appear.
In addition, the selection of thermometer code pulses should be used for " exchange " with pulse and is limited in fact individual pulse width section (that is the selection of the pulse that, is activated) to reach specific luminance state.Yet " exchange " that will pulse is limited in fact individual pulse width section (that is the binary pulse setting of modification) to obtain advantage of the present invention.As long as the single thermometer code pulses (or combination of pulse) in single section becomes and activates or become deexcitation between adjacent pixel brightness boundaries, the pulse exchange that then is used to reach particular luminance level can appear between a plurality of sections.
The front has illustrated and has been used for showing the technology that makes the motion outline minimum in pulse width modulation.