WO2012000131A1 - 激光信号调变方法 - Google Patents

激光信号调变方法 Download PDF

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Publication number
WO2012000131A1
WO2012000131A1 PCT/CN2010/000978 CN2010000978W WO2012000131A1 WO 2012000131 A1 WO2012000131 A1 WO 2012000131A1 CN 2010000978 W CN2010000978 W CN 2010000978W WO 2012000131 A1 WO2012000131 A1 WO 2012000131A1
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WO
WIPO (PCT)
Prior art keywords
laser
output
power
signal modulation
period
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PCT/CN2010/000978
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English (en)
French (fr)
Inventor
陈致晓
张聪贤
Original Assignee
宏瞻科技股份有限公司
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Priority to PCT/CN2010/000978 priority Critical patent/WO2012000131A1/zh
Publication of WO2012000131A1 publication Critical patent/WO2012000131A1/zh

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N9/00—Details of colour television systems
    • H04N9/12—Picture reproducers
    • H04N9/31—Projection devices for colour picture display, e.g. using electronic spatial light modulators [ESLM]
    • H04N9/3141—Constructional details thereof
    • H04N9/315—Modulator illumination systems
    • H04N9/3161—Modulator illumination systems using laser light sources
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00—Projectors or projection-type viewers; Accessories therefor
    • G03B21/14—Details
    • G03B21/20—Lamp housings
    • G03B21/2006—Lamp housings characterised by the light source
    • G03B21/2033—LED or laser light sources
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B21/00—Projectors or projection-type viewers; Accessories therefor
    • G03B21/14—Details
    • G03B21/20—Lamp housings
    • G03B21/208—Homogenising, shaping of the illumination light

Definitions

  • the invention relates to a laser signal modulation method, in particular to a laser signal modulation method using PWM (Pulse Width Modulation) and PAM (Pulse Amplitude Modulation) hybrid architecture.
  • PWM Pulse Width Modulation
  • PAM Pulse Amplitude Modulation
  • the small portable electronic device can display small images on any plane that can project images through micro-projection technology, and does not need a fixed screen, so it can be easily used by users. Watch the enlarged image.
  • Applications include automotive/air head-up displays (HUD), satellite navigation systems, smart phones, personal computers, toys and other consumer electronics.
  • the micro-projection technology can be basically divided into two types.
  • the first type of technology uses a light emitting diode (LED) or a laser as a backlight, through digital light processing (DLP), liquid crystal display (liquid crystal display). , LCD).
  • DLP digital light processing
  • LCD liquid crystal display
  • Grating or liquid crystal on silicon (LCoS) display technology to determine the image, and then expand the small image to the projection screen through the lens, allowing viewers to easily view larger images.
  • the second type of technology is laser scanning projection. First, the red, green, and blue primary laser beams are modulated, and then rotated by the micro-electromechanical systems (MEMS).
  • MEMS micro-electromechanical systems
  • the deflection angle and high-speed rotation change the direction after the incident laser beam is reflected, and the modulated red/green/blue three-color laser beam is quickly scanned on the screen to be imaged by the human eye.
  • the laser scanning projection technology consumes less light energy, about one-quarter to one-fifth of the first type of projection technology.
  • the laser projection technology does not use the focus imaging mechanism, so the image can be displayed on an uneven plane, and the image focal length does not need to be adjusted during development.
  • the architecture of laser scanning projection technology is relatively simple, and it is superior to the first type of projection technology in terms of miniaturization and production cost.
  • the total energy of the light emitted/reflected/diffused in a certain space is proportional to the color gradation corresponding to this space.
  • a certain pixel The total light energy of the diffused specific basic color light (R, G, B) is proportional to the total light energy of the basic color laser light projected on the pixel, that is, proportional to the optical power sum of the laser light in the pixel period ⁇ ⁇ ⁇ , Pixel period T PKA represents the total time that the laser beam is projected on a certain pixel.
  • the red, blue, and green color lasers of the laser beam are modulated in the pixel period T PKE L , and by individually changing the color levels of the three primary colors, the sum of the three primary color lasers can achieve the desired pixel.
  • the color of the presentation is a simple color of the presentation.
  • FIG. 1 which is a schematic diagram of a DC laser signal modulation technology in the prior art
  • the horizontal axis is time and the vertical axis is output power
  • the pixel period T PKA represents the total time that the laser beam is projected on a certain pixel.
  • the laser can provide different output power according to the color gradation to be displayed by the pixel, but in each pixel period T PKE , the laser power maintains a specific value, which is for the pixel to be displayed Color gradation. Therefore, in a specific pixel period T PK ⁇ in the DC laser signal modulation technique, the output energy of the laser is proportional to the output value of the laser power.
  • the laser beam sequentially scans adjacent pixels in a predetermined direction, so that two adjacent pixels are prone to color mixing at the boundary.
  • the projection screen contains a rough surface
  • the reflected wave will be generated due to the slight height change. Scattering causes the phase of the laser light projected onto the screen to be randomly modulated.
  • an interference phenomenon is formed, which randomly augments or attenuates the image spot to produce a light and dark spot. This situation is called a laser speckle and affects the quality of the projected image.
  • the semiconductor laser power output at a fixed current will mutate, affecting the accuracy of the laser output power, easily causing the color and brightness to deviate from a predetermined value, and reducing the contrast ratio of the display.
  • the main object of the present invention is to provide a laser signal modulation method for laser signal modulation using PWM (Pulse Width Modulation) and PAM (Pulse Amplitude Modulation) hybrid architecture.
  • the method which divides the active period of a laser into N time units, so that the laser can output energy in an nth time unit, where n is an integer between 1 and N;
  • the maximum effective output power of the laser is divided into M power units, so that the laser can provide the effective output power including m power units, where m is an integer between 0 and M; and the total output of the laser in one active period
  • the power is divided into two light energy unit blocks, and based on the total energy required to display an Rth color gradation Determining the values of m and n, where R is an integer between 1 and MxN; finally, summing the output energy in each light energy unit block to provide the total energy required to display the Rth color gradation; Therefore, the accuracy of the laser power output value is improved, the bandwidth requirement
  • a further object of the present invention is to provide a laser signal modulation method, wherein when the laser is applied to scan projection display, the method further comprises: stopping the energy output of the laser when the laser scans between two pixels; When the scanning position of the laser is not close to the boundary point of one pixel, the laser outputs energy to scan one pixel in an active period; wherein when the scanning position of the laser is close to a boundary point of one pixel, the laser stops outputting energy.
  • the pixel period T PKE represents the total time that the laser beam is projected on a certain pixel.
  • the laser beam does not always turn on in the pixel period ⁇ ⁇ ⁇ , but the laser beam is turned off for a period of time near the pixel boundary point, and the closing time is in the laser off period (laser off period) ) T.
  • FF said.
  • the time of FF is defined as the laser acting period T 0N .
  • the invention further shuts down the period T during the laser.
  • the FF stops output to improve the color mixing of the pixel boundaries, while using the architecture of the light energy block to control the laser activity period T. Laser output in N.
  • the present invention provides a laser signal modulation method, comprising:
  • the active period of a laser is divided into N time units so that the laser can output energy in a time period of eleventh time unit, where n is an integer between 1 and N;
  • the output energy within each light energy unit block is summed to provide the total energy required to display the Rth color scale.
  • the length of each time unit in the time unit is equal.
  • each power unit of the one power unit is equal in size.
  • the laser signal modulation method of the present invention further comprises: Providing a current source for driving the laser, wherein the current source has a bandwidth sufficient to drive the laser to provide an effective output power of m power units in each time unit of N time units, wherein m is between 0 and M The integer.
  • the laser signal modulation method of the present invention further comprises:
  • the first current source has a bandwidth sufficient to drive the laser to provide effective power output of m power units in each time unit of N time units, where m is between 0 and M An integer between
  • the second current source has a bandwidth sufficient to drive the laser to provide a set of effective output power values in a time unit, wherein the set of effective output power comprises one power unit;
  • the first and second current sources drive the laser in accordance with the total energy required to display the Rth color gradation.
  • the laser signal modulation method of the present invention further comprises:
  • the drive current provided by the particular number of current sources is summed to drive the laser.
  • the output signals of the plurality of sets of current sources are synchronized.
  • the output signals of the plurality of sets of current sources are not fully synchronized, so that the output signals between the plurality of sets of current sources have different time delays.
  • the laser signal modulation method of the present invention further comprises:
  • the laser is driven such that the initial portion and the terminating portion of the active period comprise more light energy unit squares than the central portion of the active period.
  • the laser signal modulation method of the present invention further comprises:
  • the laser is driven such that the difference in the number of light energy unit blocks contained in two adjacent time units in the active period is greater than a predetermined value.
  • the laser signal modulation method further comprises: stopping the energy output of the laser when the laser scans between adjacent pixels, wherein the pixel period T PKEL represents The total time the laser beam is projected onto a pixel, when the laser beam is turned on within a pixel period T PKE but the laser beam is turned off for a period of time near the pixel boundary point to close the period T by the laser.
  • FF indicates that the laser is turned off during each pixel period T PKE L .
  • the time outside the FF is the laser activity period ⁇ . ⁇ said, The laser is turned off during the laser cycle T.
  • the unit of time is a pulse.
  • the laser signal modulation method of the present invention can reduce the number of stages of laser power, thereby reducing the precision of the laser power output value.
  • the present invention also reduces the number of signal changes required in the pixel period 1 ⁇ , thus reducing the bandwidth requirements for the laser.
  • each pixel can be elastically period T PKa laser power is adjusted pulse width or size, to achieve the target optical power by changing the total period T PKa pixel of a color Order.
  • FIG. 1 is a schematic diagram of a conventional DC signal modulation technique in the prior art
  • FIG. 2 is a schematic view of the imaging of the present invention
  • FIG. 3 is a schematic diagram of a laser signal modulation method for a PAM used in the present invention.
  • FIG. 4 is a schematic diagram of a laser signal modulation method using PWM in the present invention.
  • FIG. 5 is a schematic diagram of a laser signal modulation method using a PNM according to the present invention.
  • FIG. 6 is a schematic diagram of a laser signal modulation method using a PWM/PAM architecture in the present invention
  • FIGS. 7A-7B are schematic diagrams showing a specific color gradation of a PWM/PAM laser signal modulation method according to the present invention.
  • FIG. 8 is a schematic view of a first embodiment of the present invention.
  • FIGS. 9A-9C are schematic views of a second embodiment of the present invention.
  • Figure 10 is a schematic view of a third embodiment of the present invention.
  • FIGS. 11A-11D are schematic diagrams showing a specific color gradation according to a third embodiment of the present invention.
  • Figure 12 is a schematic view of a fourth embodiment of the present invention.
  • Figure 13 is a schematic view showing a fifth embodiment of the present invention.
  • Figure 14 is a schematic view of a sixth embodiment of the present invention.
  • Figure 15 is a schematic view showing the pulse form of the present invention.
  • Figure 16 is a schematic view of a seventh embodiment of the present invention.
  • T PD ⁇ - pixel period T. FF -laser off period; T. N - laser activity period; Pmax - maximum effective output power; TP - maximum laser activity period.
  • the horizontal axis is time and the vertical axis is output power.
  • the pixel period T PKa represents the laser beam without considering the output size of the laser.
  • the total time projected on a pixel. Produces a color when projection laser scanning technology to display images, since each pixel to be represented in different colors, in order to avoid the same laser beam across adjacent pixels at the boundary of two mixed, the laser beam is not in the pixel period T P dish It is turned on all the time, and the laser beam is turned off for a period of time near the pixel boundary point. This period of off time is represented by the laser off period T 0FF .
  • the time other than the laser off period 1 ⁇ is defined as the laser acting period T. N.
  • the present invention stops output at the laser off period T OTF to improve color mixing of pixel boundaries while employing the architecture of the light energy block to control the laser output in the laser activity period TON.
  • FIG. 3 is a schematic diagram of a laser signal modulation method using PAM (Pulse Amplitude Modulation) in the present invention; wherein, the laser can provide different output power according to the color gradation to be displayed by the pixel, but in each laser activity During the period T QN , the laser power is maintained at a specific value, which is the color gradation to be displayed for the pixel. On the other hand, the length of each laser activity period T QN is fixed and does not change with the gradation of the pixel. Therefore, in the PAM laser signal modulation method of the present invention, the output light energy of the laser is proportional to the output value of the laser power in a specific laser activity period T QN .
  • PAM Pulse Amplitude Modulation
  • FIG. 4 is a schematic diagram of a laser signal modulation method using PWM (Pulse Width Modulation) in the present invention; wherein, all laser activity periods T.
  • the laser power in N is a fixed value and does not change with the color gradation of the pixel.
  • the pulse width of ⁇ is determined by the color gradation that the pixel wants to display. Therefore, in the M laser signal modulation method of the present invention, a specific laser activity period T is performed. In N , the output energy of the laser is proportional to the pulse width.
  • FIG. 5 is a schematic diagram of a laser signal modulation method using pulse number modulation (PNM) according to the present invention; wherein, each laser activity period T.
  • PPM pulse number modulation
  • a pulse wave having an output power value and a pulse width equal to each other can be generated in N , and the number of pulse waves is determined according to the color gradation to be displayed by the pixel. Therefore, in the PM laser signal modulation method of the present invention, a specific laser activity period T is performed. In N , the light output energy of the laser is proportional to the number of pulses.
  • the present invention uses the architecture of the light energy block to control the laser activity period T.
  • the laser output in N drives the laser.
  • FIG. 6 which is a schematic diagram of a laser signal modulation method using a PWM/PAM hybrid architecture according to the present invention, which displays a laser activity period T of the laser.
  • N- intra-optical power-time characteristic map where the vertical axis represents the output power of the laser, which is divided into M basic power units, which can provide different output power values of M groups, wherein the m-th group output power includes m basic power units.
  • the laser can provide a specific output power value for a particular output period, the length of the particular output period being equal to the sum of the lengths of n basic time units (n is an integer between 1 and N), the specific output power The value is the sum of m basic power units, and the laser activity period is T.
  • the length of N is represented by Tp. Therefore, the cycle of laser activity is rampant.
  • the optical power-time characteristic map in ⁇ can be described by a matrix of R basic unit squares, where R is an integer between 0 and (MxN), representing the number of gradations required to be achieved by the pixel.
  • R is an integer between 0 and (MxN)
  • MxN representing the number of gradations required to be achieved by the pixel.
  • the value of each basic power unit is Pmax/M
  • Tp/N the length of each basic time unit
  • T QN the length of each basic time unit
  • the sum of the number of light energy unit squares in the laser activity period T QN corresponds to the color gradation that the pixel is intended to present.
  • the first color gradation corresponds to the entire laser activity period T.
  • the lasers in N are all zero optical power output, and the Rth color gradation is equivalent to outputting (R-1) light energy unit blocks throughout the laser activity period TON.
  • the 32nd gradation can be represented by any laser output signal occupying 31 light energy unit blocks in the grid power distribution map, for example, as shown in FIG. 7A and FIG. 7B.
  • N is proportional to the bandwidth required for the signal modulation mode of the laser and the driving circuit, the required bandwidth of N must be smaller than the bandwidth that the laser and the driving circuit can operate.
  • the required number of gradations is R
  • selecting a larger N can lower M, and the difference Tp/M of each level of the laser power becomes larger, thereby reducing the precision of the laser power in the gradation control. Requirements, therefore, can extend the effective operating temperature range of this projection system.
  • the present invention can employ different circuit architectures to implement the grid power profile shown in FIG.
  • FIG. 8 it is a schematic diagram of a first embodiment of a laser signal modulation method using a PWM/PAM hybrid architecture according to the present invention.
  • the first embodiment uses a single current source to drive the laser.
  • the bandwidth of the current source enables the laser to provide 0 - Pma output power for a length of Tp/N, and its maximum sweep current is Imax (when The laser power output is the drive current at Pmax).
  • the laser can provide M sets of different output powers (m/M) xPmax in each output period Tp/N to achieve different numbers of light energy unit blocks, where m is the medium An integer between 0 and M.
  • the 134th gradation can be represented by the laser signal output of 133 light energy unit blocks occupying the grid power distribution diagram as shown in Fig. 8.
  • FIGS. 9A-9C are schematic diagrams showing a second embodiment of a laser signal modulation method using a PWM/PAM hybrid architecture according to the present invention.
  • the second embodiment uses two current sources to drive the laser: wherein the scanning current of the first group of current sources can be changed with time, and the bandwidth can enable the laser to output M sets of different output powers in the length Tp (m/ M) xPmax to provide a different number of light energy unit blocks, where m is between 0 and (M-1) An integer between.
  • the scanning current of the second group of current sources does not change with time, and the bandwidth thereof enables the laser to be in length.
  • a fixed value of Pmax/M is output during the Tp/N time to provide a different number of light energy unit blocks.
  • 133 basic light energy blocks are generated when the 134th color gradation is realized, wherein 4x32 basic light energy blocks can be driven by the first set of current sources.
  • the optical power-time characteristic diagram is shown in Fig. 9A; the other five basic light energy blocks are generated by the second group of current sources, and the optical power-time characteristic diagram is as shown in Fig. 9B.
  • Adding the two current sources can use the 133 basic light energy blocks to achieve the 134th color gradation.
  • the summed optical power-time characteristic is shown in Figure 9C.
  • the second embodiment of the present invention requires that the product of the bandwidth and the scanning current be at most (N/Tp) (Imax/M), and therefore the cost is low.
  • FIG. 10 it is a schematic diagram of a third embodiment of a laser signal modulation method using a PWM/PAM hybrid architecture according to the present invention.
  • the third embodiment uses multiple sets of current sources to drive lasers, and each of the current sources has a bandwidth. Not the same.
  • the bandwidth of the i-th current source is sufficient for the laser to generate an optical power of 0 ⁇ (Ai/M) Pmax for a period of time (N/Bi) / Tp, where i is Any integer between 1 and S, Ai is an arbitrary integer between 0 and M, and Bi is an arbitrary integer that makes N/Bi an integer, so the value of (N/Bi) /Tp can be less than the basic unit The value of the bandwidth N/Tp.
  • the scan current of each current source does not change with time, but the maximum scan current is different.
  • the i-th current source can generate an integer set (N/Bi group) AixBi basic light energy squares
  • the scan current of the first set of current sources enables the laser to produce an optical power of (1/2) x Pmax,
  • the bandwidth is 8/Tp, that is, the output period is ⁇ /8;
  • the scanning current of the second group of current sources enables the laser to generate (3 / 8 ) x Pmax optical power with a bandwidth of 16/Tp, which is the output.
  • the period is ⁇ /16;
  • the scanning current of the third group of current sources enables the laser to generate (1/8) xPmax optical power with a bandwidth of 32/Tp, that is, an output period of ⁇ /32.
  • the first set of current sources can provide 0 or 16 basic light energy squares in 8 output cycles (length ⁇ /8), and the second set of current sources can be in 16 output cycles (length ⁇ /16) Providing 0 or 6 basic light energy squares respectively, and the third set of current sources can provide 0 or 1 basic light energy squares respectively in 32 output periods (length ⁇ /32), one current source at one output
  • the maximum number of basic light energy squares that can be provided during the cycle are indicated by the bold lines in Figure 10.
  • a laser activity cycle ⁇ In the middle, it is assumed that the first group of current sources output a total of 16 basic light energy squares (al is an arbitrary integer between 0 and 8), and the second group of current sources outputs a total of 6 basic light energy blocks.
  • three groups in the current source may ⁇ ⁇ pixels within the output cycle ⁇ (16al + 6a2 + a3) basic block number of light energy.
  • 11A-11D are schematic diagrams showing a specific color gradation in a third embodiment of the present invention.
  • the three sets of current sources are during the laser activity period T.
  • the optical power-time characteristics of the first, second, and third sets of current sources are as shown in Fig. 11A, Fig. 11B, and Fig. 11C, respectively.
  • the optical power-time characteristic diagram caused by the summation of the three sets of current sources is as shown in Fig. 11D, so that the 134th color gradation can be presented in this laser activity period TON.
  • the interference of the homogenous laser will cause the laser spot.
  • the laser spot is more prominent.
  • One way to reduce the laser spot is to reduce the coherence of the laser beam.
  • the frequency of the signal driving the laser is higher, the resonance condition in the laser also changes rapidly, thereby shortening the temporal coherence period of the laser and increasing the bandwidth of the laser to suppress the laser spot.
  • FIG. 12 a schematic view of a fourth embodiment of the present invention.
  • the output of the second set of current sources lags the output of the first set of current sources by Tp/(3xN), and the output of the third set of current sources lags behind
  • the output of the second set of current sources has a time of Tp/(3xN), and the optical power-time characteristic diagram obtained by summing the three sets of current sources and driving the laser is shown in FIG. Compared to the laser activity period T shown in Fig. 1 1D.
  • the laser activity period T QN shown in Figure 12 is longer (2xTp) / (3xN), as long as the laser activity period 1 ⁇ is still less than the pixel period T PKa , then the total light energy in the pixel period T P It will not change due to the non-synchronization of each group of current sources, so it will not affect the control of the color gradation.
  • the laser driving frequency shown in Fig. 12 is three times that of the laser driving frequency shown in Fig. 11D, so that the homology of the laser beam can be reduced and the laser spot can be reduced.
  • FIG. 13 a schematic view of a fifth embodiment of the present invention. Also illustrated in a 256-level system, choose
  • Fig. 13 is a graph showing the optical power-time characteristics required for the 134th color gradation.
  • the fifth embodiment uses a high frequency signal to drive the laser light, so that the laser output power is highly random, so that the laser spot can be effectively reduced.
  • the fifth embodiment can adopt the architecture of the first embodiment, and provides a greatly varying driving current in an adjacent output period (length ⁇ / ⁇ ) by a single current source, so that the characteristics of the laser output power are as shown in FIG. .
  • the fifth embodiment can also adopt the architecture of the third embodiment. After appropriately selecting the number of current sources and various parameters, multiple sets of current sources are used to provide greatly varying values in adjacent output periods (length ⁇ / ⁇ ).
  • the drive current is such that the laser output power-time characteristics are as shown in FIG.
  • the time at which the laser beam is scanned at different positions in the same pixel is different.
  • the time at which the ⁇ point is projected is caused by the laser activity period of one pixel.
  • the left edge of the spot of the laser beam exits the point ⁇ .
  • the ⁇ point is projected from the time when the right edge of the laser beam spot contacts the ⁇ point, and ends at the left edge of the laser beam spot away from the ⁇ point.
  • the gamma point is projected from the time when the right edge of the laser beam spot contacts the gamma point, and the laser activity period ⁇ of the pixel is terminated.
  • the time at which the ⁇ point (the center of the pixel) is projected by the laser beam is larger than the time at which the ⁇ point and the ⁇ point (pixel edge) are projected by the laser beam.
  • the spot of the laser beam has the same intensity, because the ⁇ laser signal modulation method is in the laser activity cycle.
  • the output power of the crucible is maintained at a fixed value, so the observer perceives that the light intensity at a position point will be proportional to the time at which the laser beam is projected at this point. In other words, the observer will perceive that the intensity of the light clipped in the pixel is greater than the intensity of the light at the edge of the pixel.
  • the laser spot actually has a strong optical power in the center, and the optical power at the edge of the spot is weak, so the phenomenon of uneven light intensity in the pixel is more obvious. If you can cycle during the laser activity cycle. A higher optical power density is assigned near the starting point and the ending point of the ,, during the laser activity period ⁇ . The central portion of the crucible is assigned a lower optical power density, which increases the uniformity of light within the pixel. If the light intensity can be evenly dispersed in the respective pixels, the picture can be made more natural and the laser spot can be reduced.
  • FIG 14 shows the optical power-time characteristic map required for the 134th color gradation.
  • This sixth embodiment is in the laser activity period T.
  • a denser light energy unit square is allocated near the start point and the end point of N , and during the laser activity period T.
  • the central portion of N is assigned a sparse light energy unit square, so that it is possible to improve the unevenness of the light intensity caused by the difference in scanning time and the uneven energy of the laser beam in the pixel.
  • the sixth embodiment can adopt the architecture of the first embodiment, using a single current source to provide different driving currents in different output periods (length Tp/N), at which time the optical power-time of the laser is as shown in FIG.
  • the sixth embodiment can also adopt the third embodiment structure. After appropriately selecting the number of current sources and various parameters, multiple sets of current sources are used to provide different driving currents in different output periods to make the optical power of the laser- The characteristics of time are shown in Figure 14.
  • the wavelength conversion efficiency of the nonlinear crystal is proportional to the incident laser power over a particular range of optical power. Take a green laser as an example, if the wavelength is about
  • the 1064 nm laser is injected into a nonlinear crystal such as Potassium Titanyl Phosphate ( ⁇ 4/ ⁇ ) or Lithium Niobate, and is converted into a laser with a wavelength of about 532 nm.
  • a pulsed laser beam with a narrow wavelength about 1064 nm
  • a large instantaneous optical power is usually obtained.
  • a schematic diagram of a laser signal modulation method using a pulsed PWM/PAM hybrid architecture of the present invention shows a laser activity period T during laser modulation in a pulsed form.
  • the characteristic map of N internal optical power-time the vertical axis represents the output power of the laser, and is divided into M basic power units, which can provide different output power values of M group, wherein the m-th output power includes m basic power units (m It is an integer between 0 and M, and the maximum effective output power including M basic power units is represented by Pmax.
  • the horizontal axis represents the period, divided into N basic pulse units, and the laser can provide a specific output power value in each basic pulse unit, and the laser activity period T.
  • the length of N is represented by Tp.
  • the optical power-time characteristic map in ⁇ can be described by a matrix of R basic unit squares, where R is an integer between 0 and ( ⁇ ), representing the number of gradations required to be achieved by the pixel.
  • R is an integer between 0 and ( ⁇ ), representing the number of gradations required to be achieved by the pixel.
  • the value of each basic power unit is PmaxVM, and each basic pulse unit has the same length, so each basic light energy square corresponds to the same light energy, and the laser activity period T.
  • the sum of the number of light energy unit squares in N corresponds to the color gradation that the pixel is intended to present.
  • the maximum effective output power Pmax of the laser of FIG. 15 is larger than the maximum effective output power Pmax of the laser of FIG. 6, but by combining the wavelength conversion of the nonlinear crystal, the power consumption can be reduced. Get the same amount of laser light energy. At the same time, it is necessary to modulate the laser in pulse form. The bandwidth can therefore reduce the coherence of the laser beam and reduce the laser spot.
  • FIGS. 7-14 can also be applied to the pulse form PWM/PAM laser signal modulation method shown in FIG. 15, and only one example is given here.
  • a seventh embodiment of the present invention uses a pulsed PWM/PAM architecture for laser signal modulation' method.
  • the optical power-time characteristic diagram similar to that shown in Fig. 14 can be realized in the seventh embodiment except that it can pass through the laser activity period T. Different optical power densities are allocated at different time points of N to increase the uniformity of light in the pixel.
  • the laser can be modulated by pulse to reduce the coherence of the laser beam and reduce the laser spot.
  • the present invention can reduce the number of stages of laser power, thereby reducing the precision of the laser power output value.
  • the present invention also reduces the number of signal changes required in the pixel period T PKEIj , thus reducing the bandwidth requirements for the laser.
  • the laser power level or the pulse width can be elastically adjusted in each pixel period T PKE , and the target color level can be achieved by changing the total optical power in the pixel period T PKA . .

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Description

激光信号调变方法 技术领域
本发明有关一种激光信号调变方法，尤指一种采用 PWM (脉波宽度调变， Pulse Width Modulation )及 PAM (脉波振幅调变， Pulse Amplitude Modulation )混合架构 的激光信号调变方法， 适用于显像系统或以激光用于光碟片写录的光学储存系统。 背景技术
随着科技发展， 近年来各种可携式电子装置也越来越普及， 虽然有功能多样化 且携带方便的优点， 但这些小型电子装置上并无足够空间来设置大荧幕。 透过内建 的小荧幕， 使用者在浏览画面时相当辛苦， 更别说是用来阅读电子书或欣赏影片。 因此， 具有低耗能、 体积小和低成本等优点的微型投影技术逐渐地受到瞩目。 除了 自身的内建小荧幕外， 小型可携式电子装置可透过微型投影技术将小影像呈现在任 何可投射影像的平面， 并不需要一固定的荧幕， 因此能让使用者轻松地观赏放大影 像。 其应用范围涵盖汽车 /航空器抬头显示器（ Head Up Display, HUD), 卫星导航系 统、 智能型手机、 个人电脑、 玩具和其它消费性电子等。
微型投影技术基本上可区分为两类， 第一类技术以发光二极管 (light emitting diode, LED)或激光为背光源， 通过数字光源处理技术 (digital light processing, DLP)、 液晶显示 (liquid crystal display, LCD). 光栅 (grating) 或圭基液晶 (liquid crystal on silicon, LCoS)等显示技术来决定影像， 再经透镜将此小影像扩大于投影屏幕， 让观 赏者轻松地检视较大影像。 第二类技术则是激光扫描投影， 首先对红光 /绿光 /蓝光 三原色的激光光束进行信号调变， 接着利用微机电系统 (Micro Electro Mechanical Systems, MEMS)的旋转镜面， 透过上下左右的偏转角度和高速转动来改变入射激 光光束反射后的方向， 将调变后的红 /绿 /蓝三色激光光束在屏幕上快速扫描， 藉由 人眼枧觉暂留来成像。 相对应于第一类投影技术， 激光扫描投影技术的光能消耗较 低， 约为第一类投影技术的四分之一至五分之一左右。 此外， 激光投影技术并非利 用聚焦成像机制， 因此可在不平整的平面显示影样，在显像时亦不需调整影像焦距。 另一方面， 激光扫描投影技术的架构较为简单， 在微型化与生产成本上都比第一类 投影技术占优势。
在人类视觉暂留时间 （约 0.05秒） 内， 在某一个空间内所发射 /反射 /漫射的光 总能量正比于此空间所对应的色阶。 对于激光扫描投影技术的技术而言， 某个像素 所漫射的特定基本色光 (R、 G、 B)的光总能量正比于投射在此像素的基本色激光的 总光能量， 亦即正比于在像素周期 ΤΡΚΕί内激光的光功率总合， 像素周期 （pixel period ) TPKA代表激光光束投射在某一个像素上的总时间。 一般会在像素周期 TPKEL 内对激光光束的红蓝绿三色激光进行调变， 藉由个别改变此三原色的色阶 (color level), 经三原色激光的加总， 便可达成像素所欲呈现的颜色。
参考图 1 , 其是现有技术中一种直流激光信号调变技术示意图， 其横轴为时间， 纵轴为输出功率， 像素周期 TPKA代表激光光束投射在某一个像素上的总时间。在直 流激光信号调变技术中， 激光可依据像素欲显示的色阶来提供不同输出功率， 然而 在每一像素周期 TPKE 内， 激光功率维持一特定值， 此特定值即对于像素欲亙示的色 阶。 因此， 在直流激光信号调变技术中一特定像素周期 TPK ^内， 激光的输出能量和 激光功率的输出值成正比。 在现有技术的直流激光信号调变技术中， 激光光束以一 预定方向依序扫描邻近像素， 因此两相邻像素在边界容易产生颜色混杂。
另一方面， 当使用激光做为影像光源时， 若投影荧幕包含粗燥表面， 当高同调 性 (coherent)的激光光束照射在粗操投影平面上时， 反射波会因细微高度变化时而产 生散射，使得投射到屏幕的激光相位随机地调变。 当这些反射波到达影像接收器 (人 眼)时会形成干涉现象， 随机地加强或减弱影像光点而产生明暗光斑。此种情形称为 激光光斑（ laser speckle ) , 会影响投影画面的品质。 当环境温度变异时， 固定电流 下的半导体激光功量输出将随之变异， 影响激光输出功率的准确度， 容易造成色彩 和亮度偏离预定值， 降低显示画面的对比度 (contrast ratio)。
因此， 对激光扫描投影系统来说， 为了提高显示品质和降低生产成本， 在设计 时存在提高激光功率输出值的精确度、 增加像素内光强度的均勾度及减少激光光斑 的需要， 而本发明即针对上述需要提出有效的解决方巽。 发明内容
本发明的主要目的是提供一种激光信号调变方法， 为一种采用 PWM (脉波宽 度调变 Pulse Width Modulation )及 PAM(脉波振幅调变， Pulse Amplitude Modulation ) 混合架构的激光信号调变方法,.其将一激光的活动周期分为 N个时间单位， 以使激 光能在一第 n个时间单位的时间内输出能量， 其中 n为介于 1和 N之间的整数； 同 时， 将激光的最大有效输出功率分为 M个功率单位， 使激光能提供包含 m个功率 单位的有效输出功率， 其中 m为介于 0和 M之间的整数； 更将激光在一活动周期 的总输出功率分为 ΜχΝ个光能量单位方块， 并依据显示一第 R色阶所需的总能量 来决定该 m和 n的值， 其中 R为介于 1和 MxN之间的整数； 最后， 加总每一光能 量单位方块内的输出能量以提供显示第 R色阶所需的总能量； 藉此， 达成提高激光 功率输出值的精确度、 降低频宽要求、 增加像素内光强度的均匀度及减少激光光斑 的功效。
本发明的再一目的是提供一种激光信号调变方法， 其中当该激光应用于扫描投 影显像时， 更包含： 当激光扫描至临近二像素之间时， 停止该激光的能量输出， 即 当激光的扫描位置未接近一像素的边界点时， 该激光于一活动周期内输出能量以扫 描一像素； 其中当该激光的扫描位置接近一像素的边界点时， 该激光即停止输出能 量。 更言之， 以像素周期 TPKE代表激光光束投射在某一个像素上的总时间， 激光扫 描投影技术应用于影像时， 由于每个像素欲表现的颜色不尽相同， 为了避免同一激 光光束跨越邻近两个像素时在边界产生颜色混杂，因此激光光束在像素周期 ΤΡΚΕ^内 并非一直开启， 而会在像素边界点附近将激光光束关闭一段时间， 此段关闭时间以 激光关闭周期（laser off period ) T。FF表示。 在每一个像素周期 TPKa内， 激光关闭周 期 T。FF之夕卜的时间则定义为激光活动周期 （ laser acting period ) T0N。 本发明进一步 在激光关闭周期 T。FF停止输出以改善像素边界的颜色混杂， 同时采用光能量方块的 架构来控制激光活动周期 T。N内的激光输出。
为了达到上述目的， 本发明提供了一种激光信号调变方法， 包含：
将一激光的活动周期分为 N个时间单位，使该激光能在一第 11个时间单位的时 间内输出能量， 其中 n为介于 1和 N之间的整数；
将该激光的最大有效输出功率分为 M个功率单位， 使该激光能提供包含 m个 功率单位的有效输出功率， 其中 m为介于 0和 M之间的整数；
将该激光在该活动周期的总输出功率分为 ΜχΝ个光能 量单位方块，其中该激 光在每一光能量单位方块内所提供的输出能量由一相对应时间单位的长度和一相 对应功率单位的大小来决定；
依据显示一第 R色阶所需的总能量来决定 m和 η的值，并依此驱动该激光以在 相对应时间单位的时间内提供相对应数目的光能量单位方块， 其中 R为介于 1 和 ΜχΝ之间的整数； 以及
加总每一光能量单位方块内的输出能量以提供显示该第 R色阶所需的总能量。 实施时， 该 Ν个时间单位中每一时间单位的长度相等。
实施时， 该 Μ个功率单位中每一功率单位的大小相等。
实施时， 本发明所述的激光信号调变方法， 更包含： 提供一电流源以驱动该激光，其中该电流源的频宽足以驱动该激光在 N个时间 单位的各时间单位内提供 m个功率单位的有效输出功率， 其中 m为介于 0和 M之 间的整数。
实施时， 本发明所述的激光信号调变方法， 更包含：
提供一第一电流源，其中该第一电流源的频宽足以驱动该激光同时在 N个时间 单位的各时间单位内提供 m个功率单位的有效输出功率， 其中 m为介于 0和 M之 间的整数；
提供一第二电流源， 其中该第二电流源的频宽足以驱动该激光在一时间单位内 提供 1组有效输出功率值， 其中该组有效输出功率包含 1个功率单位； 以及
该第一和第二电流源依据显示该第 R色阶所需的总能量来驱动该激光。
实施时， 本发明所述的激光信号调变方法， 另包含：
提供多组电流源， 该多组电流源中一第 i组电流源的频宽足以驱动该激光以在 Ai个时间单位的时间内输出 Bi个功率单位的方式来输出 Si组 AixBi个光能量单位 方块， 其中 Ai为介于 0和 M之间的整数， 而 N/Bi为整数；
依据显示该第 R 色阶所需的总能量来开启该多组电流源中一特定数目的电流 源； 以及
加总该特定数目的电流源所提供的驱动电流以驱动该激光。
实施时， 该多组电流源的输出信号为同步。
实施时， 该多组电流源的输出信号非完全同步， 使该多组电流源之间的输出信 号互有不同的时间延迟。
实施时， 本发明所述的激光信号调变方法， 更包含：
驱动该激光以使该活动周期的起始部份和终止部份所包含的光能量单位方块 数目多于该活动周期的中央部份所包含的光能量单位方块数目。
实施时， 本发明所述的激光信号调变方法， 更包含：
驱动该激光以使该活动周期中两相邻时间单位所包含的光能量单位方块数目 的差值大于一预定值。
实施时， 当该激光应用于扫描投影显像时， 所述激光信号调变方法更包含： 当激光扫描至临近二像素之间时， 停止该激光的能量输出， 其中以象素周期 TPKEL代表激光光束投射在一像素上的总时间， 当激光光束在一像素周期 TPKE 内开 启但会在该像素边界点附近将激光光束关闭一段时间以激光关闭周期 T。FF表示， 而 在每一个像素周期 TPKEL内激光关闭周期 T。FF之外的时间以激光活动周期 τ。Ν表示， 使激光在激光关闭周期 T。FF停止输出以支善像素边界的颜色混杂。
实施时， 该时间单位是一脉冲。
与现有技术相比，本发明所述的激光信号调变方法，可减少激光功率的阶段数， 因而减少对该激光功率输出值精密度的要求。本发明亦可减少在像素周期1^^中所 需的信号变化次数， 因此减少对激光的频宽要求。在本发明的 PWM/PAM激光信号 调变方法中， 每一像素周期 TPKa中可弹性调整激光功率大小或脉波宽度， 透过改变 在像素周期 TPKa中的总光功率来达成目标的色阶。 附图说明
图 1为现有技术中一直流激光信号调变技术示意图；
图 2为本发明的成像示意图；
图 3为本发明中釆用 PAM的激光信号调变方法示意图；
图 4为本发明中采用 PWM的激光信号调变方法示意图；
图 5为本发明中一种使用 PNM的激光信号调变方法示意图；
图 6为本发明中采用 PWM/PAM架构的激光信号调变方法示意图；
图 7A-图 7B为本发明的 PWM/PAM激光信号调变方法显示特定色阶示意图； 图 8为本发明的第一实施例示意图；
图 9A-图 9C为本发明第二实施例示意图；
图 10为本发明第三实施例示意图；
图 11A-图 11D为本发明第三实施例显示特定色阶示意图；
图 12为本发明第四实施例示意图；
图 13为本发明第五实施例示意图；
图 14为本发明第六实施例示意图；
图 15为本发明釆用脉冲形式示意图；
图 16为本发明第七实施例示意图。
附图标记说明： TPD ^ -像素周期； T。FF -激光关闭周期； T。N -激光活动周期； Pmax- 最大有效输出功率； TP-最大激光活动周期。 具体实施方式
参考图 2， 其系利用本发明激光信号调变方法的成像时示意图， 其横轴为时间， 纵轴为输出功率。在不考虑激光的输出大小的情况下， 像素周期 TPKa代表激光光束 投射在某一个像素上的总时间。 激光扫描投影技术应用于显示影像时， 由于每个像 素欲表现的颜色不尽相同， 为了避免同一激光光束跨越邻近两个像素时在边界产生 颜色混杂， 因此激光光束在像素周期 TP皿内并非一直开启， 而会在像素边界点附近 将激光光束关闭一段时间， 此段关闭时间由激光关闭周期 （ laser off period ) T0FF来 表示。 在每一个像素周期 TPKE 内， 激光关闭周期 1^之外的时间则定义为激光活动 周期 （ laser acting period ) T。N。 本发明在激光关闭周期 TOTF停止输出以改善像素边 界的颜色混杂， 同时采用光能量方块的架构来控制激光活动周期 TON 内的激光输 出。
图 3为本发明中采用 PAM ( Pulse Amplitude Modulation, 脉波振幅调变)的激光 信号调变方法示意图； 其中， 激光可依据像素欲显示的色阶来提供不同输出功率， 然而在每一激光活动周期 TQN内， 激光功率维持一特定值， 此特定值即对于像素欲 显示的色阶。 另一方面， 每一激光活动周期 TQN的长度固定， 不会随像素的色阶而 改变。 因此， 本发明的 PAM激光信号调变方法中， 在一特定激光活动周期 TQN内， 激光的输出光能量和激光功率的输出值成正比。
图 4为本发明中采用 PWM ( Pulse Width Modulation, 脉波宽度调变)的激光信 号调变方法示意图； 其中， 所有激光活动周期 T。N内激光功率皆为一固定值， 不会 随像素的色阶而改变。 另一方面， 在每一激光活动周期！^的脉波宽度则由像素欲 显示的色阶来 ^定。 因此， 本发明的 M激光信号调变方法中， 在一特定激光活动周 期 T。N内 , 激光的输出能量和脉波宽度成正比。
图 5为本发明中采用脉波数量调变 (PNM， Pulse Number Modulation)的激光信号 调变方法示意图； 其中， 每一激光活动周期 T。N内可产生输出功率值和脉波宽度皆 相等的脉波， 而脉波数目则根据像素欲显示的色阶来决定。 因此， 本发明的 P M 激光信号调变方法中， 在一特定激光活动周期 T。N内， 激光的光输出能量和脉波数 目成正比。
为了降低系统频宽要求、 增加像素内光强度的均匀度， 以及减少激光光斑， 本 发明采用光能量方块的架构来控制激光活动周期 T。N内的激光输出驱动激光。 参考 图 6, 其为本发明中一采用 PWM/PAM混合架构的激光信号调变方法示意图， 其显 示在激光的激光活动周期 T。N内光功率-时间的特性图， 其中， 纵轴代表激光的输出 功率， 共分为 M个基本功率单位， 可提供 M组不同输出功率值， 其中第 m组输出 功率包含 m个基本功率单位（ m为介于 0和 M之间的整数 ) , 而包含 M个基本功 率单位的最大有效输出功率以 Pmax表示。 横轴代表周期， 共分为 N个基本时间单 位。 激光可在一特定输出周期内提供一特定输出功率值， 此特定输出周期的长度和 n个基本时间单位的加总长度相等（n为介于 1和 N之间的整数） ， 此特定输出功 率值为 m个基本功率单位的总合， 而激光活动周期 T。N的长度以 Tp表示。 因此， 在 激光活动周期 Τ。Ν中的光功率 -时间的特性图可由 R个基本单位方块所组成的矩阵来 描述， 其中 R为介于 0和 (MxN)之间的整数， 代表像素所需达成的色阶数。 在图 6 所示的实施例中， 每一基本功率单位的值皆为 Pmax/M, 每一基本时间单位的长度 皆为 Tp/N,因此每个基本光能量方块皆对应于相同的光能量，在此激光活动周期 TQN 中光能量单位方块的数量总合即对应于此像素所欲呈现的色阶。 为了说明方便， 在 说明书后续内容会以类似图 6中所示的格状功率分布图来说明本发明的实施例。
将图 6所示的 PWM/PAM混合激光信号调变方式应用在一 256 色阶显示系统 时， 第 1个色阶相当于在整个激光活动周期 T。N中激光皆为零光功率输出， 第 R个 色阶则相当于在整个激光活动周期 TON 中输出 (R-1)个光能量单位方块。 以 M=8, N=32的 256色阶系统为例， 第 32个色阶可由任何占据格状功率分布图中 31个光 能量单位方块的激光输出信号来呈现， 例如图 7A和图 7B所示， 由于 N正比于信 号调变方式的激光与驱动电路所需达成的频宽， N的需求频宽必须小于激光与驱动 电路所能操作的频宽。 同时， 在要求的色阶数为 R的情状下， 选择较大的 N则可降 低 M, 而使得激光功率各阶层的差 Tp/M变大， 因而降低在色阶控制时对激光功率 精准的要求， 因此能扩大此投影系统的有效操作温度范围。
本发明可采用不同电路架构来实现图 6中所示的格状功率分布图。 参考图 8, 其为本发明采用 PWM/PAM混合架构的激光信号调变方法第一实施例示意图。本第 一实施例使用单一电流源来驱动激光， 此电流源的频宽能使激光在长度 Tp/N的时 间内提供 0 - Pma 的输出功率， 其最大扫描电流 (sweep current)为 Imax (当激光功率 输出为 Pmax时的驱动电流)。 透过改变电流源的扫描电流值， 激光在每一输出周期 Tp/N的时间内能提供的 M组不同输出功率 (m/M) xPmax以达到不同数量的光能量 单位方块， 其中 m为介于 0和 M之间的整数。 以 M=8, N=32的 256色阶系统为例， 第 134个色阶可由占据格状功率分布图中 133个光能量单位方块的激光信号输出来 呈现如图 8所示。
参考图 9A-9C,其分别为本发明采用 PWM/PAM混合架构的激光信号调变方法 第二实施例示意图。 本第二实施例使用二电流源来驱动激光： 其中第一组电流源的 扫描电流可随时间而变， 其频宽能使激光在长度 Tp的时间内能输出 M组不同输出 功率 (m/M) xPmax以提供不同数量的光能量单位方块， 其中 m为介于 0和 (M-1)之 间的整数。 其中第二组电流源的扫描电流不随时间而变， 其频宽能使激光在长度
Tp/N的时间内输出固定值 Pmax/M的光功率以提供不同数量的光能量单位方块。以 M=8和 N=32的 256色阶系统为例， 在实现第 134个色阶时需产生 133个基本光能 量方块， 其中 4x32个基本光能量方块可由第一組电流源驱动所产生， 其光功率-时 间特性图如图 9A所示； 另外 5个基本光能量方块则由第二组电流源所产生， 其光 功率-时间特性图如图 9B所示。 将二电流源加总则可利用 133个基本光能量方块来 实现第 134个色阶， 加总后的光功率-时间特性图如图 9C所示。 本发明第二实施例 所需的频宽与扫描电流的乘积最大仅为 （N/Tp ) ( Imax/M ) ， 因此费用较低。
参考图 10, 其为本发明采用 PWM/PAM混合架构的激光信号调变方法第三实 施例示意图， 本第三实施例系使用多组电流源来驱动激光， 每一组电流源的频宽各 不相同。 以使用 S 组电流源为例， 第 i组电流源的频宽足以使激光在 （N/Bi ) /Tp 的时间长度内产生 0 ~ ( Ai/M ) Pmax的光功率， 其中 i为介于 1至 S之间的任意整 数， Ai为介于 0至 M之间的任意整数， 而 Bi为能使 N/Bi为整数的任意整数， 因 此（N/Bi ) /Tp的值可小于基本单位频宽 N/Tp的值。 每一组电流源的扫描电流不随 时间变化， 但其最大扫描电流各不相同， 其中第 i组电流源的扫描电流可使激光输 出达到 （AiM ) Pmax的光功率， 其中 Ai为介于 0至 M之间的任意整数。 若所有 电流源皆以最大扫描电流来驱动， 加总的输出功率至少会大于激光适宜输出的最大 光功率 Pmax, 亦即∑Si=l ( Ai/M ) Pmax≥Pmax。 因此， 本发明第三实施例利用开 关来控制每一电流源的输出， 亦即将 S组电流源的加总输出功率∑ Si=l ( sixAi/M ) Pmax的值控制在 0至 Pmax之间： 当 si=l时， 第 i组电流源会被开启； 当 si=0时， 第 i组电流源会被关闭。
因此， 第 i组电流源能产生整数组（N/Bi组） AixBi个基本光能量方块， 本发 明第三实施例利用开关来控制 S组电流源的输出（ si=l或 si=0 )。 当应用在一 ΜχΝ 色阶系统时， 依据像素欲显示的色阶来决定输出几组 AixBi个基本光能量方块， 使 得 S组电流源输出基本光能量方块的加总数目∑ Si=l aixAixBi为 0至 (ΜχΝ-1)的任 意整数， 其中 ai为介于 0至 N/Bi之间的任意整数， 因此能利用此 S组电流源的电 流总合来实现所需的任何色阶。 以 256色阶系统来说明， 假设选择 M=8和 N=32, 每一基本功率单位的值为 Pmax/8, 每一基本时间单位的值为 Tp/32, 因此每一基本 光能量方块的能量为 (PmaxxTp)/256。本发明第三实施例使用 S组电流源中其中三组 电流源来驱动激光， 同时选择 ( ΑΙ,ΒΙ ) = ( 4,4 ) , ( Α2,Β2 ) = ( 3,2 )且（ Α3,Β3 ) = ( 1,1 )。 换言之， 第一组电流源的扫描电流能使激光产生（ 1/2 ) xPmax的光功率， 其频宽为 8/Tp,亦即输出周期为 Τρ/8;第二组电流源的扫描电流能使激光产生（3 /8 ) xPmax的光功率， 其频宽为 16/Tp， 亦即输出周期为 Τρ/16; 第三组电流源的扫描电 流能使激光产生（1/8 ) xPmax的光功率， 其频宽为 32/Tp, 亦即输出周期为 Τρ/32。 另一方面， 第一组电流源可在 8个输出周期 （长度 Τρ/8 ) 内分别提供 0或 16个基 本光能量方块数， 第二组电流源可在 16个输出周期（长度 Τρ/16 ) 内分别提供 0或 6个基本光能量方块数， 第三组电流源可在 32个输出周期 （长度 Τρ/32 ) 内分别提 供 0或 1个基本光能量方块数， 一电流源在一输出周期内所能提供的最大基本光能 量方块数皆由图 10中的粗体线来标示。 在一激光活动周期 Τ。Ν中， 假设第一组电流 源共输出 al組 16个基本光能量方块数 ( al为介于 0至 8之间的任意整数） ， 第二 组电流源共输出 a2组 6个基本光能量方块数（ a2为介于 0至 16之间的任意整数 ) , 而第三组电流源共输出 a3个基本光能量方块数 ( a3为介于 0至 32之间的任意整数）， 透过加总这三组电流源可在像素周期 Τρκ ^内输出 （ 16al+6a2+a3 )个基本光能量方 块数。 透过选择适当 al、 a2与 a3 , 此三组电流源的总合即可在像素周期 TPKa中建 构 0个基本光能量方块至 255个单位光能量方块， 因此便可在激光活动周期 T。N中 呈现 256个色阶。
参考图 11A-11D, 其分別为本发明第三实施例中一显示特定色阶示意图。 再次 以一 256色阶系统来说明， 同样选择 M=8和 Ν=32 ,且使用三组电流源来驱动激光。 假设像素欲显示第 134个色阶， 这三组电流源在激光活动周期 T。N所输出的基本光 能量方块总数 16al+6a2+a3 需为 133, 可透过 (al,a2，a3)=(8,0,5)、 (4,11,3)或 (3,9,31) 等组合来达成。 假设选择 (al,a2,a3) =(3,9,31), 第一、 二、 三组电流源的光功率 -时间 特性图分别如图 11A、 图 11B、 图 11C所示， 而将此三组电流源加总所造成的光功 率-时间特性图如图 11D所示，因此能在此激光活动周期 TON中呈现第 134个色阶。
如前所述， 同调性激光的干涉会造成激光光斑， 当激光的光能量愈集中， 激光 光斑越为显著。 若要减少激光光斑， 其中一种方式是降低激光光束的同调性。 当驱 动激光的信号频率愈高时， 激光内的共振条件亦快速变化， 因而缩短激光的暂时同 调周期 （ temporal coherence period ) , 并增加激光的频宽以抑制激光光斑。
参考图 12 的本发明第四实施例示意图。 本第四实施例和第三实施例类似， 同 样使用 S组电流源来驱动激光， 但第三实施例中各组电流源的输出信号为同步， 而 本第四实施例中各组电流源的输出信号并非完全同步， 亦即各电流源间可互有不同 的时间延迟。 同样以一 256色阶系统来说明 , 选择 Μ=8和 Ν=32， 且使用三组电流 源来驱动激光以显示第 134 个色阶； 在不考虑时间延迟时， 单一电流源的光功率- 时间特性图分别如图 11A ~图 11C所示。 然而， 在本第四实施例的三组电流源中， 假设第二组电流源的输出落后于第一组电流源的输出有 Tp/(3xN)的时间， 第三組电 流源的输出落后于第二组电流源的输出有 Tp/(3xN)的时间， 则将三组电流源加总后 驱动激光所得的光功率-时间特性图如图 12所示。 相较于图 1 1D所示的激光活动周 期 T。N , 图 12所示的激光活动周期 TQN多了（2xTp)/(3xN)的时间长度， 只要激光活动 周期 1^仍小于像素周期 TPKa , 则像素周期 TP皿内的总光能量并不会因各组电流源 的非同步而改变， 因此不会影响对色阶的控制。 另一方面， 图 12 所示的激光驱动 频率三倍于图 11D所示的激光驱动频率， 因此能降低激光光束的同调性， 减少激光 光斑。
参考图 13 的本发明第五实施例示意图。 同样以一 256 色阶系统来说明， 选择
Μ=8和 Ν=32 , 图 13是显示第 134个色阶所需的光功率-时间特性图。 本第五实施 例使用高频率信号来驱动激光， 使激光输出功率具高随机性， 因此能有效地减少激 光光斑。 本第五实施例可采用第一实施例的架构， 利用单一电流源在相邻输出周期 (长度 Τρ/Ν )内提供变化极大的驱动电流， 以使激光输出功率的特性如图 13所示。 另外， 本第五实施例亦可采用第三实施例的架构， 在适当选择电流源数目和各项参 数后， 利用多组电流源在相邻输出周期 （长度 Τρ/Ν ) 内提供变化极大的驱动电流， 以使激光输出功率-时间的特性如图 13所示。
同一像素内不同位置被激光光束扫描的时间各有不同，以图 3上方所示之 α、 β、 γ点为例， α点被投射的时间起使于一像素的激光活动周期 Τ。Ν开始时， 而终止于激 光光束光点的左侧边缘离开 α点。 β点被投射的时间起使于激光光束光点的右侧边 缘接触 β点时， 而终止于激光光束光点的左侧边缘离开 β点。 γ点被投射的时间起 使于激光光束光点的右侧边缘接触 γ点时，而终止于此像素的激光活动周期 Τ。Ν关闭 时， 因此可知 β点（像素中央）被激光光束投射的时间大于 α点与 γ点（像素边缘） 被激光光束投射的时间。 假设激光光束的光点具同等强度， 由于 ΡΑΜ激光信号调 变方法在激光活动周期 Τ。Ν的输出功率维持一固定值， 因此观察者感受到一位置点 的光强度将正比于激光光束投射在此位置点的时间。 换言之， 观察者将感受到像素 中夹的光强度大于像素边缘的光强度。此外，激光光点实际上在中央的光功率较强， 光点边缘的光功率较弱， 因此像素内光强度不均匀的现象会更为明显。 若能在激光 活动周期 Τ。Ν的起始点与终止点附近分配较高的光功率密度， 在激光活动周期 Τ。Ν的 中央部份分配较低的光功率密度， 如此便能增加像素内光线均匀度。 若能将光强度 较均匀的分散在各别像素中， 不但可使画面较为自然， 亦可减少激光光斑的现象。 参考图 14的本发明第六实施例示意图。 同样以一 256 色阶系统来说明， 选择 M=8和 N=32, 图 14显示第 134个色阶所需的光功率-时间特性图。 本第六实施例 在激光活动周期 T。N的起始点与终止点附近分配较密集的光能量单位方块， 而在激 光活动周期 T。N的中央部份分配较稀疏的光能量单位方块， 因此能改善因扫描时间 长短差异和激光光束能量不均在像素内造成光强度不均勾的情形。 本第六实施例可 采用第一实施例架构， 利用单一电流源在不同输出周期（长度 Tp/N )内提供不同驱 动电流， 此时激光的光功率-时间如图 14所示。 另外， 本第六实施例亦可采用笫三 实施例架构， 在适当选择电流源数目和各项参数后， 利用多组电流源在不同输出周 期内提供不同驱动电流， 以使激光的光功率-时间的特性如图 14所示。
若利用非线性晶体来产生具特定波长的激光功率， 则在特定光功率范围内， 非 线性晶体的波长转换效率正比于入射的激光功率。 举绿光激光为例， 若将波长约
1064纳米的激光射入磷酸钛氧钾（Potassium Titanyl Phosphate, ΚΤΪΟΡΟ4/ΚΤΡ )或 铌酸锂 ( Lithium Niobate )等非线性晶体后， 将转换为波长约 532纳米的激光。 在 此情形下， 使用波长较窄 （约 1064 纳米） 的脉冲激光光束， 将可得到较高的波长 转换效率， 亦即以较少电能消耗来得到同样大小的绿光光能。 另一方面， 以脉冲形 式来调变激光， 通常可得到较大的瞬间光功率。
参考图 15本发明采用脉冲形式 PWM/PAM混合架构的激光信号调变方法示意 图， 其显示以脉冲形式调变时在激光的激光活动周期 T。N内光功率-时间的特性图， 纵轴代表激光的输出功率， 共分为 M个基本功率单位， 可提供 M组不同输出功率 值， 其中第 m组输出功率包含 m个基本功率单位（m为介于 0和 M之间的整数）， 而包含 M个基本功率单位的最大有效输出功率以 Pmax，表示。 横轴代表周期， 共分 为 N个基本脉冲单位， 激光可在每一基本脉冲单位内提供一特定输出功率值， 而激 光活动周期 T。N的长度以 Tp表示。 因此， 在一激光活动周期 Τ。Ν中的光功率-时间的 特性图可由 R个基本单位方块所组成的矩阵来描述，其中 R为介于 0和 (ΜχΝ)之间 的整数， 代表像素所需达成的色阶数。 在图 15 所示的实施例中， 每一基本功率单 位的值皆为 PmaxVM, 每一基本脉冲单位具相同长度， 因此每个基本光能量方块皆 对应于相同的光能量， 在此激光活动周期 T。N中光能量单位方块的数量总合即对应 于此像素所欲呈现的色阶。
由于激光系以脉冲形式调变，因此图 15的激光最大有效输出功率 Pmax，大于图 6的激光最大有效输出功率 Pmax， 但透过结合前述非线性晶体的波长转换， 则可以 较少电能消耗来得到同样大小的激光光能。 同时， 以脉冲形式调变激光时需要较高 的频宽， 因此能降低激光光束的同调性， 减少激光光斑的情形。
和图 6的 PWM/PAM激光信号调变方法类似， 图 7-图 14所示各实施例亦可应 用在图 15所示的脉沖形式 PWM/PAM激光信号调变方法， 在此仅举其中一例来作 说明。 参考图 16本发明第七实施例采用脉冲形式 PWM/PAM架构的激光信号调变 ' 方法示意图。 本第七实施例中能实现类似图 14所示的光功率-时间特性图， 除了能 透过在激光活动周期 T。N的不同时间点分配不同光功率密度以增加像素内光线均匀 度， 同时亦能透过脉冲形式调变激光以降低激光光束的同调性， 减少激光光斑的情 形。
相较于现有技术的激光信号调变技术， 本发明可减少激光功率的阶段数， 因而 减少对该激光功率输出值精密度的要求。本发明亦可减少在像素周期 TPKEIj中所需的 信号变化次数， 因此减少对激光的频宽要求。在本发明的 PW 7PAM激光信号调变 方法中， 每一像素周期 TPKE 中可弹性调整激光功率大小或脉波宽度， 透过改变在像 素周期 TPKA中的总光功率来达成目标的色阶。
以上所示仅为本发明的优选实施例， 对本发明而言仅是说明性的， 而非限制性 的。 在本领域具通常智识者理解， 在本发明专利要求所限定的精神和范围内可对其 进行许多改变， 修改， 甚至等效变更， 但都将落入本发明的保护范围内。

Claims

权利要求
1、 一种激光信号调变方法， 其特征在于， 包含：
将一激光的活动周期分为 N个时间单位，使该激光能在一第 n个时间单位的时 间内输出能量， 其中 n为介于 1和 N之间的整数；
将该激光的最大有效输出功率分为 M个功率单位， 使该激光能提供包含 m个 功率单位的有效输出功率， 其中 m为介于 0和 M之间的整数；
将该激光在该活动周期的总输出功率分为 ΜχΝ个光能 量单位方块，其中该激 光在每一光能量单位方块内所提供的输出能量由一相对应时间单位的长度和一相 对应功率单位的大小来决定；
依据显示一第 R色阶所需的总能量来决定 m和 η的值，并依此驱动该激光以在 相对应时间单位的时间内提供相对应数目的光能量单位方块， 其中 R为介于 1 和 ΜχΝ之间的整数； 以及
加总每一光能量单位方块内的输出能量以提供显示该第 R色阶所需的总能量。
2、 如权利要求 1所述的激光信号调变方法， 其特征在于， 该 Ν个时间单位中 每一时间单位的长度相等。，
3、 如权利要求 1所述的方法， 其特征在于， 该 Μ个功率单位中每一功率单位 的大小相等。
4、 如权利要求 1所述的激光信号调变方法， 其特征在于， 其更包含： 提供一电流源以驱动该激光，其中该电流源的频宽足以驱动该激光在 Ν个时间 单位的各时间单位内提供 m个功率单位的有效输出功率， 其中 m为介于 0和 M之 间的整数。
5、 如权利要求 1所述的激光信号调变方法， 其特征在于， 其更包含： 提供一第一电流源，其中该第一电流源的频宽足以驱动该激光同时在 N个时间 单位的各时间单位内提供 m个功率单位的有效输出功率， 其中 m为介于 0和 M之 间的整数；
提供一第二电流源， 其中该第二电流源的频宽足以驱动该激光在一时间单位内 提供 1组有效输出功率值 , 其中该组有效输出功率包含 1个功率单位； 以及
该第一和第二电流源依据显示该第 R色阶所需的总能量来驱动该激光。
6、 如权利要求 1所述的激光信号调变方法， 其特征在于， 其另包含： 提供多组电流源， 该多组电流源中一第 i组电流源的频宽足以驱动该激光以在
Ai个时间单位的时间内输出 Bi个功率单位的方式来输出 Si组 AixBi个光能量单位 方块， 其中 Ai为介于 0和 M之间的整数， 而 N/Bi为整数；
依据显示该第 R 色阶所需的总能量来开启该多組电流源中一特定数目的电,流 源； 以及
加总该特定数目的电流源所提供的驱动电流以驱动该激光。
7、 如权利要求 6 所述的激光信号调变方法， 其特征在于， 该多组电流源的输 出信号为同步。
8、 如权利要求 6 所述的激光信号调变方法， 其特征在于， 该多组电流源的输 出信号非完全同步， 使该多組电流源之间的输出信号互有不同的时间延迟。
9、 如权利要求 1所述的激光信号调变方法， 其特征在于， 其更包含： 驱动该激光以使该活动周期的起始部份和终止部份所包含的光能量单位方块 数目多于该活动周期的中央部份所包含的光能量单位方块数目。
10、 如权利要求 1所述的激光信号调变方法， 其特征在于， 其更包含： 的差值大于一预定值。
11、 如权利要求 1所述的激光信号调变方法， 其特征在于， 当该激光应用于扫 描投影显像时， 所述激光信号调变方法更包含：
当激光扫描至临近二像素之间时， 停止该激光的能量输出， 其中以像素周期 TPKE代表激光光束投射在一像素上的总时间， 当激光光束在一像素周期 TPKa内开 启但会在该像素边界点附近将激光光束关闭一段时间以激光关闭周期 T。FF表示， 而 在每一个像素周期 ΤΡΚΕ 内激光关闭周期 T。FF之外的时间以激光活动周期 T。N表示， 使激光在激光关闭周期 T。FF停止输出以改善像素边界的颜色混杂。
12、 如权利要求 1所述的激光信号调变方法， 其特征在于， 该时间单位是一脉 冲。
PCT/CN2010/000978 2010-06-29 2010-06-29 激光信号调变方法 WO2012000131A1 (zh)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110515260A (zh) * 2018-05-21 2019-11-29 成都理想境界科技有限公司 一种激光扫描成像的方法以及激光扫描成像设备

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5874981A (en) * 1995-09-19 1999-02-23 Eastman Kodak Company Combined pulse-width and amplitude modulation of exposing laser beam for thermal dye transfer
CN1756099A (zh) * 2004-10-01 2006-04-05 乐金电子(中国)研究开发中心有限公司 功率放大器的驱动电压可调的移动通信终端及控制方法
CN101494796A (zh) * 2008-01-24 2009-07-29 船井电机株式会社 激光投影仪
TW200937101A (en) * 2008-02-29 2009-09-01 Guo-Ren Chen Design method for the modulation of laser color level simultaneously using pulse width and pulse amplitude

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5874981A (en) * 1995-09-19 1999-02-23 Eastman Kodak Company Combined pulse-width and amplitude modulation of exposing laser beam for thermal dye transfer
CN1756099A (zh) * 2004-10-01 2006-04-05 乐金电子(中国)研究开发中心有限公司 功率放大器的驱动电压可调的移动通信终端及控制方法
CN101494796A (zh) * 2008-01-24 2009-07-29 船井电机株式会社 激光投影仪
TW200937101A (en) * 2008-02-29 2009-09-01 Guo-Ren Chen Design method for the modulation of laser color level simultaneously using pulse width and pulse amplitude

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110515260A (zh) * 2018-05-21 2019-11-29 成都理想境界科技有限公司 一种激光扫描成像的方法以及激光扫描成像设备

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