CN110061421B - Semiconductor laser driving method and driving circuit - Google Patents
Semiconductor laser driving method and driving circuit Download PDFInfo
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- CN110061421B CN110061421B CN201910335533.8A CN201910335533A CN110061421B CN 110061421 B CN110061421 B CN 110061421B CN 201910335533 A CN201910335533 A CN 201910335533A CN 110061421 B CN110061421 B CN 110061421B
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Abstract
The embodiment of the invention provides a semiconductor laser driving method and a semiconductor laser driving circuit, wherein a driving signal is generated according to a driving period of a semiconductor laser, the driving signal in a high level duration time period of one driving period is composed of N pulses, N is an integer larger than 1, and the pulse widths of the N pulses are the same; wherein, N pulse peak values are equal, and at least two pulse intervals in N-1 pulse intervals formed by N pulses are not equal, or N-1 pulse intervals formed by N pulses are equal, and at least two pulse peak values in N pulses are not equal, or at least two pulse intervals in N-1 pulse intervals formed by N pulses are not equal, and at least two pulse peak values in N pulses are not equal; and outputting a driving signal to the semiconductor laser. Therefore, speckle suppression or elimination is carried out under the condition of not needing an additional speckle elimination device, and the structural complexity is further reduced.
Description
The application is based on Chinese invention application 201510452361.4 (2015-07-28), and the invention name is as follows: a semiconductor laser driving method and a divisional application of a driving circuit are provided.
Technical Field
The invention relates to the technical field of semiconductor lasers, in particular to a semiconductor laser driving method and a semiconductor laser driving circuit.
Background
The laser has the advantages of good monochromaticity, good directivity, high brightness, linear spectrum and the like, is very suitable for being used in a laser display system, is considered as a fourth generation display technology after black and white display, color display and high-definition digital display, and has the advantages of capability of realizing large color gamut display, high color saturation, high color resolution, flexible and variable display picture size, energy conservation, environmental protection and the like. Since laser light has high coherence, when laser light is used as a display light source, speckle is generated on a screen. The existence of speckle seriously affects the imaging quality of laser display, so that the contrast and resolution of an image are reduced, and the speckle becomes one of main reasons for restricting and hindering the rapid development and marketization of laser display.
In order to eliminate laser speckle, various methods for simulating speckle are proposed, such as: a moving scattering sheet is added into the light path, random phase distribution is generated through movement, speckle patterns are overlapped in the integration time of human eyes, the effect of inhibiting speckles can be achieved, and the purpose of inhibiting the speckles is achieved.
However, the method is to add a speckle dispersing device outside the laser, and the structure is complex, so that the cost is high.
Disclosure of Invention
The embodiment of the invention provides a semiconductor laser driving method and a semiconductor laser driving circuit, which are used for inhibiting or eliminating speckles without an additional speckle eliminating device, so that the structural complexity is reduced.
The embodiment of the invention provides a semiconductor laser driving method, which comprises the following steps:
generating a driving signal according to a driving cycle of the semiconductor laser, one driving cycle including a high level duration period and a low level duration period, the driving signal within the high level duration period of one driving cycle being composed of N pulses, N being an integer greater than 1; wherein, the peak values of at least two pulses in the N pulses are not equal, and/or the pulse intervals of at least two pulses in N-1 pulse intervals formed by the N pulses are not equal; and outputting the driving signal to the semiconductor laser.
Preferably, the peak values of at least two pulses of the N pulses are not equal, including: the peak values of the N pulses are decreased progressively; or the peak value of the N pulses is incremented; or the change curve of the peak values of the N pulses conforms to a Gaussian curve.
Preferably, when the peak values of at least two pulses in the N pulses are not equal, N-1 pulses formed by the N pulses have equal intervals.
Preferably, at least two pulse intervals of N-1 pulse intervals formed by the N pulses are not equal, including: the interval of N-1 pulses formed by the N pulses is decreased progressively; or the interval of N-1 pulses formed by the N pulses is increased progressively; or the variation curve of N-1 pulse intervals formed by the N pulses conforms to a Gaussian curve.
Preferably, when at least two pulse intervals of N-1 pulse intervals formed by the N pulses are not equal, the peak values of the N pulses are all equal.
Preferably, the increment is a linear increment.
Preferably, the decrease is a linear decrease.
Preferably, the semiconductor laser is a red semiconductor laser.
An embodiment of the present invention further provides a semiconductor laser driving circuit, including:
a signal generation unit for generating a drive signal according to a drive cycle of the semiconductor laser, one drive cycle including a high level duration period and a low level duration period, the drive signal within the high level duration period of one drive cycle being composed of N pulses, N being an integer greater than 1; wherein, the peak value of at least two pulses in the N pulses is not equal, and/or the pulse interval of at least two pulses in N-1 pulse intervals formed by the N pulses is not equal.
And a signal output unit for outputting the driving signal to the semiconductor laser.
Preferably, the peak values of at least two pulses of the N pulses are not equal, including: the peak values of the N pulses are decreased progressively; or the peak value of the N pulses is incremented; or the change curve of the peak values of the N pulses conforms to a Gaussian curve.
Preferably, when the peak values of at least two pulses in the N pulses are not equal, N-1 pulses formed by the N pulses have equal intervals.
Preferably, at least two pulse intervals of N-1 pulse intervals formed by the N pulses are not equal, including: the interval of N-1 pulses formed by the N pulses is decreased progressively; or the interval of N-1 pulses formed by the N pulses is increased progressively; or the variation curve of N-1 pulse intervals formed by the N pulses conforms to a Gaussian curve.
Preferably, when at least two pulse intervals of N-1 pulse intervals formed by the N pulses are not equal, the peak values of the N pulses are all equal.
Preferably, the increment is a linear increment.
Preferably, the decrease is a linear decrease.
Preferably, the semiconductor laser is a red semiconductor laser.
In the embodiment of the invention, N pulses are generated in the high level duration time period in the driving period of the semiconductor laser, and at least two peak values of at least two pulses in the N pulses are not equal, and/or at least two pulse intervals in N-1 pulse intervals formed by the N pulses are not equal, so that on one hand, the semiconductor laser can be ensured to emit laser beams in the high level duration time period of the driving period because the N pulses are generated only in the high level duration time period in the driving period, on the other hand, the wavelength range of output light of the semiconductor laser is widened by adjusting the pulse peak values and the pulse intervals because the peak values of at least two pulses in the N pulses are not equal, and/or at least two pulse intervals in the N-1 pulse intervals formed by the N pulses, the laser obtains uniformly changed temperature in the time dimension, so that uniformly distributed laser spectral lines are obtained, and finally, the frequency difference among different laser beams is enlarged, so that the coherence of a light source in a laser display system is reduced, and laser speckles are restrained. Compared with the prior art that the speckle eliminating device is added in the laser system, the embodiment of the invention does not need to add the speckle eliminating device and has the characteristics of simple system structure and low cost.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is apparent that the drawings in the following description are only embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a schematic diagram of an optical configuration of a prior art DLP projection system;
FIG. 2 is a schematic diagram of a light-emitting period T of a DLP projection system in the prior art, and waveforms of driving signals of a red semiconductor laser, a green semiconductor laser and a blue semiconductor laser;
FIG. 3 is a schematic temperature-current curve of a prior art semiconductor laser;
fig. 4 is a schematic diagram of a semiconductor laser driving process according to an embodiment of the present invention;
FIG. 5A is a waveform diagram illustrating the linear increase of the peak value of N pulses when the pulse intervals of the N pulses are equal according to an embodiment of the present invention;
FIG. 5B is a waveform diagram illustrating the linear decrease of the peak values of N pulses when the pulse intervals of the N pulses are equal according to the embodiment of the present invention;
fig. 5C is a waveform diagram of a variation curve of peak values of N pulses according to a gaussian curve when pulse intervals of the N pulses are equal according to an embodiment of the present invention;
FIG. 6A is a waveform diagram illustrating N-1 pulses formed by N pulses with linearly increasing pulse intervals when the peaks of the N pulses are equal according to an embodiment of the present invention;
FIG. 6B is a waveform diagram illustrating N-1 pulse intervals formed by N pulses decreasing linearly when the peaks of the N pulses are equal according to an embodiment of the present invention;
FIG. 6C is a waveform diagram illustrating a Gaussian curve followed by a variation curve of N-1 pulse intervals formed by N pulses when the peaks of the N pulses provided by the embodiment of the present invention are equal;
FIG. 7A is a waveform diagram illustrating the linear increment of N-1 pulse intervals formed by N pulses when the peak values of the N pulses are linearly increased according to the embodiment of the present invention;
FIG. 7B is a waveform diagram illustrating N-1 pulse intervals formed by N pulses decreasing linearly when the peak values of the N pulses decrease linearly according to an embodiment of the present invention;
fig. 8 is a schematic structural diagram of a semiconductor laser driving circuit according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described below in detail and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention provides a semiconductor laser driving scheme, which can be used for inhibiting or eliminating speckles by a driving signal of a laser without adding a speckle elimination device and has the characteristics of simple system structure and low cost.
In the embodiment of the invention, the related technical terms are as follows:
1. LD (Laser Diode, semiconductor Laser for short): the laser is a device which utilizes intrinsic energy level or doping energy level in semiconductor materials, utilizes cleavage planes of crystal lattices to form a resonant cavity, generates energy level inversion in a current injection mode, and finally generates laser through light amplification.
2. PWM (Pulse Width Modulation, Pulse Width Modulation for short): the digital output of the microprocessor is used for controlling an analog circuit, namely, a series of pulse widths are modulated to equivalently generate waveforms with different widths.
3. Laser speckle: when a coherent light source irradiates a rough object, scattered light generates interference in space, some parts of the space generate constructive interference, and some parts of the space generate destructive interference, and finally, granular light and dark spots, called speckles, appear on a screen.
4. Coherence: the coherence of laser light is generally divided into temporal coherence and spatial coherence. The time coherence refers to the magnitude of the self-coherence function between a train of waves and a self-wave delayed by a time t, and is a measure of the ability of the train of waves to interfere with themselves after being delayed for a certain time.
5. Laser display: the display technology is a technology for displaying by scanning or illuminating a display chip by using RGB (Red, Green, Blue, Red, Green, Blue) three-color laser as a light source of three primary colors.
6. Line width of spectrum: the wavelength range corresponding to the intensity falling half way down to the maximum is generally referred to as the spectral line width. The narrower the line width, the better the monochromaticity of the light source.
7. Line broadening: due to the physical property of the atomic system or the influence of the physical state of the environment, the spectral line emitted or absorbed by the atom is not a spectral line with a single frequency.
8. Red shift: the phenomenon that the wavelength of electromagnetic radiation of an object is increased due to some reason is shown in the form that spectral lines of a spectrum move a certain distance towards the red end in a visible light wave band, namely the side length of the wavelength is long, and the frequency is reduced.
9. Pulse interval: is the time interval between the last pulse and the next pulse.
Fig. 1 schematically illustrates an optical structure of a DLP (digital light processing) projection system, which is a laser display system to which an embodiment of the present invention is applied. As shown in fig. 1, the DLP projection system optical system includes: a red light semiconductor laser 101, a green light semiconductor laser 102, a blue light semiconductor laser 103, a beam expander 104, a refractor 105, a beam combining prism 106, a DMD (Digital micromirror Device) chip 107 and a projection lens 108.
As shown in fig. 1, a red semiconductor laser 101, a green semiconductor laser 102, and a blue semiconductor laser 103 form a three-primary-color laser light source of a DLP system, and in a light emitting period of the DLP projection system, when the output light intensities of the three semiconductor lasers are substantially the same, one light emitting period can be divided into three equal time periods, each semiconductor laser can output light in one time period, and no light is output in the other two time periods. Due to the high coherence of laser light, laser speckle is commonly observed in DLP projection systems that use laser light as a light source, and the presence of laser speckle affects the image, information quality, etc. of a display screen.
Fig. 2 exemplarily shows one light emitting period T of the DLP projection system, and driving signal waveforms of the red semiconductor laser, the green semiconductor laser, and the blue semiconductor laser. In a light emitting period T, the output light time lengths of the red light semiconductor laser, the green light semiconductor laser and the blue light semiconductor laser are equal. In practical application, in a light emitting period T, the output light time lengths of the red light semiconductor laser, the green light semiconductor laser, and the blue light semiconductor laser may also be unequal, which is not limited in the embodiment of the present invention.
In a light emitting period T, the red semiconductor laser, the green semiconductor laser, and the blue semiconductor laser respectively include a light emitting period and a non-light emitting period, and when a drive signal applied to the laser is high, the laser emits light, whereas the laser does not emit light. Accordingly, the drive signal waveforms of the red, green, and blue semiconductor lasers are as shown in fig. 3. Similarly, in the drive signal of the green semiconductor laser, one high level and an adjacent low level form one drive period, and in the drive signal of the blue semiconductor laser, one high level and an adjacent low level form one drive period. That is, within a drive period of one semiconductor laser, a high level duration period and a low level duration period are included.
In a light emitting period of the laser, the high level stage outputs laser light, and the low level stage outputs fluorescence or does not emit light, because the current value of the driving signal input to the laser in the high level stage is larger than the threshold current value of the laser which needs to emit light, and the current value of the driving signal input to the laser in the low level stage is smaller than the threshold current value of the laser which needs to emit light. Since the same laser has the same resistance, the higher the input voltage value of the laser is in the high level stage, the higher the current value thereof is.
Semiconductor lasers are generally pumped by current injection, and the injection of different driving currents can cause different amounts of heat to be generated when the semiconductor laser chip operates, so that the semiconductor laser chip has different temperatures. Semiconductor lasers can output light with different wavelengths at different temperatures, and the higher the temperature is, the longer the wavelength of the output light is. Meanwhile, the spectrum of the semiconductor laser also widens as the drive current increases.
Fig. 3 schematically illustrates a temperature-current curve of a semiconductor laser provided by an embodiment of the present invention. From fig. 3 it can be determined that: when the driving current is lower than the threshold value, the semiconductor laser can only emit fluorescence, and only when the driving current is greater than the threshold value current of the laser, the laser can normally work to output laser. The threshold current of the semiconductor laser is affected by temperature, and the higher the operating temperature of the semiconductor laser chip, the higher the threshold current of the semiconductor laser.
In the prior art, laser speckle is interference generated in space after a coherent light source irradiates a rough object. However, two lights having the same frequency and a constant phase difference are called coherent lights, and the light source thereof is called a coherent light source. Since the laser light generated by the laser is light with the same frequency and the same phase, the light emitted by the laser is coherent light.
The coherence of laser light is generally divided into temporal coherence and spatial coherence. The temporal coherence is mainly embodied as monochromaticity, and when the monochromaticity of the laser light source is better, the temporal coherence of the light output by the laser is better; the better the monochromaticity of the laser light source, the narrower the spectral line width of the light output by the laser; the spectral line width represents a wavelength range corresponding to the time when the intensity of the laser output light is half of the maximum value, that is, the spectral line width of the laser output light is related to the wavelength of the laser output light, and the longer the wavelength of the laser output light is, the wider the spectral line width is, and accordingly, the poorer the coherence of the laser output light is.
In this way, laser speckle in a DLP display system can be suppressed by reducing the coherence of the output light of the semiconductor laser.
Based on the above analysis, and considering that the time length of one light emitting period of the DLP projection system is several milliseconds, the response time of the semiconductor laser can reach nanosecond level, so in the embodiment of the present invention, the driving signal in the high level duration of the semiconductor laser is changed into a plurality of pulses, and by controlling the pulse peak value of the plurality of pulses in the high level duration of the semiconductor laser, or the pulse interval formed by the plurality of pulses, or the pulse peak value of the plurality of pulses and the pulse interval formed by the plurality of pulses at the same time, the wavelength of the output light of the semiconductor laser can be lengthened, and the coherence of the output light of the semiconductor laser can be further reduced.
Example one
The following describes a semiconductor laser driving procedure according to an embodiment of the present invention in detail. Fig. 4 schematically illustrates a semiconductor laser driving flow chart provided by an embodiment of the present invention. The flow can be implemented in a semiconductor laser driving circuit. Referring to fig. 4, a semiconductor laser driving process provided in an embodiment of the present invention includes the following steps:
step 401, generating a driving signal according to a driving cycle of the semiconductor laser, where one driving cycle includes a high level duration and a low level duration, and the driving signal in the high level duration of one driving cycle is composed of N pulses, where N is an integer greater than 1; wherein, the peak value of at least two pulses in the N pulses is not equal, and/or the pulse interval of at least two pulses in N-1 pulse intervals formed by the N pulses is not equal.
In practical applications, the waveforms with different widths can be equivalently generated by adjusting the N pulses in the high level duration of one driving period of the semiconductor laser through PWM. In the embodiment of the present invention, the pulse widths of the N pulses in the high level duration of one driving cycle may be all the same or may be partially the same. In the embodiment of the present invention, the pulse widths of the N pulses in the high level duration of one driving cycle are not specifically limited.
In a DLP projection system, there are three semiconductor lasers: red, green and blue semiconductor lasers. In the embodiment of the present invention, for the DLP projection system, the driving signals of all three semiconductor lasers may be generated as described above, or the driving signals of any two semiconductor lasers in all three semiconductor lasers may be generated as described above, or the driving signal of any one laser may be generated as described above, and accordingly, the "semiconductor laser" in the above process may be one of a red semiconductor laser, a green semiconductor laser, and a blue semiconductor laser.
Preferably, in the embodiment of the present invention, the semiconductor laser may be a red semiconductor laser. This is because the threshold current of the semiconductor laser is affected by temperature, and the temperature characteristic of the red semiconductor laser is most remarkable, and it is easier to change the wavelength range by controlling the change in temperature. Therefore, reducing the coherence of the output light of the red semiconductor laser is easier to achieve than reducing the coherence of the output light of the green semiconductor laser and the blue semiconductor laser.
In the embodiment of the invention, N pulses are generated in the high level duration time period in the driving period of the semiconductor laser, and at least two peak values of at least two pulses in the N pulses are not equal, and/or at least two pulse intervals in N-1 pulse intervals formed by the N pulses are not equal, so that on one hand, the semiconductor laser can be ensured to emit laser beams in the high level duration time period of the driving period because the N pulses are only generated in the high level duration time period in the driving period, on the other hand, the wavelength of output light of the semiconductor laser is changed and the wavelength range of the output light of the semiconductor laser is widened because at least two peak values of the N pulses are not equal, and/or at least two pulse intervals in the N-1 pulse intervals formed by the N pulses are not equal, the laser obtains uniformly changed temperature in the time dimension, so that uniformly distributed laser spectral lines are obtained, the frequency difference among different laser beams is finally enlarged, the coherence of a light source in a laser display system is reduced, and laser speckles are further inhibited.
Example two
The implementation process of the second embodiment is substantially the same as that of the first embodiment, and in particular, when the peak values of at least two pulses of the N pulses generated in step 401 are not equal, the N-1 pulse intervals formed by the N pulses may all be equal.
In the second embodiment, as long as it is ensured that the peak values of at least two pulses of the N pulses in the high level duration of one driving cycle are not equal, the operating temperature of the semiconductor laser chip can be changed in general. In order to effectively control the operating temperature of the semiconductor laser chip and increase the wavelength of the output light of the semiconductor laser, in a preferred embodiment of the present invention, the variation rule of the pulse peak values of N pulses in the high level duration of one driving cycle of the semiconductor laser may include any one of the following rules a1 to a rule a 3.
Rule a1, the peak values of N pulses within the high level duration period of one drive cycle of the semiconductor laser are incremented.
Further, the peak values of the N pulses in the high level duration of the semiconductor laser may be linearly increased or may be non-linearly increased, for example, according to an increasing portion of a gaussian curve.
Rule a2, the peak values of N pulses within the high level duration of one drive cycle of the semiconductor laser are decremented.
Further, the peak values of the N pulses in the high level duration of the semiconductor laser may decrease linearly or may increase non-linearly, for example, according to a decreasing portion of a gaussian curve.
Rule a3, a change curve of peak values of N pulses in a high level duration period of one driving cycle of a semiconductor laser follows a gaussian curve.
Further, in the embodiment of the present invention, the variation rule of the peak values of the N pulses in the high level duration of one driving period of the semiconductor laser is not specifically limited.
Specifically, the peak values of the N pulses conform to the above a1 rule and all pulse intervals are equal, that is, the peak values of the N pulses in the high level duration of the semiconductor laser linearly increase, and N-1 pulse intervals formed by the N pulses are equal. Fig. 5A is a waveform diagram illustrating a linear increase in the peak value of N pulses when the pulse intervals for providing N pulses are equal in an embodiment of the present invention.
Because the peak values of N pulses in the high level duration of the semiconductor laser are linearly increased in an increasing manner, and N-1 pulse intervals formed by the N pulses are equal, it can be determined that the heat generated by each pulse interval of the semiconductor laser chip in the high level duration will be different, and accordingly, the operating temperature of the semiconductor laser chip will be different; the semiconductor laser can output light with different wavelengths at different working temperatures, and the wavelength of the output light is longer as the working temperature is higher; in the prior art, the wavelength of the semiconductor laser is red-shifted with the increase of temperature, so that the width and the distribution of spectral lines of the semiconductor laser output are changed.
It can be determined that the pulse intervals of N pulses within the high level duration of the semiconductor laser are equal, and when the peak values of the N pulses linearly increase, the wavelength of the output light of the semiconductor laser can be changed, and within the high level duration of the semiconductor laser, the wavelength range of the output light of the semiconductor laser is widened, the spectral width of the semiconductor laser is widened, the frequency difference between different laser beams is enlarged, and thus the coherence of the output light of the semiconductor laser is reduced.
Further, when the pulse intervals of the N pulses in the high level duration of the semiconductor laser are equal and the peak values of the N pulses in the high level duration of the semiconductor laser increase nonlinearly, such as by increasing in accordance with an increasing portion of a gaussian curve, the coherence of the output light of the semiconductor laser can be reduced as well.
Specifically, the peak values of the N pulses conform to the above a2 rule and all pulse intervals are equal, that is, when the peak values of the N pulses in the high level duration of the semiconductor laser linearly decrease, N-1 pulse intervals formed by the N pulses are equal. Fig. 5B is a waveform diagram illustrating that the peak values of N pulses linearly decrease when the pulse intervals of the N pulses provided in the embodiment of the present invention are equal.
Because the peak values of N pulses in the high level duration of the semiconductor laser are linearly decreased progressively and the N-1 pulse intervals formed by the N pulses are equal, the heat generated by the semiconductor laser chip in each pulse interval in the high level duration can be determined to be different, and correspondingly, the working temperature of the semiconductor laser chip is different; since the semiconductor laser can output light with different wavelengths at different operating temperatures, the wavelength of the output light is longer as the operating temperature is higher.
It can be determined that the pulse intervals of N pulses within the high level duration of the semiconductor laser are equal, and the peak values of the N pulses decrease linearly, the wavelength of the output light of the semiconductor laser can be changed, and within the high level duration of the semiconductor laser, the wavelength range of the output light of the semiconductor laser is widened, the spectral width of the semiconductor laser is widened, the frequency difference between different laser beams is enlarged, and thus the coherence of the output light of the semiconductor laser is reduced.
Further, when the pulse intervals of the N pulses in the high level duration of the semiconductor laser are equal, and the peak values of the N pulses in the high level duration of the semiconductor laser increase nonlinearly, for example, decrease in accordance with a decreasing portion of a gaussian curve, the coherence of the output light of the semiconductor laser may be reduced as well.
Specifically, the peak values of the N pulses conform to the above a3 rule and all pulse intervals are equal, that is, when the variation curve of the peak values of the N pulses within the high level duration of the semiconductor laser conforms to a gaussian curve, and N-1 pulse intervals formed by the N pulses are equal. Fig. 5C is a waveform diagram illustrating that the variation curve of the peak values of N pulses conforms to a gaussian curve when the pulse intervals of the N pulses provided in the embodiment of the present invention are equal.
Because the variation curve of the peak value of the pulse in the high level duration time of the semiconductor laser accords with the Gaussian curve, and N-1 pulse intervals formed by N pulses are equal and the same, the heat generated by each pulse interval of the semiconductor laser chip in the high level duration time can be determined to be different, and correspondingly, the working temperature of the semiconductor laser chip is different; since the semiconductor laser can output light with different wavelengths at different operating temperatures, the wavelength of the output light is longer as the operating temperature is higher.
It can be determined that the pulse intervals of the N pulses within the high level duration of the semiconductor laser are equal, and the variation curve of the peak line of the N pulses conforms to a gaussian curve, the wavelength of the output light of the semiconductor laser can be changed, and within the high level duration of the semiconductor laser, the wavelength range of the output light of the semiconductor laser is widened, the spectral width of the semiconductor laser is broadened, the frequency difference between different laser beams is enlarged, and thus the coherence of the output light of the semiconductor laser is reduced.
Further, in the embodiment of the present invention, when the pulse intervals of the N pulses within the high level duration period of the semiconductor laser are equal, the rule of variation of the peak values of the N pulses within the high level duration period of the semiconductor laser is not particularly limited as long as the coherence of the output light of the semiconductor laser can be reduced.
In the embodiment of the invention, the driving signal which is generated in the high level continuous time period of the semiconductor laser and consists of N pulses is output to the semiconductor laser. Since the peak values of at least two pulses in the N pulses in the high level duration time period are not equal, the operating temperature of the semiconductor laser chip can be controlled by changing the peak values of the pulses in the high level duration time period, so that the wavelength of the output light of the semiconductor laser is changed. In the laser display system, the wavelength of the output light of the laser semiconductor is changed, the wavelength range of the output light of the semiconductor laser is widened, and the laser obtains uniformly-changed temperature in the time dimension, so that uniformly-distributed laser spectral lines are obtained, the spectral width of the semiconductor laser is widened as much as possible, the frequency difference among different laser beams is enlarged, the coherence of the output light of the semiconductor laser is reduced, and laser speckles are restrained. Compared with the prior art that a speckle eliminating device is added in a laser system, the embodiment of the invention has the characteristics of simple system structure and low system cost.
EXAMPLE III
The implementation process of the third embodiment is substantially the same as that of the first embodiment, and in particular, when the N-1 pulse intervals formed by the N pulses generated in step 401 are not equal, the N pulse peaks may be equal.
In the third embodiment, when at least two pulse intervals of N-1 pulse intervals of N pulse formations within a high level duration period of one driving cycle of the semiconductor laser are not equal, a variation rule of the N-1 pulse intervals of the N pulse formations may include any one of the following rules b1 to b 3:
rule b1, N-1 pulse intervals of N pulse formations within a high level duration of one drive cycle of the semiconductor laser are incremented.
Further, the N-1 pulse intervals formed by the N pulses in the high level duration of the semiconductor laser may be linearly increasing or may be non-linearly increasing, for example, may be increased according to an increasing portion of a gaussian curve.
Rule b2, N-1 pulse intervals of N pulse formations within a high level duration of one drive cycle of the semiconductor laser are decremented.
Further, the N-1 pulse intervals formed by the N pulses in the high level duration of the semiconductor laser may be linearly decreasing or may be non-linearly increasing, for example, decreasing according to a decreasing portion of a gaussian curve.
Rule b3, the variation curve of N-1 pulse intervals formed by N pulses in the high level duration of one drive cycle of the semiconductor laser follows a gaussian curve.
Further, in the embodiment of the present invention, the variation rule of the N-1 pulse intervals formed by the N pulses in the high level duration of one driving cycle of the semiconductor laser is not particularly limited.
Specifically, the pulse intervals formed by the N pulses conform to the b1 rule described above and all the pulse peaks are equal, that is, when the pulse intervals formed by the N pulses within the high level duration of the semiconductor laser linearly increase, the peaks of the N pulses are equal. Fig. 6A is a waveform diagram illustrating that N-1 pulse intervals formed by N pulses are linearly increased when the peaks of the N pulses provided by the embodiment of the present invention are equal.
Because N-1 pulse intervals formed by N pulses in the high level duration of the semiconductor laser are linearly increased in number and the peak values of the N pulses are equal, it can be determined that the heat generated by each pulse interval of the semiconductor laser chip in the high level duration will be different, and the working temperatures of the corresponding semiconductor laser chips have differences; since the semiconductor laser can output light with different wavelengths at different operating temperatures, the wavelength of the output light is longer as the operating temperature is higher.
It can be determined that N-1 pulse intervals formed by N pulses within the high level duration of the semiconductor laser linearly increase, and peaks of the N pulses are equal, the wavelength of the output light of the semiconductor laser can be changed, and within the high level duration of the semiconductor laser, the wavelength range of the output light of the semiconductor laser is widened, the spectral width of the semiconductor laser is widened, the frequency difference between different laser beams is enlarged, and thus the coherence of the output light of the semiconductor laser is reduced.
Further, when the peak values of N pulses in the high level duration of one driving cycle of the semiconductor laser are equal, and the interval between N-1 pulses formed by the N pulses in the high level duration of the semiconductor laser increases non-linearly, for example, the pulse may increase according to the increasing portion of the gaussian curve, the coherence of the output light of the semiconductor laser may also be reduced.
Specifically, the pulse intervals formed by the N pulses conform to the b2 rule described above and all the pulse peaks are equal, that is, when the pulse intervals formed by the N pulses in the high level duration of the semiconductor laser linearly decrease, the peak values of the N pulses are equal. Fig. 6B is a waveform diagram illustrating that N-1 pulse intervals formed by N pulses are linearly decreased when the peak values of the N pulses provided by the embodiment of the present invention are equal.
Because N-1 pulse intervals formed by N pulses in the high level duration of the semiconductor laser are linearly decreased, and the peak values of the N pulses are equal, the heat generated by each pulse interval of the semiconductor laser chip in the high level duration can be determined to be different, and the working temperatures of the corresponding semiconductor laser chips are different; the semiconductor laser can output light with different wavelengths at different working temperatures, and the wavelength of the output light is longer as the working temperature is higher; in the prior art, the wavelength of the semiconductor laser is red-shifted with the increase of temperature, so that the width and the distribution of spectral lines of the semiconductor laser output are changed.
It can be determined that N-1 pulse intervals formed by N pulses within the high level duration of the semiconductor laser decrease linearly, and peaks of the N pulses are equal, the wavelength of the output light of the semiconductor laser can be changed, and within the high level duration of the semiconductor laser, the wavelength range of the output light of the semiconductor laser is widened, the spectral width of the semiconductor laser is widened, the frequency difference between different laser beams is enlarged, and the coherence of the output light of the semiconductor laser is reduced.
Further, when the peak values of N pulses in the high level duration of one driving period of the semiconductor laser are equal, and the interval between N-1 pulses formed by the N pulses in the high level duration of the semiconductor laser increases non-linearly, for example, decreases according to the decreasing portion of the gaussian curve, the coherence of the output light of the semiconductor laser can be reduced.
Specifically, the pulse intervals formed by the N pulses conform to the b3 rule and all pulse peaks are equal, that is, when the variation curve of the pulse intervals formed by the N pulses in the high level duration of the semiconductor laser conforms to the gaussian curve, the peaks of the N pulses are equal. Fig. 6C is a waveform diagram illustrating that the variation curve of N-1 pulse intervals formed by N pulses conforms to a gaussian curve when the peak values of the N pulses provided by the embodiment of the present invention are equal.
Because the variation curve of N-1 pulse intervals formed by N pulses in the high level duration time of the semiconductor laser is linear according to a Gaussian curve and the peak values of the N pulses are equal, the heat generated by each pulse interval of the semiconductor laser chip in the high level duration time can be determined to be different, and the working temperature of the corresponding semiconductor laser chip is different; since the semiconductor laser can output light with different wavelengths at different operating temperatures, the wavelength of the output light is longer as the operating temperature is higher.
It can be determined that N-1 pulse intervals formed by N pulses in the high level duration of the semiconductor laser are linearly decreased, and peaks of the N pulses are equal, the wavelength of the output light of the semiconductor laser can be changed, and in the high level duration of the semiconductor laser, the wavelength range of the output light of the semiconductor laser is widened, the spectral width of the semiconductor laser is widened, the frequency difference between different laser beams is enlarged, so that the coherence of the output light of the semiconductor laser is reduced, and the coherence of the output light of the semiconductor laser is reduced.
In the embodiment of the invention, the driving signal which is generated in the high level continuous time period of the semiconductor laser and consists of N pulses is output to the semiconductor laser. Since at least two pulse intervals of N-1 pulse intervals formed by N pulses in the high level duration time period are not equal, the working temperature of the semiconductor laser chip can be controlled by changing the pulse intervals in the high level duration time period, so that the wavelength of the output light of the semiconductor laser is changed. In the laser display system, the wavelength of the output light of the laser semiconductor is changed, the wavelength range of the output light of the semiconductor laser is widened, and the laser obtains uniformly-changed temperature in the time dimension, so that uniformly-distributed laser spectral lines are obtained, the spectral width of the semiconductor laser is widened as much as possible, the frequency difference among different laser beams is enlarged, the coherence of the output light of the semiconductor laser is reduced, and laser speckles are restrained. Compared with the prior art that a speckle eliminating device is added in a laser system, the embodiment of the invention has the characteristics of simple system structure and low system cost.
Example four
The implementation process of the fourth embodiment is substantially the same as that of the first embodiment, and in particular, when the peak values of at least two pulses of the N pulses formed in step 401 are not equal, at least two pulse intervals of N-1 pulse intervals formed by the N pulses may also be not equal.
In the fourth embodiment, the variation rule of the pulse peak values of the N pulses in the high level duration period of one driving cycle of the semiconductor laser may include any one of the rules a1 to a3 in the second embodiment; when at least two pulse intervals of N-1 pulse intervals of N pulse formations within a high level duration of one driving period of the semiconductor laser are not equal, the rule of variation of N-1 pulse intervals of N pulse formations may include any one of rules b1 to b3 in embodiment three.
Specifically, the peak values of the N pulses conform to the above-mentioned a1 rule and the pulse interval lines formed by the N pulses conform to the above-mentioned b1 rule, that is, the peak values of the N pulses in the high level duration of the semiconductor laser linearly increase and the N-1 pulse intervals formed by the N pulses linearly increase. Fig. 7A is a waveform diagram illustrating N-1 pulse intervals formed by N pulses in a linear increment when N pulses are provided in an embodiment of the present invention with linearly increasing peak values.
Since the peak values of the N pulses in the high level duration of the semiconductor laser are linearly increased and the N-1 pulse intervals formed by the N pulses are also linearly increased, it can be determined that the amount of heat generated by the semiconductor laser chip in each pulse interval in the high level duration will be different, but since the semiconductor laser is linearly increased in each pulse interval in the high level duration, the amount of heat generated by the semiconductor laser chip in the high level duration will tend to be equal. Because the laser spectrum and the temperature are strictly and positively correlated, when the temperature is uniformly distributed, the spectrum output by the semiconductor laser is also uniformly distributed.
It can be determined that the peak values of N pulses within the high level duration of the semiconductor laser are linearly increased and the N-1 pulse intervals formed by the N pulses are also linearly increased, so that the wavelength range of the output light of the semiconductor laser is widened, the spectral width of the semiconductor laser is widened, the frequency difference between different laser beams is enlarged, and the coherence of the output light of the semiconductor laser is reduced.
Further, when the peak values of the N pulses in the high level duration of the semiconductor laser are increased according to the increasing part of the gaussian curve, and the N-1 pulses formed by the N pulses are increased in a non-linear manner at intervals, such as being increased according to the increasing part of the gaussian curve, the coherence of the output light of the semiconductor laser can be reduced.
Specifically, the peak values of the N pulses conform to the rule a2 and the pulse interval lines formed by the N pulses conform to the rule b2, i.e., the peak values of the N pulses in the high level duration of the semiconductor laser linearly decrease and the N-1 pulse intervals formed by the N pulses linearly decrease. Fig. 7B is a waveform diagram illustrating that the N-1 pulse intervals formed by the N pulses are linearly decreased when the peak values of the N pulses are linearly decreased in the embodiment of the present invention.
Since the peak values of the N pulses in the high level duration of the semiconductor laser linearly decrease and the N-1 pulse intervals formed by the N pulses also linearly decrease, it can be determined that the amount of heat generated by the semiconductor laser chip in each pulse interval in the high level duration will be different, and since the pulse intervals of the semiconductor laser chip in the high level duration are linearly decreased, the amount of heat generated by the semiconductor laser chip in the high level duration will tend to be equal. Because the laser spectrum and the temperature are strictly and positively correlated, when the temperature is uniformly distributed, the spectrum output by the semiconductor laser is also uniformly distributed.
It can be determined that the peak values of N pulses within the high level duration of the semiconductor laser decrease linearly, and the N-1 pulse intervals formed by the N pulses also increase linearly, so that the wavelength range of the output light of the semiconductor laser is widened, the spectral width of the semiconductor laser is widened, the frequency difference between different laser beams is enlarged, and the coherence of the output light of the semiconductor laser is reduced.
Further, when the peak values of the N pulses in the high level duration of the semiconductor laser decrease according to the decreasing portion of the gaussian curve, and the N-1 pulse intervals formed by the N pulses increase nonlinearly, such as decrease according to the decreasing portion of the gaussian curve, the coherence of the output light of the semiconductor laser can be reduced.
In the embodiment of the invention, the driving signal which is generated in the high level continuous time period of the semiconductor laser and consists of N pulses is output to the semiconductor laser. The peak values of at least two pulses in the N pulses in the high level duration time period and at least two pulse intervals in N-1 pulse intervals formed by the N pulses are different. Therefore, by simultaneously changing the pulse peak value and the pulse interval in the high level duration period, the operating temperature of the semiconductor laser chip can be controlled, thereby changing the wavelength of the output light of the semiconductor laser. In the laser display system, the wavelength of the output light of the laser semiconductor is changed, the wavelength range of the output light of the semiconductor laser is widened, and the laser obtains uniformly-changed temperature in the time dimension, so that uniformly-distributed laser spectral lines are obtained, the spectral width of the semiconductor laser is widened as much as possible, the frequency difference among different laser beams is enlarged, the coherence of the output light of the semiconductor laser is reduced, and laser speckles are restrained. Compared with the prior art that a speckle eliminating device is added in a laser system, the embodiment of the invention has the characteristics of simple system structure and low system cost.
EXAMPLE five
Based on the same concept, the fifth embodiment provides a semiconductor laser driving circuit. Fig. 8 schematically illustrates a semiconductor laser driving circuit provided in an embodiment of the present application, which includes a signal generating unit 81 and a signal output unit 82.
A signal generating unit 81 for generating a driving signal according to a driving cycle of the semiconductor laser, one driving cycle including a high level duration period and a low level duration period, the driving signal in the high level duration period of one driving cycle being composed of N pulses, N being an integer greater than 1; wherein, the peak value of at least two pulses in the N pulses is not equal, and/or the pulse interval of at least two pulses in N-1 pulse intervals formed by the N pulses is not equal.
A signal output unit 82 for outputting the driving signal to the semiconductor laser.
Preferably, the peak values of at least two pulses of the N pulses are not equal, including:
the peak values of the N pulses are decreased progressively; or
The peak values of the N pulses are incremented; or
And the change curve of the peak values of the N pulses conforms to a Gaussian curve.
Preferably, when the peak values of at least two pulses in the N pulses are not equal, N-1 pulses formed by the N pulses have equal intervals.
Preferably, at least two pulse intervals of N-1 pulse intervals formed by the N pulses are not equal, including:
the interval of N-1 pulses formed by the N pulses is decreased progressively; or
The interval of N-1 pulses formed by the N pulses is increased progressively; or
The variation curve of N-1 pulse intervals formed by the N pulses conforms to a Gaussian curve.
Preferably, when at least two pulse intervals of N-1 pulse intervals formed by the N pulses are not equal, the peak values of the N pulses are all equal.
Preferably, the increment is a linear increment.
Preferably, the decrease is a linear decrease.
Preferably, the semiconductor laser is a red semiconductor laser.
The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While the preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all alterations and modifications as fall within the scope of the application.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.
Claims (11)
1. A semiconductor laser driving method, comprising:
generating a driving signal according to a driving cycle of the semiconductor laser, wherein one driving cycle comprises a high level duration time period and an adjacent low level duration time period, the driving signal in the high level duration time period of one driving cycle is composed of N pulses, N is an integer greater than 1, and the pulse widths of the N pulses are the same;
the N pulse peak values are equal, and at least two pulse intervals in N-1 pulse intervals formed by the N pulses are not equal;
or the N-1 pulse intervals formed by the N pulses are equal, and the peak values of at least two pulses in the N pulses are not equal;
or at least two pulse intervals in N-1 pulse intervals formed by the N pulses are not equal and the peak values of at least two pulses in the N pulses are not equal,
and outputting the driving signal to the semiconductor laser.
2. The driving method according to claim 1,
the semiconductor laser is a red semiconductor laser, a green semiconductor laser or a blue semiconductor laser.
3. The driving method according to claim 1,
at least two pulse intervals in N-1 pulse intervals formed by the N pulses are unequal, and the method comprises the following steps:
the interval of N-1 pulses formed by the N pulses is decreased progressively; or
The interval of N-1 pulses formed by the N pulses is increased progressively; or
The variation curve of N-1 pulse intervals formed by the N pulses conforms to a Gaussian curve.
4. The driving method according to claim 1,
the peak values of at least two pulses in the N pulses are unequal, and the method comprises the following steps:
the peak values of the N pulses are decreased progressively; or
The peak values of the N pulses are incremented; or
And the change curve of the peak values of the N pulses conforms to a Gaussian curve.
5. The driving method as claimed in any one of claims 1 to 4, wherein N pulses in a high level duration of one driving period are adjusted by PWM.
6. The driving method according to any one of claims 1 to 4, wherein a high level duration of one driving period is a light emission phase of the semiconductor laser.
7. A semiconductor laser driving circuit, comprising:
the semiconductor laser driving circuit comprises a signal generating unit, a driving unit and a control unit, wherein the signal generating unit is used for generating driving signals according to driving cycles of the semiconductor laser, one driving cycle comprises a high level duration time section and an adjacent low level duration time section, the driving signals in the high level duration time section of one driving cycle are formed by N pulses, N is an integer larger than 1, and the pulse widths of the N pulses are the same;
the N pulse peak values are equal, and at least two pulse intervals in N-1 pulse intervals formed by the N pulses are not equal;
or the N-1 pulse intervals formed by the N pulses are equal, and the peak values of at least two pulses in the N pulses are not equal;
or at least two pulse intervals in N-1 pulse intervals formed by the N pulses are not equal, and the peak values of at least two pulses in the N pulses are not equal;
and a signal output unit for outputting the driving signal to the semiconductor laser.
8. The drive circuit according to claim 7, wherein the semiconductor laser is a red semiconductor laser or a green semiconductor laser or a blue semiconductor laser.
9. The drive circuit of claim 7,
at least two pulse intervals in N-1 pulse intervals formed by the N pulses are unequal, and the method comprises the following steps:
the interval of N-1 pulses formed by the N pulses is decreased progressively; or
The interval of N-1 pulses formed by the N pulses is increased progressively; or
The variation curve of N-1 pulse intervals formed by the N pulses conforms to a Gaussian curve.
10. The driving circuit of claim 7, wherein at least two of the N pulses have unequal peak values, comprising:
the peak values of the N pulses are decreased progressively; or
The peak values of the N pulses are incremented; or
And the change curve of the peak values of the N pulses conforms to a Gaussian curve.
11. A drive circuit as claimed in any one of claims 7 to 10, characterized in that the N pulses within the high duration of one drive period are adjusted by PWM.
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| CN109462135A (en) * | 2018-12-26 | 2019-03-12 | 昂纳信息技术（深圳）有限公司 | A kind of the amplification output method and system of optical signal |
| CN112234431A (en) * | 2020-08-31 | 2021-01-15 | 深圳博升光电科技有限公司 | Method and unit for driving laser device |
| CN116539559A (en) * | 2023-07-05 | 2023-08-04 | 安徽至慧仪器科技有限公司 | Laser gas leakage sensor based on scattering medium |
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| CN106410602B (en) | 2019-07-05 |
| CN110007551A (en) | 2019-07-12 |
| CN106410602A (en) | 2017-02-15 |
| CN110007551B (en) | 2021-05-18 |
| CN110061421A (en) | 2019-07-26 |
| CN110112647B (en) | 2021-05-18 |
| CN110112647A (en) | 2019-08-09 |
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