Laser projector

A laser projector steers a pulsed laser beam to form a pattern of stationary dots on an object, the pulsed laser beam having a periodicity determined based at least in part on a maximum allowable spacing of the dots and on a maximum angular velocity at which the beam can be steered, wherein a pulse width of the laser beam and a pulse peak power of the laser beam are based at least in part on the determined periodicity and on laser safety requirements.

BACKGROUND

The subject matter disclosed herein relates to a light projection system, often referred to as a “laser projector,” and especially to a light projection system that projects a glowing light pattern onto an object without requiring retroreflective or cooperative targets.

Light projection devices are used in a variety of applications to project images onto objects. In some applications, an illuminated three-dimensional (3D) pattern, also referred to as a “template,” is projected onto an object. The template may be formed, for example, by projecting a rapidly moving, vector-scan, light beam onto the object. In some systems, the projected light beam is a laser beam. The light beam strikes the surface of the object following a predetermined trajectory in a repetitive manner. When repetitively moved at a sufficiently high beam speed and refresh rate, the trace of the projected beam on the object appears to the human eye as a continuous glowing line. The projected pattern of light appears as the glowing template that can be used to assist in the positioning of parts, components and work pieces.

Currently, light projection systems are mainly used within production facilities. Light projection systems potentially useful outside production facilities, for example, in construction sites to assist in constructing of buildings or other objects. However, until now, limitations have made the use of light projection devices impractical in such applications. Examples of such limitations include (1) power limitations that make battery operation largely impractical, (2) cumbersome sharing of information with computers and accessory instruments, (3) relatively large instrument size, and (4) dynamic range limitations making many types of measurements impractical. In addition, a problem seen within production facilities and outdoors at construction sites is poor visibility of projected laser beams in certain circumstances, particularly when distances being measured are large, when flicker cannot be tolerated, and when laser safety standards are desired be observed.

Accordingly, while light projection systems and methods are suitable for their intended purposes, the need for improvement remains, particularly in enabling power efficient battery operation, methods of easily sharing data with computers and instruments, reducing instrument size, increasing measurement dynamic range, and maintaining high visibility of projected light.

BRIEF DESCRIPTION

According to an embodiment, a method is provided. The method includes: steering a pulsed laser beam to form a pattern of stationary dots on an object, the pulsed laser beam having a periodicity determined based at least in part on a maximum allowable spacing of the dots and on a maximum angular velocity at which the beam can be steered, wherein a pulse width of the laser beam and a pulse peak power of the laser beam are based at least in part on the determined periodicity and on laser safety requirements; and storing the periodicity.

In addition to one or more of the features described herein, or as an alternative, further embodiments of the method may include steering a continuous-wave (cw) laser beam to form a pattern on the object, the power of the emitted laser beam based at least in part on the laser safety requirements. In addition to one or more of the features described herein, or as an alternative, further embodiments of the method may include shutting off projection of laser light in response to detecting with an optical detector a condition indicating that the emitted laser pulse energy has exceeded a laser safety limit. In addition to one or more of the features described herein, or as an alternative, further embodiments of the method may include shutting off projection of laser light in response to detecting with an optical detector a condition indicating that the emitted average laser power has exceeded a laser safety limit.

In addition to one or more of the features described herein, or as an alternative, further embodiments of the method may include placing a reflective target to intercept one of the dots; and detecting a change in reflected light and, in response, switching the laser from pulsed mode to continuous-wave (cw) mode. In addition to one or more of the features described herein, or as an alternative, further embodiments of the method may include detecting a second pattern of laser light reflected from the reflective target when the laser is in cw mode and, in response, taking an action based on the detected second pattern.

According to another embodiment a device is provided. The device includes: a laser operable to produce a pulsed laser beam; a beam-steering system operable to steer the pulsed laser beam onto an object; and one or more processors operable to control the laser and the beam-steering system to form the pulsed laser beam into a pattern of stationary dots on the object, the pulsed laser beam having a periodicity determined based at least in part on a maximum allowable spacing of the dots and on a maximum angular velocity at which the beam can be steered, the pulsed laser beam having a pulse width and a pulse peak power of the laser beam determined based at least in part on the determined periodicity and on laser safety requirements.

In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include the laser being further operable to produce a continuous-wave (cw) laser beam having an emitted power, the emitted power based at least in part on the laser safety requirements; and the beam-steering system is further operable to steer the cw laser beam onto the object to form a pattern on the object. In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include the one or more processors are further operable to shut off the projection of laser light in response to detecting with an optical detector a condition indicating that the emitted laser pulse energy has exceeded a laser safety limit. In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include the one or more processors are further operable to shut off the projection of laser light in response to detecting with an optical detector a condition indicating that the emitted average laser power has exceeded a laser safety limit. In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include the action including steering the pulsed laser beam to form a third pattern of stationary dots on the object, the third pattern covering a smaller area than the first pattern.

In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include a reflective target; and an optical detector operable to detect reflected laser light. In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include the laser being further operable to produce a continuous-wave (cw) laser beam; the beam-steering system is further operable to steer the cw laser beam onto the object to form a pattern on the object; and the one or more processors are further operable to determine that laser light detected by the detector has been reflected by the reflective target and, in response, causing the laser to emit the cw laser beam and further causing the beam-steering system to steer the emitted cw laser beam into a segment of light on the reflective target.

In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include the one or more processors are further operable to determine that the cw laser beam, when reflected from the reflective target and detected by the optical detector, has a second pattern, the processor taking a further action based on the determined second pattern. In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include the further action including steering the pulsed laser beam to form a third pattern of stationary dots on the object, the third pattern covering a smaller area than the first pattern.

DETAILED DESCRIPTION

Embodiments of the present disclosure provide improved power efficiency, built-in batteries, wireless communication, reduced instrument size, improved dynamic range, and higher visibility of projected patterns without flicker.

FIGS.1A,1Bare front isometric and rear isometric views of a light projector10according to an embodiment. In an embodiment, the light projector10includes a front cover assembly20, a base assembly30, a power assembly40, and a fan assembly50. The power assembly40further includes a latch42that opens and closes a door44. In an embodiment, elastomeric bumpers22are attached to each of the four corners of the front cover assembly20and light pipes24are attached on each side of each bumper. The light pipes are illuminated by light emitting diodes (LEDs) in status LED PCBAs340(FIG.3).

FIG.2is an isometric view of the light projector with the fan assembly removed. A rear assembly60is sandwiched between the base assembly30and the power assembly40. The base assembly30and the rear assembly60include grooved heat sinks35as outer elements.

FIG.3is an exploded isometric view of the front cover assembly20. In an embodiment, the front cover assembly20includes a front panel subassembly310, status LED printed circuit board assemblies (PCBAs)340, and camera subassembly360. The front panel subassembly310includes a front panel form312, an information plate314, a front window316, a window gasket318, a camera illuminator gasket320, and a camera window322. The front cover assembly20includes four of the status LED PCBAs340, one of the PCBAs40behind each corner of the front panel form312. In an embodiment, the camera subassembly360includes a camera lens362, a camera lens mount364, a camera PCBA366, and an infrared (IR) LED PCBA370. The camera PCBA366includes a photosensitive array, and the IR LED PCBA370, which includes LEDs372.

FIGS.4A,4Bshow two isometric views of the rear assembly60. The rear assembly60includes a rear panel410, a power distribution PCBA420, a ribbon cable422, an environmental recorder430, and an internal battery440. The ribbon cable, which has first header423and second header424, receives electrical power from and exchanges communication signals with the power assembly40. The rear panel410serves as a grooved heat sink.

FIG.5is a partially exploded isometric view of the power assembly40that includes the door44opened to reveal two battery units510,512and a circuit board compartment520. In an embodiment, the batteries510,512may be removed or inserted without turning off power to the light projector10. The power assembly further includes an on-off switch530, a connector for optional input power522, and an Ethernet connector524.

FIGS.6A,6Bare top isometric and bottom isometric views, respectively, of a fan assembly50. From the top isometric view,FIG.6Ashows the fan plenum610, which is the part of the fan assembly that circulates air to components of the light projector10. The fan assembly further includes two cooling fans620,622and a cooling fan mount624.

FIG.7is a front view of the base assembly30. In this view, some components are shown in cross section, including the base housing702, the fan assembly, and optical components such as lenses, beam splitters, and detectors. A laser710launches polarized light into a polarization maintaining (PM) optical fiber712, which terminates in a fiber-optic connector714that includes a ferrule716. Light is launched from the ferrule716through a first lens assembly720and a second lens assembly725. A focusing mechanism730adjusts the position of the second lens assembly725to focus the beam of light to a small spot on an object some distance away from the light projector10. The light from the second lens assembly725proceeds to a folding beam splitter740. A small amount of the light passes to an optical detector742that measures the optical power of the launched laser beam for monitoring purposes. The rest of the laser light reflects off the folding beam splitter740and travels to the polarizing beam splitter745.

In an embodiment, the ferrule716is clocked to align the linear polarization of the laser light to the direction of maximum reflection of the polarizing beam splitter745. The light reflected off the polarizing beam splitter745passes through a quarter wave plate750oriented to convert the reflected linearly polarized light into circularly polarized light. The circularly polarized light reflects off a first mirror755driven by a galvanometer (galvo) motor assembly757that further includes a transducer such as an angular encoder (not shown) for measuring the angle of rotation of the first mirror755. The light reflected off the first mirror755passes to a second mirror760that sends the light out of the window316. The second mirror760is driven by the galvo motor assembly762that further includes an angular transducer (not shown) for measuring the angle of rotation of the second mirror760.

After striking an object, reflected light passes back through the window316, reflects off the second mirror760, reflects off the first mirror755, and passes back through the quarter wave plate750. In reflecting off the object, the handedness of the circularly polarized light is reversed. As a result, when passing through the quarter waveplate on the reverse path, the light is converted back to linear polarization oriented at 90 degrees with respect to the outgoing beam of light reflected off the polarizing beam splitter745. The returning light reaching the polarizing beam splitter745is oriented in the direction of minimum reflection (maximum transmission) of the polarizing beam splitter745, enabling the returning light passes through the polarizing beam splitter745with low loss. This arrangement of using a quarter wave plate in combination with a linearly polarizing beam splitter to reduce loss provides a advantage over prior art light projectors. In the usual light projector system, half of the light is lost on a beam splitter on the way out of the light projector and half of the light is lost on the beam splitter on the way back into the light projector. In other words, with the quarter wave plate method described herein, the returning light level may increase by a factor of four than would otherwise be the case.

The returning light passes through an optical bandpass filter765that rejects wavelengths outside a narrow band around the projected laser wavelength. In an embodiment, the laser710emits light at 520 nm, and the bandpass filter is also centered at 520 nm. A lens770focuses the light, which passes through a pinhole775before traveling to a beam splitter780. In an embodiment, the beam splitter780transmits 80 percent of the light and reflects 20 percent of the light. In an embodiment, part of the light is transmitted to a relatively high sensitivity silicon photomultiplier (SiPM) detector785, and another part of the light is reflected to a relatively low sensitivity SiPM detector790. In an embodiment, the higher sensitivity detector is approximately one thousand times more sensitive than the lower sensitivity detector. By providing two SiPM detectors having different sensitivities, a greater variety of objects can be measured with a scanned laser beam. A range of detector sensitivities is useful, for example, in measuring near objects and far objects and in measuring objects having reflectance ranging from high to low.

In sending the light from the folding beam splitter740to the polarizing beam splitter745, a small amount of light may be transmitted through the beamsplitter. A beam dump795absorbs this small amount of light, minimizing any stray, unwanted light. In an embodiment, the beam dump795includes an anti-reflection (AR) coated neutral density (ND) filter796and a low-reflectance block797such as black felt.

FIG.8is a schematic representation of optical elements included inFIG.7, with numbering of all optical elements the same as inFIG.7.FIG.9is a cross-sectional view of optical components and their optomechanical supports, with numbering of elements the same as inFIG.7.FIG.10is a top view andFIG.11is an isometric view of optical components and their optomechanical supports, with the numbering of elements the same as inFIG.7. A first optics tube1010supports the first lens assembly720and the second lens assembly725. A focus stepper mount1012affixes the first optics tube1010to the focusing mechanism730. A tube clamp1014affixes the first optics tube1010to the beam splitter housing1030. A power monitor assembly1020that includes an optical detector742is attached to the beam splitter housing1030. An adapter mount1032attaches the quarter wave plate750to the beam splitter housing1030. In addition, the polarizing beam splitter745, the AR coated ND filter796, the low-reflectance block797, and a second optics tube1040attach to the beam splitter housing1030. A pinhole-adjuster assembly1050provides an interface between the second optics tube1040and an SiPM detector assembly1060.FIG.12is an exploded isometric view of the beam splitter housing1030and attached components numbered as inFIG.7. Optical detector PCBA741includes the optical detector742(FIGS.7,8).

FIG.13is an exploded isometric view of a return optics assembly1300that includes a retaining ring1302, the optical bandpass filter765, a spacer1304, the lens770, the second optics tube1040, a wave spring1310, the x-y adjustment assembly1050, a z-alignment ring1320, an ND filter1330, a dual-sensor mount1340, the beam splitter780, a first SiPM PCBA1390, and a second SiPM PCBA1385. In an embodiment, the first SiPM PCBA1390includes the relatively low sensitivity SiPM detector790, while the second SiPM PCBA1385includes the relatively high sensitivity SiPM detector785. The pinhole-adjuster assembly includes an x-y adjustment assembly1050, which is coupled to a z-adjustment assembly that includes the second optics tube1040, the z-alignment ring1320, and the wave spring1310. The pinhole aperture is a small plate having a small hole, ordinarily less than 100 micrometers in diameter. The x-y adjustment assembly1050includes a threaded x hole1051and a similar hole on the opposite side of1051. In an embodiment, a compression spring is placed in one of these holes followed by a set screw. A set screw is screwed into the opposite threaded x hole. By adjusting the positions of the set screws, the pinhole can be adjusted in the x direction. The x-y adjustment assembly1050further includes a threaded y hole1052and a similar hole on the opposite side of1052. In an embodiment, a compression spring is placed in one of these holes followed by a set screw. A set screw is screwed into the opposite threaded y hole. By adjusting the positions of the set screws, the pinhole can be adjusted in the y direction. The x-y adjustment stage slides into the z-alignment ring1320until the edge1053of the x-y adjustment stage encounters the circular ridge1054of the z-alignment ring1320. With the x-y stage in this position, the holes1051,1052are accessible allowing the x-y adjustment to be made after the attachment to the z-alignment ring. The z-alignment ring has an internal thread that matches the external thread of the second optics tube1040. The wave spring1310is placed against the x-y adjustment ring1050. The spring provides a force to keep the edge1053in contact with the circular ridge1054as the z-alignment stage is screwed in and out to obtain the proper pinhole aperture position in the z-direction. A cross-sectional view of the elements of the pinhole aperture and pinhole adjustment assembly is shownFIG.9.

By adjusting the set screws, the pinhole aperture can be centered on the returning light. The pinhole aperture775(FIGS.7,8,9) helps to block unwanted background light from the environment outside the enclosure of the light projector10. Examples of such unwanted background light blocked by the aperture include artificial light and sunlight, both direct and reflected. In a further embodiment, the frame that holds the lens and pinhole assembly is at least partially covered with a coating to suppress reflections from the light traveling between the lens770and the pinhole775. In the embodiment illustrated inFIG.9, the inner elements of the frame that may be coated include an inner portion of the second optics tube1310and an inner portion of the x-y adjustment assembly1050. In an embodiment, the coating applied to the inner elements of the frame is a material such as Acktar Magic Black coating that can reduce reflections from metal to about one percent for visible wavelengths. Acktar Ltd. Has its headquarters in Kiryat-Gat, Israel.

FIG.14is an exploded isometric view of the focusing mechanism730, along with components attached to and actuated by the focusing mechanism730. The focusing mechanism includes a stepper motor1410, a retaining ring1412, the focus stepper mount1012, a spring1420, an oversized washer1430, a focus slide connector1440, a lock washer1416, and a nut1418. Elements attached to the focusing mechanism730include the tube clamp1014, the first optics tube1010, the first lens720, a retaining ring1414, and a sliding focus assembly1450.FIG.9shows a cross-sectional view of the three elements of the sliding focus assembly1450, which include the sliding focus mount1451, the second lens725, and the retaining ring1452. The sliding focus mount1451is attached to the focus slide connector1440with a screw1453, as shown inFIG.9. The stepper motor1410includes a threaded portion1411that passes through hole1441in the focus slide connector1440. The lock washer1416and nut1418attach to the threaded portion1411of the stepper motor. The spring1420and the oversized washer1430provide compressive force to hold the focus slide connector1440firmly to against the lock washer1416. The focus slide connector1440also includes a rod1444used to trigger a photogate sensor when setting a home position for the focus slide connector1440.

The purpose of the focusing mechanism730is to focus the beam of light from the light projector10on an object of interest. A method for making this adjustment using a focusing mechanism is described in commonly owned U.S. patent application Ser. No. 16/017,360 filed on Jun. 25, 2018, the contents of which are incorporated by reference herein.

FIG.15is an isometric view of the optical components and their optomechanical supports as shown inFIG.14with the addition of an optoelectrical control board1400. The optoelectrical control board includes electrical circuits to cooperate with PCBAs having optical detectors742,785, and790. It also includes electrical circuits to control the focusing mechanism730.

FIG.16is a cross-sectional side view of the light projector system10. Shown are the front cover assembly20, the base assembly30, the power assembly40, the fan assembly50, and the rear assembly60. The base assembly includes the base housing702, an outer portion of which includes the grooved heat sinks35. Shown within the base assembly30are the optoelectrical control board1400, some optical and optomechanical components, and some PCBAs1610. The power assembly40includes batteries510,512, and the circuit board compartment520. The fan assembly50includes the fan plenum610and a cooling fan620. The rear assembly60includes the rear panel410and the power distribution PCBA420.

FIG.17is a block diagram of electrical modules1700within the light projection system10according to an embodiment. Each module may be constructed and tested separately from the other modules. In most cases, each module includes a PCBA. Electrical modules1700include optics module1710, front panel module1720, laser module1730, electronics processing module1740, galvo module1750, back-panel module1760, power/battery module1770, and fan module1780.

FIG.18Ais a block diagram of electrical elements of the optics module1710. In an embodiment, the optics module1710includes the first SiPM PCBA1390, the second SiPM PCBA1385, the optical detector PCBA741. Electrical signals from the first SiPM PCBA1390and the second SiPM PCBA1385go to an analog section1802that includes a transimpedance amplifier and other electrical conditioning components. The analog section1802includes an analog-to-digital converter (ADC) that converts the processed analog signals to digital signals for transmission to a complex programmable logic device (CPLD)1810for further processing. The processed signals from the CPLD1804pass over wires to the carrier-opto controls connector1810A. Electrical signals pass between the carrier/opto-controls connector1810A over a cable182to a carrier/opto-controls connector1810B on the electronics processing module1740. The electrical signal from the optical detector PCBA741is sent to power monitor1820, which provides processed data to a processor device, which in an embodiment is a programmable system-on-a-chip (PSoC)1825. A PSoC is a family of microcontroller integrated circuits manufactured by Cypress Semiconductor, a company having headquarters in San Jose, Calif. Other types of processor devices different than a PSoC may be used in place of the PSoC1825. In an embodiment, the PSoC1825sends signals to an I2C controller1830that sends one set of control signals1831to the four status LED PCBAs340and other signals1832to the IR LED PCBA370. The PSoC1825also sends signals to a stepper controller1835that sends signals to the stepper motor1410, which adjusts the position of the second lens725to focus the projected light on an object. The home switch1837sets a home position by triggering when the rod1444passes in front of a photogate sensor.

FIG.18Bis a block diagram of electrical elements of the front panel module1720and the laser module1730. The laser module1730includes a laser1733having a built-in thermistor1734and in contact with a thermoelectric controller (TEC)1735. The laser1733and built-in thermistor1734are included in the laser710(FIG.7). The laser module1730further includes a TEC PCBA1731, and a laser driver PCBA1732. Power is provided to the TEC PCBA1731over the line1840from the optics module1710. Additional power is supplied to the laser driver PCBA1732by the +12 V supply over the line1843. on the optics module provides power to the TEC PCBA1731over the line1840. The laser driver PCBA receives additional control signals via control line1841from the PSoC1825and1842from the cable1811. The thermistor1734measures the temperature of the laser1733and provides the measured temperature to the TEC PCBA1731, which adjusts the TEC1735to hold the laser temperature to a desired set point.

FIG.18Cis a block diagram of electrical elements of the electronics processing module1740, the galvo module1750, and the back-panel module1760. The electronics processing module1740includes a carrier PCBA1845for a System-On-Module (SOM)1850and a collection of additional electrical components that interface with the SOM. In an embodiment, the SOM is a PicoZed, a device sold by Avnet and based on models of Xilinx System-on-a Chip (SoC). Avnet has its headquarters in Phoenix, Ariz. Xilinx has its headquarters in San Jose, Calif. The SOM1850is placed on the carrier PCBA1845that includes a Wi-Fi and Bluetooth component1852that interfaces with an antenna1853. The SOM1850also supports a Wi-Fi LED PCBA1854. Wi-Fi is a trademark of the non-profit Wi-Fi Alliance. Wi-Fi devices are compliant with the IEEE 802.11 standard. Bluetooth is a wireless technology standard used for exchanging data between fixed and mobile devices over short distances using radio waves between 2.4 and 2.485 GHz. Bluetooth standards are maintained by the Bluetooth Specification Working Group (CSWG). The Wi-Fi may be used as a client to interface with already established network or as an access point for establishing links to computers or other instruments not connected to a network. The carrier PCBA1845supports a laser power switch1855for turning the laser710on and off. The carrier PCBA1845includes low-voltage differential signaling (LVDS) circuitry1857to the standard RS-422, also known as TIA-EIA-422. This technical standard specifies the electrical characteristics of a differential, serial communication protocol. The SOM supports Ethernet and is interconnected through the ribbon cable422to the Ethernet connector524on the power assembly40. The first header423for the ribbon cable422resides in the back-panel module1760. The carrier module1845further includes a MicroSD card slot1860that enables reading and writing of data on MicroSD cards. In an embodiment, the SOM1850communicates with the camera PCBA366over a Universal Serial Bus (USB) link1722. USB is an industry standard maintained by the USB Implementer's Forum.

The back-panel module1760includes an environmental logger PCBA430that in an embodiment includes two accelerometers for measuring two different maximum acceleration levels. It also includes a combination humidity/temperature sensor, an oscillator to drive a real-time clock, and nonvolatile memory for logging extreme events with time stamps. Such extreme events may include large shocks, relatively very high temperatures or humidities or relatively very low temperatures. A battery440is provided to power the elements in the environmental logger PCBA430even when the power to the unit is turned off, for example, when a unit is shipped with batteries removed. The battery440also provides short term power for the carrier PCBA1845for around a minute when batteries510,512are removed and electrical power is otherwise not provided. In this way, state information for the system is preserved long enough to allow a battery to be exchanged. The battery440also provides power to an 8-bit microcontroller1864that is attached to a nine-axis MEMS inertial measurement unit (IMU)1865.

FIG.18Dis a block diagram of the power/battery module1770. The OR controller1870cooperates with the power prioritizer1867and the main load switch1866to determine the amount of current, if any, drawn from each of the first battery510and the second battery512. Some of the resulting power is provided to DC-DC converter1862that produces −15 volts and DC-DC converter1863that produces +15 volts. These voltages are provided to the digital signal processor (DSP) in the galvo module1750. AC power is provided through the input port522, which is sent to an electrical input filter PCBA1872and on to an AC-DC converter1874that convert AC voltages between 100 and 240 VAC into a DC voltage of +15 VDC. The Ethernet input signal is sent to a magnetics unit1876that serves as an isolation transformer for the Ethernet signal. An LED driver1878provides signals to a first battery LED status indicator or DSP1890and a second battery LED status indicator or DSP1892.

FIG.18Cshows the electrical elements of the galvo module1750that support the galvo motor assemblies757,762. In an embodiment, the electronics of the galvo module make use of electrical and algorithmic methods to reduce the power consumed by the galvo motors while continuing to provide high visibility in the pattern of light projected by the light projector10. Methods for obtaining this power reduction are described in commonly owned U.S. Patent Application No. 62/925,257 filed on Oct. 24, 2019, the contents of which are incorporated by reference herein. These methods include adjusting the output of a power control module based at least on one or more calculated parameters that control the trajectory of the projected beam of light on the object. In an embodiment shown inFIG.18C, a power amplifier1882drives an XY galvo module1884that controls the movements of the galvo motor assemblies757,762. In an embodiment, the parameter-based trajectory is determined at least in part by the DSP1880. In an embodiment, one of the calculated parameters is the refresh rate for the flicker-free threshold of the projected beam of light. In an embodiment, the power amplifier1882is a switching mode current amplifier having an output based on a configurable effective duty cycle.

InFIG.19, the light projector10projects a glowing pattern of light1910onto an object of interest1920. This glowing pattern of light is sometimes referred to as a “template.” In general, the projected pattern of light1910is repeated periodically at a given time interval, which is the period of the projected pattern. The reciprocal of the period of the projected pattern is called the refresh rate. If the refresh rate is too low, the glowing pattern will appear to observers to be flickering and will appear to flash at regular intervals. A flickering pattern can cause observers to experience fatigue, dizziness, and headaches. To avoid this problem, the refresh rate is set high enough that a viewer observes the glowing pattern as a steady, flicker-free image. Such a flicker-free image is related to persistence of vision experienced when viewing motion pictures in cinema or on television. In some embodiments, it is also desired that the projected glowing pattern of light1910be bright enough to be clearly visible to an observer. At the same time, it is desired that a glowing pattern of light1910meet the eye safety limit for laser light.

In addition to projecting a glowing pattern of light1910on an object of interest1920, light projectors10are also used to scan fiducial targets such as the targets1930A,1930B,1930C,1930D with the same beam1905used to produce the glowing pattern of light1910. In some cases, the fiducial targets have been made of retroreflective materials, while in other cases the targets are features that are reflective but not retroreflective.

Historically, industrial light projector systems have used continuous wave (cw) lasers with on/off controls to project multi-segment glowing templates. However, the visibility of a glowing pattern of light1910produced by a cw laser is limited by the allowable average laser beam power. The visible brightness of projected continuous lines is proportional to the reflectivity of the object's surface and inversely related to the projected line width and the distance from the projector to the object.

A prior art reference disclosing improvement of laser projection visibility is disclosed in U.S. Pat. No. 7,385,180 to Rueb, et al., issued on Jun. 10, 2008. The suggested solution prescribes decreasing the maximum beam steering speed, resulting in a flickering image. Although such an approach increases visibility, it does so at the expense of user headaches and dizziness.

A prior art approach to improving visibility without flickering is disclosed in commonly held U.S. Pat. No. 8,085,388 to Kaufman, et al., issued on Dec. 27, 2011. This approach uses a pulsed laser, such as a Q-switched laser, having a fixed repetition rate. A beam-steering control is synchronized with the generated laser pulses to produce a projection consisting of stationary spots1912. Although an improvement over prior art solutions, this approach could not be optimized to deliver the best possible visibility of the projected laser light for different trajectories of the projected beam while also meeting eye laser safety requirements. Another shortcoming of this approach is the need for relatively complicated and expensive signal processing.

In an embodiment, the glowing pattern of light1910includes dotted contours1912as inFIG.19. In an embodiment, the dots1912appear to be stationary to the human eye though the projected trajectory is created by dynamically steering the laser beam as a periodic function of time. In an embodiment, the dots1912are formed by pulsed laser light having a selectable repetition rate. A beam steering control produces variable acceleration and velocity through a stream of incremental position commands precisely synchronized with the timing of the laser pulses. The frequency and duration of the laser pulses are selected based at least in part on a selected beam angular velocity that maintains a reasonable separation between the dots while maintaining a peak optical power that meets the laser eye safety limits. To implement such a collection of dots with the light projection system10. In an embodiment, the laser710has modes for generating both pulsed light and cw light. In an embodiment, the pulsed laser light may rapidly change repetition rate, peak power, and pulse duration. In an embodiment, the cw laser has a variable power level. In an embodiment, the laser source is a semiconductor laser having analog functionality for modulating the laser beam in time. In an embodiment, the light projector10ordinarily uses the pulsed mode of operation when projecting the glowing pattern of light1910on the object as a collection of dots1912. It ordinarily uses the cw mode of operation when scanning fiducial targets and features such as1930A,1930B,1930C,1930D in raster scan patterns1932A,1932B,1932C,1932D, respectively. In an embodiment, the analog section circuit1802(FIG.18A) converts the detected signal from analog to digital form before sending it to the CPLD1804for further processing. In an embodiment, the optical detector741and the power monitor1820are used to guarantee fail-safe system operation in multiple laser control modes by limiting the average output power and, if desired, the laser pulse energy according to the assigned laser safety class.

In an exemplary light projector10, the beam steering angular velocity reaches up to about 200 radians per second, with beam steering angular accelerations reaching up to about 200,000 radians per second squared.FIG.20illustrates an exemplary velocity trajectory2010constructed of piece-wise segments.FIG.20also shows the resulting position trajectory2020, which is found by integrating the velocity trajectory over time. In an embodiment, beam-steering servo control is provided by the DSP1880of the galvo module1750(FIG.18C). In an embodiment, the DSP1880sends real-time position commands to the galvo motor assemblies757,762at equal time intervals (“time ticks”) of between 10 and 80 microseconds. Because the time intervals are much smaller than the reaction time of the galvo motor assemblies757,764, the position commands executed in each time interval produce a smooth motion. This is illustrated inFIG.21, where incremental position movements at time intervals T produce a smooth position trajectory2110.

In an embodiment, the carrier PCBA1845provides a master clock that sends synchronization signals to the DSP1880in the galvo module1750and through the cables1811,1842to the TEC PCBA1731.FIG.22is a schematic illustration showing how galvo movements and laser emissions are synchronized to produce a glowing pattern2210on an object. The glowing pattern includes a collection of glowing dots2212. A line2214connecting the dots is ordinarily not visible on the object. In an embodiment, a complete collection of the dots2212is projected once each cycle beginning with an initial projection point2216. In an embodiment, both galvo mirrors755,760are completely settled in their positions at the initial projection point2216. The direction of movement of the projected dots during a cycle is indicated by the arrows2218. Clock pulses2222of the master clock pulse train2220are separated by the time intervals (time ticks) T. In an embodiment, the laser beam is emitted at each time interval, with one of the dots2212produced with each emission. In an embodiment, the amount of separation between adjacent dots2212is determined by the movement of the galvo mirrors755,760between laser emissions. In an embodiment, this movement is determined by signals sent from the DSP1880to the power amplifier1882in the galvo module1750. These signals are indicative of a position trajectory2230inFIG.22, also discussed herein in reference toFIG.21. The distance between successive dots2212are command increment distances2232calculated for each interval. Because of the dynamic integration of small individual command increments resulting in a smooth, reproducible motion profile, the locations of the laser dots2212appear stationary to the human eye, even though the trajectory path is created by a moving pulsed laser beam. Although in the discussion herein above, the laser pulses were synchronized to command increment distances between dots2212, a stationary pattern would still be created even if the time between laser pulses were a little different than the time between calculated position increments as long as the galvo mirrors755,760came to a stop at the start of each period at the projection point2216beam position.

Visibility of a glowing pattern2210formed by a focused moving laser beam, either continuous or pulsed, is determined by its local average irradiance, in units of optical power per unit area, along the trajectory path. This is illustrated inFIG.23Afor continuous laser operation and inFIGS.23B,23C,23Dfor pulsed operation. To simplify calculations, the shape of the focused laser spot2312inFIG.23Ais a square, each side having a dimension a. For the case of cw laser operation that produces a periodically projected continuous glowing line section2310formed by a continuously moving laser spot2312having a linear velocity v, a projection refresh period T, a spot side dimension a, and a cw beam power P0, the average irradiance A0of the glowing line section as seen by a viewer is
A0=(P0/a2)(a/L)=P0/(vTa)  (Eq. 1)

Here, the length L of the periodically projected line2310is L=v·T. For the case of continuous laser operation, the average output power PAis equal to the cw laser power P0.

FIG.23Dshows a pulse train2320of individual laser pulses2322each having a pulse width τ, the time interval between pulses t, and a peak power P1. The average output beam power PAof the pulse train2320is
PA=P1τ/t.(Eq. 2)

FIG.23Cshows a periodically projected pattern2330having isolated areas2332illuminated during the laser pulses2322. The projected spots are blurred over the pulse width τ by the movement of the beam at the linear velocity v. If the velocity is constant over the pulse width, then the velocity is equal to
v=a/τ,(Eq. 3)

And the illumination distribution across each area2332has a triangular shape2340that occupies a length
b=2a(Eq. 4)

If the pulses are synchronized with the beam motion control as described herein above, the isolated areas2332appear to be stationary to the human eye, and the isolated areas2332occupy the same locations in the path2334for every period of projection. In this situation, the separation s between adjacent areas2332is
s=t·v.(Eq. 5)

The average irradiance A1of a single laser dot in an isolated area2332as it appears to a viewer eye is
A1=(P1/2a2)(a/L).  (Eq. 6)

Noting that for the case of a cw laser beam, the average output power is equal to the cw laser power, PA=P0, and combining Eqs. (1)-(6) give the results
A1=A0s/b,(Eq. 7)
ands/b=t/(2τ).  (Eq. 8)

Eq. (7) says that average irradiance of an individual laser dot in area2332as viewed by an observer's eye is higher by a factor s/b than the average irradiance of a continuously moving laser spot2312emitted by a cw laser. Hence it is possible to improve visibility using a pulsed laser beam to produce dots that appear stationary to a user. As an example, to achieve an increase in the irradiance of 5 to 10 times in a glowing pattern of light seen by an observer, the ratio s/b would ordinarily be held to at least 10:1.

The discussion above made some simplifying assumptions such as the shape of the moving laser spot (square rather than Gaussian shape, for example). If desired, more detailed calculations can be performed to eliminate the simplifying assumptions. In general, the effective spot size is a function of pulse width, linear velocity, and simplified spot size: b=F(τ,v,a).

An aspect of an embodiment is obtaining high visibility of the dots that appear stationary while keeping within laser safety requirements. This is done by adjusting a combination of parameters, including average laser power, pulse repetition rate, instant pulse energy, focused laser spot size, distance between the light projector10and the object, and the beam steering angular velocity.

In an embodiment, the relevant laser safety standard in most cases is the International Standard on Safety of Laser Products IEC 60825-1. This standard defines Accessible Exposure Limits (AEL) by limiting the average laser power, the single pulse energy, and the energy per pulse within a pulse train for each defined Laser Safety Class. In other embodiments, other standards or safety guidelines are followed instead of, or in addition to, those of IEC 60825-1.

For galvanometer-based laser light projectors such as the light projector10, usually the relevant laser quantities from IEC 60825-1 are average laser power and single pulse energy. Allowable levels for these quantities are established for different laser classes. For the light projector10, usually projectors are either class 2 or class 3R. For projection of visible wavelengths, the average optical power limits are 1 mW for class 2 and 5 mW for class 3R.

According to the 2014 edition of IEC 60825-1, the maximum single pulse energy for visible light pulses shorter than 5 microseconds is 77 nJ (nanojoules) for class 1 and class 2 and 380 nJ for class 3R.

For a single pulse energy EPand an average power PAof a pulse train, the periodicity of pulses is given by
t=EP/PA.  (Eq. 9)

Hence for a class 2 laser at the optical power limit of 1 mW and a pulse energy limit of 77 nJ, the periodicity of laser pulses in a pulse train must be separated by at least H=77 nJ/1 mW=77 μs. In this document, the symbol H is used to represent the maximum allowable periodicity. Many values are possible for the allowable periodicity H according to the standard being considered.

For pulsed laser operation, a value is obtained for a maximum allowable linear spacing between projected dots. Spacing between the dots must be small enough to provide an operator with guidance to align and place items in a manufacturing or construction projector. In an embodiment, the spacing s is a constant. The light projector10has maximum achievable angular velocity vang(in units of radians per second) for the projected beam of light. In an embodiment, the periodicity t between pulses is determined with the equation t=s/(D·vANG). In one embodiment, D is the average distance between the light projector10and the object. Under this condition, the quantities s, D, and vangare fixed so that the periodicity t between adjacent laser pulses is also fixed. In another embodiment, the distance D is taken to be the actual distance to each point, which then produces a periodicity t that changes with the distance D.

In an action, one of two branches is taken according to whether the periodicity t between pulses is less than or equal to the pulse train periodicity threshold H. If t≤H, then for an allowable average power limit PAvLimand a maximum available peak laser power PPkMax, the pulse width τ and peak power P1are set to
τ=t·PAvLim/PPkMax,  (Eq. 10)
P1=PPkMax.  (Eq. 11)

The calculated values for the periodicity t, the pulse width τ, and the peak pulse power P1are selected to provide control of the laser when running in pulsed mode. The laser beam is steered by the galvo steering mirrors755,760in response to signals sent from the DSP1880. The trajectory produced by the galvo steering mirrors755,760is synchronized to the laser pulses.

For cw laser operation, the processor calculates the trajectory of the glowing pattern. The average output power is set less than or equal to the laser safety limit: PAv≤PAvLim. The galvo steering mirrors755,760move the laser beam along a predetermined trajectory, taking steps with free running motion control ticks T as inFIG.21.

For both pulsed and cw laser operation, the power monitor assembly1020monitors the output of the laser monitor to guarantee fail-safe operation of the system to meet laser safety requirements. In an embodiment, when the light projector10is operating in cw mode and the average emitted laser power PAvexceeds the laser safety limit PAvLim, circuitry in the power monitor1820in the optics or front panel module1720causes the PSoC1825to send a signal to the laser driver PCBA1732over the control line1841to shut down the laser710. In an embodiment, when the light projector10is operating in pulsed mode, the power monitor1820causes the PSoC1825to send a signal to the laser driver PCBA1732to shut down the laser if the energy of a single laser pulse energy exceeds the allowable emission limit for pulse energy for the given periodicity t, for example, as given in IEC 60825-1 or other applicable laser safety standard.

Today, it can happen that a light projector system projects so many patterns on an object that the time to project all the patterns is larger than the flicker limit, resulting in the undesirable flicker effect described earlier. A way that has been developed for countering this problem is for an operator to place a reflective or retroreflective material in the path the projected pattern. The presence of this material is detected by the light projector system and interpreted as a command by the operator. Such a command might indicate, for example, to zoom in on the region near the detected material, thereby illuminating only a portion of the whole pattern and causing the flickering to stop. In another case, the command might direct the light projector to begin projecting the next pattern in a sequence of patterns. Such a command might be used, for example, in a multi-ply layout procedure used with carbon-fiber composite structures in which a different pattern is projected for each new ply.

These methods for inserting a reflective material into the path of projected beam of light work well for projectors operating in cw mode. However, this method does not in general work for the case in which stationary dots are projected onto an object at position2216, as the dots do not necessarily intercept the reflective material. The projection of dots is particularly problematic if the reflective pattern inserted into the projected light pattern contains multiple separate elements that together provide a coded command in which the command depends on the arrangement of the separate elements.

FIGS.24A,24B,24Cshow three reflective coded patterns2400,2410,2420, respectively, having one, two, and three reflective elements2402,2412,2422, respectively, that reflect patterns of light2404,2414,2424, respectively. If a cw beam of light strikes these reflective coded patterns, the pattern of reflected light is detected by optical detectors such as the SiPM detectors1385,1390and the pattern identified by a processor within the light projector10. In contrast, when the light projector is operating in the pulsed mode, as illustrated inFIG.24D, the reflective portion2432of the coded pattern2430will not necessarily reflect light from one of the dots2434. In an embodiment, the operator moves the target along the path2436until one of the reflective elements reflects one of the dots back to the light projector10. In most cases, the reflectivity of the reflective portion of a reflective coded pattern will be relatively much larger than the amount of light reflected from the object. The processors within the light projector10notice this increase in reflected light and, in response, cause the light projector10to switch to cw mode, projecting a short segment of light2440over the coded pattern2442as illustrated inFIG.24E. In an embodiment, the segment of light is long enough to identify the nature of the pattern within the coded pattern. In an embodiment, the light projector may return to pulsed mode or remain in cw mode depending on the nature of the coded message contained in the coded pattern.

According to another embodiment, another method is provided. The method includes: steering a pulsed laser beam to form a first pattern of stationary dots on an object; placing a reflective target to intercept one of the dots; and detecting a change in reflected light and, in response, switching the laser from pulsed mode to continuous-wave (cw) mode.

In addition to one or more of the features described herein, or as an alternative, further embodiments of the method may include detecting a second pattern of laser light reflected from the reflective target when the laser is in cw mode and, in response, taking an action based on the detected second pattern. In addition to one or more of the features described herein, or as an alternative, further embodiments of the method may include the action that steers the pulsed laser beam to form a third pattern of stationary dots on the object, the third pattern covering a smaller area than the first pattern.

According to another embodiment, another device is provided. The device including a laser operable to produce a pulsed laser beam and a continuous-wave (cw) laser beam. A beam-steering system is operable to steer the pulsed laser beam onto an object to create a first pattern of stationary dots on the object. A reflective target is provided. An optical detector is operable to detect reflected laser light. One or more processors are operable to determine that the detected laser light has been reflected by the reflective target and, in response, causing the laser to emit the cw laser beam and further causing the beam-steering system to steer the emitted cw laser beam into a segment of light on the reflective target

In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include the one or more processors being operable to determine that the cw laser beam, when reflected from the reflective target and detected by the optical detector, has a second pattern, the processor taking a further action based on the determined second pattern. In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include the further action that steers the pulsed laser beam to form a third pattern of stationary dots on the object, the third pattern covering a smaller area than the first pattern.

According to another embodiment, another device is provided. The device includes a beam-steering system operable to project a pattern of laser light onto an object, the beam-steering system including a first galvanometer operable to rotate a first mirror and a second galvanometer operable to rotate a second mirror, the first galvanometer further including a first angle transducer to measure a first angle of rotation of the first mirror, the second galvanometer including a second angle transducer to measure a second angle of rotation of the second mirror. An optical detector is operable to detect laser light reflected the object. A processor is operable to discern features of the object based at least in part on the optical power of the reflected laser light and on the measured first angle and the measured second angle. A first battery is operable to automatically provide electrical power to the device in the absence of electrical power from a power mains.

In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include a second battery operable to provide electrical power to the device, wherein the first battery or the second battery may be removed from or placed into the device without first turning off power to the device. In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include a supplemental backup battery providing temporary backup power to preserve device state information when electrical power is available from neither the battery nor the power mains. In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include circuitry to balance electrical power extracted from the first battery and the second battery based at least in part on charge remaining in the first battery and the second battery.

According to another embodiment, another method is provided. The method includes: providing a system having a laser, a beam-steering system, an optical detector, and a first battery; generating laser light with the laser; projecting the laser light onto an object with the beam-steering system, the beam-steering system having a first galvanometer and a second galvanometer, the first galvanometer steering laser light off a first mirror and measuring a first angle of rotation of the first mirror, the second galvanometer steering the laser light off a second mirror and measuring a second angle of rotation of the second mirror; detecting with the optical detector the laser light reflected from the object; discerning features of the object based at least in part on the optical power of the detected laser light and on the measured first and the measured second angle; monitoring to determine whether the system is being provided with electrical power through a power mains; and providing the system with electrical power the first battery when monitoring has determined that the power mains is not providing the system with electrical power.

In addition to one or more of the features described herein, or as an alternative, further embodiments of the method may include providing the electrical system with a second battery and providing the system with electrical power from the second battery. In addition to one or more of the features described herein, or as an alternative, further embodiments of the method may include adding the second battery to the system or removing the second battery from the system without first turning off power to the system. In addition to one or more of the features described herein, or as an alternative, further embodiments of the method may include providing the system with a supplemental backup battery; monitoring to determine whether the system is being electrical power from any source; and providing the system with temporary backup power to preserve device state information when electrical power is not being provided to the system from any source.

In addition to one or more of the features described herein, or as an alternative, further embodiments of the method may include balancing electrical power extracted from the first battery and the second battery based at least in part on charge remaining in the first battery and the second battery.

In another embodiment, another device is provided. The device includes a beam-steering system operable to project a pattern of laser light onto an object, the beam-steering system including a first galvanometer operable to rotate a first mirror and a second galvanometer operable to rotate a second mirror, the first galvanometer further including a first angle transducer to measure a first angle of rotation of the first mirror, the second galvanometer including a second angle transducer to measure a second angle of rotation of the second mirror. An optical detector is operable to detect laser light reflected the object. A processor is operable to discern features of the object based at least in part on the optical power of the reflected laser light and on the measured first angle and the measured second angle. A wireless communication system is operable to transmit and receive wireless data.

In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include the wireless communication system includes a Wi-Fi transceiver module based on the IEEE 802.11 family of standards, the Wi-Fi module operable to transmit and receive data wirelessly. In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include the Wi-Fi transceiver module being operable to communicate with Wi-Fi device connected to a network. In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include the Wi-Fi transceiver module is further operable to communicate with a Wi-Fi device not connected to a network, the communication made through an access point on the device. In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include the wireless communication system having a Bluetooth transceiver module operable to exchange data wirelessly with a Bluetooth enabled device.

According to another embodiment, another device is provided. The device includes a beam-steering system operable to project a pattern of laser light onto an object, the beam-steering system including a first galvanometer operable to rotate a first mirror and a second galvanometer operable to rotate a second mirror, the first galvanometer further including a first angle transducer to measure a first angle of rotation of the first mirror, the second galvanometer including a second angle transducer to measure a second angle of rotation of the second mirror. A first optical detector is operable to detect laser light reflected the object. A second optical detector is operable to detect the laser light reflected from the object, the second optical detector having a higher sensitivity than the first optical detector. A beam splitter is operable to send a first portion of the laser light reflected from the object to the first optical detector and to send a second portion of the laser light reflected from the object to the second optical detector. A processor is operable to discern features of the object based at least in part on the measured first angle, the measured second angle, and on at least one of the optical power of the first portion and the optical power of the second portion.

In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include the sensitivity of the second optical detector is at least one hundred times higher than the sensitivity of the first optical detector. In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include a pinhole aperture; a lens operable to focus the laser light reflected from the object; and a pinhole adjustment mechanism operable to adjust the position of the pinhole aperture to pass the focused laser light to the beam splitter. In addition to one or more of the features described herein, or as an alternative, further embodiments of the device may include a housing to hold the lens and the pinhole aperture, the housing being at least partially covered with a coating to suppress scattering of light between the lens and the pinhole aperture.

According to yet another embodiment, a pinhole assembly is provided. The pinhole assembly including a pinhole aperture. A pinhole x-y adjustment mechanism is provided having a first screw and a first spring that each push in the x direction against the pinhole aperture, the first spring arranged to apply a force opposing the push of the first screw, the pinhole x-y adjustment further having a second screw and a second spring that each push in the y direction against the pinhole aperture, the second spring arranged to apply a force opposing the push of the second screw. A pinhole z-adjustment mechanism is provided having a tube with external threads, a ring with internal threads, and a third spring, the ring being placed over the pinhole x-y adjustment mechanism and the third spring and then screwed onto the tube, the ring constraining the z-position of the pinhole x-y adjustment mechanism while providing access to the first screw and the second screw for adjusting the x-y position of the pinhole aperture.