Patent Publication Number: US-2020284880-A1

Title: Lidar with phase light modulator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. § 119(e) to co-owned U.S. Provisional Patent Application Ser. No. 62/815,090, filed Mar. 7, 2019, which is hereby incorporated by reference in its entirety herein. 
    
    
     TECHNICAL FIELD 
     This relates generally to ranging devices, and in particular to ranging and imaging devices using light. 
     BACKGROUND 
     Light detection and ranging (LIDAR) systems detect and determine the position of objects. In one example, a light beam is projected to a known position in a field of view. A light detector is focused on that position in the field of view and detects any reflection of the light from an object that may be in the field of view. The time the light travels is used to help determine the distance of the object. By scanning the light beam across the field, the position of objects in the field and an image of the objects can be determined. 
     A challenge with scanning-type LIDAR systems is scanning rapidly and accurately enough to capture movement of objects within the field. For example, in automotive applications, the LIDAR system must rapidly and accurately determine the movement of pedestrians and vehicles, as well as other objects. Mirrors have been applied to scan the beams. Other examples use gimbal mounts to move the entire light projection and detection system as one unit. However, it is difficult to operate these mechanical systems with sufficient accuracy. In addition, such systems are often bulky, have large power requirements, and require frequent maintenance and calibration to maintain accuracy. 
     SUMMARY 
     In accordance with a described example, an apparatus includes a phase light modulator. The apparatus also includes a first light source optically coupled to the phase light modulator, the first light source configured to generate a first light beam and positioned to direct the first light beam to the phase light modulator at a first angle of incidence, the phase light modulator configured modulate the first light beam to provide a first modulated light beam and to direct the first modulated light beam to a first field of view responsive to the first light beam; and a second light source optically coupled to the phase light modulator, the second light source configured to generate a second light beam and positioned to direct the second light beam to the phase light modulator at a second angle of incidence, the phase light modulator configured modulate the second light beam to provide a second modulated light beam and to direct the second modulated light beam to a second field of view responsive to the second light beam. The apparatus also includes a first light detector optically coupled to the first field of view and configured to detect the first modulated light beam as reflected from the first field of view and a second light detector optically coupled to the second field of view and configured to detect the second modulated light beam as reflected from the second field of view. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  (collectively “ FIG. 1 ) are diagrams illustrating light steering using phase light modulators (PLMs). 
         FIG. 2  is a side view of an example micromirror. 
         FIG. 3  is a top view of an example LIDAR apparatus. 
         FIGS. 4A-D  (collectively “ FIG. 4 ”) are views of a transmit portion of an example LIDAR apparatus and a scanning pattern used with the LIDAR apparatus. 
         FIGS. 5A and 5B  (collectively “ FIG. 5 ”) are views of a receive portion of the LIDAR apparatus of  FIG. 4 . 
         FIG. 6  is a diagram of another example LIDAR apparatus. 
         FIG. 7  is a flow diagram of an example method. 
         FIG. 8  is a flow diagram of another example method. 
     
    
    
     DETAILED DESCRIPTION 
     In the drawings, corresponding numerals and symbols generally refer to corresponding parts unless otherwise indicated. The drawings are not necessarily drawn to scale. 
     In this description, the term “coupled” may include connections made with intervening elements, and additional elements and various connections may exist between any elements that are “coupled.” Elements referred to herein as “optically coupled” are elements that include a connection between the elements that involves transmission of light. Also as used herein, a “phase light modulator” (PLM) is a device with a plurality of pixels, wherein the PLM may modify the phase of light applied to each pixel. The PLM may reflect or transmit the applied light. The interference of the light from the phase modified pixels and/or phase unmodified pixels modulates the applied light. 
     In example arrangements, the problems of slow scan rates and a narrow field of view (FOV) for a phase light modulator (PLM) steered light source are solved by providing at least two light sources to a PLM such that the light from each light source scans a different FOV contemporaneously. In at least one example, the LIDAR apparatus has a single PLM device used for at least two light sources. The light sources have different angular orientations relative to the PLM. Because of the different angular orientations, each laser illuminates a point in a respective field of view (FOV), and all FOVs are scanned contemporaneously and tiled together. In accordance with an example, an apparatus includes a phase light modulator. The apparatus also includes a first light source optically coupled to the phase light modulator, the first light source configured to generate a first light beam and positioned to direct the first light beam to the phase light modulator at a first angle of incidence, the phase light modulator configured modulate the first light beam to provide a first modulated light beam and to direct the first modulated light beam to a first field of view responsive to the first light beam; and a second light source optically coupled to the phase light modulator, the second light source configured to generate a second light beam and positioned to direct the second light beam to the phase light modulator at a second angle of incidence, the phase light modulator configured modulate the second light beam to provide a second modulated light beam and to direct the second modulated light beam to a second field of view responsive to the second light beam. The apparatus also includes a first light detector optically coupled to the first field of view and configured to detect the first modulated light beam as reflected from the first field of view and a second light detector optically coupled to the second field of view and configured to detect the second modulated light beam as reflected from the second field of view. 
     An example PLM is a digital micromirror based PLM. This type of PLM device includes a number of digital micromirrors on the surface of a substrate. In examples, this type of PLM may include hundreds of thousands of micromirrors or more than a million micromirrors. Each micromirror is designed so that its vertical position above the substrate can be precisely positioned using electrostatic force applied to the micromirror by driving circuitry in the substrate. The phase of light reflected from a particular micromirror is determined by the vertical position of the micromirror (vertical with respect to the substrate, which is horizontal for this discussion). For example, if a first micromirror is a its full height above the substrate and an adjacent second micromirror is lowered one fourth of a wavelength, the light reflected from the second micromirror travels one-half wavelength (one quarter wavelength down plus one quarter wavelength up) relative to light reflected from the first micromirror. The light reflected from the first and second micromirrors will then interfere in a predictable manner. The pattern of phase changes on a PLM may be selected to provide a desired diffraction-like effect, such as steering or focusing the light. See, e.g. McManamon et al., “Optical Phased Array Technology, Proc. of the IEEE, Vol. 84, No. 2, pp 269-298 (February 1996), which is hereby incorporated by reference herein in its entirety. Arbitrary patterns such as spots or beams can be created at a desired distance in the field of view. Another example PLM is a liquid crystal type phase light modulator. With this type of PLM, a voltage applied at each pixel alters the liquid crystal at that pixel to cause a phase shift of the light. Liquid crystal PLMs may be transmissive or reflective. 
       FIGS. 1A and 1B  (collectively “ FIG. 1 ) are diagrams illustrating light steering using PLMs. In this example, PLM  102  is a digital micromirror based PLM. In  FIG. 1A , micromirrors  104  of PLM  102  have a steering pattern selected to direct light  106  in direction  108 . In  FIG. 1B , micromirrors  104  have a pattern selected to direct light  106  in a direction  110 . Thus, PLM  102  can steer light in a desired direction. In addition to steering the light, PLM  102  can focus the light at a spot (focal point) at a desired distance. 
       FIG. 2  is a side view of an example micromirror like one of micromirrors  104  ( FIG. 1 ). Platform  204  connects to two platform electrodes  212  via platform posts  214 . Post  208  supports mirror  210  above platform  204 . As shown in  FIG. 2 , when a voltage is applied to driving electrode  206  and a reference voltage (e.g. ground) is applied to platform electrodes  212 , an electrostatic force pulls platform  204 , and thus mirror  210 , down. The amount of movement is determined by the applied voltage. In other examples, pixel  202  uses two or more driving electrodes  206  that are individually addressable by driving circuitry (not shown). The applied electrostatic force is proportional to the area of a driving electrodes  206  and platform  204 . Thus, using multiple electrodes the amount of force, and thus the vertical position of mirror  210  can be precisely controlled by selecting the driving electrode  206  or combination of driving electrodes  206 , while applying the same voltage to each selected one of driving electrodes  206 . The phase shift provided by pixel  202  is determined by the vertical positioning of mirror  210 . For example, if a pixel lowers by one-quarter wavelength (¼ λ), light reflected from that pixel will travel an additional one-half wavelength (¼ λ down to the mirror and ¼ λ back) relative to a pixel that is not lowered. In another example, if a pixel lowers by one-eighth wavelength (⅛ λ), light reflected from that pixel will travel an additional one-quarter wavelength (⅛ λ down to the mirror and ⅛ λ back) relative to a pixel that is not lowered. 
       FIG. 3  is a top view of an example LIDAR apparatus  300 . Light source  302  is a laser in this example. In an example, light source  302  provides near infrared laser light. Light source  302  provides light through collimating lens  304  to transmit PLM  306 . Transmit PLM  306  provides a configurable phase pattern to the light that directs the light to target  308 . In the example of  FIG. 3 , target  308  is on the surface of an object  310 , which is an automobile. Light reflected from object  310  is focused by receive PLM  312  to detector  314  through lens  316 . Because the point at which the light is directed by transmit PLM  306  is known, detection of reflected light by detector  314  indicates that an object is at that point. In this example, detector  314  is an avalanche photo diode. Transmit PLM  306  scans the field of view while receive PLM  312  scans the field of view seen by the APD to match the target  308  to which transmit PLM is scanning. This allows example LIDAR apparatus  300  to determine the distance and contour of object  310 . 
     LIDAR apparatus  300  has limitations. For example, each pattern on the PLM corresponds to steering the light beam in a particular direction. A significant amount of time is required for the transmit PLM  306  and receive PLM  312  to change from one pattern to another. For example, if a new pattern&#39;s data load time is 50 μs, and the frame time is 100 ms, then only 2,000 points can be captured, which is a resolution of only ˜65×30. A higher resolution is preferable. In addition, LIDAR scanning of large field-of-view (FOV) is difficult. Scanning an area larger than 60×20 degrees a with 0.1 degree beam width, 10 Hz frame rate requires a PLM update rate of greater than 1 million samples/second. However, the size of the mirrors in the PLM limits the field of view and the wavelength of the light limit the FOV. For a pixel size of about 10μ square using near infrared light, the FOV of current PLM devices is limited to just a few degrees. Receive PLM  312  allows rejection of ambient light by directing light from a narrow angle to the detector. However, scanning a large FOV requires wide-angle optics. Wide angle optics require a small aperture size that limits the signal strength received at detector  314 . 
       FIGS. 4A-D  (collectively “ FIG. 4 ”) are views of a transmit portion  402  of an example LIDAR apparatus  400 .  FIG. 4A  is a top view of transmit portion  402 . As used herein, the terms “top view” and “side view” indicate the relative orientation of the figures and do not denote any other relationship. For example, the “top” or “side” of LIDAR apparatus  400  may be in any of a number of orientations in a particular installation of example LIDAR apparatus  400 . Example LIDAR apparatus  400  includes three light sources: first light source  404 , second light source  406  and third light source  408 . Controller  401  controls the light output of first light source  404 , second light source  406  and third light source  408 . Example LIDAR apparatus  400  includes three light sources in this example but may include two, four, or more light sources, which may be arranged in a one-dimensional or two-dimensional array. In addition, in this example, first light source  404 , second light source  406  and third light source  408  are near-infrared laser diodes but may be other types of light sources, such ultraviolet light sources. First light source  404  provides first light beam  410  through first collimating lens  412  at a first angle of incidence relative to transmit PLM  414 . Transmit PLM  414  is a digital micromirror based PLM in this example. In other examples, transmit PLM  414  is a reflective or transmissive liquid crystal phase light modulator. In accordance with a steering pattern applied to transmit PLM  414  by controller  401 , the first output of transmit PLM  414  in response to first light beam  410  is first modulated light beam  416  having a first output angle of reflection. The first angle of incidence of first light source  404  and the steering pattern on transmit PLM  414  determine the output angle of reflection to the first focal point  411 . In this example, the first angle of incidence directs first modulated light beam  416  to a first focal point  411  on object  450  in first field of view (FOV)  418 . 
     Second light source  406  provides second light beam  420  through second collimating lens  422  at a second angle of incidence relative to transmit PLM  414 . In accordance with a steering pattern applied to transmit PLM  414  by controller  401 , the output of transmit PLM  414  in response to second light beam  420  is second modulated light beam  426  having a second angle of reflection. At any given time, the steering pattern on transmit PLM  414  is constant. Therefore, the difference between the second angle of reflection and the first angle of reflection is determined by the difference between the second angle of incidence and the first angle of incidence. As with the first angle of reflection, the second angle of reflection of second light source  406  and the pattern on transmit PLM  414  determine the second angle of reflection. In this example, the second angle of reflection directs second modulated light beam  426  to a second focal point  421  on object  450  in second FOV  428 . 
     Third light source  408  provides third light beam  430  through third collimating lens  432  at a third angle of incidence relative to transmit PLM  414 . In accordance with a steering pattern applied to transmit PLM  414  by controller  401 , the output of transmit PLM  414  in response to third light beam  430  is third modulated light beam  436  having a third angle of reflection. At any given time, the steering pattern on transmit PLM  414  is constant. Therefore, the difference between the third angle of reflection and the first and second angles of reflection is determined by the difference between the third angle of incidence and the first and second angles of incidence. As with the first and second angles of reflection, the third angle of incidence of third light source  408  and the pattern on transmit PLM  414  determine third angle of reflection. In this example, the third angle of reflection directs third modulated light beam  436  to a third focal point  431  on object  450  in third FOV  438 . In summary, transmit PLM  414  contemporaneously directs light from first light source  404 , second light source  406  and third light source  408  to points in first FOV  418 , second FOV  428  and third FOV  438 , respectively. 
       FIG. 4B  is a view of the fields of view as shown by view line  4 B- 4 B of  FIG. 4A .  FIG. 4B  is a view from the perspective of transmit PLM  414  facing first FOV  418 , second FOV  428  and third FOV  438 . For a given steering pattern on transmit PLM  414 , first light source  404 , second light source  406  and third light source  408  illuminate one point in each of first FOV  418 , second FOV  428  and third FOV  438 , respectively. By changing the steering pattern of transmit PLM  414 , transmit portion  402  scans each FOV. In this example, first scanning points  442 , second scanning points  452  and third scanning points  462  are scanned in a raster scan manner, as illustrated in  FIG. 4B . However, other scanning methods may be used such as random scanning. As shown in  FIG. 4B , in this example, the size of first FOV  418 , second FOV  428  and third FOV  438  is selected so that first FOV  418 , second FOV  428  and third FOV  438  avoid extraneous diffraction orders produced by light diffracting from the steering pattern on transmit PLM  414 . In other examples, the FOVs overlap to provide more accurate, but slower, scanning. In these examples, any extraneous diffraction orders must be corrected after detection. 
       FIG. 4C  is side view of transmit portion  402  of example LIDAR apparatus  400 .  FIG. 4C  is a view looking across the face of transmit PLM  414  from the direction of third light source  408 , which is from view  4 C- 4 C of  FIG. 4A . Third light source  408  blocks the view of first light source  404  and second light source  406  from this perspective. In addition, third collimating lens  432  blocks the view of first collimating lens  412  and second collimating lens  422 . For simplicity, only third light beam  430  and third modulated light beam  436  are shown in  FIG. 4C . As can be seen from  FIG. 4C , third light beam  430  and third modulated light beam  436  are not in the same plane. In this example, this avoids interference of third light source  408  with third modulated light beam  436 . A specific configuration of light sources is shown in this example vis-a-vis transmit PLM  414 . Other examples may use different configurations. In addition, other examples may use two, four or more light sources. 
       FIG. 4D  is a top view of another example transmit portion  405  of another example LIDAR apparatus  403 . In this example apparatus, one light source  407  produces first modulated light beam  416 , second modulated light beam  426  and third modulated light beam  436 . Light source  407  provides light beam  423  through collimating lens  425 . Transmit PLM  414  in this example does not use a single steering pattern, but rather uses three steering patterns. In an example, three different steering patterns would be applied to three different portions of transmit PLM  414 . Three steering patterns are used in this example. However, two, four or more steering patterns may be used. In addition, the example of  FIG. 4D  includes one light source at one angle of incidence. However, using multiple light sources at multiple angles of incidence along with multiple steering patterns applied to transmit PLM  414  multiplies the number of fields of view that can be illuminated contemporaneously. For example, three light sources applied to a transmit PLM having three steering patterns can illuminated nine fields of view contemporaneously. 
     In the example of  FIG. 4D , three steering patterns applied to transmit PLM  414  produce light first modulated light beam  416 , second modulated light beam  426  and third modulated light beam  436 , which illuminate object  450  at first focal point  411 , second focal point  421  and third focal point  431 , respectively, in first FOV  418 , second FOV  428  and third FOV  438 , respectively. The steering pattern scans the fields of view as described above with regard to  FIGS. 4A and 4B . The example of  FIG. 4D  limits the amount of light provided to each focal point to one-third or less of the luminance provided by light source  407  because each steering pattern is applied to one-third or less of the area of transmit PLM  414 . 
       FIGS. 5A and 5B  (collectively “ FIG. 5 ”) are views of a receive portion  502  of example LIDAR apparatus  400  ( FIG. 4 ).  FIG. 5A  shows a top view of receive portion  502 . Controller  501  is like controller  401  ( FIG. 4 ). First detector  504 , second detector  506  and third detector  508  detect light reflecting off an object in first FOV  518 , second FOV  528  and third FOV  538 , respectively. First FOV  518 , second FOV  528  and third FOV  538  correspond to first FOV  418 , second FOV  428  and third FOV  438  ( FIG. 4 ). First focal point  511 , second focal point  521  and third focal point  531  correspond to first focal point  411 , second focal point  421  and third focal point  431  ( FIG. 4 ), respectively. First detector  504  detects first focal point  511  in first FOV  518  illuminated by first light source  404  ( FIG. 4 ). Second detector  506  detects second focal point  521  in second FOV  528  illuminated by second light source  406  ( FIG. 4 ). Third detector  508  detects third focal point  531  in third FOV  538  illuminated by third light source  408  ( FIG. 4 ). Object  550  corresponds to object  450  ( FIG. 4 ) 
     Receive PLM  514  focuses first reflected light beam  516  reflected from object  550  at a first focal point  511  in first FOV  518  as first received light beam  510  onto first detector  504  through first receiving lens  512 . Receive PLM  514  is a digital micromirror based PLM in this example. In other examples, receive PLM  514  is a reflective or transmissive liquid crystal phase light modulator. Controller  501  receives the output of first detector  504  for further processing. First focal point  511  in first FOV  518  corresponds to first focal point  411  in first FOV  418  ( FIG. 4 ). A fourth angle of reflection of first detector  504  and a steering and a focusing pattern on receive PLM  514  provided by controller  501  determine a fourth angle of incidence of the first focal point  511  relative to receive PLM  514 . In an example, the fourth angle of reflection is different from the first angle of incidence to allow positioning of first detector  504  in such a way that first light source  404  ( FIG. 4 ) and first detector  504  do not interfere with each other. Selecting a steering and focusing pattern on receive PLM  514  as provided by controller  501  steers the focus of first reflected light beam  516  to first focal point  511  on object  550 . The first focal point  511  of first reflected light beam  516  is the first focal point  411  to which first modulated light beam  416  ( FIG. 4 ) is directed. As first modulated light  416  ( FIG. 4 ) scans first FOV  418  ( FIG. 4 ), the focus of first reflected light beam  516  scans the same points to which first modulated light  416  ( FIG. 4 ) is directed. In this example, first detector  504  is an avalanche photo diode. If first detector  504  detects light from first light source  404  ( FIG. 4 ) reflected from first focal point  511  of first reflected light beam  516 , this detected light indicates that an object  550  is at that point. Scanning all of first FOV  518  determines the shape and position of object  550  that may be in first FOV  518 . In examples, transmit PLM  414  ( FIG. 4 ) and receive PLM  514  are the same PLM. However, because the pattern on PLM  414 / 514  in this example must both focus the transmit and receive light, an example using one, combined PLM requires positioning of the light sources and detectors in configurations that may not be practicable in certain situations. Using a separate PLM for the receive and transmit sections as in the example of  FIGS. 4 and 5  allows for greater flexibility of positioning components of the LIDAR apparatus. 
     Receive PLM  514  and second receiving lens  522  focus second reflected light beam  526  reflected from object  550  at a second focal point  521  in second FOV  528  as second received light beam  520  to second detector  506 . Controller  501  receives the output of second detector  506  for further processing. Second focal point  521  in second FOV  528  corresponds to second focal point  421  in second FOV  428  ( FIG. 4 ). A fifth angle of reflection of second detector  506  relative to receive PLM  514  and the focusing pattern on receive PLM  514  determine a fifth angle of incidence of the second focal point  521  relative to receive PLM  514 . In an example, the fifth angle of reflection is different from the second angle of incidence to allow positioning of first detector  506  in such a way that first light source  406  ( FIG. 4 ) and first detector  506  do not interfere with each other. The second focal point  521  of second reflected light beam  526  is the second focal point  421  of second FOV  428  to which second modulated light beam  426  ( FIG. 4 ) is directed. At any given time, the steering pattern on receive PLM  514  is constant. Therefore, the difference between the fifth angle of incidence and the fourth angle of incidence is determined by difference between the fifth angle of reflection and the fourth angle of refection. As with the fourth angle of reflection, the fifth angle of reflection of second detector  506  and the pattern on receive PLM  514  determines fifth angle of incidence. As second modulated light beam  426  ( FIG. 4 ) scans second FOV  428 , the second focal point  521  of second reflected light bean  526  scans the same second focal point  421  to which second modulated light beam  426  ( FIG. 4 ) is directed. In this example, second detector  506  is an avalanche photo diode. If second detector  506  detects light from second light source  406  ( FIG. 4 ) reflected from object  550  at the second focal point  521 , this detected light indicates that object  550  is at that point. Scanning all of second FOV  528  determines the shape and position of an object that may be in second FOV  528 . 
     Receive PLM  514  and third receiving lens  532  focus third reflected light beam  536  reflected from an object  550  at a third focal point  531  in third FOV  538  as third received light beam  530  to third detector  508 . Controller  501  receives the output of third detector  508  for further processing. Third focal point  531  in third FOV  538  corresponds to third focal point  431  in third FOV  438  ( FIG. 4 ). A sixth angle of incidence of third detector  508  and the steering and focusing pattern on receive PLM  514  provided by controller  501  determine a sixth angle of reflection of the third focal point  531  relative to receive PLM  514 . In an example, the sixth angle of reflection is different from the third angle of incidence to allow positioning of third detector  508  in such a way that third light source  408  ( FIG. 4 ) and third detector  508  do not interfere with each other. At any given time, the steering pattern on receive PLM  514  is constant. Therefore, the difference between the sixth angle of incidence and the fourth and fifth angles of incidence is determined by difference between the sixth angle of reflection and the fourth and fifth angles of reflection. As with the fourth and fifth angles of incidence, the angle of reflection of third detector  508  and the pattern on receive PLM  514  determine sixth angle of incidence. The third focal point  531  of third reflected light beam  536  is the third focal point  431  of third FOV  438  to which third modulated light beam  436  ( FIG. 4 ) is directed. As third modulated light beam  436  ( FIG. 4 ) scans third FOV  438 , the third focal point  531  of first reflected light beam  516  scans the same third focal point  431  ( FIG. 4 ) to which third modulated light beam  436  ( FIG. 4 ) is directed. In this example, third detector  508  is an avalanche photo diode. If third detector  508  detects light from third light source  408  ( FIG. 4 ) reflected from an object  550  at the third focal point  531 , this detected light indicates that object  550  is at that point. Scanning all of third FOV  538  determines the shape and position of an object that may be in third FOV  538 . In summary, example LIDAR apparatus  400  ( FIG. 4 ) scans three fields of view contemporaneously. That is, the data rate of the PLM is reduced by the number of tiled FOVs. Thus, example LIDAR apparatus  400  ( FIG. 4 ) scans the same area three times faster than a LIDAR apparatus using one light source/detector pair for a given PLM steering pattern loading rate. In addition, because each field of view scanned is a smaller portion of the overall field of view, limitations to the field of view size caused by limitations to the steering angle of the PLMs are overcome. In another example, the tiled FOVs can overlap to provide multiple data for each point and thus provide better coverage. In another example, the FOVs can be tiled in two dimensions. That is, fields of view can be on one plane or on multiple planes with respect to the LIDAR apparatus. 
       FIG. 5B  is side view of receive portion  502  of example LIDAR apparatus  400 .  FIG. 5B  is view  5 B- 5 B of  FIG. 5A  looking across the face of receive PLM  514  from the direction of third detector  508 . Third detector  508  blocks the view of first detector  504  and second detector  506  from this perspective. In addition, third receiving lens  532  blocks the view of first receiving lens  512  and second receiving lens  522 . For simplicity, only third received light beam  530  and third reflected light beam  536  are shown in  FIG. 5B . As shown in  FIG. 5B , third received light beam  530  and third reflected light beam  536  are not in the same plane. In this example, this avoids interference of third detector  508  with third reflected light beam  536 . A specific configuration of light sources is shown in this example vis-a-vis receive PLM  514 . Other examples may use different configurations. In addition, other examples may use two, four or more detectors. In another example, the FOV or tiled FOVs as in the example of  FIGS. 4 and 5 , can be expanded by illuminating with a diverging laser beam. Examples of using divergent light beams are described in Makowski, et al., “Simple Holographic Projection in Color,” Opt. Express 20, 22 (October 2012) and Maimone et al., “Holographic Near-Eye Displays for Virtual and Augmented Reality,” ACM Transactions on Graphics, Vol. 36, No. 4, Article 85 (July 2017), which are hereby incorporated by reference herein in their entirety. 
       FIG. 6  is a diagram of another example LIDAR apparatus  600 . Light source  602  is a laser in this example. In an example, light source  602  provides near infrared laser light. Light source  602  provides divergent light beam  603  to transmit PLM  606 , which provides a modulated light beam  605  in response to the divergent light beam  603  output from light source  602 . Rather than use a collimating lens as in the example of  FIG. 3 , transmit PLM  606  provides a configurable phase pattern to the light that both directs modulated light beam  605  to target  608  and provides an optical power or curvature that focuses the divergent light beam  603  from light source  602  to focus on focal point  611 . Thus, by using a phase pattern with an optical power to focus divergent light from light source  602 , example LIDAR apparatus  600  eliminates the additional expense and manufacturing complication of using a collimating lens. In the example of  FIG. 6 , focal point  611  is on the surface of an object  610 , which is an automobile. Receive PLM  612  includes a pattern that focuses light reflected from object  610  at the focal point  611  onto detector  614 . In this example, the pattern on receive PLM  612  includes both a steering function and an optical power or curvature that focuses the light directly onto detector  614 . Thus, an additional lens that focuses and “de-collimates” light from focal point  611  on to detector  614  is not necessary. Transmit PLM  606  and receive PLM  612  are a digital micromirror based PLM in this example. In other examples, either or both of transmit PLM  606  and receive PLM  612  are reflective or transmissive liquid crystal phase light modulators. Controller  601  controls the patterns on transmit PLM  606  and receive PLM  612 , and controls the light provided by light source  602  and receives the detected light signal from detector  614 . Because controller  601  knows the point at which transmit PLM  606  directs the light from light source  602 , detection of reflected light by detector  614  indicates that an object is at that point. In this example, detector  614  is an avalanche photo diode. Transmit PLM  606  scans the field of view while receive PLM  612  is adjusted to focus on the focal point  611  to which transmit PLM  606  is scanning. This allows example LIDAR apparatus  600  to determine the distance and contour of object  610 . In another example, with a configuration using multiple light sources and detectors like that of  FIGS. 4 and 5 , the light sources can provide divergent light and the PLMs can provide an optical power as with the example of  FIG. 6 , thus eliminating the need for collimating lenses at the output of the light sources and focusing lenses at the input of the detectors. 
       FIG. 7  is a flow diagram of an example method  700 . Step  702  is directing a first light beam from a first light source to a first input of a phase light modulator. A light source such as first light source  404  ( FIG. 4 ) provides the first light beam. The phase light modulator is like transmit PLM  414  ( FIG. 4 ). Step  704  is modulating the first light beam using the phase light modulator to provide a first modulated light beam directed to a first field of view. The first modulated light beam is like modulated first modulated light beam  416  ( FIG. 4 ). The first field of view is like first FOV  418  ( FIG. 4 ). Step  706  is directing a second light beam from a second light source to the phase light modulator. A light source such as second light source  406  ( FIG. 4 ) provides the second light beam. Step  708  is modulating the second light beam using the phase light modulator to provide a second modulated light beam directed to a second field of view. The second modulated light beam is like second modulated light beam  426  ( FIG. 4 ). The second field of view is like second FOV  428  ( FIG. 4 ). Step  710  is detecting the first light beam as reflected from the first field of view using a first light detector. The first light detector is like first detector  504  ( FIG. 5 ). Step  712  is detecting the second light beam as reflected from the second field of view using a second light detector. The second light detector is light second detector  506  ( FIG. 5 ). 
       FIG. 8  is a flow diagram of another example method  800 . Step  802  is directing a divergent light beam from a light source to a phase light modulator. The divergent light source is like light source  602  ( FIG. 6 ). The phase light modulator is like transmit PLM  606 . Step  804  is modulating the divergent light beam using the phase light modulator to provide a modulated output beam directed to a field of view. The field of view is like target  608  ( FIG. 6 ). Step  806  is detecting the light modulated output as reflected from the field of view using a light detector. The light detector is like detector  614  ( FIG. 6 ). 
     Modifications are possible in the described examples, and other examples are possible, within the scope of the claims.