fig1 illustrates an exemplary embodiment of a measurement and display system 100 , which measures or detects some feature beneath a surface ( e . g ., skin surface ) and displays information onto the surface indicative of the measurement . the system includes an imaging laser 102 , which provides a coherent laser light output in an appropriate frequency range for imaging a feature beneath the surface , for example , the vascular system 113 in a patient &# 39 ; s forearm 130 . the system also includes a display laser 104 , which provides a coherent laser light output in an appropriate frequency range for display of an image , typically in a visible range of the electromagnetic spectrum ( i . e ., having a wavelength between about 400 and 700 nm ). the imaging laser 102 is generally used to obtain the location of the vessels of a patient , while the display laser 104 is generally used to indicate to a medical practitioner or user of the system 100 the location of the imaged vessels . in some embodiments , the location of the imaged vessels is substantially overlaid in a projection by display laser 104 onto the body of a patient so that the projected image of the vessels is outlined onto the surface of the patient &# 39 ; s body ( skin ) and generally maps to the actual location of the vessels below the surface . in this way , a practitioner ( surgeon , blood technician , emergency injection operator , etc .) can easily locate the vessels below the surface of the skin and access the vessels as necessary , with the desired accuracy , to accomplish their task . as will be explained below , the present system can also be used to detect and project information about temperature , oxygen content , and other measurable features . one or more rotating mirrors 106 are used to direct the light output of the imaging and display lasers , 102 and 104 respectively , onto the desired location of the patient &# 39 ; s body . note that the rotating mirrors 106 can be augmented with other optical components such as other lenses , gratings , optical elements , apertures , gates , relays , mirrors , including flat , concave , convex , or combinations thereof to achieve the desired guidance of the light onto and collection of light from the patient &# 39 ; s body . the illustration is intended to depict an optical assembly generally , including a combination of the above types of components or others as would be appreciated by those skilled in the art . this can include focusing or defocusing elements , filters , amplifiers , and other optical components as called for in a particular design of the system 100 . the overall result of the one or more optical elements is an optical assembly that provides an imaging beam 103 by which the patient is irradiated and which is incident upon a region of interest (“ roi ”) 110 of the patient &# 39 ; s body . one method of achieving the transmission of the incident beam over a rectangular roi 110 on the skin is by means of a pair of mirrors which rotate in orthogonal planes and which redirect the laser beam in a controlled raster - scan pattern over an x and y coordinate axis projected onto the skin as will be described below . the imaging beam 103 operates on and interacts with the patient &# 39 ; s vasculature and / or blood and provides the imaging of the vascular system in the rot 110 . in addition , the optical assembly ( or a separate optical assembly if the aging and display paths are treated separately ) carries a display beam 105 that is used to display the relevant image of the vascular system of the roi 110 . in some embodiments , the display beam 105 and imaging beam 103 propagate along parallel but spatially distinct optical paths . in other embodiments both the display and imaging beams 105 , 103 propagate substantially along the same optical path and use shared optical components . in operation , the imaging beam 103 is incident upon a rot 110 on the patient &# 39 ; s body as mentioned above . the light from the imaging beam 103 penetrates the patients skin and outer tissues so as to be incident on and interact with the patient &# 39 ; s vascular system and / or the blood within the patient &# 39 ; s vascular system in the roi 110 . the light from imaging beam 103 is then redirected , reflected , refracted , and otherwise sent upon its interaction with the patient &# 39 ; s vascular system and / or blood in the roi 110 back out from the patient &# 39 ; s body in what we refer to herein as the “ reflected imaging beam ” 107 . in one embodiment , near - infrared light is used which is known to have a higher absorption coefficient by blood than by other tissue . it should be appreciated that while reflection and absorption is one way of forming the reflected imaging beam 107 , other optical and electromagnetic , chemical , and mechanical effects influencing the incident imaging beam 103 can also contribute to or influence the light forming the reflected imaging beam 107 . the intensity of the reflected beam is a function of the absorption and scattering of the incident beam by the tissue and blood upon which it is incident at each location in the roi as the incident beam is controllably scanned across the roi . the reflected imaging beam 107 is sensed by a photocell 108 . more specifically , light forming the reflected imaging beam 107 is collected by some optical assembly that can include a lens , collator , filter , modulator , mirror , prism shaped collector , and other optical elements for delivery to a photocell 108 , directly or indirectly . the photocell 108 can be of a number of sizes and configurations so that it can sense an intensity , power , amplitude , or other quantifiable characteristic of the reflected imaging beam 107 . photocell 108 may include an array or grid of photo - sensitive elements , e . g . arranged in two dimensions such as x - y cartesian dimensions to form an output signal 109 . when measured by a photodetector as a function of time ( which can be directly related to the position of the incident beam in the roi as it is scanned across the region ), the signal intensity from the reflected beam can be used to recreate a map of the tissue reflection and absorption as a function of location in the roi . note that in some embodiments , the use of a line - source or spot / pencil beam source of light can be accomplished where the line or pencil beam sources are scanned with a mechanical or opto - electro - mechanical scanner so as to cover the surface of the roi by translating the location of the spot or line beam over the surface of the roi . in turn , the photocell output 109 includes one or more signals that can be used to modulate the display laser 104 and hence modulate display beam 105 . it can now be seen that the display portion of the system 100 is modulated by the imaging portion of the system 100 such that the images projected by the display portion of the system 100 can include information derived from the imaging portion of the system 100 . in particular , in some embodiments , the display portion of the system 100 can be made to project an image of or light information representative of the blood vessels in the roi 110 . even more particularly , a visible light image can be projected onto the surface of the patient &# 39 ; s body that is effectively a representation that is spatially and visually matched to or corresponding to the blood vasculature beneath the ski in the roi 110 , where a light - coded portion of the projected image corresponds to an underlying vessel located directly beneath the light - coded portion of the projected image . in one embodiment , the intensity of the projected display light beam 105 is modulated to spatially indicate on the patient &# 39 ; s body in the roi 110 the location of an underlying vein ( or vessel that is to be injected or otherwise used in a medical procedure such as insertion of an iv line . in another embodiment , the inverse image ( the negative ) is possible , where the path and location of a blood vessel is darkened relative to the surrounding portion of the roi 110 . in yet another embodiment , a color - coding is used in a multi - color modulated display system to indicate various features of the vascular system being imaged . for example , characteristics of the vascular system including temperature , flow rate , oxygen level diameter , pressure , proximity to the surface , and other characteristics of the vessels and vascular network can be indicated by proper modulation of the imaging portion of the system 100 . as to the design of the rotating mirror assembly 106 , this allows single line or planar scanning of a region of interest over a finite surface of the patient &# 39 ; s body so that a single and relatively simple laser can be used for the imaging laser 102 . in the same way , a relatively simple source can be used for the display laser 104 so that it can be used to cover and illuminate and form a projection onto a finite area of the roi 110 of the patient &# 39 ; s body . the operation of the rotating mirror can be controlled so that its speed of rotation allows a pulsed or continuous application of the laser sources 102 , 104 , to achieve a controlled result on the patient &# 39 ; s body in the roi 110 . in one embodiment , the image and display lasers use the same rotating mirror assembly to minimize the number of parts and to ensure perfect collocation of the two laser beams on the roi . the display laser 102 itself can also be made of one or more parts so as to project an image ( e . g ., a two - dimensional image ) or representation upon the patient &# 39 ; s body &# 39 ; s roi 110 . the display portion of the system 100 can be specifically built to include a microdisplay , digital projection elements , micro - reflectors , etc . that are controllable and addressable to form two - dimensional light output in display beam 105 that is indicative of the vascular structure being imaged . the modulation of the display portion of the system 100 can be amplitude modulation with a resulting dark - to - bright modulation of specific areas of the illuminated image corresponding to characteristics of the vascular system in the patient &# 39 ; s body in the roi 110 . in some embodiments , the system may comprise a low - power and hand - held apparatus within a compact housing 101 . this application can be used in the field for military ( e . g ., combat ) or civilian ( e . g ., emergency services ) operations to locate blood vessels below the surface of a patient &# 39 ; s skin under various conditions . the system 100 can be portable , light - weight and powered by a dc power source such as a battery . a visible projected cross hair marker 111 or other marking can indicate to a user a location of interest on the surface of the skin ( or other surface ). for example , this marker can be projected on a location of a vein for the purpose of inserting a needle or catheter at this location of interest . a region of interest roi 110 can be a substantially two - dimensional surface of a patient &# 39 ; s body having any of several shapes and sizes . for example , roi 110 can extend in two cartesian dimensions along the surface of a patient &# 39 ; s body or skin , covering a substantially rectangular patch or aperture of said body or skin . also , roi 110 can extend in other coordinate systems such as a cylindrical or polar coordinate system and cover a substantially circular patch or aperture of said body or skin . of course , in a real body , the surface covered by the roi 110 can be generally planar ( e . g ., covering a small region of a human &# 39 ; s abdomen ) or can be non - planar and including topology that follows the surface of the body . in some applications , the present system can be used to determine spatial profiles of thermal or chemical composition maps beneath a surface , e . g ., the surface of a patient &# 39 ; s skin . the information measured can be illustratively depicted or processed then displayed onto the surface , typically in a visible depiction overlaid over the region where the measurement itself is made . one such application specifically would be for oximetry . as described above , blood provides a measurable medium due to the mechanical , optical and chemical composition thereof , and due to the contrast between the composition and nature of blood ( including hemoglobin ) and surrounding tissue . oximetry measurements can be made based on infrared and red light wavelength absorption characteristics of oxygenated hemoglobin in the blood and / or deoxygenated hemoglobin in the blood . deoxygenated hemoglobin absorbs red wavelengths ( 600 - 750 nm ) more than oxygenated hemoglobin or other tissues . oxygenated hemoglobin absorbs infrared wavelengths ( 850 - 1000 nm ) more than other substances do . the ratio of infrared to red absorption in arterial blood correlates to the ratio of oxygenated to deoxygenated hemoglobin . in practice , these measurements can be used with lookup tables to determine an oxygen saturation or relative oxygenation level of the blood . this effect may be due to the chemical , mechanical , optical , electro - optical or other physical characteristics of the blood , and is intended here as an illustrative example of the present concept rather than a limiting discussion of the same . those skilled in the art may appreciate the generalization of the instant description to similar or analogous uses in such or other materials in living or non - living organisms and subjects . fig2 illustrates a simplified plot 200 showing absorption 210 as a function of wavelength 220 . the exemplary absorption characteristics of oxygenated hemoglobin ( hbo2 ) 230 compared to deoxygenated hemoglobin ( hb ) 240 illustrate how quantitative determinations can be made for detecting vessels carrying hb and hbo2 beneath the skin . for example , a wavelength 202 of 660 nm would be suitable for determining the presence of hb while a wavelength 204 of 910 nm would be suitable for determining the presence of hbo2 . our imaging wavelength can detect one or both of these and our display wavelength can project a graphical representation of the vasculature on the surface of the skin substantially congruent to the physical location at which each of these things has been detected . furthermore , a quantitative representation can be made so that the projected or displayed information shows the oxygenation level where this quantity has been measured . the amount of oxygen can be shown by a color coded projection or by projection of characters ( e . g ., numbers ) onto the surface of the skin of the patient showing the same . in an example , the wavelength interacting with hb is between 500 and 800 nm , optimally about 660 nm and a second wavelength interacting with hbo2 is between 800 and 1100 nm , optimally about 910 nm . in an aspect , a combined laser path imaging system as described herein can be used to measure the ratio of absorption of infrared and red laser light at given locations in a region of interest , for example , on a point - by - point basis . the region of interest can be an antecubital fossa where several large blood vessels are present . current vessel location systems require contact measurement apparatus , typically using the transmission of led light in two selected wavelengths to calculate the oxygen saturation . however , the present system allows for a multi - wavelength compact ( and sometimes portable or even hand held ) device that can operate without contact to efficiently locate and display features below the skin surface . again , this system and technique can be generalized to other surfaces such as walls or objects concealing subsurface features . fig3 illustrates an exemplary system 300 for detecting and displaying measurements relating to a subsurface characteristic such as blood oxygenation information ( oxymetry ), which can be used to determine the state of hemoglobin as a function of location in a region of interest . this information can be of clinical value and can be used in imaging or other diagnostic and therapeutic procedures . in this and other embodiments , computer technology , generally including processing hardware , software , firmware or other machine - readable instructions can be utilized to control the operation of the system . those skilled in the art will understand various implementations of the present system that include such processing hardware and program instructions , some or all of which can be procured from components known in the art , but which are creatively now coupled and programmed and arranged as presently described . uses of such technology can be made in the user interface designs for the present systems . for example , to allow entry of information and other desired settings and configurations of the system . then , to allow for reading or receiving output from the system as needed . interfacing the system to other machines is contemplated , including connecting the system through appropriate connectors and interface units to computer data networks , database systems , healthcare provider computer networks , insurance data systems , and other processing systems and networks . in addition , signal processing and data acquisition and filtering and related operations can be achieved through similar computerized functionality as would be known to those skilled in the art in view of the present disclosure . hence , generally , a signal processing unit 302 is provided to achieve the above functions . note that this functionality can be contained in a single general purpose or special purpose hardware or computer chip or processing circuit , or it may be divided among a number of circuit components and processors that cooperatively achieve the same end . the other elements of system 300 are similar to that described above . for example , a plurality of laser sources operating at respective wavelengths are provided for the present imaging and display functions , including to investigate the presence and location of oxygen rich and oxygen poor hemoglobin in blood vessels beneath the skin ( using , e . g ., red laser 310 , display visible laser 330 and infra red ( ir ) laser 320 ). these laser beams 322 are scanned across a region of interest , the imaging ( or sensing ) beams of which penetrate the skin surface to investigate what lies below , but the display laser beam 332 scans over the corresponding skin locations to show the user where the items of interest lie beneath . as mentioned , rotating mirrors 306 , which generally mean a scanning optical assembly , are provided to scan the beams across the region of interest . collector 308 acts to collect light in the system and direct it to photocell 304 . more than three beams of various wavelengths may be used to further detect or discriminate sensed objects beneath the surface of the skin if desired by extending the present concept . fig4 illustrates another embodiment of a system 400 for detecting and displaying information based on sensing the same beneath the surface of an object but projecting the same onto the surface of the object . a plurality , e . g ., three , laser beams are provided by respective sources 402 , 404 and 406 . the beams are directed by a common beam splitter or combiner 408 to pass through collector 440 onto rotating mirrors ( or optical assembly ) 430 and then to the region of interest 450 . the rotating optical assembly 430 may be substituted with a solid state scanning or modulating assembly . in this embodiment the sensing ( imaging ) and display laser beams ( from sources 404 and 402 respectively ) are collinear and travel substantially along a common path or parallel pathway towards the region of interest 450 . the scattered or retroreflected portion of the sensing beam returns to the rotating optical assembly 430 and is reflected at least in part by the collector 440 towards the photocell 420 . signal processing of the collected signal from photocell 420 is provided to signal processing unit 410 or other digital data units as discussed above . in addition to that described previously , the present system can be used to accomplish pulse oximetry and improve the system &# 39 ; s signal to noise ratio and eliminate or reduce background signals from the detected absorption signal . the system can be used to filter background absorption signals from the venous blood and other tissues . by tracking the time dependent absorption signal , the system can sense periodic peaks in absorption due to pulmonary pulsation of blood into the organ of interest . periodic rise and fall of the intensity of the absorption signal can be used to define a dc absorption floor where background tissue and venous blood are responsible for the absorbed light rather than arterial blood . the system can then subtract the background absorption signal from the measured absorption signal to eliminate the noise of non - arterial blood absorption to yield a more accurate measurement of the arterial blood absorption characteristics in a location of interest . pulse oximetry also permits measurement of heart rate as it affects the periodic flow of hemoglobin in the region of interest through measurements of the red and / or infrared absorption signals . in another aspect , thermometry of tissues can be performed using the above system and techniques . specifically , a temperature map as a function of space or space and time can be achieved . in fact , using the same architecture described herein , all of the above measurements and a display of the same can be made in a patient . fig5 illustrates a simplified raster scanning pattern 510 over a region of interest ( e . g ., skin ) providing pulse oximetry ( po ) 522 , heart rate ( hr ) 524 and temperature ( t ) 526 at each point in the region of interest . it should be appreciated that the overall operation of the present imaging and display systems can be controlled by the construction of the system and by the method for applying the system to the patient &# 39 ; s body . for example , the overall power and intensity of the imaging beam and the optical wavelengths used in the imaging portion of the system can affect the physical characteristics to which the system and imaging light responds . for example , using other wavelengths , e . g ., infrared light , or near - infrared light , to image the body can provide deeper penetration into the body depending on the application and the type of tissue intervening between the light source and the feature being detected . it should also be appreciated that the wavelength of the imaging and the display light beams do not have to be the same . for example , the imaging light may be in the infrared while the display light may be in the visible range of the electromagnetic spectrum , allowing plain - sight observation of the displayed image projected onto the roi . auxiliary features and functions can be microprocessor controlled and can include the ability to control the intensity of the imaging and the display portions of the system . the present system and methods can be applied to more than just imaging of veins , arteries , and vessels in a human or animal body . but with proper selection of inking light source power and wavelength and system design the system can image piping and vessels and flow paths and other features hidden from view . for example , for inspection of circuit boards , fluid pipes , wear on parts , or other thermal or corrosive environments best imaged with ultraviolet (“ uv ”) or infrared (“ ir ”) or other light sources . a light source optimized in frequency and other characteristics to image the feature or object disposed below the skin or skin and subcutaneous fat layers or other tissue can be used . in addition , there can be safety and architectural and manufacturing applications of the present systems and features . in addition to those already discussed such as iv and central line placement , some specific applications which the present system can be adapted for include : infrared (“ ir ”) spectroscopy for chemical identification and blood analysis , for glucose and metabolic monitoring , for treatment of bleeding patients or those having internal bleeding , intraoperative use to avoid unwanted cutting of blood vessels during surgery , dermatological use for assessing ulcer vascularization and other possible uses of ir or uv signal from the skin to assess melanoma , differentiate malignant / benign , assess skin health from sun damage , deeper thermal imaging of sinuses in suspected sinusitis to assess for blood , visualizing varicosities and other telangiectasia of the venous system . in addition , the system could be adapted for use in biometric security applications such as personal identification and secure access applications where a unique or detectable blood vessel or pattern of blood vessels or other biometric characteristic is sensed and indicated . numerous other embodiments , modifications and extensions to the present disclosure are intended to be covered by the scope of the present inventions as claimed below . this includes implementation details and features that would be apparent to those skilled in the art upon review of the present disclosure and appreciation of the concepts and illustrative embodiments provided herein .
the present disclosure provides systems and methods for imaging and display of subsurface features of a region of interest such as a portion of a body of a patient . a first imaging portion of the system is used to cause an interaction of an imaging beam with an underlying feature of a region of interest . a retro - reflected or returned portion of said imaging beam is detected by a detector which then provides an output to control a display portion of the system for displaying an image corresponding to that which was detected . the system can be used for guiding or assisting clinical or industrial operations or for diagnosis of medical conditions and other uses within medicine , industry and others .