Large area marking device and method for printing

[0002] This application is related to U.S. application Ser. No. 10/346,148, filed Jan. 16, 2003, in the names of David L. Patton et al and entitled, “Printing and Apparatus For Printing An Image on a Selected Surface.”

[0003] This invention is directed to printing apparatus and method for forming an image over a large surface area or walkway such as driveways, fields and/or decks or patios.

[0004] This invention generally relates to a marking apparatus and methods and more particularly relates to an apparatus and method for marking a large surface with multiple colors.

[0005] It is often desirable to form color images on a large area. For example, children love to draw and write with colored chalk on a driveway. Similarly to drawing with a crayon on a blank piece of paper the child creates drawings, but does not usually have the ability to draw detailed animals, cartoon characters, scenes, and the like. Children like to color in coloring books and print images using a desktop inkjet printer because they can create detailed drawings that are in full color. These activities are fun, and the child does not need the skills of an artist to produce colorful graphic images. When the child attempts to draw the image manually on a surface such as a driveway, the result may be less than satisfactory. Therefore, it is desirable to provide a marking device capable of forming more pleasing images on a large surface such as a driveway.

[0006] U.S. Pat. Nos. 5,446,559 and 6,062,686 disclose devices that are designed to print on a small smooth surface such as a sheet of paper on a table or desktop. Because of their compact construction, these so-called handheld devices are not burdened by the size and weight of conventional devices that perform similar functions, such as desktop and large format printers. Furthermore, these handheld devices offer superior flexibility in printing and can be used with over sized media. For example, such handheld devices can print on media that is much larger than used in a desktop printer.

[0007] Despite such positive attributes of these handheld devices such as being compact, other less desirable attributes still remain. For example, these handheld devices still require the attention and labor of the user to manually sweep them over an appropriate medium to produce printing on the medium. They are limited in size to a medium that is the size of a sheet of paper or a poster. They are not equipped to print on a rough surface such as asphalt or concrete. To overcome the problems of conveying a hand held device over the surface to be printed a drive mechanism was added. Unlike a desktop printer, the drive mechanism contacts the surface being printed. This creates the problem of contacting the area that has just be printed and damaging the image. In small format printers and printers that are printing several lines of text this is not a problem, but it is a problem for a device printing a large area with a continuous image.

[0008] Charles Manning in U.S. Pat. Nos. 6,299,934 and 6,074,693 discloses a global positioning system for controlling a paint spraying system used to apply paint to a large surface such as a road. The systems described in these patents may be suited for locating a paint sprayer used for painting lines on a road to within a few feet, but GPS systems do not possess the positioning precision required for printing an image. Moreover, the paint-spraying device described by Manning does not have the ability to deliver a marking medium to the marking surface with the amount and with the accuracy necessary to form a desirable image.

[0009] Therefore, there has been a long-felt need to provide an apparatus and method for suitably marking a large area in a manner which automatically accurately determines the size of the large area to be printed, the distance to the surface and quickly, yet precisely, applies a marking medium uniformly to predetermined portions of the surface and can provide multiple color marking to the surface wherein the surface comprises large surface areas of pavement, wood or other structural composites, or concrete, asphalt, brick, grass or laid carpeting collectively hereinafter referred to as a “walkway,” even though cars or other vehicles may also be driven over same.

[0010] A method and apparatus for conveying a portable printing mechanism over a large surface area such as a walkway having a printing means for forming indicia on the surface area is described.

[0011] In accordance with a first aspect of the invention, there is provided an apparatus for printing an image on a large surface area or walkway, the apparatus comprising a marking engine responsive to digital signals representing an image for imagewise marking the surface with a color marking solution; i.e. dye or pigment of ink or paint that is in solution or suspension in a liquid, to form a visible image on the surface during an image recording mode; a self-propelled and automatically steered vehicle that supports the marking engine and includes a drive that engages the surface at plural locations for moving the marking engine along the surface. It is preferred to provide the marking engine so that it is located outboard of an area defined by lines connecting the plural locations so that during operation of the marking engine for imagewise marking during the image recording mode the drive does not engage areas of the surface that have been previously imagewise marked and the drive providing movement of the marking engine to position the marking engine at substantially all points to be marked in the area.

[0012] In accordance with a second aspect of the invention, there is provided a method for printing an image on a large surface area or walkway, the method comprising imagewise marking the surface with a color marking solution to form a visible image on the surface during an image recording mode of a marking engine that is responsive to digital image signals representing the visible image to be printed; automatically steering a vehicle that supports the marking engine and which includes a drive that engages the surface at plural locations and moving the marking engine relative to the surface, the marking engine being located outboard of an area defined by lines connecting the plural locations so that during operation of the marking engine for imagewise marking during the image recording mode the drive does not engage areas of the surface that have been previously imagewise marked and the drive providing movement of the marking engine to position the marking engine at substantially all points to be marked in the area.

[0013] In the preferred embodiment the invention comprises a printing assembly including a housing, a drive and steering mechanism, a power supply, a printer, logic and control unit, and a communications device. The portable printing mechanism can be electronically guided by a removable Erasable Programmable Read Only Memory (EPROM) located in the logic and control unit or it can be guided by transmissions from a remote control device. Alternately, the portable printing mechanism can optically follow a line manually drawn on the driveway or other large surface area.

[0014] The portable printing mechanism maps the area to be printed, determines where within the area the indicia is to be formed and the initial starting position, maintains the correct distance between the print head and the surface area to be printed, and maintains the correct spacing of the lines being printed while the indicia is formed.

[0015] While the specification concludes with claims particularly pointing-out and distinctly claiming the subject matter of the present invention, it is believed the invention will be better understood from the following description when taken in conjunction with the accompanying drawings wherein:

[0016] FIG. 1 is a view in elevation of one embodiment of the present invention showing an apparatus for printing on a large surface area made in accordance with the present invention;

[0017] FIGS. 2 and 3 are top plan views of the apparatus of FIG. 1.

[0018] FIG. 4 is a view in elevation of a portion of the apparatus of FIG. 1 and showing one embodiment of the present invention showing a sensor comprising a laser system for measuring distance to a surface from the print head;

[0019] FIG. 5 is a view in elevation similar to that of FIG. 4 but illustrating another embodiment of the present invention showing a sensor comprising a mechanical follower for measuring distance to the surface from the print head for use in the apparatus of the invention;

[0020] FIG. 6 is a fragmentary view showing a multiple color print head forming a part of the apparatus of FIG. 1;

[0021] FIG. 7 is a cross-sectional view of the multiple color print head of FIG. 6 as taken along line 7—7 of FIG. 6;

[0022] FIG. 8 is an enlarged view of a nozzle of the print head of FIGS. 6 and 7;

[0023] FIG. 9 is a schematic drawing on a large surface area or walkway with an image formed thereon by the apparatus illustrated in FIG. 1;

[0024] FIG. 10 is a schematic of an input panel of the apparatus illustrated in FIG. 1.

[0025] FIGS. 11, 11a, 11band 11care a logic flowchart of a process for mapping an image onto a large surface area or walkway in accordance with the invention;

[0026] FIG. 12 is a schematic drawing on a large surface area or walkway with an image formed by use of a handheld marker thereon made in accordance with another embodiment of the invention;

[0027] FIG. 13 is the schematic drawing of FIG. 12 completed by the apparatus illustrated in FIG. 1;

[0028] FIG. 14 is a schematic drawing on the large surface area or walkway of FIG. 9 with an image formed in accordance with an aspect of the invention by use of a remote control device;

[0029] FIG. 15 is a schematic drawing on a large surface area or walkway with an image formed thereon by use of a laser beam and the apparatus of FIG. 1; and

[0030] FIGS. 16 and 17 are schematic drawings on a large surface area or walkway such as a deck being painted using the apparatus of FIG. 1.

[0031] The invention will be described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

[0032] Referring to FIGS. 1, 2 and 3 apparatus 10 is a device for printing on a large surface area or walkway 100 such as a driveway and other large surface areas suited for walking upon or driving a vehicle upon as referred to above (See FIG. 9). Apparatus 10 is a wheeled vehicle that includes a propulsion assembly 15 including a set of two drive wheels 18aand 18beach with an encoder 19aand 19b, and stepper motors 20aand 20bmounted on a frame 22. Apparatus 10 also comprises a marking engine 23 with a thermo-mechanically activated DOD (Drop on Demand) print head 24, which may be a piezoelectric inkjet print head of the type disclosed in commonly assigned U.S. Pat. No. 6,295,737. Other types of inkjet print heads may also be used including thermally actuated inkjet print heads and continuous inkjet print heads.

[0033] Marking engine 23 is mounted on a sliding or rotating arm 25 having an arm positioner 26. Apparatus 10 further comprises a steerable wheel 27, a steering control 28, a power supply 30, a logic and control unit 35, a communications device 40, sensors 42aand 42b, guide finger 43 and reservoirs 45a, 45b, 45cand 45d. In this embodiment four reservoirs are shown however there may be more or fewer reservoirs. Reservoirs 45a, 45b, 45cand 45dcontain marking solutions 50a, 50b, 50c, and 50dfor example, cyan, magenta, yellow and white marking solutions, respectively. In the present invention, marking solutions can be inks, dyes, paint, or pigments etc., and can form a permanent or temporary visible image. It is understood that any color or combination of colors may be used to form an image as required. Additional reservoirs and print stations may be provided for printing spot colors particularly suited for coloration of logos.

[0034] The apparatus 10 is controlled by logic and control unit 35 that includes a microprocessor and which receives instructions from various sources such as from an input panel 37, from an internal memory source (not shown), from the communication device 40, from the sensors 42aand 42b, from guide finger 43 or from an Erasable Programmable Read Only Memory (EPROM) 55, which can be inserted into the Erasable Programmable Read Only Memory (EPROM) slot 60. Other types of memory such as floppy disks, CD, CD-R, DVD, Picture Disc, memory sticks, tape, etc. may be used. The logic and control unit 35 uses instructions from the aforementioned sources to control the marking engine 23, the propulsion assembly 15, the steering control 28, the rotating arm 25 and arm positioner 26 to form an image 65 on large surface area or walkway 100 as shown in FIG. 9. The logic and control unit 35 is connected to marking engine 23, the rotating arm 25 and arm positioner 26, sensors 42aand/or 42band positioning mechanism 62 for controlling the position of marking engine 23 in relationship to the area 100. The rotating arm 25 allows the marking engine 23 supported on the rotating arm 25 to be positioned outboard of the apparatus 10 such that when a swath 29aor 29bis printed the wheels 18 do not run over the swath 29aor 29b. As used herein the term “outboard” implies support of the print head for printing on the walkway at locations outside of the enclosed area defined by the current points of contact of the wheels (such as for example 18a, 18band 27) which support the apparatus on the walkway. The wheels 18a, 18band 27 may be relatively positioned on the vehicle so that they engage the surface as a tricycle would with three points of contact. The arm 25 may be rotated as indicated by the arrows 31 to positions “A”, “B”, or “C” depending on what is being printed. In this regard rotation of the arm 25 may be provided by a stepper motor or other mechanism attached to the arm for swinging it outboard from a storage position. In an alternative embodiment, the arm may be locked in the outboard position.

[0035] The apparatus 10 may move laterally to the right in the direction indicated by arrows 44aand 44bor to the left in the direction indicated by arrows 44cand 44dby auxiliary wheels not shown. Sensors 42aand/or 42bare disposed in sensing relationship to area 100 for sensing the vertical distance to area 100. Sensors 42aand/or 42bsense the distance to area 100, and send a signal via logic and control unit 35 to the positioning mechanism 62. The positioning mechanism 62 moves the marking engine 23 and thus print head 24 as indicated by arrow 66 (FIG. 4) maintaining constant distance between print head 24 and walkway area 100 to allow the respective multi-color ink or paint marking mediums 50a, 50b, 50c, and 50dto be applied to area 100 in accordance with the image to be formed. When apparatus 10 is in an image recording mode, printing is carried out by activating the logic and control unit 35 which in turn activates the stepper motors 20aand 20bto propel the apparatus 10 over the large surface area 100. In response to the position encoder means associated with each of the drive wheels 18aand 18b, and a print signal received by the apparatus 10, the marking engine 23 is selectively activated by the logic and control unit 35 to print the sequential printing swaths 29aor 29b.

[0036] In the preferred-embodiment of the present invention, there is adopted a printing method wherein the printing operation is divided into printing a plurality of printing swaths 29aor 29bupon the large surface area 100. The plurality of printing swaths 29aor 29bare adjacent to one another and are printed in sequential order as the apparatus 10 is guided over the surface area 100. The printing may also be accomplished by printing a raster line rather than a swath, which comprises a plurality of raster lines. The printing is carried out by activating the stepper motors 20aand 20bto propel the apparatus 10 over the surface area 100. In response to the encoders 19aand 19b, sensors 42aand 42b, and a print signal received by the apparatus 10, the print head 24 is selectively activated by the logic and control unit 35 to print the sequential printing swaths 29aor 29b. In addition, to prevent apparatus 10 from rolling over a swath already printed, the apparatus 10 is controlled in accordance with programming in the logic and control unit to laterally translate to the right in the direction indicated by arrows 44aand 44bor to the left in the direction indicated by arrows 44cand 44dby auxiliary wheels not shown, pivot around the common point 72 using the drive propulsion mechanism 15 and steering control 28 and/or move the print head 24 via the arm positioner 26 moving the arm 25 outboard of the apparatus 10 as shown in FIGS. 2 and 3. In printing of a swath multiple passes may also be provided so as to avoid printing adjacent pixels simultaneously.

[0037] Referring to FIG. 4, sensor 42aand/or 42bis preferably a laser system comprising a photodiode light source 74 capable of emitting a laser light beam 76 to be intercepted by area 100 and reflected therefrom to define a reflected light beam 78. In such a laser system, sensors 42aand/or 42bfurther comprises a light detector 79, which may be a CCD (charged Couple Device) associated with light source 74 for detecting reflected light beam 78. In this regard, the laser system comprising light source 74 and detector 79 may be a modified “IMPULSE”™ model laser system available from Laser Technology, Incorporated located in Englewood, Colo. In addition to sensing the distance from the print head 24 to the area 100 sensors 42aand/or 42bmay be used to determine the relative color of the area to be printed for example white concrete or black asphalt. The mechanism for adjusting the position of the print head relative to the walkway surface area 100 may be a bellows type mechanism or telescoping-like or piston-like mechanism.

[0038] Referring to FIG. 5, as another embodiment of the present invention, sensor 80 is a mechanical follower mechanism comprising a telescoping spring-loaded follower 150 having an end portion 155 (e.g., a rollable ball bearing) adapted to contact area 100 and follow there along. In this case, telescoping follower 150 is capable of extending and retracting as indicated by arrow 157 in order to follow contour of area 100, and is also capable of generating an electrical signal indicative of the amount follower 150 extends and retracts with respect to area 100. It should be appreciated that sensor 80 and print head 24 need not be pointing at the same location on area 100 as long as the initial position of sensor 80 relative to the initial position of print head 24 is known at the start of the mapping process.

[0039] Referring now to FIG. 6, print head 24 (see FIG. 1), which in this embodiment is a DOD inkjet print head comprises a plate 70 having a plurality of nozzles 71a, 71b, 71c, and 71d. As previously discussed in FIG. 1 like numerals indicate like parts and operations. Each of the nozzles is capable of ejecting a drop 88 (see FIG. 8) of marking solution 50atherefrom to be intercepted by the large surface area 100. Referring to FIG. 7, there is illustrated a cross-sectional view of the print head 24 as taken along line 7—7 of FIG. 5. Nozzles 71a, 71b, 71c, and 71dare connected to channel-shaped chambers 75a, 75b, 75cand 75d. The chambers 75a, 75b, 75cand 75dare in liquid flow communication with respective reservoirs 45a, 45b, 45cand 45dshown in FIG. 1 via flexing tubing lines 73a, 73b, 73c, and 73drespectively. In this manner, respective color marking solutions of color ink or paint flow through respective tubing lines 73a, 73b, 73c, and 73dand into respective chambers 75a, 75b, 75cand 75d. In addition, each of the nozzles 71a, 71b, 71c, and 71bdefines a nozzle orifice 81a, 81b, 81c, and 81dcommunicating with chamber 75a, 75b, 75cand 75drespectively for flow of the respective liquid to the respective nozzle orifice.

[0040] Referring now to FIG. 8, which is an enlargement of the nozzle 71aof FIG. 7. As the marking solution flows into chamber 75aa marking solution body 85 is formed. A marking solution meniscus 82 is disposed at orifice 81awhen marking solution body 85 is disposed in chamber 75a. In this position of marking solution meniscus 82, marking solution meniscus 82 has a surface area 86. By way of example only and not by way of limitation, orifice 81amay have a radius of approximately 60 μm. When a voltage is applied to piezoelectric transducer 87a, drop 88 of marking solution 50ais ejected from nozzle 71ain the direction of arrow 89.

[0041] Referring again to FIG. 7, the plurality of nozzles 71a, 71b, 71c, and 71dare pointed at the common point 72 so that varying colors can be created with a single pass of the print head 23. The marking engine 23 may comprise more than one print head 24. The controls for the multihead print head can also be programmed to provide for color marking of adjacent spots or spots somewhat spaced from each other. The amount of marking solution 50a, 50b, 50c, and 50damount may range in drop size from 32 Pico liters to 300 Pico liters depending on the amount of coverage, resolution in dots per inch and the time to print desired. For example, using a drop size of 128 Pico liters and a resolution of 150 pixels per inch a six foot by six foot image may be printed in approximately four and one half minutes or at a print rate of approximately 500 square feet per hour. The amount of coverage also depends of the characteristics of the surface being covered. The coarser the surface the greater the coverage required. The multiple colors for a pixel may not exactly overlap but can have some overlap or else a close positioning relative to each other. The print head 24 is capable of marking in any number of colors including the complementary color sets such as cyan, magenta, and yellow. When mapping the area 100 (the mapping process is described later with reference to FIG. 11), sensors 42aand/or 42bdetect the color and characteristic of the surface of area 100. For example, if the apparatus 10 were printing on grass the surface color would be predominantly green. The logic and control unit 35 would indicate to the user via the display 37 what color marking solution is needed. Likewise, the processor is programmed to determine the predominant color of the surface, and indicates to the user whether or not or how much of a background color is to be painted on the area before printing the image.

[0042] The coarseness of the surface can be determined by how the distance from the surface to the print head varies in relation to linear distance traveled. In the case where the sensors 42aand/or 42bsense a dark surface such as asphalt driveway, a supplementary white color may be applied to the area 100 before the cyan, magenta and yellow is applied to create the image 65. Alternately in the case where the sensors 42aand/or 42bsense a light surface such as concrete a supplementary black color may be added similar to a desktop inkjet printer applying cyan, magenta, yellow and black. When the sensors sense a particular color surface, the printing algorithm in the logic and control unit 35 can automatically adjust the amount of cyan, magenta, yellow, black or white marking solution based on look up tables that have been heuristically determined. Depending on what surface a user desires to mark, any number of colors deemed appropriate for generation of full-color images can be used.

[0043] Therefore, referring to FIG. 1, the apparatus 10 is controlled by logic and control unit 35, which receives directions from the input panel 37 (see FIG. 10) and image data from an external memory source such as computer not shown, from the communication device 40 such as an RF receiver and transmitter, from an internal memory source such as the EPROM 55, inserted into the EPROM slot 60 or from the logic and control unit 35 itself. The logic and control unit 35 is in communication with the marking engine 23 and print engine 24 via lines 90a, 90b, 90c, and 90d. Using the nozzles 71a, 71b, 71c, and 71d, marking engine 15 can create a color image 65 on the large area or walkway 100 as shown in FIG. 9.

[0044] Referring to FIG. 9, using encoders 19aand 19b(see FIGS. 2 and 3) and mapped image 65 (the mapping process is described later with reference to FIG. 11) the apparatus 10 returns to the starting position 102 to begin the printing process. The logic and control unit 35 is electrically coupled by means of suitable power boosting control electronics to the propulsion assembly 15 and steering control 28 for selectively activating the stepper motors 20aand 20band steering control 28, thereby rotating the drive wheels 18aand 18band propelling the apparatus 10 over the large surface area 100. For example, the propulsion assembly 15 is activated by receiving electrical pulses from the logic and control unit 35. In response to each of the electrical pulses, the stepper motors 20aand 20beach rotates a fraction of a revolution. In response to rotation of the stepper motors 20aand 20b, each of the drive wheels 18aand 18bmay rotate independently. The set of drive wheels 18aand 18bfrictionally engages the top surface of the area 100 as each of the wheels rotates, thereby propelling the apparatus 10 over the area 100. The steering wheel 27 operates together with the drive wheels 18aand 18bto guide the apparatus 10. The encoders 19aand 19band sensors 42aand 42bmonitor the position and orientation of the apparatus 10 relative to the area 100 and portion of the image 65, which has already been printed. When printing in the direction indicated in FIG. 4 by arrow 47, sensor 42ais active. When printing in the direction indicated by arrow 48, sensor 42bis active. Both sensors 42aand 42bmay be active at the same time and may perform different functions such as one sensor sensing the image that has already been printed, while the other senses the distance to the surface.

[0045] The logic and control unit 35 counts the number of electrical pulses sent to the stepper motors 20aand 20band steering control 28. It should be noted that the present invention is not limited in the use of a stepper motor and steering control since other types of electric motors can be substituted and controlled by electric signals from the logic and control unit 35 with beneficial results. Accordingly, the encoder can be alternatively embodied, for example, by software which programs the logic and control unit 35 to count a number of electrical pulses respectively generated by shaft rotation encoders respectively coupled to each of the rolling members.

[0046] Referring to FIG. 10, the input panel 37 comprises a display 92, which via a fiducial 94 shows the position of the apparatus 10 in relation ship to the large area or walkway 100, and a keyboard 96 for inputting instructions. The display 92 may be a touch screen.

[0047] Therefore, referring to FIGS. 1, 9, 10 and 11, the manner in which area 100 is mapped into x, y and z Cartesian coordinates will now be described. First, apparatus 10 is placed upon the large surface area 100 by the user at Step 270. The user then records the orientation of the apparatus 10 on the large area 100 by inputting, via the input panel 37, the location of the starting position 102 of the apparatus 10. For example, the starting position 102 can be located in a center 105, top right 110, top left 115, lower right 120 or lower left 125 position at Step 280. The user selects the image to be printed; the size the image is to be printed and activates the mapping sequence Step 290. Next, the logic and control unit 35 activates sensors 42aand 42band encoders 19aand 19b. That is, the logic and control unit 35 effectively determines distance or proximity of large surface area 100 from sensors 42aand 42b. Distance of this initial point is determined either by use of light beams 76/78 or follower 155 and encoders 19aand 19b. This initial point is designated as a datum point “0” and will have Cartesian coordinates of x=0, y=0 and z=distance from sensor 42aand 42bas at Step 300. The x, y and z coordinates for datum point “0” are sent to logic and control unit 35 and stored therein as at Step 310. Logic and control unit 35 then activates propulsion assembly 15 to increment drive wheels 18aand 18band encoders 19aand 19ba predetermined amount in order to sense a first measurement point “1” on area 100 as at Step 320. This first measurement point “1” is located at an epsilon or very small distance “δ” on area 100 in a predetermined direction from datum point “0” as at Step 330. Moreover, this first measurement point “1” will have coordinates of x=x₁, y=y₁, and z=z₁, where the values of x₁, y₁and z₁are distances defining location of measurement point “1” from datum point “0” in the well-known three-dimensional Cartesian coordinate system as illustrated by Step 340. The coordinates of measurement point “1” are sent to logic and control unit 35 and stored therein as at Step 350. Logic and control unit 35 then activates propulsion assembly 15 to increment drive wheels 18aand 18band encoders 19aand 19bepsilon distance “δ” to a second measurement point “2” on area 100 as at Step 360. That is, this second measurement point “2” is located at the epsilon distance “δ” on area 100 in a predetermined direction from first measurement point “1” as illustrated by Step 370. Moreover, this second measurement point “2” will have coordinates of x=x₂, y=y₂and z=z₂, where the values of x₂, y₂and z₂are distances defining separation of measurement point “2” from datum point “0” in the three-dimensional Cartesian coordinate system as illustrated by Step 380. These coordinates of second measurement point “2” are sent to logic and control unit 35 and stored therein as at Step 390. In similar manner, logic and control unit 35 activates propulsion to assembly 15 to increment drive wheels 18aand 18band encoders 19aand 19bby increments equal to epsilon distance “δ” about the entire area 100 to establish values of x=0, 1, . . . n_x; y=0, 1, . . . n_y; and z=0, 1, 2, . . . n_z, where n_x, n_yand n_zequal the total number of measurement points to be taken on area 100 in the x, y and z directions, respectively as at Step 400. Each measurement point is spaced-apart from its neighbor by epsilon distance “δ” as illustrated by Step 410. In this manner, all measurement points describing area 100 are defined relative to initial datum point “0”, which is defined by x=0, y=0 and z=distance from sensor 42aand 42bas illustrated by Step 420. The process disclosed hereinabove results in a three-dimensional grid map of area 100 being stored in logic and control unit 35 as x, y and z coordinates as at Steps 430, 440, 445 and 450. Alternately the entire area need not be mapped if the dimensions of the area where the image is to be printed are known.

[0048] Referring again to FIGS. 1, 9, 10 and 11, logic and control unit 35 performs a calculation which justifies color image 65 stored therein with the x, y and z map of area 100 as at Step 460. Preferably color image 65 has been previously stored in logic and control unit 35 and represented therein in the form of a plurality of color points defined by x′ and y′ two-dimensional Cartesian coordinates. That is, each point in color image 65 stored in logic and control unit 35 has been previously assigned x′, y′ and a color value for each x′ and y′ value representing color image 65 in the x′-y′ two-dimensional plane. This x′-y′ plane has an origin defined by values of x′=0 and y′=0. The values in the x′-y′ plane range from x′=0, 1, 2, . . . n_x′, and from y=0, 1, 2, . . . n_y′, where n_x′ and n_y′ equal the total number of color pixel points representing color image 65 in the x′ and y′ directions, respectively. Logic and control unit 35 then mathematically operates on the values defining the x′-y′ plane of color image 65 in order to justify the x′, y′ and color values forming color image 65 to the x and y measurement values forming color map of area 100. That is, logic and control unit 35 multiplies each x′ and y′ value by a predetermined scaling factor, so that each x′ and y′ value is respectively transformed into corresponding x″ and y″ values as at Step 470. There are several methods, which may be used to scale the image. One technique increases the size of each the individual pixels. A preferred method is to increase the number of pixels by interpolation. The transformation can be preformed via texture mapping techniques such as those described in Advanced Animation and Rendering Techniques Theory and Practiceby Watt and Watt. These techniques are well known in the art. The z coordinates of the measurement values obtained by sensor 42aand/or 42bremain undisturbed by this justification. That is, after logic and control unit 35 scales the x′ and y′ values, logic and control unit 35 generates corresponding x″ and y″ values (with the z coordinate values remaining undisturbed). The x″ values range from x″=0, 1, 2, . . . n_x″ and the y″ values range from y″=0, 1, 2, . . . n_y″, where n_x″ and n_y″ equal the total of pixel points representing image 65 in the x″ and y″ directions, respectively as illustrated by Step 480. It should be understood from the description hereinabove, that once the values of x″ and y″ are defined, the values of z are predetermined because there is a unique value of z corresponding to each x″ and y″ pair as illustrated by Step 490. These values of x″, y″ and z define where ink pixels are to be applied on area 100 as illustrated by Step 500. As described herein below, after the map and color image 65 stored in logic and control unit 35 are justified, logic and control unit 35 controls encoders 19aand 19b, stepper motors 20aand 20b, print head 24 and positioning mechanism 62 to print the now justified color image 65 on area 100 as described previously in FIG. 7. If desired, the position of the color image 65 in the x-y plane stored in logic and control unit 35 may be matched to the corresponding mapped portion of area 100 stored in the x′-y′ plane in order to obtain the necessary justification.

[0049] In another embodiment referring now to FIGS. 12 and 13, a path 205 representing an image 210 is drawn on the large surface area all walkway 100 using a handheld marker 215, which applies a material 220 such as a fluorescent dye, iron oxide, or a colorant, which is detected by the sensor 42aand/or 42bshown in FIG. 1. The marker 215 is used to draw the image 210, which can be a word 225, or an outline 230 of a graphic 235, etc. Using the signal produced by the sensor 42aand/or 42bas it tracks the material 220, the logic and control unit 35 controls the marking engine 23, the propulsion assembly 15, and the steering mechanisms 28 to add a selected color to the word 225 or fills in the graphic 235 completing the image 210 as the apparatus 10 follows the material 220. When filling in the outline 230 of the graphic 235 etc., the apparatus 10 follows the map stored in the internal memory or using the sensor 42aand/or 42bsenses the outline 230 previously created by the marker 215 or printed by the marking engine 23.

[0050] Referring to FIG. 14 in yet another embodiment of the present invention, the apparatus 10 may be guided over the area 100 using a remote control receiver device 606 such as a radio remote control used to control a remote control toy car or airplane as is known to those skilled in the art. The operator 608 holding a transmitter 609 and operating same to guide the apparatus 10 in this manner the marking engine 24 can be used to write or print an image 600 such as a name on the area 100.

[0051] Now referring to FIG. 15 in another embodiment of the present invention, apparatus 10 is used to print lines 602 on grass 605, much like people put lines down for badminton and volleyball courts 607. The apparatus 10 can follow signals received by the communications device 40 or may be equipped with a light sensor 610, which is used to sense and follow a laser beam 615 from a laser 620. The laser is placed and aligned at position “D: using a reflector 625 then positions “E”, “F”, and “G”. After the laser 620 is placed, the apparatus 10 using the sensor 610 follows the laser beam 615 and prints the line 602.

[0052] Referring to FIGS. 16 and 17, another aspect of the invention is to apply a stain or paint to decks 700 with apparatus 10 by following the path 705 drawn using the marker 215 described in FIG. 12. In this embodiment the material applied may be invisible to the unaided eye but visible to the sensors 42aand/or 42bor using a sensor 42aand/or 42bor a guide finger 43 such as a mechanical sensor (see FIG. 1) to following a board. Following the edge of a board 710 with sensor 42aand/or 42bor a guide finger 43, the apparatus 10 could add a decorative patterned border 715 to an otherwise plain decking material.

[0053] As is evident from the foregoing description, certain other aspects of the invention are not limited to the particular details of the examples illustrated, and it is therefore contemplated that other modifications and applications will occur to those skilled in the art. It is accordingly intended that the claims shall cover all such modifications and applications as do not depart from the true spirit and scope of the invention.