Patent Description:
Three dimensional printers are in widespread use. Examples of three dimensional printer technologies includes stereolithography, selective laser sintering, and fused deposition modeling to name a few. Stereolithography-based printers utilize a controllable light engine to selectively harden or solidify a liquid photocure resin one layer at a time. In some embodiments the light engine includes a light source that illuminates a spatial light modulator.

Some of these light engines originate from projectors that are used for displaying images and video. When these light engines are used for three dimensional printers, certain inefficiencies result because these light engines have electronics optimized for the display of full motion video. There is a need to redesign the electronics to be optimal for three dimensional printing. <CIT> discloses a solid shaped body having sufficient hardness by enlarging the degree of polymerization by a method wherein a plurality of times of light irradiation are performed at the predetermined time intervals to the same position of liquid photo-setting resin. <CIT> discloses a system for fabricating a three-dimensional object, the system comprising:.

The invention is reflected in independent claim <NUM>. Preferred embodiments are reflected in claims <NUM> to <NUM>. In a first aspect of the invention, a three dimensional printing system includes a vessel for containing photocure resin, a fixture for supporting a three dimensional article of manufacture, a movement mechanism for incrementally displacing the fixture, a light engine, and a controller that is electrically or wirelessly coupled to the movement mechanism and the light engine. The vessel includes a lower surface having a transparent sheet in contact with the photocure resin. The three dimensional article of manufacture has a lower face that is in facing relation with the transparent sheet. The light engine is configured to apply pixelated light through the sheet and to the lower face in order to solidify thin slices of the photocure resin proximate to a build plane. The build plane defines a lateral area that the light engine is capable of curing. The controller activates the light engine to perform the following steps: (a) receive a first incoming slice energy data array; (b) process the first incoming slice energy data array to define a first image frame; (c) receive an on signal; (d) activate the first light source in response to the on signal; (e) repeatedly send the first defined image frame to the first spatial light modulator during a defined cure time for a layer of the resin; (f) receive an off signal; (g) deactivate the first light source in response to the off signal; and (h) repeat steps (a) - (g) until the three dimensional article of manufacture is formed.

In one implementation the light engine includes a system processor coupled to a digital mirror device module and a light source module. In one embodiment the digital mirror device module includes an image scaler, a digital mirror device formatter, and a digital mirror device. The image scaler processes the received first slice image to do one or more of correction, calibration, scaling, and stitching and to provide a scaled energy data array. The digital mirror device formatter converts the scaled energy data array into an image frame compatible with the digital mirror device. The digital mirror device includes a digital mirror array which includes at least one million individually addressable mirror elements. The light source module includes a light source driver coupled to a light source.

In another implementation the first image frame defines a sequence of bit planes for individual pixel elements of the first spatial light modulator. An energy value delivered for each pixel element is determined by which bit planes are in an "on" state. Thus, the first image frame is an array of binary numbers with bit positions in a binary number corresponding with a bit plane.

In yet another implementation the first light source is activated simultaneously with a "temporal leading edge" of one of the defined image frames. The temporal leading edge of an image frame is the left hand side of an image frame in a time domain - it is when the image frame begins to affect operation of the spatial light modulator. Thus the first light source is turned on simultaneously with the activation of the first spatial light modulator with one of the defined image frames.

In a further implementation an integer number of the defined image frames are received by the first spatial light modulator between the activation and the deactivation of the light source.

In a yet further implementation a non-integer number of the defined image frames are received by the spatial light modulator between the activation and the deactivation of the light source.

In another implementation the three dimensional printing system includes a second light engine including a second light source that illuminates a second spatial light modulator, the second light engine configured to: (a) receive a second incoming slice energy data array, the second incoming slice energy data array is complementary with the first incoming slice energy data array to allow the first and second light engines to have different but partially overlapping build fields; (b) process the incoming slice energy data array to define a second image frame; (c) receive the on signal from the first light engine; (d) activate the second light source in response to the on signal; (e) repeatedly send the second defined image frame to the second spatial light modulator during the defined cure time; (f) receive the off signal from the first light engine; (g) deactivate the second light source in response to the off signal; and (h) repeat steps (a) - (g) until the three dimensional article of manufacture is formed.

In yet another implementation the first light engine sends the incoming slice energy data array along a first data path to a digital mirror device module and sends the on and off signals along a second data path to a first light source module.

In a second aspect of the invention, a three dimensional printing system includes a vessel for containing photocure resin, a fixture for supporting a three dimensional article of manufacture, a movement mechanism for incrementally displacing the fixture, a light engine, and a controller that is electrically or wirelessly coupled to the movement mechanism and the light engine. The vessel includes a lower surface having a transparent sheet in contact with the photocure resin. The three dimensional article of manufacture has a lower face that is in facing relation with the transparent sheet. The light engine is configured to apply pixelated light through the sheet and to the lower face in order to solidify thin slices of the photocure resin proximate to a build plane. The build plane defines an area that the light engine is capable of curing. The light engine includes a light source, a spatial light modulator that is illuminated by the light source, a system processor for receiving an incoming slice energy data array and light source switching signals; an image scaler that receives and processes the incoming slice energy data array and outputs a scaled energy data array after one or more of correcting, calibrating, scaling, and stitching of the incoming slice energy data array; a digital mirror device formatter that receives and converts the scaled energy data into an image frame and repeatedly sends the image frame to the spatial light modulator; and a light source driver that receives the light source switching signals and turns the light source on for a cure time duration that overlaps with the repeated image frame. In a first embodiment turning the light source on is synchronized with the start of one of the image frames. In a second embodiment an integer number of the image frames are received by the spatial light modulator while the light source is on. In a third embodiment a non-integer number of the image frames are received by the spatial light modulator while the light source is on.

In one implementation the light engine is a plurality of light engines configured to cooperatively generate a composite build plane, the plurality of light engines receiving different but complementary incoming slice energy data arrays. The plurality of light engines includes a master light engine and at least one subsidiary light engine, the master light engine receives the switching signals and routes them to the at least one subsidiary light engine.

In a third aspect of the invention a three dimensional printing system includes a vessel for containing photocure resin, a fixture for supporting a three dimensional article of manufacture, a movement mechanism for incrementally displacing the fixture, a plurality of light engines, and a controller that is electrically or wirelessly coupled to the movement mechanism and the plurality of light engines. The vessel includes a lower surface having a transparent sheet in contact with the photocure resin. The three dimensional article of manufacture has a lower face that is in facing relation with the transparent sheet. The light engines are configured to apply pixelated light through the sheet and to the lower face in order to solidify thin slices of the photocure resin proximate to a composite build plane. The composite build plane defines an area that the light engine is capable of curing. The plurality of light engines include a master light engine and at least one subsidiary light engine. The master light engine includes a system processor that is configured to: (a) receive an incoming slice energy data array specific to the master light engine; (b) receive light source switching signals; (c) route the incoming slice energy data array specific to the master light engine to a digital mirror device module that is within the master light engine; (d) apply the switching signals to a light source module that is within the master light engine; and (e) route the switching signals to the at least one subsidiary light engine.

In one implementation the composite build plane is defined by a plurality of partially overlapping build fields. Each build field is individually formed by one of the plurality of light engines.

In another implementation the digital mirror device module includes an image scaler, a digital mirror device formatter, and a digital mirror device. The image scaler processes the incoming slice energy data array to define a scaled energy data array and the digital mirror device formatter processes the scaled energy data array to define an image frame. The switching signals include an on signal and an off signal. A cure time is defined by a time duration between the on signal and the off signal. The digital mirror device formatter is configured to sequentially send an integer number of image frames to the digital mirror device during the cure time.

In yet another implementation the digital mirror device module includes an image scaler, a digital mirror device formatter, and a digital mirror device. The image scaler processes the incoming slice energy data array to define a scaled energy data array and the digital mirror device formatter processes the scaled energy data array to define an image frame. The switching signals include an on signal and an off signal. A cure time is defined by a time duration between the on signal and the off signal. The digital mirror device formatter is configured to sequentially send a non-integer number of image frames to the digital mirror device during the cure time.

<FIG> is a schematic block diagram of an exemplary three dimensional printing system <NUM>. In describing this the following figures, mutually perpendicular axes X, Y and Z will be used. Axes X and Y are lateral axes. In some embodiments X and Y are also horizontal axes. Axis Z is a central axis. In some embodiments Z is a vertical axis. In some embodiments the direction +Z is generally upward and the direction -Z is generally downward.

Three dimensional printing system <NUM> includes a vessel <NUM> containing photocurable resin <NUM>. Vessel <NUM> includes a transparent sheet <NUM> that defines at least a portion of a lower surface <NUM> of vessel <NUM>. A light engine <NUM> is disposed to project light up through the transparent sheet <NUM> to solidify the photocure resin <NUM> and to thereby form the three dimensional article of manufacture <NUM>. The three dimensional article of manufacture <NUM> is attached to a fixture <NUM>. A movement mechanism <NUM> is coupled to fixture <NUM> for translating the fixture <NUM> along the vertical axis Z.

A controller <NUM> is electrically or wirelessly coupled to the light engine <NUM> and the movement mechanism <NUM>. Controller <NUM> includes a processor (not shown) coupled to an information storage device (not shown). The information storage device includes a non-transient or non-volatile storage device (not shown) that stores instructions that, when executed by the controller <NUM> can be contained in a single IC (integrated circuit) or multiple ICs. Controller <NUM> can be at one location or distributed among multiple locations in three dimensional printing system <NUM>. Processor controls the light engine <NUM> and the movement mechanism <NUM>.

The three dimensional article of manufacture <NUM> has a lower face <NUM> that faces the transparent sheet <NUM>. Between the lower face <NUM> and the transparent sheet <NUM> is a thin layer of resin <NUM>. As light engine <NUM> applies light energy through the transparent sheet <NUM> it polymerizes resin proximate to a "build plane" <NUM> which can be coincident or proximate to the lower face <NUM>.

The light engine <NUM> includes a light source <NUM>, a spatial light modulator <NUM>, and other devices (see <FIG>). Light source <NUM> illuminates spatial light modulator <NUM> which generates a pixelated image that is projected up through the transparent film <NUM>. In an exemplary embodiment, light source <NUM> includes one or more light emitting diodes and/or lasers. The light source <NUM> can generate blue or ultraviolet light for curing layers of resin <NUM>. In an exemplary embodiment, the spatial light modulator <NUM> is a digital mirror device <NUM> that can include one million or more controllable mirror elements. Each mirror element (not shown) has at least two positions including an "on" position and an "off' position. In the "on" position it transmits light to illuminate a "pixel element" <NUM> of the build plane <NUM>. In an "off" position it leaves that pixel <NUM> element dark. (<FIG> illustrates the build plane <NUM>).

Controller <NUM> controls the light engine <NUM> to selectively harden a new layer of resin onto the lower face <NUM>. After each layer of resin is hardened, controller <NUM> controls movement mechanism <NUM> to raise the three dimensional article of manufacture <NUM> to allow for replenishment of the thin layer of resin <NUM>.

<FIG> depicts the lateral build plane <NUM> for a fixed value of Z. The lateral build plane <NUM> is defined a lateral extent of the light engine in X and Y for the fixed value of Z. The lateral build plane <NUM> has a center <NUM> and lateral edges <NUM>. Lateral edges <NUM> define the lateral extent of the lateral build plane <NUM>. While the lateral build plane <NUM> is shown as rectangular it is to be understood that distortions and other artifacts may render the lateral build plane <NUM> to have nonlinear lateral edges <NUM> and/or a non-rectangular shape.

Within the lateral build plane <NUM> are pixel elements <NUM>. Each pixel element <NUM> is defined by the spatial light modulator <NUM>. In an exemplary embodiment, each pixel element <NUM> corresponds to a mirror element of the spatial light modulator <NUM>. <FIG> depicts build plane <NUM> as having far fewer pixel elements <NUM> than a real system for illustrative simplicity. In practice, build plane <NUM> can have one million or more individual pixel elements <NUM>.

<FIG> is an electrical block diagram depicting light engine <NUM> which includes system processor <NUM> that is coupled to information storage device <NUM>, light source module <NUM>, and digital mirror device module <NUM>. Light source module <NUM> includes light source driver <NUM> and light source <NUM>. Digital mirror device module <NUM> includes image scaler <NUM>, digital mirror device formatter <NUM>, and digital mirror device <NUM>.

System processor <NUM> orchestrates most or all of the major functions of the light engine <NUM>. System processor <NUM> is configured to receive an incoming slice energy data array from controller <NUM> that defines at least a portion of a new layer of the article of manufacture <NUM>. The incoming slice energy data array defines a two dimensional array of energy values that define optical cure energy to be applied versus position in X and Y. The spacing of the energy values in X and Y may or may not correspond to the pixel array on the spatial light modulator <NUM>. The system processor <NUM> transmits the incoming slice energy data array to the image scaler <NUM> of the digital mirror device module <NUM>.

Information storage device <NUM> can include one or more memory devices that store incoming or processed data for the system processor <NUM>. Such data can include the incoming slice energy data array.

Image scaler <NUM> processes the incoming image slice data to provide one or more of correction, calibration, scaling, and stitching. Correction includes de-warping, and corrections for distortions such as barrel distortion and the keystone effect. Calibration can include compensation for light source <NUM> output and variation in an optical path length from the light engine <NUM> to the build plane <NUM>. Scaling can include remapping and frame rescaling. Remapping is the conversion of the incoming data array spacing of energy values to the spacing of the pixel array of the spatial light modulator <NUM>. Frame rescaling is the scaling of the energy values from a total energy per pixel element <NUM> to an energy value per pixel element for one frame. For example, if it takes <NUM> frames to provide a required cure time with light source <NUM>, then the energy values would be reduced by <NUM>% for each frame. Finally, stitching adjustments are performed when more than one light engine is used to define a build plane <NUM>. In some alternative embodiments, part of the correction, calibration, scaling, and stitching can be performed by the controller before the data is passed to the digital mirror device module <NUM> or by the digital mirror device formatter <NUM>. Then the image scaler <NUM> may not need to perform all of these functions. After these functions are performed, the image scaler <NUM> passes resultant scaled energy data array to the spatial light modulator formatter <NUM>.

Digital mirror device formatter <NUM> formats the scaled energy data array to a format compatible with the digital mirror device <NUM>. The scaled energy data array has a scaled (for the frame period) energy value for each pixel. The digital mirror device formatter <NUM> converts each scaled energy value into a binary number corresponding to a sequence of bit planes. A sequence of bit planes is depicted in <FIG>. Each bit plane is a time duration during which a pixel element is either on or off. When a binary value of <NUM> is sent for a given bit plane, the pixel element is then turned on during the bit plane time duration. When a binary value of <NUM> is sent for a given bit plane, the pixel element is turned off for the bit plane time duration. <FIG> illustrates a <NUM> bit image frame. The bit planes include a least significant bit (LSB) or bit zero that is the narrowest time duration defined for a mirror element to be on or off. The next most significant bit (bit one) has twice the time duration of bit zero. This repeats up to the most significant bit (MSB). While <FIG> depicts a six bit frame for simplicity, other systems may utilize <NUM> bit frames or more or less bits. A binary number of <NUM> would have bit zero turned on, bit two turned off, but three turned on, and so on for a six bit frame. The binary number thus defines the frame data for a given pixel element. The digital mirror device formatter <NUM> sends the image frame data for the build plane <NUM> to the digital mirror device <NUM> which sequentially activates and deactivates the individual mirror elements accordingly.

The system processor <NUM> is configured to receive switching signals from controller <NUM> and to pass the switching signals to the light source driver <NUM> of the light source module <NUM>. For embodiments having more than one light engine <NUM>, the system processor <NUM> can also send the switching signals to other light engines <NUM>. The light source driver <NUM> provides power to the light source <NUM>. In an exemplary embodiment light source <NUM> is a light emitting diode (LED) that emits ultraviolet (UV) light. The switching signals include an "on" signal that activates (turns on) the light source <NUM> and an "off" signal that deactivates (turns off) the light source <NUM>. In other embodiments the light source <NUM> includes one or more of a laser and a blue light emitter.

Also depicted in <FIG> is the transmission of light (thicker gray arrows <NUM> and <NUM>) through the three dimensional printing system <NUM>. Element <NUM> depicts the "raw" or unprocessed light emitted by the light source <NUM>. Element <NUM> depicts the pixelated light that is reflected by the digital mirror device <NUM> and to optics that in turn deliver the pixelated light to the build plane <NUM>.

<FIG> is a flowchart and <FIG> is a timing diagram depicting an exemplary method <NUM> of operation for the three dimensional printing system <NUM>. According to step <NUM>, the system processor <NUM> receives incoming slice N energy data array (from controller <NUM>) to solidify an Nth layer of the three dimensional article of manufacture <NUM>. System processor <NUM> delivers the incoming slice N energy data array to the image scaler <NUM>. Step <NUM> is depicted as the top graph in <FIG>. Receipt of slice N and slice N+<NUM> image data is represented as the up arrows.

According to step <NUM> the image scaler <NUM> processes the slice N image data to provide one or more of correction, calibration, scaling, and stitching. As an alternative, one or more of these functions can occur in controller <NUM> or in the digital mirror device formatter <NUM>. One advantage over performing such functions in controller <NUM> is speed because the components of the digital mirror device module <NUM> has dedicated hardware that can perform these functions very rapidly. The image scaler <NUM> then delivers a scaled energy data array to digital mirror device formatter <NUM>.

According to step <NUM> the digital mirror device formatter <NUM> converts the scaled energy data array to an image frame having representation of bit planes (as depicted in <FIG> for one image frame). According to step <NUM> the formatted image frame data is repeatedly sent to the digital mirror device <NUM>. The middle graph of <FIG> depicts six image frames being sent to the digital mirror device <NUM> during a time duration that contains slice N. In general M frames are contained within a slice time duration and can vary from one frame to any number that are sufficient to properly solidify a layer of resin <NUM>.

In some embodiments each frame has a time duration of <NUM>/<NUM>th of a second. A total cure time can be one or two seconds. A one second cure time would require <NUM> of such image frames. A two second cure time would require <NUM> image frames. In this exemplary embodiment one image frame may contain <NUM> bit planes. In other embodiments one image frame can contain <NUM>, <NUM>, <NUM>, or more bit planes depending upon a desired energy resolution.

Other cure times are possible depending on the cure speed of the resin <NUM> being used. Other frame time durations are possible such as <NUM>/<NUM>th of a second, <NUM>/<NUM>th of a second, and so on. The number of bit planes during a frame can also vary depending upon the desired resolution.

Concurrent to the repeated sending of frames (step <NUM>) steps <NUM> to <NUM> are performed. According to step <NUM> the system processor <NUM> receives an "on" switching signal from controller <NUM>. As part of step <NUM> system processor <NUM> delivers the on signal to the light source driver <NUM> which then activates or turns on the light source <NUM>.

According to step <NUM> the light source remains on during a cure time. During step <NUM> the digital mirror device formatter <NUM> continues to send image frames to the digital mirror device <NUM>.

According to step <NUM> the system processor receives an "off" switching signal. As part of step <NUM> the system processor delivers the off signal to the light source driver <NUM> which then deactivates or turns off the light source <NUM>.

In some embodiments the on and off signals are sent by the system processor to one or more subsidiary light engines <NUM>. A subsidiary light engine <NUM> would have an architecture similar to that of discussed with respect to <FIG>. Such an arrangement will be discussed with respect to <FIG>.

The lower timing diagram of <FIG> depicts steps <NUM>-<NUM>. Arrows up indicate the light source <NUM> being turned on and the arrows down indicate the light source <NUM> being turned off. The horizontal axes of <FIG> indicate exemplary relative timing of receiving slice data, delivery of frames, and activation and deactivation of the light source <NUM>. Various embodiments are possible.

In some embodiments activation of the light source <NUM> can be synchronized with the beginning of a frame. In other embodiments they are not synchronized but the light source on and off occurs sometime during the delivery of the frames.

In some embodiments an integer number of frames are delivered by the digital mirror device formatter <NUM> to the digital mirror device <NUM> during the cure time of step <NUM>. In other embodiments a non-integer number of frames are delivered by the digital mirror device formatter <NUM> to the digital mirror device <NUM> during the cure time of step <NUM>.

According to step <NUM> controller <NUM> activates movement mechanism <NUM> to incrementally move the 3D article of manufacture <NUM> upward. According to step <NUM> the value of N increments to N + <NUM> so that the N+<NUM> slice image data can be received by the system processor <NUM>. The sequence <NUM> repeats until the 3D article of manufacture <NUM> is fully formed.

<FIG> is a schematic block diagram of an exemplary three dimensional printing system <NUM> which is similar to that depicted in <FIG> except for the use of more than one light engine <NUM>. This enables the imaging of laterally larger 3D articles of manufacturing <NUM> without a reduction in resolution. Otherwise like element numbers indicate like or similar elements.

The light engines <NUM> (light engine A and light engine B) have a zone of overlap <NUM> over which both light engines <NUM> provide energy to the same portion of the build plane <NUM>. While two light engines <NUM> are shown, it is to be understood that the three dimensional printing system <NUM> can include one or more light engines <NUM> and can include any number of light engines <NUM>.

<FIG> depicts a composite build plane <NUM> that is formed by a composite of four light engines A, B, C, and D. The different types of dashed outlines indicate overlapping build fields within the composite build plane <NUM> that are addressed by the light engines <NUM>. For example, the upper left build field that is bounded by the dotted rectangle A is the field of build plane <NUM> that is addressed by light engine A. Each of the build fields has a non-overlapping field portion and an overlapping field portion. The overlapping field portion overlaps with one or more of the other build fields. The indicated field portion <NUM> is an area of build plane <NUM> over which build field A overlaps with build field field B. Indicated build field portion <NUM> is an area of build plane <NUM> over which all four build fields A, B, C, and D overlap. The composite build plane <NUM> has an outer boundary <NUM> that is substantially rectangular but may have a different shape due to various distortions such as a keystone effect and/or barrel distortion. Also, each of build fields A, B, C, and D may be likewise distorted in shape.

<FIG> is an electrical block diagram depicting four exemplary light engines <NUM> according to capital letters A, B, C, and D. Refer to <FIG> to see additional details applicable to these light engines <NUM>. The light engines <NUM> includes a master light engine A and three subsidiary light engines B, C, and D. The distinction between master and subsidiary light engines <NUM> is related to the routing of signals and controlling and timing of a cure cycle. The master light engine A delivers the switching signals to the subsidiary light engines B, C, and D whereby a cure cycle for all four light engines <NUM> can be simultaneous.

A light engine <NUM> includes a system processor <NUM> coupled to a light source module <NUM> and a digital mirror device module <NUM> (see <FIG> for more details). The system processor <NUM> is configured to receive data from controller <NUM> for each new layer of photocure resin to be selectively cured onto the article of manufacture <NUM>. Data transmitted from controller <NUM> to light engines <NUM> includes incoming slice energy data arrays and switching signals.

The incoming slice energy data arrays are indicated in <FIG> by "A DATA", "B DATA", "C DATA", and "D DATA" for light engines A, B, C, and D respectively. The four data arrays define a slice for the composite build plane <NUM> illustrated in <FIG>. As can be seen, the controller <NUM> provides incoming slice energy data arrays directly to the individual light engines <NUM>. The data arrays are complementary and they individually include a non-overlapping array and an overlapping data array for a particular build field.

The switching signals are indicated by "SWITCH" in <FIG>. The switching signals are received by the system processor <NUM> of master light engine A which delivers the switching signals the light source module <NUM> within master light engine A. System processor <NUM> of master light engine A also delivers the switching signals to the subsidiary light engines B, C, and D. The system processor within a subsidiary light engine <NUM> then sends the switching signals to the light source module <NUM> which operates in the same way as the light source module <NUM> of the master light engine <NUM>. Having one master system processor <NUM> to receive and deliver the switching signals to subsidiary system processors <NUM> allows for synchronized and simultaneous operation of the light engines <NUM> which increases the speed of a three dimensional printing system <NUM> having multiple light engines <NUM>.

<FIG> is a flowchart depicting a method <NUM> of operation of a three dimensional printing system <NUM> having more than one light engine <NUM>. According to step <NUM> the controller <NUM> sends a slice N energy data array to each of light engines A, B, C, and D. Slice N data refers to data that defines an Nth layer of a three dimensional article of manufacture <NUM>. The data received by a particular light engine <NUM> (A, B, C, or D) is different than the other light engines since it defines one build field which has a portion that overlaps the three other build fields and a non-overlapping portion that is unique to that light engine.

According to step <NUM> the individual light engines <NUM> separately process the incoming slice N energy data arrays using image scaler <NUM>. Step <NUM> is similar to step <NUM> of <FIG> except that step <NUM> includes separate processing for the light engines <NUM>. According to step <NUM> the data from step <NUM> is formatted for the individual spatial light modulators <NUM>. According to step <NUM> image frames are repeatedly sent to light modulators <NUM>. For a given light engine <NUM>, this is the same as step <NUM> of <FIG> and the middle graph of <FIG>.

According to step <NUM> the controller <NUM> sends an on pulse to the system processor <NUM> of master light engine A. According to step <NUM> the system processor <NUM> of master light engine A routes the on signal to the system processors <NUM> for the subsidiary light engines B, C, and D. Also as part of step <NUM> the system processors <NUM> activate the light sources <NUM> for all of the light engines A, B, C, and D simultaneously. According to step <NUM> the light sources <NUM> are on for a cure time for the layer N. According to step <NUM> the system processor <NUM> of master light engine A receives an "off" signal. According to step <NUM> the system processor <NUM> of light source A routes the off signal to the system processors <NUM> for the subsidiary light sources B, C, and D. Also as part of step <NUM> the system processors <NUM> deactivate the light sources <NUM> for all of the light engines A, B, C, and D simultaneously.

During the cure time <NUM> a plurality of the image frames are sent to the digital mirror devices <NUM> for the individual light engines <NUM>. The timing diagram depicted in <FIG> depicts a similar sequence if <NUM> is replaced by step <NUM>, step <NUM> is replaced by step <NUM>, and steps <NUM>-<NUM> are replaced with steps <NUM>-<NUM>. As before the cure time <NUM> can contain an integer or non-integer number of image frames. The start of the cure time can be synchronized or not synchronized to the start of an image frame.

According to step <NUM> the movement mechanism <NUM> moves the three dimensionally article of manufacture <NUM> incrementally upward. According to step <NUM> the N increments to N+<NUM> for the next slice image data to be delivered from controller <NUM> to the light engines <NUM>. Steps <NUM> to <NUM> can be repeated until the three dimensional article of manufacture <NUM> is completed.

Claim 1:
A three dimensional printing system (<NUM>) which forms a three dimensional article of manufacture through a layer-by-layer process with each layer being formed by selectively curing photocure resin onto a face of the three dimensional article of manufacture comprising:
a vessel (<NUM>) for containing the photocure resin;
a controller (<NUM>);
a light engine (<NUM>) including:
a light source (<NUM>);
a spatial light modulator (<NUM>) that is illuminated by the light source;
a system processor (<NUM>) for receiving an incoming slice energy data array and light source switching signals, wherein the incoming slice energy data array defines a two dimensional array of energy values that define optical cure energy to be applied versus position in X and Y;
an image scaler (<NUM>) that receives and processes the incoming slice energy data array and outputs a scaled energy data array after one or more of correcting, calibrating, scaling, and stitching of the incoming slice energy data array;
a digital mirror device formatter (<NUM>) that receives and converts the scaled energy data into an image frame and repeatedly sends the image frame to the spatial light modulator;
a light source driver (<NUM>) that receives the light source switching signals characterized in that it further turns the light source on for a cure time duration that temporally overlaps with the repeated image frame.