WO2013170311A1

WO2013170311A1 - Apparatus and method for making an object

Info

Publication number: WO2013170311A1
Application number: PCT/AU2013/000516
Authority: WO
Inventors: Justin Elsey
Original assignee: Zydex Pty Ltd
Priority date: 2012-05-15
Filing date: 2013-05-15
Publication date: 2013-11-21

Abstract

An apparatus (100) for making an object (60) is disclosed. The apparatus has a spatial light modulator and a projection optic (18) for projecting radiation (6) from a radiation source (2) onto a photohardenable material. The apparatus comprises a controller (30) for controlling the radiance of the radiation source (2) and a photodetector (16) positioned to sample a portion (7) of the radiation emitted by the radiation source before it has passed a final element of the optical system. A method which may be executed using the apparatus (100) is also disclosed.

Description

APPARATUS AND METHOD FOR MAKING AN OBJECT

Field of the Invention

The present invention generally relates to an apparatus for making an object and a method for making an object.

Background of the Invention

A three dimensional object can be built up one section at a time. A layer of material is solidified in the shape of a section of the object by projecting electromagnetic radiation onto a photohardenable material by means of a spatial light modulator (SLM) having a fixed number of imaging elements, e.g. pixels. Once the section is formed, another is formed in contact with the previous section. Repetition of this process allows multi-laminate objects to be fabricated.

SLMs currently used in the fabrication of multilayer objects include micro-electro-mechanical-systems (MEMS) mirror arrays (such as DLP technology from Texas

Instruments) and liquid crystal arrays, which are integral components of a light projection engine.

The use of SLMs permits an entire section of an object is formed in a single exposure, resulting in fast fabrication speeds. SLM pixels in the "off" (i.e. dark) state may still leak light, however, resulting in

unintended exposure of the photohardenable material, causing it to degrade. Mechanical shutter systems have been employed to obstruct leaked light between exposures. Mechanical shutter systems increase the cost of the apparatus and have a finite switching time. SLMs provide limited control over the radiation intensity delivered to the photohardenable material. MEMS SLMs control the intensity of projected radiation by controlling the duty cycle of their mirrors between binary "on" and "off" states. Although this gives the impression of grayscale intensity output to a human observer due to persistence of vision, the peak intensity is, in fact, unchanged. Photohardenable materials (such as

photoinitiated acrylate resins) may behave nonlinearly with actinic radiation intensity due to oxygen inhibition and competing reaction kinetics . In some applications there may be other media included in the material which is sensitive to radiation intensity. Thus binary switching may adversely impact final material properties . Liquid crystal SLMs may provide true intensity control, however they are not suitable for ultraviolet radiation - the preferred radiation type for object fabrication

applications. Ultraviolet radiation rapidly degrades the liquid crystal material. Commercial liquid crystal SLMs are also limited in their intensity resolution, typically providing 8 control bits offering 256 intensity levels.

The average intensity of radiation reaching the photohardenable material may be adjusted to a

preconfigured set-point value by adjusting the grayscale intensity parameters of the SLM. This may allow

predetermined exposure times to be utilized with various radiation sources which may have different intensities. Excess radiation from bright radiation sources, however, is discarded instead of being utilized to build objects faster.

SLMs are not able to detect intensity variations in the radiation source during a fabrication process and make adaptations . Intensity variations may result in malformed sections, causing the fabrication process to fail.

Summary of Invention Disclosed herein is a method for making an object. The method comprises illuminating actinic radiation hardenable material with actinic radiation generated by an actinic radiation source to form a plurality of layers

constituting the object. The power of the actinic radiation generated by the actinic radiation source has a minimum in between the formation of adjacent layers of the plurality of layers.

In the context of this specification, an object is a tangible object. It may, for example, be solid, rigid or resilient. It may have one or more hollows or voids, such as that of a cup or tennis ball, for example. Generally, the object may be described as a solid object.

Generally but not necessarily, the actinic radiation hardenable material is a liquid. The liquid may comprise a layer of liquid. In alternative embodiments, the material may comprise a powder such as a fluidized polymer powder, or a fluid or paste. Any suitable material may be used .

In the context of this specification, a layer is to be understood to encompass a slice of the object. A planar layer encompasses a portion of the object located between two parallel planes that intersect the object. Generally, but not necessarily, the layers formed are planar layers.

Reducing the actinic radiation reaching the material by reducing the power of the generated actinic radiation may be more effective than using a radiation blocking device that selectively blocks the actinic radiation after generation. The radiation blocking device may not block all of the light. The radiation blocking device may have a slow switching time.

An embodiment comprises spatially modulating the actinic radiation from the actinic radiation source with a spatial light modulator. The spatial light modulator may have a fixed number of imaging elements.

A spatial light modulator may be used as a radiation blocking device to block the radiation between the formation of adjacent layers, but the spatial light modulator may generally still let some light through.

Reducing the generated actinic radiation may be more effective and result in less unwanted exposure of the material between the formation of adjacent layers which may degrade the material or result in a malformed object. Spatial light modulators may slowly degrade because of exposure to the actinic radiation. Reducing the power - or turning it off completely - of the light between the formation of adjacent layers may extend the life of the spatial light modulator. The spatial light modulator may be expensive and inconvenient to replace, so extending its life may be desirable. Similarly, the life of the light source may be extended. In an embodiment, the actinic radiation source is turned off in between the formation of adjacent layers of the plurality of layers.

In an embodiment, an electrical current driving the actinic radiation source has a minimum in between the formation of adjacent layers of the plurality of layers. The electrical current driving the actinic radiation source may be zero in between the formation of adjacent layers of the plurality of layers. In an embodiment, between the formation of adjacent layers of the plurality of layers, repositioning the object being made with respect to the material.

In an embodiment, the actinic radiation source comprises at least one of a light emitting diode (LED) , a laser, and a lamp .

Disclosed herein is a device for making an object. The device comprises a material receiver arranged to receive an actinic radiation hardenable material. The device comprises an actinic radiation source arranged to generate an actinic radiation for illuminating the actinic

radiation hardenable material when received by the material receiver. The device comprises a controller arranged to control the actinic radiation generator such that the hardenable material when so received is

illuminated with the actinic radiation to form a plurality of layers constituting the object. The power of the actinic radiation generated by the actinic radiation source has a minimum in between the formation of adjacent layers of the plurality of layers. An embodiment comprises a spatial light modulator arranged to modulate the actinic radiation generated by the actinic radiation source, and the controller is arranged to control the actinic radiation generator and the spatial light modulator such that the actinic radiation hardenable material when so received is illuminated with the actinic radiation spatially modulated by the spatial light modulator .

In an emboidment the spatial light modulator has a fixed number of imaging elements .

In an embodiment the controller is arranged to turn the actinic radiation source off in between the formation of adjacent layers of the plurality of layers.

In an embodiment the controller is arranged to cause an electrical current driving the actinic radiation source to have a minimum in between the formation of adjacent layers of the plurality of layers. The controller may be arranged to turn off the electrical current driving the actinic radiation source between the formation of adjacent layers of the plurality of layers .

An embodiment comprises a repositioner arranged to reposition the object being made, and the controller is arranged to, between the formation of adjacent layers of the plurality of layers, reposition the object being made with respect to the material.

In an embodiment, the actinic radiation source comprises at least one of a LED, a laser, and a lamp. Disclosed herein is a method for making an object. The method comprises, in each of a plurality of temporally spaced apart periods, generating an actinic radiation. The method comprises illuminating a material with the generated actinic radiation to form one of a plurality of layers constituting the object. The power of the generated actinic radiation is less between adjacent ones of the plurality of temporally spaced apart periods than during the temporally spaced apart periods.

In an embodiment, the generated actinic radiation' s power may be zero for a temporal interval between adjacent ones of the plurality of temporally spaced apart periods .

In an embodiment, generating the actinic radiation may comprise powering at least one of a light emitting diode (LED), a laser, and lamp to generate an actinic light. In an embodiment, the method may comprise spatially modulating the radiation in each of the plurality of temporally spaced apart periods .

Disclosed herein is a device for making an object. The device comprises an actinic radiation generator arranged to generate an actinic radiation. The device comprises a material receiver arranged to receive a material

responsive to the actinic radiation. The device comprises a controller arranged to control the actinic radiation generator such that in each of a plurality of temporally spaced apart periods the actinic radiation is generated and the material when so received is illuminated with the generated actinic radiation to form one of a plurality of layers constituting the object, the power of the generated actinic radiation being less between adjacent ones of the plurality of temporally spaced apart periods than during the temporally spaced apart periods.

In an embodiment, the controller may be configured to stop the actinic radiation generator from generating the actinic radiation for a temporal interval between adjacent ones of the plurality of temporally spaced apart periods.

In an embodiment, the actinic light generator may comprise at least one of a LED, a laser, and a lamp configured to generate actinic light.

In an embodiment, the device may comprise a spatial radiation modulator arranged to modulate the radiation during each of the plurality of temporally spaced apart periods. In an embodiment, the spatial radiation modulator may have a fixed number of imaging elements.

Disclosed herein is a method for making an object by using an actinic radiation to form a plurality of layers constituting the object The method comprises generating actinic radiation power information indicative of the actinic radiation's power. The method comprises using the actinic radiation power information to determine the time a material should be exposed to the actinic radiation to form one of the plurality of layers of a predetermined thickness. In an embodiment, the step of generating actinic radiation power information may comprise detecting a sample of the actinic radiation with a radiation detector. In an embodiment, the step of detecting a sample of the actinic radiation with a radiation detector comprises switching the majority of pixels of a spatial light modulator to a substantially off state. In an embodiment, the step of determining the time may comprise using information describing the expected thickness of a layer for an actinic radiation power and an exposure time. Disclosed herein is a device for making an object by using an actinic radiation to form a plurality of layers constituting the object The device comprises an actinic radiation generator arranged to generate the actinic radiation. The device comprises an actinic radiation power information generator arranged to generate actinic radiation power information indicative of the actinic radiation's power. The device comprises a processor configured to determine the time a material should be exposed to the radiation to form one of the plurality of layers of a predetermined thickness using the actinic radiation power information when so generated.

In an embodiment, the actinic radiation generator may comprise at least one of a LED, a laser, and a lamp configured to generate actinic light.

Disclosed herein is a device for making an object by illuminating a material with an actinic radiation to form each of a plurality of layers constituting the object. The device comprises an actinic radiation generator. The device comprises a vessel arrange for the material to be disposed therein. The device comprises an optical system arranged to deliver the actinic radiation to the vessel. The device comprises an actinic radiation detector system to sample the actinic radiation without interfering with the delivered actinic radiation. In an embodiment, the radiation detector system may be arranged to sample the actinic radiation before it has passed a final element of the optical system.

Disclosed herein is a device for making an object by receiving a material responsive to an actinic radiation and illuminating the material with the actinic radiation.

The device comprises an actinic radiation generator arranged to generate the actinic radiation. The device comprises a controller arranged to receive information and control the generation of actinic radiation by the actinic radiation generator in response to the received

information .

In an embodiment, the device may comprise an actinic radiation detector arranged to generate actinic radiation power information indicative of the power of the generated actinic radiation by detecting at least some of the actinic radiation when so generated, the actinic radiation detector being further arranged to communicate the actinic radiation power information to the controller for

controlling the generation of the actinic radiation. In an embodiment, the controller may be configured to control the generation of actinic radiation such that the received actinic radiation power information satisfies a predetermined condition.

In an embodiment, the predetermined condition comprises the actinic radiation power information is equal to a predetermined value. In an embodiment, the device may comprise a radiation spatial modulator arranged to spatially modulate the actinic radiation when so generated.

In an embodiment, the controller may be arranged to temporally coordinate the radiation spatial modulator with the actinic radiation generator.

In an embodiment, the device may be arranged to form a plurality of layers, wherein the device is arranged to generate less actinic radiation in a first temporal period between a second temporal period, in which one of the plurality of layers is formed, and a third temporal period, in which another one of the plurality of layers is formed .

In an embodiment, the device may be arranged to not generate the actinic radiation during the first temporal period . In an embodiment, the actinic radiation generator may comprise at least one of a light emitting diode (LED) , a laser and a lamp. In an embodiment, the controller may be arranged to control a current powering the actinic radiation

generator . In an embodiment, the controller may comprise a current modulator arranged to modulate the current.

Disclosed herein is a method for making an object. The method comprises receiving a material responsive to an actinic radiation. The device comprises receiving information. The device comprises generating the actinic radiation. The device comprises illuminating the material with the actinic radiation. In an embodiment, the method may comprise the step of generating actinic radiation power information indicative of the power of the generated actinic radiation by detecting at least some of the actinic radiation when so generated, and communicating the actinic radiation power information for controlling the generation of the actinic radiation .

In an embodiment, the method may comprise the step of controlling the generation of actinic radiation such that the received actinic radiation power information satisfies a predetermined condition.

In an embodiment, the predetermined condition may comprise the actinic radiation power information being equal to a predetermined value.

In an embodiment, the method may comprise the step of temporally coordinating a radiation spatial modulator arranged to spatially modulate the actinic radiation with the generation of the actinic radiation.

In an embodiment, the method may comprise forming a plurality of layers, wherein less actinic radiation is generated in a first temporal period between a second temporal period, in which one of the plurality of layers is formed, and a third temporal period, in which another one of the plurality of layers is formed.

In an embodiment, no actinic radiation may be generated in the first temporal period.

In an embodiment, the step of generating the actinic radiation may comprise the step of using at least one of a LED, a laser and a lamp to generate the actinic radiation.

In an embodiment, the method may comprise the step of controlling a current powering an actinic radiation generator generating the actinic radiation.

Any of the carious features of each of the above

disclosures, and of the various features of the

embodiments described below, can be combined as suitable and desired . enerator generating the actinic radiation.

Brief description of the Figures

In order to achieve a better understanding of the nature of the present invention, embodiments will now be described, by way of example only, with reference to the accompanying figures in which: Figure 1 shows a schematic elevation view of an embodiment of an apparatus for making an object;

Figures 2 and 3 each show a flow diagram of

embodiments of methods for making an object.

Detailed Description of embodiments of the invention

Figure 1 shows a schematic view of one embodiment of an apparatus for making an object, the apparatus being generally indicated by the numeral 100. Coordinate axes are shown in the figure where x is horizontally orientated and z is vertically orientated.

The apparatus 100 comprises a radiation source 2, in the form of an actinic radiation source, such as a light emitting diode (LED) , laser or lamp which emits radiation 6. The emitted radiation in this but not necessarily all emboidments, has a component wavelength in the ultraviolet range, i.e. from about 200nm to about 400nm. Example suitable wavelengths include 355nm, 385nm and 405nm. Other wavelengths (e.g. green) or other forms of radiation (e.g. electrons) may be used as appropriate.

Emitted radiation 6 travels via relay optics 8 to a prism 10. Prism 10, for example, a beam splitter or "total internal reflection" (TIR) prism, directs the radiation onto a spatial light modulator 12 (SLM) . Examples of suitable SLMs include, but are not limited to, Texas Instruments DLP micro-electromechanical system (MEMS) mirror arrays and liquid crystal on silicon (LCOS) devices. Generally any suitable SLM can be used. The spatial light modulator 12 receives bitmap information representing the layer of the objet being solidified via a controller 14, and switches the pixels of the spatial light modulator to an appropriate state to project the received bitmap image. The radiation 6 is reflected from the spatial light modulator 12 back through the prism 10 to a projection optic 18. Projection optic 18 may be a projection lens which images the reflective surface of the spatial light modulator onto the underside of a vessel 24 arranged to contain a photohardenable material in the form of a photohardenable liquid 22. In alternative

embodiments, a powder or other suitable materials may be used .

The photopolymer resin 22 may comprise a mixture of acrylate monomers and oligomers, photoinitiators ,

colourants and stabilizers such that the mixture

polymerizes when exposed to suitable light. Example liquids include Somos NEXT from DSM Somos, USA, and KZ- 1860-CL from Allied PhotoPolymers , USA.

The projected light causes a layer of the photopolymer resin to cure and attach to previously hardened layers of an object 60 on a fabrication platform 52.

Fabrication platform 52 can be positioned in the z- direction by a linear actuator 50. The linear actuator may comprise any one or more of linear motors, drive belts, stepper motors, rack and pinion arrangements, for example, or generally any suitable components arranged to provide linear motion.

Some radiation 7 of the radiation 6 incident on the prism 10 passes directly through the prism to a photodetector 16, such as a photodiode, which relays a signal to a controller 30 in the form of a microprocessor, a logic device, an FPGA or generally any suitable

controller. The signal carries information indicative of the power and/or irradiance of the incident radiation. In an embodiment, the signal is a voltage that is

proportional to the irradiance of the incident radiation. In another embodiment, the signal is a digital signal which carries information indicative of the irradiance of the incident radiation. The signal magnitude is correlated with the intensity, i.e. the irradiance, of the incident radiation 7. Controller 30 is also in communication with an electrical current modulator 4, in the form of a transistor, MOSFET or other suitable device which can control the electrical current input to the radiation source 2 and thereby vary its radiance, i.e. the intensity of the radiation 6 it emits. The controller may, for example, deliver a pulse-width modulated control signal to the electrical current modulator. Pulse width modulation signals permit very fine control. Thus, the current may be set with a high resolution over a wide range (e.g. in the order of six orders of magnitude or more) . Controller 30, current modulator 4, radiation source 2 and photodetector 16 may form a feedback control loop permitting control of the radiation 6 emitted from the radiation source 2 to a determined value. As the radiation reaching the vessel 24 is proportional to the radiation emitted by the radiation source 2 (and proportional also the some radiation 7 which passes through the prism) , the described control loop permits accurate control of the intensity of radiation reaching the vessel 24 once the proportionality factor is known. This factor may be determined by, for example, simultaneously measuring the radiation intensity reaching - li the vessel and the radiation intensity measured by the photodetector 16 during a calibration. An analytical method of determining the proportionality factor, or generally any suitable method, may alternatively be used. Alternatively, the photodetector may be positioned in another location provided that it can receive some of the light emitted by the radiation source 2 and does not block the projected light. For example, the photodetector could alternatively be located where indicated by the dashed outline 17, where it can receive light from the radiation source either directly 42 or by scattering 44 off other components, or both. In this but not necessarily all embodiments the photodetector is positioned to sample light before it has passed a final element of the optical system, such as the projection optic 18. That is, it may be positioned to detect light emitted from the radiation source 2 that has not passed through the projection optic 18 (unlike radiation 20 which has passed through the projection optic) . If the photodetector were positioned to detect a component of radiation 20 that has passed through the final optical element 18 it may block some of the radiation that may otherwise be incident on the

photohardenable material. Alternatively, a mechanical arm which may, but not necessarily, also act as a shutter may intermittently insert the photodetector into the radiation field to take measurements (e.g. part of radiation 20), although this may be inconvenient or more costly.

After a layer of photohardenable material has been exposed to the radiation for a requisite time to achieve a desired dose at the desired intensity, i.e. irradiance, physical operations may be required to prepare the vessel 24 and/or object being fabricated for the hardening of the next layer of the object. These operations may include the controller 30 activating the linear actuator 50 to separate the formed layer from the vessel, recoating the vessel with photohardenable material, and activating linear actuator 50 again to reposition the object at a new distance from the vessel ready to form the next layer. During this time, the controller 30 instructs the current controller 4 to deliver either substantially reduced or no current to the radiation source 2 . Substantially reduced may be, for example, a reduction of greater than one of 80%, 90%, 95%, 99% and 99.9%. The reduction may be below the threshold of the generation of the actinic radiations. The radiation intensity during this time is herein referred to as a "minimum" in the understanding that it is less than the average radiation intensity used for hardening a layer, even though it is possible for the radiation when hardening a layer to possibly drop to a low value or zero intermittently. As a result, radiation leakage to the vessel 24 (despite the finite contrast- ratio of the SLM) may be zero or close to zero during this operation, preventing unwanted photohardening without the use of an additional apparatus such as a physical shutter. Furthermore, the radiation source 2 may be prevented from experiencing wear or degradation during this time, thereby extending the lifetime of the radiation source 2 .

Furthermore, the SLM may be prevented from experiencing undue degradation due to the action of the incident radiation upon it. Ultraviolet radiation is known to cause rapid degradation of some DLP micromirror arrays and liquid crystal SLM devices. Thus the utilization of this method may greatly extend the working life of the

apparatus. This method is generally indicated with numeral 200 with step 202 in Figure 2. The photodetector 16 may provide useful information (i.e. a radiation intensity value) to a processor which controls the fabrication process. The processor may be, for example, an external processor. Alternatively, the processor may comprise or include controller 30. A method is generally indicated by numeral 300 with steps 302,304 in Figure 3. First, a look-up table for a particular photohardenable material comprising cure-thickness data as a function of radiation intensity (i.e. irradiance) and exposure time is supplied to the processor. The data in the look-up table may be generated experimentally for the particular photohardenable material by exposing different samples of it to radiation of different intensities for varying times, and measuring the resulting thicknesses of the hardened layers with a micrometer. An example of how such look-up table data may appear is shown in Table 1.

Table 1: Cure thickness in microns as a function of exposure intensity and time.

Prior to a fabrication process commencing, the intensity of the light source is measured with the photodetector 16 and the data is used to calculate the exposure time required to achieve the desired fabrication layer cure thickness. The exposure time for the process can be determined from the material's look-up table. For example, according to the example data shown in Table 1, if the measured intensity is 3.0 mW/cm 2 and the desired cure thickness is 40 microns per layer, then the required exposure time is 5 seconds. Interpolation and/or

extrapolation may be used to estimate the required exposure time when the measured intensity and required cure thickness fall between or outside measured data points in the table. For example, according to the example data shown in Table 1, if the measured intensity is 2 mW/cm^A2 and the desired thickness is 35 microns, the required exposure time may be linearly interpolated to be 7.5 seconds. Other types of interpolation and

extrapolation, such as cubic and spline methods, may be employed. The calculation may be performed by a processor of the apparatus (such as controller 30) or an external processor utilizing data provided by the apparatus, for example, over a network or input by a user.

Note that it is not necessary for the photohardenable material to be removed from the apparatus while the radiation intensity is measured if the following procedure is used: First the pixels of the SLM 12 are switched to the "off" state, then the radiation source 2 is switched on, then the radiation intensity measurement is made using photodetector 16, then the radiation source 2 is switched off. This procedure has the advantages that it can be performed during a fabrication process without interfering with the apparatus, and does not require user

intervention . In addition to, or instead of, sampling the radiation intensity for calculating the exposure time prior to the commencement of a fabrication process, the sampling and calculation may be performed during the fabrication process prior to the exposure of a particular layer, or even during the exposure of a particular layer. The sampling and calculation may be performed for each layer. In some embodiments, the measurements may be integrated over time to improve accuracy. Such approaches permit real-time adaptation of exposure time to variations in the radiation source's power (i.e. intensity of emitted light), which may occur during a fabrication process. For example, some radiation sources, including light emitting diodes, become less efficient with increasing temperature. As the temperature of the apparatus may vary during the fabrication process, different radiation output under otherwise similar conditions may result. Such real-time calculation and adaptation of exposure time can improve the reliability and performance of the apparatus. Now that embodiments of the invention have been described, it will be appreciated that some embodiments may have some of the following advantages :

• The apparatus may be configured to deliver no radiation between the exposure of subsequent layers of the object, without employing a mechanical apparatus such as a shutter. This may prevent leaked light causing unwanted exposure of the photohardenable material, and may reduce wear on the radiation source thereby extending its lifetime. • The lifetime of the SLM and/or radiation source may be extended due to reduced incident radiation on the SLM and reduced radiation generation in the intervals between the exposure of layers of the object.

• Radiation intensity may be measured in real-time during a fabrication process without interrupting the fabrication process or requiring user intervention .

• The appropriate exposure time for forming a layer of an object may be determined from a measured radiation intensity value using cure-thickness data. This permits full use of the available output from the radiation source, as opposed to other methods which require the available radiation to be attenuated to a pre-determined set-point .

It will be appreciated that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

Claims

1. A method for making an object, the method comprising: illuminating actinic radiation hardenable material with actinic radiation generated by an actinic

radiation source to form a plurality of layers

constituting the object, wherein the power of the actinic radiation generated by the actinic radiation source has a minimum in between the formation of adjacent layers of the plurality of layers.

2. A method defined by claim 1 comprising spatially

modulating the actinic radiation from the actinic radiation source with a spatial light modulator.

3. A method defined by claim 2 wherein the spatial light modulator has a fixed number of imaging elements.

4. A method defined by any one of the preceding claims wherein the actinic radiation source is turned off in between the formation of adjacent layers of the plurality of layers.

5. A method defined by any one of the preceding claims wherein an electrical current driving the actinic radiation source has a minimum in between the formation of adjacent layers of the plurality of layers.

6. A method defined by claim 5 wherein the electrical

current driving the actinic radiation source is zero in between the formation of adjacent layers of the plurality of layers.

7. A method defined by any one of the preceding claims comprising, between the formation of adjacent layers of the plurality of layers, repositioning the object being made with respect to the material.

8. A method defined by any one of the preceding claims wherein the actinic radiation source comprises at least one of a light emitting diode (LED) , a laser, and a lamp .

9. A device for making an object, the device comprising: a material receiver arranged to receive an actinic radiation hardenable material;

an actinic radiation source arranged to generate an actinic radiation for illuminating the actinic

radiation hardenable material when received by the material receiver; and

a controller arranged to control the actinic

radiation generator such that the hardenable material when so received is illuminated with the actinic radiation to form a plurality of layers constituting the object, wherein the power of the actinic radiation generated by the actinic radiation source has a minimum in between the formation of adjacent layers of the plurality of layers.

10. A device defined by claim 9 comprising a spatial

light modulator arranged to modulate the actinic radiation generated by the actinic radiation source, and the controller is arranged to control the actinic radiation generator and the spatial light modulator such that the actinic radiation hardenable material when so received is illuminated with the actinic radiation spatially modulated by the spatial light modulator .

11. A device defined by claim 10 wherein the spatial light modulator has a fixed number of imaging elements.

12. A device defined by any one of the claims 9 to 11 wherein the controller is arranged to turn the actinic radiation source off in between the formation of adjacent layers of the plurality of layers.

13. A device defined by any one of the claims 9 to 12 wherein the controller is arranged to cause an

electrical current driving the actinic radiation source to have a minimum in between the formation of adjacent layers of the plurality of layers .

14. A device defined by claim 13 wherein the controller is arranged to turn off the electrical current driving the actinic radiation source between the formation of adjacent layers of the plurality of layers.

15. A device defined by any one of the claims 9 to 14 comprising a repositioner arranged to reposition the object being made, and the controller is arranged to, between the formation of adjacent layers of the plurality of layers, reposition the object being made with respect to the material.

16. A device defined by any one of the claims 9 to 15 wherein the actinic radiation source comprises at least one of a LED, a laser, and a lamp.

17. A method for making an object, the method comprising:

in each of a plurality of temporally spaced apart periods, generating an actinic radiation; and illuminating a material with the generated actinic radiation to form one of a plurality of layers constituting the object, the power of the generated actinic radiation being less between adjacent ones of the plurality of temporally spaced apart periods than during the temporally spaced apart periods .

A method defined by claim 17 wherein the generated actinic radiation' s power is zero for a temporal interval between adjacent ones of the plurality of temporally spaced apart periods.

A method defined by either one of claims 17 and 18 wherein generating the actinic radiation comprises powering at least one of a light emitting diode (LED) a laser, and lamp to generate an actinic light.

A method defined by any one of the claims 17 to 19comprising spatially modulating the radiation in each of the plurality of temporally spaced apart periods .

A device for making an object, the device comprising: an actinic radiation generator arranged to generate an actinic radiation;

a material receiver arranged to receive a material responsive to the actinic radiation; and a controller arranged to control the actinic radiation generator such that in each of a plurality of temporally spaced apart periods the actinic radiation is generated and the material when so received is illuminated with the generated actinic radiation to form one of a plurality of layers constituting the object, the power of the generated actinic radiation being less between adjacent ones of the plurality of temporally spaced apart periods than during the temporally spaced apart periods .

22. A device defined by claim 21 wherein the controller is configured to stop the actinic radiation generator from generating the actinic radiation for a temporal interval between adjacent ones of the plurality of temporally spaced apart periods.

23. A device defined by either one of claim 21 and claim 22 wherein the actinic light generator comprises at least one of a LED, a laser, and a lamp configured to generate actinic light.

24. A device defined by any one of the claims 21 to 23 comprising a spatial radiation modulator arranged to modulate the radiation during each of the plurality of temporally spaced apart periods.

25. A method for making an object by using an actinic

radiation to form a plurality of layers constituting the object, the method comprising the steps of:

generating actinic radiation power information indicative of the actinic radiation' s power; and

using the actinic radiation power information to determine the time a material should be exposed to the actinic radiation to form one of the plurality of layers of a predetermined thickness.

26. A method defined by claim 25 wherein the step of

generating actinic radiation power information comprises detecting a sample of the actinic radiation with a radiation detector.

27. A method defined by either one of claim 25 and claim 26 wherein the step of determining the time comprises using information describing the expected thickness of a layer for an actinic radiation power and an exposure time .

A device for making an object by using an actinic radiation to form a plurality of layers constituting the object, the device comprising:

an actinic radiation generator arranged to generate the actinic radiation;

an actinic radiation power information generator arranged to generate actinic radiation power

information indicative of the actinic radiation' s power; and

a processor configured to determine the time a material should be exposed to the radiation to form one of the plurality of layers of a predetermined thickness using the actinic radiation power

information when so generated.

A device defined by claim 28 wherein the actinic radiation generator comprises at least one of a LED, a laser, and a lamp configured to generate actinic light .

A device for making an object by illuminating a material with an actinic radiation to form each of a plurality of layers constituting the object, the device comprising:

an actinic radiation generator;

a vessel arrange for the material to be disposed therein ;

an optical system arranged to deliver the actinic radiation to the vessel; and

an actinic radiation detector system to sample the actinic radiation without interfering with the delivered actinic radiation.

A device defined by claim 30 wherein the radiation detector system is arranged to sample the actinic radiation before it has passed a final element of the optical system.

A device for making an object by receiving a material responsive to an actinic radiation and illuminating the material with the actinic radiation, the device comprising :

an actinic radiation generator arranged to generate the actinic radiation; and

a controller arranged to receive information and control the generation of actinic radiation by the actinic radiation generator in response to the received information.

A device defined by claim 32 comprising an actinic radiation detector arranged to generate actinic radiation power information indicative of the power of the generated actinic radiation by detecting at least some of the actinic radiation when so generated, the actinic radiation detector being further arranged to communicate the actinic radiation power information to the controller for controlling the generation of the actinic radiation.

A device defined by claim 33 wherein the controller is configured to control the generation of actinic radiation such that the received actinic radiation power information satisfies a predetermined condition.

35. A device defined by claim 33 wherein the predetermined condition comprises the actinic radiation power information is equal to a predetermined value.

36. A device defined by any one of the claims 32 to 35 comprising a radiation spatial modulator arranged to spatially modulate the actinic radiation when so generated .

37. A device defined by claim 36 wherein the controller is arranged to temporally coordinate the radiation spatial modulator with the actinic radiation

generator .

38. A device defined by any one of the claims 32 to 37 arranged to form a plurality of layers, wherein the device is arranged to generate less actinic radiation in a first temporal period between a second temporal period, in which one of the plurality of layers is formed, and a third temporal period, in which another one of the plurality of layers is formed.

39. A device defined by claim 38 wherein the device is arranged to not generate the actinic radiation during the first temporal period.

40. A device defined by any one of the claims 32 to 39 wherein the actinic radiation generator comprises at least one of a light emitting diode (LED) , a laser and a lamp.

A device defined by any one of the claims 32 to 40 wherein the controller is arranged to control a current powering the actinic radiation generator.

42. A device defined by claim 41 wherein the controller comprises a current modulator arranged to modulate the current .

43. A method for making an object, the method comprising the steps of:

receiving a material responsive to an actinic radiation;

receiving information;

generating the actinic radiation, the generation being controlled in response to the received

information; and

illuminating the material with the actinic radiation .

44. A method defined by claim 43 comprising the step of generating actinic radiation power information indicative of the power of the generated actinic radiation by detecting at least some of the actinic radiation when so generated, and communicating the actinic radiation power information for controlling the generation of the actinic radiation.

45. A method defined by claim 44 comprising the step of controlling the generation of actinic radiation such that the received actinic radiation power information satisfies a predetermined condition.

46. A method defined by claim 45 wherein the predetermined condition comprises the actinic radiation power information is equal to a predetermined value.

47. A method defined by any one of the claims 43 to 46 comprising the step of temporally coordinating a radiation spatial modulator arranged to spatially modulate the actinic radiation with the generation of the actinic radiation.

48. A method defined by any one of the claims 43 to 47 comprising forming a plurality of layers, wherein less actinic radiation is generated in a first temporal period between a second temporal period, in which one of the plurality of layers is formed, and a third temporal period, in which another one of the plurality of layers is formed.

49. A method defined by claim 47 wherein no actinic

radiation is generated in the first temporal period.

50. A method defined by any one of the claims 43 to 49 wherein the step of generating the actinic radiation comprises the step of using at least one of a LED, a laser and a lamp to generate the actinic radiation.

51. A method defined by any one of the claims 43 to 50 comprising the step of controlling a current powering an actinic radiation generator generating the actinic radiation .

52. A method defined by claim 26 wherein the step of

detecting a sample of the actinic radiation with a radiation detector comprises switching the majority of pixels of a spatial light modulator to a substantially off state.