JP3349508B2 - Calibration device and calibration method for three-dimensional modeling device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Cross Reference of Related Applications This application is filed with United States Patent Application Serial No.
182,823, 182,830, 183,016, 183,015,
Nos. 182,801, 183,014, and 183,012, all of which are incorporated herein by reference in their entirety. U.S. Patent Applications Nos. 182,830, 183,016, 183,014, and 1st
A continuation-in-part of No. 83,012 was filed on November 8, 1988,
The entire contents of which are incorporated herein by reference. The application numbers of the partial continuation applications are respectively:
(About No. 182,830) No. 269,801, No. 268,806,
No. 268,337, No. 268,907, (About No. 183,016)
No. 268,429, (No. 183,014) No. 268,408,
And (about No. 183,012) No. 268,428. A continuation application of US Patent Application No. 269,801 is March 31, 1989.
Filed on December 5, the entire contents of which are incorporated herein by reference. The Lyon & Lyon case reference number of the continuation application is 186/195.

2. Other References The entire contents of the following two manuals are incorporated herein by reference.

-3D Systems, November 1987, Beta Site User's Manual and Service Manual.

-3D Systems, October 1987, Beta Release, first draft software manual.

In addition, the following appendix is attached to this specification, and the contents of this appendix are also included in the disclosure content of this specification.

Appendix A: Software vendors other than 3D Systems, as of April 13, 1988.

3. FIELD OF THE INVENTION The present invention relates generally to an apparatus and method for measuring and controlling a beam of electromagnetic radiation or a beam of particles, and more particularly to measuring the intensity profile of a beam, The present invention relates to a new device and a new method for controlling a beam based on the measurement result, and also to a related application related to manufacturing of a three-dimensional object by three-dimensional modeling.

4. Background of the Invention Recently, "solid modeling" systems have been utilized as described in U.S. Patent No. 4,575,330 entitled "Apparatus for manufacturing three-dimensional objects by solid modeling". The disclosure of U.S. Pat. No. 4,575,330 is incorporated herein by reference in its entirety. Basically, three-dimensional modeling is a continuous printing of complex plastic parts by laminating sections with photopolymerizable liquid or similar until all of its thin layers are joined together to form the entire part. This is a method for automatically forming. In this technique, the parts are literally grown from within a container containing liquid plastic. This manufacturing method is very effective for quickly bringing a design idea into a physical form and for manufacturing a prototype.

Photopolymerizable liquids (photopolymers) change from a liquid to a solid in the presence of light, and their rate of photopolymerization under ultraviolet light (UV) is fast enough to be a practical model building material It is. When making parts, the non-polymerized material is still usable and remains in the container, and the parts are made continuously. Ultraviolet lasers are used to generate small, intense beam spots of UV light. This beam spot is moved over the surface of the liquid by a scanning device of the XY axis reflecting mirror type using a galvanometer mirror. The scanning device is driven by a computer that generates vectors or the like. Precise and complex models can be produced quickly with this technique.

The lasers, scanners, containers for photopolymerizable liquids, and elevators used with the control computer are described in the SL
It is configured to form a three-dimensional modeling device called "A". SLAs are programmed to automatically produce plastic parts by "drawing" one cross section at a time and layering them one by one.

Stereolithography is an unprecedented new way to quickly create complex or simple parts without tools.

Since this technique relies on the use of a computer to generate the cross-sectional pattern, there is necessarily a data link to CAD / CAM.

In order for 3D modeling to be effective, this system
Focus, laser beam oscillation mode, beam power, intensity distribution or intensity profile, and laser scanning for writing, in order to carry out precise and effective manufacturing of parts (objects made by 3D modeling are called "parts") You need to have information about the displacement of the system over time. The beam must be relatively focused on the surface of the photopolymerizable liquid. Laser mode, intensity distribution, and beam power, as well as scan speed, are important factors that determine the cure depth and width of the working medium. The "time shift" of the scanning system must be checked and corrected periodically.

The beam profile (beam intensity profile) measurement has useful information about the beam because it can help achieve the following objectives:

1. Focus the optical system and correct aberrations such as astigmatism.

2. Measurement of beam power (performed daily).

3. Check the laser mode and change the mode.

4. Correction for positional deviation of laser scanning system over time.

5. Record the positional deviation over time for later analysis of the changes.

6. Automatically calibrate the scanning device.

7. To be able to easily control the position of the beam spot to perform other measurements (eg, separately measuring the beam power to find a calibration factor for the power of the system).

8. Be able to predict the size and shape of cured traces of cured plastic.

Accordingly, devices and methods for rapidly determining a beam profile to calibrate and standardize a stereolithography device and to correct for changes over time of a reflective mirror positioning system of the stereolithography device, particularly to a stereolithography device What you need is needed.

SUMMARY OF THE INVENTION Briefly and generally speaking, the present invention provides a new and improved apparatus and method for performing beam profile measurements. The apparatus includes a sensor means for measuring the intensity of a portion of the beam when the beam impinges on the sensor means, and the entire beam along a surface substantially perpendicular to the optical path followed by the beam. Or means for changing the vertical position of the sensor means with respect to the optical path followed by the beam in order to measure the intensity of a part thereof. A method for measuring a beam profile includes measuring the intensity of a cross-section of a beam of a preselected size along a surface substantially perpendicular to an optical path followed by the beam, and measuring the intensity of the beam along the surface. By repeating the measuring step for the other part.

The apparatus and method creates an intensity map of the beam along a surface substantially perpendicular to the optical path followed by the beam. The intensity map indicates the intensity for each preselected magnitude portion of the beam cross section. The intensity profile obtained in this way can be used not only to calculate the beam power (the conversion to beam power is known), but also to determine and adjust the focus of the beam. The beam profile can be used to predict the cure depth and width of the plastic created on the working medium. The beam profile measurement device acts as a fixed reference point and can be used to detect "time offset" of the beam scanning device by determining the scanning device coordinates of the beam center. The device also recalibrates a positioning "map" or table that determines the orientation of the scanning device in transforming the computer-generated design into the actual dimensions on the liquid surface that cures for object formation. Can be used for

This preferred form of the beam profile measurement system has significant economic advantages. This is because the system uses a computational system and a light beam positioning system already built into the stereolithography machine.

While current systems refer to "laser beam systems" and "XY galvanometer mirror scanning systems", other possible systems having different energy sources or positioning means or combinations thereof have each of the above advantages. It is clear that it can be applied.

The present invention provides a new and improved apparatus and method related to standardization and calibration of a three-dimensional printing apparatus.

In an apparatus for producing parts by stereolithography, the emission of the reaction means (laser beam according to the preferred embodiment) of the working medium (designated surface with the photopolymerizable liquid according to the preferred embodiment) is specified. There is a need for devices and methods for optimizing and calibrating. Precise positioning of the reaction means in the working medium is easy according to the invention, which comprises at least one which can be located at a predetermined position on a plane defined by a specified surface of the working medium. This is possible by installing a sensor. The sensor detects the presence of the reaction means. A storage means is provided for storing other information, including positioning information, which causes the responsive means to be accurately directed towards the sensor. According to a preferred embodiment, the stored look-up table or stored reference map is populated with specific positioning information for each of a number of specific locations on the working medium surface. Standard linear interpolation techniques are used to determine the positioning information and are useful in directing the responsive means in the direction of each position falling between each position in the look-up table.

Accordingly, an object of the present invention is to provide an apparatus and method for accurately calibrating and standardizing a three-dimensional printing apparatus.

It is still another object of the present invention to provide an improved and more precise method and apparatus for beam positioning.

It is also an object of the present invention to provide a related new and improved apparatus and method for correcting the positional displacement of a reflective mirror type positioning system over time to provide improved precision and repeatability. .

A three-dimensional object, or "part", can be made from a medium that can be exposed and cured by a stereolithography device to a reaction means that is operated in a preselected manner on a designated surface of the medium. In this manner, successive adjacent thin layers of cured media forming the part are stacked.

Thermal effects, abrasion effects, and other effects can shift the position of the positioning means for positioning the reaction means over time, so that the reaction means is no longer repeatedly directed to the same location. . To mitigate such displacement over time, the present invention employs at least one sensor means capable of detecting the application of a responsive means to the sensor means. The sensor means is installed at a predetermined location fixed to the surface of the set medium. The positioning means can position and apply the reaction means at an appropriate location, and can apply the reaction means to the sensor means. The means for outputting the sensor position for viewing provides information on the sensor position for viewing, indicating the position of the sensor means as viewed from the responding means when the responding means is applied to the sensor means. Similarly, storage means is used to contain past sensor position information, including the previous viewing position of the sensor means. The present invention also includes a comparison unit for comparing the current sensor position information with the past sensor position information, and the comparison unit removes the effect of the positional deviation of the pointing position of the reaction unit with time, thereby setting the positioning unit. It has the ability to determine the correction of the misregistration over time, which is needed to adjust.

The above and other objects and advantages of the present invention are:
The following more detailed description, taken in conjunction with the accompanying drawings of illustrative embodiments, will become apparent.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1, FIG. 2, and FIG. 3 are flow charts illustrating the basic concept used when carrying out the three-dimensional modeling method.

FIG. 4 is a combination of a block diagram and a schematic vertical sectional view of a three-dimensional printing system.

 FIG. 5 is a block diagram of a three-dimensional printing system.

FIGS. 6, 7A and 7B are exploded perspective views of the main components in the three-dimensional printing system.

FIG. 8 is a perspective view of a laser and optical system of a stereolithography system using a preferred embodiment of the present invention.

FIG. 9A is a schematic sectional view of a beam profile measuring sensor according to a preferred embodiment of the present invention.

FIG. 9B is a top plan view of a pinhole plate of the sensor for measuring a beam profile according to the preferred embodiment of the present invention.

FIG. 10 is a block diagram showing an apparatus according to a preferred embodiment of the present invention.

FIG. 11A is a functional block diagram of a preferred embodiment of the method for generating a beam intensity profile according to the present invention.

FIG. 11B is a functional block diagram of a method of moving a beam when performing the method described in FIG. 11A.

FIG. 11C is a functional block diagram of a method for reading the intensity of a part of the beam when performing the method described in FIG. 11A.

FIG. 12 is a functional block diagram illustrating processing and analysis that can be combined with the method described in FIG. 11A.

FIG. 13 is a chart showing a sample of the intensity profile of the beam generated by the preferred embodiment of the present invention.

FIG. 14 shows a profile of expected cure depth along two axes generated from beam profile information according to a preferred embodiment of the present invention.

FIG. 15 depicts a cross section of a cured mark of a photopolymerizable liquid cured by exposure to a beam.

 FIG. 16A shows a perspective view of the calibration plate.

 FIG. 16B shows a cross-sectional view of the calibration plate.

FIG. 17 illustrates the main steps of the three-dimensional modeling process.

FIG. 18 shows a software diagram of the three-dimensional printing system.

19a-19b illustrate switches and indicators on the control panel.

 FIG. 20 shows a sample part record.

 FIG. 21 shows a sample of the action curve.

Figures 22a-22e illustrate a recommended method for cleaning optical equipment.

FIG. 23 illustrates the replacement of the air filter.

Figures 24a-24b show the components of a SLICE computer.

Figures 25a-25b show the components of an electronic cabinet.

 Figures 26a-26c show the optical system components.

 FIG. 27 shows the components of the chamber.

 Nos. 28a-28b show the arrangement of laser resonators.

 Figures 29a-29b show the alignment of the optical system.

 FIG. 30 shows the alignment in the chamber.

FIG. 31 illustrates an SLA-1 type three-dimensional printing system.

Figures 32a-32b show an assembly of an electronic cabinet.

 FIG. 33 shows an optical instrument assembly.

 Figures 34a-34b show the assembly of the chamber.

 FIG. 35 shows an SLA-1 type wiring diagram.

Figures 36a-36f show a geometric model of a car that can be input to SLICE.

Figures 37a-37c show that all triangles included in the geometric model belong to one of three types: planar triangles, near-plane triangles, or scanning triangles.

FIG. 38 shows how SLICE ranks triangles by type and height.

Figure 39 shows that the scanning triangle is SL
Shows how ICE ranks.

Figures 40a-40b illustrate how SLICE stacks individual thin layers to represent a model, and how to "skin-fill" triangles that are close to plane, and plane triangles. It is an illustration of how.

FIG. 41 shows how individual thin layers are formed by skin-filling or hatching the area between the boundaries.

Figures 42a-42b show how SLICE creates a trapezoid for a triangle that is close to a plane.

FIG. 43a shows why SLICE does not create a trapezoid for a planar triangle.

FIG. 43b shows how SLICE generates only a boundary for a scanned triangle (after which the boundary is hatched).

Description of the Preferred Embodiment The stereolithography system in which the apparatus and method of the preferred embodiment of the present invention are used, is capable of performing its physical A three-dimensional object is created by creating a cross-sectional pattern of the object formed on a selected surface of a liquid medium, such as a UV curable liquid, that has the ability to change states. The successive contacting laminae corresponding to the continuous cross section of the object are automatically formed and joined, resulting in the shaping of the object consisting of a stepped lamina. Thereby, a three-dimensional object is formed and grown from a substantially superficial or plate-like plane of the liquid medium throughout the forming process.

The general nature of this technique is illustrated by the flow chart of FIG. 1-5 and the drawings.

FIG. 4 is a vertical sectional view of the three-dimensional printing system. The container 21 contains a UV curable liquid or equivalent and has a designated work surface 23. A programmable light source 26 of ultraviolet light or the like illuminates a plane 27 of the surface 23 with a spot 27 of ultraviolet light. The spot 27 is surfaced by the movement of a reflecting mirror or other optical or mechanical element (not shown in FIG. 4) used with the light source 26.
It is movable over 23. The position of spot 27 on surface 23 is controlled by computer control system 28. This system 28 is a CA created by the data generator 20 that is a CAD design system or equivalent and sent to the computerized conversion system 21 in PHIGS format or equivalent.
Controlled by D data. Computerized conversion system 21
Is to process information defining an object so as to reduce stress, curl and distortion, and to increase resolution, strength and reproduction accuracy.

A movable lift table 29 inside the container 21 can be selectively moved up and down, and the position of the table is controlled by a system 28. When this device is operated, 30a, 30b, 30c
A three-dimensional object is created in steps by combining
30 is generated.

The surface of the UV curable liquid 22 is maintained at a constant level within the container 21 and is exposed to a spot of UV light or other stimulus of sufficient intensity to cure the liquid and convert it to a solid material. Move over the work surface 23 according to a programmed method. When the liquid 22 has hardened to form a solid material, the elevator 29, which was initially just below the surface 23, is lowered from the surface in a programmed manner by some suitable drive. In this way, the initially formed solid material is lowered below the surface, and a new liquid 22 flows over the surface 23. A portion of this new liquid is converted into a solid material by the sequentially programmed spots of UV light 27, and the new material integrates to adhere to the underlying material.
This process continues until the three-dimensional object 30 is completely formed. The object 30 is then removed from the container 21 and the device is ready to make another object. At this point, the next object can be made, or a new object can be made by modifying the program on computer 28.

The light source 26 of the stereolithography system according to a preferred embodiment of the present invention is typically a helium-cadmium ultraviolet laser, such as a 4240-N, HeCd multi-mode, manufactured by Reconix, Inc.
There is a laser.

Commercially available stereolithography systems will have additional components and sub-systems in addition to the apparatus schematically illustrated in FIGS. 1-5. For example, commercially available systems are:
It will have a frame, storage and control panel. Also, means should be provided for shielding the operator from extreme UV and visible light, and it is possible to provide means for observing the object 30 while it is being formed. Commercially available equipment is also provided with safety measures to remove ozone and harmful poisons, in addition to the usual high pressure security and interlocks. Some commercially available devices will have means for the purpose of effectively protecting sensitive electronic equipment from electronic noise sources.

Commercially available SLAs are self-contained systems that interact directly with the user's CAD system. A commercially available SLA containing a preferred embodiment of the apparatus of the present invention is shown in FIGS. 6-7 and comprises four main components. A SLICE computer terminal, an electronic cabinet assembly, an optical system assembly, and a chamber assembly. FIG. 5 is a block diagram of a commercially available SLA.

The electronic cabinet assembly includes a processing computer, a keyboard, a monitor, a power supply, an AC power distribution board, and a control board. The computer assembly includes a terminal control plug-in type circuit board, a high-speed scanning reflection mirror, and a vertical (Z stage) elevator. The laser power supply, dynamic mirror, and elevator drive are located at the bottom of the cabinet.

The control panel is provided with a power switch and a display, a chamber light switch and a display, a laser operation display, and a shutter open display.

Operation and maintenance parameters include fault diagnosis information and laser function information and are usually displayed on a monitor. All operations are performed on the keyboard. Work surfaces around the keyboard and the computer are covered with hormica (common name of surface finishing material) or the like to maintain cleanliness and long life.

FIG. 8 below shows that a helium-cadmium (HeCd) laser 100 and optical components are installed on top of an electronic cabinet and chamber assembly 102. The base with the laser and optical components
By removing the separated cover, access for service is possible. For safety reasons, a special tool is required to unlock the cover lock, and when the cover is removed, the interlock switch operates. The interlock activates a solenoid controlled shutter to block the laser beam, regardless of which cover is removed.

As shown in FIG. 8, a shutter assembly 104 and two 90-degree beam redirecting mirrors 106 and 1 are provided on the optical system base.
08, beam expander 110, XY axis scanning mirror assembly 1
12, and a precision optical window 114 is provided. A rotary solenoid driven shutter is located at the laser output and rotates to block the beam when the safety interlock is opened. 90 degree beam redirecting mirrors 106,108
Reflects the laser beam towards the next optical component. The beam expander 110 expands the laser beam and focuses on the liquid surface. The fast scanning mirror directs the laser beam at a vector on the resin to be traced. A two-axis galvo mirror scan head with two mirrors is available from General Scanning, Watertown, Mass., And has been found to be sufficient for this purpose. In a preferred embodiment, the DX-2005 servo, XY
A type-0507 galvanometer mirror XY scanning head was used.
The quartz window 114 between the optical container and the reaction chamber
Only the laser beam is passed into the reaction chamber and the others isolate the two regions.

In the chamber assembly, there is an environment-conditioned chamber in which a table, a resin container, a lift, and a sensor for measuring a beam profile are installed.

The chamber for forming the object is designed in consideration of the protection of the operator and to maintain a uniform operation state. The chamber was warmed to about 40 ° C (104 ° F) and air was circulating through the filter. Ceiling lights illuminate the resin container and work surface. An entrance door interlock activates a shutter to block the laser beam when the door is opened.

The resin container is designed with minimal handling of the resin. The resin container is mounted in a chamber on a guide for aligning the resin container with an elevator and a table.

The object is formed on a vertical axis elevator, ie, a table mounted on a Z stage. The table is immersed in a resin container,
It is adjusted so that it gradually descends while the object is being formed. To remove the formed article, raise the part to a position above the container. Thereafter, the platform is disconnected from the elevator and removed from the chamber for the next step. Usually, a processing dish is used to receive resin spills.

Two beam profile measurement sensors 116 and 118 according to a preferred embodiment of the present invention are installed on both sides of the resin container, and the focus of the laser optical system is adjusted to match the sensor position (ie, a galvanomirror). The same distance as the distance from the scanner to a point 0.3 inches (about 0.8 centimeters) below the liquid surface is mounted as the radial distance from the galvanometer mirror scanner;
(See FIGS. 7A-7B). The scanning mirror is periodically commanded to direct the laser beam over a beam profile measurement sensor that measures the intensity profile. The intensity data is displayed on the terminal as a profile representing the intensity value or as a single number representing the overall (integrated) beam intensity. This information includes whether the reflector is clean and aligned, whether the laser is operating, whether the scanning mirror is displaced over time, and what parameter values determine the desired thickness and width. It is used to determine if a hardened vector can be obtained.

The beam profile measuring sensors 116 and 118 are installed at symmetrical positions with respect to the center of the resin container (see FIG. 7A). Although not necessary, it is desirable that these have the same coordinates (with opposite signs) in the X and Y directions with respect to the container center. In other words, they are on the diagonal of the 3D modeling device. The coordinates in the X direction and the Y direction based on the center of the container will be described below.
It will be referred to as “offset value”. In FIG. 7A,
Beam profile measurement sensors 116 and 118 are shown in the corner of the chamber assembly. The distance from the second scanning mirror on the optics base above the chamber assembly to the aperture of each beam profile measurement sensor is the focal length of the desired distance between the liquid and the scanning mirror plus a small increment. be equivalent to. Hereinafter, a focal length obtained by adding a slight increment to a desired distance between the liquid and the scanning mirror is referred to as an “optically equivalent distance” as the distance between the liquid and the scanning mirror. In the SLA-1 sold by 3D Systems (shown in Figures 6, 7A and 7B), the distance from the scanning mirror to the liquid is about 27 inches (about 69 centimeters), with a slight increase in the above. Is 0.3 inches (about
0.8 cm). Therefore, the focal length is about 27.
3 inches (about 69.8 cm). Separating the sensors 116 and 118 for measuring the beam profile from the second scanning mirror by an optically equivalent distance to the photopolymerizable liquid may be associated with a designated surface of the photopolymerizable liquid in the SLA-1 resin container. Has the effect of detecting the best average focus image. When the photopolymerizable liquid is at the desired level at the center of the resin container, the focal length of the laser beam will be 0.3 inches (about 0.8 centimeters) below the surface of the photopolymerizable liquid. The beam focus image in the photopolymerizable liquid at the center of the resin container does not change much. SLA-1
The focal length at the corner of the 12 inch resin container is about 1 inch (about 2.5 centimeters) above the surface of the photopolymerizable liquid. The focal length is on the surface of a circle with a radius of 4.2 inches (about 10.7 centimeters) around the center of the photopolymerizable liquid surface. The arrangement of the sensor for measuring the beam profile at the focal length is intended to obtain an optimal beam profile, taking into account that the surface of the photopolymerizable liquid is usually not at the focal length of the laser.

FIG. 9A is a cross-sectional view of a beam profile measuring sensor 35 of a preferred embodiment of the apparatus according to the present invention, and FIG. 9B is a top plan view of a pinhole plate used in the beam profile measuring sensor. The beam profile measuring sensor includes a stainless steel sheet 40 in which four pinholes (passages) 45 of different sizes are etched. The diameter of these pinholes in the preferred embodiment is 0.0005 inches, 0.001 inches, 0.002 inches, and 0.004 inches (about 0.01 millimeter, about 0.03 millimeter, about 0.05 millimeter, and about 0.1 millimeter). Each pinhole passes a small amount of laser beam 50 incident on the pinhole to reach a photodetector 55 below the thin steel plate 40. The purpose of providing several pinholes is to enable profile measurement of a beam with a wide range of incident power. One pinhole is dedicated to measuring the intensity profile of a beam with a given incident power. The helium-cadmium laser used in SLA-1 has a diameter of 2
It has been found that a single pinhole in the mill (approximately 0.03 mm) satisfies the purpose. The beam is scanned along X and Y columns of the selected pinhole to form a two-dimensional profile of beam intensity.

As shown in FIG. 7A and particularly FIG. 9A, the beam profile measuring sensor 35 has two storage sections 60. The light beam 50 enters from the right side of FIG. 9A and moves toward the left side. In order to prevent the beam profile measurement sensor from colliding with the resin container when the resin container enters or exits the assembly section of the chamber, the beam profile measurement sensor is installed at a corner of the assembly section of the chamber. (See Figure 7A).

Returning to FIG. 9A, the beam profile measurement sensor 35
Is comprised of two separate storage sections 60, a pinhole plate 40, and an ultraviolet transmission filter 70, which absorbs visible light and prevents false readings due to visible light. Filter 70 is a 2 millimeter thick filter glass of the Schott YG-11 type, which has been found to meet this purpose of the preferred embodiment. This filter has adequate transmission characteristics in the wavelength range of 300-310 nanometers, and has very low transmittance at other wavelengths. A one millimeter thick filter material of the type HOYA U-350 also meets the purpose.

Below the filter 70 in the housing is a photodiode sensor 55, which detects ultraviolet light passing through the filter 70 from the pinhole 45. EEG Vactec, VTS3
It has been found that a type 072 super blue enhanced photodiode is suitable for this purpose. The output from the photodiode is sent to a current-voltage amplifier (not shown). OP07 type current-voltage amplifiers are well known to those skilled in the art and have been found to be usable for this purpose.

Pinhole plate for beam profile measurement sensor 35
40 is covered with a quartz filter (not shown). The quartz filter is cleanable and protects the beam profile measurement sensor from dripping of dust and photopolymerizable liquid. The quartz filter should be coated to prevent internal reflections and prevent false shape measurements when the light sensor is not perpendicular to the beam. Optionally, a light diffuser (not shown) can be used between the pinholes. This is to assist the filter and prevent damage to the optical components.

FIG. 10 is a block diagram showing an apparatus according to a preferred embodiment of the present invention. Essential to this invention is a computer for control and analysis. The computer can receive an input from a program, a keyboard, or the like, and display the result via a printer, a terminal, or the like.
The control and analysis computer transmits mirror positioning instructions to a mirror positioning system that adjusts the XY scanning mirror. The laser beam is focused by the optics shown in FIG. 8 to reach the XY scanning mirror,
These mirrors point to one of the sensors for measuring the beam profile. For the purpose of correcting misregistration over time, it is recommended to use two sensors for measuring the beam profile. The signal from the beam profile measurement sensor is converted into a signal that can be read by a computer. This signal is then processed as described below.
Returned to control and analysis computer.

Physically speaking, the beam profile measuring method according to the present invention moves a beam to each array point of the pinhole plate centered on the optimal known position of the pinhole. As a result, different regions of the beam illuminate the pinhole, are transmitted through the pinhole, are detected by the photodiodes, and are converted into numerical signals that can be analyzed by a computer. Intensity profiles for different areas of the beam are generated by a computer (see FIG. 13). This is the "intensity profile" of the beam.

FIG. 11A is a functional block diagram showing a method for creating a beam profile according to a preferred embodiment of the present invention. The best known position of the pinhole on the beam profile measurement sensor is retrieved from memory by the control and analysis computer and transmitted to the mirror positioning system to position the XY scanning mirror to direct the beam to this best known position. Is done. Through the beam positioning system, the control and analysis computer moves the beam to the first column in the first row of a rectangular array of points centered on the best known location. Thereafter, the intensity of the portion of the beam incident on the pinhole detected by the beam profile measurement sensor is read and stored along with a mirror positioning instruction associated with the intensity. next,
The beam is moved from beginning to end of an array point on a particular row or column, and the steps of reading and storing intensity values are repeated. The column or row array is then moved from beginning to end, and the move and read steps are performed for each column or row.

As a result, a beam intensity reading will be made for each position on the array ("position" is known to the computer as a set of mirror positioning instructions). Control and analysis of the array of intensity values A standard analysis performed by a production computer is generally performed to generate a new optimal known position of the pinhole (to be used next time to process the first stage of the profile scan). This is done irrespective of the detailed function actually being analyzed (see Fig. 12.) According to this method, the calculated optimal known position is very accurate and the pinhole size It has been found that much higher accuracy can be obtained, and if the appropriate number of locations are found and stored, the control system will move the beam to these locations, or some intermediate location. To can use these values to the linear interpolation of 2 axes type.

FIG. 11B is a functional block diagram for implementing the beam moving method and the method described in connection with FIG. 10A. The first step in moving the beam is to transmit beam positioning information about the desired location to the XY scanning mirror servo mechanism. The servo mechanism (either analog or digital) then sends a signal to the mirror driver to position the XY scanning mirror at the new location. The servo mechanism of the XY scanning mirror measures the actual position of the mirror driver, compares the actual position with the desired position, and adjusts the drive signal appropriately. Adjustment is continued within the specified values for the desired location.

FIG. 11C is a functional block diagram illustrating a method for reading beam intensity and a method for performing the method of the preferred embodiment of the present invention. The first step is to convert the total amount of light passing through the pinhole into a signal proportional to the amount of light. In a preferred embodiment, this step is performed by a photodiode that measures the light incident through the pinhole and the filter. The current from the photodiode is transmitted to a current-to-voltage amplifier that generates a signal proportional to the amount of light received by the photodiode. Amplifying the signal (which is proportional to intensity) to provide a wide range of measurements is important for obtaining small but sufficient readings for the beam edges that would otherwise be missed.

The next step is to measure a signal proportional to the amount of received light after this signal has been converted to a digital form for numerical analysis.

FIG. 12 is a functional block diagram illustrating the steps and analysis, and this analysis is related to the method described in FIG. 11A. As shown in this figure, various steps and analyzes can be selected from the menu, the first five of which are the eleventh.
The profile scanning routine shown in FIG. The first step is to scan the beam intensity profile according to the method described in FIG. 11A. The intensity profile can be displayed in numerical or graphical form. Optionally, the power can be calculated from the intensity profile as well as the new optimal known position of the pinhole used. Another possible step is to add the data generated in connection with the beam intensity profile to the history file and provide an option for displaying the history file. An additional possible step is to generally also scan a second, separate sensor (in the preferred embodiment, another sensor for measuring the beam profile) to calculate the displacement information over time of the mirror positioning system. Then, an offset value and a gain value relating to the temporal displacement are calculated and displayed. Another step is to calculate and display the beam power, including summing the profile intensities and multiplying by the power conversion factor.

The power conversion factor can be determined, for example, using a process with a beam of known power or by comparing the calibrated sensor power with the calculated power to determine the required power magnification. It is.
Other features include calculating and displaying focus information, which may be due to the option of utilizing a special transformation of the intensity data used to calculate the focus information, It may be based on the use of known resin properties to predict the shape and size of the cure mark. Other possible functions include moving the beam to a desired location for start-up (to make a part), testing, etc., where the option to search for a sensor from a new location or scan a profile is provided. It is also possible. A useful function is to search for sensor pinholes in a spiral motion reading mode. This may be necessary if the best known location of the pinhole is not accurate, i.e., if the trace of the array is going past the best known location of the pinhole. The next step is to verify (by pinhole location) by testing or profile scanning. Yet another feature is to use a sensor for beam profile measurement for calibration, which involves making a measurement of misregistration over time while obtaining a calibration diagram for a surface corresponding to the surface of the photopolymerizable liquid. . The last function is to store variables such as optimal known location, scale factor, resin properties, etc. in the computer.

FIG. 13 is a sample diagram of an intensity profile of a laser beam according to a preferred embodiment of the present invention. That number corresponds to the beam intensity measured from the preferred embodiment of the present invention. Numerical values are converted to integers for easy reading of the display.

The intensity profile generated by the present invention can be used to calculate beam power and to determine the shape of the cured trace of the photopolymerizable liquid (the photopolymerizable liquid solidified by exposure to a beam of UV light). Used to predict size. The results of the study are described below.

Beam intensity is measured with a beam profile measurement sensor when the beam is directed at each of the arrays on the pinhole plate, which is generally in a plane perpendicular to the beam path. The X and Y directions on this surface correspond to the directions in which the beam moves as one or more scanning mirrors rotate.

The coordinates of the array in the X and Y directions are each from 1
i max, and 1 to j max. (Generally, i max and j max
Is 22).

Generally, a beam moves from point to point in the array with a transit time much shorter than the time the beam spends at a point. The interval between points is: S (mm) = scan step / scale factor [1].

The scanning step is typically 4 "bits" and the scaling factor is typically 140 bits / mm. Each of the scanning mirrors can obtain 65535 (64K) different positions with a light beam rotation of 40 degrees. This means, in other words, that one bit along the X or Y axis corresponds to a rotation of 6.104 × 10 ^-4 degrees. Since the distance from the mirror to the liquid surface is about 27 inches (about 69 centimeters), this rotation angle is 2.875 × 10
^-4 inches (7.303 × 10 ^-3 mm), or 137 equivalent
Bits / mm, or about 140 bits / mm.

The area of the array needs to span the entire beam (because it creates the most information about the beam, as well as the measurement of the entire beam is needed for beam power calibration). Also, a sufficient number of points is needed to resolve the desired beam profile. Generally, the spacing between each point in the array is less than one tenth of its beam width. The diameter of the pinhole should be smaller than this resolution limit.

An "element" is the portion of the beam measured when the beam is directed at a point (m, n) in the array. Each element (m, n) takes an intensity reading I (m, n). The letters m and n mean the positions in the X and Y directions in the array, that is, the array points. FIG. 13 shows the intensity readings in the array just discussed.

The beam power is measured separately and the power calibration factor K
Is derived from the following equation:

The power calibration factor K applies only to the selected pinhole, measurement system, and laser wavelength. Individual power measurements must be performed on the beam after passing through the same number of optical surfaces on the beam path.
These calculations also assume that the background optical signal has been removed and that the amplification factor of the amplifier has been compensated.

The power / unit area in the element (m, n) is obtained by the following equation.

Intensity (at element m, n) = K × I (m, n) / S ² (Watts / mm ² ) [3] This is independent of whether the beam is stationary or moving. m, n) is the instantaneous intensity experienced by the small area.

If the beam travels uniformly along the Y axis at velocity V (mm / sec) and takes the same time as S / V to pass through each element, it is absorbed per unit area from element (m, n) The exposure energy is as follows.

Exposure of the element (m, n) = K × (I (m, n) / S 2) · (S / V) ( Joules / m
m ² ) [4] This is the exposure energy absorbed per unit area from a particular element (m, n) of the beam. The total beam exposure (absorbed beam energy) is as follows:

Exposure at m = K × ΣI (m, n) / S ² × (S / V) (joules / mm ² ) [5] Physically speaking, this equation uses the term element as described above, where the beam is the element 5 shows a state of traversing in the Y direction over a region having an area corresponding to the element size of the beam. The area intersects with each element of the beam having the X coordinate m, thus n
Changes from 0 to jmax, each region having an area of one element at each m is exposed over all the elements (m, n).

Although the calculations described above are based on individual elements, it is clear that integral values can also be used. The movement is assumed to be along the Y axis for convenience. Other angles can easily be determined, which is necessary if the beam is asymmetric.

 The speeds V corresponding to the variables SS and SP are as follows.

 V = (SS / scale rate) (SP / 100,000) (mm / sec) [6] where SS = step size (bits / step) Generally, the scale rate is 140 bits / mm.

SP / 100,000 = step period (second) (SP unit is the same unit as 10 microseconds). 1E6 = 1,000,000 is the conversion factor between joules / mm and joules / m ² or microjoules / mm ² .

Equations 5 and 6 show that the sensor or beam is Y
Z = 0 in a small area at position m when moving in the direction
Can be used in combination to calculate the total exposure (intensity output or energy) at the liquid (photopolymerizable liquid) surface represented by Ie, exposure at (m, Z = 0); Finally, the absorption of the beam penetrating the liquid can be corrected according to Beer's law.

E (m, Z) = E (m, o) × exp (−Z / λ) [8] where λ is the depth of penetration (mm) E (m, o) is the exposure of the surface E (m, z) is the exposure at a depth Z (mm) below the surface.

Since it can be assumed that the attenuation has no nonlinearity or time dependence with respect to absorption, it is simply represented by I (Z) = I (Z = 0) × exp (−Z / λ).

Obviously, the above calculations can be modified as appropriate, taking into account the deviations from the simplified situation for the absorption described above.

Photopolymerizable liquids have been experimentally shown to cure to a gel if the exposure is greater than the critical value Ec, and therefore the shape of the cured trace of the cured plastic for a given system will be Prediction is possible by calculating the trajectory of the point having Ec. Ec can be accurately and individually measured for each photopolymer. The "gel point" gives only the boundary between "cured part" and "uncured part", and the exposure gradient at the resin depth other than the depth boundary corresponding to Ec (related to the penetration depth)
Is ignored. The strength of the part is likely to be related to the higher exposure, so the absorption properties should be chosen to give the optimum (highest) cure gradient. Also, the slope or penetration depth limits the optimal effective resolution in the Z direction. This is because slight variations in exposure (such as line-to-line variations) cannot be avoided, thus resulting in varying cure depths according to this variation in exposure.

The cure depth Zc (m) for a given X position (m) is derived by the following equation.

Zc (m) = λ × ln (E (m, Z = 0) / Ec) [9] The beam profile measured with sufficient reliability and accuracy predicts the curing depth determined only by the chemical properties of the resin Used to do. FIG. 14 illustrates two examples of prediction along the X and Y axes, respectively. The profile function (m, Z) also allows the trace width to be predicted automatically as a function of depth (and "beam width" and "minimum surface angle" with appropriate changes). The formation and measurement of the "banjo top", i.e., cure marks cured by the beam to directly determine the shape and size of the cured photopolymerizable liquid, is only for checking. FIG. 15 shows a cross section of a test scan of a banjo top, which should be compared with FIG.

To display the predicted trace trace profile,
A transformation diagram of cure depth versus position is plotted for the beam.
The conversion rate for the distance across the beam is straightforward, simply one row (or one column, etc.) of the scan as dimension s, depending on the pixel or graphic display block
May be selected and obtained. At this time, the depth scale is λ / s pixels each time the exposure is multiplied by e. The only optional element is the depth zero, which is related to the exposure characteristic Ec in Equation 9 or the equivalent factor in Equation 7. The displayed effective depth is determined by the operating range of the intensity measurement system and whether the truncation at I (m, n) is above some suitable value near the noise level.

[Calibration and standardization]

As noted above, it is desirable to have an apparatus and method for calibrating the position of the reaction means with respect to the working medium in order to obtain improved precision and accuracy in the stereolithography device. The calibration procedure of the preferred embodiment of the present invention draws a "map" from the CAD space design,
It is possible to derive the instructions for the actual SLA.
In any automated modeling system, there are several sources of different errors that need to be corrected in the calibration process. This system has a pair of scanning mirrors in close proximity to each other, and if the simple map in CAD dimensions is left uncorrected for the mirror angle, needle-like distortion will result. This is because the system also models a flat surface extending far from a point on the surface closest to the mirror, so that a uniform increment of angle will project onto that surface as a progressively larger distance. Because. This is a major distortion in the system, but it is possible to make geometric predictions so that the correction can be calculated. However, there are many other errors and distortions that need to be corrected, many of which are not easily predictable.

The calibration and normalization of the present invention is used in a wide range of applications and systems, and allows the translation of CAD positions into commands that are sent to a scanning system to draw a designated pattern on a work surface. A reference table is created automatically.

The term "normalization" can be used to indicate that more than one dimension is corrected at a time, while "calibration" is a term that provides a single correction rate for a system. Has a meaning outside. The device in the preferred embodiment has a single position sensor (sensor for measuring the beam profile), which moves automatically for each array of positions on the work surface, and then for each of these positions Record the substantial mirror positioning instructions needed to reach. In another preferred embodiment, a rectangular calibration plate with two-dimensionally arranged sensor pinholes is used to eliminate the need for sensor movement. In another preferred embodiment, a calibration plate is used in which the sensor pinholes that need to move only along a single axis are arranged linearly (one-dimensionally).

16A and 16B illustrate a rectangular calibration plate 200 of the preferred embodiment of the present invention. The UV-opaque metal coating 206 is 1/8 inch to 1/4 inch thick (approximately 3.2mm
(Approx. 6.4 mm) to a substrate 204 made of the preferred material of quartz or Pyrex. In a preferred embodiment, 49 × 49 pinholes 202 arranged two-dimensionally are etched on the UV opaque metallization 206 at 1/4 inch (about 6.4 mm) intervals. The diameter of each etched pinhole is 0.004 inches ± 0.0005 inches (approximately 0.1 ± 0.01
mm), but it is very important that the pinhole diameter be smaller than the diameter of the beam projected on the calibration plate to achieve the best resolution. A sensor (not shown) is mounted below the calibration plate and is positioned so that, when the calibration plate is used, it is located at a precise location relative to the working medium surface.

In a preferred embodiment of the present invention, two-dimensionally arranged 5.times.5, or 25, UV light sensing photodiodes
208 is used with the calibration plate.

In this preferred embodiment, the light that enters the pinhole is the light entering the pinhole because the UV light only enters the calibration plate through one of the pinholes and the calibration plate material tends to diffuse the incoming light. Spreading horizontally beyond the exact location of the pinhole, the 25 sensors described above are sufficient to cover an area of 49x49 pinholes.

Typical calibration procedures can be performed before shipping the SLA to the customer and after the mirror control system has been subjected to physical trauma that could invalidate the SLA calibration.

The actual calibration procedure uses a beam profile measurement methodology similar to that for obtaining the “optimal position” of a pinhole from the center position of the scan data.

The new “optimal position” is defined for each pinhole in the case of a square calibration plate with pinholes arranged two-dimensionally, and for each row of pinholes in the case of a calibration plate with pinholes arranged linearly. If the sensor is located at a preset location, it is determined for each preset location. Scanning each pinhole to find the look-up table that is actually used is not necessarily required. In a preferred embodiment of the present invention, 40 × 40 pinholes are located and mapped. Fewer pinholes are used in situations where the geometric distortion is low, or where the required accuracy is low, or where other sources of distortion are properly corrected with more reliable interpolation. You may. Linear interpolation associated with the X and Y positions is used to determine mirror positioning for points falling between "optimal positions" stored in look-up tables in storage. The appropriate number of pinholes is determined by these considerations and from the time required to perform the calibration or from the system memory available to store the look-up table. The temporal displacement correction apparatus and method described below are optionally and preferably used with calibration to obtain more precise and accurate results. Similarly, the same temporal displacement correction method and apparatus may be used during part fabrication to improve accuracy and precision.

The method in a preferred embodiment of the present invention will now be briefly described.

First step: The operator inserts the calibration plate into the SLA modeling chamber so that each sensor pinhole of the calibration plate is located at a position where the liquid level is normally located, and performs sensors 1 and 2 (fixed beam). Profile measurement sensor 116,
And 118) and the position of the calibration plate (which can be considered as "sensor 3") between each reading time.

Second stage: The sensors 1 and 2 are repositioned at the position to be positioned when the first profile scan occurs, and their coordinates are determined and recorded as mirror positioning information.

Third step: The center position of the calibration plate is determined by determining whether the position of the sensor 3, that is, the coordinates are within an allowable error range. The center coordinates of the calibration plate should match the center coordinates for mirror positioning. This arrangement allows the mirror to move equally and maximally in all directions.

Fourth step: The signal level obtained by the calibration plate (sensor 3) is set by reading the central pinhole of the calibration plate. (The center pinhole is found by the sensor search algorithm defined by FIG. 1 of the beam profile). The actual beam intensity is
It is found by reading the sensor with and without the beam in the central pinhole. This reduces the background noise received by the sensor 3. Control of the signal level is adjusted by the operator until the sensitivity of the sensor is optimal.

Step 5: The calibration plate boundary is established by advancing the beam from the pinhole to the calibration plate boundary in a stepped manner. (1 = west, 2 = north, 3 = south, 4 = east).

A) A pinhole is searched for in the direction 1 by moving in the direction 1 by a preset (bit / pinhole separation distance) value. The bit indicates the change value of the mirror coordinates.

B) After a known number of pinholes have been read up to the boundary, another movement (bit / pinhole separation) is performed.

C) If the reading finds a pinhole there,
Either the signal level is improperly set due to reading the wrong pinhole, or the search has started with the pinhole to the right of the center pinhole. Return to the third stage.

D) If no pinhole is detected, the left and right boundaries have been established.

E) The beam returns to the center pinhole and searches for the rear boundary in the same way as AD.

F) Once all boundaries have been determined through movements 1 and 2, the values indicating the pinhole locations for movements 1, 2, 3, and 4 create a "pinhole coarse separation map" on the mirror bit plate. Used to do. After the movement 4, the beam is left in the pinhole (1, 1).

Step 6: Rapid search for all pinhole positions on the calibration plate. If the pinhole is no longer located, the beam will remain in a location that is likely to be optimal as determined by the "schematic map of the pinhole" and the operator will be asked to investigate the dust around the pinhole. Prompt. After waiting, the search continues until the pinhole is located or the operator stops. If the operator so desires, the signal level can be reset at this stage. When the signal level is changed, the operator performs a quick search again from the pinhole (1,1).

Seventh step: After searching all the pinholes on the calibration plate by the rapid search, the final search is performed after a necessary delay time from the first step. Also, to determine the “calibration gain value” and “calibration offset value” corrections performed in the rapid and final search at the mirror bit move interval to the same location (end of each row):
The positions of sensors 1 and 2 are checked. These correction values are applied to proportionally correct the position of each calibration point in a way that normalizes to a single combination of fixed sensor 1 and 2 reference locations.

Eighth step: After the final search is completed, all the data of the gain value at calibration, the offset value at calibration, the intensity, and the position are stored. This completes the procedure.

[Position correction over time]

Temporal displacement correction is performed by periodically checking the apparent position of one or more beam profile measurement sensors (herein referred to as "sensor means") to provide a temporal displacement, particularly for mirror positioning systems. This is a procedure for correcting a temporal displacement. 1
The measurement of the variation in the apparent position of the two sensors
It is possible to correct the temporal displacement of the “zero setting” mirror system. In the case of two separate sensors, further correction for variations in SLA part size due to extended mirror operating range of the system and / or thermal or other effects that cannot be compensated for by one sensor Enable. Other errors can be corrected by using multiple sensors, but it is believed that the use of two beam profile measurement sensors in the preferred embodiment of the present invention is sufficient.

In a preferred embodiment of the invention, the calibration operation is performed periodically. The calibration procedure uses a calibration plate with a large number of pinholes and a sensor to generate a table in the system memory of mirror position settings corresponding to pre-fixed positions on the calibration plate.

While performing the calibration, the system periodically checks the apparent position of the two sensors. Since these measurements are used to correct the calibration measurements for this temporal displacement value, they are all standardized as "standard values" indicating the current position of the two sensors. Be transformed into After the part has been formed, the same two sensors are again scanned periodically and the apparent position is used to correct for zero point variations from the time of calibration and extension of the mirror operating range. This method has been found to eliminate 90% of the errors due to mirror displacement over time.
The calibration procedure has already been described.

In the method and apparatus for correcting misregistration over time in a preferred embodiment of the present invention, two sensors for measuring a beam profile which can detect a laser beam when the laser beam is directed to the sensor by a mirror positioning system are provided. The reaction means is fixedly installed at a predetermined fixed position with respect to a designated surface of the working medium which can collide and thereby solidify.

The laser beam is periodically directed at the sensor,
The sensor position output means provides a reading of the sensor apparent position. The current apparent location of the sensor is compared to past apparent sensor locations stored in storage, and the difference indicates the need for misregistration correction over time.

For example, one sensor 1 is used, which has a past apparent position of X = 20, Y = 20 and X = 22,
If we have the current apparent position of Y = 22, then + 2X and +
A 2Y displacement over time has occurred, and the mirror positioning system can apply an appropriate correction factor to direct the beam to the desired location. As another example, a sensor 2 is used in addition to the sensor 1, and the sensor 2
It is assumed that X = 64000 and Y = 64000 are read at the time of calibration, and X = 64004 and Y = 64004 are obtained as current apparent positions. In this case, in addition to the linear movement of + 2X, −2X over the whole system (two sensors arranged diagonally), the extension of + 2X, + 1Y is related to the normalized distance between sensor 1 and sensor 2. is there. The ratio of the distance between the sensor 1 and the sensor 2 after the extension to the normalized distance is referred to as a “gain value”. And we
For different relative positions with respect to the sensor 1, different proportions of expansion proportional to the above are expected and corrected. In making the correction, linear interpolation can be used to help the mirror positioning system correct for stretching due to displacement over time.

Special computer software algorithms have been developed to achieve more accurate part fabrication using 3D molding. This algorithm is known as the "temporal misregistration correction algorithm" and is considered to have two parts.

The first part is a code for determining the value of a variable used for correcting the positional displacement over time. The second part is the code for the use of these variables for misregistration correction over time.

 The temporal displacement correction variables are as follows.

* The X-axis gain value is DriftGain X in our example.
Call.

* X-axis offset value of the first sensor DriftOffset
X * Y-axis gain value DriftGain Y * Y-axis offset value of the first sensor DriftOffset
Y These variables are used to calculate the correction factor applied to each X, Y coordinate position where the laser mirror is pointed. This correction is applied individually to each axis,
Each axis has a gain (multiplier) value and an offset (addition) value. The correction is represented by the following equation.

Modified coordinate value in an axis direction = (gain value × desired distance along the axis from the first sensor) + offset value of the first sensor Here, the gain value and the offset value as variables are
Based on the measured values, the ideal desired position in each axis direction corresponds to the actual corrected coordinate position.

The misregistration correction variable over time is determined at the beginning of each layer formation by the use of an algorithm for beam profile measurement that is very similar to the algorithm in the beam program. The positions of the two beam profile measurement sensors arranged at the diagonal portions of the resin container are measured and calculated, and are compared with the ideal positions stored in the data file in the disk. The difference between the measurement position of these two profile measurement sensors and the ideal position determines the value of the temporal displacement correction variable. Placing two profile measurement sensors at the diagonal of the scan area optimizes each baseline along the X and Y axes, which is the basis for measuring gain value changes.

The following Pascal function is a sample for calculating the value of the temporal displacement correction variable. The 'Ref' variable is
This is the reference position of the two beam profile measurement sensors read from the data file in the disk. 'Now'
The variable is the latest position of the two sensors for profile measurement. Due to dynamic changes in the physical properties of the laser scanning system, the position held in the 'Now' variable is slightly different from the ideal reference position. It is the purpose of this function to utilize these positional differences to adjust the mirror direction immediately after.

For CorrectForDrift… compute value of drift correctionvariables｝ procedure CorrectForDrift; Var quotient: Float Type; begin DriftGain X: = (Sensor2 NowX−Sensor1 NowX) / (Sensor2 RefX−Sensor1 RefX;) DriftOffset X: = Sensor1 NowX; DriftGain Y: = (Sensor2 NowY−Sensor1 NowY) / (Sensor2 RefY−Sensor1 RefY;) DriftOffset Y: = Sensor1 NowY; end; In the following Pascal procedure, after determining the time-varying displacement correction variable, how to convert to a pair of coordinates This shows whether the correction of the positional deviation over time can be performed. Note that the corrections for each axis are independent of each other.

｛DriftCorfect… correct coordinate pair for drift｝ procedure DriftCorrect (oldX, oldY: FloatType: Var newX, newY: FloatTyp
e); begin newX: = (oldX−Sensor1 RefX) * DriftGain X + DriftOffsetX; newY: = (oldY−Sensor1 RefY) * DriftGain Y + DriftOffsetY: end: The DriftCorreet procedure is used when the drawing vector is used within 3D Systems software. It is used to modify the start and end coordinates of each drawing vector prior to being converted into a "feature" which is a highly optimized form of laser writing. After the latest position of the two beam profile measurement sensors is determined, CorrectF
orDrift is used only once per layer.

In effect, these routines are located in a special memory resident driver (known as STEREO) that can be used by different stereolithography application programs. This application program is responsible for detecting the position of the profile measurement sensor and transmits this position information to the special device driver.

 BUILD STEREO Application used for molded parts Program including correction of positional deviation over time; For each layer → Transmits the position information of the server that performs 3D modeling of various types of profile measurement sensors related to multiple tasks. Memory resident driver.

A procedure equivalent to the temporal displacement correction is performed at all calibration points during the calibration of the SLA. In a preferred embodiment, the displacement over time is determined at the end of the scan for each row having a pre-fixed position, and the correction is applied through linear interpolation of that row. The actual software implementation of such a modification routine is within the capabilities of those skilled in the art and will not be described further here.

While a particular form of the invention has been illustrated and described, it will be apparent from the foregoing description that many modifications may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.

Appendix A 34.166-34.169 '88 .4.13 Software status other than 3D Systems Corporation Slice Computer (NEC386) TM 386 / ix Operation System UNIX; System V Release 1.0.4 80386 TDCP Ethernet Support, MICOM Version INTERACTIVE Systems Corporation ( INTERACTIVE Systems Corporation, 2401 Colorado Av
enue, 3rd Floor Santa Monica, California 90404) Process computer (WYSE 286) MS-DOS 3.21 Wyse Technology, 3571 N. First Street, San Jose, CA
95134) Q-DOS II version 2.00 Gazelle Systems, 42 North University Avenue, Suite
10 Provo, Utah 84601) FTP software PC / TCP file transfer program version 1.16 FTP software PC / TCP telnet version 1.16 MICOM-Interlan, Inc., 155 Swanson Rd., Boxborough,
MA 01719) April 13, 1988 SLA-1 Main Parts List Laser: 1) Linconix, 1390 Borregas Abenue, Sunnyvale, CA 9408
9) A) 4240H type He-Cd multi-mode laser B) 4240PS type power supply 2) Omnichrome (Omnichrome, 13620 Fifth Street, Chinno, CA 91710) A) 356XM type He-Cd laser B) 100 type power supply Scanning Mirror: 1) General Scanning, Inc., 500 Arsonal Street, Waterto
wn, MA 02172) A) P / N E00-Z2173 XY0507 scanning mirror B) P / N E00-DX2005 XY0507 scanning mirror controller Z-axis (vertical) elevator: 1) Dedal (Daedal, POBox G, Harrison City, PA 15838) (Purchased through an agency) Pacific Technical Products, 15901 Foothill Blvd.,
Sylmer, CA 91342) A) P / N 008-0324-3 14 inch, 5 pitch linear table B) P / N MC5000-20 Motor drive control SLA-1 Process computer: 1) Wyse Technology, 3571 N. First Street, San Jose, CA
95134) (Purchased through distributor) Peripheral Systems, Inc., 8107 Orion Avenue, Van Nu
ys, CA 91406) A) Wyse 286, Model 2200 (including the following) 1. 40MB hard disk 2. PC AT keyboard 3. Monitor 4. Graphic card 5. Mathematical coprocessor 2) Tarnz Technologies, 8025 Sepulveda Blvd., Van Nuy
s, CA 91406) A) I / O board SLA-1 slice computer: 1) NEC Information Systems, Inc., 1414 Massachusetts A
venue, Boxborough, MA 01719) (Purchased through an agency) Peripheral Systems, Inc., 8107 Orion Avenue, Van Nu
ys, CA 91406) A) NEC PowerMate 386 Computer Beam Expander: 1) Optomeo Design Co., 901 18th St. Suite 203, Los Ala
mos, NM 67544) A) No.D10493 (4X) type beam expander

────────────────────────────────────────────────── ─── Continuing on the front page (31) Priority claim number 268,816 (32) Priority date November 8, 1988 (November 18, 1988) (33) Priority claim country United States (US) (31) Priority Number 268,837 (32) Priority Date November 8, 1988 (1988.11.18) (33) Priority Country United States (US) (72) Inventor Olmquist, Thomas Sa, California, United States of America , Gabriel, Duart, Lord, 9035 (56) References JP-A-51-6742 (JP, A) JP-A-61-225012 (JP, A) JP-A-62-35966 (JP, A) JP 63-72526 (JP, A) JP-A-61-209424 (JP, A) JP-A-61-77184 (JP, U) JP-B-53-34058 (JP, B1) US Patent 4,498,767 (US, A) ( 58) Field surveyed (Int.Cl. ⁷ , DB name) B2 9C 67/00 G02B 26/10 B23K 26/00-26/18 G01J 1/02 G03F 7/20-7/24

Claims (19)

(57) [Claims] 1. A scanning means for directing a beam to each position on a surface of a work medium which can be solidified when exposed to the beam, and a command for designating a direction in which the scanning means directs the beam is issued. Means for selectively solidifying the surface of the working medium to form a desired three-dimensional object layer by layer, comprising: A plate-like calibration device for specifying the command that specifies a direction in which the beam is directed corresponding to a position, comprising: a calibration plate having a plurality of pinholes two-dimensionally arranged at a predetermined position; Detecting means for emitting a signal when the beam is incident on each of the plurality of pinholes.In use, the calibration plate is located at a position determined relative to the surface of the working medium. Calibration apparatus characterized by being arranged in parallel to the serial surface. 2. A scanning means for directing the beam to each position on the surface of the solidifiable working medium when exposed to the beam, and a command for designating a direction in which the scanning means directs the beam is generated by the scanning means. Means for selectively solidifying the surface of the working medium to form a desired three-dimensional object layer by layer, comprising: What is claimed is: 1. A calibration method for specifying a command for designating a direction of directing said beam corresponding to a position, comprising: a calibration plate having a plurality of pinholes two-dimensionally arranged at a predetermined position; A detection device that emits a signal when the beam is incident on each of the work media, a plate-like calibration device is provided at a position defined relative to the surface of the working medium. table Arranging the beam in parallel with a plane; moving the beam on the calibration device so that the beam is sequentially incident on each of the plurality of pinholes; and for each of the pinholes, And storing the command specifying the direction in which the beam is directed when the beam is incident and the detection unit emits the signal in association with the pinhole. 3. The method according to claim 2, wherein the signal generated by the detecting means is a signal linked to an intensity of a beam incident on each of the plurality of pinholes. Adjusting the horizontal position of the calibration device such that one pinhole selected from the plurality of pinholes is located substantially immediately below a point at which the direction of the beam is changed by the scanning unit; Adjusting the calibration device such that the beam is directed substantially toward the selected pinhole, but the sensitivity of the detection means for generating the signal is optimized; and The beam is moved in all directions from the position, and the selected one pinhole is accurately positioned immediately below the point where the direction of the beam is changed by the scanning means. Confirming that the number of pinholes that should be in each of the four sides in the case where the number of times the signal is generated by the detection means while moving the beam in each of the four sides is the same. Further comprising: a number of the pinholes that should be on each of the four sides;
If the number of times the detection means has generated the signal while moving the beam in each of the four directions does not match, the step of adjusting the horizontal position and the sensitivity are optimized. 3. The calibration method according to claim 2, wherein the step of adjusting the calibration device and the step of checking are repeated. 4. The three-dimensional modeling apparatus further includes a storage unit, wherein the storing step includes the steps of:
When the beam is incident on the pinhole and the detection unit emits the signal, storing the command specifying the direction in which the beam is directed in the storage unit in association with the pinhole, When forming the three-dimensional object by the three-dimensional modeling apparatus, when the scanning unit directs the beam to a desired point on the work surface corresponding to any of the pinholes, the computer control unit includes: Sending the command stored in the storage means in association with the pinhole corresponding to the desired point on the work surface to the scanning means; When the scanning means directs the beam to a point, the computer control means corresponds to at least two of the pinholes Directing the beam to the desired point by linear interpolation based on the positions of at least two points on the working surface and the at least two instructions stored in the storage means in association with the at least two pinholes. 4. A calibration method according to claim 2, wherein a command is generated and sent to said scanning means. 5. The calibration method according to claim 2, wherein said beam is a laser beam. 6. A calibration method according to claim 2, wherein said beam is a beam of electromagnetic radiation. 7. The calibration method according to claim 2, wherein said beam is a light beam. 8. The calibration method according to claim 2, wherein said beam is an electron beam. 9. The calibration method according to claim 2, wherein the working medium is a photopolymerizable liquid. 10. The calibration method according to claim 2, wherein the working medium is a powder. 11. A scanning means for directing the beam to each position on a surface of a work medium which can be solidified when exposed to the beam, and a command for designating a direction in which the beam is directed by the scanning means. Means for selectively solidifying the surface of the working medium to form a desired three-dimensional object layer by layer, comprising: What is claimed is: 1. A calibration method for specifying a command for designating a direction of directing said beam corresponding to a position, comprising: a calibration plate having a plurality of pinholes two-dimensionally arranged at a predetermined position; A detection device that emits a signal when the beam is incident on each of the work media, a plate-like calibration device is provided at a position defined relative to the surface of the working medium. Arranging the beam parallel to the surface; moving the beam on the calibration device to sequentially impinge the beam on a plurality of pinholes selected from the plurality of pinholes; For each of the plurality of pinholes, the command that specifies the direction in which the beam is directed when the beam is incident on the pinhole and the detection unit issues the signal is stored in association with the pinhole. A calibration method. 12. The method according to claim 11, wherein the signal generated by the detecting means is a signal linked to an intensity of a beam incident on each of the plurality of pinholes. Adjusting the horizontal position of the calibration device such that one pinhole selected from the plurality of pinholes is located substantially immediately below a point at which the direction of the beam is changed by the scanning unit; Adjusting the calibration device so as to optimize the sensitivity of the detection means for generating the signal while directing the beam substantially in the direction of the selected pinhole; The beam is moved in all directions from a position so that the selected one pinhole is accurately located just below the point where the direction of the beam is changed by the scanning means. In this case, it is confirmed that the number of pinholes that should be in each of the four directions matches the number of times that the detection unit has generated the signal while moving the beam in each of the four directions. A number of said pinholes to be in each of said four sides;
If the number of times the detection means has generated the signal while moving the beam in each of the four directions does not match, the step of adjusting the horizontal position and the sensitivity are optimized. 12. The calibration method according to claim 11, wherein the step of adjusting the calibration device and the step of checking are repeated. 13. The three-dimensional modeling apparatus further includes storage means, wherein the step of storing includes, for each of the plurality of selected pinholes, the beam is incident on the pinhole, and the detection means outputs the signal Is a step of storing the command specifying the direction in which the beam is directed in the storage unit in association with the pinhole when the three-dimensional object is formed by the three-dimensional modeling apparatus. When the scanning means directs the beam to a desired point on the work surface corresponding to any of the plurality of pinholes provided, the computer control means controls the computer control means to correspond to the desired point on the work surface. Sending the command stored in the storage unit in association with the pinhole to be performed to the scanning unit, and not corresponding to any of the selected plurality of pinholes. When the scanning means directs the beam to a desired point on the work surface, the computer control means causes the computer control means to direct the beam onto the work surface corresponding to at least two of the selected plurality of pinholes. At least 2
Generating a command to direct the beam to the desired point by linear interpolation based on the position of the point and the at least two commands stored in the storage means in association with the at least two pinholes; 13. The calibration method according to claim 11, wherein the calibration method is sent to a means. 14. The calibration method according to claim 11, wherein said beam is a laser beam. 15. The calibration method according to claim 11, wherein said beam is a beam of electromagnetic radiation. 16. The calibration method according to claim 11, wherein said beam is a light beam. 17. The calibration method according to claim 11, wherein said beam is an electron beam. 18. The calibration method according to claim 11, wherein the working medium is a photopolymerizable liquid. 19. The calibration method according to claim 11, wherein the working medium is a powder.