Pixel cross talk suppression in digital microprinters
First Claim
Patent Images
1. A printing system comprising:
- a spatial light modulator (SLM) for image generation, the SLM comprising an array of source pixel elements, wherein each source pixel modulates illumination intercepting that pixel;
an illumination source disposed to illuminate the SLM, whereupon modulated illumination leaves the SLM; and
an optical projection system disposed to convey the modulated illumination from the SLM to a printing surface, wherein each source pixel generates a corresponding modulated exposure field that exposes the printing surface;
the SLM being configured to induce a phase difference of approximately π
/2 between adjacent exposure fields.
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Abstract
Digital microprinters such as maskless projection lithography systems can be adversely affected by pixel cross talk resulting from coherent interactions between adjacent pixels. Such effects are significantly mitigated by inducing a π/2 optical phase shift between adjacent pixels. In one implementation, the printing surface is exposed twice, with the phase shift sign-inverted between exposures so that coherent interaction effects cancel out between the two exposures.
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Citations
27 Claims
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1. A printing system comprising:
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a spatial light modulator (SLM) for image generation, the SLM comprising an array of source pixel elements, wherein each source pixel modulates illumination intercepting that pixel;
an illumination source disposed to illuminate the SLM, whereupon modulated illumination leaves the SLM; and
an optical projection system disposed to convey the modulated illumination from the SLM to a printing surface, wherein each source pixel generates a corresponding modulated exposure field that exposes the printing surface;
the SLM being configured to induce a phase difference of approximately π
/2 between adjacent exposure fields.- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 19)
the SLM is configured with a phase-shifting mechanism that comprises two optical media proximate the source pixels;
the two media have different refractive indices;
portions of the illumination that intercept any two adjacent source pixels traverse different optical path lengths through the two media; and
the optical path length difference between adjacent pixels is selected to induce a phase difference of approximately π
/2 between adjacent pixels.
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9. The printing system of claim 1, wherein the projection system comprises an Offner catoptric system.
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19. The printing system of claim 9, wherein the projection system comprises an Offner catoptric system.
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10. A printing system comprising a Spatial Light Modulator (SLM), an illumination source, an optical projection system, a printing surface, and a positioning mechanism, wherein:
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the illumination source illuminates the SLM;
the SLM comprises an array of source pixel elements, wherein each source pixel modulates the illumination intercepting that pixel;
the projection system conveys the modulated illumination from the SLM to the printing surface, wherein each source pixel generates a corresponding modulated exposure field that exposes the printing surface;
the SLM further comprises a phase-shifting mechanism that induces a phase difference of approximately π
/2 between adjacent exposure fields;
the positioning mechanism controls the positional relationship between the printing surface and the SLM; and
at least two exposures are applied to the printing surface, wherein the two exposures are substantially identical except that the positional relationship is altered between the two exposures so as to invert the sign of the phase difference, and whereby the sign inversion causes coherent interaction between adjacent exposure fields to substantially cancel out between the two exposures. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
alternate source pixels are recessed relative to their adjacent pixels;
the phase-shifting mechanism comprises the pixel recesses; and
the recess depth is selected to induce a phase difference of approximately π
/2 between adjacent pixels.
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16. The printing system of claim 10, wherein:
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the phase-shifting mechanism comprises two optical media proximate the source pixels;
the two media have different refractive indices;
portions of the illumination that intercept any two adjacent source pixels traverse different optical path lengths through the two media; and
the optical path length difference between adjacent pixels is selected to induce a phase difference of approximately or π
/2 between adjacent pixels.
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17. The printing system of claim 10 wherein the projection system images the source pixels onto the printing surface.
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18. The printing system of claim 10 wherein
the printing system further comprises a planar array of microlenses proximate the printing surface, the exposure field corresponding to each source pixel comprises a primary radiation component that has intercepted and been focused by a microlens corresponding to the source pixel, but which may also comprise a secondary radiation component that has intercepted and been focused by adjacent microlenses, the two exposures cause the coherent interactions between the primary radiation component from each source pixel and the secondary radiation component from other adjacent source pixels to substantially cancel out.
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20. A method of operating a printing system that includes a spatial light modulator (SLM) for image generation, the SLM comprising an array of light-modulating pixels, the method comprising:
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illuminating the SLM;
controlling the SLM in accordance with a desired information pattern so that each pixel modulates the illumination intercepting that pixel;
projecting the modulated illumination from the SLM to a printing surface so that each pixel generates a corresponding modulated exposure field that exposes the printing surface; and
inducing a phase difference of approximately π
/2 between adjacent exposure fields.- View Dependent Claims (21, 22, 23)
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24. A method of operating a printing system that includes a spatial light modulator (SLM) that comprises an array of light-modulating pixels, the method comprising:
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illuminating the SLM;
controlling the SLM in accordance with a desired information pattern so that each pixel modulates the illumination intercepting that pixel;
projecting the modulated illumination from the SLM to a printing surface so that each pixel generates a corresponding modulated exposure field that exposes the printing surface;
inducing a phase difference of approximately π
/2 between adjacent exposure fields;
applying a first exposure to the printing surface;
altering the positional relationship between the printing surface and the SLM in a manner that inverts the sign of the phase difference; and
applying a second exposure to the printing surface, whereby the sign inversion causes coherent interaction between adjacent exposure fields to substantially cancel out between the two exposures. - View Dependent Claims (25, 26, 27)
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Specification