1. A method for forming a microstructure, comprising:
(a) forming a photocurable layer on a substrate, the photocurable layer including at least one photocurable compound that has a plurality of photocurable functional groups and a photocurable functional group equivalent weight ranging from 70 to 700 gmol;
(b) covering partially the photocurable layer using a patterned mask;
(c) exposing the photocurable layer through the patterned mask using a first light source so that the photocurable layer is cured at first regions which are exposed;
(d) removing the patterned mask; and
(e) illuminating the photocurable layer using a second light source to cure second regions of the photocurable layer which have not been cured;
wherein the first and second regions have different surface heights and provide a surface roughness for the microstructure.
2. The method of claim 1, wherein the first light source is UV light, visible light, electron beam, or X-ray.
3. The method of claim 1, wherein the second light source is UV light, visible light, electron beam, or X-ray.
4. The method of claim 1, wherein the first light source is UV light and has an exposure dosage of not less than 70 mJcm2.
5. The method of claim 1, wherein the photocurable functional group equivalent weight of the photocurable compound ranges from 80 to 600 gmol.
6. The method of claim 1, wherein the photocurable functional group equivalent weight of the photocurable compound ranges from 85 to 400 gmol.
7. The method of claim 1, wherein, in step (a), the photocurable layer further includes a photoinitiator.
8. The method of claim 1, wherein the photocurable layer is formed by coating the substrate with a paste including the photocurable compound.
9. The method of claim 8, wherein the paste further includes a solvent.
10. The method of claim 1, wherein the photocurable functional groups are selected from the group consisting of an alkenyl group and an epoxy group.
11. The method of claim 7, wherein the photoinitiator is selected from the group consisting of vinyl phenone derivatives, benzophenone derivatives, Michler’s ketone, benzyne, benzyl derivatives, benzoin derivatives, benzoin methyl ether derivatives, \u03b1-acyloxy ester, thioxanthone derivatives, and anthraquinone derivatives.
12. The method of claim 9, wherein the solvent is selected from the group consisting of acetone, acetonitrile, chloroform, chlorophenol, cyclohexane, cyclohexanone, cyclopentanone, dichloromethane, diethyl acetate, dimethyl carbonate, ethanol, ethyl acetate, N, N-dimethyl acetamide, 1,2-propanediol, 2-hexanone, methanol, methyl acetate, butyl acetate, toluene, and tetrahydrofuran.
13. The method of claim 1, wherein the surface roughness is not less than 0.05 \u03bcm.
14. The method of claim 1, wherein the surface roughness ranges from 0.15 \u03bcm to 8 \u03bcm.
15. The method of claim 1, wherein the surface roughness ranges from 0.2 \u03bcm to 7 \u03bcm.
16. A microstructure made according to the method of claim 1.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An apparatus for processing a digital input signal having a sampling frequency, the apparatus comprising:
an adaptive gain selection module configured to select a target gain setting based on a detected level of the digital input signal, a higher target gain setting being selected for a lower detected level;
a digital multiplier configured to multiply an upsampled version of the digital input signal with an instantaneous digital gain approaching the target gain setting to generate a digital output signal, the instantaneous digital gain updated upon detection of a zero cross in the upsampled version of the digital input signal; and
an amplifier configured to amplify an analog version of the digital output signal with an instantaneous analog gain inversely proportional to the instantaneous digital gain.
2. The apparatus of claim 1, the instantaneous digital gain configured to approach the target gain setting in fixed decibel increments.
3. The apparatus of claim 1, further comprising a level detection module further configured to filter the absolute value of the digital input signal with a configurable time constant to generate the detected level of the digital input signal.
4. The apparatus of claim 3, the level detection module further configured to downsample the filtered value by a configurable factor to generate a signal indicating the detected level of the digital input signal.
5. The apparatus of claim 1, the adaptive gain selection module further configured to assign a target gain setting based on the detected level of the digital input signal falling within one of a plurality of predefined zones, each zone being defined by at least one configurable threshold.
6. The apparatus of claim 5, the adaptive gain selection module further configured to assign the detected level of the digital input signal to one of the predefined zones based on whether such detected level lies outside such predefined zone by a configurable hysteresis amount.
7. The apparatus of claim 1, further comprising a zero cross detection module configured to detect the zero cross of the upsampled signal based on whether the absolute value of the upsampled signal is greater or less than a configurable zero detect window parameter.
8. The apparatus of claim 1, further comprising:
a peak detection module configured to detect a peak level of the digital input signal; the apparatus configured to reduce the instantaneous digital gain applied by the digital multiplier in response to the detected peak level being greater than a peak threshold level.
9. The apparatus of claim 8, the peak threshold level being inversely proportional to the instantaneous digital gain.
10. The apparatus of claim 8, further comprising a peak gain correction module configured to adjust the instantaneous digital gain to be a value that will result in no clipping by the multiplier in response to the detected peak level being greater than a threshold determined by the instantaneous digital gain.
11. The apparatus of claim 8, the apparatus further configured to hold the reduced instantaneous digital gain for a configurable timeout period in response to the detected peak level being greater than the threshold determined by the instantaneous digital gain.
12. The apparatus of claim 11, the apparatus further configured to, in response to detecting a second peak level greater than the threshold determined by the instantaneous gain during a running timeout period:
reduce the instantaneous digital gain applied by the digital multiplier in response to the second detected peak level; and
hold the reduced instantaneous digital gain for the configurable timeout period commencing with the detection of said second detected peak level.
13. The apparatus of claim 1, the digital input signal comprising a digital audio signal, the apparatus further comprising an upsampling module including an interpolator.
14. The apparatus of claim 1, further comprising an upsampling module for generating the upsampled version of the digital input signal, the upsampling module including a zero-order hold module.
15. The apparatus of claim 1, further comprising an upsampling module for generating the upsampled version of the digital input signal, the upsampling module including a CIC filter.
16. The apparatus of claim 1, the amplifier comprising a power amplifier having adjustable analog gain.
17. A method for processing a digital input signal having a sampling frequency, the method comprising:
selecting a target gain setting based on a detected level of the digital input signal, a higher target gain setting being selected for a lower detected level;
multiplying an upsampled version of the digital input signal with an instantaneous digital gain approaching the target gain setting to generate a digital output signal, the instantaneous digital gain updated upon detecting a zero cross in the upsampled version of the digital input signal; and
amplifying an analog version of the digital output signal with an instantaneous analog gain inversely proportional to the instantaneous digital gain.
18. The method of claim 17, further comprising configuring the instantaneous digital gain to approach the target gain setting in fixed decibel increments.
19. The method of claim 17, further comprising detecting the level of the digital input signal by filtering the absolute value of the digital input signal with a configurable time constant.
20. The method of claim 19, the detecting the level of the digital input signal comprising downsampling the filtered value by a configurable factor to generate a signal indicating the detected level of the digital input signal.
21. The method of claim 17, the selecting the target gain setting comprising assigning a target gain setting based on the detected level of the digital input signal falling within one of a plurality of predefined zones, each zone being defined by at least one configurable threshold.
22. The method of claim 21, the selecting the target gain setting further comprising assigning the detected level of the digital input signal to one of the predefined zones based on whether such detected level lies outside such predefined zone by a configurable hysteresis amount.
23. The method of claim 17, further comprising detecting the zero cross by detecting whether the absolute value of the upsampled signal is greater or less than a configurable zero detect window parameter.
24. The method of claim 17, further comprising:
detecting a peak level of the digital input signal; and
reducing the instantaneous digital gain in response to the detected peak level being greater than a peak threshold level.
25. The method of claim 24, the peak threshold level being inversely proportional to the instantaneous digital gain.
26. The method of claim 24, further comprising adjusting the instantaneous digital gain to be a value that will result in no clipping when generating the analog version of the digital output signal.
27. The method of claim 24, further comprising holding the reduced instantaneous digital gain for a configurable timeout period in response to the detected peak level being greater than the threshold determined by the instantaneous digital gain.
28. The method of claim 27, further comprising, in response to detecting a second peak level greater than the threshold determined by the instantaneous gain during a running timeout period:
reducing the instantaneous digital gain applied by the digital multiplier in response to the second detected peak level; and
holding the reduced instantaneous digital gain for the configurable timeout period commencing with detecting said second detected peak level.
29. The method of claim 17, the digital input signal comprising a digital audio signal, the method further comprising upsampling the digital input signal by interpolating and applying a zero-order hold.
30. The method of claim 17, the method further comprising upsampling the digital input signal by applying a CIC filter.
31. The method of claim 17, the amplifying the DAC output signal further comprising amplifying with an adjustable gain to generate an analog output, and further amplifying the analog version of the digital output signal by a power amplifier.
32. An apparatus for processing a digital input signal having a sampling frequency, the apparatus comprising:
means for selecting a target gain setting based on the detected level of the digital input signal;
means for multiplying an upsampled version of the digital input signal with an instantaneous digital gain approaching the target gain setting to generate a digital output signal; and
means for amplifying an analog version of the digital output signal with an instantaneous analog gain inversely proportional to the instantaneous digital gain.