1. Micro-mirror Micromechatronics System FH AACHEN
University of Applied Science
Supervisor: Prof. Kämper
Team member:
Chun Wa George Young
Issis Contreras
Ramanathan Swaminathan
Spandan Shroff

2. Advantage of MEMS Spectrometer over conventional
small size
low cost,
fast response – filter unwanted wavelengths
high signal to noise ratio
reduced complexity and low power consumption

3. Key features of micromirror array
a 100% fill-factor
minimum surface roughness and high reflectivity (ideally 100%) in the wavelength range of interest
zero insertion loss
zero noise
simple control
identical deflection versus input energy response

4. A unique application of micromachined mirrors can be performance enhancement of a spectrometer by selectively focusing a particular spectral component on a detector thereby reducing the number of detectors required.
improves the signal to noise ratio of the spectrometer device

5. IR Range Spectrometer
Littrow configuration
Source: FhG-IZM

6. Portable Universial Spectrometer
Small mirror – reducing bandpass - higher resolution
But low light intensity
Variable band pass filter

7. Diffraction grating Monochromatic light d sina + d sinb = wavelength
So leading to constructive interference
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8. Diffraction grating
When a diffraction grating is used, care must be taken in the design of broadband monochromators because the diffraction pattern has overlapping orders.
In-plane diffraction
refers to a diffraction technique in which both the incident and diffracted beams are nearly parallel to the sample surface.
The grating diffracts the light, which converges toward the exit slit; the spectrum is scanned by rotating the grating to bring different wavelengths into focus at or near the exit slit.
The spectrum is scanned by rotating the grating; this moves the grating normal relative to the incident and diffracted beams, which (by Eq. (2-1)) changes the wavelength diffracted toward the second mirror.
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9. Grat scanning
The spectrum is scanned by rotating the grating; this moves the grating normal relative to the incident and diffracted beams, which (by Eq. (2-1)) changes the wavelength diffracted toward the second mirror.
 the grating is rotated to bring different wavelengths into focus at the (stationary) exit slit.
The grating diffracts the light, which converges toward the exit slit; the spectrum is scanned by rotating the grating to bring different wavelengths into focus at or near the exit slit.
The efficiency is maximal when the grating is used in the Littrow configuration
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10. Plan grating and mounts
The Czerny-Turner monochromator
the light incident on and diffracted by the grating is collimated, the spectrum remains at focus at the exit slit for each wavelength,
The Ebert-Fastie monochromator
This design is a special case of a Czerny-Turner mount
Disadvantage
This can be seen by recognizing that the Ebert-Fastie monochromator is a special case of the Czerny-Turner monochromator in which both concave mirror radii are the same, and for which their centers of curvature coincide.
Advantage
However, an advantage that the Ebert-Fastie mount provides is the avoidance of relative misalignment of the two mirrors
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11. Plan grating and mounts
The Monk-Gillieson monochromator
Advantage
Often the angles of reflection (from the primary mirror), incidence and diffraction are small (measured from the appropriate surface normals), which keeps aberrations (especially off-axis astigmatism) to a minimum.
Disadvantage
Consequently the spectrum cannot remain in focus at a fixed exit slit when the grating is rotated (unless this rotation is about an axis displaced from the central groove of the grating42).
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12. Plan grating and mounts
The Littrow monochromator
The same auxiliary optics can be used as both collimator and camera, since the diffracted rays retrace the incident rays.
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13. Definition In-plane diffraction
refers to a diffraction technique in which both the incident and diffracted beams are nearly parallel to the sample surface.
The blaze wavelength
is defined as that wavelength, in a given diffraction order m, for which the efficiency curve reaches its maximum.
ml = d (sina + sinb)
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15. Fabrication
polysilicon (poly-Si) and gold micromirror is fabricated by a surface -micromachining process
Drawback: residual stress
Result: curvature of the mirror surface which results in high insertion loss and crosstalk
So monocrystalline silicon
best results and closely resembles
an ideal reflector surface.
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16. 1 dimension array micro mirror
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17. Type of micro mirror
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18. Question
The proposal is workable?
Mirror size?
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19. Optics definition Aberrations
are departures of the performance of an optical system from the predictions of paraxial optics
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20. Slit
The entrance slit is placed at the effective focus of the collimator so that the light from the slit reflected from the mirror is collimated (focused at infinity)
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21. Portable Monochromator
300nm – 5um
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22. Portable Monochromator
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