Calibration device and uses thereof
This invention relates to a device for calibrating circular or linear dichroism spectrometers, or other photoelastic modulator (PEM) based devices or instruments. In preferred embodiments, the present invention features a device for calibrating circular dichroism or linear dichroism spectrometers comprising at least one waveplate (Q) providing (n±¼) waves of retardation at a defined set of wavelengths, and at least one isotropic plate (P). The invention also features methods for using the device, for example, for calibrating circular dichroism spectrometers or linear dichroism spectrometers.
1. A device for calibrating circular dichroism or linear dichroism spectrometers or other photoelastic modulator based devices or instruments comprising: at least one waveplate (Q) providing (n±¼) waves of retardation at a defined set of wavelengths, wherein the waveplate (Q) has a thickness (t); comprising at least one waveplate (H) providing (N±½) waves of retardation at the same wavelengths where Q provides (n±¼) waves of retardation, wherein the waveplate (H) has a thickness (2+4m)t, where m is zero or a positive integer; and at least one isotropic plate (P).
2. The device of claim 1 , wherein the waveplate (H) has a thickness (2t).
3. The device of claim 1 , wherein the waveplate (Q) or the waveplate (H) is oriented with its surface normal to a direction of light propagation (Z axis).
4. The device of claim 1 , wherein the waveplate (Q) or the waveplate (H) is oriented with its crystal axis at an angle about a Z axis, measured from the positive X axis direction.
5. The device of claim 4 , wherein the angle is 45°.
6. The device of claim 3 , wherein the waveplate (Q) or the waveplate (H) is subsequently rotated at an angle about a Y axis.
7. The device of claim 6 , wherein the angle is between 1° and 90° about the Y axis.
8. The device of claim 3 , wherein the waveplate (Q) or the waveplate (H) is subsequently rotated at an angle about an X axis.
9. The device of claim 8 , wherein the angle is between 1° and 90° about the X axis.
10. The device of claim 1 , wherein the isotropic plate (P) is oriented at an angle about a Y axis.
11. The device of claim 10 , wherein the angle is between 1° and 90° about the Y axis.
12. The device of claim 1 , wherein the isotropic plate (P) is oriented at an angle about an X axis.
13. The device of claim 12 , wherein the angle is between 1° and 90° about the X axis.
14. The device of claim 1 , wherein two isotropic plates (P) are oriented at equal and opposite angles about the X or Y axis.
15. The device of claim 1 , wherein the isotropic plate (P) is oriented normal to a direction of light propagation (Z axis).
16. A method of calibrating circular dichroism spectrometers or linear dichroism spectrometers with the device of claim 1 .
17. The device of claim 1 , comprising two waveplates (Q) providing (n±¼) waves of retardation.
18. A device for calibrating circular dichroism or linear dichroism spectrometers or other photoelastic modulator based devices or instruments comprising:
at least one waveplate (Q) providing (n±¼) waves of retardation at a defined set of wavelengths, wherein the waveplate (Q) has a thickness (t); and
at least one isotropic plate (P), wherein a first isotropic plate (P) is oriented at a first angle about an axis;
wherein a second isotropic plate (P) is oriented at a second angle about an axis;
and wherein the first and second isotropic plates (P) are oriented at equal and opposite angles about the axis.
19. The device of claim 18 , wherein the axis is an X axis.
20. The device of claim 18 , wherein the axis is a Y axis.
21. The device of claim 19 , wherein the angle is between 1° and 90° about the X axis.
22. The device of claim 20 , wherein the angle is between 1° and 90° about the Y axis.
23. The device of claim 18 , comprising two waveplates (Q) providing (n±¼) waves of retardation.