waveguide:manuals:ls-15-3005
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waveguide:manuals:ls-15-3005 [2016/01/15 03:31] – [Operation] Michael Radunsky | waveguide:manuals:ls-15-3005 [2016/01/19 00:22] – [Connections and Controls] Michael Radunsky | ||
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Do not clean outside surfaces of any Vescent Photonics products with solvents such as acetone. Front panels on electronics modules may be cleaned with a mild soap and water solution. Do not clean optics modules. | Do not clean outside surfaces of any Vescent Photonics products with solvents such as acetone. Front panels on electronics modules may be cleaned with a mild soap and water solution. Do not clean optics modules. | ||
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+ | The user should NEVER disconnect the control cable from the scanner or driver while power is applied ("hot swapping" | ||
==Limited Warranty== | ==Limited Warranty== | ||
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Vescent Photonics shall not be obligated to furnish service under this warranty from damage caused by service or repair attempts made without authorization by Vescent Photonics; from damage caused by operation of equipment outside of its specified range as stated in either the product specifications or operators manual; from damage due to improper connection to other equipment or power supplies. | Vescent Photonics shall not be obligated to furnish service under this warranty from damage caused by service or repair attempts made without authorization by Vescent Photonics; from damage caused by operation of equipment outside of its specified range as stated in either the product specifications or operators manual; from damage due to improper connection to other equipment or power supplies. | ||
This warranty is in lieu of all other warranties including any implied warranty concerning the suitability or fitness of the product for a particular use. Vescent Photonics shall only be liable for the cost of repairs or replacement of the defective product within the warranty period. Vescent Photonics shall not be liable for any damages to persons or property resulting from the use of the product or caused by the defect or failure of this product. Vescent Photonics' | This warranty is in lieu of all other warranties including any implied warranty concerning the suitability or fitness of the product for a particular use. Vescent Photonics shall only be liable for the cost of repairs or replacement of the defective product within the warranty period. Vescent Photonics shall not be liable for any damages to persons or property resulting from the use of the product or caused by the defect or failure of this product. Vescent Photonics' | ||
- | Vescent Photonics | ||
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=====Operating Parameters===== | =====Operating Parameters===== | ||
Absolute Maximum Ratings | Absolute Maximum Ratings | ||
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===Prototype EO Scanner Optical Head=== | ===Prototype EO Scanner Optical Head=== | ||
The 1.5 µm LS-15-43005-FC/ | The 1.5 µm LS-15-43005-FC/ | ||
- | The scanner is packaged with a PM fiber pigtail (see Figure 4) with an FC/PC connector. This is an engineering package and not intended for field use. Its input must be linearly polarized light with the polarization axis parallel to the FC key. | + | The scanner is packaged with a PM fiber pigtail (see Figure 4) with an FC/PC connector. This is an engineering package and not intended for field use. Its input must be linearly polarized light with the polarization axis parallel to the FC key. |
- | + | ||
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=====Connections and Controls===== | =====Connections and Controls===== | ||
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+ | The user should NEVER disconnect the control cable from the scanner or driver while power is applied ("hot swapping" | ||
With the power switch in the OFF or down position (see Figure 5) connect the power supply to the wall plug and to the LS-105 back panel (see Figure 6). Use the provided cable to connect the LS-105 driver to the SEEOR unit. The unit is now ready to be powered on. The driver provides up to 110 V to the beam steerer. | With the power switch in the OFF or down position (see Figure 5) connect the power supply to the wall plug and to the LS-105 back panel (see Figure 6). Use the provided cable to connect the LS-105 driver to the SEEOR unit. The unit is now ready to be powered on. The driver provides up to 110 V to the beam steerer. | ||
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Now the beam steerer is ready for steering. | Now the beam steerer is ready for steering. | ||
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Front Panel Controls (from left to right) | Front Panel Controls (from left to right) | ||
|Power Switch|This turns the unit on. Up is on and down is off.| | |Power Switch|This turns the unit on. Up is on and down is off.| | ||
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</ | </ | ||
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Back panel Controls (from left to right) | Back panel Controls (from left to right) | ||
|Polarity Clock out|This outputs the clock frequency. | |Polarity Clock out|This outputs the clock frequency. | ||
|Polarity Clock in|If the user does not connect a clock input, the driver will use its internal clock that is set to 5 KHz. If the user inputs the clock signal, the internal clock will be disabled automatically and the external clock will be used.| | |Polarity Clock in|If the user does not connect a clock input, the driver will use its internal clock that is set to 5 KHz. If the user inputs the clock signal, the internal clock will be disabled automatically and the external clock will be used.| | ||
- | |Power In|Power the driver with the AC adapter that is included with the package.|</ | + | |Power In|Power the driver with the AC adapter that is included with the package.| |
+ | </ | ||
=====Advanced Settings===== | =====Advanced Settings===== | ||
- | 3.3. Background on Driving LC Devices | + | ====Background on Driving LC Devices==== |
- | When designing LC-drive electronics there are two important inherent properties. First, for a typical nematic LC, the EO response is via an induced dipole interaction. This means that the LC-molecules respond to the magnitude of the applied electric field but not the sign. Second, it is necessary that the time-averaged voltage across an LC optic is “DC-balanced” to have zero or minimal offset. This can be critical for both the operation and lifetime of the device. Prolonged time-averaged DC offsets will drive ion-migration inside the LC material, which can be deleterious for both the short-term performance and ultimately the lifetime of the device. On short timescales ion-migration will create a shielding field to cancel the applied voltage, which will cause the LC molecules to “relax” or “sag.” Precision applications can be sensitive to this sag even during short timescales. On long timescales ion-migration can result in the build up of permanent charge layers within the LC, thereby causing a “burn-in” which may forever degrade the operation of the device. The LC-drive electronics must account for both the “induced dipole” response and the “DC-balance” constraint. | + | When designing LC-drive electronics there are two important inherent properties. First, for a typical nematic LC, the EO response is via an induced dipole interaction. This means that the LC-molecules respond to the magnitude of the applied electric field but not the sign. Second, it is necessary that the time-averaged voltage across an LC optic is “DC-balanced” to have zero or minimal offset. This can be critical for both the operation and lifetime of the device. Prolonged time-averaged DC offsets will drive ion-migration inside the LC material, which can be deleterious for both the short-term performance and ultimately the lifetime of the device. On short timescales ion-migration will create a shielding field to cancel the applied voltage, which will cause the LC molecules to “relax” or “sag.” Precision applications can be sensitive to this sag even during short timescales. On long timescales ion-migration can result in the build up of permanent charge layers within the LC, thereby causing a “burn-in” which may forever degrade the operation of the device. The LC-drive electronics must account for both the “induced dipole” response and the “DC-balance” constraint.\\ |
- | An optimum voltage waveform that satisfies both of these LC requirements is a high quality square wave with no DC offset. Since the LC material only responds to the magnitude of the electric field and not the sign, by rapidly switching the voltage polarity the LC material will see the same E-field magnitude and simultaneously the need for DC balance will be satisfied. While in principle the square wave provides the ideal waveform, for anyone who has ever worked with square waves they will know that a high quality square wave is easier said than done. This is especially true when driving capacitive loads such as LC cells. Furthermore, | + | An optimum voltage waveform that satisfies both of these LC requirements is a high quality square wave with no DC offset. Since the LC material only responds to the magnitude of the electric field and not the sign, by rapidly switching the voltage polarity the LC material will see the same E-field magnitude and simultaneously the need for DC balance will be satisfied. While in principle the square wave provides the ideal waveform, for anyone who has ever worked with square waves they will know that a high quality square wave is easier said than done. This is especially true when driving capacitive loads such as LC cells. Furthermore, |
- | Common problems with square waves are illustrated on the left of Figure 9. Typically, the square wave is generated via amplification of a low voltage clock from a function generator or other clock source. Frequently, amplifiers are susceptible to several common problems: offsets (often frequency dependent which hampers trimming), limited slew rates, limited settling times (can cause overshoot | + | <WRAP center round box 90%> |
+ | </ | ||
+ | Common problems with square waves are illustrated on the left of Figure 7. Typically, the square wave is generated via amplification of a low voltage clock from a function generator or other clock source. Frequently, amplifiers are susceptible to several common problems: offsets (often frequency dependent which hampers trimming), limited slew rates, limited settling times (can cause overshoot and ringing), and limited current output. As shown on the left of Figure 7, all of these problems can have dramatic impacts on the magnitude of the electric field, i.e. what the LC responds to. For high-speed LC devices, the slew rate required to minimize any transient LC response during the polarity switch can be >100 Volts/ms, which is beyond the capabilities of most amplifiers when driving a capacitive load. The right hand side of Figure 7 shows an ideal square wave and its associated constant E-field magnitude. Figure 8 plots an example waveform from an LS-105. | ||
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+ | ====SEEOR: An Asymmetric LC Device==== | ||
+ | For conventional LC devices such as displays, the electronics are constructed to keep the DC offset minimized over all operational square wave voltages. | ||
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+ | ====Internal Factory-Set Trim Pots==== | ||
+ | There are a number of internal trim pots that are factory set. These are typically set for a specific scanner. | ||
+ | By unscrewing the four hex-bolts and the two BNC washers, the front panel may be folded up to allow access to four of the internal trim pots, as shown in Figure 10. From here, the user may adjust the magnitude and sign of the voltage dependent offsets. If the scanner has more than acceptable twinning or splitting of the scanned beam, especially at maximum deflection, then it may be beneficial to adjust the magnitude of the voltage dependent offset. | ||
+ | Also shown in Figure 10 are the trim pots for setting the Freedericksz voltages. | ||
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- | + | </ | |
- | Figure 9: Left) Drawing of a typical square wave as provided by common amplifiers. Slew rate, DC offset, overshoot, and ripple all result in a non-constant E-field magnitude. Since it is the E-field magnitude that the LC responds to this can be problematic. Right) Drawing of an ideal square wave and its related constant E-field magnitude. The goal of a proper LC-driver is to get as close to this ideal as possible. | + | |
- | + | ||
- | Figure 10: Plot of a typical high voltage output from the LS-105. | + | |
- | 3.4. SEEOR: An Asymmetric LC Device | + | |
- | For conventional LC devices such as displays, the electronics are constructed to keep the DC offset minimized over all operational square wave voltages. | + | |
- | + | ||
- | Figure 11: The two types of DC offsets that are important for proper control of the SEEOR. | + | |
- | 3.5. Internal Factory-Set Trim Pots | + | |
- | There are a number of internal trim pots that are factory set. These are typically set for a specific scanner. | + | |
- | By unscrewing the four hex-bolts and the two BNC washers, the front panel may be folded up to allow access to four of the internal trim pots, as shown in Figure 12. From here, the user may adjust the magnitude and sign of the voltage dependent offsets. If the scanner has more than acceptable twinning or splitting of the scanned beam, especially at maximum deflection, then it may be beneficial to adjust the magnitude of the voltage dependent offset. | + | |
- | Also shown in Figure 12 are the trim pots for setting the Freedericksz voltages. | + | |
- | + | ||
- | Figure 12: Trim pots that are accessible after removing the front panel. | + | |
There is another set of trim pots that are only accessible by sliding the electronics out of the housing. | There is another set of trim pots that are only accessible by sliding the electronics out of the housing. | ||
- | Inside the LS-105 there are two electronics boards. | + | Inside the LS-105 there are two electronics boards. |
- | There is also a trim plot to minimize the constant DC offset for each of the three SEEOR electrodes, as shown in Figure | + | There is also a trim plot to minimize the constant DC offset for each of the three SEEOR electrodes, as shown in Figure |
- | Figure | + | <WRAP center round box 450px> |
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