waveguide:manuals:ls-15-3005
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waveguide:manuals:ls-15-3005 [2016/01/15 03:01] – [Prototype EO Scanner Optical Head] 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. | ||
+ | |||
+ | <color red> | ||
+ | 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 | ||
+ | <WRAP center round box 400px> | ||
+ | </ | ||
=====Operating Parameters===== | =====Operating Parameters===== | ||
Absolute Maximum Ratings | Absolute Maximum Ratings | ||
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=====Operation===== | =====Operation===== | ||
The LS-105 is shipped with a 5 V power supply and a cable for connection to the SEEOR, as shown in Figure 2. If you purchased a chip level SEEOR the cable will have a connector on one end and clip-connectors on the other end. If you purchased a fiber-coupled SEEOR the cable will be connectorized at both ends. | The LS-105 is shipped with a 5 V power supply and a cable for connection to the SEEOR, as shown in Figure 2. If you purchased a chip level SEEOR the cable will have a connector on one end and clip-connectors on the other end. If you purchased a fiber-coupled SEEOR the cable will be connectorized at both ends. | ||
- | < | + | < |
<WRAP right round box 550px> | <WRAP right round box 550px> | ||
The cable plugs into the LS-105 with a push connector. | The cable plugs into the LS-105 with a push connector. | ||
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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. |
- | + | =====Connections and Controls===== | |
- | <WRAP left round box 400px>[{{ : | + | <color red>WARNING</color> |
+ | The user should NEVER disconnect the control cable from the scanner or driver while power is applied ("hot swapping" | ||
- | ===Connections and Controls=== | + | 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 |
- | <WRAP left round box 500px> | + | |
- | 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 | + | |
Please allow 1 to 2 minutes for the SEEOR to temperature stabilize. | Please allow 1 to 2 minutes for the SEEOR to temperature stabilize. | ||
Now the beam steerer is ready for steering. | Now the beam steerer is ready for steering. | ||
- | Figure 5: LS-105 front panel. | + | <WRAP left round box 100%>[{{ : |
- | Front Panel Controls (from left to right): | + | Front Panel Controls (from left to right) |
- | • Power Switch: | + | |Power Switch|This turns the unit on. Up is on and down is off.| |
- | • Power LED: | + | |Power LED|This is on when the unit is on.| |
- | • Temperature LED: | + | |Temperature LED|This LED turns green when the temperature is stabilized.| |
- | • Optical Head: High Voltage and temperature control output connector. | + | |Optical Head|High Voltage and temperature control output connector.| |
- | • Horizontal: User can input the external signal. Maximum voltage should not exceed ±10 V. Input impedance is 1 MΩ. This input will steer the beam horizontally. | + | |Horizontal|User can input the external signal. Maximum voltage should not exceed ±10 V. Input impedance is 1 M Ω. This input will steer the beam horizontally.| |
- | • Vertical: User can input the external signal. Maximum voltage should be held within 0 to +10 V. Input impedance is 1 MΩ. This input will steer the beam vertically. | + | |Vertical|User can input the external signal. Maximum voltage should be held within 0 to +10 V. Input impedance is 1 MΩ. This input will steer the beam vertically.| |
- | + | </WRAP> | |
- | Figure 8: SEEOR 205 back panel. | + | |
- | Back panel Controls (from left to right): | + | |
- | • 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. | + | |
- | • Power In: Power the driver with the AC adapter that is included with the package. | + | |
- | =====Advanced Settings===== | + | |
- | 3.3. 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. | + | |
- | 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 and ringing), and limited current output. As shown on the left of Figure 9, 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/s, which is beyond the capabilities of most amplifiers when driving a capacitive load. The right hand side of Figure 9 shows an ideal square wave and its associated constant E-field magnitude. Figure 10 plots an example waveform from an LS-105. | + | |
+ | <WRAP left round box 100%> | ||
+ | Back panel Controls (from left to right) | ||
+ | |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.| | ||
+ | |Power In|Power the driver with the AC adapter that is included with the package.| | ||
+ | </ | ||
+ | =====Advanced Settings===== | ||
+ | ====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.\\ | ||
+ | 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, | ||
+ | <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. | ||
+ | | ||
+ | <WRAP center round box 450px> | ||
+ | </ | ||
+ | ====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. | ||
- | + | <WRAP center round box 450px> | |
- | 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. | + | </ |
- | + | ====Internal Factory-Set Trim Pots==== | |
- | 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. In the SEEOR, the internal construction is inherently asymmetric. | + | |
- | + | ||
- | 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. | 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 | + | 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 |
- | Also shown in Figure | + | Also shown in Figure |
- | + | ||
- | Figure | + | <WRAP center round box 450px> |
+ | </ | ||
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> |
- | + |