JP2018136567A - Adaptive optics liquid crystal array device having meander resistors - Google Patents

Abstract

An AO actuator that is compact, lightweight, high power over an aperture or at least constant pixel speed, high power, and works well with a discontinuous in-phase wavefront. A liquid crystal adaptive optical actuator comprises a two-dimensional array of pixels, each pixel being connected to a control circuit by control line signal paths 16, 20, the control line signal path being connected to an electrical interconnect 16 and a serpentine resistor. And each resistor has a resistance value selected to equalize the RC time constant of each control line signal path associated with each pixel. Thus, each control line can carry one or more control signals, and the control line signal path is configured so that all pixels respond to the control signal with a uniform response time. [Selection] Figure 1

Description

  The structures and techniques described herein relate to optical transceiver systems, and more specifically to free space laser / optical transceiver systems.

  As is well known in the art, adaptive optics (AO) actuators provide a means to correct the in-phase wavefront at the pixel unit level.

  As is also known, conventional AO actuators operate as so-called “reflection mode” elements and are typically implemented via deformable mirrors or MEMS mirrors. With the exception of liquid crystal cells, all known techniques for realizing AO are essentially limited to reflection mode operation.

  The use of reflective mode AO elements often results in an unnecessarily complicated optical layout. Furthermore, reflective mode AO actuators are generally larger and heavier than desired for many applications. In addition, such reflection mode AO actuators are not as fast as desired, do not deal with in-phase wavefronts with phase discontinuities, do not have sufficient spatial resolution, and have high levels of light Does not deal with strength.

  In addition, all machine-based AOs suffer from inter-actuator modulation, whereby certain pixel settings affect adjacent pixel settings. This prevents such AOs from correcting wavefronts with discontinuous phases that are common in the atmosphere with high levels of turbulence. MEMS-based devices (such as those manufactured by Boston Micromachines, etc.) provide a minimum known inter-actuator coupling of about 13%.

  Prior art transmissive AOs based on liquid crystal technology that use mechanical AOs to alleviate some difficulties are known but suffer from low bandwidth and variable response time from pixel to pixel.

  Accordingly, in a preferred transmission mode embodiment, it is possible to provide an AO actuator that is compact, lightweight, high power over the aperture or at least constant pixel speed, high power, and works well with a discontinuous in-phase wavefront. Would be desirable.

  According to the concepts, systems, components, and techniques described herein, an adaptive optical actuator includes a two-dimensional array of pixels, each of which includes a serpentine resistor, each serpentine resistor layout. Is selected to provide a uniform time constant for all pixels across the aperture.

  By using this particular arrangement, adaptive optics is provided with a specially designed electrode layout that provides a uniform time constant for all pixels across the aperture.

  According to the concepts, systems, components, and techniques described herein, the adaptive optical actuator includes a two-dimensional array of pixels, each of which is selected to equalize the RC rise time for that pixel. A resistor having a resistance value is provided.

  According to the concepts, systems, components, and techniques described herein, an adaptive optical actuator is an array of pixels, each of the pixels having a front plate having an inner surface and facing the front plate surface. Provided with a substrate having an inner surface, wherein the substrate and the front plate are formed thereon and arranged as electrodes that allow different voltages to be applied to each pixel. An array of pixels having an electrically conductive structure and an electrical signal path capable of carrying one or more control signals and coupled to each pixel in the array of pixels, each substantially The electrode signal path provided such that a uniform time constant has a path length and resistance as provided to all pixels across the array of pixels.

    An adaptive optical actuator comprising an array of two-dimensional pixels, each pixel having an associated control line signal path electrically coupled to that pixel, each control line signal path being associated An adaptive optical actuator comprising a resistor having a resistance value selected to equalize the RC rise time for a given pixel. By using this arrangement, each control line can carry one or more control signals, and the control line signal path is configured so that a uniform time constant is provided for all pixels across the array of pixels. The

  In one embodiment, the pixels are provided to have a square cross-sectional shape to better support the intended use of AO with a square beam.

  As mentioned above, in some embodiments, an electrode layout is used that provides a uniform time constant for all pixels across the aperture. In optical applications where a square beam is used, the pixels are square to better support the intended use of AO with a square beam. Of course, it is to be understood that the concepts, systems, and techniques described herein are not limited to square beams, and any beam shape may be used.

The foregoing features of the circuits and techniques described herein may be more fully understood from the following description of the drawings.
1 and 2 are a series of plan views of an electrically active substrate of an adaptive optical (AO) actuator. 1 and 2 are a series of plan views of an electrically active substrate of an adaptive optical (AO) actuator. 3 and 4 are a series of plan views of a portion of the AO actuator shown in FIGS. 3 and 4 are a series of plan views of a portion of the AO actuator shown in FIGS. 4A is an enlarged view of a part of FIG. FIG. 4B is an enlarged view of a part of FIG. 4A.

  Referring now to FIGS. 1-4B, where identical elements are provided to have the same reference symbols throughout the several figures, adaptive optics (AO) is generally as known in the art. A voltage addressable transmission mode having a substrate 12 patterned in an array of independent pixels, generally indicated as 14, and supporting two-dimensional (2-D) addressing for use as an AO actuator A liquid crystal (LC) cell is provided. In addition to each pixel denoted by reference numeral 14, each individual pixel in FIGS. 1-4B also includes a unique alphanumeric symbol (eg, A1-A4, B1-B12, C1-C20, D1-D28, E1-E36). , F1-F44, G1-G40).

  In the exemplary embodiment of FIGS. 1-4B, the adaptive optics provided has a variety of shapes (squares and triangles) and a plurality of pixels arranged in columns and rows. Each of the pixels is coupled to a corresponding one of the outputs of a control circuit (not shown in FIGS. 1-4B). Note that the control circuit can be placed on the substrate of the LC via “flip chip” or other chip-on-glass assembly techniques, or the control circuit can be “out of glass”. The control circuit is coupled to the pixel 14 via an electrical signal path that couples a control signal to a conductor disposed on the substrate. Electrical transition 16 and compensation resistor 20 (also referred to as RC balance resistor) form part of such a signal path to pixel 14. Such a signal path may also include, for example, a flex cable coupled to a controller or other signal source (not visible in FIG. 1). Each pixel 14 is individually very thin and not clearly shown in the figure, but via a lead that extends from each compensation resistor to its corresponding pixel and is routed into a narrow gap between the pixels. Note that it is addressable. Thus, the control circuit can provide one or more control signals to each of the AO pixels.

  Each signal path coupled between the flex circuit and the pixel generally includes an RC balanced resistor, shown as 20. In a preferred embodiment, the resistors are provided to have a serpentine resistor layout (FIG. 4B). The path length within the serpentine resistor layout is selected to provide a substantially uniform speed when controlling pixels across the array. That is, the time required for any pixel in the AO pixel array to respond to the control signal is substantially the same regardless of the pixel location in the AO. Since these response times are equal, any effects (such as RMS voltage drop resulting from delay and decay between the voltage source and the pixel) are made equal across the entire pixel and are already needed for any liquid crystal device. Will enable compensation for such voltage drops in the calibration table.

Referring now to FIGS. 3-4B, as described above, AO includes a specially designed electrode layout that provides a uniform time constant for all pixels across the aperture. As can be seen most clearly in FIG. 4B, a serpentine resistor layout is used to achieve the desired uniform time constant. Each pixel has a known capacitance in advance given its area and device thickness and liquid crystal properties, so the resistors are designed to have the same R _i C _i product. Get (i moves across all pixels). Usually the pixel with the largest product (the “latest” pixel, eg one of the pixels in the center of the aperture, which has its longest connection to the edge of the aperture and hence the most resistive Determine the resistance and capacitance. Here, for this pixel numbered pixel number 1, it has a certain value of R ₁ C ₁ . The serpentine resistor chosen for this pixel will have a minimum resistance, preferably zero resistance. That is, it will not be in the board layout. Its inherent R _i0 C _i (with no added compensation resistor, with pixel capacitance C _i and resistor R _i0 for connection from the edge of the aperture to the pixel) is therefore less than R ₁ C ₁ For each of the other pixels, a compensation resistor is included in series with the connection. Thus, all pixels are “decelerated” so that they all have substantially the same RC response time.

  The approach described above makes it possible to compensate for the effects of voltage decay in the RC network in a uniform manner for all pixels, and allows the use of a single calibration table for all pixels, This is a very desirable feature to gain control. Compensation resistor 20 is placed in a front glue line (ie, a space where sealant or “glue” is arranged to form sidewalls and couple the superstrate to the substrate). Resistor 20 may be coupled via a connection element 16 that provides a transition to the outer lead-out leads (and ultimately the flex circuits 18a, 18b and controller). As can be clearly seen in FIGS. 3 and 4, a total of eight serpentine resistor layout cell types are required for one quarter pixel of AO.

  As described above, an electrode layout is used that provides a uniform time constant for all pixels across the aperture. In optical applications where a square beam is used, the pixel is square to better support the intended use of AO with a square beam. Of course, it is to be understood that the concepts, systems, and techniques described herein are not limited to square beams, and any beam shape may be used. Similarly, AOs with pixel geometries that differ from squares may employ compensating resistors designed according to the present teachings. For example, a hexagonally packed array is a useful geometric shape for AO, as is known in the art. The feed line for the pixel is of variable length and is longer for the center pixel, so the compensation resistor technique taught herein is applicable to equalize the response time, Hence, it allows a more convenient drive voltage circuit with the same calibration table for all pixels.

  Although one or more preferred embodiments of the circuits, techniques, and concepts described herein have been described, it is now possible that other embodiments incorporating these circuits, techniques, and concepts can be used. Will be apparent to those skilled in the art. Thus, it is contemplated that the scope of the patent should not be limited to the described embodiments, but rather should be limited only by the spirit and scope of the appended claims.

Claims (10)

An adaptive optical actuator,
A two-dimensional array of pixels;
With multiple electrical signal paths,
Each of the plurality of electrical signal paths is coupled to one of the pixels in the array of two-dimensional pixels, and each electrical signal path is capable of carrying one or more control signals;
Each of the plurality of electrical signal paths includes a compensation resistor for providing a uniform time constant to all pixels across the two-dimensional array of pixels, the compensation resistor being provided as a serpentine resistor signal path. To be
Adaptive optical actuator.   Each of the plurality of electrical signal paths corresponds to a serpentine resistor signal path, and the layout of each serpentine resistor signal path is selected to provide a uniform time constant for all pixels across the aperture. 2. The adaptive optical actuator according to 1. Each of the pixels in the two-dimensional array of pixels is
A front plate having an inner surface;
A liquid crystal cell comprising: a substrate having an inner surface facing the surface of the front plate;
The adaptive optical actuator according to claim 1, wherein the plurality of electrical signal paths are disposed on one of the substrate and the front plate.   4. The adaptive optical actuator of claim 3, wherein the liquid crystal cell is provided as a voltage addressable transmission mode liquid crystal cell.   The adaptive optical actuator of claim 1, wherein at least some of the pixels are provided to have a shape corresponding to at least one of a square cross-sectional shape and / or a triangular cross-sectional shape.   The adaptive optical actuator of claim 1, wherein the compensation resistor is provided as a serpentine resistor signal path.   The adaptive optical actuator of claim 1, wherein each serpentine resistor signal path is provided with a resistance value selected to equalize the RC rise time for its associated pixel. An adaptive optical actuator having a two-dimensional array of pixels,
Each of the pixels has an associated control line electrically coupled to the pixel;
Each control line includes a compensation resistor for providing a uniform time constant to all pixels in the two-dimensional pixel array, the compensation resistor being provided as a serpentine resistor signal path;
Adaptive optical actuator. Each of the pixels in the two-dimensional array of pixels is provided from a liquid crystal cell comprising a front plate having an inner surface and a substrate having an inner surface facing the surface of the front plate;
A plurality of electrical signal paths are disposed on one of the substrate and the front plate,
The liquid crystal cell is provided as a voltage-addressable transmission mode liquid crystal cell,
At least some of the pixels are provided to have a shape corresponding to at least one of a square cross-sectional shape and / or a triangular cross-sectional shape;
The adaptive optical actuator according to claim 8. Each serpentine resistor signal path comprises a resistor having a resistance value selected to equalize the RC rise time for the associated pixel.
The adaptive optical actuator according to claim 8.

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