Apparatus and method for optical component alignment

Abstract

To provide an apparatus and method for optical component alignment.SOLUTION: An apparatus and method for aligning optical components such as mirrors to facilitate proper beam alignment using an image integration optical system is used to integrate images from multiple optical features, such as from both left and right mirror banks, to present the images simultaneously to a camera system. A fluorescent material may be used to render a beam footprint visible and the relative positions of the footprint and an alignment feature may be used to align the optical feature.SELECTED DRAWING: Figure 9B

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. patent application Ser. No. 63 / 072,390, entitled "APPARATUS FOR AND METHOD OF OPTICAL COMPONENT ALIGNMENT," filed Aug. 31, 2020, and incorporated by reference in its entirety into this specification.

[0002] The present disclosure relates to systems and methods for aligning optical components used, for example, in lithographic apparatus, and in particular to components of an optical pulse stretcher useful for stretching the pulse of the output of a laser source. [Background technology]

[0003]

[0003] A lithographic apparatus applies a desired pattern onto a substrate, such as a wafer of semiconductor material, typically onto a target portion of the substrate. A patterning device, alternatively called a mask or reticle, may be used to generate the circuit pattern formed on an individual layer of the wafer. Transfer of the pattern is typically achieved by imaging onto a layer of radiation-sensitive material (resist) provided on the substrate. Generally, a single substrate will contain adjacent target portions that are successively patterned.

[0004]

[0004] Lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing the entire pattern onto the target portion in one go, and so-called scanners, in which each target portion is irradiated by scanning the pattern with a radiation beam in a given direction (the "scan" direction) while synchronously scanning the substrate parallel or anti-parallel to this direction. It is also possible to transfer the pattern from the patterning device to the substrate by imprinting the pattern onto the substrate. For simplicity, both steppers and scanners will be referred to herein simply as scanners.

[0005]

[0005] The light source used to illuminate and project the pattern onto the substrate may be any of several configurations. Deep ultraviolet excimer lasers commonly used in lithography systems include krypton fluoride (KrF) lasers with a wavelength of 248 nm and argon fluoride (ArF) lasers with a wavelength of 193 nm. The laser source may include an optical pulse stretcher for stretching the pulse of the output of a high power gas discharge laser system.

[0006]

[0006] Newer requirements for lithography scanner performance require longer pulse lengths, as measured by the time integral square (TIS) of the pulse length. For example, improving edge placement error (EPE) of chip features requires a longer TIS. Optical pulse stretchers (OPuS) are used to stretch the pulse to achieve the desired TIS. Increasing the TIS requires a larger OPuS. Increasing the size of the OPuS makes it even more important that the components of the OPuS are in proper optical alignment.

[0007]

[0007] The conventional method of aligning OPuS components involves opening the OPuS enclosure and physically positioning a target card near the optical surface of the component to be aligned. The incoming beam is then aligned based on the landing position of the beam on the target card. The target card is then moved to the next optical component requiring alignment until all of the optical components requiring alignment are properly aligned.

[0008]

[0008] This alignment process, sometimes called open beam paper target alignment, requires opening a sealed laser enclosure to place the card. It entails the risk of open beam operation and needs to be performed very carefully to avoid exposing the aligner's skin to UV radiation. It is also time consuming and requires a great deal of manipulation and other manual operations. It exposes the optical surfaces being aligned to contamination, which can result in reduced optical life of critical optical components. Furthermore, the complexity of establishing the beam alignment target and the subjective judgment of the beam position make it difficult to achieve accurate alignment. Summary of the Invention

[0009]

[0009] The following presents a brief summary of one or more embodiments to provide a basic understanding of the embodiments. This summary is not an extensive summary of all contemplated embodiments, and is not intended to identify key or essential elements of all embodiments or to delineate the scope of any or all embodiments. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to the more detailed description that is presented below.

[0010] According to certain aspects of an embodiment, a camera system is used to monitor the beam position on the OpuS components, such as mirrors, to facilitate correct beam alignment. In some embodiments, an image integration optical system is used to integrate images from multiple optical features, such as from both the left and right mirror banks, to simultaneously present the images to the camera system. This simplifies the design and avoids the expense of having multiple cameras to inspect the features individually. According to certain aspects of an embodiment, the camera system is placed outside the purge volume of the OPuS enclosure to reduce the risk of open beam operation and to avoid disruption of the purge. As used herein, the term "camera" is intended to encompass any device, system, or arrangement for capturing (transducing) an image.

[0011] According to aspects of certain embodiments, during alignment, the landing position of the beam as revealed by the "fluorescence footprint" is positioned to coincide with or overlap an alignment feature of the component being aligned. For example, if the optical component is a dichroic mirror in OPuS, the alignment feature may be located on the back support plate via the dichroic mirror to facilitate positioning of the beam.

[0012]

[0012] Thus, according to some embodiments, the use of a camera system minimizes the amount of open beam manipulation required during alignment. This significantly improves the safety of the alignment procedure. The non-contact nature of this alignment system also reduces the risks inherent in direct close optics handling, including the risk of surface contamination. This system also allows for a significant reduction in field service time for OPuS modules by eliminating the need to open enclosures to break purges and the need for manual target positioning.

[0013] According to an aspect of an embodiment, an optical component is disclosed that includes a sealed enclosure including a window that transmits visible light, a first optical feature positioned at a first location within the enclosure, a second optical feature positioned at a second location within the enclosure, and an image integration module arranged to receive the first optical feature light from the first optical feature and the second optical feature light from the second optical feature, and adapted to redirect the first optical feature light and the second optical feature light through the window to form an image from the first optical feature light juxtaposed with an image from the second optical feature light. The optical component may be an optical pulse stretcher. The first optical feature may include a first mirror, and the second optical feature may include a second mirror. The first mirror may include a first concave dichroic mirror, and the second mirror may include a second concave dichroic mirror. The first optical feature and the second optical feature may be positioned substantially symmetrically with respect to the image integration module.

[0014] According to another aspect of an embodiment, the image integration module may include a first reflective surface arranged to redirect light from the first optical feature and a second reflective surface arranged to redirect light from the second optical surface. The first reflective surface may include a first prism reflective surface of a first prism, and the second reflective surface may include a second prism reflective surface of a second prism. The image integration module may include a prism having a first reflective surface oriented toward the first optical feature and a second reflective surface oriented toward the second optical feature. The image integration module may include two flat chamfered mirrors.

[0015]

[0015] According to another aspect of an embodiment, the optical component may further include a third optical feature positioned at a third location within the enclosure and a fourth optical feature positioned at a fourth location within the enclosure, and the image integration module may be positioned to receive the third optical feature light from the third optical feature and the fourth optical feature light from the fourth optical feature and adapted to combine and redirect the third optical feature light and the fourth optical feature light through the window to form an image from the third optical feature light adjacent to the image from the fourth optical feature light.

[0016] According to another aspect of an embodiment, the optical component may further include a camera system arranged to receive the first optical feature light and the second optical feature light through the window. The camera system may include a lens system arranged to receive the first optical feature light and the second optical feature light through the window, and a camera arranged to receive the first optical feature light and the second optical feature light from the lens system. The optical component may further include a folding mirror optically positioned between the image integration module and the window for redirecting an optical path of the first optical feature light and the second optical feature light.

[0017]

[0017] According to another aspect of an embodiment, at least one of the first optical feature and the second optical feature may be adjustable, and may further include an actuator mechanically coupled to at least one of the first optical feature and the second optical feature for adjusting an orientation of at least one of the first optical feature and the second optical feature.

[0018] According to another aspect of an embodiment, the first optical feature may include a first fluorescent material and a first alignment feature, and the second optical feature may include a second fluorescent material and a second alignment feature. The first optical feature may include a first mirror including a first substrate that transmits visible light, a first reflective coating that reflects UV radiation, and a first mirror support, and the second optical feature may include a second mirror including a second substrate that transmits visible light, a second reflective coating that reflects UV radiation, and a second mirror support. The first mirror support may include a first alignment feature on a front surface of the first mirror support, and the second mirror support may include a second alignment feature on a front surface of the second mirror support. The first alignment feature can coincide with a position of an aligned beam footprint on the first mirror, and the second alignment feature can coincide with a position of an aligned beam footprint on the second mirror.

[0019]

[0019] According to another aspect of an embodiment, the first optical feature may include a first reflective coating including a first fluorescent material and the second optical feature may include a second reflective coating including a second fluorescent material. The first fluorescent material may be provided on a back surface of the first substrate and the second fluorescent material may be provided on a back surface of the second substrate. The first fluorescent material may be provided on a front surface of the first mirror support and the second fluorescent material may be provided on a front surface of the second mirror support. The first mirror support may include the first fluorescent material and the second mirror support may include the second fluorescent material.

[0020]

[0020] According to another aspect of an embodiment, a system includes an enclosed enclosure including a window that transmits visible light, a first optical feature positioned within a first field of view within the enclosure, a second optical feature positioned within the first field of view within the enclosure, and an image integration module positioned to receive the first field of view light from the first field of view and adapted to combine and redirect the first field of view light through the window, wherein the image integration module is

number

[0021]

[0021] According to another aspect of an embodiment, a method of aligning a plurality of optical features disposed within a sealed enclosure having a window is disclosed that includes combining light from each of the optical features to generate a combined optical signal, directing the combined optical signal outside the enclosure through the window, and aligning at least some of the plurality of optical features based at least in part on the combined optical signal. The method may further include imaging the combined optical signal using a camera system positioned outside the sealed enclosure and positioned to receive the combined optical signal after directing the combined optical signal outside the enclosure through the window. Each of the plurality of optical features may include an alignment feature and a fluorescent material arranged to generate a visible footprint of a UV beam impinging on the optical feature, and the method may further include exposing each of the optical features to a UV radiation beam and generating an illumination footprint of the UV radiation beam on each of the optical features prior to combining light from each of the optical features to generate a combined optical signal, and aligning at least some of the plurality of optical features based at least in part on the combined optical signal may include aligning at least some of the plurality of optical features based at least in part on a positional relationship of the illumination footprint and the alignment feature for each optical feature. The aligning may include adjusting one or more of the plurality of optical features. The adjusting one or more of the plurality of optical features may include manually manipulating one or more actuators mechanically coupled to one or more of the plurality of optical features, respectively. The adjusting one or more of the plurality of optical features may include providing a signal to actuate one or more motorized actuators mechanically coupled to one or more of the plurality of optical features, respectively. Adjusting one or more of the plurality of optical features may include adjusting an orientation of one or more of the plurality of optical features.

[0022]

[0022] Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Further embodiments will be apparent to those skilled in the art based on the teachings contained herein.

[0023]

[0023] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate by way of example and not by way of limitation the methods and systems of embodiments of the present invention. Together with the detailed description of the invention, the drawings further serve to explain the principles of the methods and systems presented herein and to enable those skilled in the art to make and use the methods and systems presented herein. In the drawings, like reference numbers indicate identical or functionally similar elements. [Brief description of the drawings]

[0024] [Figure 1]

[0024] A schematic diagram, not to scale, of the overall broad concept of a photolithography system in accordance with one aspect of the disclosed subject matter is shown. [Diagram 2]

[0025] 1 shows a schematic diagram, not to scale, of the overall broad concept of a laser system used in a lithography system, in accordance with an aspect of the disclosed subject matter. [Diagram 3]

[0026] FIG. 1 is a diagram of an optical pulse stretcher in accordance with an aspect of the disclosed subject matter. [Figure 4]

[0027] 1 illustrates various optical paths within an optical pulse stretcher in accordance with an aspect of the disclosed subject matter. [Figure 5A]

[0028] 1 illustrates various optical paths within an optical pulse stretcher in accordance with an aspect of the disclosed subject matter. [Figure 5B] FIG. 2 illustrates various optical paths within an optical pulse stretcher in accordance with an aspect of the disclosed subject matter. [Figure 6]

[0029] FIG. 13 is a partial perspective view of a mirror arrangement on one side of an optical pulse stretcher in accordance with an aspect of the disclosed subject matter. [Figure 7]

[0030] FIG. 1 illustrates a conventional method for aligning optical features in an optical component. [Figure 8A]

[0031] FIG. 1 illustrates a system for aligning optical features according to an aspect of the disclosed subject matter. [Figure 8B] FIG. 1 illustrates a system for aligning optical features according to an aspect of the disclosed subject matter. [Figure 9A]

[0032] FIG. 1 illustrates a system for aligning optical features according to an aspect of the disclosed subject matter. [Figure 9B]

[0033] 1 illustrates juxtaposition of images in a system for aligning optical features in accordance with an aspect of the disclosed subject matter. [Figure 10]

[0034] FIG. 1 illustrates conditions for achieving maximum field of view, according to certain aspects of the disclosed subject matter. [Figure 11A]

[0035] 1 illustrates alternative components of an image merging module in accordance with an aspect of the disclosed subject matter. [Figure 11B] 1 illustrates alternative components of an image merging module according to an aspect of the disclosed subject matter. [Figure 11C]

[0036] 13A-13C illustrate the effect of arrangement of components within an optical image synthesis module on the field of view, in accordance with an aspect of the disclosed subject matter. [Figure 12A]

[0037] FIG. 1 illustrates a system for aligning optical features according to an aspect of the disclosed subject matter. [Figure 12B]

[0038] 1 illustrates juxtaposition of images in a system for aligning optical features in accordance with an aspect of the disclosed subject matter. [Figure 13A]

[0039] 1 illustrates one embodiment of a configuration of an optical feature according to an embodiment of the disclosed subject matter. [Figure 13B]

[0039] An embodiment of the structure of an optical feature according to an embodiment of the disclosed subject matter is shown. [Figure 13C]

[0039] An embodiment of the structure of an optical feature according to an embodiment of the disclosed subject matter is shown. [Figure 13D]

[0039] An embodiment of the structure of an optical feature according to an embodiment of the disclosed subject matter is shown. [Figure 14A]

[0040] 1 illustrates one embodiment of a configuration of an optical feature according to an embodiment of the disclosed subject matter. [Figure 14B]

[0040] An embodiment of the structure of an optical feature according to an embodiment of the disclosed subject matter is shown. [Figure 14C]

[0040] An embodiment of the structure of an optical feature according to an embodiment of the disclosed subject matter is shown. [Figure 14D]

[0040] An embodiment of the structure of an optical feature according to an embodiment of the disclosed subject matter is shown. [Figure 15A]

[0041] 1 illustrates the relative positioning of a UV footprint and an alignment mark before an alignment process, according to an embodiment of the disclosed subject matter. [Figure 15B]

[0041] Figure 1 illustrates the relative positioning of the UV footprint and alignment marks after an alignment process, according to an aspect of the disclosed subject matter. [Figure 16]

[0042] 1 is a flowchart illustrating a method for aligning optical features in an optical component according to an aspect of the disclosed subject matter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025]

[0043] Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited to the specific embodiments described herein. Such embodiments are presented herein for illustrative purposes only. Further embodiments will be apparent to those skilled in the art based on the teachings contained herein.

[0026]

[0044] This specification discloses one or more embodiments incorporating the features of the present invention. The disclosed embodiment or embodiments are merely exemplary of the present invention. The scope of the present invention is not limited to the disclosed embodiment or embodiments. The present invention is defined by the claims appended hereto.

[0027]

[0045] References to one or more described embodiments, and to "one embodiment," "an embodiment," "an example embodiment," "an exemplary embodiment," and the like in this specification indicate that one or more described embodiments may include a particular feature, structure, or characteristic, but that all embodiments may not necessarily include that particular feature, structure, or characteristic. Also, such expressions do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in the context of one embodiment, it is understood that it is within the knowledge of one of ordinary skill in the art to cause such feature, structure, or characteristic to occur in the context of other embodiments, whether or not explicitly described.

[0028]

[0046] Spatially relative terms such as "beneath," "below," "lower," "above," "on," "upper," "left," "right," and the like may be used herein for convenience of description to describe the relationship of one element or feature to another element or features as shown in the drawings. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation shown in the drawings. The device may be oriented differently (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may be similarly interpreted accordingly.

[0029]

[0047] Before describing specific embodiments in more detail, it is useful to illustrate an example environment in which embodiments of the invention may be implemented. With reference to Figure 1, a photolithography system 100 includes an illumination system 105. As will be described more fully below, the illumination system 105 includes a light source that generates a pulsed light beam 110 and directs it to a photolithography exposure tool or scanner 115 that patterns microelectronic features on a wafer 120. The wafer 120 is positioned on a wafer table 125 that is connected to a positioner (not shown) that is constructed to hold the wafer 120 and configured to precisely position the wafer 120 according to certain parameters.

[0030]

[0048] The photolithography system 100 uses a light beam 110 having a wavelength in the deep ultraviolet (DUV) range, for example, 248 nanometers (nm) or 193 nm. The minimum size of a microelectronic feature that can be patterned on the wafer 120 depends on the wavelength of the light beam 110, with lower wavelengths allowing for smaller minimum feature sizes. If the wavelength of the light beam 110 is 248 nm or 193 nm, the minimum size of the microelectronic feature can be, for example, 50 nm or less. The bandwidth of the light beam 110 can be the actual instantaneous bandwidth of its optical spectrum (or emission spectrum), which includes information about how the optical energy of the light beam 110 is distributed across different wavelengths. The scanner 115 includes an optical arrangement having, for example, one or more focusing lenses, a mask, and an objective arrangement. The mask can be moved along one or more directions, such as along the optical axis of the light beam 110 or in a plane perpendicular to the optical axis. The objective arrangement includes a projection lens and allows image transfer to occur from the mask to the photoresist on the wafer 120. The illumination system 105 adjusts the angular range of the light beam 110 that impinges on the mask and also homogenizes the intensity distribution of the light beam 110 across the mask.

[0031]

[0049] The scanner 115 may include, among other features, a lithography controller 130, air conditioning devices, and power sources for various electrical components. The lithography controller 130 controls how layers are printed on the wafer 120. The lithography controller 130 includes memory that stores information such as process recipes. The process program or recipe determines the length of exposure to the wafer 120 based on, for example, the mask used and other factors that affect the exposure. During lithography, multiple pulses of the light beam 110 illuminate the same area of ​​the wafer 120 to constitute an illumination dose.

[0032]

[0050] Photolithography system 100 also preferably includes a control system 135. Generally, control system 135 includes one or more of digital electronic circuitry, computer hardware, firmware, and software. Control system 135 also includes memory, which may be read-only memory and / or random-access memory. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including, by way of example, semiconductor memory devices such as EPROM, EEPROM, and flash memory devices, magnetic disks such as internal hard disks and removable disks, magneto-optical disks, and CD-ROM disks.

[0033]

[0051] The control system 135 may also include one or more input devices (such as a keyboard, touch screen, microphone, mouse, handheld input device, etc.) and one or more output devices (such as a speaker or monitor). The control system 135 may also include one or more programmable processors and one or more computer programs tangibly embodied in a machine-readable storage device for execution by the one or more programmable processors. Each of the one or more programmable processors may execute a program of instructions to perform a desired function by performing operations on input data and generating appropriate output. In general, a processor receives instructions and data from a memory. Any of the above may be supplemented by or incorporated in specially designed ASICs (application specific integrated circuits). The control system 135 may be centralized or partially or wholly distributed throughout the photolithography system 100.

[0034]

[0052] Referring to Figure 2, an exemplary laser source system in illumination system 105 is a pulsed laser source that generates a pulsed laser beam as light beam 110. Figure 2 illustrates, illustratively and in block diagram form, a gas discharge laser system in accordance with an embodiment of certain aspects of the disclosed subject matter. The gas discharge laser system may include, for example, a solid-state or gas discharge seed laser system 140, an amplification stage, for example, a power ring amplifier ("PRA") stage 145, relay optics 150, and a laser system output subsystem 160. Seed system 140 may include, for example, a master oscillator ("MO") chamber 165.

[0035]

[0053] The seed laser system 140 may also include a master oscillator output coupler ("MO OC") 175, which may include a partially reflective mirror that, together with a reflective grating (not shown) in a line narrowing module ("LNM") 170, forms an oscillator cavity in which the seed laser 140 oscillates to form the seed laser output pulse, i.e., to form the master oscillator ("MO"). The system may also include a line-center analysis module ("LAM") 180. The LAM 180 may include an etalon spectrometer for precision wavelength measurement, and a grating spectrometer for coarser resolution. The MO wavefront engineering box ("WEB") 185 can function to redirect the output of the MO seed laser system 140 towards the amplification stage 145 and can include, for example, beam expanding, e.g., using a multi-prism beam expander (not shown), and coherence busting, e.g., in the form of an optical delay path (not shown).

[0036]

[0054] The amplification stage 145 may include, for example, a PRA lasing chamber 200, which may also be an oscillator formed by seed beam injection and output coupling optics (not shown), which may be incorporated into, for example, a PRA WEB 210, and which may be redirected back through a gain medium in the chamber 200 by a beam reverser 220. The PRA WEB 210 may incorporate partially reflective input / output couplers (not shown) for a nominal operating wavelength (e.g., approximately 193 nm for an ArF system) and one or more prisms and maximum reflecting mirrors.

[0037]

[0055] A bandwidth analysis module ("BAM") 230 at the output of the amplification stage 145 receives the pulsed output laser light beam from the amplification stage and can pick off a portion of the light beam for metrology purposes (e.g., to measure the output bandwidth and pulse energy). The pulsed laser output light beam then passes through an optical pulse stretcher ("OPuS") 240 and an output combined autoshutter metrology module ("CASMM") 250, which can also be the location of a pulse energy meter. One purpose of the OPuS 240 can be, for example, to convert a single output laser pulse into a pulse train. Secondary pulses created from the original single output pulse can be delayed relative to each other. By distributing the original laser pulse energy into a train of secondary pulses, the effective pulse length of the laser can be extended and at the same time the peak pulse intensity can be reduced. Thus, the OPuS 240 can receive the laser beam from the PRA WEB 210 via the BAM 230 and direct the output of the OPuS 240 to the CASMM 250. In other embodiments, other suitable arrangements may be used.

[0038]

[0056] The PRA lasing chamber 200 and MO 165 are configured as chambers in which a discharge between electrodes can create a lasing gas discharge within the lasing gas to create a population inversion of energetic molecules including, for example, Ar, Kr, and / or Xe to produce a relatively broadband radiation that can be line narrowed to a relatively very narrow bandwidth and center wavelength selected in a line narrowing module (“LNM”) 170, as is known in the art.

[0039]

[0057] Tuning typically occurs within the LNM. A common technique used to line narrow and tune the laser is to provide a window behind the laser's discharge cavity through which a portion of the laser beam enters the LNM. There, a portion of the beam is expanded using a prism beam expander and directed to a grating that reflects a narrow, selected portion of the laser's broader spectrum back into the discharge chamber where it is amplified. The laser is typically tuned by changing the angle at which the beam illuminates the grating using an actuator, such as a piezo actuator.

[0040]

[0058] In operation, OPuS 240 stretches an excimer or other gas discharge laser (eg, a molecular fluoride gas discharge laser) having a given pulse length and TIS into a longer pulse with several peaks and a larger TIS.

[0041]

[0059] 3 is a schematic diagram of a front view of an example of an optical pulse stretcher 401 having a first optical pulse stretcher 401a and a second optical pulse stretcher 401b in accordance with some embodiments of the present disclosure. The optical pulse stretcher 401 receives an input beam pulse 411, stretches it, and outputs a stretched output beam pulse 413.

[0042]

[0060] According to some embodiments, and as described in more detail below, the second optical pulse stretcher 401b may include two or more (e.g., three) stages of a confocal optical pulse stretcher. In some examples, these three stages of a confocal optical pulse stretcher may be positioned approximately parallel to one another in the second optical pulse stretcher 401b. In some embodiments, the second optical pulse stretcher 401b may be positioned perpendicular or approximately perpendicular to the first optical pulse stretcher 401a. That is, in some embodiments, the first optical pulse stretcher 401a (e.g., an orthogonal optical pulse stretcher that may be positioned vertically) is positioned perpendicular or approximately perpendicular to the two or more (e.g., three) stages of a confocal optical pulse stretcher of the second optical pulse stretcher 401b, which are positioned vertically in the drawing. According to some embodiments, the second optical pulse stretcher 401b is designed to provide additional optical delay.

[0043]

[0061] According to some embodiments, the expanded optical pulse stretcher 401 combines two or more confocal optical pulse stretchers. For example, the expanded optical pulse stretcher 401 combines confocal optical pulse stretchers with combinations of 4 bounces, 4 bounces, 12 bounces, and 12 bounces per optical circuit configuration. According to some embodiments, the inclusion of combinations of different mirror separations and delay lengths (e.g., 4 bounce and 12 bounce delay lengths) can result in very long pulse stretching and minimal efficiency loss.

[0044]

[0062] According to some embodiments, the second optical pulse stretcher 401b may include three stages of confocal optical pulse stretchers. However, embodiments of the present disclosure are not limited to these examples and the second optical pulse stretcher 401b may include other numbers of stages of confocal optical pulse stretchers. In some examples, the first stage of the second optical pulse stretcher 401b is described as having two mirrors. However, embodiments of the present disclosure are not limited to these examples and the first stage of the second optical pulse stretcher 401b may include other numbers (e.g., two or more) and / or configurations of mirrors. In some examples, the multiple mirrors used in the first stage of the second optical pulse stretcher 401b are configured to generate four reflections of the laser beam between them.

[0045]

[0063] In some examples, the second stage of the second optical pulse stretcher 401b is described as having four mirrors. However, embodiments of the present disclosure are not limited to these examples and the second stage of the second optical pulse stretcher 401b may include other numbers (e.g., four or more) and / or configurations of mirrors. In some examples, the mirrors used in the second stage of the second optical pulse stretcher 401b are configured to generate 12 reflections of the laser beam between them.

[0046]

[0064] In some examples, the third stage of the second optical pulse stretcher 401b is described as having four mirrors. However, embodiments of the present disclosure are not limited to these examples and the third stage of the second optical pulse stretcher 401b may include other numbers (e.g., four or more) and / or configurations of mirrors. In some examples, the mirrors used in the third stage of the second optical pulse stretcher 401b are configured to generate 12 reflections of the laser beam between them.

[0047]

[0065] According to some embodiments, the stages of the first optical pulse stretcher 401a and the second optical pulse stretcher 401b are designed such that the optical delay increases from the first optical pulse stretcher 401a to the second optical pulse stretcher 401b. Similarly, the optical delay of each stage of the second optical pulse stretcher 401b increases from the first stage to the third stage. For example, the first optical pulse stretcher 401a (e.g., a quadrature optical pulse stretcher) may have an optical delay: a first stage of the second optical pulse stretcher 401b may have a first optical delay equal to or greater than the optical delay of the first optical pulse stretcher 401a; a second stage of the second optical pulse stretcher 401b may have a second optical delay equal to or greater than the first optical delay; and a third stage of the second optical pulse stretcher 401b may have a third optical delay equal to or greater than the second optical delay. According to some embodiments, the optical delay may be determined based on the distance the beam travels within the optical pulse stretcher.

[0048]

[0066] According to some embodiments, the first stage of the second optical pulse stretcher 401b may have an optical design including two mirrors (e.g., the two lower mirrors of mirrors 501 and 502 in FIG. 3) that generate four reflections of the laser beam between the mirrors. Although this example is described with two mirrors, the first stage of the second optical pulse stretcher 401b may include other numbers of mirrors (e.g., two or more mirrors). These mirrors may be positioned to generate four reflections of the laser beam between them. In some embodiments, the two mirrors of the first stage of the second optical pulse stretcher 401b may be separated from each other by a physical distance of about 2 m to 4 m. For example, the physical distance may be about 2.5 m to 3.5 m. These distances are provided by way of example only, and other distances may be used in other embodiments. In some examples, the first stage of the second optical pulse stretcher 401b may be capable of optical pulse stretching with an optical delay of about 60 ns to 80 ns, from the examples. For example, an optical delay of about 65 ns to 75 ns. For example, an optical delay of about 70 ns to 75 ns. Note that the example physical distance between the two mirrors and the example optical delay provided do not limit the embodiments of the present disclosure. The first stage of the second optical pulse stretcher 401b can be designed to achieve various other physical distances and / or various optical delays.

[0049]

[0067] According to some embodiments, the mirrors of the first stage of the second optical pulse stretcher 401b (e.g., the two lower mirrors of mirrors 501 and 502) may include rectangular concave mirrors. For example, two large rectangular concave mirrors can be used, although other shapes are used in other embodiments. According to some embodiments, the reflective surfaces of the mirrors may be spherically concave, such that the distance between the two mirrors of the first stage of the second optical pulse stretcher 401b (e.g., the surfaces of the two lower mirrors of mirrors 501 and 502) is equal (or nearly equal) to the respective radii of curvature of the two mirrors. For example, the mirrors may be designed and positioned based on a telecentric design. The concave mirrors may be designed with an orthogonal tip-tilt adjustment and also a Z-axis (e.g., beam propagation direction) adjustment according to some embodiments.

[0050]

[0068] According to some embodiments, the first stage of the second optical pulse stretcher 401b may include additional optical elements. In one example, the first stage of the second optical pulse stretcher 401b may include a beam splitter used to split the laser beam and generate copies of the laser beam. The beam splitter of the first stage of the second optical pulse stretcher 401b may have a reflectivity of about 45% to 65%, for example. In some examples, the beam splitter may have a reflectivity of about 50% to 60%. However, embodiments of the present disclosure are not limited to these examples and various other values ​​of reflectivity may be used. In some examples, the reflectivity of the beam splitter may depend on and / or be calculated based on the reflectivity of the mirrors used in the first stage of the second optical pulse stretcher 401b.

[0051]

[0069] According to some embodiments, the second stage of the second optical pulse stretcher 401b may have an optical design including four mirrors (e.g., four intermediate mirrors, mirrors 501 and 502 in FIG. 3) that generate 12 reflections of the laser beam between the mirrors. Although this example is described with four mirrors, the second stage of the second optical pulse stretcher 401b may include other numbers of mirrors (e.g., four or more mirrors). These mirrors may be positioned to generate 12 reflections of the laser beam between them. In some embodiments, the two pairs of mirrors of the second stage of the second optical pulse stretcher 401b may be separated from each other by a physical distance of about 2 m to 4 m. For example, the physical distance may be about 2.5 m to 3.5 m. These distances are provided by way of example only, and other distances may be used in other embodiments. In some examples, the second stage of the second optical pulse stretcher 401b may be capable of optical pulse stretching with an optical delay of about 170 ns to 210 ns, from the examples. For example, an optical delay of about 180 ns to 190 ns. For example, an optical delay of about 185 ns to 195 ns. Note that the example physical distances between the two pairs of mirrors and the example optical delays provided do not limit the embodiments of the present disclosure. The second stage of the second optical pulse stretcher 401b can be designed to achieve various other physical distances and / or various optical delays.

[0052]

[0070] According to some embodiments, the mirrors of the second stage of the second optical pulse stretcher 401b (e.g., the four middle mirrors of mirrors 501 and 502) may include rectangular concave mirrors. For example, four large rectangular concave mirrors can be used, although other shapes are used in other embodiments. According to some embodiments, the reflective surfaces of the mirrors may be spherically concave, such that the distance between the two pairs of mirrors of the second stage of the second optical pulse stretcher 401b (e.g., the surfaces of the two pairs of middle mirrors of mirrors 501 and 502) is equal (or approximately equal) to the radius of curvature of each of the four mirrors. For example, the mirrors may be designed and positioned based on a telecentric design. The concave mirrors can be designed with orthogonal tip-tilt adjustments according to some embodiments.

[0053]

[0071] According to some embodiments, the second stage of the second optical pulse stretcher 401b may include additional optical elements. In one example, the second stage of the second optical pulse stretcher 401b may include a beam splitter (intermediate beam splitter of beam splitter 503 in FIG. 3) used to split the laser beam and generate copies of the laser beam. The beam splitter of the second stage of the second optical pulse stretcher 401b may have a reflectivity of, for example, about 45%-65%. In some examples, the beam splitter may have a reflectivity of, for example, about 50%-60%. However, embodiments of the present disclosure are not limited to these examples and various other values ​​of reflectivity may be used. In some examples, the reflectivity of the beam splitter may depend on and / or be calculated based on the reflectivity of the mirrors used in the second stage of the second optical pulse stretcher 401b.

[0054]

[0072] Further details regarding light pulse stretchers can be found in U.S. Pat. No. 7,369,597, issued May 6, 2008, and entitled "Laser Output Light Pulse Stretcher," the entire contents of which are incorporated herein by reference.

[0055]

[0073] FIG. 4 shows a schematic diagram of a portion of the laser beam path in the second optical pulse stretcher 401b according to some embodiments of the present disclosure.

[0056]

[0074] As shown in FIG. 4, a laser beam 601 optically stretched using a stage of a first optical pulse stretcher 401a enters a second optical pulse stretcher 401b. Using a first beam splitter 503a, the laser beam 601 is split into a laser beam 603 and a laser beam 605. The laser beam 605 enters a second stage of the second optical pulse stretcher 401b. The laser beam 603 enters a first stage of the second optical pulse stretcher 401b, which includes two mirrors. As shown in FIG. 5A, after four reflections from two mirrors 501a, 502a of the first stage of the second optical pulse stretcher 401b, a part of the laser beam enters the second stage of the second optical pulse stretcher 401b by reflecting off a beam splitter 503a, and the remaining part of the beam continues to loop further within the optical pulse stretcher 400.

[0057]

[0075] Laser beam 605 (and / or the laser beam from the first stage of second optical pulse stretcher 401b) is split into laser beam 607 and laser beam 609. Laser beam 609 enters the third stage of second optical pulse stretcher 401b. Laser beam 607 enters the second stage of second optical pulse stretcher 401b, which includes four mirrors 501c, 501b, 502b, and 501c, as shown in FIG. 5B. After 12 reflections (indicated by numbers 1-12) from the four mirrors of the second stage of second optical pulse stretcher 401b, a portion of the laser beam enters the third stage of second optical pulse stretcher 401b by reflecting off beam splitter 503b.

[0058]

[0076] Laser beam 609 (and / or the laser beam from the second stage of the second optical pulse stretcher 401b) is split into laser beam 611 and laser beam 613. Laser beam 613 is reflected back to the first optical pulse stretcher 401a using mirrors 505a and 505b. Laser beam 611 enters the third stage of the second optical pulse stretcher 401b, which includes four mirrors. After 12 reflections from the four mirrors of the third stage of the second optical pulse stretcher 401b, a portion of the laser beam is reflected back towards the first optical pulse stretcher 401a using beam splitter 503c and folding mirrors 505a and 505b (FIG. 4).

[0059]

[0077] FIG. 6 shows a schematic diagram of a portion of the laser beam path in the second optical pulse stretcher 401b and some of the mirrors used in the second optical pulse stretcher 401b according to some embodiments of the present disclosure.

[0060]

[0078] In FIG. 6, five mirrors on one side of the second optical pulse stretcher 401b are shown. It will be understood that according to some embodiments, there are also substantially symmetrical arrangements in the second optical pulse stretcher 401b. In this example, mirror 502a of the first stage of the second optical pulse stretcher 401b is shown. A mirror (e.g., mirror 501a) is on the opposite side of the first stage of the second optical pulse stretcher 401b, which is not shown in this figure. In this example, a pair of mirrors 502b and 502c of the second stage of the second optical pulse stretcher 401b is shown. Another pair of mirrors (e.g., pair of mirrors 501b and 501c) is on the opposite side of the second stage of the second optical pulse stretcher 401b, which is not shown in this figure. Similarly, in this example, a pair of mirrors 502d and 502e of the third stage of the second optical pulse stretcher 401b is shown. Another pair of mirrors (eg, pair of mirrors 501d and 501e) is on the opposite side of the third stage of the second optical pulse stretcher 401b, which is not shown in this figure.

[0061]

[0079] The following description relates to an arrangement in which the optical components in the OPuS, such as mirrors, are arranged in two banks that are approximately symmetrical about a central axis, for the purpose of having a concrete example to facilitate the description. However, it will be understood that the principles disclosed herein are applicable to other arrangements, and the concrete examples described herein are not limiting. As appealed to herein, "approximately symmetric" and "substantially symmetric" mean sufficient symmetry that the OPuS can function for its intended purpose and that the image integration module, as described below, can "see" all the mirrors simultaneously. According to an aspect of an embodiment, in such an arrangement, the image integration module is arranged to collect object rays from both the left optics and the right optics, which in this example are concave mirrors. Thus, in this arrangement, there are several left and right mirror pairs. A camera system, including a camera and a lens system, is positioned outside the sealed OPuS enclosure. The camera is arranged to collect light rays through a sealed window that transmits light in the visible part of the spectrum, i.e., within the wavelength range of about 380 to about 700 nm. The light beam creates an image with half of the image coming from the left concave mirror of the mirror pair and the other half coming from the right concave mirror of the mirror pair.

[0062]

[0080] With this as background, a conventional method of aligning optical elements in an OPuS will be described with reference to FIG. 7. As seen in FIG. 7, OPuS 700 includes an enclosure 710. Within the enclosure 710, optical elements 720, 730, 740, and 750 are positioned. These optical elements may be, for example, mirrors. These optical elements must be aligned so that an incoming beam strikes the optical elements at the correct location. To perform this alignment procedure, the enclosure 710 is opened and an alignment card 760 is placed adjacent to the location of the optical surface of one of the optical elements (in the figure, optical element 750). The optical element is then aligned so that the beam strikes the correct location on the alignment card 760. As described above, this method includes several drawbacks, such as the need to open the enclosure 710 to break the purge, and the need for an operator to insert their hands into the enclosure 710 in an open beam situation (which may expose the operator's hands to UV light). It also increases the risk of optical contamination and a resulting reduction in the useful life of the optical system.

[0063]

[0081] As shown in FIG. 8A, according to aspects of an embodiment, an OPuS 800 that enables improved alignment methods includes an enclosure 810. Located within the enclosure 810 are optical features 820, 830, 840, and 850. Located in a central portion of the enclosure 810 is an image integration module 860. As described in more detail below, this image integration module 860 collects light from the optical features and presents the light to a camera 890 through a sealed window 870 and a lens 880. In effect, the camera 890 "sees" all the optical features within the enclosure 810 simultaneously without the need to open the enclosure 810. This allows for continuous observation of the alignment state of the OPuS 800 while avoiding the shortcomings of prior art methods. In some embodiments, the image integration module 860 is located as close to the camera system as possible to maximize the available field of view. Elements 835 and 855 are adjusters, as described in more detail below. Figure 8B shows the arrangement of the image combining module 860 in relation to the arrangement shown in Figure 5B, where again the numbers 1 through 12 indicate the positions of the 12 reflections from the four mirrors.

[0064]

[0082] 9A illustrates a possible implementation of an image integration module 860, according to aspects of an embodiment. As shown, the image integration module 860 may be implemented as a pair of mirror prisms 910, 920. The prism 910 is positioned to receive light from a region of interest 825, which includes at least one optical feature 820, and redirect the light out through a sealed window 870, as shown. Similarly, the prism 920 is positioned to receive light from a region of interest 835, and redirect the light out through a sealed window 870, as shown. Thus, a camera system including a camera and one or more lenses positioned on opposite sides of the sealed window 870 simultaneously receives image-forming light from both the left region of interest 825 and the right region of interest 835. That is, the image integration module 860 collects object rays from both the left optical feature and the right optical feature. A camera and lens system positioned outside the sealed OPuS enclosure 820 camera collects the object beam through a visible transmissive sealed window and produces an image where half of the image is from the left optical feature and the other half is from the right optical feature.

[0065]

[0083] FIG. 9B illustrates how image integration module 860 receives light from both a left region of interest 825 that includes at least one optical feature and a right region of interest 835 that also includes at least one optical feature and redirects the light to position A from which virtual object 825a, which is an image of left region of interest 825, and virtual object 835a, which is an image of right region of interest 835, appear to be juxtaposed, i.e., positioned side by side, so that they can be viewed simultaneously by a single camera system positioned at position A.

[0066]

[0084] According to aspects of an embodiment, the image merging module 860 may also be implemented using a pair of mirrors. As an example, a mirror 950 is shown in FIG. 10 with the other mirror arranged substantially symmetrically with respect to an axis 970. The condition of maximum field of view in such an arrangement is established geometrically, as also shown in FIG. 10. In the figure, h is the height of the field of interest 960, d is the vertical distance between the center of the field and the center of the mirror 950, and s is the horizontal distance between the field and the mirror 950. The upper part of the figure is the position of the virtual image as seen from below the mirror (in the figure). The angle θ for maximum field of view between a line 980 parallel to the field of interest 960 and passing through the center of the mirror 950 is related to:

number

number

[0067]

[0085] As mentioned above, the image combining module 860 may be implemented in any one of several ways. According to aspects of some embodiments, the image combining module 860 may be implemented as a pair of prisms 910, 920 as shown in FIG. 9A, or as a single prism 1000 with two mirrored surfaces 1010 and 1020 as shown in FIG. 11A, or as two flat chamfered mirrors 1030 and 1040 as shown in FIG. 11B. However, the image combining module 860 is implemented, in some embodiments, the gaps between the optical elements or mirrored surfaces are minimized so as not to waste the portion of the field of view that is lost due to the gaps as shown in FIG. 11C. In FIG. 11C, arrow A indicates the field of view from one of the optical features (e.g., the mirror), arrow B indicates the field of view from the other pair of optical features, and arrow C indicates the field of view that is lost due to the gap between the prisms 910 and 920.

[0068]

[0086] FIG. 9A shows an arrangement in which light passing through the sealed window 870 travels directly to the lens system 880 in a straight line. In some embodiments, it may be advantageous to insert additional optical elements in the path from the sealed window 870 to the lens system 880. For example, FIG. 12A shows an arrangement in which a folding mirror 1100 is placed in this path to fold the light path and create the possibility of providing a more compact arrangement. In the arrangement of FIG. 12A, the mirror 1100 is positioned within the enclosure to obtain a larger field of view. This arrangement also provides the ability to adjust the image orientation and improve the matching of the size and shape of the field to the image sensor in the camera. FIG. 12B shows an arrangement in which the prisms 910a, 920a are partially rotated to fold the light path. 12B illustrates how image merging module 860a receives light from both the left region of interest 825 and the right region of interest 835 and redirects that light to position B from which virtual object 825b, which is an image of left region of interest 825, and virtual object 835b, which is an image of right region of interest 835, appear to be juxtaposed, or positioned side-by-side, so that they can be viewed simultaneously by a single camera system located at position B. As shown, this arrangement also provides the ability to adjust the image orientation and improve matching of the size and shape of the field to the image sensor in the camera.

[0069]

[0087] In some embodiments, it may also be advantageous to improve visibility of the region of interest by providing alignment features and by using visible light (to the camera) due to fluorescence generated by absorption of ultraviolet light. Using the example of a dichroic mirror as the optical element to be aligned, the mirror is generally supported by a mirror support plate 1300 that includes a support 1310 and at least one alignment feature 1320. According to some embodiments, as shown in FIG. 13, the dichroic mirror assembly 1330 includes a substrate 1340 that transmits visible light as shown in FIG. 13B, and a UV-reflective coating 1360 (FIG. 13D). The dichroic mirror assembly 1330 is layered on top of the mirror support plate 1300 to produce a sandwich-like structure shown in FIGS. 13C and 13D. UV radiation impinging on the dichroic mirror assembly 1330 produces a visible beam fluorescence footprint 1350 in a manner described more fully below. The fluorescence produced by the ultraviolet light and the rear alignment features can be observed, for example, by a camera operating in the visible spectral region. By comparing the location of the fluorescence and the alignment features through a mirror or substrate, the system can be easily aligned, as described below. Although visible light is used in this example, it will be understood that radiation outside the visible part of the spectrum may also be used.

[0070]

[0088] According to aspects of various embodiments, the illumination beam footprint may be generated upon UV exposure in any one of several different ways. For example, as shown in FIG. 14A, a UV reflective coating 1360 may be selected to exhibit intrinsic fluorescent properties upon UV exposure. This is illustrated in FIGS. 14A-14D with a thick arrow indicating the incident UV radiation and a wavy arrow indicating light caused by fluorescence. Alternatively, as shown in FIG. 14B, the backside of the substrate 1340 may be provided with a fluorescent coating 1370, where light is generated by UV leakage through the reflective coating 1360. The term "backside" when referring to the substrate 1340 refers to the substrate surface facing away from the incoming UV radiation. Alternatively, as shown in FIG. 14C, the frontside of the support 1310 may be provided with a fluorescent coating 1380, where light is generated by UV leakage through the reflective coating 1360. The term "frontside" when referring to the support 1310 refers to the support surface facing the incoming UV radiation. Alternatively, as shown in FIG. 14D, the support 1310 may be made from a fluorescent material, where light is produced by UV leakage through a reflective coating 1360 .

[0071]

[0089] FIG. 15A is a plan view of a dichroic mirror assembly 1330 superimposed on a mirror support plate 1300 having alignment features 1320. The mirror support plate 1300 having alignment features 1320 is shown in perspective because it is behind the dichroic mirror assembly 1330. UV radiation impinging on the dichroic mirror assembly 1330 produces a visible beam fluorescent footprint 1350 as described. That is, a beam of UV radiation impinges on the dichroic mirror assembly 1330 at one or more specific locations, for example as shown in FIG. 5B. The specific areas impinged by the beam fluoresce as shown by the fluorescent footprint 1350. The remainder of the surface of the dichroic mirror assembly 1330 not impinged by the beam do not fluoresce. FIG. 15A shows a non-aligned position where the fluorescent footprint 1350 is not fully aligned with the alignment feature 1320. 15B shows the alignment position where the fluorescent footprint 1350 is fully aligned with the alignment feature 1320. This is achieved by alignment such that the UV beam lands on the dichroic mirror assembly 1330 at the correct location (two in this example) that will illuminate and reveal the relative positioning of the UV footprint and alignment features through fluorescence. To correct the alignment, the orientation of one or more mirrors is adjusted so that the beam lands in the correct position on all mirrors. The image of the beam landing juxtaposed with the alignment feature is captured by a camera and thus converted into a digital image that can be viewed by the operator while performing the alignment operation.

[0072]

[0090] According to some embodiments, alignment of the pulse stretcher requires that at least some of the mirrors are adjustable, e.g., in the case of a four mirror arrangement, at least two of the four imaging relay mirrors are adjustable. Two adjustable mirrors each have tip / tilt adjustment resulting in a total of four degrees of freedom. The two adjustable mirrors may be located at opposite ends of the OPuS due to the confocal design of the system. The adjustable mirrors may also be designed with Z-axis (e.g., beam propagation direction) adjustment according to some embodiments.

[0073]

[0091] Typically, adjustments to these components to perform alignment are made using through-the-wall adjusters ("TWAs") such as adjusters 855 and 835 (FIG. 8A). These involve the use of a manually operated hex driver to tip, tilt, or translate the optics or module. The TWA may provide a sealed mechanical feedthrough for the specific adjustment, and may be accessed, for example, through a cover via a sealed mechanical feedthrough. Adjustments may also be made with an electrically actuated TWA instead of a manually actuated TWA. A motor is mechanically coupled to the TWA. For example, the motor may have a shaft with a hex adapter attached such that as the motor rotates the shaft, the hex driver also rotates, thereby causing the end of the TWA to translate along its axis according to the direction of rotation of the shaft. The use of an electronically actuated TWA allows for automation of the alignment process, where digital images from camera 890 are conveyed to control system 135 (FIG. 1), which then analyzes the images and actuates the TWA to perform the alignment.

[0074]

[0092] It is to be understood that alignment may involve adjusting only one optical feature, and that having the beam impinge on the correct portion of a first optical feature may require adjusting a second optical feature.

[0075]

[0093] FIG. 16 is a flow chart showing a process of aligning optical features positioned in a sealed enclosure according to aspects of an embodiment. In step S10, the optical features in the enclosure are exposed to a UV radiation beam. The UV radiation beam makes the footprint of the UV radiation beam visible to the eye. In step S20, the light generated by the UV radiation beam fluorescence is combined into a single image from the optical features. The single image is brought to a camera outside the closed chamber in step S30. In step S40, the features are aligned based on the image made from the light combined from the features by a technician while viewing the image captured by the camera or by a control system as described above. In essence, in an example where each feature includes an alignment feature, the alignment is determined for each optical feature based on the image of the beam footprint and the positional relationship within the alignment feature.

[0076]

[0094] The present invention has been described above using functional components that illustrate the implementation of certain functions and their relationships. The boundaries of these functional components have been arbitrarily defined herein for the convenience of description. Other boundaries may be defined as long as the certain functions and their relationships are appropriately performed.

[0077]

[0095] The above description of specific embodiments fully reveals the general nature of the present invention so that others, by applying knowledge within the skill of the art, may easily modify and / or adapt such specific embodiments for various applications without undue experimentation and without departing from the general concept of the present invention. Such adaptations and modifications are therefore intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the terms or terminology used herein are for purposes of description and not of limitation, as the terms or terminology used herein would be interpreted by those skilled in the art in light of the teachings and guidance.

[0078]

[0096] Other aspects of the invention are described in the following numbered clauses. 1. A sealed enclosure including a window that transmits visible light; a first optical feature positioned at a first location within the enclosure; a second optical feature positioned at a second location within the enclosure; and an image integrating module disposed to receive a first optical feature light from the first optical feature and a second optical feature light from the second optical feature, and adapted to redirect the first optical feature light and the second optical feature light through a window to form an image from the first optical feature light juxtaposed with an image from the second optical feature light; 4. An optical component comprising: 2. The optical component of claim 1, wherein the optical component is an optical pulse stretcher. 3. The optical component of clause 1, wherein the first optical feature includes a first mirror and the second optical feature includes a second mirror. 4. The optical component of clause 3, wherein the first mirror comprises a first concave dichroic mirror and the second mirror comprises a second concave dichroic mirror. 5. The optical component described in clause 1, wherein the first optical feature and the second optical feature are positioned substantially symmetrically with respect to the image integrating module. 6. The optical component described in clause 1, wherein the image integration module includes a first reflective surface arranged to redirect light from a first optical feature and a second reflective surface arranged to redirect light from a second optical surface. 7. The optical component of clause 6, wherein the first reflective surface comprises a first prism reflective surface of a first prism and the second reflective surface comprises a second prism reflective surface of a second prism. 8. The optical component described in clause 1, wherein the image integration module includes a prism having a first reflective surface oriented toward the first optical feature and a second reflective surface oriented toward the second optical feature. 9. The optical component of claim 1, wherein the image integration module includes two flat chamfered mirrors. 10. A third optical feature positioned at a third location within the enclosure; and a fourth optical feature positioned at a fourth location within the enclosure; and Further comprising: The optical component described in clause 1, wherein the image integration module is positioned to receive third optical feature light from the third optical feature and fourth optical feature light from the fourth optical feature, and is adapted to combine and redirect the third optical feature light and the fourth optical feature light through the window to form an image from the third optical feature light juxtaposed with the image from the fourth optical feature light. 11. The optical component described in clause 1, further comprising a camera system positioned to receive the first optical feature light and the second optical feature light through the window. 12. The camera system a lens system positioned to receive the first optical feature light and the second optical feature light through the window; a camera positioned to receive the first optical feature light and the second optical feature light from the lens system; 12. The optical component of claim 11, comprising: 13. The optical component described in clause 11, further comprising a folding mirror optically positioned between the image integration module and the window for redirecting the optical paths of the first optical feature light and the second optical feature light. 14. The optical component described in clause 1, wherein at least one of the first optical feature and the second optical feature is adjustable, and further comprising an actuator mechanically coupled to at least one of the first optical feature and the second optical feature for adjusting an orientation of at least one of the first optical feature and the second optical feature. 15. The optical component of clause 1, wherein the first optical feature includes a first fluorescent material and a first alignment feature, and the second optical feature includes a second fluorescent material and a second alignment feature. 16. The first optical feature includes a first mirror including a first substrate that transmits visible light, a first reflective coating that reflects UV radiation, and a first mirror support; The optical component of clause 1, wherein the second optical feature includes a second mirror including a second substrate that transmits visible light, a second reflective coating that reflects UV radiation, and a second mirror support. 17. An optical component as described in clause 16, wherein the first mirror support includes a first alignment feature on a front surface of the first mirror support and the second mirror support includes a second alignment feature on a front surface of the second mirror support. 18. The optical component of clause 17, wherein the first alignment feature coincides with a position of an aligned beam footprint on the first mirror and the second alignment feature coincides with a position of an aligned beam footprint on the second mirror. 19. The optical component of clause 18, wherein the first optical feature further comprises a first fluorescent material and the second optical feature further comprises a second fluorescent material. 20. The optical component of clause 19, wherein the first optical feature includes a first reflective coating comprising a first fluorescent material and the second optical feature includes a second reflective coating comprising a second fluorescent material. 21. An optical component as described in clause 19, wherein a first fluorescent material is provided on a rear surface of a first substrate and a second fluorescent material is provided on a rear surface of a second substrate. 22. An optical component as described in clause 19, wherein a first fluorescent material is provided on a front surface of the first mirror support and a second fluorescent material is provided on a front surface of the second mirror support. 23. An optical component as described in clause 19, wherein the first mirror support comprises a first fluorescent material and the second mirror support comprises a second fluorescent material. 24. A sealed enclosure including a window that transmits visible light; a first optical feature positioned within a first field of view within the enclosure; a second optical feature positioned within the enclosure and within the first field of view; an image combination module disposed to receive the first field of view light from the first field of view and adapted to combine and redirect the first field of view light through a window; Including, The image integration module

number

Claims

1. a sealed enclosure including a window that transmits visible light; a first optical feature positioned at a first location within the enclosure; a second optical feature positioned at a second location within the enclosure; and an image combining module disposed to receive a first optical feature light from the first optical feature and a second optical feature light from the second optical feature, and adapted to redirect the first optical feature light and the second optical feature light through the window to form an image from the first optical feature light juxtaposed with an image from the second optical feature light; 4. An optical component comprising:

2. The optical component of claim 1 , wherein the optical component is an optical pulse stretcher.

3. The optical component of claim 1 , wherein the first optical feature comprises a first mirror and the second optical feature comprises a second mirror.

4. The optical component of claim 3 , wherein the first mirror comprises a first concave dichroic mirror and the second mirror comprises a second concave dichroic mirror.

5. The optical component of claim 1 , wherein the first optical feature and the second optical feature are positioned substantially symmetrically with respect to the image combining module.

6. 2. The optical component of claim 1, wherein the image integration module includes a first reflective surface positioned to redirect light from the first optical feature and a second reflective surface positioned to redirect light from the second optical surface.

7. The optical component of claim 6 , wherein the first reflective surface comprises a first prism reflective surface of a first prism and the second reflective surface comprises a second prism reflective surface of a second prism.

8. The optical component of claim 1 , wherein the image combining module includes a prism having a first reflective surface oriented toward the first optical feature and a second reflective surface oriented toward the second optical feature.

9. The optical component of claim 1 , wherein the image combining module includes two flat chamfered mirrors.

10. a third optical feature positioned at a third location within the enclosure; and a fourth optical feature positioned at a fourth location within the enclosure; and Further comprising:

2. The optical component of claim 1, wherein the image combination module is positioned to receive a third optical feature light from the third optical feature and a fourth optical feature light from the fourth optical feature, and is adapted to combine and redirect the third optical feature light and the fourth optical feature light through the window to form an image from the third optical feature light juxtaposed with an image from the fourth optical feature light.

11. The optical component of claim 1 , further comprising a camera system positioned to receive the first optical feature light and the second optical feature light through the window.

12. The camera system comprises: a lens system positioned to receive the first optical feature light and the second optical feature light through the window; a camera positioned to receive the first optical feature light and the second optical feature light from the lens system; The optical component of claim 11 , comprising:

13. The optical component of claim 11 , further comprising a folding mirror optically positioned between the image integration module and the window for redirecting optical paths of the first optical feature light and the second optical feature light.

14. 2. The optical component of claim 1, wherein at least one of the first optical features and the second optical features is adjustable, and further comprising an actuator mechanically coupled to the at least one of the first optical features and the second optical features for adjusting an orientation of the at least one of the first optical features and the second optical features.

15. The optical component of claim 1 , wherein the first optical feature comprises a first fluorescent material and a first alignment feature, and the second optical feature comprises a second fluorescent material and a second alignment feature.

16. the first optical feature includes a first mirror including a first substrate that transmits visible light, a first reflective coating that reflects UV radiation, and a first mirror support; 10. The optical component of claim 1, wherein the second optical feature comprises a second mirror including a second substrate that transmits visible light, a second reflective coating that reflects UV radiation, and a second mirror support.

17. 17. The optical component of claim 16, wherein the first mirror support includes a first alignment feature on a front surface of the first mirror support and the second mirror support includes a second alignment feature on a front surface of the second mirror support.

18. 20. The optical component of claim 17, wherein the first alignment feature coincides with a position of an aligned beam footprint on the first mirror and the second alignment feature coincides with a position of an aligned beam footprint on the second mirror.

19. The optical component of claim 18 , wherein the first optical feature further comprises a first fluorescent material and the second optical feature further comprises a second fluorescent material.

20. 20. The optical component of claim 19, wherein the first optical feature includes a first reflective coating that includes the first fluorescent material, and the second optical feature includes a second reflective coating that includes the second fluorescent material.

21. 20. The optical component of claim 19, wherein the first fluorescent material is provided on a rear surface of the first substrate and the second fluorescent material is provided on a rear surface of the second substrate.

22. 20. The optical component of claim 19, wherein the first fluorescent material is provided on a front surface of the first mirror support and the second fluorescent material is provided on a front surface of the second mirror support.

23. 20. The optical component of claim 19, wherein the first mirror support comprises the first fluorescent material and the second mirror support comprises the second fluorescent material.

24. a sealed enclosure including a window that transmits visible light; a first optical feature positioned within a first field of view within the enclosure; and a second optical feature positioned within the enclosure and within the first field of view; an image combination module disposed to receive first field of view light from the first field of view and adapted to combine and redirect the first field of view light through the window; Including, The image integration module determines the relationship [0010] the plane mirror is tilted with respect to a line passing through a center of the plane mirror and substantially parallel to the first field of view by an angle θ given by an optical component, wherein h is a height of the first field of view, d is a vertical distance between the center of the first field of view and the center of the planar mirror surface, and s is a horizontal distance between the first field of view and the center of the planar mirror surface.

25. 1. A method for aligning a plurality of optical features disposed within a sealed enclosure having a window, the method comprising: combining light from each of the optical features to generate a combined optical signal; directing the combined optical signal out of the enclosure through the window; aligning at least some of the plurality of optical features based at least in part on the combined optical signal; A method comprising:

26. 26. The method of claim 25, further comprising imaging the combined optical signal using a camera system positioned outside the sealed enclosure and configured to receive the combined optical signal after directing the combined optical signal outside the enclosure through the window.

27. each of the plurality of optical features includes an alignment feature and a fluorescent material arranged to produce a visible footprint of a UV beam impinging on the optical feature, and prior to combining light from each of the optical features to produce a combined optical signal, exposing each of the optical features to a beam of UV radiation; generating an illumination footprint of the UV radiation beam on each of the optical features; Further comprising:

26. The method of claim 25, wherein aligning at least some of the plurality of optical features based at least in part on the combined optical signal comprises aligning at least some of the plurality of optical features based at least in part on a positional relationship of the illumination footprint and the alignment feature for each optical feature.

28. The method of claim 25 , wherein aligning comprises adjusting one or more of the plurality of optical features.

29. 30. The method of claim 28, wherein adjusting one or more of the plurality of optical features comprises manually manipulating one or more actuators mechanically coupled to the one or more of the plurality of optical features, respectively.

30. 30. The method of claim 28, wherein adjusting one or more of the plurality of optical features comprises providing signals to actuate one or more motor-driven actuators respectively mechanically coupled to the one or more of the plurality of optical features.

31. 30. The method of claim 28, wherein adjusting one or more of the plurality of optical features comprises adjusting an orientation of one or more of the plurality of optical features.

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