JP5120081B2 - Spectrum light source device - Google Patents

Description

  The present invention relates to an optical spatial modulation device and a spectrum light source device. The present invention particularly relates to an optical spatial modulation device and a spectrum light source device that modulate light having a continuous wavelength distribution into an arbitrary wavelength distribution.

A spectrum light source device that modulates light having a continuous wavelength distribution into an arbitrary wavelength distribution is known (see, for example, Patent Document 1). This spectrum light source has a light source that emits light having a continuous wavelength distribution and a tunable filter as a modulation element having an arbitrary spectral transmittance characteristic. In this spectrum light source device, input light from the light source is converted into light having an arbitrary wavelength distribution by passing through a tunable filter and output. More specifically, in this spectrum light source device, a transmissive liquid crystal element array and polarizing plates are installed at the front and back of the transmissive liquid crystal element array at the position of the spectrum image formed by the tunable filter spectroscope, and the individual transmissive liquid crystal elements are independently scaled. After tuned control to modulate the transmitted light quantity of the spectrum image, the output light is output by adding arbitrary spectral characteristic modulation to the input light by wavelength multiplexing again by the built-in spectroscope.
JP-A-11-101944

  A xenon lamp is used as a light source of the spectrum light source device. A xenon lamp has, for example, a plurality of light intensities that protrude locally in the near infrared region. If you want to output with this protruding wavelength band kept low, the attenuation capability by combining the liquid crystal element and the polarizing plate will use a considerable part of the capability to suppress the protruding portion of input light, so further seeking The number of attenuation gradations of the liquid crystal element for fine adjustment to obtain the spectrum characteristics is insufficient. Also, if the light intensity of the input light is too strong, it is difficult to obtain the required attenuation.

  In order to solve the above-described problem, in the first embodiment of the present invention, the polarization state of input light having a plurality of optical elements arranged along a surface to which input light is input and passing through the plurality of optical elements. When at least one of the input light and the output light passes, and the modulation element unit that outputs at least one of the intensity and the intensity independently modulated for each optical element based on a command from the outside. An optical spatial modulation device is provided that includes an intensity modulation filter that modulates at least one of input light and output light to a predetermined intensity as a function of the direction of the arrangement of the plurality of optical elements.

  In the second embodiment of the present invention, a light source that generates input light, a polarization optical system that converts the input light into a specific polarization state, and a spectrum that spreads the light converted into the specific polarization state in one direction. Input light having a wavelength-dispersive spectroscopic optical system that divides into an image, a plurality of optical elements arranged along the spread direction of the spectrum image, and a reflecting surface, and reciprocating within the plurality of optical elements after being reflected by the reflecting surface The polarization state of the spectrum image is modulated independently for each wavelength region reciprocating in the optical element based on a command from the outside, and the modulation element unit that reflects the output light, and the input light and the output light pass therethrough And an intensity modulation filter that modulates the input light and the output light to a predetermined intensity for each wavelength region, and the output light that has passed through the intensity modulation filter is re-input to the wavelength dispersion type spectroscopic optical system. The length is combined, the output light wavelength multiplexing is a spectrum light source device output polarized light having one polarization direction is re-input to the polarization optical system is separated from the other polarization is provided.

  In the third aspect of the present invention, the light source that generates the input light, the input polarization optical system that converts the input light into a specific polarization state, and the light converted into the specific polarization state are spread in one direction. It has a wavelength dispersion type spectroscopic optical system that divides into a spectrum image and a plurality of optical elements arranged along the spread direction of the spectrum image, and the polarization state when the spectrum image of the input light passes through the plurality of optical elements. A modulation element that outputs output light that is modulated independently for each wavelength region that passes through the optical element based on a command from the outside, and at least one of the input light and the output light passes through the input light. And an intensity modulation filter that modulates at least one of the output lights to a predetermined intensity for each wavelength region, a wavelength multiplexing optical system that wavelength-multiplexes the output light of the spectrum image, and wavelength-multiplexed Of Power light spectrum light source device and an output polarization optical system that separates and outputs the polarized light having one polarization direction from the other polarization it is provided.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 is a schematic diagram of a spectrum light source device 10 which is an example of an embodiment. The spectrum light source device 10 modulates the input light 90 from the light source 20 having a continuous wavelength distribution into an output light 92 having an arbitrary wavelength distribution and outputs the modulated light to the optical fiber 86. The spectrum light source device 10 shown in FIG. 1 includes a light source 20, a polarization optical system 30, a slit 38, a wavelength dispersion type spectroscopic optical system 40, an optical spatial modulation device 50, a modulation element driver 66, and an optical system 84. Is provided.

  The light source 20 generates input light 90 having a continuous wavelength distribution. An example of the light source 20 is a xenon lamp. The spectrum of the xenon lamp has a light intensity protrusion in a specific wavelength band, but can be used as the light source 20 if the intensity distribution with respect to the wavelength is known.

  The polarization optical system 30 includes an optical system 32, a polarization beam splitter 34, and an optical system 36, and converts the input light 90 into a specific polarization state. Here, the optical system 32 collimates the input light 90 from the polarization optical system 30, and the polarization beam splitter 34 linearly passes linearly polarized light whose electric field direction is parallel to the drawing, and linearly polarized light orthogonal to the linearly polarized light. The traveling direction is bent and discarded as discarded light 94. Further, the optical system 36 focuses the linearly polarized light that has passed straight through the polarization beam splitter 34. In FIG. 1, the traveling direction 80 is indicated by an arrow, and the polarization direction 82 is shown superimposed on the arrow. The reciprocating arrow in FIG. 1 indicates that the polarization direction 82 is parallel to the paper surface, and the circle indicates that the polarization direction 82 is perpendicular to the paper surface.

  The wavelength dispersion type spectroscopic optical system 40 includes a collimator 42, a grating 44, and a camera 46, and splits the linearly polarized light into a spectrum image having a spatial extension in one direction. Further, a slit 38 is disposed between the polarization optical system 30 and the wavelength dispersion type spectroscopic optical system 40. In this case, the slit 38 is preferably located at the rear focal point of the optical system 36 and the front focal point of the collimator 42. The optical system 36 focuses linearly polarized light on the slit 38. The light that has passed through the slit 38 is diffused and input to the collimator 42. The collimator 42 collimates the input diffused light and inputs it to the grating 44.

  The grating 44 splits the input light into a spectrum image having a spatial spread according to the wavelength. In the example shown in FIG. 1, the grating 44 splits the input light into spectrum light that spreads in the direction perpendicular to the paper surface from the longer wavelength to the lower wavelength. Here, since the parallel light beam collimated by the collimator 42 is input to the grating 44, the locality of the polarization state modulation in the process of passing through the grating 44 can be suppressed. Further, the spectrum image is focused on the spatial light modulator 50 by the camera 46.

  The spatial light modulator 50 includes an intensity modulation filter 70 that modulates the intensity, and a modulation element unit 60 that modulates and outputs the polarization state of the input light. The intensity modulation filter 70 and the modulation element unit 60 will be described in detail later.

  The light output from the modulation element 60 is re-input to the polarization beam splitter 34 through the intensity modulation filter 70, the camera 46, the grating 44, the collimator 42, the slit 38 and the optical system 36 in the opposite direction. . Here, the output light that has re-passed the intensity modulation filter 70 is re-input to the camera 46 and collimated, and then re-input to the grating 44, wavelength-multiplexed, re-input to the collimator 42, and focused on the slit 38. And collimated by the optical system 36.

  When the output light collimated by the optical system 36 is re-input to the polarization beam splitter 34, the polarization beam splitter 34 separates the polarized light having one polarization direction from the other polarized light and outputs it. . That is, the polarization beam splitter 34 linearly transmits and discards the wavelength component whose polarization direction is not modulated by the intensity modulation filter 70 in the re-input output light. On the other hand, the polarization beam splitter 34 bends the traveling direction of the wavelength component whose polarization direction is modulated by the intensity modulation filter 70 of the re-input output light (for example, 90 ° in FIG. 1), and applies it to the optical system 84. Let them enter. The optical system 84 focuses the input light as the output light 92 on the optical fiber 86 and outputs it. FIG. 1 shows output light modulated by the modulation element unit 60.

  2 is a front view of the spatial light modulator 50 as viewed from the direction in which the input light is input. FIG. 3 is a plan view of the spatial light modulator 50. FIG. 4 is a side view of the spatial light modulator 50. . The spatial light modulator 50 includes a protective glass 76, an intensity modulation filter 70, and a modulation element unit 60.

  The modulation element unit 60 is a reflective liquid crystal, and includes a plurality of liquid crystal elements 62, a cover glass 68 that seals the liquid crystal elements 62, and a flat mirror 64 that is in close contact with the back surface of the liquid crystal element 62. On the cover glass 68, transparent electrodes for individually applying an electric field to the liquid crystal elements 62 are formed. The liquid crystal element 62 is an example of an optical element, and the flat mirror 64 is an example of a reflecting surface.

  Here, as shown in FIG. 2, the plurality of liquid crystal elements 62 are arranged one-dimensionally, and the arrangement direction is along the spread direction of the spectrum image (for example, the horizontal direction in FIG. 2). The individual liquid crystal elements 62 are independently controlled by the modulation element driver 66 of FIG. 1, and different retardations are added to the light that reciprocates in the individual liquid crystal elements 62 for each liquid crystal element 62. Therefore, the spectrum image emerging from the modulation element unit 60 becomes elliptically polarized light that differs for each liquid crystal element 62, that is, for each wavelength region.

  As a result, the modulation element unit 60 reflects the polarization state of the spectrum image of the input light reflected by the plane mirror 64 and reciprocating within the plurality of liquid crystal elements 62 for each wavelength region based on a command from the modulation element driver 66. Output light is modulated independently of each other. In this case, since the modulation element 60 is a reflection type, a large aperture ratio can be obtained.

  An intensity modulation filter 70 is bonded on the input / output surface of the cover glass 68. A protective glass 76 is bonded on the intensity modulation filter 70. An antireflection coating is applied to the outer surface of the protective glass 76. However, an antireflection coating may be applied directly on the intensity modulation filter 70 without the protective glass 76. In order to suppress stray light from the surface reflected light from the outer surface of the protective glass 76 or from the outer surface of the intensity modulation filter 70 in the absence of the protective glass 76, the protective glass 76 is made into a wedge type as shown in FIG. Good. Thereby, it is possible to prevent the path of the outer surface reflected light of the protective glass 76 from being separated from the signal light and mixed into the output light. In addition, about a joining surface of the intensity | strength modulation filter 70 and the protective glass 76, a reflectance can be suppressed to the minimum by taking refractive index matching, and stray light can be suppressed. Further, the spectrum image of the light emitted from the light source 20 and dispersed by the grating 44 is formed on the plane mirror 64, but the intensity modulation filter 70 is disposed in the very vicinity of the plane mirror 64 as shown in FIG. Therefore, the spectrum image is also formed on the intensity modulation filter 70 in a slightly defocused state.

  FIG. 5A shows an example of a spectrum, and FIG. 5B is a front view of the intensity modulation filter 70. The intensity modulation filter 70 is a film having a light shielding part 73 that shields light and a window 72 that transmits light. For example, the intensity modulation filter 70 is formed by printing black ink as the light-shielding portion 73 on a transparent resin film having almost no birefringence, excluding an area corresponding to the window 72. The intensity modulation filter 70 modulates the light passing through the intensity modulation filter 70 based on the shape of the window 72 to a predetermined intensity as a function of the arrangement direction of the plurality of liquid crystal elements 62.

  For example, in the example shown in FIG. 5B, the width of the window 72 in the direction orthogonal to the arrangement direction of the liquid crystal elements 62 is narrower in the region where the intensity of light passing therethrough should be reduced. Thereby, the intensity modulation filter 70 receives input light to the modulation element unit 60 that is wavelength-dispersed in the arrangement direction of the liquid crystal elements 62 and output light from the modulation element unit 60, that is, re-input light to the intensity modulation filter 70. When passing, the input light and the output light are modulated to the intensity corresponding to the window 72 for each wavelength region. The window 72 has a symmetric shape with the arrangement direction of the liquid crystal elements 62 as an axis, but the shape of the window 72 may be asymmetric.

  Here, the shape of the window 72 in FIG. 5B corresponds to the intensity distribution with respect to the wavelength of the light generated by the light source 20. For example, it is assumed that the intensity I of the light generated by the light source 20 with respect to the wavelength λ has a distribution indicated by a thin line in FIG. 5A, and the wavelength λs to the wavelength λl is the use wavelength region. In this case, as shown in FIG. 5B, in the wavelength region dispersed by the grating 44, the region where the intensity of light generated by the light source 20 is larger, the width of the window 72 (the length in the vertical direction in the drawing). ). As a result, the intensity modulation filter 70 shields a relatively large amount of light in the wavelength region of the light generated by the light source 20. Therefore, as shown by the thick line in FIG. 5A, the intensity distribution of the wavelength of light reciprocating in the intensity modulation filter 70 and the liquid crystal element 62 can be made flatter than the intensity distribution of the light source 20. .

  Further, the window 72 is not limited to the shape corresponding to the wavelength intensity distribution in the light of the light source 20, but may have another shape. For example, when light passes through the optical system 32, the grating 44, the liquid crystal element 62, and the like, and there is wavelength dependency with respect to light absorption, the window 72 corresponds to the wavelength dependency by the optical system 32 or the like. The larger the absorptivity, the wider the window 72 may be.

  Furthermore, the intensity modulation filter 70 may be detachably joined to the modulation element unit 60. As a result, when the light source 20 is replaced and used, the intensity distribution filter 70 having the shape of the window 72 corresponding to the intensity distribution of the wavelength in each light source 20 is used, so that the intensity distribution can be obtained for any light source 20. It can be made flatter.

  As described above, according to the present embodiment, when using a light source such as a xenon lamp that has a protruding light intensity in a specific wavelength band, the function of the modulation element unit 60 that modulates the polarization state of each wavelength region is not used. In addition, the protruding wavelength band can be suppressed. Therefore, the modulation element unit 60 can be applied to a function of modulating the polarization state of each wavelength region, and the polarization state can be modulated with a finer gradation.

  FIG. 6 is a front view showing another example of the intensity modulation filter 70. The intensity modulation filter 70 of FIG. 6 has a pattern 74 that is uniform in the direction orthogonal to the arrangement direction of the liquid crystal elements 62 and has a lower transmittance in a region where the intensity should be reduced. For example, the pattern 74 of the intensity modulation filter 70 is formed by printing light and shade with black ink on a resin film that is transparent and has almost no birefringence.

  The light shielding portion 73 in FIG. 5 and the pattern 74 in FIG. 6 may use a mirror-like thin film such as a chrome thin film instead of the black ink. In this case, the surface of the pattern 74 is formed into a mirror surface as the region whose strength should be reduced by etching. Thereby, in the intensity | strength modulation filter 70, input light is reflected in the area | region which should make intensity | strength small. When the polarization state of the input light reflected by the intensity modulation filter 70 hardly changes while passing through the wavelength dispersion spectroscopic optical system 40 and the slit 38, the light reflected by the intensity modulation filter 70 is reflected by the polarization optical system 30. Since it is distributed from the output component and output to the discard side, it does not go out to the output light 92.

  In the embodiment shown in FIGS. 1 to 6, the modulation element unit 60 is a reflective liquid crystal, but the liquid crystal is not limited to the reflective liquid crystal. As another example, a transmissive liquid crystal may be used. In this case, the spectrum light source device 10 has the following configuration.

  That is, the spectrum light source device 10 includes the light source 20, the polarizing optical system 30, the slit 38, and the wavelength dispersion type spectroscopic optical system 40 shown in FIG. 1, and a transmission type at the position where the modulation element unit 60 in FIG. Has liquid crystal. Further, the same configuration as these is arranged at a position conjugate with the light source 20, the slit 38 and the wavelength dispersion type spectroscopic optical system 40. Thus, the spectrum light source device 10 includes the polarization optical system 30 as an input polarization optical system and an output polarization optical system conjugated with the polarization optical system 30, and a wavelength dispersion type spectroscopic optical system 40 and a wavelength multiplexing optical system conjugated with the wavelength dispersion type optical system. .

  Further, the spectrum light source device 10 is arranged between the wavelength dispersion type spectroscopic optical system 40 and the transmission type liquid crystal element, between the transmission type liquid crystal element and the wavelength multiplexing optical system, or both, as shown in FIG. It has the intensity | strength modulation filter 70 shown in FIG. Thereby, the effect similar to embodiment shown in FIGS. 1-6 can be acquired.

  In this case, instead of the polarizing beam splitter 34 and the polarizing beam splitter conjugated with the polarizing beam splitter 34, polarizing plates that transmit light in a specific polarization direction may be arranged at the respective portions. In addition, these polarizing plates are provided between the wavelength dispersion type spectroscopic system 40 and the transmissive liquid crystal element, and in the transmissive liquid crystal, instead of the polarizing beam splitter 34 and the polarizing beam splitter conjugated with the polarizing beam splitter 34 shown in FIG. It may be arranged between the element and the wavelength multiplexing optical system. In this case, the transmissive liquid crystal element and these polarizing plates modulate the intensity of the spectrum light independently of each other for each liquid crystal element, that is, for each wavelength region input to the liquid crystal element. In this case, the intensity modulation filter 70 may be disposed between the transmissive liquid crystal element and the polarizing plate, or may be disposed outside the polarizing plate.

  Further, regardless of whether the modulation element unit 60 is a reflection type or a transmission type, a conjugate image thereof may be formed and the intensity modulation filter 70 may be provided there. Thereby, the same effect as the case where the intensity modulation filter 70 is disposed in close contact with the modulation element 60 can be obtained.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

The schematic diagram of the spectrum light source device 10 which is an example of embodiment is shown. It is the front view which looked at the spatial light modulator 50 from the direction which input light inputs. 3 is a plan view of the spatial light modulator 50. FIG. 3 is a side view of the spatial light modulator 50. FIG. (A) shows an example of a spectrum, and (b) is a front view of the intensity modulation filter 70. 6 is a front view showing another example of the intensity modulation filter 70. FIG.

Explanation of symbols

  10 spectrum light source device, 20 light source, 30 polarization optical system, 32 optical system, 34 polarization beam splitter, 36 optical system, 38 slit, 40 wavelength dispersion type spectroscopic optical system, 42 collimator, 44 grating, 46 camera, 50 light spatial modulation Device, 60 modulation element section, 62 liquid crystal element, 64 plane mirror, 66 modulation element driver, 68 cover glass, 70 intensity modulation filter, 72 window, 73 light shielding section, 74 pattern, 76 protective glass, 80 traveling direction, 82 polarization direction 84 Optical system, 86 Optical fiber, 90 input light, 92 output light, 94 Discard light

Claims (7)

A light source that generates input light;
A polarization optical system that converts the input light into a specific polarization state;
A wavelength dispersive spectroscopic optical system that splits the light converted into the specific polarization state into a spectrum image spread in one direction;
A plurality of optical elements arranged along the spread direction of the spectrum image and a reflection surface, and a polarization state of the spectrum image of the input light reflected by the reflection surface and reciprocating in the plurality of optical elements, A modulation element that reflects output light, modulated independently of each other for each wavelength region that reciprocates within the plurality of optical elements based on an external command;
An intensity modulation filter that modulates the input light and the output light to a predetermined intensity for each wavelength region when the input light and the output light pass through;
The output light that has passed through the intensity modulation filter is re-input to the wavelength dispersion spectroscopic optical system and wavelength-multiplexed, and the wavelength-combined output light is re-input to the polarization optical system and is polarized. A spectrum light source device that outputs polarized light having a direction separated from other polarized light. A light source that generates input light;
An input polarization optical system for converting the input light into a specific polarization state;
A wavelength dispersive spectroscopic optical system that splits the light converted into the specific polarization state into a spectrum image spread in one direction;
A plurality of optical elements arranged along a spread direction of the spectrum image, and when the spectrum image of the input light passes through the plurality of optical elements, the polarization state is determined based on an instruction from the outside. A modulation element unit that outputs output light modulated independently for each wavelength region transmitted through the optical element;
An intensity modulation filter that modulates at least one of the input light and the output light to a predetermined intensity for each wavelength region when at least one of the input light and the output light passes;
A wavelength multiplexing optical system for wavelength multiplexing the output light of the spectrum image;
A spectrum light source device comprising: an output polarization optical system that separates and outputs polarized light having one polarization direction from the other polarized light in the wavelength-multiplexed output light. 3. The spectrum light source according to claim 1, wherein the intensity modulation filter has a window having a narrower width for transmitting light in a direction orthogonal to a direction in which the plurality of optical elements are arranged in a region where the intensity should be reduced. apparatus. The spectrum light source device according to claim 3, wherein the window has a symmetric shape with respect to a direction in which the plurality of optical elements are arranged. The intensity modulation filter has a pattern that is uniform in a direction orthogonal to the direction in which the plurality of optical elements are arranged and has a lower transmittance in a region where the intensity should be reduced. The spectrum light source device according to Item. The spectrum light source device according to claim 1, wherein the modulation element unit is a reflective liquid crystal . The spectrum light source device according to claim 2, wherein the modulation element unit is a transmissive liquid crystal .

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