JP5286648B2 - Light source device, spectrum modulator, and spectrum measuring device - Google Patents

Description

  The present invention relates to a light source device, a spectrum modulator, and a spectrum measuring device.

  Currently, monochromatic light or light having a desired spectral characteristic is required for inspection of various devices. Of these, monochromatic light can be made relatively easily by guiding light from a white light source or the like to the spectroscope. On the other hand, light having a specific wavelength distribution is used for inspection of a CCD (particularly a visible one such as a digital camera). Conventionally, a filter using a multilayer film has been used as a method for forming light having a specific wavelength distribution.

  However, in the case of a filter using a multilayer film, it can be made relatively inexpensively, but it is difficult to make a spectral distribution freely. Further, when many filters having a multilayer film formed by vapor deposition are produced, the cost can be reduced. However, when many kinds of filters are produced in small quantities, the cost is increased. In addition, filters having many types of spectral characteristics are required particularly in evaluation at the development stage.

  Further, a spectrum modulator that forms light having a wavelength distribution different from the wavelength distribution from light having a certain wavelength distribution is required for the purpose of forming light having a desired wavelength distribution.

  Furthermore, the conventional spectrum measuring apparatus measures the spectrum of light by rotating the spectroscopic element such as a diffraction grating or a prism and changing the wavelength of light incident on the light quantity measuring apparatus. There was a problem that the mechanism was complicated.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a light source device, a spectrum modulator, and a spectrum measurement device that have no movable part and can emit light having different wavelength distributions. To do.

The first means for solving the problem includes a light source, a polarization separation element, a spectroscopic element, a condensing optical system, and two polarization modulation elements, and separates the light from the light source into the polarization separation. The P-polarized light and the S-polarized light are separated from each other by guiding them to the element, and the P-polarized light and the S-polarized light are respectively incident on the spectroscopic element. Each focused light wavelength is imaged by the condensing optical system placed after the spectroscopic element, and at the imaging position, each wavelength of the dispersed P-polarized light and S-polarized light is measured. The two polarization modulation elements arranged in a line so as to correspond to the imaging position of the light are arranged so that the polarization can be modulated by a desired amount for each wavelength of the P-polarized light or the S-polarized light. The two polarization modulation elements can be controlled separately, and the polarization can be controlled. Each modulated light is returned to the spectroscopic element by advancing the optical path in reverse, where the dispersed light of each wavelength is synthesized and returned to the polarization separation element. The light source device is characterized in that light of a component whose polarization state is orthogonal to the separated light of the two optical paths is extracted from each of the corresponding light and used as output light.

The second means for solving the problem is the first means, wherein the polarization separation element is a polarization beam splitter (PBS), and the two polarization modulation elements are liquid crystal polarization modulation elements. It is characterized by being.

The first reference form of the present invention is the second means, wherein a crystal plate or a Savart plate having an optical axis inclined with respect to the incident direction of incident light is disposed between the PBS and the spectrometer. It is characterized by that.

A third means for solving the problem includes a polarization separation element, a spectroscopic element, a condensing optical system, and two polarization modulation elements, and guides light from the light source to the polarization separation element. The P-polarized light and the S-polarized light are separated from each other so that the P-polarized light and the S-polarized light are incident on the spectroscopic element, and the P-polarized light and the S-polarized light are dispersed by the spectroscopic element. For each wavelength by the condensing optical system placed after the spectroscopic element, and at the imaging position, the light having the respective wavelengths of the dispersed P-polarized light and S-polarized light is formed. The two polarization modulation elements arranged in a line so as to correspond to the imaging position are arranged, and the polarization can be modulated by a desired amount for each wavelength of the P-polarized light or the S-polarized light. The two polarization modulation elements can be controlled separately and the polarization is modulated Each light is returned to the spectroscopic element by traveling in the reverse direction of the optical path, where the dispersed light of each wavelength is synthesized, returned to the polarization separation element, and separated by the polarization separation element at the time of incidence. A spectral modulator characterized in that light of a component whose polarization state is orthogonal to light of two optical paths is extracted from the corresponding light and used as output light.

A fourth means for solving the problem is the third means, wherein the polarization separation element is a polarization beam splitter (PBS), and the two polarization modulation elements are liquid crystal polarization modulation elements. It is characterized by being.

The second reference form of the present invention is the fourth means, wherein a crystal plate or a Savart plate having an optical axis inclined with respect to the incident direction of incident light is disposed between the PBS and the spectrometer. It is characterized by that.

A fifth means for solving the problem includes a polarization separation element, a spectroscopic element, a condensing optical system, two polarization modulation elements, and a light amount detector, and outputs light from the light source. The P-polarized light and the S-polarized light are separated from each other by guiding to a polarization separation element, and the P-polarized light and the S-polarized light are respectively incident on the spectral element. The light dispersed in step S is imaged by the condensing optical system placed after the spectroscopic element for each wavelength, and the dispersed P-polarized light and S-polarized light respectively The two polarization modulation elements arranged in a line so as to correspond to the imaging position of the light of the wavelength of the light are arranged, and the polarization is modulated by a desired amount for each wavelength of the P-polarized light or the S-polarized light. The two polarization modulation elements can be controlled separately so that Each light whose polarization is modulated is returned to the spectroscopic element by traveling in the reverse direction of the optical path, where the dispersed light of each wavelength is synthesized and returned to the polarization separation element again. In the polarization separation element, The light of the component whose polarization state is orthogonal to the light of the two optical paths separated at the time of incidence is taken out from each corresponding light, the light quantity is measured by the light quantity detector, and the modulation amount by the two polarization modulation elements and the The spectrum measuring apparatus is characterized in that a spectral characteristic of incident light is obtained from a relationship between light amounts measured by a light amount detector.

A sixth means for solving the problem is the fifth means, wherein the polarization separation element is a polarization beam splitter (PBS), and the two polarization modulation elements are liquid crystal polarization modulation elements. It is characterized by being.

The third reference form of the present invention is the sixth means, wherein a crystal plate or a Savart plate whose optical axis is inclined with respect to the incident direction of incident light is disposed between the PBS and the spectrometer. It is characterized by that.

  According to the present invention, it is possible to provide a light source device, a spectrum modulator, and a spectrum measuring device that have no movable part and can emit light having different wavelength distributions.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an outline of an optical system of a spectrum modulator as an example of an embodiment of the present invention. 1A is a view of half of the optical system (up to the diffraction grating) as viewed from above, FIG. 1B is a view of the optical system as viewed from side, and FIG. 1C is a view of FIG. FIG. 6 is a view of the remaining part of the optical system (diffractive grating is shown in both drawings) not shown in FIG.

  As shown in FIGS. 1A and 1B, incident light enters a polarization beam splitter (PBS) 1 in which two triangular prisms are bonded together. A coating surface that reflects S-polarized light and transmits P-polarized light is applied to the bonding surface 2 of one triangular prism constituting the PBS 1. Therefore, the light incident on this surface is divided into P-polarized light and S-polarized light components, respectively, and is guided to two different optical paths.

  The light separated into the two optical paths is totally reflected by the side surfaces of the prisms constituting the PBS 1 and enters the pinholes of the pinhole plate 3 placed on the rear surface of the prisms constituting the PBS 1. At this time, as shown in the figure, two pinholes are prepared for P-polarized light and S-polarized light. Further, the light from the light source is made incident on the PBS 1 with the condensed light by a lens or the like so as to be condensed into the pinhole.

  Then, as shown in FIGS. 1A and 1B, the light emitted from the pinhole is collimated by the spherical mirror 4 placed thereafter to become a parallel light beam and enters the diffraction grating 5. Then, the light wavelength-dispersed by the diffraction grating 5 as shown in FIG. 1 (b) is condensed by the spherical mirror 6 as shown in FIGS. 1 (b) and 1 (c). A pinhole image is created at a position conjugate to the pinhole. Specifically, two rows of line-shaped images can be formed corresponding to the dispersion of light of P-polarized light and S-polarized light. In this embodiment, a reflective LCOS (Liquid Crystal on Silicon) element array 7 is placed in accordance with the imaging position of the pinhole image of the two rows of lines. This LCOS element array 7 is shown in FIG. As shown in FIG. 1C, it has a two-stage (corresponding to P-polarized light and S-polarized light) line, and corresponds to a pinhole image.

  Then, the polarization of the light incident on the LCOS element array 7 is modulated by the LCOS element. Specifically, the polarization axis of the LCOS element is inclined by 45 ° with respect to the optical axes of the P-polarized light and the S-polarized light, and it is possible to freely apply a phase difference between the electric field component in the direction and the direction orthogonal thereto. ing. Due to the modulation, the incident light, which was linearly polarized light, becomes elliptically polarized light, and travels by reversing the incident optical path after being reflected. Then, the light collimated by the spherical mirror 6 enters the diffraction grating 5, and the wavelength-dispersed light is combined and incident on the spherical mirror 4 and is condensed on the pinhole. The light that has passed through the pinhole enters the PBS 1.

  The light that has returned to PBS 1 is modulated by the LCOS element and becomes elliptically polarized light as described above. S polarization component is included. Among these, the P-polarized component passes through the PBS1 coat and returns in the same direction as the incident light, but the S-polarized component is reflected by the PBS1 coat and the direction written as the emitted light in FIG. Is injected into.

  Similarly, the S-polarized light separated by PBS 1 and directed to the pinhole plate 3 includes a P-polarized component when it returns to PBS 1. Of these, the S-polarized component is reflected by the PBS1 coat and returns in the same direction as the incident light, but the P-polarized component is transmitted through the PBS1 coat and is the direction written as exiting light in FIG. Is injected into.

  In this way, only the component modulated by the LCOS element can be extracted in the direction written as “emitted light” in FIG. 1A, and accordingly, the degree of modulation in each LCOS element of the LCOS element array 7 By controlling, light having different spectral distributions can be extracted and used as a spectrum modulator. Since there are two LCOS element arrays 7 for P-polarized light and S-polarized light, the polarization state of the emitted light can also be controlled by controlling these separately.

  In the above description, the embodiment as a spectrum modulator has been described. However, if a predetermined light source is added to the optical system shown in FIG. 1, it is obvious that these can be used as a light source capable of controlling the spectrum distribution.

  If a light amount detector for measuring the amount of emitted light is added to the optical system shown in FIG. 1, these can be used as a spectrum measuring device. For example, among the LCOS elements constituting the LCOS element array 7, in the LCOS element corresponding to one wavelength, all (or specified%) of the incident P-polarized light is converted to S-polarized light, and all of the incident S-polarized light (or the above-mentioned) If modulation is performed so that the specified%) becomes P-polarized light, the other wavelengths are not modulated, P-polarized light is reflected by P-polarized light, and S-polarized light is reflected by full-polarized light. Only the light of the wavelength multiplied by is detected by the light amount detector. If this measurement is performed by sequentially changing the wavelengths to be modulated, the spectral distribution of the incident light can be measured. This spectrum measuring instrument has no mechanical moving parts and has a simple mechanism.

  FIG. 2 is a diagram showing a modification of PBS 1 in FIG. The optical system other than the configuration of the PBS 1 is the same as that shown in FIG. 1 and is shown in a simplified manner. This PBS 1 is composed of four prisms, and a coating that reflects S-polarized light and transmits P-polarized light is applied to the bonding surface of the prisms 11 and 12. Therefore, the light incident on this surface is divided into P-polarized light and S-polarized light components, respectively, and is guided to two different optical paths. The S-polarized light is reflected and enters the prism 13, is totally reflected by the cut surface of the prism 13, exits from the prism 13, and travels to the next optical system. The P-polarized light passes through the coating surface, is totally reflected by the cut surface of the prism 12 and enters the prism 14, is totally reflected by the cut surface of the prism 14, exits from the prism 14, and travels to the next optical system. In this case, although the shape is slightly complicated, since the surfaces of the prisms intersect at only 90 ° or 45 °, processing is easy depending on the case. The operation of this beam splitter is the same as that shown in FIG.

  In the above description, the polarization beam splitter (PBS) is used as the polarization separation element, and the liquid crystal modulation polarization element LCOS is used as the polarization modulation element. In addition, the polarization separation element is composed of an optical crystal, etc. In addition, a magneto-optic spatial light modulator or the like can also be used as the polarization modulation element.

  FIG. 3 is a view in which a crystal plate 15 is provided after PBS 1 in FIG. 1 (between PBS 1 and pinhole plate 2). The crystal axis of this crystal plate is inclined with respect to the optical axis direction of the incident light. In this case, the P-polarized light is an ordinary ray and the S-polarized light is an extraordinary ray. Therefore, the S-polarized light travels in the oblique direction in the crystal plate 14 and proceeds in the original optical axis direction after exiting the crystal plate 15. That is, the optical axis shifts in the vertical direction in the figure.

  As a result, as shown in FIG. 3, the point where the incident light is incident on the bonding surface 2 and the point where the emitted light is emitted from the bonding surface 2 are different from each other in the horizontal direction of the drawing. Thereby, there is an advantage that the extinction ratio can be increased as compared with the case where the PBS 1 is used alone. The same effect can be obtained by using a Savart plate instead of the crystal plate.

It is a figure which shows the outline | summary of the optical system of the spectrum modulator which is an example of embodiment of this invention. It is a figure which shows the modification of PBS in FIG. It is the figure which provided the wavelength plate or the Savart plate after PBS in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... PBS (polarization beam splitter), 2 ... Prism bonding surface, 3 ... Pinhole plate, 4 ... Spherical mirror, 5 ... Diffraction grating, 6 ... Spherical mirror, 7 ... LCOS element array

Claims (6)

  It has a light source, a polarization separation element, a spectroscopic element, a condensing optical system, and two polarization modulation elements, and guides light from the light source to the polarization separation element to separate the optical paths of P-polarized light and S-polarized light. Then, the P-polarized light and the S-polarized light are respectively incident on the spectroscopic element, and the P-polarized light and the S-polarized light are placed after the spectroscopic element for each light wavelength dispersed by the spectroscopic element. In addition, the light is imaged by the condensing optical system, and the image forming positions are linearly formed so as to correspond to the image forming positions of the dispersed wavelengths of the P-polarized light and the S-polarized light. The two polarization modulation elements are arranged side by side, and the two polarization modulation elements can be separately controlled so that the polarization can be modulated by a desired amount for each wavelength of the P-polarized light or the S-polarized light. Yes, each polarization-modulated light travels backwards in the optical path The light is then returned to the spectroscopic element, where the dispersed wavelengths of light are combined, returned to the polarization separation element, and the polarization separation element is a component in which the polarization state is orthogonal to the light in the two optical paths separated upon incidence. Is extracted from each of the corresponding lights to be output light.   The light source device according to claim 1, wherein the polarization separation element is a polarization beam splitter (PBS), and the two polarization modulation elements are liquid crystal polarization modulation elements.   A polarization separation element, a spectroscopic element, a condensing optical system, and two polarization modulation elements, and guides light from the light source to the polarization separation element to separate optical paths of P-polarized light and S-polarized light; The P-polarized light and the S-polarized light are respectively incident on the spectroscopic element, and the light dispersed by the spectroscopic element for each of the P-polarized light and the S-polarized light is placed after the spectroscopic element for each wavelength. Each image is formed by a condensing optical system, and the image forming positions are arranged in a line so as to correspond to the image forming positions of the dispersed wavelengths of the P-polarized light and the S-polarized light. The two polarization modulation elements are arranged, and the two polarization modulation elements can be separately controlled so that the polarization can be modulated by a desired amount for each wavelength of the P-polarized light or the S-polarized light, Each polarization-modulated light travels in the reverse direction of the optical path. Is returned to the spectroscopic element, where the dispersed light of each wavelength is synthesized, returned to the polarization separation element again, and the polarization separation element is light of a component whose polarization state is orthogonal to the light of the two optical paths separated upon incidence. Is extracted from the corresponding light and used as output light. The spectrum modulator according to claim 3 , wherein the polarization separation element is a polarization beam splitter (PBS), and the two polarization modulation elements are liquid crystal polarization modulation elements.   A polarization separation element, a spectroscopic element, a condensing optical system, two polarization modulation elements, and a light amount detector, and guides light from the light source to the polarization separation element to provide optical paths of P-polarized light and S-polarized light The P-polarized light and the S-polarized light are respectively incident on the spectroscopic element, and the light dispersed by the spectroscopic element for each of the P-polarized light and the S-polarized light is separated for each wavelength of the spectroscopic element. Images are formed by the condensing optical system placed later, and the image forming positions correspond to the image forming positions of the dispersed wavelengths of the P-polarized light and the S-polarized light, respectively. The two polarization modulation elements are arranged in a line, and the two polarization modulation elements are separately provided so that the polarization can be modulated by a desired amount for each wavelength of the P-polarized light or the S-polarized light. Controllable, each polarization modulated light, reverse the optical path The light is returned to the spectroscopic element by proceeding there, where the dispersed light of each wavelength is synthesized and returned to the polarization separation element. The polarization separation element and the polarization state of the two light paths separated upon incidence are orthogonal to each other. The component light is extracted from each of the corresponding lights, the light amount is measured by the light amount detector, and incident from the relationship between the modulation amount by the two polarization modulation elements and the light amount measured by the light amount detector. A spectrum measuring apparatus characterized by obtaining a spectral characteristic of light. The spectrum measuring apparatus according to claim 5 , wherein the polarization separation element is a polarization beam splitter (PBS), and the two polarization modulation elements are liquid crystal polarization modulation elements.

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