JPH0732506U - Michelson interferometer - Google Patents

Abstract

(57) [Summary] [Objective] The present invention aims to realize an optical measurement device that can always maintain good measurement accuracy by eliminating the cause of measurement error regardless of the polarization state of incident light. To do. A deflection separation element 16 is provided after a collimated parallel beam of incident light 11. Then, after the polarization component is separated into two light components orthogonal to each other, they are incident on the beam splitter 12. The incident light beam at this time is made incident at an angle of 45 degrees with respect to the deflection direction of the crystal of the beam splitter 12, one light ray is made incident at +45 degrees, and the other light ray is made −
It is incident at an angle of 45 degrees. Then, the emitted light beam after being interfered by the beam splitter 12 is condensed and received by the light receiver 15
Michelson interferometer configured to convert to an electric signal by.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an optical device that eliminates an error in measurement data due to the polarization state of incident light due to the polarization-dependent characteristics of the beam splitter itself in the field of optical measurement.

[0002]

[Prior art]

 First, an example of an optical block diagram of the optical interferometry (Michelson interferometer) in FIG. 2 and its calculation formulas 51 to 54 will be shown to explain the outline of the error factors in the optical power spectrum detection.

Incident light 11 is incident on a beam splitter 12 and is branched into two directions on the inclined surface of the prism, and one is reflected by a fixed reflecting mirror 14 and is incident on the beam splitter 12 again on an optical path 14 a. . On the other hand, the optical path length L2 is finely adjusted by the variable reflecting mirror 13 to become the optical path 13a, and both are interfered and combined by the beam splitter and emitted to the optical paths 15a and 15b. The interference output of one optical path 15a is received by the optical receiver 15a. Is converted into an electric signal with.

However, in the present configuration, due to the influence of the polarization-dependent characteristics of the beam splitter 12 itself, even if the incident powers are the same, under the condition of the incident light 11 in different deflection states, the output after interference is output. Changes, resulting in a change in the measured output level. This will be described below by showing a calculation formula.

[0005]

[Equation 1]

In the calculation formula, the beam splitter 12 will be described with the amplitude reflection intensities for S waves and P waves as √Rs and √Rp, and the amplitude transmission intensities as √Ts and √Tp.

The emission power of the S wave after the interference is calculated by the equation 51, and the emission power of the P wave after the interference is calculated by the equation 52. Here, even if the input light power (the left side of Expression 53) is constant, there can be a plurality of combinations of the S wave component and the P wave component on the right side depending on the deflection state. In this calculation formula, E0s is the power of the incident light S wave component, E0p is the power of the incident light P wave component, E1s is the power of the interference light S wave component, and E1p is the power of the interference light P wave component. Where √Rs and √Rp are amplitude reflection intensities, √Ts and √Tp are amplitude transmission intensities, and D is an optical path difference.

First, the output power after the interference result that has passed through the beam splitter 12 is the calculation formula of Expression 54. As can be seen from this equation 54, there are elements of E0s amplitude and E0p amplitude. Therefore, even if the incident power is the same, it means that the output fluctuates when the deflected state of the incident light 11 is different.

Conventionally, as a countermeasure against this, the beam splitter 12 itself has been provided with a means for eliminating the polarization dependent characteristic by a coating process, but in this case, the usable wavelength range is limited to a narrow range. Therefore, it is practically inconvenient as a measuring instrument.

[0010]

As described above, in the related art, the optical power level of the measurement incident light 11 is only changed when the polarization state of the incident light does not change, when the light is circularly polarized, or when it is randomly polarized. However, there is a problem that the measurement output level fluctuates in the case of linear deflection, and there is a limitation in use that the measurement accuracy will vary depending on the condition of the incident light to be measured. It was Therefore, it is not always a good measuring device. This causes a measurement error in the measurement of the light source whose polarization state changes, which is not preferable in use.

Therefore, the problem to be solved by the present invention is to realize an optical measuring device that can always perform accurate measurement by eliminating the cause of measurement error regardless of the polarization state of incident light and maintain good accuracy. The purpose is to do.

[0012]

[Means for solving the problem]

 (Solution to Claim 1) In order to solve the above-mentioned problems, in the structure of the present invention, the incident light 11 which is a collimated parallel light beam is incident to separate the deflection component into two orthogonal light components. The element 16 is provided. Then, when the light emitted from the deflection separation element 16 is incident on the beam splitter 12, the incident light ray is incident at an angle of 45 degrees with respect to the deflection direction of the crystal of the beam splitter 12, and one light ray is +45 degrees. Then, the other ray is provided with a beam splitter 12 which provides an optical arrangement that allows the other ray to be incident at an angle of -45 degrees. Then, the Michelson interferometer is provided with a configuration in which a light receiver 15 that collects the outgoing light beam after being interfered by the beam splitter 12 and converts it into an electric signal is provided.

(Means for Solving Claim 2) Further, the Michelson interferometer has a configuration in which a collimator 17 for collimating (collimating) the uncollimated incident light 11 is provided in the above configuration. With this configuration, it is possible to realize measurement even with an incident light beam in a non-collimated state, such as an incident light beam from an optical fiber.

[0014]

[Action]

 As shown in FIG. 1, the polarization separation element 16 is provided for the incident light 11 to separate the polarization component into two orthogonal light components, so that the P-wave incident angle and the S-wave incident angle of the beam splitter 12 are Thus, one ray can be made incident at +45 degrees and the other ray can be made incident at -45 degrees. When the light beam split into two by the polarization splitting element 16 is made incident at an angle of 45 degrees with respect to the deflection direction of the crystal of the beam splitter 12, the P wave and S wave components have the same effect.

[0015]

【Example】

 First, an outline of implementation will be described. In this embodiment, a deflecting / separating element 16 is provided after the collimated parallel beam of the incident light 11 to separate the deflecting component into two orthogonal light components, which are then incident on the beam splitter 12. Here, this incident light beam is made incident at an angle of 45 degrees with respect to the deflection direction of the crystal of the beam splitter 12 (deflection direction of the beam splitter). As a result, one light ray is incident at +45 degrees and the other light ray is incident at -45 degrees. Then, the optical path 15a after being interfered by the beam splitter 12 is provided with a condenser lens 18, is condensed, and then is incident on the photodetector 15 to be converted into an electric signal.

Regarding this, an example of an optical block diagram of the optical interferometry (Michelson interferometer) by the beam splitter of FIG. 1 and its calculation formulas 61 to 64 are shown to explain the details of the optical power spectrum detection. To do.

[0017]

[Equation 2]

First, the polarization separation element 16 is provided for the incident light 11 to separate the polarization component into two orthogonal light components. Next, the P-wave and S-wave of the beam splitter 12 are made incident with a polarization plane of ± 45 degrees. That is, one light ray is incident at +45 degrees and the other light ray is incident at -45 degrees. As a result, the calculation formula shown in Formula 61 is obtained. An example of the deflection separation element 16 used here is a compound element (Rochor prism, Wollaston prism, Savart plate, etc.).

Here, (E0 +) of the equation 61 is the amplitude of the +45 degree component of the incident light, and (E0−) is the amplitude of the −45 degree component of the incident light. The output after the interference by the beam splitter 12 is as shown in equation 62 on the (E0 +) side and as shown in equation 63 on the (E0-) side. Therefore, the power output obtained by adding both is as shown in Expression 64. In Equation 64, (E0 +) and (E0-) from Equation 61 become E0 on the left side, and as a result, the deflection element of ± 45 degrees disappears and only the element of the incident light 11 itself becomes. This indicates that it is not affected by the amplitudes of the S deflection component and P deflection component of the incident light. That is, it means that it does not become an interference error factor in any deflected state of the incident light.

When the incident beam is separated into ± 45 degrees in order to realize the above-mentioned deflection separation element 16, both light rays pass through different optical paths, so that the optical path length is the same or the optical path difference is There is a method of synthesizing waveforms based on the above, or synthesizing after frequency conversion. Also, when separating diffused light, it passes through the above-mentioned compound image before entering the interferometer, collimates after polarization separation and enters the beam splitter 12, and after interference, it collects again the polarization separation. The formed lights are imaged separately. In this case, the separated light beams interfere with each other in the same optical path, so that they can be easily combined.

[0021]

[Effect of device]

 Since the present invention is configured as described above, it has the following effects. Even if the deflection state of the incident light changes, there is an advantage that there are almost no error factors in the measurement of the measurement power level. This has the effect of realizing optical power measurement without having to be aware of the unknown polarization state of incident light.

Further, as a result of eliminating the polarization dependence of the incident light, it can be used as a particularly effective measuring device in an incident light beam in an unknown deflection state or in a measurement mode in which the deflection state of the incident light is changed. Become. In the past, in the measurement mode in which the deflection state changed, it was unclear whether or not the output value was a true measurement value. However, this configuration has almost no deflection dependence, so that stable optical power measurement can be achieved. .

[Brief description of drawings]

FIG. 1 is an optical block diagram of optical interferometry (Michelson interferometer) of the present invention.

FIG. 2 is an example of an optical block diagram of conventional optical interferometry (Michelson interferometer).

[Explanation of symbols]

 11 Incident Light 12 Beam Splitter 13 Variable Reflector 14 Fixed Reflector 15 Light Receiver 16 Deflection Separation Element 17 Collimator 18 Condenser Lens

Claims (2)

[Scope of utility model registration request] 1. A polarization separation element (16) for separating collimated incident light (11) to separate a polarization component into two orthogonal light components in measurement of light power using an optical interferometer.
Is provided, and when the light emitted from the deflection separation element (16) is incident on the beam splitter (12), the incident light beam is incident at an angle of 45 degrees with respect to the deflection direction of the crystal of the beam splitter (12). And one ray is +45 degrees and the other ray is -4
A beam splitter (12) for entering at an angle of 5 degrees is provided, and a light receiver (15) for converging an outgoing light beam after being interfered by the beam splitter (12) and converting it into an electric signal is provided. A Michelson interferometer characterized by having the above. 2. A collimator (17) for collimating (collimating) uncollimated incident light (11).
The Michelson interferometer according to claim 1, further comprising: