JP2014123669A - Light source device, control method, and shape measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light source device capable of stabilizing the wavelength of light from a light source.SOLUTION: The light source device includes: a wavelength reference part changing the intensity of the light from the light source, according to the change of the wavelength of the light from the light source; a first detection part detecting the intensity of the light passing through the wavelength reference part; a second detection part detecting the intensity of the light not passing through the wavelength reference part; an optical element dividing the light from the light source into the light made incident on the first detection part and the light made incident on the second detection part by a light division surface; an arithmetic part obtaining the change of the wavelength of the light by using the intensity of the light detected by the first detection part and the second detection part; and a control part controlling the wavelength of the light. The second detection part includes: a detector detecting the intensity of the light transmitted through the light division surface or another light division surface having the same configuration as that of the light division surface; and a detector detecting the intensity of the light reflected by the light division surface or the another light division surface.

Description

  The present invention relates to a light source device. More specifically, the present invention relates to an apparatus for stabilizing the wavelength of light emitted from a light source device.

  High-precision light source devices have been developed for applications such as laser light sources for high-precision length measurement interferometers and semiconductor lasers used for DWDM optical communication, which is one of optical wavelength division multiplexing communications. Yes. A highly accurate light source device here is a light source device provided with a device for stabilizing the wavelength of light from the light source.

  Generally, a light source device is a light source whose wavelength is stabilized, a wavelength discriminator that converts a wavelength change of light from the light source into a light intensity change, and detects light from the wavelength discriminator and converts the light intensity into an electrical signal. A photodetector. Furthermore, the light source device has an arithmetic unit that calculates a modulation change (also referred to as a wavelength error) from the electrical signal detected by the photodetector.

  Furthermore, a control unit for obtaining a control signal for controlling the wavelength of the light source from the wavelength error signal obtained by the computing unit, and a wavelength changer for changing the wavelength of the light source based on the control signal. A light source device that stabilizes the wavelength of the light source in this manner is described in Patent Document 1.

  In addition, the light source device stabilization method includes a method involving wavelength modulation in the error signal generation process (modulation method) and a method not requiring wavelength modulation (non-modulation method). In the non-modulation method, the light source can be simplified and the cost can be easily reduced as compared with the modulation method. Patent Document 2 discloses a light source device used in a semiconductor laser for optical communication.

  The light source device divides light from the light source into light output from the light source device and light used to stabilize the wavelength using a half mirror. The light used to stabilize the light source is further split using a beam splitter into light that is transmitted through the wavelength discriminator and incident on the photodetector and light that is directly incident on another photodetector.

  By detecting the intensity of each of the two divided lights, it is possible to know a change in the transmittance of light that has passed through the wavelength discriminator even if the output of the light source itself changes (changes in light intensity). Therefore, the wavelength change can be measured from the change in the transmittance of the light transmitted through the wavelength discriminator, and the wavelength changer is controlled from the obtained wavelength change.

Japanese Patent Application Laid-Open No. 07-099361 JP 2002-185074 A

  However, the beam splitter that splits the light from the light source into two lights changes in transmittance and reflectance as time passes. This is because a change in temperature due to the light splitting surface (dielectric multilayer film) of the beam splitter absorbing light and generating heat affects the transmittance and the reflectance. If the transmittance changes during the measurement of the wavelength change, the change in the intensity of the light transmitted through the wavelength discriminator is due to the wavelength change, or the change in the transmittance and reflectance of the beam splitter. It cannot be distinguished.

  For this reason, changes in the transmittance and reflectance of the beam splitter affect the change in the transmittance of the light that is detected by being transmitted through the wavelength discriminator, and erroneously changes the wavelength of the light from the light source. There is a fear.

  Therefore, an object of the present invention is to provide a light source device capable of stabilizing the wavelength of light from a light source with high accuracy.

  The light source device of the present invention includes a light source, a wavelength reference unit that changes the intensity of light from the light source according to a change in wavelength of the light from the light source, and a light source that passes through the wavelength reference unit. 1 detector, a second detector for detecting the intensity of light that does not pass through the wavelength reference unit, light from the light source incident on the first detector by a light splitting surface, and the second detector The optical element that is divided into incident light, the light intensity detected by the first detection unit, and the light intensity detected by the second detection unit are used to transmit light from the light source that has passed through the wavelength reference unit. A light source device comprising: a calculation unit for obtaining a wavelength change; and a control unit for controlling a wavelength of light from the light source based on the wavelength change obtained by the calculation unit, wherein the second detection unit is the light Transmits through the splitting plane or another splitting plane with the same configuration as the splitting plane A detector for detecting the intensity of light was, characterized in that it comprises a detector for detecting the intensity of the light reflected the light splitting surface or the other light splitting surface.

  Since the second detection unit includes a detector that detects the intensity of the light that has been transmitted through and reflected from the light dividing surface or another light dividing surface that has the same configuration as the light dividing surface, the reflectance of the light dividing surface and It is possible to provide a light source device that can cancel the influence of the change in transmittance and stabilize the wavelength of light from the light source.

It is the figure which showed the light source device of 1st Embodiment. It is the figure which showed the light source device of 2nd Embodiment. It is the figure which showed the light source device of 3rd Embodiment. It is the figure which showed the conventional non-modulation type light source device. It is the figure which showed the transmittance | permeability change with respect to the wavelength of a wavelength discriminator. It is the figure which showed the measuring device of 4th Embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, in each figure, the same reference number is attached | subjected about the same member and the overlapping description is abbreviate | omitted.

  First, the principle of a technique for stabilizing the wavelength of light from a light source will be described using the light source device 400 of FIG. Here, the non-modulation method will be described.

  The light source device 400 includes a light source 1, a half mirror 2, a beam splitter 3 that divides an optical path of transmitted light that has passed through the half mirror 2, a wavelength discriminator 4 (wavelength reference unit), and a detection that detects the intensity of light from the light source 1. And a detector 60 for detecting light transmitted through the wavelength discriminator 4.

  Further, the light source device 400 includes an error signal calculator 8 (calculation unit) for obtaining a wavelength error of light from the light source using outputs of the detector 50 and the detector 60, and a light source based on the output of the error signal calculator 8. 1 has a control unit 9 for controlling one wavelength. The light source device 400 includes the output unit 10 for outputting light with a stable wavelength.

  The half mirror 2 divides the light from the light source 1 into light incident on the output unit 10 (output light) and light incident on the beam splitter 3 (controlled light). Here, the reflected light reflected from the half mirror 2 is incident on the output unit 10 and the transmitted light transmitted through the half mirror 2 is incident on the beam splitter 3, but the transmitted light is incident on the output unit 10 and the reflected light is beamed. The structure which injects into the splitter 3 may be sufficient. The light incident on the beam splitter 3 is used as controlled light in order to control the wavelength of the light source 1. That is, the light from the light source 1 is split into output light and controlled light by the half mirror 2.

  The beam splitter 3 (divider) divides the controlled light into light incident on the detector 50 and light incident on the wavelength discriminator 4. The controlled light that has passed through the wavelength discriminator 4 is guided to the detector 60. That is, the controlled light transmitted through the half mirror 2 is branched into light incident on the detector 50 (second detection unit) and light incident on the detector 60 (first detection unit) by the beam splitter 3. Here, a Fabry-Perot etalon, a gas cell, or the like is used as the wavelength discriminator 4.

  Next, the light intensity incident on the detector 50 and the detector 60 will be described.

The intensity of the light from the light source 1 I _o, the transmittance T ₂ of the half mirror _2, the reflectivity of the beam splitter 3 to the R ₃ and transmittance T _3. Here, an element having no loss due to absorption is used as the beam splitter 3, and T ₃ = 1−R ₃ is set. Furthermore, transmission of a wavelength discriminator 4 by wavelength difference Δλ of the reference transmittance in the wavelength discriminator 4 from T _d, the reference wavelength lambda _d at the reference wavelength is the target wavelength of the light source device 400 for lambda _d, the reference wavelength lambda _{d Let the} rate change be ΔTd.

FIG. 5 is a diagram showing the transmittance with respect to the wavelength of the light transmitted through the wavelength discriminator 4. It is the figure shown about the case where a gas cell is used as the wavelength discriminator 4. FIG. FIG. 5 shows the relationship between the reference wavelength λ _d , the wavelength difference Δλ, the reference transmittance T _d , and the transmittance change ΔT _d .

If the reflectivity R ₃ = T _d / (1 + T _d ) of the beam splitter 3 in order to make the output levels of the detector 50 and the detector 60 equal, the light intensity I ₅₀ incident on the detector ₅₀ and the detector 60 The incident light intensity I ₆₀ is expressed by the following equations (1) and (2).

The light intensity _{I 50} is converted into a voltage signal _{V 50} by the detector 50, the light intensity _{I 60} is converted into a voltage signal _{V 60} by the detector 60, _E an error signal E by error signal calculator 8 _{= V} 60 / _V determined as ₅₀ -1. From the equations (1) and (2), the error signal E becomes the following equation (3).

From the equation (3), the error signal E is proportional to the transmittance change ΔT _d and is not affected by the light intensity I _o of the light source 1. Therefore, as shown in FIG. 5, it can be seen that the transmittance change ΔT _d is caused by the wavelength difference Δλ of the light from the light source 1. By controlling the wavelength of light from the light source 1 by the control unit 9 based on the error signal E, the wavelength of light output from the output unit 10 can be stabilized.

However, the light source device 400 shown in FIG. 4 has a problem that a slight change in the reflectance R ₃ and the transmittance T ₃ of the beam splitter 3 lowers the wavelength stability. Equation (1) and the change in reflectance of the beam splitter 3 and [Delta] R ₃ in (2), the error signal E is the following equation when there is no wavelength error in the light from the light source 1 ([Delta] T d _{= 0)} (4) It becomes.

That is, when the reflectance R ₃ of the beam splitter 3 is changed, the error signal E is output by the error signal computing unit 8 even if there is no wavelength difference Δλ to light from the light source 1. If the control unit 9 controls the light source 1 based on the error signal E, the stability of the wavelength is lowered.

For example, when a hydrogen cyanide-enclosed gas cell (SRM2519a) is used for the wavelength discriminator 4, the typical value of the absorption line (FIG. 5) indicating the transmittance with respect to the wavelength of light transmitted through the gas cell is a peak transmittance T _c = 0.65. The full width at half maximum is about 15 pm. At this time, the relationship between the transmittance change ΔT _d and the wavelength change Δλ is ΔT _d ≈4.7E10 × Δλ. Assuming that the reference transmittance Td = (1 + T _c ) /2=0.83 and ΔR ₃ << T _d , the wavelength of light from the light source with respect to the reflectance change of the beam splitter 3 is obtained from the equations (4) and (3). The error (wavelength change Δλ) given to is given by the following equation (5).

Wavelength error Δλ where the reflectance changes [Delta] R ₃ of the beam splitter 3 is changed 0.1% from the formula (5) is 70fm (9MHz). In general, it is difficult to stabilize an optical element with an accuracy of 0.1%. For this reason, it has been difficult to stabilize the wavelength in the order of MHz in the conventional method of stabilizing the light source.

(First embodiment)
FIG. 1 is a diagram illustrating a light source device 100 according to the first embodiment.

  The light source device 100 according to the first embodiment includes a light source 1, a half mirror 2, a beam splitter 3, a wavelength discriminator 4, a detector 50, a detector 51, a detector 60, and an error signal calculator 8. And a control unit 9 and an output unit 10. In the present embodiment, the second detection unit that detects light that does not pass through the wavelength discriminator includes a detector 50 and a detector 51.

  Hereinafter, the configuration of the light source device 100 of the first embodiment will be described in detail. In the first embodiment, a 1.5 μm wavelength band distributed feedback (DFB) semiconductor laser is used as the light source 1. As the light source 1, other semiconductor lasers or fiber lasers may be used.

  The half mirror 2 (light splitter) divides the light from the light source 1 into light output from the output unit 10 and light (controlled light) used to control the wavelength of light from the light source. Here, as the half mirror, a wedge-type glass substrate coated with a chromium film (reflection film) is used.

  The light transmitted through the half mirror 2 is split into light that passes through the wavelength discriminator 4 by the optical element (beam splitter 3) and light that enters the detector 50 or the detector 51 without passing through the wavelength discriminator 4. Is done. In the first embodiment, a beam splitter 3 in which three right angle prisms are bonded together is used. A dielectric multilayer film is formed as a reflective film on the reflective surface (light splitting surface) of the beam splitter 3. Further, the beam splitter 3 is coated with an antireflection film on its entrance surface and exit surface, and has a characteristic that there is almost no unnecessary return light.

  Another configuration of the beam splitter 3 may be a configuration in which two beam splitters each having two right-angle prisms bonded together are arranged close to each other. Moreover, it is good also as a structure which has arrange | positioned the glass flat plate (optical element) in which the dielectric multilayer film was formed as a reflecting film on the light division surface instead of the right angle prism.

  The wavelength discriminator 4 uses a gas cell in which hydrogen cyanide gas is sealed in an optically transparent sealed container. Hydrogen cyanide gas has a large number of absorption lines in the 1.5 μm wavelength band and is widely used as a wavelength reference for a stabilized light source in an optical communication band. As another wavelength discriminator, a gas cell or etalon in which another gas such as acetylene is sealed may be used.

  The detector 50, the detector 51, and the detector 60 are InGaAs type photodiodes having a wavelength band of 1.5 μm. As another detector, a detector having an appropriate sensitivity to the wavelength of light from the light source 1, such as an avalanche photodiode, can be used.

  The error signal calculator 8 is composed of an electric circuit such as an amplifier and an operational amplifier, and based on signals from the detectors 50, 51 and 60, a voltage signal (error signal) proportional to the wavelength of light from the light source 1 by calculation described later. Is output.

  The control unit 9 is composed of a control arithmetic unit on which an integrated circuit such as a PC or FPGA (Field Programmable Gate Array) is mounted, and an LD driver that can arbitrarily set the driving current and operating temperature of the semiconductor laser of the light source 1. . Although the wavelength of the DFB semiconductor laser can be changed by changing the drive current or the operating temperature, in this embodiment, the output signal (control signal) from the control arithmetic unit is output in a state where the temperature is controlled to be constant. The light source 1 is controlled by changing the drive current.

Next, an operation principle of stabilizing the wavelength of light from the light source 1 in the first embodiment will be described. At the start of wavelength stabilization, the light source 1 is adjusted to the operating temperature by the control unit 9 and is simultaneously started up with an initial driving current. The operating temperature and the initial drive current are set so that the oscillation wavelength substantially matches the reference wavelength λ _d based on the wavelength temperature characteristic and wavelength current characteristic of the light source 1 measured in advance.

  Light from the light source 1 is branched into output light and controlled light by the half mirror 2, and the controlled light is further branched by the beam splitter 3. The light transmitted through the light splitting surface on the lower side of FIG. 1 of the beam splitter 3 passes through the wavelength discriminator 4 and is detected by the detector 60 as a wavelength discrimination signal. The light reflected from the lower light splitting surface of the beam splitter 3 and transmitted through the upper light splitting surface is detected by the first detector 50 as a light intensity signal. The light reflected from the lower light splitting surface of the beam splitter 3 and reflected from the upper light splitting surface is detected by the second detector 51 as a light intensity signal. The upper light splitting surface and the lower light splitting surface are made of dielectric multilayer films having the same configuration, and the reflectance and transmittance and their change states are also the same.

The intensity of light from the light source 1 is I _o , the transmittance of the half mirror 2 is T ₂ , the reflectance of the beam splitter 3 is R ₃ , the transmittance of the beam splitter 3 is T ₃ = 1−R ₃ , and the reference wavelength λ _d is The reference transmittance of the wavelength discriminator 4 is _Td . Here, the intensity of light incident on the detector is obtained in consideration of the reflectance change ΔR ₃ of the beam splitter. Considering the change in reflectance, the reflectance of the beam splitter 3 is (R ₃ + ΔR ₃ ), and the transmittance of the beam splitter 3 is (T ₃ = 1−R ₃ −ΔR ₃ ). Assuming that the transmittance change of the wavelength discriminator 4 due to the wavelength difference Δλ from the reference wavelength λ _d is ΔT _d , the intensities I ₅₀ , I ₅₁ and I ₆₀ of the light incident on the detectors ₅₀ , ₅₁ and ₆₀ are expressed by the following equations: From (6) to (8).

The light intensities I ₅₀ and I ₅₁ detected by the detectors ₅₀ and ₅₁ are converted into voltage signals V ₅₀ and V ₅₁ by the respective detectors. The voltage signal output from each detector is input to the miscalculation signal calculator 8. Obtained from the second detector by the error signal computing unit 8 (the detector 50 and the detector 51) the light intensity is detected by the signal V _i following equation (9).

The light intensity I ₆₀ detected by the detector ₆₀ is converted into a voltage signal V ₆₀ . The error signal E is obtained from the following equation (10) by the error signal calculator 8 with the wavelength discrimination signal V _w = V ₆₀ .

  From Expression (6) to Expression (9), Expression (10) becomes the following Expression (11).

From equation (11), it can be seen that the error signal E in the first embodiment is proportional to the transmittance change ΔT _d due to the wavelength difference Δλ and is not affected by the light intensity I _o of the light source 1. Further, it can be seen that the error signal E is not affected by the change ΔR _{3 in} the reflectivity of the beam splitter 3 (optical element). That is, from the equations (6) to (9), both the light intensity signal V _i and the wavelength discrimination signal V _w are affected by the same effect as once passing through the optical branching device. Therefore, according to the equation (10), the influence due to the change in reflectance and transmittance of the beam splitter 3 is canceled, and an error signal that is not affected by the change in reflectance can be obtained even when the reflectance changes. Using this error signal, the control unit 9 controls the wavelength of light from the light source.

  As described above, since the detector 50 and the detector 51 are used as the second detection unit that detects light that does not pass through the wavelength reference unit, the influence of the change in the reflectance and transmittance of the beam splitter 3 is negated. The wavelength of the light from can be stabilized with higher accuracy than before.

(Second Embodiment)
FIG. 2 shows a light source device 200 according to the second embodiment.

  In the light source device 200 of the second embodiment, it is assumed that the beam splitter 3 is formed by bonding two right-angle prisms. The light beam reflected by the beam splitter 3 is folded back by the shift mirror 70, thereby simplifying the configuration of the beam splitter 3 (optical element) compared to the first embodiment.

  The shift mirror 70 is a right-angle prism made of optical glass such as BK7. The shift mirror 70 is disposed so that the incident surface (the oblique side of the right triangle) is perpendicular to the light beam reflected from the beam splitter 3.

  When a 45-degree right angle prism is used as the shift mirror 70, the incident light is incident on two sides forming a right angle at an incident angle of 45 degrees. If the distance between the right vertex and the reflection point of the light beam is d, the light incident on the shift mirror 70 rotates 180 degrees, and the light shifted by Sqrt (2) × d is incident on the beam splitter 3 again.

The refractive index n _{med in} the 1.5 μm band of the optical glass such as BK7 is about 1.50, and the critical angle θ = Asin (n _air / n _med ) = 43.5 degrees at the boundary with _air . In general, it is easy to suppress the angle change of the optical axis to 1 degree or less. Further, since the temperature coefficient of the refractive index of the optical glass is about 1E-5, the critical angle change due to the temperature change is 1.2 seconds / ° C. and is extremely small. Therefore, the shift mirror 70 is a mirror having extremely stable reflection characteristics using total reflection, and the reflectance at the shift mirror 70 need not be taken into consideration.

Therefore, the light detected by the detector 50 of the second embodiment is the light reflected and transmitted by the beam splitter 3 as in the first embodiment. Similarly, the light detected by the detector 51 is light reflected by the beam splitter 3 and reflected again, as in the first embodiment. Since the reflectance at the shift mirror 70 does not need to be considered, the intensity I ₅₀ of light incident on the detector 50 can be expressed by the above equation (6), and the intensity of light incident on the detector 51. I ₅₁ can be represented by the above formula (7).

The light transmitted through the beam splitter 3 passes through the wavelength discriminator 4 and is detected by the detector 60. The intensity I ₆₀ of the light incident on the detector 60 can be expressed by the above equation (8).

  From the above, it is understood that the equations (9) to (11) described in the first embodiment can also be applied to the light source device 200, and the error signal is not affected by the change in the reflectance of the beam splitter 3. .

  As described above, by using the detector 50 and the detector 51 as the second detection unit that detects light that does not pass through the wavelength reference unit, the wavelength of light from the light source can be stabilized with higher accuracy than in the past. . Furthermore, the structure of the beam splitter 3 (optical element) can be simplified by using a shift mirror.

(Third embodiment)
FIG. 3 shows a light source device 300 according to the third embodiment.

  The light source device 300 includes a light source 1, a half mirror 2 (branching device), a beam splitter 3 (optical element), a wavelength discriminator 4, detectors 50 and 60, shift mirrors 70 and 71, and an error signal calculator. 8, a control unit 9, and an output unit 10.

  In the light source device 300 of the third embodiment, it is assumed that the beam splitter 3 is formed by bonding two right-angle prisms. The light beam reflected by the beam splitter 3 is folded back by the shift mirror 70 as in the second embodiment. Furthermore, in this embodiment, it has the shift mirror 71 which returns the light which passed the wavelength discriminator 4 to a wavelength discriminator. On the other hand, the second detection unit that detects light that does not pass through the wavelength reference unit includes a detector 50. In this embodiment, the error signal calculator 8 obtains the error signal E from the detection results of the detector 50 (second detection unit) and the detector 60 (first detection unit).

  Next, an operation principle of stabilizing the wavelength of light from the light source 1 in the third embodiment will be described. The operation at the start of wavelength stabilization is the same as that of the first embodiment, and the light source 1 is adjusted to the operating temperature by the control unit 9 and at the same time started up with the initial drive current.

  Light from the light source 1 is branched into output light and controlled light by the half mirror 2, and the controlled light is further branched by the beam splitter 3. The light reflected by the beam splitter 3 is turned by the shift mirror 70 after the optical path is shifted, then passes through the beam splitter 3 and is guided to the detector 50 for detecting the intensity signal of the light. On the other hand, the light that has passed through the beam splitter 3 passes through the wavelength discriminator 4, shifts the optical path by the shift mirror 71 and is turned back, and then passes through the wavelength discriminator 4 again. The light that has passed through the wavelength discriminator 4 is reflected by the beam splitter 3 and guided to a detector 60 for detecting a wavelength discrimination signal.

The intensity of light from the light source 1 is I _o , the transmittance of the half mirror 2 is T ₂ , the reflectance of the beam splitter 3 is R ₃ , the transmittance of the beam splitter 3 is T ₃ = 1−R ₃ , and the reference wavelength λ _d is _Let T _{d be} the reference transmittance of the wavelength discriminator 4. Further, assuming that the change in transmittance of the wavelength discriminator 4 due to the wavelength difference Δλ from the reference wavelength λ _d is ΔT _d and the reflectivity of the boundary surfaces of the shift mirrors 70 and 71 are R ₇₀ and R ₇₁ , the detectors 50 and 60 are sent. Intensities I ₅₀ and I ₆₀ of incident light are expressed by the following equations (12) and (13).

The light intensity I ₅₀ detected by the detector ₅₀ is converted into a voltage signal V ₅₀ . Similarly, the light intensity I ₆₀ detected by the detector ₆₀ is converted into a voltage signal V ₆₀ . The error signal E is obtained from the following equation (14) by the error signal calculator 8 with the light intensity signal V _i = V ₅₀ and the wavelength discrimination signal V _w = V ₆₀ .

  From Expression (12) and Expression (13), Expression (14) becomes the following Expression (15).

As in the second embodiment, since the reflection by the shift mirrors 70 and 71 is total reflection, the reflectance of the shift mirror need not be considered. Error signal E of the formula _(15), and _R 70 ₌ R _{71 =} 1, if the [Delta] T _d << T _d, and comprising the following formula (16).

From equation (16), the error signal E in the third embodiment is proportional to the transmittance change ΔT _d due to the wavelength difference Δλ and is not affected by the change in the light intensity I _o from the light source 1. Furthermore, it can be seen that not affected by the change [Delta] R ₃ in the reflectivity of the beam splitter 3.

From the equations (12) and (13), the intensity signal V _i and the wavelength discrimination signal V _w are both detected by detecting light including light once transmitted through the beam splitter 3 and once reflected by the light from the light source. It turns out that it is what was demanded. Therefore, according to the equation (14), the influence due to the change in the reflectance and transmittance of the beam splitter 3 is canceled, and even when the reflectance of the beam splitter 3 changes, the error signal can be calculated without being affected by the influence. . Using this error signal, the control unit 9 controls the wavelength of light from the light source.

As shown in FIG. 3, the wavelength discriminator 4 may not be disposed between the beam splitter 3 and the shift mirror 71 but may be disposed between the beam splitter 3 and the detector 60. . Also in this case, the intensity I ₆₀ of light detected by the detector ₆₀ is the same as that in the equation (13).

  As described above, the first detection unit that detects light that passes through the wavelength reference unit and the second detection unit that detects light that does not pass through the wavelength reference unit include light transmitted through the beam splitter 3, reflected light, and the like. By detecting the light containing, the wavelength of light from the light source can be stabilized with higher accuracy than before. Furthermore, by using a shift mirror in the optical path for detecting the wavelength discrimination signal, the number of detectors can be reduced with respect to the second detectors of the first embodiment and the second embodiment.

(Fourth embodiment)
FIG. 6 is a diagram showing a measuring apparatus 600 according to the fourth embodiment.

  The measuring device 600 is a light wave interference measuring device that measures the distance between the reference surface 61 and the test surface 62. The measuring device 600 includes a light source device 100, a polarization beam splitter 63, an interference light detection unit 64, a calculation unit 65, a λ / 2 plate 67, and a λ / 4 plate 68. The light source device is not limited to the light source device 100 described in the first embodiment, and the light source device of any of the above-described embodiments can be applied.

  Light from the output unit 10 of the light source device 100 enters an interference optical system 66 including a polarization beam splitter 63. The λ / 2 plate rotates the polarized light so that the polarization beam splitter 63 has an appropriate branching ratio. The polarization beam splitter 63 divides the light from the light source device 100 into two lights, causes the reflected light to enter the reference surface 61, and causes the transmitted light to enter the test surface 62. The light reflected by the reference surface 61 (reference light) is rotated in the polarization direction by the λ / 4 plate 68, and then passes through the polarization beam splitter 63 and enters the interference light detector 64. The light reflected by the test surface 62 (test light) is rotated in the polarization direction by the λ / 4 plate 68, then reflected by the polarization beam splitter 63 and incident on the interference light detection unit 64. Thereby, interference light between the reference light and the test light is generated, and the interference light detection unit 64 detects the interference light. The calculation unit 65 obtains the distance between the reference surface 61 and the test surface 62 based on the interference light detected by the interference light detection unit 64.

  Further, the measurement device 600 can be used as a shape measurement device by using the interference light detection unit 64 as a two-dimensional sensor and enlarging the light from the output unit 10 with a beam expander (not shown).

  In the measurement apparatus 600 of this embodiment, the wavelength of light from the light source apparatus 100 is stabilized. Therefore, the measuring device 600 can measure the interval between the reference surface 61 and the test surface 62 with high accuracy. Moreover, if the shape of a test object (an optical member or a mechanical member) is measured using these measurement devices (shape measurement devices) and the test object is processed based on the measurement result, highly accurate processing can be performed. .

  The light source device of the present invention is not only used in a measuring device that measures the distance between the reference surface and the test surface, but also is a light source device for realizing an optical wavelength division multiplexing optical communication system in the communication field (outputted). The present invention can also be applied as a light source in which the wavelength of light is stabilized with high accuracy.

  In any of the embodiments, the case where the error signal calculator 8 obtains the transmittance of the light transmitted through the wavelength discriminator 4 has been described. However, it is not always necessary to obtain the light transmittance. For example, when the change rate of the light intensity with respect to the wavelength change is known, the light source 1 may be controlled by obtaining the wavelength difference Δλ from the light intensity change from the reference wavelength.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

1 Light source 2 Half mirror
3 Beam splitter (optical element)
4 Wavelength Discriminator 50 Detector 51 Detector 60 Detector 8 Error Signal Calculator 9 Control Unit

Claims (11)

A light source;
A wavelength reference unit that changes the intensity of light from the light source according to a change in wavelength of light from the light source;
A first detection unit for detecting the intensity of light passing through the wavelength reference unit;
A second detection unit that detects the intensity of light that does not pass through the wavelength reference unit;
An optical element that divides light from the light source into light incident on the first detection unit and light incident on the second detection unit by a light splitting surface;
A calculation unit that obtains a wavelength change of light from the light source that has passed through the wavelength reference unit using the light intensity detected by the first detection unit and the light intensity detected by the second detection unit;
Based on the wavelength change obtained by the arithmetic unit, a control unit for controlling the wavelength of light from the light source,
A light source device comprising:
The second detection unit detects a light intensity transmitted through the light splitting surface or another light splitting surface having the same configuration as the light splitting surface, and reflects the light splitting surface or the other light splitting surface. A light source device comprising a detector for detecting the intensity of the emitted light. A light source;
A wavelength reference unit that changes the intensity of light from the light source according to a change in wavelength of light from the light source;
A first detection unit for detecting the intensity of light passing through the wavelength reference unit;
A second detection unit that detects the intensity of light that does not pass through the wavelength reference unit;
An optical element that divides light from the light source into light incident on the first detection unit and light incident on the second detection unit by a light splitting surface;
A calculation unit that obtains a wavelength change of light from the light source that has passed through the wavelength reference unit using the light intensity detected by the first detection unit and the light intensity detected by the second detection unit;
Based on the wavelength change obtained by the arithmetic unit, a control unit for controlling the wavelength of light from the light source,
A light source device comprising:
The light source device, wherein light incident on the first detection unit and light incident on the second detection unit are transmitted through the light dividing surface and reflected by the light dividing surface.   3. The light source device according to claim 1, wherein the optical element is a beam splitter on which a reflection film that divides light from the light source into transmitted light and reflected light is formed. 4.   4. The light source device according to claim 1, further comprising a prism that totally reflects the light transmitted through the optical element and turns it back into the optical element. 5.   5. The light source device according to claim 1, further comprising a prism that totally reflects the light reflected by the optical element and returns the light to the optical element again. 6. The wavelength reference unit is composed of a gas cell,
6. The light source device according to claim 1, wherein the calculation unit obtains a wavelength change of light from the light source using light transmitted through the gas cell. 7. A light source;
A wavelength reference unit that changes the intensity of light from the light source according to a change in wavelength of light from the light source;
A first detection unit for detecting the intensity of light passing through the wavelength reference unit;
A second detection unit that detects the intensity of light that does not pass through the wavelength reference unit;
An optical element that divides light from the light source into light incident on the first detection unit and light incident on the second detection unit by a light splitting surface;
A calculation unit that obtains a wavelength change of light from the light source that has passed through the wavelength reference unit using the light intensity detected by the first detection unit and the light intensity detected by the second detection unit;
Based on the wavelength change obtained by the arithmetic unit, a control unit for controlling the wavelength of light from the light source,
A light source device comprising:
The second detection unit detects the intensity of the light split into the light incident on the second detection unit by the light splitting surface and transmitted through another light splitting surface having the same configuration as the light splitting surface. A light source device comprising: a detector; and a detector that detects the intensity of light reflected from the other light splitting surface. A light source;
A wavelength reference unit that changes the intensity of light from the light source according to a change in wavelength of light from the light source;
A first detection unit for detecting the intensity of light passing through the wavelength reference unit;
A second detection unit that detects the intensity of light that does not pass through the wavelength reference unit;
An optical element that divides light from the light source into light incident on the first detection unit and light incident on the second detection unit by a light splitting surface;
A prism that totally reflects the light split into the light incident on the second detection unit by the light splitting surface and turns it back into the optical element;
A calculation unit that obtains a wavelength change of light from the light source that has passed through the wavelength reference unit using the light intensity detected by the first detection unit and the light intensity detected by the second detection unit;
Based on the wavelength change obtained by the arithmetic unit, a control unit for controlling the wavelength of light from the light source,
A light source device comprising:
The second detection unit detects a light intensity of light incident on the optical element by the prism and detecting the intensity of light transmitted through the light splitting surface, and detects the intensity of light reflected from the light splitting surface. A light source device comprising a detector. A control method for controlling a light source device having a wavelength reference unit that changes the intensity of light from the light source according to a change in wavelength of light from the light source,
Using the light intensity detected by the first detection unit that detects the intensity of light that passes through the wavelength reference unit and the light intensity detected by the second detection unit that detects the intensity of light that does not pass through the wavelength reference unit A calculation step for obtaining a wavelength change of light from the light source that has passed through the wavelength reference unit;
A control step for controlling the wavelength of light from the light source based on the wavelength change obtained in the calculation step;
A control method comprising:
The light source device has an optical element that divides light from the light source into light incident on the first detection unit and light incident on the second detection unit by a light dividing surface,
The second detection unit includes a detector that detects the intensity of light transmitted through the light splitting surface or another light splitting surface having the same configuration as the light splitting surface, and the light splitting surface or the other light splitting surface. A control method comprising a detector for detecting the intensity of reflected light. A control method for controlling a light source device having a wavelength reference unit that changes the intensity of light from the light source according to a change in wavelength of light from the light source,
Using the light intensity detected by the first detection unit that detects the intensity of light that passes through the wavelength reference unit and the light intensity detected by the second detection unit that detects the intensity of light that does not pass through the wavelength reference unit A calculation step for obtaining a wavelength change of light from the light source that has passed through the wavelength reference unit;
A control step for controlling the wavelength of light from the light source based on the wavelength change obtained in the calculation step;
A control method comprising:
The light source device has an optical element that divides light from the light source into light incident on the first detection unit and light incident on the second detection unit by a light dividing surface,
The control method characterized in that light incident on the first detector and light incident on the second detector are transmitted through the light dividing surface and reflected from the light dividing surface. A shape measuring device that measures the shape of the test object by measuring the distance between the reference surface and the surface of the test object,
The light source device according to any one of claims 1 to 8,
The light from the light source device is divided into two lights, one light is made incident on the reference surface, the other light is made incident on the surface of the test object, the light from the reference surface and the test object An optical system that generates interference light with light from the surface of the object;
An interference light detector for detecting the interference light;
A calculation unit that calculates a distance between the reference surface and the surface of the test object based on the interference light detected by the interference light detection unit;
A shape measuring device characterized by comprising:

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