JP2006324636A - Method for detecting laser oscillation wavelength, control method, and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser oscillation wavelength control method which is suitable for detecting the oscillation wavelength of an emission beam from a laser element and controlling the oscillation wavelength with high definition. <P>SOLUTION: The laser beam to be emitted from the one laser element is received by respectively using the two light receiving means which are mutually different in wavelength response characteristic. The beam receiving amounts by the respective light receiving means are mutually compared so as to detect the oscillation wavelength of the laser beam. Specifically, the emission beam from the laser element is received via a wavelength selectable optical filter. The driving electric current of the laser element is varied in response to the beam receiving amounts so as to control the oscillation wavelength. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laser oscillation wavelength detection method, a control method, and an apparatus suitable for detecting an oscillation wavelength of laser light that is output after being wavelength-modulated from a laser element with high accuracy, and for controlling the oscillation wavelength.

  One of optical state detection techniques uses a self-coupling effect (also referred to as a self-mixing effect) of laser light (see, for example, Patent Documents 1 and 2). As shown in FIG. 8, this technique irradiates a laser beam to a measurement object 2 from a laser element (hereinafter referred to as LD) 1 driven using a predetermined modulation signal, and reflects the laser beam reflected by the measurement object 2. The irradiation light on which the interference signal generated by the self-coupling effect between the reflected light returning to the element 1 and the irradiation light is superimposed is received by a light receiver (hereinafter referred to as PD) 3 and the output thereof is subjected to frequency analysis or the like. The state of the measurement object 2 is detected.

  That is, when the oscillation wavelength of the output light from the laser element 1 is continuously changed, the return light reflected by the detection target 2 and the output light of the laser element 1 interfere with each other, and the laser is used at a wavelength that satisfies the resonance condition. The amplification efficiency of the element 1 is slightly increased, and the amplification efficiency is slightly decreased at a wavelength satisfying the attenuation condition. As a result, the output of the light receiver 3 repeatedly increases and decreases. For example, if a semiconductor laser device whose type changes the oscillation wavelength of the laser light according to the applied current value is wavelength-modulated using a triangular wave α whose current value changes over time, the current value will increase continuously. Accordingly, the wavelength of the laser light continuously increases, and the wavelength of the laser light continuously decreases as the current value continuously decreases after the current value reaches the peak.

In this way, while the wavelength of the laser light continuously increases and decreases, the resonance condition and the attenuation condition between the irradiation light and the return light (reflected light) are satisfied many times. As a result, a beat waveform (modulated light) β in which a minute interference component is superimposed on the triangular wave α is obtained from the light receiver 3. This interference component includes information such as the distance L between the laser element 1 and the detection target 2. Therefore, if this beat waveform β is analyzed, it is possible to detect the state such as the distance L, speed, vibration, etc. from the frequency of the resonance component to the object 2. For example, it is possible to detect the state of the measurement object by differentiating the beat waveform β and extracting a signal component superimposed on the triangular wave α and counting the signal component.
JP 10-246782 A JP-A-11-287859

  Incidentally, the intensity (light quantity) P of the output light from the laser element 1 varies with the drive current I, and the oscillation wavelength λ also varies with the drive current I. That is, a slight thermal expansion / contraction occurs in the laser element 1 due to the increase / decrease of the drive current I, and the oscillation wavelength λ of the laser light slightly increases / decreases accordingly. Therefore, in general, for example, the output light from the laser element 1 is received by a light receiver (photodiode), the intensity (light quantity) P is monitored, and the drive current I is varied according to the received light quantity P. Thus, the oscillation wavelength λ is controlled.

  However, since the intensity (light quantity) P and the oscillation wavelength λ of the output light from the laser element 1 also change depending on the temperature T of the laser element 1, the temperature T of the laser element 1 is also required to accurately control the oscillation wavelength λ. It is necessary to monitor. Moreover, since it is necessary to control the drive current I according to the intensity (light quantity) P of the output light and the temperature T of the laser element 1, it is unavoidable that the control system becomes complicated. In the mass produced laser element 1, it cannot be denied that the relationship between the intensity P of the output light and the oscillation wavelength λ varies for each individual. Such a variation in the above-mentioned characteristics for each individual is an obstacle to controlling the oscillation wavelength λ of the laser element 1 with high accuracy.

The present invention has been made in view of such circumstances, and the object of the present invention is to provide a laser oscillation wavelength detection method capable of easily and accurately detecting the oscillation wavelength of laser light output from a laser element. It is to provide.
Another object of the present invention is to provide laser oscillation wavelength control that can detect the oscillation wavelength of laser light that is output after being wavelength-modulated from a laser element with high accuracy and can effectively correct the deviation of the oscillation wavelength. It is to provide a method.

  Another object of the present invention is to provide a laser oscillation wavelength control device that can stably output a wavelength-modulated laser beam from a laser element.

In order to achieve the above-described object, a laser oscillation wavelength detection method according to the present invention receives laser beams output from one laser element using two light receiving means having different wavelength response characteristics, and each of the light receiving means. The amount of received light is compared with each other to detect the oscillation wavelength of the laser beam [Claim 1].
Preferably, at least one of the light receiving means includes an optical filter having a known wavelength response characteristic and a light receiving element that receives the laser light through the optical filter. The laser element changes the wavelength of the laser light with time.

In another laser oscillation wavelength detection method according to the present invention, the wavelength of the laser beam output from the laser element is changed over time, and the laser beam is received using a light receiving means having a known wavelength response characteristic. In addition, the oscillation wavelength of the laser beam is detected by comparing the amount of light received by the light receiving means with a light receiving characteristic assumed in advance of the light receiving means [Claim 3].
Preferably, the light receiving means includes an optical filter having a known wavelength response and a light receiving element that receives the laser light through the optical filter. The light receiving characteristics of the light receiving means are estimated from changes in the amount of light received by the light receiving means when, for example, the oscillation wavelength of the laser light is changed over a predetermined bandwidth.

  On the other hand, the laser oscillation wavelength control method according to the present invention detects the oscillation wavelength of the laser beam output from the laser element using the laser wavelength detection method described above, and based on the detected wavelength information of the laser beam, the laser The present invention is characterized in that the oscillation wavelength of light is feedback-controlled [Claim 7]. Incidentally, the feedback control of the oscillation wavelength of the laser beam may be performed, for example, by feedback control of a drive current for driving the laser element to oscillate.

  The laser oscillation wavelength control device according to the present invention has a wavelength response characteristic different from that of a semiconductor laser element and a driving means for supplying a driving current to the semiconductor laser element to oscillate and output laser light from the semiconductor laser element. Two light receiving means for receiving the laser beams output from the semiconductor laser element, a wavelength detecting means for detecting the oscillation wavelength of the laser light by comparing the amounts of light received by the respective light receiving means with each other, and this wavelength Wavelength control means for adjusting the drive current based on wavelength information of the laser light detected by the detection means to feedback control the oscillation wavelength of the laser light is provided [claim 9].

  Preferably, the driving unit is configured to change a driving current of the laser element and change an oscillation wavelength of laser light output from the laser element over time over a predetermined band. At least one includes an optical filter having a known wavelength response characteristic and a light receiving element that receives the laser light through the optical filter. The wavelength control means obtains a deviation between the oscillation wavelength of the laser beam detected by the wavelength detection means and a theoretical oscillation wavelength determined by the driving current of the laser element, and corrects the deviation of the wavelength. Further, it is configured to control the drive current of the laser element.

  Further, another laser oscillation wavelength control device according to the present invention includes a semiconductor laser element that outputs laser light, and a drive unit that changes the wavelength of the laser light with time by changing the drive current of the semiconductor laser element, A light receiving means for receiving a laser beam having a known wavelength response characteristic and outputted from the semiconductor laser element, and comparing the amount of light received by the light receiving means with a light receiving characteristic of the light receiving means assumed in advance. Wavelength detecting means for detecting the oscillation wavelength of light, and wavelength control means for feedback-controlling the oscillation wavelength of the laser light by adjusting the drive current based on the wavelength information of the laser light detected by the wavelength detecting means; (Claim 11).

  Preferably, the light receiving means includes an optical filter having a known wavelength responsiveness and a light receiving element that receives the laser light through the optical filter, and the wavelength detecting means oscillates the laser light. The light receiving characteristic of the light receiving means is estimated from the change in the amount of light received by the light receiving element when the wavelength is changed over a predetermined bandwidth, and is used for wavelength detection.

  According to the laser oscillation wavelength control method of the present invention, when the laser beam output from the laser element is received using the light receiving means having a certain wavelength response characteristic, the amount of received light changes depending on the oscillation wavelength of the laser beam. Therefore, the oscillation wavelength of the laser beam can be detected with high accuracy by the simple method described above. Then, by adjusting the drive current applied to the laser element based on the detection result (oscillation wavelength information), the oscillation wavelength of the laser beam output from the laser element can be controlled with high accuracy.

  Therefore, while changing the oscillation wavelength of the laser light output from the laser element over a predetermined band, for example, the output light is irradiated onto the measurement object, and the reflected light (return light) is reinjected into the laser element. If this is applied to a state detection device or a laser length measuring device that generates a self-coupling effect in the laser element and detects the state of the measurement object from the modulated laser light generated thereby, it can be varied over the predetermined band. Since the oscillation wavelength of the output light can be stabilized, it is possible to achieve a great practical effect such as an increase in detection accuracy.

Hereinafter, a laser oscillation wavelength detection method, a wavelength control method thereof, and a wavelength control device according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of a main part of a laser device configured by applying a laser oscillation wavelength detection method and a wavelength control method according to a first embodiment of the present invention. Reference numeral 10 denotes a laser element (laser diode LD). , 20 is the drive circuit.

  As shown in the characteristic diagram A of FIG. 2, the laser element 10 represents a monochromatic laser beam having a steep mountain-shaped wavelength distribution having a bandwidth w of several nm (hereinafter, this wavelength distribution is represented by its center wavelength λ, Is called an oscillation wavelength λ of laser light). The oscillation wavelength λ of this laser light (output light) is in the range of the fluctuation region R (λmin to λmax) as shown in the characteristic diagram B of FIG. 2, for example, according to the drive current I (Imin to Imax) of the laser element 10. It changes with. The laser beam output from the laser element 10 is irradiated to a measurement object (not shown) via, for example, the condenser lens 11 and used for distance measurement to the measurement object.

  A transmissive optical filter 12 having a predetermined wavelength selectivity is provided between the condenser lens 11 described above and the output light emitting end face of the laser element 10. The optical filter 12 is composed of, for example, a bandpass filter (bandpass filter) showing a narrow wavelength selectivity with respect to the above-described fluctuation region R of the oscillation wavelength λ of the laser light. This type of optical filter 12 is a transmission type that is generally commercially available, and the light absorption characteristics of a transparent body such as glass exhibit bandpass wavelength selectivity.

  Further, the laser device is provided with a first light receiving element (photodiode PD1) 13 and a second light receiving element (photodiode PD2) 14 with the optical filter 12 therebetween. These light receiving elements 13 and 14 preferably each have a flat light receiving characteristic in a sufficiently wide wavelength band including the fluctuation region R of the center wavelength λ of the laser light to be received. That is, it is desirable that the light receiving elements 13 and 14 have a characteristic of obtaining the same output with respect to incident light having the same intensity regardless of the wavelength. Further, it is desirable that these light receiving elements 13 and 14 have output characteristics proportional to the intensity (amount of received light) of the received laser beam. More specifically, as each of the light receiving elements 13 and 14, it is desirable to use products having the same specifications and having the same characteristics.

  Even if each of the light receiving elements 13 and 14 does not have the above-described desirable light receiving characteristics or the characteristics are not uniform, it is possible to use the light receiving characteristics by optimizing the light receiving characteristics as appropriate. It goes without saying that it is possible. As a matter of course, it is desirable that the optical filter 12 and the light receiving elements 13 and 14 are more stable than the light emitting element 10 with respect to environmental changes and deterioration over time.

  By the way, the first light receiving element 13 described above is provided so as to receive the laser light (output light) output from the laser element 10 directly or indirectly, and two light receiving means provided in parallel are provided. One of the light receiving means is configured. The second light receiving element 14 is provided so as to receive the output light output from the laser element 10 and passing through the optical filter 12. That is, the optical filter 12 and the second light receiving element 14 constitute the other light receiving means of the two light receiving means described above. Information on the received light amounts Q1 and Q2 detected by the light receiving elements 13 and 14 is input to the drive circuit 20 as information for controlling the oscillation wavelength λ of the laser element 1. ing.

  On the other hand, the drive circuit 20 described above basically supplies a drive current I to the laser element 10 to drive the laser element 10 to oscillate, and the current drive source 21 includes the above-described triangular wave or sawtooth shape. For example, as shown in FIG. 2, a modulation circuit 22 that periodically increases or decreases the drive current I in the range of (Imin to Imax) is provided. The oscillation wavelength λ of the laser element 10 changes as shown by the characteristics A and B in FIG. 2 by the drive current I that is controlled to increase or decrease in this way, and its output intensity (light emission amount) P and light reception amount Q are Change.

  The drive circuit 20 receives the received light amounts Q1 and Q2 detected by the light receiving elements 13 and 14, that is, the intensity Q1 of the laser light output from the laser element 10 and the output light transmitted through the optical filter 12, respectively. A wavelength detection circuit 23 for detecting the oscillation wavelength of the output light from the intensity Q2 and a drive current I for the laser element 10 are corrected according to the detected wavelength, thereby correcting a shift in the oscillation wavelength of the laser light. And a correction circuit 24. The drive circuit 20 controls the oscillation wavelength λ of the output light (laser light) oscillated and output from the laser element 10 by adjusting the drive current I according to the wavelength shift, and corrects the shift. It has become.

Here, the detection of the oscillation wavelength λ of the laser light based on the intensity (light reception amount) Q1 of the laser light output from the laser element 10 and the intensity (light reception amount) Q2 of the laser light transmitted through the optical filter 12 is performed. (Laser wavelength detection method according to the present invention) will be described.
Since the intensity of the laser light (output light) oscillated and output by the laser element 10 changes according to the drive current I, the amount of light received Q1 by the first light receiving element 13 that directly receives the output light is, for example, FIG. As shown by the solid line in the characteristic diagram B of FIG. Further, since the oscillation wavelength λ of the output light oscillated and output by the laser element 10 also changes in accordance with the drive current I of the laser element 10, the change in the amount of received light Q1 by the light receiving element 13 also represents the change in the oscillation wavelength λ. It can be said that.

  On the other hand, the laser beam received by the second light receiving element 14 via the optical filter 12 is affected by the optical characteristics of the optical filter 12. Therefore, when the optical filter 12 has a band-pass filter characteristic that transmits a component in a predetermined wavelength band, the amount of light received Q2 by the second light receiving element 14 changes as indicated by a broken line in the characteristic diagram B of FIG. That is, the laser light of the wavelength component in the transmission wavelength band of the optical filter 12 is transmitted as it is regardless of the presence of the optical filter 12, and the laser light of the wavelength component other than the above wavelength band (attenuation band) is greatly attenuated by the optical filter 12. Therefore, the second light receiving element 14 mainly receives only the laser beam having the predetermined wavelength band. Therefore, the received light amount ratio L (= Q2 / Q1), which is the ratio of the received light amounts Q1 and Q2, indicates the optical characteristics (selectivity of transmission wavelength) of the optical filter 12 itself as shown in the characteristic diagram C of FIG. Will be.

  Therefore, if the received light amount ratio Lmin corresponding to the wavelength λmin in the short wavelength side attenuation band and the received light amount ratio Lmax corresponding to the wavelength λmax in the long wavelength side attenuation band are respectively obtained, these received light amount ratios Lmin, Lmax and the optical The deviation (amount and direction) of the oscillation wavelength λ can be detected from the transmittance characteristics of the filter 12. For example, when the wavelength λ of the laser beam is shifted to the short wavelength side as a whole, the value of the received light amount ratio Lmin decreases and the value of the received light amount ratio Lmax increases. Conversely, when the wavelength λ of the laser beam is shifted to the longer wavelength side as a whole, the value of the received light amount ratio Lmin increases, and the value of the received light amount ratio Lmax decreases. Since the characteristic curve of the received light amount ratio L, which is the transmittance characteristic of the optical filter 12, is known, the shift amount Δλ of the wavelengths λmin and λmax can be detected from the shift amount of the received light amount ratios Lmin and Lmax.

  In general, the relationship [L × (P2 / P1)] between the light reception amount ratio L of the optical filter 12 and the light reception characteristic P2 of the light receiver 14 and the light reception characteristic P1 of the light receiver 13 is a function f (λ ), The oscillation wavelength λ of the laser beam can be measured from these relationships. However, since wavelength control cannot be performed in the region where the slope of the function f (λ) is [0], the wavelength control condition is that the slope of the function f (λ) is not [0].

  Therefore, if the drive current I of the laser element 10 is adjusted according to the wavelength shift amount Δλ detected as described above, the oscillation wavelength λ of the laser element 10 can be corrected thereby. In other words, the oscillation wavelength of the laser element 10 can be controlled with high accuracy by adjusting the drive current I according to the wavelength shift amount Δλ. Therefore, the laser beam oscillated and output by the laser element 10 is received through the optical filter 12, and the deviation of the oscillation wavelength λ is detected only by examining the amount of light received when the laser element 10 is driven to oscillate with the specific drive current I. It is possible to obtain easily and correct the deviation effectively.

  In the above-described embodiment, for the sake of simplicity of explanation, the maximum value Lmax and the minimum value Lmin of the transmittance corresponding to the maximum value Imax and the minimum value Imin of the drive current I have been described as detection targets. It is not limited. That is, it is sufficient that the received light amount ratio L with respect to the predetermined drive current value I is a detection target. In the above-described embodiment, the first light receiving element (PD1) 13 directly receives the laser beam output from the laser element 10. However, another optical filter (not shown) is used as the laser. In addition to the element 10 and the light receiving element 13, the first light receiving element 13 may be configured to receive the laser beam output from the laser element 10 through the optical filter. In this case, it goes without saying that an optical filter having a wavelength response (selectivity of transmission wavelength) different from that of the optical filter 12 is used as the additional optical filter.

  By the way, in the above-described embodiment, the respective intensities (light reception amounts) of the laser light before passing through the optical filter 12 and the laser light after passing through the optical filter 12 are respectively obtained, and the ratio of the light reception amounts Q1 and Q2 (light reception amount ratio). Focusing on L), the shift of the oscillation wavelength λ was detected. However, if the light receiving element 13 has stable performance with respect to environmental changes and aging deterioration, for example, as shown in FIG. 3, the intensity (light receiving amount) of the laser light after passing through the optical filter 12 is set to the second light receiving element. The shift of the oscillation wavelength can be obtained in the same manner simply by detecting at 14.

  That is, by changing the drive current I of the laser element 10, the oscillation wavelength λ is continuous over a predetermined wavelength range (however, including at least part of the attenuation band on the short wavelength side and the long wavelength side of the optical filter 12). The amount of light received through the optical filter 12 at that time is obtained. Then, as shown in FIG. 4, in the wavelength transmission band of the optical filter 12, the intensity of the laser light that is not affected by the optical characteristics of the optical filter 12, that is, the intensity of the laser light output from the laser element 10 is detected. can do. Therefore, from the intensity change in this band, the change in the output intensity of the laser beam with respect to the oscillation wavelength λ of the laser element 10 can be estimated as shown by the one-dot chain line in FIG.

  Even if the output characteristics of the laser element 10 are not estimated in this way, if the oscillation output characteristics are examined in advance, for example, in a shipping inspection of the laser element 10, the light is received via the output filter and the optical filter 12. The deviation of the oscillation wavelength can be obtained from the intensity of the laser beam (the amount of received light) according to the amount of received light when the laser element 10 is driven to oscillate with the current I as described above. Therefore, the oscillation wavelength λ of the laser element 10 can be controlled with high accuracy just by receiving the laser beam through the optical filter 12 as in the above-described embodiment. In addition, compared to the above-described embodiment, effects such as simplification of the configuration can be achieved because the first light receiving element 13 can be omitted.

  The laser oscillation wavelength detection method and its control method described above are summarized. The oscillation wavelength λ of the laser element 10 extends approximately linearly as the drive current I changes, and the light output (laser light intensity). P is also substantially proportional to the drive current I. Accordingly, the relationship between the drive current I, the oscillation wavelength λ, and the output intensity P of the laser element 10 is as shown in FIGS. 5 (a), 5 (b), and 5 (c), respectively.

  Here, with respect to the oscillation wavelength λ (λ1 to λ2) of the laser beam, as shown in FIG. 6A, a first optical filter (substantially no filter) having a flat received light amount ratio L, and When the laser beam is received through each of these optical filters using a bandpass type second optical filter exhibiting a selective light reception amount ratio L only for the oscillation wavelength λ (λ1 to λ2) As described above, since the output intensity of the laser beam itself changes according to the oscillation wavelength λ, the received light intensity P1 and P2 are as shown in FIG. When attention is paid to the ratio (Q2 / Q1) of these received light intensities, the received light amounts Q1 and Q2 are equal to each other in the above-mentioned wavelength (λ1 to λ2) range, so the received light amount ratio (Q2 / Q1) is [ 1], the amount of received light Q2 decreases when the wavelength (λ1 to λ2) is out of the range, and the ratio (Q2 / Q1) of the amount of received light decreases with a certain gradient as shown in FIG. 6 (c). . This attenuation gradient depends on the optical characteristic (band bus filter characteristic) of the second optical filter described above.

  Accordingly, the ratio (Q2 / Q1) of the received light amount when the drive currents I1 and I2 are applied to oscillate and output the laser beams having the oscillation wavelengths λ1 and λ2 from the laser element 10 and the reduction amount of the ratio is obtained. The oscillation wavelengths λ1 ′ and λ2 ′ of the laser light output from the laser element 10 when the drive currents I1 and I2 are applied are detected from the known optical characteristics (band bus filter characteristics) of the second optical filter. As a result, it is possible to detect a deviation from the oscillation wavelengths λ1 and λ2 to be obtained from the laser element 10.

  When the first and second optical filters have different transmittances (optical characteristics) as shown in FIG. 7A, for example, with respect to the oscillation wavelength λ (λ1 to λ2) of the laser light, The received light amounts Q1 and Q2 of the laser light respectively received through the optical filter are as shown in FIG. 7B, for example. In this case, generally, the received light amounts Q1 and Q2 do not become equal in the above-described wavelength range (λ1 to λ2). However, paying attention to the ratio (Q2 / Q1) of these received light quantities Q1 and Q2, as shown in FIG. 7C, there is some one-dimensional relationship with respect to the change in wavelength. Therefore, if this relationship is obtained in advance as a function F (λ), the oscillation wavelength λ of the laser beam can be obtained from the ratio (Q2 / Q1) of the received light amounts Q1 and Q2 according to the function F (λ).

  Therefore, the relationship between the driving current I of the laser element 10 and its oscillation wavelength λ shown in FIG. 5A and the oscillation wavelength of the laser beam detected as described above in the state where the driving current I is applied to the laser element 10. The shift of the oscillation wavelength can be detected from λ ′. Then, by adjusting the drive current I applied to the laser element 10 in accordance with the wavelength shift, the oscillation wavelength λ can be controlled with high accuracy. That is, according to the present invention, laser light is received through an optical filter having certain optical characteristics, and the oscillation wavelength can be easily detected by, for example, obtaining a ratio with the amount of received laser light that does not pass through the optical filter. Then, by adjusting the drive current for the laser element in accordance with the detected oscillation wavelength, the oscillation wavelength can be controlled with high accuracy.

  The present invention is not limited to the embodiment described above. In the embodiment shown in FIGS. 1 and 2, the laser light output from the laser element 10 is configured to pass through the lens 11 after passing through the optical filter 12, but the lens 11 is not passed through the optical filter 12. You may make it pass directly. That is, the optical filter 12 may be formed in an area that covers only the light receiving surface of the light receiving element 13 and may be disposed immediately before the light receiving element 13. Further, although the condensing lens 11 and the optical filter 12 are configured as separate bodies, the lens 11 itself can also function as a wavelength selective filter.

  In the embodiment, the transmission type optical filter 12 is used. However, it goes without saying that a reflection type optical filter may be used in the same manner. When a reflective optical filter is used, the function of the condensing lens 11 can be shared by using not only a plane mirror filter but also a concave mirror or convex mirror filter. As for the optical characteristics of the optical filter 12, it is sufficient if it has a sufficiently high transmittance (reflectance) for laser light in a wavelength band used for measurement, for example. Further, it is also possible to configure so as to detect the shift of the oscillation wavelength by paying attention to the change (output change) ΔP of the transmittance (reflectance) with respect to the oscillation wavelength.

  Furthermore, when detecting the intensity (amount of received light) of the laser light before and after the optical filter 12, the amount of attenuation at the optical filter 12 can be obtained from the amount of received light, so that the laser element 10 is not wavelength-modulated (that is, It is also applicable to laser devices (used at a certain wavelength). In the above embodiment, the wavelength response characteristic of the light receiving means is realized by a combination of a light receiving element having a flat wavelength response characteristic and an optical filter having an attenuation band. However, the light receiving element itself has an attenuation wavelength band. If it is a thing, it is also possible to comprise a light-receiving means by a single light-receiving element without using an optical filter.

  Furthermore, in the above-described embodiment, an example in which a semiconductor laser element is used as the laser element 10 and its oscillation wavelength is controlled by a drive current has been described, but the present invention is not limited to this. For example, if a wavelength tunable laser element is used as the laser element 10, the oscillation wavelength λ can be controlled by a voltage signal. In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

The principal part schematic block diagram of the laser apparatus to which the laser oscillation wavelength control method which concerns on the 1st Embodiment of this invention is applied. Changes in the light receiving intensity of laser light before and after passing through the optical filter in the laser apparatus shown in FIG. Furthermore, the figure which shows the drive current waveform, the output characteristic of a laser element, and the wavelength transmission characteristic of an optical filter. The principal part schematic block diagram of the laser apparatus to which the laser oscillation wavelength control method which concerns on the 2nd Embodiment of this invention is applied. The figure which shows the change of the light reception intensity | strength of the laser beam after permeate | transmitting an optical filter in the laser apparatus shown in FIG. 3, and the change of the light reception intensity | strength of the output laser beam of the laser element estimated from this change. The figure which shows the relationship between the drive current I, the oscillation wavelength (lambda), and the output intensity P in a laser element. The figure for demonstrating the principle of the wavelength detection at the time of using a band pass type optical filter. The figure for demonstrating the principle of a general wavelength detection in the case of using the two optical filters from which an optical characteristic differs. The principal part schematic block diagram of the laser apparatus using the self-coupling effect of a semiconductor laser element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Laser element 11 Condensing lens 12 Optical filter 13,14 Light receiver 20 Laser drive circuit 21 Current drive source 22 Modulation circuit 23 Wavelength detection circuit 24 Correction circuit

Claims (12)

  Two light receiving means having different wavelength response characteristics are used to receive laser beams output from one laser element, and the amounts of light received by the respective light receiving means are compared with each other to detect the oscillation wavelength of the laser light. And a laser oscillation wavelength detecting method.   2. The laser oscillation wavelength detecting method according to claim 1, wherein at least one of the light receiving means includes an optical filter having a known wavelength response characteristic and a light receiving element that receives the laser light through the optical filter.   The laser oscillation wavelength detection method according to claim 1 or 2, wherein the laser element changes the wavelength of the laser light with time.   The wavelength of the laser beam output from the laser element is changed over time, and the laser beam is received using a light receiving unit having a known wavelength response characteristic. The amount of light received by the light receiving unit and the light receiving unit are assumed in advance. And detecting the oscillation wavelength of the laser beam by comparing the received light receiving characteristics.   5. The laser oscillation wavelength detection method according to claim 4, wherein the light receiving means includes an optical filter having a known wavelength response and a light receiving element that receives the laser light through the optical filter.   5. The laser oscillation according to claim 4, wherein the light receiving characteristic of the light receiving means is estimated from a change in the amount of light received by the light receiving means when the oscillation wavelength of the laser light is changed over a predetermined bandwidth. Wavelength detection method.   An oscillation wavelength of a laser beam output from a laser element is detected using the laser oscillation wavelength detection method according to any one of claims 1 to 6, and the oscillation of the laser beam is performed based on the detected wavelength information of the laser beam. A laser oscillation wavelength control method, wherein the wavelength is feedback-controlled.   The laser oscillation wavelength control method according to claim 7, wherein the feedback control of the oscillation wavelength of the laser beam is performed by feedback control of a drive current for oscillating and driving the laser element. A semiconductor laser element;
Drive means for applying a drive current to the semiconductor laser element to oscillate and output laser light from the semiconductor laser element;
Two light receiving means for receiving laser beams output from the semiconductor laser elements having different wavelength response characteristics, respectively;
A wavelength detection means for detecting the oscillation wavelength of the laser light by comparing the amounts of light received by the light receiving means with each other;
A laser oscillation wavelength control comprising: wavelength control means for adjusting the drive current based on wavelength information of the laser light detected by the wavelength detection means to feedback control the oscillation wavelength of the laser light. apparatus. The driving means changes the oscillation wavelength of laser light output from the laser element by changing the drive current of the laser element over time,
The laser oscillation wavelength control device according to claim 9, wherein at least one of the light receiving means includes an optical filter having a known wavelength response characteristic and a light receiving element that receives the laser light through the optical filter. A semiconductor laser element for outputting laser light;
Drive means for changing the wavelength of the laser beam over time by changing the drive current of the semiconductor laser element;
A light receiving means for receiving a laser beam having a known wavelength response characteristic and output from the semiconductor laser element;
A wavelength detecting means for detecting the oscillation wavelength of the laser light by comparing the amount of light received by the light receiving means with a light receiving characteristic of the light receiving means assumed in advance;
A laser oscillation wavelength control comprising: wavelength control means for adjusting the drive current based on wavelength information of the laser light detected by the wavelength detection means to feedback control the oscillation wavelength of the laser light. apparatus. The light receiving means includes an optical filter having a known wavelength response, and a light receiving element that receives the laser light through the optical filter,
The wavelength detecting means estimates the light receiving characteristics of the light receiving means from the change in the amount of light received by the light receiving element when the oscillation wavelength of the laser light is changed over a predetermined bandwidth, and is used for wavelength detection. The laser oscillation wavelength control device according to claim 11.

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