JP2019113376A - Optical device - Google Patents

Abstract

To provide an optical device that can remove noise while suppressing reduction in the measurement accuracy.SOLUTION: A light reception unit 4 receives light emitted from a laser device 2 into the inside through a filter part 3. Adjusting a transmission wavelength region of the filter part 3 on the basis of the result of the light reception allows reflected light to be received even if there has been a change in the wavelength (laser wavelength λ) of an emitted light from the laser device 2. Using the light emitted in the inside makes it possible to remove noise while suppressing reduction in the measurement accuracy.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical device.

  In general, there is known a method of measuring a distance to an object based on a propagation time required from emission to light reception by emitting light such as a laser and receiving light reflected by the object. As such, when measuring the distance optically, outside light other than the reflected light may be received, which is a cause of noise. Therefore, as an apparatus using an optical distance measuring method, one provided with a specific frequency component removing means has been proposed (see, for example, Patent Document 1). In the device described in Patent Document 1, noise is reduced by removing specific frequency components from the received signal under predetermined conditions.

JP 2012-220466 A

  However, as described in Patent Document 1, various judgments have to be made in order to remove a specific frequency component from the received signal, and there is a disadvantage that complicated control is required. Then, the method of removing the exterior light used as noise and receiving only reflected light is considered by using the filter part which permeate | transmits the light of a predetermined wavelength range.

  At this time, although the noise is more easily removed as the transmission wavelength range of the filter section is narrower, the wavelength of the emitted light may change depending on the temperature, and the reflected light may pass through the filter section depending on the temperature. It may not be possible. Therefore, although it is conceivable to monitor the wavelength change by receiving a part of the light emitted toward the object, the received light can not be used for the measurement of the object, and the measurement efficiency (the energy consumption of the emission part Of the reflected light).

  Therefore, an object of the present invention is, as one example, to provide an optical device capable of removing noise while suppressing a decrease in measurement efficiency.

  In order to solve the problems described above and achieve the object, the optical device of the present invention according to claim 1 has an emitting unit for emitting light to the inside and the outside, a variable transmission wavelength range of light, and A reflected light from which light emitted to the outside is reflected by the object, a filter unit to which the light emitted to the inside is incident, a light receiving unit to receive the light transmitted through the filter unit, and the light to the inside And a controller configured to adjust a transmission wavelength range of the filter based on a result of receiving the received light by the light receiver.

FIG. 1 is a block diagram showing an optical apparatus according to a first embodiment of the present invention. It is a flowchart which shows an example of the 1st adjustment method which adjusts the transmission wavelength range of a filter part in the said optical apparatus. It is a graph which shows intensity distribution of the light which the radiation | emission part of the said optical apparatus radiate | emits. It is a graph which shows an example of a change of the light reception intensity at the time of changing the transmission wavelength range of the said filter part in time. It is a graph which shows another example of a change of the light reception intensity at the time of changing the transmission wavelength range of the said filter part in time. It is a flowchart which shows an example of the 2nd adjustment method which adjusts the transmission wavelength range of a filter part in the said optical apparatus. FIG. 5 is a block diagram showing an optical apparatus according to a second embodiment of the present invention. It is a side view showing an optical device concerning the 1st modification of the present invention. It is a side view showing the optical device concerning the 2nd modification of the present invention. It is a graph which shows the timing which the said radiation | emission part radiate | emits pulsed light. It is a flowchart which shows an example of the other adjustment method which adjusts the transmission wavelength range of a filter part in the said optical apparatus.

  Hereinafter, embodiments of the present invention will be described. An optical device according to an embodiment of the present invention includes: an emitting unit that emits light to the inside and the outside; a reflected light in which a transmission wavelength range of light is variable and light emitted to the outside is reflected by an object; The transmission wavelength range of the filter unit is determined based on the result of light reception by the filter unit on which the light emitted inside is incident, the light reception unit for receiving light transmitted through the filter unit, and the light reception unit for light emitted inside. And a control unit for adjusting.

  The emitting part emits light to the inside and the outside, and only the light emitted to the outside is used to measure the object. At this time, the light emitted to the inside and the light emitted to the outside have the same wavelength. The light emitted inside is received by the light receiving unit through the filter unit, and by adjusting the transmission wavelength range of the filter unit based on the light reception result, the wavelength of the light emitted by the emitting unit changes. Even if there is, it can receive reflected light. At this time, by utilizing the light emitted to the inside, noise can be removed while suppressing a decrease in measurement efficiency. Here, the outside is the outside of the optical device, and the inside is the inside of the optical device. Further, the light emitted to the outside is, for example, forward emitted light, and the light emitted to the inside is, for example, backward emitted light.

  Preferably, the control unit determines the optimum transmission wavelength range of the filter unit based on the change in the light reception intensity of the light receiving unit when the transmission wavelength range of the filter unit is changed with time.

  The intensity of light emitted to the inside is maximum at a predetermined wavelength (emission wavelength), and shows a sharp decrease at a wavelength shifted from the emission wavelength. That is, when the transmission wavelength range of the filter section is changed over time, the light reception intensity increases as the transmission wavelength range approaches the emission wavelength, and decreases as the distance goes away. When the transmission wavelength range is changed from the state including the emission wavelength to the state not including the emission wavelength and is changed again to the state not including the emission wavelength, the light reception intensity once rises and then turns to fall. On the other hand, when the emission wavelength is not included even if the transmission wavelength range is changed, the temporal change of the light reception intensity is monotonously increasing or monotonously decreasing. Therefore, the emission wavelength can be estimated based on the light reception intensity when the transmission wavelength range is changed with time, and the optimum transmission wavelength range can be determined.

  The emission intensity of the emission unit is controlled so that the light reception intensity of the light emitted to the inside is constant, and the control unit controls the transmission wavelength range of the filter unit so that the power consumption of the emission unit is minimized. You may adjust the

  When the emission wavelength is included in the transmission wavelength range, the light emitted inside is transmitted through the filter unit and is received by the light receiving unit to obtain a predetermined light receiving intensity. On the other hand, when the emission wavelength is out of the transmission wavelength range, the light emitted to the inside is difficult to be received by the light receiving unit, and the light reception intensity decreases. At this time, in order to keep the light reception intensity constant, it is necessary to increase the emission intensity, and the power consumption also increases. Therefore, by adjusting the transmission wavelength range of the filter unit so as to minimize the power consumption of the emission unit, it is possible to set the optimum transmission wavelength range to include the emission wavelength.

  The control unit further includes: a separation unit that separates the light emitted inside into a light traveling toward the filter unit and a light traveling in the other direction; and a comparison light receiving unit that receives light traveling in the other direction. The transmission wavelength range of the filter unit may be adjusted based on the comparison between the light reception intensity by the light reception unit and the light reception intensity by the comparison light reception unit.

  The light receiving unit receives light passing through the filter unit, and the comparison light receiving unit receives light not passing through the filter unit. Assuming that the intensities of the two lights separated by the separation unit are substantially equal, when the emission wavelength is included in the transmission wavelength range, the light reception intensity by the light reception unit and the light reception intensity by the comparison light reception unit become substantially equal. On the other hand, when the emission wavelength is not included in the transmission wavelength range, the light reception intensity by the light reception unit is lower than the light reception intensity by the comparison light reception unit. Therefore, by adjusting the transmission wavelength range of the filter unit based on the comparison of the received light intensities (calculation of the difference or ratio), the optimum transmission wavelength range can be set to include the emission wavelength. When the intensities of the two lights separated by the separation unit are different from each other, the received light intensities may be appropriately corrected and compared.

  Examples of the present invention will be specifically described below.

[First embodiment]
As shown in FIG. 1, the optical device 1A of the present embodiment includes a laser device 2 as an emitting unit, a filter unit 3, a light receiving unit 4, a temperature sensor 5, and a judgment processing unit 6. The optical device 1A is mounted, for example, on a vehicle as a moving object, and emits a laser to the outside of the vehicle to measure the distance to the object, using the other vehicle, the road installation object, the pedestrian, etc. as the object. It is used to detect the shape of an object.

  The laser device 2 is, for example, a semiconductor laser, and emits a laser beam when a voltage is applied. At both end surfaces of the element of the laser device 2, mirrors that transmit (reflect) a part of incident light and reflect (transmit) the rest are provided. The emitted laser light enters this mirror and is transmitted and reflected. The light thus amplified is emitted through the mirror. At this time, one mirror is easier to transmit than the other mirror, and the light passing through one mirror (that is, the easy-to-transmit mirror) becomes the light emitted to the outside, and passes through the other mirror. The light that is emitted becomes the light emitted inside. Further, this one side is the front side of the laser device 2 and the other side is the rear side. The light emitted from the laser device 2 may be, for example, an infrared ray.

  The laser device 2 is controlled by the laser driver 21 and the emission power is controlled by the auto power controller 22 so that the light reception intensity to be described later by the light receiving unit 4 to be described later becomes constant. At this time, the current (laser drive current) for driving the laser device 2 is measured by the laser drive current monitor 23.

  The filter unit 3 is a variable-wavelength filter in which the transmission wavelength range of light is variable, and the transmission wavelength range is adjusted by the wavelength-variable filter control unit 31. In addition, the filter unit 3 is disposed on the rear side of the laser device 2, and light emitted from the laser device 2 to the inside is made to enter the filter unit 3 and to pass therethrough. In addition, the filter unit 3 has a larger area than the laser device 2 when viewed from the laser emission direction. As a result, although the light emitted to the outside is reflected by the object, the reflected light travels toward the light receiving unit 4 and a part is blocked by the laser device 2, but the other part is going to pass through the filter unit 3. Do.

  The light receiving unit 4 is a light receiving element capable of receiving light of a wavelength in a predetermined range, and is disposed on the rear side of the filter unit 3. That is, the laser device 2, the filter unit 3, and the light receiving unit 4 are disposed in this order from the front side to the rear side. Further, the area of the light receiving unit 4 viewed from the laser emission direction is equal to or less than the area of the filter unit 3, and the light receiving unit 4 is configured to receive only the light transmitted through the filter unit 3. The light receiving unit 4 converts light into an electric signal and outputs the electric signal. The electric signal is amplified by the light receiving element I / V converting and amplifying unit 41. The size of each optical component can be appropriately designed by arranging a lens or the like in the optical system. For example, since the wavelength filter and the light receiving element are generally small and inexpensive and high performance, it is also possible to appropriately arrange a condensing lens in the light path and design it optimally.

  The temperature sensor 5 measures the temperature of the laser device 2, outputs the measurement result as an electrical signal, and the electrical signal is amplified by the temperature sensor output amplification unit 51.

  The determination processing unit 6 includes, for example, a central processing unit (CPU) provided with a memory such as a random access memory (RAM) or a read only memory (ROM), controls the entire optical device 1A, and functions as a control unit. . The determination processing unit 6 acquires information (receives a signal) from the laser drive current monitor 23, the light receiving element I / V conversion amplification unit 41, and the temperature sensor output amplification unit 51, and controls the wavelength tunable filter control unit 31. A signal is transmitted to adjust the transmission wavelength range of the filter unit 3.

  Hereinafter, a specific example of a method in which the determination processing unit 6 adjusts the transmission wavelength range of the filter unit 3 will be described. Although the light receiving unit 4 receives not only the light emitted to the inside but also the reflected light, the light receiving intensity of the light emitted to the inside is sufficiently high, so when adjusting the transmission wavelength range, It is sufficient if the light receiving intensity of the light emitted inside is taken into consideration.

As a first adjustment method, the determination processing unit 6 determines the optimum transmission wavelength range of the filter unit 3 based on the change in the light reception intensity of the light reception unit 4 when the transmission wavelength range of the filter unit 3 is changed with time. Just do it. That is, as shown in FIG. 2, the judgment processing unit 6 performs constant power control of the laser device 2 by the auto power controller 22 (step S1), and is the temperature changed based on the information acquired by the temperature sensor output amplification unit 51? determines whether (step S2), and when the temperature is changed (Y in step S2), the received light intensity to adjust the center wavelength value lambda _f of the filter unit 3 so as to maximize (step S3). The wavelength center value λ _f of the filter unit 3 is a value that is the center of the transmission wavelength range.

Here, a specific example of the above step S3 will be described. The intensity of the light emitted from the laser device 2, as shown in FIG. 3, becomes maximum at the lasing wavelength lambda _LD, illustrating the distribution decreases rapidly at wavelengths away from the laser wavelength lambda _LD. At this time, the center wavelength value lambda _f of the filter unit 3, when the time is varied so as to reciprocate in a range of ± [Delta] [lambda] with respect to a laser wavelength lambda _LD, light intensity, time-varying, as shown in FIG. That is, when the wavelength center value λ _f matches the laser wavelength λ _LD , the light reception intensity is maximized, and when λ _f = λ _LD ± Δλ, the light reception intensity is minimum. Therefore, the period of the received light intensity is half of the period for changing the center wavelength value lambda _f time.

On the other hand, when the wavelength center value λ _f of the filter unit 3 is time-changed to reciprocate in the range of 2Δλ so as not to include the laser wavelength λ _LD , the light reception intensity changes with time as shown in FIG. That is, when the wavelength center value λ _f is closest to the laser wavelength λ _LD (in the illustrated example, it becomes the maximum value λ _{max in} this range), the received light intensity becomes maximum, and the wavelength center value λ _f is the laser wavelength λ _LD At the farthest point (in the illustrated example, the minimum value λ _min of this range), the light reception intensity is minimum. Therefore, the period of the received light intensity is consistent with the period of changing the center wavelength value lambda _f time.

Thus, based on the period of the light reception intensity, it is possible to determine whether or not the laser wavelength λ _LD is included in the transmission wavelength range when the wavelength center value λ _f is changed. When the laser wavelength λ _LD is included, the laser wavelength λ _LD can be specified. On the other hand, when the laser wavelength λ _LD is not included, the transmission wavelength region is positioned on the long wavelength side or on the short wavelength side with respect to the laser wavelength λ _LD based on whether the light reception intensity increases or decreases monotonously. It can be determined whether it is positioned, and the range may be shifted to change the wavelength center value λ _f again.

  As a second adjustment method, in a state where the emission intensity of the laser device 2 is controlled so that the light reception intensity of the light emitted to the inside by the light receiving unit 4 becomes constant, the judgment processing unit 6 consumes the laser device 2 The transmission wavelength range of the filter unit 3 may be adjusted to minimize the power. That is, as shown in FIG. 6, the judgment processing unit 6 performs constant power control of the laser device 2 by the auto power controller 22 (step S4), and is the temperature changed based on the information acquired by the temperature sensor output amplification unit 51? It is determined (step S5) whether or not the temperature has changed (Y in step S5), it is determined whether the drive current obtained by the laser drive current monitor 23 has risen (step S6). The voltage applied to the laser device 2 is constant, and the power consumption also increases as the drive current increases.

When the drive current obtained by the laser drive current monitor 23 rises (Y in step S6), the determination processing unit 6 shifts the wavelength center value λ _f to the long wavelength side (step S7), and the laser drive current monitor 23 When the drive current obtained by the above decreases (N in step S6), the determination processing unit 6 shifts the wavelength center value λ _f to the short wavelength side (step S8). The determination processing unit 6 repeatedly executes steps S6 to S8, and ends the adjustment of the wavelength center value λ _f when the drive current is minimized (step S9). Thus, if the transmission wavelength range of the filter unit 3 is adjusted so that the drive current of the laser device 2 is minimized (the power consumption is minimized), the optimum transmission wavelength to include the laser wavelength λ _f You can set the area.

According to the above configuration, the light emitted inside from the laser device 2 is received by the light receiving unit 4 through the filter unit 3, and the transmission wavelength range of the filter unit 3 is adjusted based on the light reception result. Even when the wavelength of the light emitted from the device 2 (laser wavelength λ _LD ) changes, the reflected light can be received. At this time, by utilizing the light emitted to the inside, noise can be removed while suppressing a decrease in measurement efficiency.

Second Embodiment
As shown in FIG. 7, an optical device 1B according to this embodiment includes a laser device 2 as an emitting unit, a filter unit 3, a light receiving unit 4, a judgment processing unit 6, a separating unit 7, a comparison light receiving unit 8 and And. The optical device 1 B may include the temperature sensor 5.

  The separation unit 7 is disposed between the laser device 2 and the filter unit 3 and separates the light emitted inside from the laser device 2 into light toward the filter unit 3 and light toward the other direction. .

  The comparison light receiving unit 8 is a light receiving element capable of receiving light of a wavelength within a predetermined range, and is arranged to receive light separated by the separation unit 7 and traveling in the other direction. That is, the comparison light receiving unit 8 receives the light emitted inside from the laser device 2 without passing through the filter unit 3.

  The light receiving unit 4 and the comparison light receiving unit 8 transmit an electric signal to the determination processing unit 6 in response to light reception. Note that this electrical signal may be appropriately amplified. When the electric signal is amplified as described above, the amplification factor may be set according to the intensity ratio of the two lights separated by the separation unit 7. Hereinafter, when the light passes through the filter unit 3, the signal intensity received by the determination processing unit 6 from the light receiving unit 4 and the signal intensity received by the determination processing unit 6 from the comparison light receiving unit 8 are substantially equal. Do.

Hereinafter, a specific example of a method in which the determination processing unit 6 adjusts the transmission wavelength range of the filter unit 3 will be described. As a third adjustment method, the determination processing unit 6 adjusts the transmission wavelength range of the filter unit 3 based on the comparison between the light reception intensity by the light reception unit 4 and the light reception intensity by the comparison light reception unit 8. When the laser wavelength λ _LD and the wavelength center value λ _f of the filter unit 3 substantially coincide with each other, the light emitted inside and traveling toward the filter unit 3 is transmitted through the filter unit 3 and the light receiving intensity by the light receiving unit 4 is compared with the received light. The light reception intensity by the portion 8 is substantially equal. On the other hand, when the laser wavelength λ _LD and the wavelength center value λ _f of the filter unit 3 are deviated, the light emitted inside and directed to the filter unit 3 can not be transmitted through the filter unit 3. The light reception intensity by the light reception intensity is lower than the light reception intensity by the comparison light receiving unit 8. Therefore, the judgment processing unit 6 may adjust the transmission wavelength range of the filter unit 3 so that the light reception intensity ratio of these approaches 1 and the filter unit 3 so that the difference of the light reception intensity ratio of these approaches 0. The transmission wavelength range of may be adjusted.

  With the above configuration, the light emitted inside from the laser device 2 is received by the light receiving unit 4 through the filter unit 3, and the transmission wavelength range of the filter unit 3 is adjusted based on the light reception result. As in the first embodiment, noise can be removed while suppressing a decrease in measurement efficiency.

  The present invention is not limited to the above-described embodiment, but includes other configurations and the like that can achieve the object of the present invention, and the following modifications and the like are also included in the present invention.

  For example, in the first embodiment, although the light receiving unit 4 receives both the light emitted inside from the laser device 2 and the reflected light by one component, these light components are different depending on different components. You may receive light. For example, as shown in FIG. 8 as an optical device 1C of the first modification, the first light receiving element 4B, which is a light receiving portion for receiving light emitted inside, and the light receiving portion for receiving reflected light. A second light receiving element 4C may be provided. The area of the second light receiving element 4C is sufficiently larger than the area of the first light receiving element 4B and equal to or less than the area of the filter section 3 when viewed from the laser emission direction.

  In the first embodiment, the light receiving portion 4 receives light without being condensed by a lens or the like, but a condensing lens may be provided. For example, as shown in FIG. 9 as an optical device 1D of the second modified example, a condensing lens 9 may be provided between the first light receiving element 4B and the second light receiving element 4C. The condensing lens 9 is for condensing reflected light, and can reduce the area of the light receiving surface of the second light receiving element 4C. In addition, a lens may be provided in the structure which has only one light-receiving part, and a lens may be provided before and behind a filter part. Thereby, each member can be appropriately reduced in area.

  In the first embodiment, when adjusting the transmission wavelength range of the filter unit 3, the correction according to the drive current of the laser device 2 is not performed, but the filter unit according to the drive current of the laser device 2 The transmission wavelength range of 3 may be corrected. The correction method will be described below along with the timing at which the laser device 2 emits pulsed light.

  The laser device 2 scans the irradiation position on the object while emitting pulse light at predetermined time intervals. In the example shown in FIG. 10, pulse light having a width of 10 nsec is emitted at an interval of 1 μsec, and a plurality of pulse lights constitute a pulse group (200 msec). In one pulse group, the irradiation position is scanned on a continuous line (straight line, curved line, zigzag line), the laser is turned off (20 msec) when changing the scanning start position, and the irradiation position is scanned again in another pulse group Do.

  Prior to such scanning of the laser light (500 msec in the illustrated example), the laser device 2 emits one pulse group. In this pulse group, when the light receiving portion 4 can receive light in 10 nsec which is turned on, it is not necessary to perform the correction according to the drive current as in the first embodiment.

A predetermined drive current is supplied to the laser device 2 also for 1 μsec which is turned off in the pulse group, and light emitted inside is also present. Therefore, the light receiving unit 4 may receive light at the timing when the pulse group is turned off, and the transmission wavelength range of the filter unit 3 may be adjusted based on the light reception result. At this time, the laser wavelength λ _LD of the laser device 2 may change depending on the difference between the drive current in the off state and the drive current in the on state. At this time, the transmission wavelength range of the filter unit 3 may be corrected as described below.

The determination processing unit 6 executes steps S10 to S15 similar to steps S4 to S9 in the second adjustment method shown in FIG. After that, the judgment processing unit 6 calculates the current increase of the actually used light output pulse (step S16). The current increase of the actual use light output pulse is the difference between the drive current when the pulse is turned on and when the pulse is turned off. Next, the judgment processing unit 6 corrects the wavelength center value λ _f according to the current increase of the actually used light output pulse (step S17). The relationship between the current increase and the correction amount of the wavelength center value λ _f may be stored in advance as an equation or a table.

  Besides, the best configuration, method and the like for carrying out the present invention are disclosed in the above description, but the present invention is not limited to this. That is, although the present invention has been particularly illustrated and described primarily with respect to particular embodiments, it should be understood that the present invention may be configured relative to the above-described embodiments without departing from the spirit and scope of the present invention. Those skilled in the art can make various modifications in materials, quantities, and other detailed configurations. Therefore, the description with the above-described disclosure of the shape, the material, etc. is exemplarily described for facilitating the understanding of the present invention, and is not intended to limit the present invention. The description in the name of a member from which some or all of the limitations such as the limitation have been removed is included in the present invention.

1A, 1B Optical device 2 Laser device (emitting part)
3 filter unit 4 light receiving unit 6 judgment processing unit (control unit)
7 separation unit 8 comparison light receiving unit

Claims (4)

An emitting unit that emits light to the inside and the outside;
A filter section which has a variable transmission wavelength range of light and in which the light emitted to the outside is reflected by the object and the light emitted to the inside is incident;
A light receiving unit that receives light transmitted through the filter unit;
An optical device comprising: a control unit that adjusts a transmission wavelength range of the filter unit based on a light reception result of the light emitted to the inside by the light receiving unit.   The control unit may determine an optimal transmission wavelength range of the filter unit based on a change in light reception intensity of the light receiving unit when the transmission wavelength range of the filter unit is changed with time. The optical device described in. The emission intensity of the emission unit is controlled such that the light reception intensity of the light emitted into the interior by the light reception unit is constant.
The optical device according to claim 1, wherein the control unit adjusts a transmission wavelength range of the filter unit such that power consumption of the emission unit is minimized. A separation unit that separates the light emitted into the inside into light traveling toward the filter unit and light traveling in another direction;
And a comparison light receiving unit that receives light traveling in the other direction,
The optical device according to claim 1, wherein the control unit adjusts a transmission wavelength range of the filter unit based on comparison of the light reception intensity by the light reception unit and the light reception intensity by the comparison light reception unit. .

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