Patent ID: 12206219

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the attached drawings will be referenced to describe embodiments according to the present technology in the following order.<1. Configuration of distance measuring apparatus><2. Distance measuring techniques><3. Circuit configuration related to emission driving><4. Variations in substrate configuration><5. Exemplary VCSEL structure><6. Temperature detection section><7. Example of driving emission according to temperature><8. Temperature detection in first embodiment><9. Temperature detection in second embodiment><10. Summary and modifications>

1. Configuration of Distance Measuring Apparatus

FIG.1illustrates an exemplary configuration of a distance measuring apparatus1as an embodiment of a light source apparatus according to the present technology.

As illustrated in the diagram, the distance measuring apparatus1is provided with an emission section2, a driving section3, a power supply circuit4, an emission-side optical system5, an imaging-side optical system6, an image sensor7, an image processing section8, a control section9, and a temperature detection section10.

The emission section2emits light from a plurality of light sources. As described later, the emission section2in this example includes vertical-cavity surface-emitting laser (VCSEL) light-emitting elements2aas the light sources, and these light-emitting elements2aare arrayed in a predetermined pattern, such as a matrix for example.

The driving section3includes an electrical circuit for driving the emission section2.

The power supply circuit4generates a power supply voltage for the driving section3(a driving voltage Vd described later) on the basis of an input voltage (an input voltage Vin described later) from a source such as a battery not illustrated that is provided in the distance measuring apparatus1, for example. The driving section3drives the emission section2on the basis of the power supply voltage.

Light emitted by the emission section2illuminates, through the emission-side optical system5, a subject S treated as the target of distance measurement. Thereafter, reflected light from the subject S out of the light emitted in this way is incident on the imaging surface of the image sensor7through the imaging-side optical system6.

The image sensor7is an image sensor such as a charge-coupled device (CCD) sensor or a complementary metal-oxide semiconductor (CMOS) sensor for example that receives reflected light from the subject S incident through the imaging-side optical system6as above, and converts the received light to output an electrical signal.

The image sensor7executes processes such as a correlated double sampling (CDS) process and an automatic gain control (AGC) process on the electrical signal obtained by photoelectric conversion of the received light, and furthermore performs an analog/digital (A/D) conversion process. An image signal is then output as digital data to the image processing section8downstream.

Additionally, the image sensor7in this example outputs a frame synchronization signal Fs to the driving section3. With this arrangement, the driving section3is capable of causing the light-emitting elements2ain the emission section2to emit light at timings according to the frame cycle of the image sensor7.

The image processing section8is configured as an image processor such as a digital signal processor (DSP), for example. The image processing section8performs various types of image signal processing on the digital signal (image signal) input from the image sensor7.

The control section9is provided with an information processing device such as a microcomputer including components such as a central processing unit (CPU), read-only memory (ROM), and random access memory (RAM), or a DSP. The control section9controls the driving section3for controlling the emission operations by the emission section2and controls imaging operations by the image sensor7.

The control section9includes functions that act as a distance measurement section9a. The distance measurement section9ameasures the distance to the subject S on the basis of the image signal input through the image processing section8(that is, the image signal obtained by receiving reflected light from the subject S). The distance measurement section9ain this example measures the distance to different portions of the subject S, thereby making it possible to identify the three-dimensional shape of the subject S.

Herein, specific techniques of measuring distance in the distance measuring apparatus1will be described in further detail later.

The temperature detection section10detects the temperature of the emission section2. A configuration that detects temperature using a diode for example can be adopted as the temperature detection section10.

In this example, information about the temperature detected by the temperature detection section10is supplied to the driving section3, thereby enabling the driving section3to drive the emission section2on the basis of the information about the temperature.

Alternatively, as illustrated by the dashed line, information about the temperature detected by the temperature detection section10may be supplied to the control section9, thereby enabling the control section9to control the driving section3on the basis of the information about the temperature to drive the emission section2according to the temperature.

In the present embodiment, as described later, a detection value correction process that improves the accuracy of the temperature detection by the temperature detection section10is performed, and this correction process (and related processes) is anticipated to be performed in the driving section3in one case and in the control section9in another case.

2. Distance Measuring Techniques

As the technique of measuring distance in the distance measuring apparatus1, a technique of measuring distance according to a structured light (STL) method or a time of flight (ToF) method can be adopted, for example.

The STL method measures distance on the basis of an image obtained by imaging the subject S illuminated with light having a predetermined light/dark pattern, such as a dot pattern or a grid pattern, for example.

FIGS.2A and2Bare diagrams explaining the STL method.

In the STL method, the subject S is illuminated with pattern light Lp having a dot pattern like the one illustrated inFIG.2A, for example. The pattern light Lp is divided into a plurality of blocks BL, and a different dot pattern is assigned to each block BL (the dot patterns are not duplicated among the blocks BL).

FIG.2Bis a diagram explaining the principle of distance measurement according to the STL method.

In the example herein, a wall W and a box BX placed in front are treated as the subject S, and the subject S is illuminated with pattern light Lp. In the diagram, “G” schematically represents the angle of view of the image sensor7.

Also, “BLn” in the diagram means the light from a certain block BL among the pattern light Lp, and “dn” means the dot pattern of the block BLn appearing in the captured image obtained by the image sensor7.

Here, in the case where the box BX in front of the wall W does not exist, the dot pattern of the block BLn appears in the captured image at a position “dn” in the diagram. In other words, the position where the pattern of the block BLn appears in the captured image is different between the case where the box BX exists and the case where the box BX does not exist, and more specifically, a distortion in the pattern occurs.

The STL method is a method of obtaining the shape and the depth of the subject S by utilizing how the illuminating pattern is distorted by the physical shape of the subject S in this way. Specifically, the STL method is a method of obtaining the shape and the depth of the subject S from the way in which the pattern is distorted.

In the case of adopting the STL method, an infrared (IR) image sensor with a global shutter is used as the image sensor7, for example. Additionally, in the case of the STL method, the distance measurement section9acontrols the driving section3such that the emission section2emits pattern light, and in addition, detects pattern distortion in the image signal obtained through the image processing section8, and calculates the distance on the basis of the way in which the pattern is distorted.

Next, the ToF method measures the distance to a target by detecting the time of flight (time difference) of light that is emitted by the emission section2, reflected by the target, and arrives at the image sensor7.

In the case of adopting what is called the direct ToF method as the ToF method, a single-photon avalanche diode (SPAD) is used as the image sensor7, and the emission section2is pulse-driven. In this case, the distance measurement section9acalculates the time difference from emission to reception for light that is emitted by the emission section2and received by the image sensor7on the basis of the image signal input through the image processing section8, and calculates the distance to different portions of the subject S on the basis of the time difference and the speed of light.

Note that in the case of adopting what is called the indirect ToF method (phase difference method) as the ToF method, an IR image sensor is used as the image sensor7, for example.

3. Circuit Configuration Related to Emission Driving

FIG.3illustrates an exemplary circuit configuration of a light source apparatus100that includes the emission section2, the driving section3, and the power supply circuit4illustrated inFIG.1. Note that in addition to the exemplary circuit configuration of the light source apparatus100,FIG.3also illustrates the image sensor7and the control section9illustrated inFIG.1.

In this example, the emission section2, the driving section3, and the power supply circuit4are formed on a common substrate (a substrate B described later). Here, the configuration unit that includes at least the emission section2and is formed on a common substrate with the emission section2is referred to as the light source apparatus100.

As illustrated in the diagram, the light source apparatus100is provided with the temperature detection section10in addition to the emission section2, the driving section3, and the power supply circuit4.

The emission section2is provided with a plurality of VCSEL light-emitting elements2aas described earlier. InFIG.3, the number of light-emitting elements2ais treated as “4” for convenience, but the number of light-emitting elements2ain the emission section2is not limited thereto, and is sufficiently at least two or more.

The power supply circuit4is provided with a DC/DC converter40, and generates a driving voltage Vd (DC voltage) that the driving section3uses to drive the emission section2on the basis of an input voltage Vin supplied as a DC voltage.

The driving section3is provided with a driving circuit30and a driving control section31.

The driving circuit30includes a switching element Q1and a switch SW for each light-emitting element2a, as well as a switching element Q2and a constant current source30a.

A field-effect transistor (FET) is used for the switching element Q1and the switching element Q2, and in this example, a P-channel metal-oxide-semiconductor (MOS) FET, or MOSFET, is used.

The switching elements Q1are connected in a parallel relationship with respect to the output line of the DC/DC converter40, or in other words the supply line of the driving voltage Vd, and the switching element Q2is connected in parallel with the switching elements Q1.

Specifically, the source of each of the switching elements Q1and the switching element Q2is connected to the output line of the DC/DC converter40. The drain of each switching element Q1is connected to the anode of a corresponding light-emitting element2aamong the light-emitting elements2ain the emission section2.

As illustrated in the diagram, the cathode of each light-emitting element2ais connected to ground (GND).

The drain of the switching element Q2is connected to ground through the constant current source30a, while the gate is connected to the node between the drain and the constant current source30a.

The gate of each switching element Q1is connected to the gate of the switching element Q2through a corresponding switch SW.

In the driving circuit30having the above configuration, the switching elements Q1whose switch SW is ON are electrically conductive, the driving voltage Vd is applied to the light-emitting elements2aconnected to the electrically conductive switching elements Q1, and the light-emitting elements2aemit light.

At this time, a driving current Id flows to the light-emitting elements2a, but in the driving circuit30having the above configuration, the switching elements Q1and the switching element Q2form a current mirror circuit, and the current value of the driving current Id is set to a value corresponding to the current value of the constant current source30a.

By controlling the ON/OFF state of the switches SW in the driving circuit30, the driving control section31controls the ON/OFF state of the light-emitting elements2a.

The frame synchronization signal Fs is supplied to the driving control section31by the image sensor7, thereby enabling the driving control section31to synchronize the ON timings and OFF timings of the light-emitting elements2awith the frame cycle of the image sensor7.

Additionally, the driving control section31is capable of controlling the ON/OFF state of the light-emitting elements2aon the basis of an instruction from the control section9.

Also, the driving control section31in this example controls the ON/OFF state of the light-emitting elements2aon the basis of the temperature of the emission section2detected by the temperature detection section10, but this control will be described in further detail later.

Note that, as described above, detection information from the temperature detection section10is supplied to the driving control section31or the control section9. The temperature detection is corrected as described later, and it is necessary to store a correction value (an offset value OF described later) used for the correction.

For example, in the case where the control section9is configured as a microcomputer, it is sufficient to store the correction value in an internal storage area (such as a register or RAM) or an external storage element (such as RAM or flash memory).

In the case where the driving control section31executes the temperature detection, it is sufficient to provide the driving control section31with a computational function provided by a microcomputer, a DSP, a logic circuit, or the like, and also with a memory function (such as a register, RAM, or flash memory).

Here,FIG.3illustrates an example of a configuration in which the switching elements Q1are provided on the anode side of the light-emitting elements2a, but like the driving circuit30A illustrated inFIG.4, a configuration in which the switching elements Q1are provided on the cathode side of the light-emitting elements2ais also possible.

In this case, the anode of each light-emitting element2ain the emission section2is connected to the output line of the DC/DC converter40.

For each of the switching elements Q1and the switching element Q2forming a current mirror circuit, an N-channel MOSFET is used. The drain and the gate of the switching element Q2is connected to the output line of the DC/DC converter40through the constant current source30a, while the source is connected to ground.

The drain of each switching element Q1is connected to the cathode of the corresponding light-emitting element2a, while the source is connected to ground. The gate of each switching element Q1is connected to the gate and the drain of the switching element Q2through each corresponding switch SW.

In this case as well, by controlling the ON/OFF state of the switches SW, the driving control section31can turn the light-emitting elements2aON/OFF.

FIG.5illustrates an exemplary configuration of a light source apparatus100A as a modification.

The light source apparatus100A is provided with a power supply circuit4A instead of the power supply circuit4and a driving section3A instead of the driving section3.

The power supply circuit4A includes multiple (in the illustrated example, two) DC/DC converters40. An input voltage Vin1is supplied to DC/DC converter40, while an input voltage Vin2is supplied to the other DC/DC converter40. The driving section3A is provided with multiple driving circuits30that accept the input of the driving voltage Vd from the respectively different DC/DC converters40. As illustrated in the diagram, in each driving circuit30, a variable current source30bis provided instead of the constant current source30a. The variable current source30bis a current source having a variable current value.

In this case, the light-emitting elements2ain the emission section2are divided into multiple light-emitting element groups whose states are controlled ON/OFF by different driving circuits30.

The driving control section31in this case controls the ON/OFF state of the switches SW in each driving circuit30.

Like the light source apparatus100A, by taking a configuration in which at least the pair of the DC/DC converter40and the driving circuit30are reproduced as multiple subsystems, the driving current Id of the light-emitting elements2acan be set to a different value for each subsystem. For example, by causing the voltage value of the driving voltage Vd and the current value of the variable current source30bto be different for each subsystem, the value of the driving current Id can be made different for each subsystem. Also, in a configuration in which the DC/DC converter40keeps the driving current Id constant, by making the target value of the constant current control different for each DC/DC converter40, the value of the driving current Id can be made difference for each subsystem.

In the case of adopting a configuration likeFIG.5, it is conceivable to make the values of the driving voltage Vd and the driving current Id different for each subsystem according to factors such as the emission intensity distribution and the temperature distribution in the emission section2. For example, it is conceivable to take measures such as increasing the driving current Id and also raising the driving voltage Vd for a subsystem corresponding to a high-temperature location in the emission section2.

4. Variations in Substrate Configuration

Here, the light source apparatus100may take the configurations illustrated inFIGS.6A,6B,7A,7B,7C,8A, and8B.

As illustrated inFIG.6A, the light source apparatus100may take a configuration in which a chip Ch2containing a circuit that acts as the emission section2, a chip Ch3containing a circuit that acts as the driving section3, and a chip Ch4containing the power supply circuit4are formed on the same substrate B.

Additionally, the driving section3and the power supply circuit4may also be formed in the same chip Ch34, and in this case, the light source apparatus100may take a configuration in which the chip Ch2and the chip Ch34are formed on the same substrate B, as illustrated inFIG.6B.

It is also possible to take a configuration in which a chip Ch is mounted on another chip Ch.

In this case, the light source apparatus100may take a configuration in which the chip Ch3having the chip Ch2mounted thereon and the chip Ch4are formed on the substrate B like inFIG.7A, a configuration in which the chip Ch3having the chip Ch2and the chip Ch4mounted thereon is formed on the substrate B like inFIG.7B, or a configuration in which the chip Ch34having the chip Ch2mounted thereon is formed on the substrate B like inFIG.7C, for example.

Additionally, the light source apparatus100may also take a configuration that includes the image sensor7.

For example,FIG.8Aillustrates an example of a configuration of the light source apparatus100in which the chip Ch2, the chip Ch3, and the chip Ch4as well as a chip Ch7containing a circuit that acts as the image sensor7are formed on the same substrate B.

Also,FIG.8Billustrates an example of a configuration of the light source apparatus100in which the chip Ch34having the chip Ch2mounted thereon and the chip Ch7are formed on the same substrate B.

Note that the light source apparatus100A described above likewise may adopt a configuration similar to those described usingFIGS.6A,6B,7A,7B,7C,8A, and8B.

5. Exemplary VCSEL Structure

Next, an exemplary structure of the chip Ch2in which the emission section2is formed will be described with reference toFIGS.9and10.

FIG.9illustrates an exemplary structure of the chip Ch2in the case of being formed on the substrate B like inFIGS.6A,6B, and8A, whileFIG.10illustrates an exemplary structure of the chip Ch2in the case of being mounted onto another chip Ch like inFIGS.7A,7B,7C, and B.

Note that, as an example,FIGS.9and10illustrate an exemplary structure corresponding to the case where the driving circuit30is inserted on the anode side of the light-emitting elements2a(seeFIG.3).

As illustrated inFIG.9, in the chip Ch2, the portions corresponding to each of the light-emitting elements2aare formed as mesas M.

A semiconductor substrate20is used as the substrate of the chip Ch2, and a cathode electrode Tc is formed on the underside of the semiconductor substrate20. For the semiconductor substrate20, a gallium arsenide (GaAs) substrate is used, for example.

On the semiconductor substrate20, in each mesa M, a first multilayer reflective layer21, an active layer22, a second multilayer reflective layer25, a contact layer26, and an anode electrode Ta are formed in order from bottom to top.

A current constriction layer24is formed in a part (specifically the lower part) of the second multilayer reflective layer25. Also, the portion including the active layer22that is sandwiched between the first multilayer reflective layer21and the second multilayer reflective layer25acts as a resonator23.

The first multilayer reflective layer21is formed using a compound semiconductor exhibiting N-type conductivity, while the second multilayer reflective layer25is formed using a compound semiconductor exhibiting P-type conductivity.

The active layer22acts as a layer for generating laser light, while the current constriction layer24acts as a layer that injects current efficiently into the active layer22and achieves a lens effect.

After the mesas M are formed, the current constriction layer24is subjected to selective oxidation in the unoxidized state, and includes a central oxidized region (also referred to as a selectively oxidized region)24aand an unoxidized region24bthat is not oxidized in the periphery of the oxidized region24a. In the current constriction layer24, a current constricting structure is formed by the oxidized region24aand the unoxidized region24b, and current is conducted to the current constriction region as the unoxidized region24b.

The contact layer26is provided to ensure an ohmic contact with the anode electrode Ta.

The anode electrode Ta is formed on the contact layer26in an annular (ring) shape or the like that is open in the center for example when looking at a plan view of the substrate B. In the contact layer26, the portion where the anode electrode Ta is not formed on top acts as an opening26a.

Light generated in the active layer22travels back and forth inside the resonator23and then is emitted to the outside through the opening26a.

Here, the cathode electrode Tc in the chip Ch2is connected to ground through a ground lead Lg formed in a wiring layer of the substrate B.

Also, in the diagram, a pad Pa represents a pad for the anode electrode formed on the substrate B. The pad Pa is connected to the drain of any one of the switching elements Q1included in the driving circuit30through a lead Ld formed in the wiring layer of the substrate B.

In the diagram, the anode electrode Ta is illustrated as being connected to the single pad Pa through an anode lead La formed on the chip Ch2and a bonding wire BW for only one light-emitting element2a, but the pad Pa and the lead Ld are formed for each light-emitting element2aon the substrate B, and furthermore, the anode lead La is formed for each of the light-emitting elements2aon the chip Ch2, and the anode electrodes Ta of the individual light-emitting elements2aare connected to the corresponding pad Pa through the corresponding anode lead La and bonding wire BW.

Next, in the case ofFIGS.11A and11B, a back-illumination chip Ch2is used as the chip Ch2. In other words, rather than emitting light in the upward direction (surface direction) of the semiconductor substrate20like the example inFIG.10, a chip Ch2of a type that emits light in the back direction of the semiconductor substrate20.

In this case, an opening for emitting light is not formed in the anode electrode Ta, and the opening26ais not formed in the contact layer26.

In the chip Ch3(or the chip Ch34; the same applies hereinafter in the description ofFIGS.11A and11B) in which the driving section3(driving circuit30) is formed, the pad Pa for establishing an electrical connection with the anode electrode Ta is formed for each light-emitting element2a. In the wiring layer of the chip Ch3, the lead Ld is formed for each pad Pa. Although omitted from illustration, each of the pads Pa is connected, by these leads Ld, to the drain of a corresponding switching element Q1in the driving circuit30formed in the chip Ch3.

Also, in the chip Ch2, the cathode electrode Tc is connected to an electrode Tc1and an electrode Tc2via leads Lc1and Lc2, respectively. The electrode Tc1and the electrode Tc2are electrodes for respectively connecting with a pad Pc1and a pad Pc2formed in the chip Ch3.

In the wiring layer of the chip Ch3, a ground lead Lg1connected to the pad Pc1and a ground lead Lg2connected to the pad Pc2are formed. Although not illustrated, these ground leads Lg1and Lg2are connected to ground.

The connections between each anode electrode Ta in the chip Ch2and each pad Pa in the chip Ch3as well as the connections between the electrodes Tc1and Tc2in the chip Ch2and the pads Pc1and Pc2in the chip Ch3are established through respective solder bumps Hb.

In other words, the mounting of the chip Ch2on the chip Ch3in this case is achieved by what is called flip chip mounting.

6. Temperature Detection Section

Next, the temperature detection section10will be described.

In the case where the chip Ch2is formed on the substrate B like inFIGS.6A,6B, and8Afor example, it is sufficient to form temperature detection elements such as diodes in the temperature detection section10at positions near the chip Ch2in the substrate B (such as positions beside the chip Ch2on the substrate B, for example).

Also, in the case where the chip Ch2is mounted onto another chip Ch like inFIGS.7A,7B,7C, andFIG.8B, it is sufficient to form the temperature detection elements at positions near the chip Ch2in the other chip Ch (such as positions underneath the mesas M of the chip Ch2, for example).

The temperature detection section10includes a plurality of temperature sensors10aincluding temperature detection elements such as diodes.

FIGS.11A and11Billustrate exemplary arrangements of the temperature sensors10ain the temperature detection section10.

In the example ofFIG.11A, the plurality of temperature sensors10aare not concentrated in a single location, but are dispersed in a plane parallel to the plane in which the light-emitting elements2aare arrayed.

This case illustrates an example in which the VCSEL light-emitting elements2adescribed above are arranged regularly in a matrix horizontally and vertically, and the temperature sensors10alikewise are arranged regularly. In other words, the temperature sensors10aare arranged at substantially equal intervals in a plane parallel to the plane in which the light-emitting elements2aare arrayed.

In this case, the plurality of temperature sensors10ais arranged such that one temperature sensor10ais disposed for each emission block containing a predetermined number of light-emitting elements2a, for example.

On the other hand,FIG.11Billustrates an example in which the light-emitting elements2aare not arranged in a matrix but instead are arranged for the purpose of forming a predetermined emission pattern, and likewise, the temperature sensors10aare not arranged in a matrix but instead are arranged with suitable positions selected according to the arrangement of the light-emitting elements2a.

As inFIGS.11A and11B, various arrangements of the light-emitting elements2aand the temperature sensors10aare anticipated depending on the purpose of the distance measuring apparatus1.

Although not illustrated, there are also cases where the light-emitting elements2aare arranged regularly in a matrix horizontally and vertically while the temperature sensors10aare arranged in a non-matrix layout, and conversely, there are also cases where the light-emitting elements2aare arranged in a non-matrix layout while the temperature sensors10aare arranged regularly in a matrix horizontally and vertically.

Furthermore, it is sufficient to provide one temperature sensor10aat a time in correspondence with a predetermined unit of one or multiple light-emitting elements2a, and for example, one temperature sensor10amay be provided in correspondence with one light-emitting element2a, or one temperature sensor10amay be provided with respect to a block of several light-emitting elements2a. The number of light-emitting elements2aand the number of temperature sensors10aand the ratio of the two are considered to be diverse.

Also, by dispersing the plurality of temperature sensors10alike in the examples ofFIGS.11A and11B, it is possible to detect an in-plane temperature distribution of the emission section2. In addition, different temperatures can be detected for different areas of the emission surface, and furthermore, by increasing the number of disposed temperature sensors10a, it is also possible to detect different temperatures for different predetermined units of light-emitting elements2a.

Here, for the process by a first embodiment described later, a reference temperature sensor10R is disposed as illustrated inFIGS.11A and11B.

The reference temperature sensor10R is considered to be disposed at a position relatively distant from the light-emitting elements2a. However, the reference temperature sensor10R is not necessarily stipulated to be disposed at such a position.

The reference temperature sensor10R is used to compute a correction value (offset value OF) that corrects inconsistencies in the absolute accuracy of each of the temperature sensors10a. Details will be described later.

FIGS.12A,12B, and12Cillustrate examples of the circuit configuration of one of the temperature sensors10a.

The example inFIG.12Ais a configuration in which a current I1flows through FETs91and92to diodes D1and D2that act as a temperature detection element110. A resistor R1is connected between the drain of the FET92and the anode of the diode D2. The voltage appearing at the anode end of the diode D1and the voltage (V1) appearing at the resistor R1are input into an op-amp93. The output of the op-amp93is connected to the gates of the transistors91and92. In this case, a voltage Vo detected by a resistor R2connected between the anode terminal of the op-amp93and ground is a temperature detection value corresponding to the temperature.

The example inFIG.12Bis a configuration in which currents2I1and I1flow through the FETs91and92to a series connection of diodes D1aand D1band a series connection of diodes D2aand D2bthat act as the temperature detection element110. The voltage V2appearing at the anode end of the diode D1aand the voltage V1appearing at the diode D2aare input into an op-amp94. The output of the op-amp94is the voltage (V2-V1), and is a temperature detection value corresponding to the temperature.

The example inFIG.12Cis a configuration in which the current I1flows through the FET91to a series connection of diodes D1aand D1bthat act as the temperature detection element110. The voltage V1appearing at the anode end of the diode D1ais input into an amp95. The output voltage2VD of the amp95is a temperature detection value corresponding to the temperature.

Note that the above configurations are merely examples. Various configurations other than the above are anticipated.

Also, inFIGS.12B and12C, the number of diodes D is changeable if necessary. Also, inFIGS.12A,12B, and12C, the current value is changeable to any value.

For example, in these examples, the portions of at least the diodes D enclosed by the dashed lines are disposed as the temperature detection elements110at the positions of the temperature sensors10ainFIGS.11A and11B.

FIG.13illustrates the placement of one of the temperature sensors10ain correspondence with the example ofFIG.10earlier. In this configuration, the chip ch3is disposed below the chip ch2in which the light-emitting elements2aare formed.

FIG.13schematically illustrates the switching elements Q1, the switches SW, the switching element Q2, and the constant current source30aforming the driving circuit30illustrated inFIG.3earlier as being formed in the chip ch3. The leads in the driving circuit30are formed in a wiring layer100.

Additionally, as illustrated in the diagram, the components of the temperature sensor10a, such as the FETs91and92, the diodes Da and D1b, and a current source30c, for example, are formed inside the chip ch3together with the driving circuit30. Also, necessary leads are formed in the wiring layer100.

Regarding the diodes D that are the temperature detection elements in the temperature sensor10ahere, various numbers of diodes and connection configurations are conceivable as illustrated inFIGS.12A,12B, and12C, but the diodes D that form the configuration portion acting as the temperature detection element110are considered to be disposed underneath the mesas M. For example, at least one or more temperature detection elements110are disposed in correspondence with each mesa M. With this arrangement, it is possible to detect the temperature of the light-emitting elements2ain each mesa M, which is suited to controlling each unit of light-emitting elements2ain each mesa M as the predetermined unit.

Obviously, as described above, one temperature detection element110may also be provided with respect to one light-emitting element2a, or one temperature detection element110may be provided with respect to a block of light-emitting elements2a, irrespectively of the mesas M. In any case, the temperature detection element110is considered to be formed in the chip ch3(or ch34) together with the driving circuit30, for example.

Note that in the case where the chip ch2is not stacked onto the chip ch3(or ch34), it is conceivable to dispose the temperature detection elements110surrounding the chip ch2, provide a layer in the temperature detection elements110are formed underneath the chip ch2, or the like.

7. Example of Driving Emission According to Temperature

An example of driving the light-emitting elements2aaccording to temperature in the case of providing the temperature sensors10aas above will be described.

As a basic example that is anticipated, the driving current value or the emission period is changed according to the temperature.

The light-emitting elements2ahave a property in which the emission efficiency falls as the temperature rises. Accordingly, the length of the emission period and the driving current value are changed for each predetermined unit of light-emitting elements2acorresponding to a temperature sensor10aaccording to the temperature detected by the temperature sensor10a.

With this arrangement, light emission of stable intensity can be achieved regardless of temperature.

Additionally, it is conceivable to switch the emission driving between simultaneous emission and time-division emission.

When measuring distance by causing the emission section2in which a plurality of VCSEL light-emitting elements2ais arrayed to emit light like the distance measuring apparatus1described above, first, a driving method that causes the plurality of light-emitting elements2ato emit light simultaneously is conceivable.

FIG.14is a diagram for explaining an example of such driving by simultaneous emission.

As an initial premise, when measuring distance, the emission section2emits light repeatedly according to a fixed emission cycle. Specifically, the emission cycle is synchronized with the frame cycle of the image sensor7. An emission target period St in the diagram is synchronized with the frame period of the image sensor7. For example, the frame rate of the image sensor7is 60 fps, and the emission target period St is set to 16.6 milliseconds (ms).

Here, the following description assumes that when measuring distance, all of the light-emitting elements2ain the emission section2emit light during each emission target period St. The number of light-emitting elements2ain the emission section2is assumed to be 800 for the sake of explanation. In other words, there are 800 emission channels from CN1to CN800.

In the driving method illustrated inFIG.14, the light-emitting elements2afrom CN1to CN800are made to emit light simultaneously during each emission target period St. At this time, the period in which each light-emitting element2ais made to emit light (the ON period) is shorter than the emission target period St, and is set to approximately 4 ms, for example.

In the case of performing simultaneous emission like the above, the temperature of the chip (chip Ch2) in which the light-emitting elements2aare formed rises easily, and depending on the ambient temperature, this may lead to a heat-induced malfunction such as a drop in the emission efficiency of the light-emitting elements2aor degraded circuit performance by the driving circuit (driving circuit30,30A) that drives the light-emitting elements2a.

Accordingly, it is conceivable to drive the plurality of light-emitting elements2a(CN1to CN800) that are to emit light in the emission target period St according to time-division emission in the emission target period St in response to the temperature conditions.

FIG.15illustrates an example of time-division emission.FIG.15illustrates an example of dividing the light-emitting elements2ain 800 channels that are to emit light in the emission target period St into two groups, such that inside the emission target period St, the 400 light-emitting elements2afrom CN1to CN400are made to emit light and then the remaining 400 light-emitting elements2afrom CN401to CN800are made to emit light.

By performing such time-division emission, as illustrated inFIG.16, the peak value of the temperature can be moderated compared to the case of simultaneous emission. In other words, a suppression of a rise in the temperature of the chip Ch2may be attained.

Time-division emission like the above is achieved by having the driving control section31control the switches SW. In this example, the driving control section31includes a logic circuit, and the logic circuit is configured to control the switches SW for the above time-division emission.

As an example of time-division emission, the light-emitting elements2aare not limited to being divided into the two groups from CN1to CN400and from CN401to CN800as above, and may also be divided into three or more groups.

At this time, the number of light-emitting elements2amade to emit light at the same time in time-division emission may also be changed in the time direction. For example, after causing the 400 elements from CN1to CN400to emit light, the 200 elements from CN401to CN600are made to emit light, and then the remaining 200 elements from CN601to CN800are made to emit light. In other words, the number of light-emitting elements2amade to emit light at the same time in time-division emission may be decreased in the time direction.

When performing time-division emission, there is a high probability that the surrounding temperature will rise for later elements in the order of emission. Consequently, by decreasing the number of light-emitting elements2amade to emit light at the same time in the time direction as above, or in other words, by decreasing the number of light-emitting elements2alater in the order of emission to less than the number of light-emitting elements2aearlier in the order of emission, a suppression of the temperature peak value in the emission target period St may be attained, and the effect of suppressing the temperature rise can be enhanced.

At this point, the driving control section31in this example is configured to be capable of switching between simultaneous emission driving that causes the light-emitting elements2ato emit light simultaneously as illustrated in the example ofFIG.14, and time-division emission driving that causes the light-emitting elements2ato emit light by time division as illustrated in the example ofFIG.15. Specifically, the driving control section31switches between the simultaneous emission driving and the time-division emission driving on the basis of the temperature detected by the temperature detection section10.

The drop in the emission efficiency of the light-emitting elements2ais relatively noticeable in the region at and above 70° C., for example. For this reason, it is conceivable to set a value equal to or less than 70° C. for example as a temperature threshold TH, and switch between the simultaneous emission driving and the time-division emission driving by using the threshold TH as a reference.

The flowchart inFIG.17illustrates an example of the flow of operations by the driving control section31in the case of switching between the simultaneous emission driving and the time-division emission driving according to the temperature.

As illustrated in the diagram, if the temperature detected by the temperature detection section10is not the threshold TH or higher (step S101: N), the driving control section31causes the light-emitting elements2ain all channels to emit light simultaneously (step S102). On the other hand, if the temperature detected by the temperature detection section10is the threshold TH or higher (step S101: Y), the driving control section31causes the light-emitting elements2ato emit light by time division (step S103).

In the embodiment herein, the temperature detection section10is provided with a plurality of temperature sensors10a, and in step S101, it is conceivable to adopt a representative value of the temperature detection values from the temperature sensors10a. Note that the temperature detection values referred to herein are the temperature detection values that have been corrected as described later.

For example, it is conceivable to use the average of the temperature detection values from the plurality of temperature sensors10aas the representative value. Alternatively, it is also conceivable to treat a temperature detection value from a predetermined temperature sensor10a(for example, the temperature sensor10ahaving the highest temperature detection value) as the representative value.

Here, when executing the time-division emission driving, the driving control section31drives the light-emitting elements2asuch that the total amount of luminescence by the emission section2(the total amount of luminescence in the emission target period St) is the same as when executing the simultaneous emission driving. Specifically, if the ON period of each light-emitting element2awhen executing the simultaneous emission driving is 4 ms as described above, for example, the ON period of each light-emitting element2ain the time-division emission driving is also set to 4 ms.

Note that in the case of reproducing the DC/DC converter40and the driving circuit30as multiple subsystems like the example illustrated inFIG.5, the ON periods of the light-emitting elements2afor each driving circuit30are made uniform while also making the values of the driving current Id uniform for example, thereby causing the total amount of luminescence to be the same.

By executing the simultaneous emission driving, even if there is motion in the subject S targeted for distance measurement, it is possible to prevent the combined reception of reflected light from when the subject S is at different positions inside a single frame period, and a drop in the distance measurement accuracy may be prevented.

By switching between the time-division emission driving and the simultaneous emission driving as above, both a prevention of a drop in the distance measurement accuracy and a suppression of a rise in the temperature can be attained.

Note that it is not essential to switch between the simultaneous emission driving and the time-division emission driving, and a configuration that always executes the time-division emission driving and switches the method of division according to the temperature is also conceivable.

Also, the above illustrates an example of switching the driving method for the entire plurality of light-emitting elements2a, but the driving method may also be switched for each block of light-emitting elements2a.

As an example, the light-emitting elements in 900 channels may be divided into blocks of 100 channels each, and the driving method may be switched between the simultaneous emission driving and the time-division emission driving in units of the 100-channel blocks.

In this case, the driving method is switched according to the temperature detected for each block (or a representative value of the temperature detection values in the case where a plurality of temperature sensors10aare provided in correspondence with the block).

For example, in the case of simultaneous emission driving, the 100 channels are made to emit light simultaneously, while in the case of time-division emission driving, the 100 channels are divided into two groups, such that inside the emission target period St, the 50 light-emitting elements2afrom CN1to CN50are made to emit light and then the remaining 50 light-emitting elements2afrom CN51to CN100are made to emit light.

In the emission section2, a temperature distribution occurs easily in the plane in which the light-emitting elements2aare arranged. The temperature conditions are different depending on the location, such as the temperature rising more easily closer to the center, for example. Accordingly, by forming and controlling blocks for each location according to the temperature, more precise driving control can be achieved.

As yet another example of driving, it is conceivable to change the number of concurrent emission groups in the time-division emission according to the temperature.

Here, a concurrent emission group means a group of light-emitting elements2amade to emit light at the same time in time-division emission. For example, in time-division emission that drives the light-emitting elements2ain 800 channels by 400 channels at a time like the example described earlier, each group of light-emitting elements2ain 400 channels corresponds to a concurrent emission group.

In this example, the number of concurrent emission groups is increased in response to a rise in temperature.

FIG.18is a flowchart illustrating the flow of operations performed by the driving control section31.

First, in this example, a plurality of thresholds TH are set as the threshold TH of the temperature detected by the temperature detection section10. Here, an example of setting a first threshold TH1and a second threshold TH2having a larger value than the first threshold TH1is assumed.

When the temperature detected by the temperature detection section10is below the first threshold TH1(step S201: Y), the driving control section31executes the simultaneous emission driving (step S102). Also, in the case where the temperature detected by the temperature detection section10is not lower than the first threshold TH1(step S201: N), when the temperature is the first threshold TH1or higher and also lower than the second threshold TH2(step S202: Y), the driving control section31executes time-division emission in two groups (step S203). In other words, the light-emitting elements2aare driven by time-division emission with the number of concurrent emission groups set to “2”, or more specifically, time-division emission of 400 channels and 400 channels is executed, for example.

Also, when the temperature detected by the temperature detection section10is the second threshold TH2or higher (step S202: N), the driving control section31executes time-division emission in three groups (step S204). That is to say, the light-emitting elements2aare driven by time-division emission with the number of concurrent emission groups set to “3”, or more specifically, time-division emission driving of 400 channels→200 channels→200 channels is executed, for example.

By increasing the number of concurrent emission groups in response to a rise in the temperature as above, it is possible to drive emission with a further enhanced effect of suppressing a rise in the temperature in response to the temperature increasing.

Consequently, malfunctions associated with a rise in the temperature can be made to occur less readily.

Here, the first threshold TH1is set to the same value as the threshold TH described above (for example, approximately 70° C.), while the second threshold TH2is set to a temperature lower than an allowable limit temperature (for example, approximately 130° C.) dictated by the specifications of the chip Ch2, for example. With this arrangement, in the case where the temperature rises enough that a drop in the emission efficiency is expected, time-division emission driving in two groups can be executed, and in the case where the temperature rises enough that the temperature is expected to reach the allowable limit temperature, time-division emission driving in three groups can be executed, or in other words, time-division emission driving with a further enhanced effect of suppressing a rise in the temperature can be executed.

In the case of such an example of driving, it is also conceivable to execute the above control independently for each predetermined unit of the light-emitting elements2a.

Obviously, various examples of emission driving control according to the temperature besides the examples illustrated above are conceivable.

In addition, the various types of emission driving control like the above are performed on the basis of temperature detection values that have been corrected as described below.

8. Temperature Detection in First Embodiment

The emission driving control according to the temperature like the above naturally is based on the result of the temperature detection section10detecting the temperature. In the present embodiment, the temperature detection accuracy is improved.

Hereinafter, the temperature detection process according to the first embodiment will be described.

Note that the processes related to temperature detection described as the first and second embodiments hereinafter may be executed by the driving control section31or by the control section9. For the sake of explanation, the processes are assumed to be executed by the driving control section31, but the processes are also similar in the case of being executed by the control section9.

FIG.19illustrates an example of a process before emission driving executed by the driving control section31as the first embodiment.

The driving control section31performs the process inFIG.19before driving the emission by the emission section2, for example. This is a process of computing an offset value OF that acts as a correction value in correspondence with each temperature sensor10a.

In step S301, the driving control section31sets a variable n=1. Here, “n” is a variable for sequentially specifying the individual temperature sensors10aas the processing target. A total number nMAX described later is assumed to be the total number of temperature sensors10a.

In step S302, the driving control section31first acquires a temperature detection value TMPA from the reference temperature sensor10R.

In step S303, the driving control section31acquires a temperature detection value TMPn from the nth temperature sensor10a. First, because the variable n=1, the temperature detection value TMP1from the 1st temperature sensor10ais acquired. Note that the driving control section31sets an order of the temperature sensors10afrom the 1st to the (nMAX)th, and the 1st temperature sensor10arefers to the 1st temperature sensor10ain the set order.

In step S304, the driving control section31computes an offset value OFn for the nth temperature sensor10aby subtracting the temperature detection value TMPn from the temperature detection value TMPA of the reference temperature sensor10R.

For example, the offset value OF1for the 1st temperature sensor10ais computed by the operation (TMPA)-(TMP1).

Thereafter, in step S305, the driving control section31stores the offset value OFn for the nth temperature sensor10ain internal memory or the like. For example, the offset value OF1for the 1st temperature sensor10ais stored. It is also conceivable to store the offset value OFn in non-volatile memory, for example.

In step S306, the driving control section31checks whether or not the variable n has reached the total number nMAX, and if not, the driving control section31increments the variable n in step S307and returns to step S303. In other words, a similar process is performed for each temperature sensor10alike the 2nd temperature sensor10a, the 3rd temperature sensor10a, and so on, and respectively corresponding offset values OF2, OF3, and so on are computed and stored.

When the offset value OF has been stored for all of the temperature sensors10a, the process inFIG.19ends after step S306.

By performing the above process before starting emission, the offset value OF for each temperature sensor10aobtained by using the temperature detection value from the reference temperature sensor10R as a reference can be stored.

Note that because this process obtains the offset value OF corresponding to the error in the absolute accuracy of each temperature sensor10a, it is sufficient to perform the process at least once.

However, to absorb changes in properties due to aging and environmental changes, the process may also be performed periodically or every time the emission (that is, distance measurement) operations are executed.

By storing the offset value OF for each temperature sensor10a, the driving control section31is able to correct and acquire temperature detection values according to the process inFIG.20while driving the emission by the emission section2.

FIG.20illustrates an example in which the driving control section31executes the temperature detection at a predetermined timing, such as a periodic timing for example, while driving emission.

When the temperature detection timing is reached, the driving control section31proceeds from steps S401to S402inFIG.20, and sets the variable n specifying the individual temperature sensors10aton=1.

Next, in step S403, the driving control section31acquires the temperature detection value TMPn from the nth temperature sensor.

In step S404, the driving control section31reads out the offset value OFn stored for the nth temperature sensor.

In step S405, the driving control section31performs temperature correction. Namely, the offset value OFn is added to the temperature detection value TMPn to obtain a corrected temperature detection value TMPSn for the nth temperature sensor10a.

Next, in step S406, the driving control section31stores the corrected temperature detection value TMPSn in an internal register or the like as the temperature detection value for the nth temperature sensor10a.

In step S407, the driving control section31checks whether or not the variable n has reached the total number nMAX, and if not, the driving control section31increments the variable n in step S408and returns to step S403.

Consequently, corrected temperature detection values (TMPS1to TMPS(nMAX)) are acquired by the process from step S403to step S406for the 1st temperature sensor10a, the 2nd temperature sensor10a, the 3rd temperature sensor10a, and so on to the last temperature sensor10a.

When temperature detection is complete for all of the temperature sensors10a, the process inFIG.20ends after step S407. Thereafter, when the next temperature detection timing is reached, the process again proceeds from steps S401to S402, and the temperature is detected similarly.

With the temperature detection results for each of the temperature sensors10acorrected in this way, the temperature conditions of the emission section2can be checked accurately. By having the driving control section31control the emission driving method like in the examples described above according to the temperature detection results, appropriate emission operations according to the temperature are achieved.

9. Temperature Detection in Second Embodiment

The second embodiment will be described. The second embodiment is an example of a case where the reference temperature sensor10R is not provided, as inFIGS.21A and21B. With regard to the arrangement of the temperature sensors10aand the light-emitting elements2a, various examples similar to the case described usingFIGS.11A and11Babove are conceivable.

The driving control section31performs the process inFIG.22as the process of computing the offset value OF before emission.

In step S351, the driving control section31sets the variable n specifying the individual temperature sensors10aton=1.

In step S352, the driving control section31acquires the temperature detection value TMPn from the nth temperature sensor10a.

In step S353, the driving control section31stores the temperature detection value TMPn for the nth temperature sensor10ain an internal register or the like.

In step S354, the driving control section31checks whether or not the variable n has reached the total number nMAX, and if not, the driving control section31increments the variable n in step S355and returns to step S352.

Consequently, detected temperature detection values TMP1to TMP(nMAX) are acquired by the process in steps S352and S353for each of the 1st temperature sensor10a, the 2nd temperature sensor10a, the 3rd temperature sensor10a, and so on to the last temperature sensor10a.

When the temperature detection values TMP1to TMP(nMAX) have been stored for all of the temperature sensors10a, the driving control section31proceeds to step S356and computes an average value TMPav of the temperature detection values TMP1to TMP(nMAX).

Next, in step S357, the driving control section31sets the variable to n=1, and proceeds to step S358.

In step S358, the driving control section31computes the offset value OFn for the nth temperature sensor10a. That is to say, the temperature detection value TMPn stored earlier for the nth temperature sensor10aand the average value TMPav are used to compute the offset value OFn by (TMPav)−(TMPn).

In step S359, the driving control section31stores the offset value OFn for the nth temperature sensor10ain an internal register, RAM, or non-volatile memory.

In step S360, the driving control section31checks whether or not the variable n has reached the total number nMAX, and if not, the driving control section31increments the variable n in step S361and returns to step S358.

Consequently, offset values OF1to OF(nMAX) are acquired by the process in steps S358and S359for each of the 1st temperature sensor10a, the 2nd temperature sensor10a, the 3rd temperature sensor10a, and so on in order to the last temperature sensor10a.

When the offset value OF has been stored for all of the temperature sensors10a, the process inFIG.22ends after step S360.

By performing the above process before starting emission, even in the case where the reference temperature sensor10R is not provided, the offset value OF for each temperature sensor10aobtained by using the average value of all temperature sensors10aas a reference can be stored.

Note that this process may also be performed at least once, but to absorb changes in properties due to aging and environmental changes, the process may also be performed periodically or every time the emission (that is, distance measurement) operations are executed.

The processing during emission, or in other words the process of correcting the temperature detection values, is similar toFIG.20of the first embodiment.

10. Summary and Modifications

In the above embodiment, effects like the following are obtained.

A light source apparatus (distance measuring apparatus1) according to the embodiment is provided with the emission section2in which a plurality of vertical-cavity surface-emitting laser light-emitting elements2ais arrayed, the driving circuit section30that causes the plurality of light-emitting elements2aof the emission section2to emit light, the temperature detection section10that includes a plurality of temperature sensors10aarranged to detect the temperature of the emission section2, and a control section (the driving control section31or the control section9).

When the light-emitting elements2aof the emission section2are driven to emit light by the driving circuit section30, the control section performs a process of correcting the detection value TMPn of each of the plurality of temperature sensors10aby using a correction value set in a non-emission period for each temperature sensor10a(seeFIG.20).

By using the correction value (offset value OF) preset for each temperature sensor to correct the detection value, a temperature detection value (corrected detection value TMPSn) guaranteeing absolute accuracy can be acquired. With this arrangement, the temperature conditions of the emission section2can be ascertained accurately, making it possible to perform appropriate emission driving control according to the temperature conditions.

In the embodiment, the correction value is taken to be the offset value OF indicating the difference from the reference detection value for the detection value of each temperature sensor10a.

By measuring the offset value OF as the difference from the reference detection value in advance for use as a correction value, an appropriate correction value can be used for each of the temperature sensors10a.

The embodiment gives an example in which the correction value (offset value OF) is computed by using the temperature detection value TMPn of each temperature sensor10aobtained in a non-emission period during which the driving circuit section30is not driving the light-emitting elements2aof the emission section2to emit light, and a reference detection value (seeFIGS.19and22).

The detection value from each temperature sensor10ain the non-emission period during which the light-emitting elements2ado not emit light is a detection value that is unaffected by temperature changes due to emission by the light-emitting elements2a. Consequently, if the temperature detection value TMPn and the reference detection value are compared at this time, it is possible to obtain a correction value (offset value OF) corresponding to the accuracy inconsistencies in each temperature sensor10aitself, including those caused by manufacturing due to factors such as the size and placement of each temperature sensor10a. With this arrangement, each temperature sensor10acan be corrected accurately, and the temperature detection accuracy can be improved.

The embodiment gives an example in which the temperature detection section10includes the reference temperature sensor10R as an absolute thermometer, and the reference detection value is the temperature detection value TMPA from the reference temperature sensor10R (FIG.19).

As illustrated inFIGS.11A and11B, by disposing the single reference temperature sensor10R for the entire system and treating the reference temperature sensor10R as an absolute thermometer that serves as a reference, the reference detection value when computing the correction value is established. With this arrangement, the reference detection value is established, and the offset value OF can be computed appropriately.

The embodiment gives an example in which the reference detection value is the average value TMPav of the temperature detection values from the plurality of temperature sensors10a(FIG.22).

In the case where the reference temperature sensor10R is not provided like inFIGS.21A and21B, the average of the temperature detection values from all of the temperature sensors10ais obtained and treated as the reference detection value, for example.

With this arrangement, the reference detection value can be acquired without providing the absolute reference temperature sensor10R, and the offset value OF for each temperature sensor10acan be computed appropriately.

Note that the average value TMPav is not necessarily the average of all of the temperature sensors10a, and may also be the average of some of the temperature sensors10a.

The embodiment describes an example in which each temperature sensor10a(particularly, each temperature detection element110) is disposed underneath each mesa M where the light-emitting elements2aare formed (seeFIG.13).

For example, in the case where the light-emitting elements2ahaving a diode structure are formed as mesas, the temperature detection elements110of the temperature sensors10aare arranged in correspondence with each mesa M.

With this arrangement, the temperature conditions of each mesa M can be detected, and the driving of the light-emitting elements2acan be controlled according to the mesa temperature.

The driving circuit section30of the embodiment is configured to be capable of individually driving the emission operation for each predetermined unit of a plurality of the light-emitting elements2a(seeFIG.3and the like).

With this configuration, the emission driving current is set to turn emission ON/OFF individually for each light-emitting element or in units of blocks acting as multiple light-emitting element groups, for example.

This arrangement achieves a configuration capable of control according to the temperature conditions for each predetermined unit ascertained as the temperature detection value from each temperature sensor10a.

Additionally, driving control according to an in-plane temperature distribution of the emission section2is possible.

With regard to the distance measuring sensor1, by controlling the light-emitting elements2afor each predetermined unit, exposure with uniform emission and light energy is possible, and the brightness of the image of reflected light from the target (subject S) appearing in the image captured by the image sensor7can be made to approach uniformity. With this arrangement, the distance measurement sensing accuracy is also improved.

The embodiment gives an example in which the method of driving the emission section2by the driving circuit section30is switched on the basis of the temperature detection values corrected and acquired by the control section (the driving control section31or the control section9).

The driving method is switched according to the corrected temperature detection values, such as by switching between simultaneous emission driving that causes the plurality of light-emitting elements to emit light simultaneously inside an emission target period, and time-division emission driving that causes the plurality of light-emitting elements to emit light at alternating times inside an emission target period, for example.

With this arrangement, appropriate driving is achieved according to the temperature detection values obtained with high accuracy.

The switching of the driving method according to the temperature may be performed for each predetermined unit (individually or in blocks) of light-emitting elements2a, or may be performed universally on all of the light-emitting elements2a.

The embodiment describes an example in which the emission section2emits light in synchronization with the frame period of the image sensor7that receives light emitted by the emission section2and reflected by the subject.

With this arrangement, to handle the case of measuring distance by illuminating a subject with light emitted by the emission section and receiving the light with an image sensor, it is possible to cause the light-emitting elements to emit light at appropriate timings according to the frame cycle of the image sensor.

Consequently, an improvement in distance measurement accuracy may be attained. In addition, a suppression of a temperature rise in correspondence with the case where a light source apparatus is used as the light source for measuring the distance to the subject may be attained.

Note that the above describes an example of a configuration in which the switch SW is provided for each light-emitting element2ato enable individual control of each light-emitting element2a, but in the present technology, a configuration enabling the individual driving of each light-emitting element2ais not essential.

Additionally, although the above describes an example in which the present technology is applied to a distance measuring apparatus, the present technology is not limited to being applied to a light source for distance measurement.

Note that the effects described in this specification are merely non-limiting examples, and there may be other effects.

Note that the present technology may be configured as below.

(1)

A light source apparatus including:an emission section in which a plurality of vertical-cavity surface-emitting laser light-emitting elements is arrayed;a driving circuit section configured to cause the plurality of light-emitting elements of the emission section to emit light;a temperature detection section including a plurality of temperature sensors arranged to detect a temperature of the emission section; anda control section configured to, when the light-emitting elements of the emission section are driven by the driving circuit section, correct a detection value from each of the plurality of temperature sensors by using a correction value set for each of the temperature sensors.

(2)

The light source apparatus according to (1), in whichthe correction value is an offset value indicating a difference from a reference detection value for the detection value from each of the temperature sensors.

(3)

The light source apparatus according to (1) or (2), in whichthe correction value is computed by using the detection value of each of the temperature sensors obtained in a non-emission period during which the driving circuit section is not driving the light-emitting elements of the emission section to emit light, and a reference detection value.

(4)

The light source apparatus according to (2) or (3), in whichthe temperature detection section includes a reference temperature sensor as an absolute thermometer, andthe reference detection value is a detection value from the reference temperature sensor.

(5)

The light source apparatus according to (2) or (3), in whichthe reference detection value is an average of detection values from the plurality of temperature sensors.

(6)

The light source apparatus according to any one of (1) to (5), in whichthe temperature sensors are respectively disposed underneath mesas where the light-emitting elements are formed.

(7)

The light source apparatus according to any one of (1) to (6), in whichthe driving circuit section is configured to be capable of individually driving emission operation for each predetermined unit of a plurality of the light-emitting elements.

(8)

The light source apparatus according to any one of (1) to (7), in whicha method of driving the emission section by the driving circuit sectionis switched on the basis of a temperature detection value corrected and acquired by the control section.

(9)

The light source apparatus according to any one of (1) to (8), in whichthe emission section is configured to emit light in synchronization with a frame period of an image sensor configured to receive light emitted by the emission section and reflected by a subject.

(10)

A temperature detection method executed by a light source apparatus including an emission section in which a plurality of vertical-cavity surface-emitting laser light-emitting elements is arrayed,a driving circuit section configured to cause the plurality of light-emitting elements of the emission section to emit light, anda temperature detection section including a plurality of temperature sensors arranged to detect a temperature of the emission section,the method including:correcting, when the light-emitting elements of the emission section are driven by the driving circuit section, a detection value from each of the plurality of temperature sensors by using a correction value set for each of the temperature sensors.

(11)

A sensing module including:an emission section in which a plurality of vertical-cavity surface-emitting laser light-emitting elements is arrayed;a driving circuit section configured to cause the plurality of light-emitting elements of the emission section to emit light;a temperature detection section including a plurality of temperature sensors arranged to detect a temperature of the emission section; anda control section configured to, when the light-emitting elements of the emission section are driven by the driving circuit section, correct a detection value from each of the plurality of temperature sensors by using a correction value set for each of the temperature sensors; andan image sensor configured to capture an image by receiving light emitted by the emission section and reflected by a subject.

REFERENCE SIGNS LIST

1Distance measuring apparatus2Emission section2aLight-emitting element3,3A Driving section7Image sensor10Temperature detection section10aTemperature sensor10R Reference temperature sensor110Temperature detection element