Patent Description:
A time-of-flight (ToF) method is a ranging method. In the TOF method, light is emitted by a light emitter, and the light reflected off a measurement-target object is detected by a detector. This makes it possible to measure a three-dimensional shape of the measurement-target object.

For example, a ranging method is known that includes diffusing, by a diffusion plate, pieces of light that respectively exit a plurality of light emitters, irradiating the diffused pieces of light onto a measurement-target range, and detecting the reflected pieces of light by a light detector that includes two dimensionally arranged light-receiving/emitting sections. In this ranging method, exiting light is diffused by a diffusion plate. Thus, a short-distance measurement can be performed over a range of light. However, this ranging method is not suitable for a long-distance measurement.

On the other hand, Patent Literature <NUM> discloses a ranging method including collimating pieces of light that exit a plurality of light emitters (forming the pieces of light into pieces of parallel light) using a lens; and irradiating the entirety of an irradiation range with beams of the pieces of light respectively exiting the plurality of light emitters. This method is suitable for a long-distance measurement since exiting light is formed into a beam.

Previously proposed arrangements are disclosed in <CIT>, which discloses a two-dimensional array of vertical cavity surface emitting laser elements.

However, a detector that detects light reflected off a measurement-target object has the property of having a high light-receiving sensitivity for light that enters from a direction vertical to the detector and having a low light-receiving sensitivity for light that enters from a direction oblique to the detector. Thus, there is a problem in which there is a reduction in the accuracy in ranging performed with respect to a surrounding portion in a measurement-target range.

In view of the circumstances described above, it is an object of the present technology to provide a light-emitting element that has a vertical-cavity surface-emitting laser structure and is suitable for a long-distance light irradiation, and a ranging apparatus.

In order to achieve the object described above, a light-emitting element according to an embodiment of the present technology includes a plurality of light emitters, a first electrode terminal, and a second electrode terminal.

The plurality of light emitters is a plurality of light emitters one-dimensionally or two-dimensionally arranged in a direction that is vertical to an optical axis corresponding to light that exits each of the plurality of light emitters, each of the plurality of light emitters being a vertical-cavity surface-emitting laser element, each of the plurality of light emitters including a first electrode and a second electrode, each of the plurality of light emitters emitting the light due to current flowing from the first electrode to the second electrode.

The first electrode terminal is electrically connected to the first electrode.

The second electrode terminal is electrically connected to the second electrode.

A current path from the first electrode terminal to the second electrode terminal that passes through one of the plurality of light emitters exhibits an electrical resistance different from an electrical resistance of a current path from the first electrode terminal to the second electrode terminal that passes through another of the plurality of light emitters.

The light-emitting element may have a central region and a surrounding region, as viewed from a direction extending in parallel with the optical axis, the central region including the light emitter situated in an inner portion of the plurality of light emitters, the surrounding portion including the light emitter situated in an outer portion of the plurality of light emitters, and
the current path passing through the light emitter being included in the plurality of light emitters and being situated in the central region may exhibit a higher electrical resistance than the current path passing through the light emitter being included in the plurality of light emitters and being situated in the surrounding region.

Each of the plurality of light emitters may include a first distributed Bragg reflector (DBR) layer that is electrically connected to the first electrode; a second DBR layer that is electrically connected to the second electrode; a current confinement layer that is arranged between the first DBR layer and the second DBR layer; and an active layer that is arranged between the first DBR layer and the second DBR layer, and emits light due to current on which confinement has been performed by the current confinement layer,.

Each of the plurality of light emitters may have a mesa structure in which at least the first DBR layer, the current confinement layer, and the active layer of the light emitter of the plurality of light emitters are spaced from at least the first DBR layer, the current confinement layer, and the active layer of the adjacent light emitter of the plurality of light emitters, and
the size of the aperture diameter may differ depending on a size of a mesa diameter.

Wiring that connects the first electrode terminal and one of the plurality of light emitters may exhibit an electrical resistance different from an electrical resistance of wiring that connects the first electrode terminal and another of the plurality of light emitters.

The light-emitting element may have a central region and a surrounding region, as viewed from a direction extending in parallel with the optical axis, the central region including the light emitter situated in an inner portion of the plurality of light emitters, the surrounding portion including the light emitter situated in an outer portion of the plurality of light emitters, and
wiring that connects the first electrode terminal and the light emitter being included in the plurality of light emitters and being situated in the central region may exhibit an electrical resistance different from an electrical resistance of wiring that connects the first electrode terminal and the light emitter being included in the plurality of light emitters and being situated in the surrounding region.

The wiring connecting the first electrode terminal and the light emitter being included in the plurality of light emitters and being situated in the central region may exhibit a higher electrical resistance than the wiring connecting the first electrode terminal and the light emitter being included in the plurality of light emitters and being situated in the surrounding region.

The wiring connecting the first electrode terminal and the light emitter being included in the plurality of light emitters and being situated in the central region may be longer than the wiring connecting the first electrode terminal and the light emitter being included in the plurality of light emitters and being situated in the surrounding region.

The plurality of light emitters may be arranged in a plurality of lines, and
the light emitters of the plurality of light emitters in each of the plurality of lines may be connected to a corresponding one of a plurality of the pieces of wiring each extending from the first electrode.

The plurality of the pieces of wiring may include wiring that extends from the first electrode terminal to the central region through the surrounding region, and wiring that extends from the first electrode terminal to the surrounding region, and
the wiring extending to the central region and the wiring extending to the surrounding region may exhibit different electrical resistances.

The wiring extending to the surrounding region may have a larger cross-sectional area than the wiring extending to the central region.

The first electrode included in the one of the plurality of light emitters may exhibit a contact resistance different from a contact resistance of the first electrode included in the other of the plurality of light emitters.

Each of the plurality of light emitters may include a first DBR layer that is electrically connected to the first electrode; a second DBR layer that is electrically connected to the second electrode; a current confinement layer that is arranged between the first DBR layer and the second DBR layer; and an active layer that is arranged between the first DBR layer and the second DBR layer, and emits light due to current on which confinement has been performed by the current confinement layer,.

One of the plurality of light emitters has a light extraction efficiency different from a light extraction efficiency of another of the plurality of light emitters.

The light-emitting element may have a central region and a surrounding region, as viewed from a direction extending in parallel with the optical axis, the central region including the light emitter situated in an inner portion of the plurality of light emitters, the surrounding portion including the light emitter situated in an outer portion of the plurality of light emitters, and
the light emitter being included in the plurality of light emitters and being situated in the central region may have a lower light extraction efficiency than the light emitter being included in the plurality of light emitters and being situated in the surrounding region.

A surface coating layer may be formed on a light exiting surface of each of the plurality of light emitters, and
the surface coating layer of the one of the plurality of light emitters may have a thickness different from a thickness of the surface coating layer of the other of the plurality of light emitters.

A surface coating layer that includes a first region and a second region may be provided on a light exiting surface of each of the plurality of light emitters, the second region having optical characteristics different from optical characteristics of the first region, and
a position of a boundary between the first region and the second region in the one of the plurality of light emitters may be different from a position of a boundary between the first region and the second region in the other of the plurality of light emitters.

Each of the plurality of light emitters may include a first DBR layer that is electrically connected to the first electrode; a second DBR layer that is electrically connected to the second electrode; a current confinement layer that is arranged between the first DBR layer and the second DBR layer; and an active layer that is arranged between the first DBR layer and the second DBR layer, and emits light due to current on which confinement has been performed by the current confinement layer, and
reflectance of the first DBR layer of the one of the plurality of light emitters and reflectance of the second DBR layer of the one of the plurality of light emitters may be respectively different from reflectance of the first DBR layer of the other of the plurality of light emitters and reflectance of the second DBR layer of the other of the plurality of light emitters.

A distribution of light-emission intensities of the plurality of light emitters from the central region to the surrounding region may have a shape represented by cosnθ.

In order to achieve the object described above, a ranging apparatus according to an embodiment of the present technology includes a light-emitting unit, a light-receiving unit, and a ranging calculation section.

The light-emitting unit includes a light-emitting element including.

The light-receiving unit detects reflected light that is light exiting the light-emitting unit.

The ranging calculation section calculates a distance to a measurement target on the basis of a result of the detection performed by the light-receiving unit.

A ranging apparatus according to embodiments of the present technology is described.

<FIG> is a block diagram illustrating a configuration of a ranging apparatus <NUM> according to the present embodiment. As illustrated in the figure, the ranging apparatus <NUM> includes a light-emitting unit <NUM>, a light emission controller <NUM>, a light-receiving unit <NUM>, and a ranging calculation section <NUM>.

The light-emitting unit <NUM> irradiates a measurement target P with irradiation light LI of which the brightness is periodically changed. When a light-emission control signal S is supplied by the light emission controller <NUM>, the light-emitting unit <NUM> generates the irradiation light LI in synchronization with the light-emission control signal S. The configuration of the light-emitting unit <NUM> will be described later.

The light emission controller <NUM> controls a light emission of the light-emitting unit <NUM>. The light emission controller <NUM> generates a light-emission control signal S, and supplies the generated light-emission control signal S to the light-emitting unit <NUM> and the light-receiving unit <NUM>. The light-emission control signal S may be, for example, a square wave of a frequency of <NUM>.

The light-receiving unit <NUM> receives reflected light LR that is the light LI reflected off the measurement target P, and detects an amount of light received. The light-receiving unit <NUM> receives a vertical synchronization signal, and can detect the amount of light received in a period of the vertical synchronization signal every time the period elapses. The vertical synchronization signal is, for example, a periodic signal of <NUM>. The light-receiving unit <NUM> includes light-receiving elements arranged in a two-dimensional grid, and supplies the ranging calculation section <NUM> with image data G that corresponds to an amount of light received by each light-receiving element.

The ranging calculation section <NUM> calculates a distance from the light-receiving unit <NUM> to the measurement target P on the basis of the image data G supplied by the light-receiving unit <NUM>. The ranging calculation section <NUM> can generate a depth map M in which a distance between each light-receiving element and the measurement target P is represented by a gradation value.

<FIG> is a schematic diagram illustrating a positional relationship between the light-emitting unit <NUM>, the light-receiving unit <NUM>, and the measurement target P. As illustrated in the figure, the light-emitting unit <NUM> and the light-receiving unit <NUM> are adjacently arranged, and a distance between the light-emitting unit <NUM> and the light-receiving unit <NUM> is, for example, about a few millimeters. A distance between each of the light-emitting unit <NUM> and the light-receiving unit <NUM>, and the measurement target P may be from about several tens of centimeters to about a few meters. As described later, the light-emitting unit <NUM> according to the present embodiment can irradiate the irradiation light LI for a long distance, and this enables a long-distance measurement.

Hereinafter, a Z direction represents a direction of an optical axis corresponding to the irradiation light LI, and an X direction and a Y direction represent directions that are orthogonal to the Z direction and orthogonal to each other, as illustrated in <FIG>.

<FIG> is a schematic diagram illustrating a configuration of the light-emitting unit <NUM>. As illustrated in the figure, the light-emitting unit <NUM> includes a light-emitting element <NUM>, a light-emitting-element support <NUM>, a base <NUM>, a collimator lens <NUM>, and a lens support <NUM>.

The light-emitting element <NUM> includes a plurality of light emitters. <FIG> is a perspective view of the light-emitting element <NUM>. As illustrated in the figure, the light-emitting element <NUM> includes a plurality of light emitters 111a two-dimensionally arranged in a direction (X-Y direction) orthogonal to the optical-axis direction (Z direction). Further, the light emitters 111a may be arranged in a line in parallel with a direction in an X-Y plane, that is, the light emitters 111a may be one-dimensionally arranged.

The light-emitting element <NUM> is fixed to the base <NUM> through the light-emitting-element support <NUM>, as illustrated in <FIG>. The collimator lens <NUM> is supported by the lens support <NUM>, and collimates the exiting light LI (forms the exiting light LI into parallel light).

<FIG> is a schematic diagram illustrating the irradiation light LI exiting the light-emitting unit <NUM>. The irradiation light LI exits each light emitter 111a, and then is collimated by the collimator lens <NUM> to be formed into a beam, as illustrated in the figure. The formation of the irradiation light LI into a beam enables the irradiation light LI to reach far. Further, the orientation of a light beam passing through a peripheral portion of the collimator lens <NUM> is tilted by the light beam passing through the collimator lens <NUM>. This makes it possible to perform irradiation onto a wider range.

Note that the configuration of the light-emitting unit <NUM> is not limited thereto. For example, a diffraction grating (a diffractive optical element: DOE) may be arranged ahead of the collimator lens <NUM> to diffract the irradiation light LI for tiling. This makes it possible to increase the number of irradiation spots, and to further make the irradiation range wider.

Each of the plurality of light emitters 111a included in the light-emitting element <NUM> is a vertical-cavity surface-emitting laser (VCSEL) element. <FIG> is a cross-sectional view of a portion of the light-emitting element <NUM>, and illustrates three light emitters 111a. <FIG> is a cross-sectional view of the three light emitters 111a, and an illustration of a portion of a configuration of the light-emitting element <NUM> is omitted.

As illustrated in <FIG> and <FIG>, the light-emitting element <NUM> includes a substrate <NUM>, an n-DBR layer <NUM>, an n-cladding layer <NUM>, an active layer <NUM>, a p-cladding layer <NUM>, a current confinement layer <NUM>, a p-DBR layer <NUM>, a contact layer <NUM>, an insulation layer <NUM>, a p-electrode <NUM>, and an n-electrode <NUM>.

The substrate <NUM> supports each layer of the light-emitting element <NUM>. The substrate <NUM> may be, for example, an n-Gas substrate, or may be made of another material.

The n-DBR layer <NUM> is provided on the substrate <NUM>, and serves as a distributed Bragg reflector (DBR) off which light of a wavelength λ is reflected. The n-DBR layers <NUM> forms a resonator for lasing together with the p-DBR layer <NUM>.

The n-DBR layer <NUM> may be formed by alternately stacking a low-refractive-index layer and a high-refractive-index layer multiple times. The low-refractive-index layer is made of, for example, n-type Alx1Ga<NUM>-X1As (<NUM><X1<<NUM>), and the high-refractive-index layer is made of, for example, n-type Alx2Ga<NUM>-x2As (<NUM><X2<X1).

The n-cladding layer <NUM> is stacked on the n-DBR layer <NUM>, and is a layer that confines light and current in the active layer <NUM>. The n-cladding layer <NUM> is made of, for example, n-type Alx3Ga<NUM>-x3As (<NUM><X3<<NUM>).

The active layer <NUM> is provided on the n-cladding layer <NUM>, and emits spontaneous-emission light and amplifies the spontaneous-emission light. The active layer <NUM> is made of, for example, undoped InX4Ga<NUM>-X4As or Alx4Ga<NUM>-x4As (<NUM><X4<<NUM>).

The p-cladding layer <NUM> is provided on the active layer <NUM>, and is a layer that confines light and current in the active layer <NUM>. The p-cladding layer <NUM> is made of, for example, p-type Alx5Ga<NUM>-x5As (<NUM><X5<<NUM>).

The current confinement layer <NUM> is provided on the p-cladding layer <NUM>, and has a confinement effect on current. As illustrated in <FIG>, the current confinement layer <NUM> has a confinement region 126a and an injection region 126b. The confinement region 126a is made of, for example, oxidized AlAs, and has a low conductivity and a low refractive index. The confinement region 126a serves as a light confining region. The injection region 126b is made of, for example, an unoxidized AlAs, and is a region having a higher conductivity than the confinement region 126a.

The p-DBR layer <NUM> is provided on the current confinement layer <NUM>, and serves as a DBR off which light of a wavelength λ is reflected. The p-DBR layers <NUM> forms a resonator for lasing together with the n-DBR layers <NUM>.

The p-DBR layer <NUM> may be formed by alternately stacking a low-refractive-index layer and a high-refractive-index layer multiple times. The low-refractive-index layer is made of, for example, p-type Alx1Ga<NUM>-X6As (<NUM><X6<<NUM>), and the high-refractive-index layer is made of, for example, p-type Alx7Ga<NUM>-x7As (<NUM><X7<X6).

The contact layer <NUM> is provided on the p-DBR layer <NUM>, and is a layer to which the p-electrode <NUM> is joined. The contact layer <NUM> is made of, for example, p-type GaAs or p-type Alx8Ga<NUM>-x8As (<NUM><X8<<NUM>).

As illustrated in <FIG>, the light emitter 111a includes a portion of the n-DBR layer <NUM>, the n-cladding layer <NUM>, the active layer <NUM>, the p-cladding layer <NUM>, the current confinement layer <NUM>, the p-DBR layer <NUM>, and the contact layer <NUM>, and is spaced from an adjacent light emitter 111a using a separation groove C. The light emitter 111a has a mesa (flat-topped shape) structure.

The insulation layer <NUM> is formed on an inner peripheral surface of the separation groove C, as illustrated in <FIG>, and insulates the adjacent light emitters 111a. The insulation layer <NUM> is made of, for example, SiO<NUM>.

The p-electrode <NUM> is formed on the contact layer <NUM> and the insulation layer <NUM>, and serves as a p-electrode of each light emitter 111a. The p-electrode <NUM> is made of any conductive material.

The n-electrode <NUM> is formed on the substrate <NUM>, and serves as an n-electrode of each light emitter 111a. The n-electrode <NUM> is made of any conductive material.

<FIG> illustrates one light emitter 111a, as viewed from a light exiting direction (Z direction). As illustrated in the figure, a peripheral portion of the surface of the contact layer <NUM> is covered with the p-electrode <NUM>. A central portion of the surface of the contact layer <NUM> is not covered with the p-electrode <NUM>, and is a surface from which laser light generated by the light emitter 111a exits. As illustrated in <FIG> and <FIG>, this surface is hereinafter referred to as a "light exiting surface H". Note that a surface coating layer used to control optical characteristics may be provided to the light exiting surface H, as described later.

<FIG> is a plan view of a front surface of the light-emitting element <NUM>. As illustrated in the figure, an anode <NUM> is provided as a "first electrode terminal" at each of two ends of the front surface of the light-emitting element <NUM>. The anode <NUM> is a portion to which a drive source of the light-emitting element <NUM> is connected by, for example, wire bonding, and the p-electrode <NUM> included in each light emitter 111a is connected to the anode <NUM>. The configuration of the anode <NUM> is not limited to the configuration illustrated in <FIG>, and any configuration that makes it possible to electrically connect the drive source and the p-electrode <NUM> may be adopted.

<FIG> is a plan view of a back surface of the light-emitting element <NUM>. As illustrated in the figure, a cathode <NUM> is provided as a "second electrode terminal" on the back surface of the light-emitting element <NUM>. The cathode <NUM> is a portion to which ground wiring of the light-emitting element <NUM> is connected by solder connection or using a conductive paste, and the n-electrode <NUM> included in each light emitter 111a is connected to the cathode <NUM>. The configuration of the cathode <NUM> is not limited to the configuration illustrated in <FIG>, and any configuration that makes it possible to electrically connect the ground of the light-emitting element <NUM> and the n-electrode <NUM> may be adopted.

The light-emitting element <NUM> has the configuration described above. Note that the configuration of the light-emitting element <NUM> is not limited thereto, and any configuration in which each light emitter 111a serves as a VCSEL may be adopted. For example, the light-emitting element <NUM> may be a VCSEL in which the light-emitting direction is a direction of the substrate, that is, a so-called back exit VCSEL.

When voltage is applied between the anode <NUM> and the cathode <NUM>, current flows through each light emitter 111a from the p-electrode <NUM> to the n-electrode <NUM>. Due to a confinement effect of the current confinement layer <NUM>, the current is injected through the injection region 126b.

Due to the injected current, spontaneous-emission light is generated in a region, in the active layer <NUM>, that is adjacent to the injection region 126b. The spontaneous-emission light travels in a stacking direction of the light-emitting element <NUM> (Z direction), and is reflected off the n-DBR layer <NUM> and the p-DBR layer <NUM>.

The n-DBR layer <NUM> and the p-DBR layer <NUM> are configured such that light of an oscillation wavelength λ is reflected off the n-DBR layer <NUM> and the p-DBR layer <NUM>. From among the spontaneous-emission light, a component of the oscillation wavelength λ forms a standing wave between the n-DBR layer <NUM> and the p-DBR layer <NUM>, and is amplified by the active layer <NUM>.

When a value of the injected current exceeds a threshold, light forming a standing wave is lased, and is transmitted through the p-cladding layer <NUM>, the current confinement layer <NUM>, the p-DBR layer <NUM>, and the contact layer <NUM> to exit from the light exiting surface H. Consequently, light corresponding to an optical axis of which a direction is the Z-axis direction exits each light emitter 111a, and light LI corresponding to an optical axis of which a direction is the Z-axis direction exits the light-emitting unit <NUM> (refer to <FIG>).

In the ranging apparatus <NUM>, the irradiation light LI exits the light-emitting unit <NUM>, and the light-receiving unit <NUM> receives the reflected light LR reflected off the measurement target P to measure a distance to the measurement target P, as described above. <FIG> is a schematic diagram illustrating an angle of incidence of the reflected light LR.

The light-emitting element <NUM> according to the present embodiment is configured such that the intensities of the pieces of irradiation light LI emitted by the respective light emitters 111a (hereinafter referred to as light-emission intensities) are not uniform, and the pieces of irradiation light LI have a specified distribution of a light-emission intensity. If the respective light emitters 111a have a uniform light-emission intensity, irradiation spots formed by the collimator lens <NUM> will also have a uniform brightness.

Here, the light-receiving unit <NUM> has the property of having a higher light-receiving sensitivity for light that enters from a wide angle of field (reflected light LR1 in <FIG>) than for light that enters from a narrow angle of field (reflected light LR2 in <FIG>). Thus, when irradiation spots have a uniform brightness, there may be a reduction in the accuracy in ranging performed with respect to a surrounding region in a measurement-target range.

<FIG> is a plan view of the light-emitting element <NUM> according to the present embodiment, as viewed from a direction (Z direction) extending in parallel with an optical axis corresponding to exiting light. As illustrated in the figure, the front surface of the light-emitting element <NUM> is divided into a plurality of regions referred to as a first region A<NUM>, a second region A<NUM>, and a third region A<NUM>.

The first region A<NUM> includes the light emitter 111a situated in an inner portion of a plurality of light emitters 111a, and is a region situated in a central portion of the light-emitting element <NUM>. The third region A<NUM> includes the light emitter 111a in an outer portion of the plurality of light emitters 111a, and is a region situated in a surrounding portion of the light-emitting element <NUM>. The second region A<NUM> is a region between the first region A<NUM> and the third region A<NUM>, and includes the light emitter 111a situated between the first region A<NUM> and the third region A<NUM>.

The light-emitting element <NUM> is configured such that the third region A<NUM> exhibits a highest light-emission intensity, the second region A<NUM> exhibits a second highest light-emission intensity, and the first region A<NUM> exhibits a lowest light-emission intensity, as described later. This makes it possible to compensate for a reduction in the light-receiving sensitivity for light that enters the light-receiving unit <NUM> from a wide angle of field (the reflected light LR1 in <FIG>) and to prevent a reduction in the accuracy in ranging performed with respect to a surrounding region in a measurement-target range.

In <FIG>, the first region A<NUM> to the third region A<NUM> are distributed in two directions that are the X-direction and the Y-direction, that is, in a two-dimensional manner. However, the first region A<NUM> to the third region A<NUM> may be distributed only in the X-direction, that is, in a one-dimensional manner.

<FIG> is a plan view of the one-dimensionally distributed first to third regions A<NUM> to A<NUM>. As illustrated in the figure, the first region A<NUM> may be a region situated in a central portion of the light-emitting element <NUM>, the third region A<NUM> may be a region situated in a surrounding portion of the light-emitting element <NUM>, and the second region A<NUM> may be a region situated between the first region A<NUM> and the third region A<NUM>.

Note that, in the following description, the light emitter 111a included in the first region A<NUM> is referred to as a first light emitter 111a<NUM>, the light emitter 111a included in the second region A<NUM> is referred to as a second light emitter 111a<NUM>, and the light emitter 111a included in the third region A<NUM> is referred to as a third light emitter 111a<NUM>. The number of first light emitters 111a<NUM>, the number of second light emitters 111a<NUM>, and the number of third light emitters 111a<NUM> are not particularly limited.

The light-emitting element <NUM> has the following configuration in order to make a difference in the light-emission intensity of the light emitter 111a between the first region A<NUM>, the second region A<NUM>, and the third region A<NUM>. Note that the number of regions into which the light-emitting element <NUM> is divided is not limited to the example described above.

As described above, each light emitter 111a is electrically connected to the anode <NUM> and the cathode <NUM>, and a current path from the anode <NUM> to the cathode <NUM> that passes through each light emitter 111a is formed between the anode <NUM> and the cathode <NUM>.

<FIG> is a circuit diagram illustrating an equivalent circuit of a current path in one light emitter 111a. In the figure, Vcc (a power-supply potential) is a potential of the anode <NUM>, and GND (a ground potential) is a potential of the cathode <NUM>. A resistance Rf is a resistance between the light emitter 111a and the anode <NUM>, and a resistance Rb is a resistance between the light emitter 111a and the cathode <NUM>. As illustrated in the figure, a current path from the anode <NUM> to the cathode <NUM> that passes through the light emitter 111a is referred to as a current path E, and a resistance of the current path E is referred to as a path resistance RE.

<FIG> is a circuit diagram illustrating an equivalent circuit of current paths of the first light emitter 111a<NUM>, the second light emitter 111a<NUM>, and the third light emitter 111a<NUM>. As illustrated in the figure, a current path from the anode <NUM> to the cathode <NUM> that passes through the first light emitter 111a<NUM> is referred to as a first current path E<NUM>. Likewise, a current path that passes through the second light emitter 111a<NUM> is referred to as a second current path E<NUM>, and a current path that passes through the third light emitter 111a<NUM> is referred to as a third current path E<NUM>.

As illustrated in <FIG>, the resistance Rf in the first current path E<NUM> is referred to as a resistance Rf<NUM>, the resistance Rf in the second current path E<NUM> is referred to as a resistance Rf<NUM>, and the resistance Rf in the third current path E<NUM> is referred to as a resistance Rf<NUM>. Further, the resistance Rb in the first current path E<NUM> is referred to as a resistance Rb<NUM>, the resistance Rb in the second current path E<NUM> is referred to as a resistance Rb<NUM>, and the resistance Rb in the third current path E<NUM> is referred to as a resistance Rb<NUM>.

A resistance of the entirety of the first current path E<NUM> is obtained by summing the resistance Rf<NUM> and the resistance Rb<NUM>, and a resistance of the entirety of the second current path E<NUM> is obtained by summing the resistance Rf<NUM> and the resistance Rb<NUM>. A resistance of the entirety of the third current path E<NUM> is obtained by summing the resistance Rf<NUM> and the resistance Rb<NUM>. Hereinafter, the resistance of the entirety of the first current path E<NUM> is referred to as a first path resistance RE1, the resistance of the entirety of the second current path E<NUM> is referred to as a second path resistance RE2, and the resistance of the entirety of the current path E<NUM> is referred to as a third path resistance RE3.

A current path in a region, on the front surface of the light-emitting element <NUM>, that is situated closer to the center of the front surface exhibits a higher resistance. In other words, the first path resistance RE1, the second path resistance RE2, and the third path resistance RE3 are different from each other, where the first path resistance RE1 is higher than the second path resistance RE2, and the second path resistance RE2 is higher than the third path resistance RE3.

A larger current flows through a current path exhibiting a lower path resistance RE, and this results in the light emitter 111a exhibiting a higher light-emission intensity. Thus, the third light emitter 111a<NUM> exhibits a highest light-emission intensity, the second light emitter 111a<NUM> exhibits a second highest light-emission intensity, and the first light emitter 111a<NUM> exhibits a lowest light-emission intensity.

This makes it possible to compensate for a reduction in the light-receiving sensitivity for light (the reflected light LR1 in <FIG>) that enters the light-receiving unit <NUM> from a wide angle of field, and to prevent a reduction in the accuracy in ranging performed with respect to a surrounding region in a measurement-target range.

A specific method for making a difference between the first path resistance RR1, the second path resistance RE2, and the third path resistance RE3 is described below.

In the light-emitting element <NUM>, it is possible to make a difference in a resistance of a current path by controlling an internal resistance of each light emitter 111a using an aperture diameter (an optical aperture (OA) diameter) of the light emitter 111a.

<FIG> is a cross-sectional view of a portion of the configuration of the light emitter 111a, and illustrates an OA diameter D. As illustrated in the figure, the OA diameter D is a diameter of the injection region 126b of the current confinement layer <NUM>. In the light emitter 111a, current applied to the light emitter 111a is injected through the injection region 126b, and spontaneous-emission light is generated in a region, in the active layer <NUM>, that is adjacent to the injection region 126b. In other words, the injection region 126b serves as an optical aperture.

<FIG> is a graph illustrating a relationship between voltage and current for each OA diameter of the light emitter 111a. As indicated by an arrow in the figure, voltage necessary to cause the same amount of current to flow is reduced as the OA diameter is increased.

<FIG> is a graph illustrating a relationship between current and light output for each OA diameter of the light emitter 111a. As indicated by an arrow in the figure, a saturation light output is increased as the OA diameter is increased, but the light output remains unchanged with the same amount of current regardless of the OA diameter when the light output is smaller than the saturation light output.

<FIG> is a graph illustrating a relationship between voltage and light output for each OA diameter of the light emitter 111a. As indicated by an arrow in the figure, light output at the same voltage is increased as the OA diameter is increased.

Thus, in the light-emitting element <NUM>, the OA diameter of the light emitter 111a differs between regions that are the first region A<NUM> to the third region A<NUM>, and this makes it possible to control a level of difficulty in current flowing due to voltage, that is, a resistance of the light emitter 111a, and to make a difference in the path resistance RE.

Specifically, the OA diameter of the third light emitter 111a<NUM> is made largest, the OA diameter of the second light emitter 111a<NUM> is made second largest, and the OA diameter of the first light emitter 111a<NUM> is made smallest. <FIG> a schematic diagram illustrating the OA diameters D of the first light emitter 111a<NUM> to the third light emitter 111a<NUM>. As illustrated in the figure, an OA diameter D<NUM> of the third light emitter 111a<NUM> is larger than an OA diameter D<NUM> of the second light emitter 111a<NUM>, and the OA diameter D<NUM> of the second light emitter 111a<NUM> is larger than an OA diameter D<NUM> of the first light emitter 111a<NUM>. For example, the OA diameter D<NUM> may be <NUM>, the OA diameter D<NUM> may be <NUM>, and the OA diameter D<NUM> may be <NUM>.

Consequently, the first path resistance RE1 is highest, the second path resistance RE2 is second highest, and the third path resistance RE3 is lowest. Accordingly, the third light emitter 111a<NUM> exhibits a highest light-emission intensity, the second light emitter 111a<NUM> exhibits a second highest light-emission intensity, and the first light emitter 111a<NUM> exhibits a lowest light-emission intensity.

A method for changing the width of the confinement region 126a measuring from an outer periphery of the mesa structure is a method for making a difference in OA diameter between the light emitters 111a. <FIG> is a schematic diagram illustrating a difference in the width of the confinement region 126a. As illustrated in the figure, the width of the confinement region 126a of the first light emitter 111a<NUM> is referred to as a width Wai, the width of the confinement region 126a of the second light emitter 111a<NUM> is referred to as a width Wa<NUM>, and the width of the confinement region 126a of the third light emitter 111a<NUM> is referred to as a width Wa<NUM>.

Note that widths Wb of the mesa structures of the respective light emitters 111a are the same. Here, the OA diameter D<NUM> can be made largest and the OA diameter D<NUM> can be made smallest by making the width Wa<NUM> smaller than the width Wa<NUM> and by making the width Wa<NUM> smaller than the width Wa<NUM>.

The confinement region 126a can be formed by performing an oxidation treatment after layers that form the current confinement layer <NUM> are stacked. In this case, it is possible to make a difference in the width of the confinement region 126a between the first region A<NUM> to the third region A<NUM> by adjusting the time for the oxidation treatment or another condition for the oxidation treatment.

Further, a method for changing the diameter of the mesa structure (hereinafter referred to as a mesa diameter) is another method for making a difference in OA diameter between the light emitters 111a. <FIG> is a schematic diagram illustrating a difference in mesa diameter. As illustrated in the figure, the mesa diameter of the first light emitter 111a<NUM> is referred to as a diameter Wbi, the mesa diameter of the second light emitter 111a<NUM> is referred to as a diameter Wb<NUM>, and the mesa diameter of the third light emitter 111a<NUM> is referred to as a diameter Wb<NUM>.

Note that widths Wa of the confinement regions 126a of the respective light emitters 111a are the same. Here, the OA diameter D<NUM> can be made largest and the OA diameter D<NUM> can be made smallest by making the diameter Wb<NUM> larger than the diameter Wb<NUM> and by making the diameter Wb<NUM> larger than the diameter Wb<NUM>.

The diameter of the mesa structure can be adjusted by the position at which the separation groove C (refer to <FIG>) is formed or by the width of the separation groove C. This method makes it possible to change the OA diameter, with the widths Wa of the confinement regions 126a of the first region A<NUM> to the third region A<NUM> being the same. This makes it possible to adopt the same condition of oxidization treatment performed to form the confinement regions 126a of the first region A<NUM> and the third region A<NUM>.

Further, it is also possible to make a difference in the OA diameter of the light emitter 111a between the first region A<NUM> to the third region A<NUM> by changing both the width Wa of the confinement region 126a and the mesa diameter Wb.

In the light-emitting element <NUM>, for example, a wiring electrode structure in which electrodes are arranged in separate lines is adopted instead of the structure including electrodes that uniformly cover the entirety of the light-emitting element <NUM>, in order to connect the anode <NUM> and the p-electrode <NUM> included in each light emitter 111a, and it is possible to make a difference between the first path resistance RR1, the second path resistance RE2, and the third path resistance RE3 using an electrical resistance of the wiring.

<FIG> is a schematic diagram illustrating wiring L that connects the light emitters 111a and the anodes <NUM> situated at two ends of the light-emitting element <NUM>. As illustrated in the figure, the light emitters 111a are arranged in a plurality of lines in the X direction. A plurality of pieces of wiring L extends in the X direction from the anodes <NUM> situated at the two ends, and the light emitters 111a in each line are connected to the wiring L in series. Note that the wiring L may be the p-electrode <NUM> formed between the light emitters 111a in <FIG>. However, the wiring L may be a conductive member different from the p-electrode <NUM>.

In this configuration, the light-emission intensity of the third region A<NUM> can be made highest and the light-emission intensity of the first region A<NUM> can be made lowest when the first region A<NUM>, the second region A<NUM>, and the third region A<NUM> are one-dimensionally arranged, as illustrated in <FIG>. In each piece of wiring L, the wiring L between the anode <NUM> and the second region A<NUM> is referred to as a wiring portion La, and the wiring L between the first region A<NUM> and the third region A<NUM> is referred to as a wiring portion Lb, as illustrated in <FIG>. Further, the wiring L between the second regions A<NUM> is referred to as a wiring portion Lc.

The wiring L exhibits some resistance, although the wiring L is made of a conductive material. Hereinafter, the resistance of the wiring portion La is referred to as a resistance RLa, and the resistance of the wiring portion Lb is referred to as a resistance RLb.

<FIG> is a circuit diagram of the light-emitting element <NUM>. As illustrated in the figure, the third path resistance RE3 corresponding to the resistance of the third current path E<NUM> is obtained by summing the resistance Rf<NUM> and resistance Rb<NUM>. On the other hand, the second path resistance RE2 corresponding to the resistance of the second current path E<NUM> is obtained by summing the resistance RLa, the resistance Rf<NUM>, and the resistance Rb<NUM>, since there is the wiring portion La in a current path between the anode <NUM> and the second light emitter 111a<NUM>.

Further, the first path resistance RE1 corresponding to the resistance of the first current path E<NUM> is obtained by summing the resistance RLa, the resistance Rf<NUM>, and the resistance Rb<NUM>, since there are the wiring portion La and the wiring portion Lb in a current path between the anode <NUM> and the first light emitter 111a<NUM>.

As described above, the wiring L between the anode <NUM> situated at each of the two ends and the third light emitter 111a<NUM> adjacent to the anode <NUM> is short, and the third path resistance RE3 is low. On the other hand, the wiring L (the wiring portion La) between the anode <NUM> situated at each of the two ends and the second light emitter 111a<NUM> situated away from the anode <NUM> is long, and the second path resistance RE2 is high.

Further, the wiring L (the wiring La + the wiring Lb) between the anode <NUM> situated at each of the two ends and the first light emitter 111a<NUM> situated farthest away from the anode <NUM> is longer, and the first path resistance RE1 is highest. As described above, it is possible to make a difference in the path resistance RE between regions by making a difference between the first region A<NUM>, the second region A<NUM>, and the third region A<NUM> in the length of the wiring L situated between the anode <NUM> and the light emitter 111a.

Note that the wiring L does not necessarily have to have the same cross-sectional area. For example, the wiring portion La may have a larger cross-sectional area than the wiring portion Lb, and the wiring portion Lb may have a larger cross-sectional area than the wiring portion Lc. The cross-sectional area of the wiring L can be adjusted by changing at least one of a width or a thickness of the wiring L.

Further, in the light-emitting element <NUM>, it is also possible to make the light-emission intensity of the third region A<NUM> highest and to make the light-emission intensity of the first region A<NUM> lowest when the first region A<NUM>, the second region A<NUM>, and the third region A<NUM> are two-dimensionally arranged, as illustrated in <FIG>. <FIG> is a schematic diagram illustrating the wiring L connecting the light emitters 111a and the anodes <NUM> situated at two ends of the light-emitting element <NUM>. As illustrated in the figure, the light emitters 111a are arranged in a plurality of lines in the X direction, and a plurality of pieces of wiring L extends in the X direction from the anodes <NUM> situated at the two ends. The light emitters 111a in each line are connected to the wiring L in series.

Here, the wiring L includes wiring L1, wiring L2, and wiring L3. The wiring L1 is wiring that passes through the third region A<NUM> and the second region A<NUM> to extend to the first region A<NUM>, and the wiring L2 is wiring that passes through the third region A<NUM> to extend to the second region A<NUM>. The wiring L3 is wiring that extends to the third region A<NUM>. Note that the number of pieces of wiring L1, the number of pieces of wiring L2, and the number of pieces of wiring L3 may be set discretionarily, and are not limited to the numbers illustrated in <FIG>.

The wiring L1, the wiring L2, and the wiring L3 exhibit different electrical resistances, where the wiring L3 exhibits a lowest electrical resistance, and the wiring L1 exhibits a highest electrical resistance. The electrical resistances of the wiring L1, the wiring L2, and the wiring L3 can be controlled by their cross-sectional areas, where the wiring L3 may have a larger cross-sectional area than the wiring L2, and the wiring L2 may have a larger cross-sectional area than the wiring L1.

The cross-sectional area of the wiring L can be adjusted by changing at least one of a width or a thickness of the wiring L. As illustrated in <FIG>, the wiring L may have a uniform thickness, the wiring L3 may have a greater width than the wiring L2, and the wiring L2 may have a greater width than the wiring L1.

Further, the wiring L may have a uniform width, the wiring L3 may have a greater thickness than the wiring L2, and the wiring L2 may have a greater thickness than the wiring L1. Moreover, both the thickness and the width of the wiring L can be adjusted such that the wiring L3 has a larger cross-sectional area than the wiring L2, and the wiring L2 has a larger cross-sectional area than the wiring L1. Note that the wiring L is not limited to three types of wiring that are the wiring L1, the wiring L2, and the wiring L3 of different cross-sectional areas, and the wiring L may be two types of wiring, or four or more types of wiring.

In this configuration, in the X direction in which the wiring L extends, the path resistance RE in the central portion is increased using the length of the wiring L connecting each light emitter 111a and the anode <NUM>. Further, in the Y direction, the path resistance RE in the central portion is increased using a difference in the electrical resistance of the wiring L. Thus, the first path resistance RE1 can be made highest, the second path resistance RE2 can be made second highest, and the third path resistance RE3 can be made lowest when the first region A<NUM>, the second region A<NUM>, and the third region A<NUM> are two-dimensionally arranged.

As described above, the light-emitting element <NUM> in which a surrounding region (the third region A<NUM>) exhibits a higher light-emitting intensity than a central region (the first region A<NUM>) can be provided by making a difference in the path resistance RE between the first region A<NUM>, the second region A<NUM>, and the third region A<NUM> using a resistance of the wiring L. In this configuration, the respective light emitters 111a have the same configuration. Thus, it is possible to form a distribution of a light-emission intensity only by changing the wiring width, with conditions for producing the respective light emitters 111a being the same.

Note that <FIG> and <FIG> illustrate an example of providing the wiring L connecting a plurality of light emitters 111a. However, a planar electrode (a solid-pattern electrode) may be provided instead of the wiring L. In this case, it is possible to make a difference in path resistance by the wiring resistances from the anode <NUM> to the respective light emitters 111a being different.

Further, in the light-emitting element <NUM>, it is also possible to make a difference in the path resistance RE using a contact resistance in each light emitter 111a, that is, a resistance between a semiconductor and a metal interface.

<FIG> is a cross-sectional view of the light emitter 111a. The area of contact of the p-electrode <NUM> with the contact layer <NUM> can be changed by adjusting a width Wp of the p-electrode <NUM> in contact with the contact layer <NUM>, as illustrated in <FIG> and <FIG>. This makes it possible to increase or decrease the resistance Rf (refer to <FIG>) in the light emitter 111a, and to make a difference between the first path resistance RR1, the second path resistance RE2, and the third path resistance RE3.

Specifically, the width Wp in the third light emitter 111a<NUM> may be set to be a specified width to set the resistance Rf<NUM> (refer to <FIG>). Further, the width Wp in the second light emitter 111a<NUM> may be smaller than the width Wp in the third light emitter 111a<NUM> such that the resistance Rf<NUM> exhibits a larger value than the resistance Rf<NUM>. Furthermore, the width Wp in the first light emitter 111a<NUM> may be smaller than the width Wp in the second light emitter 111a<NUM> such that the resistance Rf<NUM> exhibits a larger value than the resistance Rf<NUM>.

Further, the resistance Rf can also be increased or decreased by changing the shape of the p-electrode <NUM> and adjusting the area of contact of the p-electrode <NUM> with the contact layer <NUM>, in addition to controlling the width Wp.

Furthermore, the resistance Rb (refer to <FIG>) can be increased or decreased by adjusting a depth M of the separation groove C (refer to <FIG>), as illustrated in <FIG>, and this makes it possible to make a difference between the first path resistance RR1, the second path resistance RE2, and the third path resistance RE3.

Specifically, the depth M of the separation groove C situated around the third light emitter 111a<NUM> may be set to be a specified depth to set the resistance Rb<NUM> (refer to <FIG>). Further, the depth M of the separation groove C situated around the second light emitter 111a<NUM> may be greater than the depth M of the separation groove C situated around the third light emitter 111a<NUM> such that the resistance Rb<NUM> exhibits a larger value than the resistance Rb<NUM>. Furthermore, the depth M of the separation groove C situated around the first light emitter 111a<NUM> may be greater than the depth M of the separation groove C situated around the second light emitter 111a<NUM> such that the resistance Rb<NUM> exhibits a larger value than the resistance Rb<NUM>.

Further, both the widths Wp and the depths M of the first light emitter 111a<NUM>, the second light emitter 111a<NUM>, and the third light emitter 111a<NUM> can also be changed such that the first path resistance RR1 is highest and the third path resistance RE3 is lowest.

The above-described adjustment of the width Wp and the depth M makes it possible to make a difference in the path resistance RE between the first region A<NUM>, the second region A<NUM>, and the third region A<NUM>. Such a configuration also makes it possible to form a distribution of a light-emission intensity only using the shape of the p-electrode <NUM> or the depth of the separation groove C, with the respective light emitters 111a having a uniform stacking structure.

As described above, the light-emitting element <NUM> in which the surrounding region (the third region A<NUM>) exhibits a higher light-emitting intensity than the central region (the first region A<NUM>) can be provided using a difference in the path resistance RE between the first region A<NUM>, the second region A<NUM>, and the third region A<NUM>.

Note that, with respect to the method for making a difference in the path resistance RE between the first path resistance RR1, the second path resistance RE2, and the third path resistance RE3, only one of the control performed using an OA diameter, the control performed using a wiring resistance, and the control performed using a contact resistance described above may be used, or two or more thereof may be used in combination. For example, a one-dimensional distribution of a light-emission intensity (refer to <FIG>) can be formed by performing the control by a wiring resistance, and then a two-dimensional distribution of a light-emission intensity (refer to <FIG>) can be formed by performing the control by an OA diameter.

Further, the light-emitting element <NUM> in which the first path resistance RR1 is highest, the second path resistance RE2 is second highest, and the third path resistance RE3 is lowest can also be provided by a method, such as changing a material of the wiring L, that is different from the respective methods described above.

In the light-emitting element <NUM>, it is possible to make a difference in light-emission intensity between the first region A<NUM>, the second region A<NUM>, and the third region A<NUM> (refer to <FIG>) by controlling the light extraction efficiency of the light emitter 111a. Note that, when a difference in light-emission intensity is made due to the light extraction efficiency of the light emitter 111a, the above-described path resistances of the light emitters 111a may be the same.

Specifically, in the light-emitting element <NUM>, the light extraction efficiencies of the light emitters 111a in the first region A<NUM>, the second region A<NUM>, and the third region A<NUM> are different from each other, and the light emitter 111a has a higher light extraction efficiency in a region, on the front surface of the light-emitting element <NUM>, that is situated closer to the center of the front surface. In other words, the third light emitter 111a<NUM> has a highest light extraction efficiency, the second light emitter 111a<NUM> included in the second region A<NUM> has a second highest light extraction efficiency, and the first light emitter 111a<NUM> has a lowest light extraction efficiency. Consequently, the third region A<NUM> exhibits a highest light-emission intensity, the second region A<NUM> exhibits a second highest light-emission intensity, and the first region A<NUM> exhibits a lowest light-emission intensity.

This makes it possible to compensate for a reduction in the light-receiving sensitivity for light (the reflected light LR1 in <FIG>) that enters the light-receiving unit <NUM> from a wide angle of field, and to prevent a reduction in the accuracy in ranging performed with respect to a surrounding region in a measurement-target range, as described above.

A specific structure that makes a difference in the light extraction efficiency of the light emitter 111a is described below.

In the light-emitting element <NUM>, it is possible to make a difference in the light extraction efficiency of the light emitter 111a using a thickness of a surface coating layer included in each light emitter 111a.

<FIG> is an enlarged cross-sectional view of the light emitter 111a, and illustrates a surface coating layer <NUM> that is included in the light emitter 111a. As illustrated in the figure, the surface coating layer <NUM> is formed on the contact layer <NUM>. The surface coating layer <NUM> is an optical thin film used to control the reflectance of the light exiting surface H, and may be made of, for example, SiN. The change of a thickness T of the surface coating layer <NUM> makes it possible to change a threshold current and the slope efficiency, and this results in changing light output with a specific current value.

<FIG> is a graph illustrating an example of a relationship between the thickness T of the surface coating layer <NUM> and light output. As illustrated in the figure, due to the thickness T of the surface coating layer <NUM>, light output of the light emitter 111a is changed, that is, the light extraction efficiency can be adjusted. Note that <FIG> illustrates an example in which light output is reduced due to the thickness T being increased, but the light extraction efficiency may be periodically changed due to the thickness T, and the reduction in the thickness T may result in an increase in light output.

In the light-emitting element <NUM>, it is possible to make the light extraction efficiency in the third region A<NUM> is highest, to make the light extraction efficiency in the second region A<NUM> is second highest, and to make the light extraction efficiency in the first region A<NUM> lowest by making a difference in the thickness T of the surface-coding layer <NUM> between the first light emitter 111a<NUM>, the second light emitter 111a<NUM>, and the third light emitter 111a<NUM>.

Consequently, the third region A<NUM> exhibits a highest light-emission intensity, the second region A<NUM> exhibits a second highest light-emission intensity, and the first region A<NUM> exhibits a lowest light-emission intensity. This makes it possible to provide the light-emitting element <NUM> in which the surrounding region exhibits a higher light-emitting intensity than the central region. In this configuration, the respective light emitters 111a have the same configuration except for the thickness of the surface coating layer <NUM>. Thus, it is possible to form a distribution of a light-emission intensity by preparing the thickness of the surface coating layer <NUM>, with conditions for producing the respective light emitters 111a being the same.

In the light-emitting element <NUM>, it is also possible to make a difference in the light extraction efficiency of the light emitter 111a using a position of a boundary in surface coating layers of each light emitter 111a.

<FIG> is an enlarged cross-sectional view of the light emitter 111a, and illustrates a surface coating layer <NUM> and a surface coating layer <NUM> that are included in the light emitter 111a. As illustrated in (a) and (b) of <FIG>, the surface coating layer <NUM> is formed on the contact layer <NUM>, and the surface coating layer <NUM> is formed on a partial region of the surface coating layer <NUM>. The surface coating layer <NUM> and the surface coating layer <NUM> are optical thin films used to control the reflectance of the light exiting surface H, and may be made of, for example, SiN.

A region, on the light exiting surface H, in which the surface coating layer <NUM> and the surface coating layer <NUM> are formed is referred to as a region Ha, and a region, on the light exiting surface H, in which only the surface coating layer <NUM> is formed is referred to as a region Hb. Further, a boundary between the region Ha and the region Hb is referred to as a boundary K.

<FIG> is a schematic diagram illustrating the region Ha and the region Hb, where (a) of <FIG> is a plan view of (a) of <FIG>, and (b) of <FIG> is a plan view of (b) of <FIG>. In the light emitter 111a, an oscillation mode of light can be switched by the position of the boundary K, and a threshold current and the slope efficiency can be changed. Thus, it is possible to make the light extraction efficiency in the third region A<NUM> highest, to make the light extraction efficiency in the second region A<NUM> second highest, and to make the light extraction efficiency in the first region A<NUM> lowest by making a difference in a position of the boundary K between the first light emitter 111a<NUM>, the second light emitter 111a<NUM>, and the third light emitter 111a<NUM>, as illustrated in (a) and (b) of <FIG> and (a) and (b) of <FIG>.

Consequently, the third region A<NUM> exhibits a highest light-emission intensity, the second region A<NUM> exhibits a second highest light-emission intensity, and the first region A<NUM> exhibits a lowest light-emission intensity. This makes it possible to provide the light-emitting element <NUM> in which the surrounding region exhibits a higher light-emitting intensity than the central region. Also in this configuration, the respective light emitters 111a have the same configuration except for the configurations of the surface coating layers. Thus, it is possible to form a distribution of a light-emission intensity by preparing the position of a boundary in surface coating layers, with conditions for producing the respective light emitters 111a being the same.

Note that the region Ha and the region Hb are not limited to regions of which the numbers of surface coating layers are different. The region Ha and the region Hb may be regions of which the surface coating layers have different optical characteristics, such as regions of which the surface coating layers have different thicknesses, or regions of which the surface coating layers are made of different materials. The number of regions is also not limited to two, and may be three or more.

In the light-emitting element <NUM>, it is also possible to make a difference in the light extraction efficiency of the light emitter 111a using one of the reflectance of the n-DBR layer <NUM> and the reflectance of the p-DBR layer <NUM>, or both of them.

As described above, when voltage is applied between the anode <NUM> and the cathode <NUM> in the light emitter 111a, spontaneous-emission light emitted by the active layer <NUM> is reflected off the n-DBR layer <NUM> and the p-DBR layer <NUM>, and is lased to be emitted from the light exiting surface H. Thus, the light extraction efficiency in the third region A<NUM> can be made highest, the light extraction efficiency in the second region A<NUM> can be made second highest, and the light extraction efficiency in the first region A<NUM> can be made lowest by making a difference in the reflectance of the n-DBR layer <NUM> and the reflectance of the p-DBR layer <NUM> in the light emitter 111a between the first light emitter 111a<NUM>, the second light emitter 111a<NUM>, and the third light emitter 111a<NUM>.

Consequently, the third region A<NUM> exhibits a highest light-emission intensity, the second region A<NUM> exhibits a second highest light-emission intensity, and the first region A<NUM> exhibits a lowest light-emission intensity. This makes it possible to provide the light-emitting element <NUM> in which the surrounding region exhibits a higher light-emitting intensity than the central region.

As described above, the light-emitting element <NUM> in which the surrounding region exhibits a higher light-emitting intensity than the central region can be provided using a difference in light extraction efficiency between the first region A<NUM>, the second region A<NUM>, and the third region A<NUM>.

Note that, with respect to the method for making a difference in light extraction efficiency between the first light emitter 111a<NUM>, the second light emitter 111a<NUM>, and the third light emitter 111a<NUM>, only one of the control performed using a thickness of a surface coating layer, the control performed using a position of a boundary in surface coating layers, and the control performed using a DBR layer reflectance described above may be used, or two or more thereof may be used in combination.

Further, the light-emitting element <NUM> in which the light extraction efficiency in the third region A<NUM> is highest, the light extraction efficiency in the second region A<NUM> is second highest, and the light extraction efficiency in the first region A<NUM> is lowest can also be provided by a method that is different from the respective methods described above.

An example of a distribution of a light-emission intensity of the light-emitting element <NUM> is described. <FIG> is a graph illustrating an example of a distribution of a light-emission intensity of the light-emitting element <NUM>. As illustrated in the figure, the distribution of a light-emission intensity of the light emitter <NUM> shows that the first region A<NUM> corresponding to the central region exhibits a low light-emission intensity, and the third region A<NUM> corresponding to the surrounding region exhibits a high light-emission intensity.

Here, the distribution of a light-emission intensity illustrated in <FIG> has a shape represented by cos-<NUM>θ. The distribution of a light-emission intensity of the light-emitting element <NUM> is not limited to having the shape represented by cos-<NUM>θ, and it is favorable that the distribution of a light-emission intensity of the light-emitting element <NUM> have a shape represented by cosnθ. <FIG> are graphs respectively illustrating other examples of the distribution of a light-emission intensity of the light-emitting element <NUM>.

The distribution of a light-emission intensity may have a shape represented by cos-<NUM>θ, as illustrated in <FIG>, or may have a shape represented by cos-<NUM>θ, as illustrated in <FIG>. Further, the distribution of a light-emission intensity may have a shape represented by cos-<NUM>θ, as illustrated in <FIG>.

Further, the distribution of a light-emission intensity of the light-emitting element <NUM> is not limited to being curved, as illustrated in <FIG>. <FIG> are schematic diagrams respectively illustrating other examples of the distribution of a light-emission intensity of the light-emitting element <NUM>. As illustrated in the figures, the light-distribution of a light-emission intensity of the light-emitting element <NUM> may have a step shape that approximates the shape represented by cosnθ.

As described above, in the light-emitting element <NUM>, the light-emission intensity in the third region A<NUM> can be made highest, the light-emission intensity in the second region A<NUM> can be made second highest, and the light-emission intensity in the first region A<NUM> can be made lowest by controlling a resistance of a current path that passes through each light emitter 111a or the efficiency in extracting light emitted by each light emitter 111a. This makes it possible to compensate for a reduction in the light-receiving sensitivity for light (the reflected light LR1 in <FIG>) that enters the light-receiving unit <NUM> from a wide angle of field, and to prevent a reduction in the accuracy in ranging performed with respect to a surrounding region in a measurement-target range. Further, there is no need to add a component, to increase component costs, and to make a component larger in size, in order to obtain such a distribution of a light-emission intensity.

Further, it is possible to form a distribution of a light-emission intensity using a difference in path resistance or a difference in light extraction efficiency, with the respective light emitters 111a being connected to the anode <NUM> and the cathode <NUM> in common. In other words, there is no need to adjust applied power by an anode and a cathode being connected to each individual light emitter 111a, in order to form the distribution of a light-emission intensity. Consequently, there is no need to arrange a plurality of drive sources for the light emitters 111a, and this makes it possible to prevent component costs from being increased due to such an arrangement and to prevent the ranging apparatus <NUM> from becoming larger in size due to such an arrangement.

Furthermore, the present technology is also effective when an anode and a cathode are connected to each individual light emitter 111a, and the respective light emitters 111a are individually driven. There is a possibility that a driver that drives each light emitter 111a will not have a parameter used to set power for the light emitter 111a, or only a unified parameter can be used. Even in such a case, it is possible to form the distribution of a light-emission intensity in the light-emitting element <NUM> by supplying equivalent power to the anode <NUM> and the cathode <NUM> for each light emitter 111a.

In the embodiments described above, there is a difference in the light-emission intensity of the light emitter 111a between three regions that are the first region A<NUM>, the second region A<NUM>, and the third region A<NUM> (refer to <FIG>). However, the number of regions is not limited to three, and the number of regions may be two or four or more. The light-emitting element <NUM> in which a surrounding region of the light-emitting element <NUM> exhibits a high light-emitting intensity and a central region of the light-emitting element <NUM> exhibits a low light-emitting intensity regardless of the number of regions, makes it possible to prevent a reduction in the accuracy in ranging performed with respect to a surrounding region in a measurement-target range of the light-receiving unit <NUM>.

Further, the example in which, in the light-emitting element <NUM>, the n-type portion is situated on the side of the substrate <NUM> (a lower side in <FIG>), and the p-type portion is situated on the side of the light exiting surface H (an upper side in <FIG>) has been described above, but the positions of the n-type portion and the p-type portion may reverse. Furthermore, a high-resistance substrate may be used as the substrate <NUM>, a p-type layer and an n-type layer may be provided on the substrate <NUM>, and both of the electrodes may be taken out of one side of the substrate <NUM>. Further, the light-emitting element <NUM> may be a back exit VCSEL in which the light-emitting direction is a direction of the substrate. Furthermore, the example of a GaAs substrate has been described in the embodiments above, but a GaN substrate or an InP substrate may be used depending on a target light-emission wavelength.

In addition, the example in which the light-emitting element <NUM> is included in the light-emitting unit <NUM> of the ranging apparatus <NUM> has been described above, but the light-emitting element <NUM> is not limited thereto. For example, the light-emitting element <NUM> may also be used as a light source for structured light of the ranging apparatus, or may be applied to uniform irradiation performed without using a diffusion plate.

Further, the light-emitting element <NUM> can also be used as a light source for illumination in addition to being used for the ranging apparatus. The light-emission wavelength may correspond to infrared light, ultraviolet light, or visible light, and the light-emitting element <NUM> can also be applied to exposure. In this case, it is also possible to correct for the angular dependence of the transmittance of an optical section (such as a lens) in an illumination optical system (the light intensity in a surrounding portion that light enters obliquely is also easily reduced in this case).

Claim 1:
A light-emitting element (<NUM>), comprising:
a plurality of light emitters (111a) one-dimensionally or two-dimensionally arranged in a direction that is vertical to an optical axis corresponding to light that exits each of the plurality of light emitters, each of the plurality of light emitters being a vertical-cavity surface-emitting laser element, each of the plurality of light emitters including a first electrode (<NUM>) and a second electrode (<NUM>), each of the plurality of light emitters emitting the light due to current flowing from the first electrode to the second electrode;
a first electrode terminal (<NUM>) that is electrically connected to the first electrode; and
a second electrode terminal (<NUM>) that is electrically connected to the second electrode, wherein
a first current path from the first electrode terminal to the second electrode terminal that passes through a first one of the plurality of light emitters exhibits a first electrical resistance different from a second electrical resistance of a second current path from the first electrode terminal to the second electrode terminal that passes through a second one of the plurality of light emitters, wherein the first and second current paths are parallel circuit paths.