Patent Description:
A known distance measuring apparatus for measuring the distance to an object scans the object by deflecting illumination light from a light source via a deflection unit, and calculates the distance to the object based on the time until the reception of reflected light from the object and the phase of the reflected light.

Patent Document <NUM> discusses a distance measuring apparatus including a prism that reflects either one of illumination light and reflected light on the inner surface, and reflects the other thereof on the outer surface to guide the illumination light and the reflected light to a deflection unit and a light-receiving element, respectively.

The spread angle of illumination light emitted from a general light source used in a distance measuring apparatus differs between the horizontal and vertical directions. Therefore, shaping of illumination light is required to obtain a favorable distance measurement accuracy. However, in a configuration discussed in Patent Document <NUM> in which illumination light is reflected by the outer surface of a prism, it is difficult to shape the illumination light by using the prism. Therefore, the use of other optical elements is required to shape the illumination light, resulting in an increased complication of the entire apparatus.

On the other hand, in a configuration discussed in Patent Document <NUM> in which illumination light is reflected by the inner surface of the prism, the illumination light can be shaped by using the prism. However, the illumination light passes through many optical surfaces of the prism. Therefore, part of the illumination light is scattered by scratches and foreign objects (sticking substances) on each optical surface of the prism, and the light is incident on a light-receiving element as unnecessary light. This increases the possibility of degradation of the distance measurement accuracy.

The present invention is directed to providing a simply configured optical apparatus capable of preventing the generation of unnecessary light.

To achieve the above-described purpose, according to claim <NUM> of the present invention, an optical apparatus includes a deflection unit configured to deflect illumination light from a light source to scan an object and deflect reflected light from the object, and a guide unit configured to guide the illumination light from the light source to the deflection unit and guide the reflected light from the deflection unit to a light-receiving element, wherein the light guide unit includes a first surface on which the illumination light from the light source is incident and a second surface including a transmissive region through which the illumination light from the first surface is transmitted and a reflective region that reflects the reflected light from the deflection unit, wherein the first and the second surfaces are non-parallel to each other, and wherein the illumination light from the first surface is incident on the transmissive region without being transmitted or reflected by other surfaces.

Preferred exemplary embodiments of the present invention will be described below with reference to the accompanying drawings. For descriptive purposes, each drawing may be illustrated in a scale different from the actual scale. In each drawing, identical members are assigned the same reference numerals, and redundant descriptions thereof will be omitted.

<FIG> schematically illustrates a main portion of an optical apparatus <NUM>, in a cross-section (YZ cross-section) including the optical axis, according to a first exemplary embodiment of the present invention. The optical apparatus <NUM> includes a light source unit <NUM>, a light guide unit (branch unit) <NUM>, a deflection unit <NUM>, a light receiving unit (first light receiving unit) <NUM>, a light receiving unit for light source (second light receiving unit) <NUM>, and a control unit <NUM>. <FIG> illustrates optical paths in the optical apparatus <NUM>, including an optical path (illumination optical path) along which the illumination light from the light source unit <NUM> travels toward an object <NUM>, and an optical path (light receiving optical path) along which the reflected light from the object <NUM> travels toward the light receiving unit <NUM>.

The optical apparatus <NUM> receives the reflected light from the object <NUM> to serve as a detection apparatus (imaging apparatus) for detecting (capturing) the object <NUM> or as a distance measuring apparatus for acquiring the distance (distance information) to the object <NUM>. The optical apparatus <NUM> according to the first exemplary embodiment employs a technique called Light Detection and Ranging (LiDAR) for calculating the distance to the object <NUM> based on the time until the reception of the reflected light from the object <NUM> and the phase of the reflected light.

The light source unit <NUM> includes a light source <NUM>, an optical element <NUM>, and a diaphragm <NUM>. The light source <NUM> may be a semiconductor laser device having a high energy concentration and a high directivity. When applying the optical apparatus <NUM> to an on-vehicle system (described below), the object <NUM> may possibly include the human body. Therefore, it is desirable to employ, as the light source <NUM>, a light source that emits infrared light having a small influence on the human eyes. The illumination light emitted by the light source <NUM> according to the present exemplary embodiment has a wavelength of <NUM> which is contained in the near-infrared region.

<FIG> schematically illustrates a general semiconductor laser device and a light beam emitted therefrom. As illustrated in <FIG>, an active layer <NUM> of the semiconductor laser device as the light source <NUM> emits a divergent light beam having an elliptic shape in the xy cross-section parallel to the exit surface (light emitting surface) of the active layer <NUM>. If the semiconductor laser <NUM> is of a linearly polarized light type, the polarization direction of the light beam (oscillation direction of the electric field) is a direction parallel to the upper and lower surfaces of the active layer <NUM>, i.e., in a direction in the zx cross-section.

The optical element <NUM> has a function of changing the convergence of the illumination light emitted from the light source <NUM>. The optical element <NUM> according to the present exemplary embodiment is a collimator lens (light condensing element) that converts (collimates) the divergent light beam emitted from the light source <NUM> into a parallel light beam. The parallel light beam in this case includes not only a strict parallel light beam but also an approximate parallel light beam such as a weak divergent light beam and a weak convergent light beam.

The diaphragm <NUM>, which is a light-shielding member having an opening, determines the light beam diameter (light beam width) by limiting the illumination light from the optical element <NUM>. The opening of the diaphragm <NUM> according to the present exemplary embodiment has an elliptic shape to match the shape of the illumination light. However, the opening shape is not limited thereto but may be other than an ellipse as required. The opening diameter of the diaphragm <NUM> according to the present exemplary embodiment is <NUM> in the X-axis direction (major axis direction) and <NUM> in the Z-axis direction (minor axis direction).

As illustrated in <FIG>, the light guide unit <NUM> is a light guide member for branching an optical path into an illumination optical path and a light receiving optical path, guiding the illumination light from the light source unit <NUM> to the deflection unit <NUM>, and guiding the reflected light from the deflection unit <NUM> to the light receiving unit <NUM>. The light guide unit <NUM> according to the present exemplary embodiment includes a single branching optical element (prism) <NUM> made of a single material. Desirably, the material of the branching optical element <NUM> has a sufficiently high transmissivity with respect to the wavelength of the illumination light. More specifically, the material provides a refractive index of at least <NUM> with respect to a <NUM> wavelength. The material of the branching optical element <NUM> according to the present exemplary embodiment is TAFD55 from HOYA Corporation, having a refractive index of <NUM> with respect to a <NUM> wavelength.

<FIG> schematically illustrates a main portion of the branching optical element <NUM> according to the present embodiment, illustrating the invention. The branching optical element <NUM> has a plurality of optical surfaces (a first surface <NUM>, a second surface <NUM>, and a third surface <NUM>) that transmit and reflect a light beam. <FIG> illustrates a cross-section (YZ cross-section) perpendicular to each optical surface of the branching optical element <NUM>, and the second surface <NUM> thereof viewed from the normal direction. According to the present embodiment, in the YZ cross-section, an angle α<NUM> formed by the first surface <NUM> and the second surface <NUM> is <NUM>°, and an angle α<NUM> formed by the first surface <NUM> and the third surface <NUM> is <NUM>°.

The first surface <NUM> is an optical surface on which the illumination light from the light source unit <NUM> is incident. As described above, since the shape of the opening of the diaphragm <NUM> is an ellipse, the shape of a passage region (light incident region) <NUM> that transmits the illumination light on the first surface <NUM> is also an ellipse. The first surface <NUM> includes a total reflection region <NUM> in a region other than the passage region <NUM> for transmitting the illumination light from the light source unit <NUM>. The total reflection region <NUM> totally reflects the light reflected by the second surface <NUM> to guide the light to the third surface <NUM>. If necessary, there may be provided an antireflection film for reducing the reflectance to improve the transmissivity at the portion corresponding to the passage region <NUM>, and a reflection film at the portion corresponding to the total reflection region <NUM>.

The second surface <NUM> includes a transmissive region <NUM> that transmits the illumination light from the first surface <NUM> and a reflective region <NUM> that reflects the reflected light from the deflection unit <NUM>. The transmissive region <NUM> according to the present exemplary embodiment has an elliptic shape, the shape is not limited thereto. For example, if the light guide unit <NUM> shapes the illumination light so that its cross-section has a circular shape, the transmissive region <NUM> may accordingly have a circular shape. The transmissive region <NUM> may be provided with an antireflection film. The reflective region <NUM> according to the present exemplary embodiment is provided with a reflection film (reflection layer) made of a metal or dielectric. It is desirable that the bottom portion (bottom layer) of the reflection film is provided with an absorption layer for absorbing the light from the inside of the branching optical element <NUM>.

The illumination light that passed through the opening of the diaphragm <NUM> enters the branching optical element <NUM> from the first surface <NUM>, penetrates the transmissive region <NUM> on the second surface <NUM>, and travels toward the deflection unit <NUM>. As described above, the present exemplary embodiment is configured to allow the illumination light to enter the branching optical element <NUM> and then guide the light to the deflection unit <NUM>. This makes it possible to shape the illumination light by the refractive action of the first surface <NUM> and the second surface <NUM>. Thus, even if the spread angles (divergent angles) of the illumination light from the light source unit <NUM> are different between the X- and the Z-directions, the optical apparatus <NUM> can obtain a favorable distance measurement accuracy (detection accuracy).

The following assumes a case where, like the above-described Patent Document <NUM>, the illumination light is reflected by the outer surface of the branching optical element and then is guided to the deflection unit. In this case, since the illumination light from the light source unit travels toward the deflection unit only through the outer surface of the branching optical element, the outer surface of the branching optical element needs to be made nonspherical (anamorphic) to shape the illumination light by using the branching optical element. In this configuration, however, the reflected light from the object is also incident on the outer surface of the branching optical element. Accordingly, the reflected light is affected by the aspheric surface action, resulting in a difficulty in obtaining a favorable distance measurement accuracy.

Alternatively, there is assumed a method for shaping the illumination light by disposing another optical element only in the illumination light path between the outer surface and the deflection unit. However, this increases the number of components in the optical apparatus, resulting in the increase in the complexity and size of the entire apparatus. Therefore, to obtain a favorable distance measurement accuracy while reducing the complexity and size of the optical apparatus, it is desirable to enable the illumination light to enter the branching optical element and have the illumination light guided to the deflection unit through a plurality of optical surfaces of the branching optical element, as is the case with the present exemplary embodiment.

In addition, the present inventive embodiment is configured to directly guide the illumination light that has entered the branching optical element <NUM> from the first surface <NUM> to the transmissive region <NUM> on the second surface <NUM> without using other surfaces. This configuration enables shaping the illumination light by using the minimum number of optical surfaces, i.e., the first surface <NUM> and the second surface <NUM>, of the branching optical element <NUM>. This enables reducing the possibility of the illumination light becoming partly scattered by scratches and foreign objects on each optical surface and turning into unnecessary light that enters the light receiving unit <NUM>.

An on-vehicle system (described below) is required to detect, as the object <NUM>, an object existing in a range between a short distance (approximately <NUM>) from the optical apparatus <NUM> and a long distance (approximately <NUM>) therefrom. However, the intensity of the reflected light (signal light) from the object <NUM> decreases with increasing distance from the optical apparatus <NUM> to the object <NUM>. For example, if the distance from the optical apparatus <NUM> to the object <NUM> is increased by <NUM> times, the intensity of the reflection light received by the optical apparatus <NUM> decreases by approximately <NUM>/<NUM> times.

Therefore, when measuring the distance of the object <NUM> at the long distance, in particular, the above-described unnecessary light largely affects the distance measurement accuracy. For example, in a case where the ratio of the unnecessary light to the signal light received by the light receiving unit <NUM> increases, it becomes difficult to distinguish between the signal light and the unnecessary signal, largely decreasing the distance measurement accuracy. There is assumed a method for increasing the light quantity of the illumination light (the output of the light source <NUM>) in accordance with the increase in the distance to the object <NUM>. However, this method is not desirable because of the large influence of the object <NUM> on the human eyes.

On the other hand, the optical apparatus <NUM> having a simple configuration according to the present exemplary embodiment enables preventing the generation of unnecessary light without increasing the light quantity of the illumination light, thus achieving a favorable distance measurement accuracy. The optical apparatus <NUM> according to the present exemplary embodiment makes it possible to accurately acquire the distance information for the object <NUM> even when an infrared sensor having a lower sensitivity than a visible light sensor is used as the light receiving unit <NUM>.

It is desirable that the branching optical element <NUM> is configured to change (vary) the diameter of the illumination light from the light source unit <NUM>. According to the present exemplary embodiment, when the illumination light penetrates the first surface <NUM> and the second surface <NUM>, the diameter of the illumination light in the YZ cross-section is enlarged by refraction. More specifically, in the YZ cross-section, the diameter of the illumination light emitted from the transmissive region <NUM> is larger than the diameter of the illumination light incident on the first surface <NUM>.

Since the spread angle of the illumination light can be reduced by increasing the diameter of the illumination light in this way, sufficient illuminance and resolution can be ensured even when the object <NUM> is far away. In the present exemplary embodiment, although only the light beam diameter in the YZ cross-section is enlarged to correspond to the elliptic shape of the illumination light from the light source unit <NUM>, the present invention is not limited to this configuration. The light beam diameter in the YZ cross-section may be reduced, or the light beam diameter in a cross-section perpendicular to the YZ cross-section may be varied depending on the shape of the illumination light and the required detection information.

In the YZ cross-section, the illumination light that enters the first surface 211has a diameter h<NUM> (diameter of the diaphragm <NUM>) and the illumination light that exits the transmissive region <NUM> has a diameter h<NUM> (diameter of the transmissive region <NUM>). Here, an incident angle of the illumination light incident on the first surface <NUM> is θ<NUM> [°], a refraction angle of the illumination light refracted on the first surface <NUM> is θ<NUM> [°], an incident angle of the illumination light incident on the transmissive region <NUM> is θ<NUM> [°], and a refraction angle of the illumination light refracted on the transmissive region <NUM> is θ<NUM> [°]. In this case, the relation represented by the following Formula (<NUM>) is satisfied based on Snell's law.

The values on both sides of Formula (<NUM>) are larger than <NUM> in a case where the incident angle θ<NUM> to the first surface <NUM> is larger than the refraction angle θ<NUM> to the transmissive region <NUM>. This means that, when the values on both sides of Formula (<NUM>) are larger than <NUM>, the diameter of the illumination light is enlarged by the branching optical element <NUM>. According to the present exemplary embodiment, h<NUM> = <NUM>, h<NUM> = <NUM>, θ<NUM> = <NUM>°, θ<NUM> = <NUM>°, θ<NUM> = <NUM>°, and θ<NUM> = <NUM>°, and the values on both sides of formula (<NUM>) are <NUM>, it can be seen that the illumination light has been enlarged.

The deflection unit <NUM> is a member for deflecting the illumination light from the light guide unit <NUM> to scan the object <NUM> and deflecting the reflected light from the object <NUM> to guide the reflected light to the light guide unit <NUM>. The deflection unit <NUM> according to the present exemplary embodiment includes a single drive mirror (movable mirror) <NUM>. It is desirable that the drive mirror <NUM> is swingable about at least two axes (<NUM>-axis drive mirror) to enable two-dimensional scanning of the object <NUM>. For example, a galvanometer mirror or a Micro Electro Mechanical System (MEMS) mirror can be employed as the drive mirror <NUM>. The drive mirror <NUM> according to the present exemplary embodiment is a MEMS mirror having a swinging angle of ±<NUM>° about the X- and the Y-axes and a swinging frequency of approximately <NUM>.

The light receiving unit (light receiving unit for distance measurement) <NUM> includes an optical filter <NUM>, an optical element <NUM>, and a light-receiving element (light-receiving element for distance measurement) <NUM>. The optical filter <NUM> is a member for transmitting only desired light and blocking (absorbing) other unnecessary light. The optical filter <NUM> according to the present exemplary embodiment is a band-pass filter for transmitting only the light in the wavelength band corresponding to the illumination light emitted from the light source <NUM>. The optical element <NUM> is a condenser lens for condensing the light that passed through the optical filter <NUM> on the light receiving surface of the light-receiving element <NUM>. The configurations of the optical filter <NUM> and the optical element <NUM> are not limited to those according to the present exemplary embodiment. For example, if necessary, the order of the arrangements of the two members may be changed, and a plurality of the respective members may be disposed.

The light-receiving element (first light-receiving element) <NUM> is an element (sensor) for receiving light from the optical element <NUM>, photoelectrically converting the light into a signal, and outputting the signal. The light-receiving element <NUM> made of a photodiode (PD), an avalanche photodiode (APD), or a single photon avalanche diode (SPAD) can be employed. The reflected light from the object <NUM> illuminated by the illumination light is deflected by the deflection unit <NUM> and reflected by the reflective region <NUM> of the branching optical element <NUM>, and then enters the light-receiving element <NUM> via the optical filter <NUM> and the optical element <NUM>.

Part of the illumination light from the first surface <NUM> does not penetrate but reflects off the transmissive region <NUM>. This reflection occurs regardless of the presence or absence of an antireflection film in the transmissive region <NUM>. The light reflected by the transmissive region <NUM> totally reflects off the total reflection region <NUM> on the first surface <NUM>, exits the branching optical element <NUM> from the third surface <NUM>, and then enters the light receiving unit for light source <NUM>.

The light receiving unit for light source <NUM> includes a light-receiving element for light source (second light-receiving element) <NUM> for photoelectrically converting the illumination light from the light source <NUM> into a signal and outputting the signal. For example, a sensor similar to the light-receiving element <NUM> may be used as the light-receiving element for light source <NUM>. If necessary, the light receiving unit for light source <NUM> may include an optical element (filter or lens) for guiding the light from the branching optical element <NUM> to the light receiving surface of the light-receiving element for light source <NUM>.

The control unit <NUM> controls the light source <NUM>, the drive mirror <NUM>, the light-receiving element <NUM>, and the light-receiving element for light source <NUM>. The control unit <NUM> is, for example, a processing apparatus (processor) such as a central processing unit (CPU) or a calculation apparatus (computer) including the processing apparatus. The control unit <NUM> drives each of the light source <NUM> and the drive mirror <NUM> with a predetermined drive voltage and a predetermined drive frequency, and controls the output of the light source <NUM> (the light quantity of the illumination light) based on the signal from the light-receiving element for light source <NUM>. The control unit <NUM> is capable of controlling, for example, the light source <NUM> to change the illumination light to pulsed light, and performing the intensity modulation on the illumination light to generate signal light.

The control unit <NUM> is also capable of acquiring the distance information for the object <NUM> based on the time period since the time (light emission time) when the illumination light is emitted from the light source <NUM> until the time (light reception time) when the light-receiving element <NUM> receives the reflected light from the object <NUM>. In this case, the control unit <NUM> may acquire the signal from the light-receiving element <NUM> at a specific frequency. The control unit <NUM> may acquire the distance information based on the phase of the reflected light from the object <NUM> instead of the time until the reception of the reflected light from the object <NUM>. More specifically, the control unit <NUM> may obtain the difference (phase difference) between the phase of the signal of the light source <NUM> and the phase of the signal output from the light-receiving element <NUM>, and then multiply the phase difference by the velocity of light to acquire the distance information for the object <NUM>.

The optical apparatus <NUM> serving as a LiDAR-based distance measuring apparatus identifies the object <NUM> such as a vehicle, pedestrian, or obstacle, and is preferable for an on-vehicle system that controls a vehicle according to the distance information for the object <NUM>. If LiDAR is used, a coaxial system or a non-coaxial system can be employed. In the coaxial system, the optical axes of the light source unit <NUM> and the light receiving unit <NUM> partially coincide with each other. In the non-coaxial system, the optical axes do not coincide with each other. The optical apparatus <NUM> according to the present exemplary embodiment includes the light guide unit <NUM>, whereby the overall size of the apparatus is reduced and achieves a coaxial system.

Scratches and foreign objects existing in the passage region <NUM> for the illumination light on the first surface <NUM> partly scatter the illumination light and causes scattering light to travel in the direction of an angle different from the angle of the desired illumination light. If this scattering light is incident on the light-receiving element <NUM> as unnecessary light, the distance measurement accuracy may possibly be degraded. A condition for preventing the scattering light generated in the passage region <NUM> from being incident on the light-receiving element <NUM> will be discussed below.

More specifically, scattering light (unnecessary light) incident on the light-receiving element <NUM> is identified by tracing the optical path of the light traveling in the direction opposite to the traveling direction of the reflected light reflected by the reflective region <NUM> on the second surface <NUM> (backward ray tracing). First, divergent light emitted from the light-receiving element <NUM> as a virtual light source (starting point) will be considered below. The divergent light emitted from the light-receiving element <NUM> as the starting point is changed to parallel light by the optical element <NUM>, and reaches the second surface <NUM> via the optical filter <NUM>. The light incident on the reflective region <NUM> on the second surface <NUM> does not reach the passage region <NUM> on the first surface <NUM>, but the light incident on the transmissive region <NUM> on the second surface <NUM> is refracted and reaches the passage region <NUM>.

More specifically, the optical path of the light that is emitted from the light-receiving element <NUM> and reaches the passage region <NUM> on the first surface <NUM> can be considered as an inverse optical path of the optical path of the scattering light to be identified. Thus, when the transmissive region <NUM> is projected onto the first surface <NUM> from the traveling direction of the light emitted from the light-receiving element <NUM> and refracted by the transmissive region <NUM> (refraction angle ω with respect to the transmissive region <NUM>), it is desirable that the projection region and the passage region <NUM> do not overlap with each other. Since, according to the inventive principle, the light emitted from the light-receiving element <NUM> and refracted by the transmissive region <NUM> does not reach the passage region <NUM>, scattering light caused by scratches and foreign objects in the passage region <NUM> can be prevented from being received by the light-receiving element <NUM>.

According to the present inventive embodiment, the traveling direction of the illumination light incident on the passage region <NUM> is parallel to the traveling direction of the reflected light reflected by the reflective region <NUM>. That is, the traveling directions are parallel to each other (Y-direction). More specifically, the light source unit <NUM> and the light receiving unit <NUM> according to the present inventive embodiment are disposed so that the optical axes of the two units are parallel to each other. In this configuration, it is desirable to satisfy the following conditional expression (<NUM>): <MAT> where ts denotes the minimum optical path length (shortest distance) of the illumination light from the passage region <NUM> to the transmissive region <NUM>.

The conditional expression (<NUM>) indicates the condition for the shortest distance ts between the passage region <NUM> and the transmissive region <NUM>, which prevents the overlapping of the passage region <NUM> and the projection region on the first surface <NUM>. Referring to <FIG>, the distance between points A and B is the shortest distance ts between the passage region <NUM> and transmissive region <NUM>. According to the present exemplary embodiment, ts = <NUM>, the value of the left-hand side of the conditional expression (<NUM>), ts/h<NUM>, is <NUM>, and the value of the right-hand side thereof is <NUM>, which satisfy the conditional expression (<NUM>). According to the present exemplary embodiment, this projection region is used as the above-described total reflection region <NUM>.

It is desirable that the light source <NUM> is disposed so that the x axis illustrated in <FIG> coincides with the Z axis illustrated in <FIG>, and the y axis illustrated in <FIG> coincides with the X axis illustrated in <FIG>. Disposing the light source <NUM> in this way enables changing the illumination light incident on the passage region <NUM> on the first surface <NUM> to P-polarized light with the electric field oscillating in the YZ cross-section.

<FIG> illustrates the relation between the incident angle and the reflectance of the P-polarized light with respect to the first surface <NUM> according to the present exemplary embodiment. The reflectance of the P-polarized light on the first surface <NUM> decreases with increasing incident angle with respect to the first surface <NUM> from <NUM>°. Once the reflectance decreases to <NUM>, the reflectance increases. The incident angle when the reflectance of the P-polarized light becomes <NUM> is referred to as Brewster's angle. Brewster's angle θB is represented by the following Formula (<NUM>): <MAT> where N denotes the refractive index of the P-polarized light for the incident medium, and N' denotes the refractive index thereof for the light emitting medium.

By making the illumination light incident on the first surface <NUM> at an incident angle close to Brewster's angle θB, the reflectance of the passage region <NUM> on the first surface <NUM> can be reduced without using an antireflection film. This enables the illumination light to enter the branching optical element <NUM> with a high efficiency in a simple configuration. Therefore, it is desirable that the branching optical element <NUM> satisfies the following conditional expression (<NUM>): <MAT>.

According to the present exemplary embodiment, Brewster's angle for the material of the branching optical element <NUM> is <NUM>°, resulting in θB - θ<NUM> = -<NUM>° which satisfies the conditional expression (<NUM>). Further, it is more desirable that the following conditional expressions (4a) and (4b) are satisfied in this order. <MAT> <MAT>.

The optical apparatus <NUM> according to the present exemplary embodiment enables preventing the generation of unnecessary light even with a simple configuration.

<FIG> schematically illustrates a main portion of an optical apparatus <NUM>, in a cross-section (YZ cross-section) including the optical axis, according to a second exemplary embodiment of the present invention. The optical apparatus <NUM> according to the second exemplary embodiment differs from the optical apparatus <NUM> according to the first exemplary embodiment in that an optical system <NUM> is disposed between the deflection unit <NUM> and an object (not illustrated). Other components are similar to those of the optical apparatus <NUM> according to the first exemplary embodiment, and redundant descriptions thereof will be omitted.

The optical system <NUM> is an optical system (telescope) that enlarges the diameter of the illumination light from the deflection unit <NUM> and reduces the diameter of the reflected light from the object. The optical system <NUM> according to the present exemplary embodiment includes a plurality of optical elements (lenses) having refractive power, and is an afocal system not having refractive power in the overall system. More specifically, the optical system <NUM> includes a first lens <NUM> having positive power and a second lens <NUM> having positive power which are sequentially disposed from the side of the deflection unit <NUM> to the side of the object. The configuration of the optical system <NUM> is not limited thereto and may include three or more lenses as required.

A drive mirror <NUM> according to the present exemplary embodiment is disposed at the position of the incidence pupil of the optical system <NUM>. The absolute value of the optical magnification (horizontal magnification) β of the optical system <NUM> according to the present exemplary embodiment is larger than <NUM> (|β| > <NUM>). The deflection angle of the principal ray of the illumination light emitted from the optical system <NUM> is smaller than the deflection angle of the principal ray of the illumination light deflected by the drive mirror <NUM> and incident on the optical system <NUM>, making it possible to improve the resolution at the time of object detection.

The illumination light from the light source unit <NUM> is deflected by the deflection unit <NUM> via the light guide unit <NUM> and then enlarged according to the optical magnification β by the optical system <NUM> before illuminating the object. The reflected light from the object is reduced by optical system <NUM> in accordance with the optical magnification <NUM>/β and then deflected by the deflection unit <NUM> before reaching the light receiving unit <NUM>.

Disposing the optical system <NUM> on the object side of the deflection unit <NUM> in this way enables the diameter of the illumination light to be enlarged not only by the light guide unit <NUM> but also by the optical system <NUM>. This makes it possible to reduce the spread angle by further extending the diameter of the illumination light, thus ensuring sufficient illuminance and resolution even when the object is far away. Extending the pupil diameter by the optical system <NUM> enables receiving a larger quantity of reflected light from the object, thus improving the distance measurement distance and distance measurement accuracy.

<FIG> schematically illustrates a main portion of an optical apparatus <NUM>, in a cross-section (YZ cross-section) including the optical axis, according to a third exemplary embodiment of the present invention. <FIG> illustrates optical paths in the optical apparatus <NUM>, including an optical path along which the illumination light from the light source unit <NUM> travels toward the object <NUM> and an optical path along which the reflected light from the object <NUM> travels toward the light receiving unit <NUM>. The optical apparatus <NUM> according to the third inventive embodiment differs from the optical apparatus <NUM> according to the first inventive embodiment in the configuration of the light guide unit <NUM> and the layout of the light source unit <NUM> and the light receiving unit for light source <NUM>. Other components are similar to those of the optical apparatus <NUM> according to the first inventive embodiment, and redundant descriptions thereof will be omitted.

The light guide unit <NUM> according to the present exemplary embodiment includes a branching optical element <NUM> having a shape different from that of the branching optical element <NUM> according to the first exemplary embodiment. The optical apparatus <NUM> according to the present inventive embodiment differs from the optical apparatus <NUM> according to the first inventive embodiment in that the traveling direction (Z-direction) of the illumination light entering the light guide unit <NUM> from the light source unit <NUM> is perpendicular to the traveling direction (Y-direction) of the reflected light reflected by the light guide unit <NUM>. More specifically, the light source unit <NUM> and the light receiving unit <NUM> according to the present inventive embodiment are disposed so that the optical axes of the two units are perpendicular to each other.

<FIG> schematically illustrates a main portion of the branching optical element <NUM> according to the present exemplary embodiment. The branching optical element <NUM> has a first surface <NUM> and a second surface <NUM>. <FIG> illustrates a cross-section (YZ cross-section) perpendicular to each optical surface of the branching optical element <NUM>, and the second surface <NUM> thereof viewed from the normal direction. According to the present exemplary embodiment, an angle α<NUM> (not illustrated) formed by the first surface <NUM> and the second surface <NUM> in the YZ cross-section is <NUM>°.

The illumination light that passed through the opening of the diaphragm <NUM> enters the branching optical element <NUM> from the first surface <NUM>, reaches the second surface <NUM> without passing through other surfaces, penetrates the transmissive region <NUM>, and travels toward the deflection unit <NUM>. According to the present exemplary embodiment, h<NUM> = <NUM>, h<NUM> = <NUM>, θ<NUM> = <NUM>°, θ<NUM> = <NUM>°, θ<NUM> = <NUM>°, and θ<NUM> = <NUM>°, and the values on both sides of Formula (<NUM>) are <NUM>. The illumination light is enlarged by the first surface <NUM> and the second surface <NUM>. Part of the illumination light from the first surface <NUM> does not penetrate but reflects off the transmissive region <NUM>, penetrates the transmissive region <NUM> on the first surface <NUM>, exits the branching optical element <NUM>, and is incident on the light receiving unit for light source <NUM>.

Like the first exemplary embodiment, a condition for preventing the scattering light generated in the passage region <NUM> on the first surface <NUM> from being incident on the light-receiving element <NUM> will be discussed. According to the present exemplary embodiment, the traveling direction of the illumination light incident on the passage region <NUM> and the traveling direction of the reflected light reflected by the reflective region <NUM> are perpendicular to each other. In this configuration, it is desirable that the following conditional expression (<NUM>) is satisfied: <MAT> where ti denotes the maximum optical path length (longest distance) of the illumination light from the passage region <NUM> to the transmissive region <NUM>.

Like the conditional expression (<NUM>), the conditional expression (<NUM>) indicates a condition for preventing the projection region formed by projecting the transmissive region <NUM> onto the first surface <NUM> at a refraction angle ω from overlapping with the passage region <NUM>. Referring to <FIG>, the distance between points A and B is the longest distance ti between the passage region <NUM> and the transmissive region <NUM>. According to the present exemplary embodiment, ti = <NUM>, the value of the left-hand side of the conditional expression (<NUM>), t<NUM>/h<NUM>, is <NUM>, and the value of the right-hand side thereof is <NUM>, which satisfy the conditional expression (<NUM>). According to the present exemplary embodiment, the projection region is used as the above-described transmissive region <NUM>.

It is desirable that the light source <NUM> is disposed so that the x axis illustrated in <FIG> coincides with the Y axis illustrated in <FIG>, and the y axis illustrated in <FIG> coincides with the X axis illustrated in <FIG>. Like the first exemplary embodiment, disposing the light source <NUM> in this way enables changing the illumination light incident on the passage region <NUM> on the first surface <NUM> to P-polarized light with the electric field oscillating in the YZ cross-section. According to the present exemplary embodiment, Brewster's angle for the material of the branching optical element <NUM> is <NUM>°, and hence θB - θ<NUM> = -<NUM>°, which satisfies the conditional expression (<NUM>).

Thus, using the branching optical element <NUM> according to the present exemplary embodiment enables preventing the generation of unnecessary light while simplifying the overall apparatus even in the configuration in which the optical axes of the light source unit <NUM> and the light receiving unit <NUM> are perpendicular to each other. Like the second exemplary embodiment, an optical system (telescope) may also be disposed on the object side of the deflection unit <NUM> according to the present exemplary embodiment.

Table <NUM> indicates values related to the above-described formulas according to each exemplary embodiment.

<FIG> illustrates the optical apparatus <NUM> and a configuration of an on-vehicle system (driving assistance apparatus) <NUM> including the optical apparatus <NUM> according to the present exemplary embodiment. The on-vehicle system <NUM> supported by a moving body (moving apparatus), such as an automobile (vehicle), is an apparatus for assisting the driving (control) of the vehicle based on distance information of objects such as obstacles and passengers around the vehicle acquired by the optical apparatus <NUM>. <FIG> schematically illustrates a vehicle <NUM> including the on-vehicle system <NUM>. <FIG> illustrates a case where the distance measurement range (detection range) of the optical apparatus <NUM> is set on the anterior side of the vehicle <NUM>. However, the distance measurement range may be set on the posterior or lateral side of the vehicle <NUM>.

As illustrated in <FIG>, the on-vehicle system <NUM> includes the optical apparatus <NUM>, a vehicle information acquisition apparatus <NUM>, a control apparatus (electronic control unit (ECU)) <NUM>, and a warning device <NUM>. In the on-vehicle system <NUM>, the control unit <NUM> included in the optical apparatus <NUM> has functions of a distance acquisition unit (acquisition unit) and a collision determination unit (determination unit). However, if necessary, the on-vehicle system <NUM> may include the distance acquisition unit and the collision determination unit as different units from the control unit <NUM>. These units may be provided outside the optical apparatus <NUM> (e.g., inside the vehicle <NUM>). Alternatively, the control apparatus <NUM> may be used as the control unit <NUM>.

<FIG> is a flowchart illustrating an example of an operation of the on-vehicle system <NUM> according to the present exemplary embodiment. Operations of the on-vehicle system <NUM> will be described below with reference to the flowchart.

In step S1, an object around the vehicle is illuminated by the light source unit <NUM> of the optical apparatus <NUM>, and based on a signal output by the light receiving unit <NUM> in response to reception of reflected light from the object, distance information of the object is acquired by the control unit <NUM>. In step S2, the vehicle information acquisition apparatus <NUM> acquires vehicle information including the vehicle speed, yaw rate, and steering angle of the vehicle. In step S3, using the distance information acquired in step S <NUM> by the control unit <NUM> and the vehicle information acquired in step S2, it is determined whether the distance to the object falls within a preset range of a set distance.

This makes it possible to determine whether an object exists within the set distance around the vehicle to determine the possibility of a collision between the vehicle and the object. Steps S1 and S2 may be performed in reverse order of the above-described order, or performed in parallel. In a case where an object exists within the set distance, then, in step S4, the control unit <NUM> determines that "there is a possibility of a collision". On the other hand, in a case where no object exists within the set distance, then in step S5, the control unit <NUM> determines that "there is no possibility of a collision".

In a case where the control unit <NUM> determines that "there is a possibility of a collision", the control unit <NUM> notifies the control apparatus <NUM> and the warning device <NUM> of the determination result (transmits the determination result thereto). In step S6, the control apparatus <NUM> controls the vehicle based on the determination result by the control unit <NUM>. In step S7, the warning device <NUM> warns the user (driver) of the vehicle based on the determination result by the control unit <NUM>. At least either one of the control apparatus <NUM> and the warning device <NUM> needs to be notified of the determination result.

The control apparatus <NUM> performs controls including applying the brakes, releasing the accelerator, turning the steering wheel, and generating control signals for generating a braking force in each wheel to restrain the power of the engine and motor. The warning device <NUM> warns the driver by generating an alarm sound, displaying alarm information on the screen of a car navigation system, and applying vibration to the seat belt or steering wheel.

The on-vehicle system <NUM> according to the present exemplary embodiment is capable of performing object detection and distance measurement through the above-described processing, making it possible to avoid a collision between the vehicle and an object. In particular, applying the optical apparatus <NUM> according to each exemplary embodiment to the on-vehicle system <NUM> enables achieving a high distance measurement accuracy, making it possible to perform object detection and collision determination at a high accuracy.

Although, in the present exemplary embodiment, the on-vehicle system <NUM> is applied to driving assistance (collision damage reduction), the present invention is not limited thereto. The on-vehicle system <NUM> may be applied to cruise control (including full speed range adaptive cruise control function) and automatic driving control. The on-vehicle system <NUM> is applicable not only to vehicles such as automobiles but also to moving bodies such as boats and ships, aircrafts, and industrial robots. In addition, the on-vehicle system <NUM> is applicable not only to moving bodies but also to Intelligent Transport Systems (ITS), monitoring systems, and other various apparatuses utilizing object recognition.

While the present invention has specifically been described based on the above-described preferred exemplary embodiments, the present invention is not limited thereto.

For example, if necessary, another optical element may be disposed in the optical path between the light guide unit <NUM> (second surface) and the deflection unit <NUM>. However, to favorably restrict the generation of the above-described unnecessary light, it is desirable that nothing is disposed in the optical path between the light guide unit <NUM> and the deflection unit <NUM> as in each of the above-described exemplary embodiments. In other words, it is desirable to employ a configuration in which the illumination light from the second surface is incident on the drive mirror <NUM> without passing through other surfaces.

Although, in each exemplary embodiment, each member is integrally formed (integrally held), each member may be configured as a separate member. For example, the light source unit <NUM> and the light receiving unit <NUM> may be attachable to and detachable from the light guide unit <NUM> or the deflection unit <NUM>. In this case, the holding member (housing) for holding each member needs to be provided with a connecting portion (binding portion) for connection with each other. To improve the positioning accuracy between the light source unit <NUM> and the light guide unit <NUM>, a diaphragm <NUM> may be provided in the light guide unit <NUM> and held by a holding member commonly used for the branching optical element.

Claim 1:
An optical apparatus (<NUM>; <NUM>; <NUM>) comprising:
a deflection unit (<NUM>) configured to deflect illumination light from a light source (<NUM>) to scan an object (<NUM>) and deflect reflected light from the object (<NUM>); and
a guide unit (<NUM>) configured to guide the illumination light from the light source (<NUM>) to the deflection unit (<NUM>) and guide the reflected light from the deflection unit (<NUM>) to a light-receiving element (<NUM>),
wherein the light guide unit (<NUM>) includes a first surface (<NUM>) on which the illumination light from the light source (<NUM>) is incident and a second surface (<NUM>) including a transmissive region (<NUM>) through which the illumination light from the first surface (<NUM>) is transmitted and a reflective region (<NUM>) that reflects the reflected light from the deflection unit (<NUM>),
wherein the first (<NUM>) and the second (<NUM>) surfaces are non-parallel to each other, and
wherein the illumination light from the first surface (<NUM>) is incident on the transmissive region (<NUM>) without being transmitted or reflected by other surfaces.