JP2021110868A - Light receiving device and electronic system - Google Patents

Abstract

To provide a light receiving device in which spectral characteristics of a filter can be improved without increasing lens length, and an electronic system with a light receiving device.SOLUTION: A light receiving device comprises: a telecentric optical system 11 having a Fresnel surface 14; a filter 12 transmitting light of a predetermined wavelength band from among light passing through the telecentric optical system 11; and an imaging unit 13 photoelectrically converting the light passing through the filter 12. An incident angle of the principal ray when the light transmitted through the telecentric optical system 11 is incident on the filter 12 can be reduced, so that the spectral characteristics of the filter 12 can be improved.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a light receiving device and an electronic system.

ToF (Time of Flight) distance measurement technology that measures the distance to an object based on the time difference between the time when the object is irradiated with light and the time when the reflected light from the object is received is known. Has been done. The ToF distance measurement technology is expected to be used in a wide range of fields such as automatic driving and face recognition.

The ToF type distance measuring light receiving device receives light that has passed through a lens (hereinafter, ToF lens), but it is necessary to make the F value of the ToF lens as small as possible so that even weak light can be received.

Recently, a ToF type light receiving device may be installed in a portable device such as a smartphone for the purpose of face recognition or the like. In smartphones and the like, it is necessary to make the light receiving device as small as possible, and it is required to make the ToF lens thinner.

US Patent Publication US201130250039A1

However, when the ToF lens is made thinner, the refraction angle becomes larger as the distance from the center of the optical axis increases. The light that has passed through the ToF lens is incident on a bandpass filter (hereinafter, simply referred to as a filter), and only the light component in a predetermined wavelength band is extracted and incident on the image sensor. When the ToF lens is made thinner, the CRA (Chief Ray Angle) of the light incident on the filter becomes larger. Here, the CRA is the angle of incidence of the main light beam on the filter, and the angle of incidence in this case is the angle of inclination of the incident surface of the filter from the normal direction.

As the CRA increases, the angle of incidence on the filter also increases, and the spectral characteristics of the filter deteriorate. More specifically, as the CRA increases, the filter transmits light in a frequency band different from the frequency band that should originally transmit. Therefore, light having a wavelength component different from the originally intended wavelength component is incident on the image sensor. As a result, the S / N ratio of the image sensor is lowered, and the distance measurement accuracy is lowered.

To improve the spectral characteristics of the filter, it is necessary to reduce the CRA. In order to reduce the CRA, the light emitted from the ToF lens should be substantially parallel to the optical axis direction, but if the traveling direction of the light beam is changed inside the ToF lens, the lens length will increase. It will be long. In smartphones and the like, it is difficult to use a ToF lens with a long lens length because the installation space is limited.

Therefore, the present disclosure provides a light receiving device and an electronic system capable of improving the spectral characteristics of a filter without increasing the lens length.

In order to solve the above problems, according to the present disclosure, a telecentric optical system having a Fresnel surface and
A filter that transmits light in a predetermined wavelength band from the light that has passed through the telecentric optical system,
Provided is a light receiving device including an imaging unit that photoelectrically converts light that has passed through the filter.

The telecentric optical system is
The front group optical system that diverges the main ray of the incident peripheral luminous flux,
It has a rear group optical system that parallelizes the peripheral luminous flux that has passed through the front group optical system.
The rear group optical system may have the Fresnel surface.

The rear group optical system has a first surface which is arranged to face the front group optical system and a second surface which is arranged to face the filter.
The second surface may be a Fresnel surface.

The degree of curvature of the first surface may be larger than the degree of curvature of the second surface.

The rear group optical system may have a lens whose thickness decreases from the center of the optical axis toward the periphery.

The rear group optical system has a transparent base material having a uniform thickness and has a uniform thickness.
The transparent base material has a third surface arranged on the front group optical system side and a fourth surface arranged on the imaging unit side.
The third surface is a Fresnel surface,
The filter may be a layer coated on the fourth surface.

The telecentric optical system is incident with the reflected light emitted from the light source and reflected by the object.
The filter has Wcut_on as the upper limit wavelength at which the transmittance becomes 50% when light is incident from a direction inclined by a predetermined angle from the normal direction of the filter, and when light is incident from the normal direction of the filter. When the lower limit wavelength at which the transmittance becomes 50% is Wcut_off and the amount of change in the emission wavelength of the light source due to the initial wavelength variation of the light source and the temperature change is Wld, it has a transmission characteristic satisfying Wcut_on-Wcut_off> Wld. You may.

The telecentric optical system may have a glass base material having a rectangular outer shape and a Fresnel surface.

The telecentric optical system may have a resin base material having a rectangular outer shape and a Fresnel surface.

The telecentric optical system has a convex resin base material and a flat glass base material bonded to the resin base material.
The filter may be a layer coated on the surface of the glass substrate.

The telecentric optical system is incident with the reflected light emitted from the light source and reflected by the object.
The light receiving device may have a distance measuring unit that measures the distance to the object by the time difference between the timing when the light source emits light and the timing when the light receiving device receives the reflected light.

According to the present disclosure, a light source that emits light and
A light receiving device that receives the reflected light that is emitted by the light source and reflected by the object.
An electronic system including a support substrate that supports the light source and the light receiving device.
The light receiving device is
Telecentric optics with Fresnel surface and
A filter that transmits light in a predetermined wavelength band from the light that has passed through the telecentric optical system,
An electronic system is provided that includes an imaging unit that photoelectrically converts light that has passed through the filter.

The light receiving device may have a distance measuring unit that measures the distance to the object by the time difference between the timing when the light source emits light and the timing when the light receiving device receives the reflected light.

The telecentric optical system is
The front group optical system that diverges the main ray of the incident peripheral luminous flux,
It has a rear group optical system that parallelizes the main light beam of the peripheral luminous flux that has passed through the front group optical system.
The rear group optical system may have the Fresnel surface.

The rear group optical system has a first surface which is arranged to face the front group optical system and a second surface which is arranged to face the filter.
The second surface may be a Fresnel surface.

The degree of curvature of the first surface may be larger than the degree of curvature of the second surface.

The rear group optical system may have a lens whose thickness decreases from the center of the optical axis toward the periphery.

The rear group optical system has a transparent base material having a uniform thickness and has a uniform thickness.
The transparent base material has a third surface arranged on the front group optical system side and a fourth surface arranged on the imaging unit side.
The third surface is a Fresnel surface,
The filter may be a layer coated on the fourth surface.

The telecentric optical system is incident with the reflected light emitted from the light source and reflected by the object.
The filter has Wcut_on as the upper limit wavelength at which the transmittance becomes 50% when light is incident from a direction inclined by a predetermined angle from the normal direction of the filter, and when light is incident from the normal direction of the filter. When the lower limit wavelength at which the transmittance becomes 50% is Wcut_off and the amount of change in the emission wavelength of the light source due to the initial wavelength variation of the light source and the temperature change is Wld, it has a transmission characteristic satisfying Wcut_on-Wcut_off> Wld. You may.

The telecentric optical system may have a glass base material having a rectangular outer shape and a Fresnel surface.

The figure which shows the module structure of the electronic system provided with the light receiving device by 1st Embodiment. The figure which shows the optical composition of a light receiving device. The figure explaining the Fresnel surface. The figure which shows the detailed optical composition of a telecentric optical system. The figure explaining the shape of the Fresnel surface of the rear group optical system in more detail. The figure which shows the optical characteristic of the telecentric optical system by this embodiment. The perspective view which shows an example of the rear group optical system. Sectional view of the rear group optical system. The cross-sectional view which shows an example of the rear group optical system of a hybrid structure. The figure which shows the optical composition of the optical system by 1st comparative example. The figure which shows the optical characteristic of the optical system of FIG. 8A. The figure which shows the optical composition of the optical system by 2nd comparative example. The figure which shows the optical characteristic of the optical system of FIG. 9A. The figure which shows the characteristic change of a light source. The figure which shows the temperature dependence of a light source. The figure which shows the correspondence relationship of the wavelength of the light incident on a filter, the incident angle and the spectral transmittance. The figure which shows the correspondence relationship of the wavelength of the light incident on the filter, the incident angle and the spectral transmittance when the excess bandwidth BW is 55 nm. The figure which shows the correspondence relationship of the wavelength of the light incident on the filter, the incident angle and the spectral transmittance when the excess bandwidth BW is 45 nm. The figure which shows the correspondence relationship of the wavelength of the light incident on the filter, the incident angle and the spectral transmittance when the excess bandwidth BW is 35 nm. The figure which shows the correspondence relationship of the wavelength of the light incident on the filter, the incident angle and the spectral transmittance when the excess bandwidth BW is 25 nm. It is a figure which summarized the characteristic of the filter of FIG. 12A to FIG. 12D. The figure which shows the correspondence relationship between the transmission bandwidth of a filter and a depth value, and the correspondence relationship between a transmission bandwidth of a filter and an S / N ratio (SNR). The figure which compared the characteristic of the optical system by 1st comparative example and the telecentric optical system by this embodiment. The figure which shows the optical structure of the light receiving device by 2nd Embodiment. FIG. 6 is a diagram showing a curved surface shape before forming a Fresnel surface on the glass base material of FIG. 16 and a detailed shape of the Fresnel surface 14. The figure which shows the correspondence relationship between the image height (mm) and the ray incident angle (degrees) of the telecentric optical system by 2nd Embodiment. The figure which shows the optical structure of the light receiving device according to 3rd Embodiment. The figure which shows the correspondence relationship between the image height (mm) of the telecentric optical system by 3rd Embodiment, and the ray incident angle (degree 9). It is a block diagram which shows an example of the schematic structure of a vehicle control system. It is explanatory drawing which shows an example of the installation position of the vehicle exterior information detection unit and the image pickup unit. It is a figure which shows the example of the installation position of the imaging unit.

Hereinafter, embodiments of the light receiving device and the electronic system according to the present disclosure will be described with reference to the drawings. In the following, the main components of the light receiving device and the electronic system according to the present disclosure will be mainly described, but the light receiving device and the electronic system according to the present disclosure may have components and functions not shown or described. The following description does not exclude components or functions not shown or described.

(First Embodiment)
FIG. 1 is a diagram showing a module configuration of an electronic system 2 including a light receiving device 1 according to the first embodiment. The electronic system 2 of FIG. 1 includes a light receiving device 1, a light source 3, and a support substrate 4. The light receiving device 1 and the light source 3 are arranged apart from each other on one main surface of the support substrate 4.

The electronic system 2 of FIG. 1 irradiates an object (not shown) with the light emitted from the light source 3, and the light receiving device 1 receives the reflected light from the object. The light receiving device 1 measures the distance from the electronic system 2 to the object by the time difference between the time when the light is emitted from the light source 3 and the time when the reflected light from the object is received. As described above, the electronic system 2 of FIG. 1 functions as a ToF system.

The light source 3 includes a light emitting element such as a vertical cavity surface emitting laser (VCSEL), a diffuser that uniformly diffuses the light emitted by the light emitting element, and a driver that supplies driving power to the light emitting element. The light source 3 emits light in the wavelength band of infrared light, for example. The wavelength band of the light emitted by the light source 3 is arbitrary.

FIG. 2 is a diagram showing an optical configuration of the light receiving device 1. As shown in FIG. 2, the light receiving device 1 includes a telecentric optical system 11, a bandpass filter (hereinafter, simply referred to as a filter) 12, and an imaging unit 13. The telecentric optical system 11, the filter 12, and the imaging unit 13 are arranged in order along the optical axis 20.

The filter 12 has a transmission characteristic that transmits light in the same wavelength band as the light emitted by the light source 3 and blocks light in other wavelength bands. For example, when the light source 3 emits infrared light, the filter 12 is an IRBPF that transmits the wavelength band of infrared light.

The telecentric optical system 11 has a feature that light substantially parallel to the optical axis 20 can be emitted without increasing the lens length. In FIG. 2, the lens length of the telecentric optical system 11 is L1. The telecentric optical system 11 according to the present embodiment has a Fresnel surface 14 as described later. The Fresnel surface 14 replaces the curved surface of the lens with a plurality of concentric grooves. By providing the Fresnel surface 14, the thickness of the lens can be reduced.

FIG. 3 is a diagram illustrating the Fresnel surface 14. The broken line in FIG. 3 shows the curved surface of a general convex lens. The Fresnel surface 14 is a stepped curved surface formed by dividing the curved surface of the convex lens into a plurality of concentric circles and moving the curved surface of each divided region in the direction of the central surface 14a of the convex lens. As a result, a plurality of grooves are formed on the Fresnel surface 14, and the bottom surface of each groove has a curvature similar to the curved surface of the convex lens.

The left side of the Fresnel surface 14 in FIG. 3 is the light incident side, and the right side is the filter 12 side. The thin dashed arrow line in FIG. 3 indicates the traveling direction of the light incident on the telecentric optical system 11. As shown in FIG. 3, the light incident substantially parallel to the Fresnel surface 14 is focused on the focal position in the same manner as a normal convex lens. On the other hand, the light obliquely incident on the Fresnel surface 14 is refracted in a direction close to the optical axis 20 direction and emitted.

In FIG. 2, the light rays incident on the telecentric optical system 11 are represented by fine solid lines. The telecentric optical system 11 has an optical configuration in which a lens group composed of a plurality of lenses is arranged in the optical axis 20 direction, and a Fresnel surface 14 is provided as a part of the lens group.

FIG. 4 is a diagram showing a detailed optical configuration of the telecentric optical system 11 according to the present embodiment. In FIG. 4, the traveling direction of the light incident on the telecentric optical system 11 from diagonally below the optical axis 20 is shown by a fine solid line. As shown in FIGS. 2 and 4, the telecentric optical system 11 has a front group optical system 21 and a rear group optical system 22. The front group optical system 21 has a refractive power that focuses the incident light and diverges each main ray. The rear group optical system 22 collimates the main light beam that has passed through the front group optical system 21. Collimating is the parallelization of light. The rear group optical system 22 has the Fresnel surface 14 described above. The light emitted from the rear group optical system 22 is incident on the filter 12. The light transmitted through the filter 12 is incident on the imaging unit 13. The right end of FIGS. 2 and 4 represents the imaging surface of the imaging unit 13.

The front group optical system 21 has a configuration in which a plurality of lenses are arranged along the optical axis 20. In the example of FIG. 4, the front group optical system 21 is composed of a lens group composed of three lenses, but the number and shape of the lenses constituting the front group optical system 21 are arbitrary.

The rear group optical system 22 has a first surface which is arranged to face the front group optical system 21 and a second surface which is arranged to face the filter 12, and the second surface is a Fresnel surface 14. Although the examples of FIGS. 2 and 4 show an example in which the rear group optical system 22 is composed of one lens, the rear group optical system 22 may be composed of a lens group composed of a plurality of lenses. In FIGS. 2 and 4, the surface of the rear group optical system 22 facing the filter 12 is the Fresnel surface 14, but the surface of the rear group optical system 22 other than the surface facing the filter 12 is the Fresnel surface. It may be the surface 14. However, if the Fresnel surface is provided on the side closer to the filter 12, the direction of the light incident on the filter 12 can be made closer to the direction of the optical axis 20.

The rear group optical system 22 of FIG. 4 has a lens 23 whose thickness gradually decreases from the center of the optical axis toward the periphery. The surface (second surface) of the lens 23 facing the filter 12 is a Fresnel surface 14. As shown in FIG. 3, the Fresnel surface 14 can reduce the thickness of the lens 23, that is, the degree of curvature. In the example of FIG. 4, the Fresnel surface 14 side of the rear group optical system 22 is a flat surface as an overall shape. On the other hand, the front group optical system 21 side of the rear group optical system 22 is largely curved, and the optical axis center side protrudes toward the front group optical system 21 side rather than the peripheral edge side. As a result, the rear group optical system 22 is thicker toward the center of the optical axis and thinner toward the peripheral edge.

By gradually reducing the thickness of the rear group optical system 22 from the center of the optical axis toward the peripheral edge, the CRA at the peripheral edge of the rear group optical system 22 can be reduced. Further, by making the surface (second surface) of the rear group optical system 22 facing the filter 12 a Fresnel surface 14, the traveling direction of the light emitted from the rear group optical system 22 is made substantially parallel to the optical axis 20. be able to.

FIG. 5 is a diagram for explaining the shape of the Fresnel surface 14 of the rear group optical system 22 in more detail. The curved surface on the left side of FIG. 5 shows the lens curved surface of the convex lens before forming the Fresnel surface 14. By dividing this lens curved surface into a plurality of regions concentrically from the center of the optical axis and moving the divided curved surface of each region toward the lens center surface side, a stepped Fresnel surface 14 as shown on the right side of FIG. 5 is formed. Will be done. Comparing the thicknesses of the lenses before and after forming the Fresnel surface 14, the thickness can be significantly reduced. For example, in the example of FIG. 5, there is a difference in thickness of 10 times or more before and after forming the Fresnel surface 14. Even if the thickness of the Fresnel surface 14 is reduced, the optical characteristics themselves can maintain the optical characteristics of the convex lens before forming the Fresnel surface 14, so that the incident light can be collimated on the Fresnel surface 14.

FIG. 6 is a diagram showing the optical characteristics of the telecentric optical system 11 according to the present embodiment, and more specifically, the correspondence between the image height (mm) and the light incident angle (degrees) of the telecentric optical system 11 according to the present embodiment. Have a relationship. FIG. 6 illustrates the characteristic w1 of the main ray, the characteristic w2 of the ray below the main ray, and the characteristic w3 of the ray above the main ray. The ray incident angle (CRA) of the main ray is almost 0 degrees regardless of the image height, and it can be seen that the CRA is sufficiently small. A sufficiently small CRA means that light is incident on the filter 12 from a direction close to the normal direction of the incident surface of the filter 12. This eliminates the risk of deterioration of the spectral characteristics of the filter 12.

FIG. 7A is a perspective view showing an example of the rear group optical system 22, and FIG. 7B is a cross-sectional view of the rear group optical system 22. The outer shape of the rear group optical system 22 shown in FIG. 7A is rectangular in accordance with the outer shapes of the filter 12 and the imaging unit 13. The surface of the rear group optical system 22 facing the front group optical system 21 has a convex shape as shown in the figure. On the other hand, the surface of the rear group optical system 22 facing the filter 12 side is a flat surface, but in reality, a minute-sized Fresnel surface 14 is formed on this flat surface. The outer shape of the rear group optical system 22 does not necessarily have to be rectangular, but it is desirable that the shape matches the outer shape of the filter 12 and the imaging unit 13.

The rear group optical system 22 is formed by using, for example, a glass base material. By etching the glass substrate, the Fresnel surface 14 can be formed relatively easily. The Fresnel surface 14 is formed on the bottom surface side of FIGS. 7A and 7B.

Instead of forming the rear group optical system 22 only with a glass base material, a hybrid structure of a resin base material and a glass base material may be used. FIG. 7C is a cross-sectional view showing an example of the rear group optical system 22 having a hybrid structure. In the example of FIG. 7C, after the upper surface of the flat glass base material 220 is processed into a Fresnel surface, a resin base material 221 having a thickness as large as the center of the optical axis is bonded to the Fresnel surface. A coating layer that functions as a filter 12 may be provided on the surface of the glass substrate 220 opposite to the bonding surface with the resin substrate 221. As a result, the rear group optical system 22 and the filter 12 can be brought into close contact with each other, and the light utilization efficiency can be improved.

FIG. 8A is a diagram showing an optical configuration of the optical system 25 according to the first comparative example. FIG. 8B is a diagram showing the optical characteristics of the optical system 25 of FIG. 8A, and shows the correspondence between the image height of the optical system 25 of FIG. 8A and the light ray incident angle. Since the optical system 25 of FIG. 8A is not the telecentric optical system 11, the lens length can be shortened, but the CRA is larger than that of FIG. In the CRA of FIG. 8B, since light is incident on the filter 12 from a direction inclined from the normal direction of the filter 12, the spectral characteristics of the filter 12 are deteriorated.

FIG. 9A is a diagram showing an optical configuration of the optical system 26 according to the second comparative example. 9B is a diagram showing the optical characteristics of the optical system 26 of FIG. 9A, and shows the correspondence between the image height of the optical system 26 of FIG. 9A and the light ray incident angle. The optical system 26 of FIG. 9A realizes a telecentric optical system by increasing the thickness of the lens on the rear side of the optical axis, and as shown in FIG. 9B, the CRA can also be reduced. However, since the lens length of the optical system 26 of FIG. 9A is longer than that of FIGS. 3 and 8A, it is difficult to mount it on a portable device such as a smartphone.

The wavelength of the light emitted from the light source 3 fluctuates due to manufacturing variations and temperature changes. When the wavelength of the light emitted from the light source 3 fluctuates, the wavelength of the light received by the light receiving device 1 also fluctuates, which adversely affects the spectral characteristics of the filter 12.

FIG. 10A is a diagram showing a change in the characteristics of the light source 3, and FIG. 10B is a diagram showing the temperature dependence of the light source 3. It should be noted that FIGS. 10A and 10B show changes in the characteristics of the specific light source 3, and different results can be obtained if the type of the light source 3 is different. The horizontal axis of FIG. 10B is the wavelength [nm], and the vertical axis is the light intensity [a.u.].

The upper two stages of FIG. 10A show wavelength fluctuations due to manufacturing variations of the light source 3. The third to sixth stages from the top of FIG. 10A show the fluctuation of the wavelength depending on the temperature of the light source 3.

As shown in FIG. 10A, the emission wavelength changes by 951.5-935.5 = 16 nm and the center wavelength is 943.5 nm due to the manufacturing variation of the light source 3.

Further, as shown in FIGS. 10A and 10B, as the temperature increases, the emission wavelength of the light source 3 increases and the light intensity decreases. For example, when compared at 0 ° C. and 85 ° C., the emission wavelengths differ by 955.1-934 = 21.1 nm.

As can be seen from FIG. 10A, the fluctuation amount of the emission wavelength is larger (= 21.1 nm) due to the temperature change than the fluctuation amount (= 16 nm) due to the manufacturing variation of the light emitting element.

In this way, the wavelength of the light emitted from the light source 3 fluctuates due to manufacturing variations, temperature, and the like, and the wavelength band of the reflected light from the object received by the light receiving device 1 also fluctuates accordingly. The spectral transmittance of the filter 12 changes depending on the wavelength of the light incident on the filter 12. The spectral transmittance of the filter 12 also changes depending on the incident angle of the light incident on the filter 12.

FIG. 11 is a diagram showing the correspondence between the wavelength of light incident on the filter 12, the angle of incidence, and the spectral transmittance. The curve w4 in FIG. 11 shows the correspondence between the wavelength at 0 degree incident and the spectral transmittance, and the curve w5 shows the correspondence between the wavelength at 30 degree incident and the spectral transmittance. Here, the incident angle is an inclination angle of the filter 12 with respect to the normal direction, and 0 degree means that light is incident from the normal direction.

In FIG. 11, the wavelength at which the spectral transmittance is 50% with respect to the 30-degree incident light beam is called the cut-on wavelength Wcut_on, and the lower limit wavelength at which the spectral transmittance is 50% with respect to the 0-degree incident light beam is called the cut-off wavelength. We call it Wcut_off.

The wavelength width of the difference between the cut-on wavelength Wcut_on and the cut-off wavelength Wcut_off (hereinafter referred to as the wavelength fluctuation bandwidth) can be transmitted by the filter 12 even if the incident angle of light changes within the range of 0 to 30 degrees. The bandwidth of light that can be produced (wavelength fluctuation bandwidth).

As shown in FIG. 11, the wavelength fluctuation bandwidth is separated from the transmission bandwidth BW of the 0-degree incident ray, the wavelength at which the spectral transmittance is 50% with respect to the 0-degree incident ray, and the spectrum with respect to the 30-degree incident ray. It is equal to the value obtained by subtracting the difference bandwidth Ws from the wavelength at which the transmittance becomes 50%. That is, the relationship of the following equation (1) holds.
BW-Ws = Wcut_on-Wcut_off ... (1)

The wavelength fluctuation bandwidth, which is the difference between the cut-on wavelength Wcut_on and the cut-off wavelength Wcut_off, differs depending on the type of the filter 12. 12A, 12B, 12C, and 12D are diagrams showing the correspondence between the wavelength, the angle of incidence, and the spectral transmittance of the light incident on the filter 12 having a transmission bandwidth BW of 55 nm, 45 nm, 35 nm, and 25 nm, respectively. be. The above-mentioned differential bandwidth Ws also differs depending on the transmission bandwidth BW.

The amount of fluctuation due to the temperature change of the emission wavelength of the light emitting element is 21.1 nm from FIG. 10A. If the difference (wavelength fluctuation bandwidth) between the cut-on wavelength Wcut_on and the cut-off wavelength Wcut_off in the above equation (1) is not 21.1 nm or more, the spectral characteristics of the filter 12 may deteriorate.

FIG. 13 is a diagram summarizing the characteristics of the filter 12 of FIGS. 12A to 12D. The larger the difference (wavelength fluctuation bandwidth) between the cut-on wavelength Wcut_on and the cut-off wavelength Wcut_off, the more noise light other than the reflected light of the light emitted from the light source 3 is transmitted by the filter 12. On the other hand, if the wavelength fluctuation bandwidth is too narrow, the reflected light may not be transmitted when the wavelength of the light emitted from the light source 3 fluctuates due to manufacturing variation or temperature change.

FIG. 14 is a diagram showing the correspondence between the transmission bandwidth of the filter 12 and the depth value, and the correspondence between the transmission bandwidth of the filter 12 and the S / N ratio (SNR). The depth value is the distance error to the object measured by the light receiving device 1, and the larger the depth value, the larger the distance error. Further, it is shown that the larger the S / N ratio is, the less susceptible to noise. Graph w6 of FIG. 14 shows the correspondence between the transmission bandwidth of the filter 12 and the depth value. Graph w7 shows the correspondence between the transmission bandwidth of the filter 12 and the S / N ratio. As shown by the broken line on the graph w6, the depth value 13.8 when the transmission bandwidth BW = 35 is smaller than the depth value 16.1 when the transmission bandwidth BW = 45. Further, the smaller the transmission bandwidth BW, the higher the S / N ratio. From the above, it can be seen that the smaller the transmission bandwidth BW is, the more desirable from the viewpoint of distance measurement.

Therefore, in the present embodiment, the difference (wavelength fluctuation bandwidth) between the cut-on wavelength Wcut_on and the cut-off wavelength Wcut_off is in the transmission bandwidth BW in which the fluctuation amount due to the temperature change of the emission wavelength of the light emitting element is larger than 21.1 nm. The minimum value, transmission bandwidth BW = 35 nm, is selected.

Since the transmission bandwidth BW may be larger than the fluctuation amount of 21.1 nm, the transmission bandwidth BW = 45 nm or 55 nm may be selected.

Summarizing the above, in the present embodiment, the transmission characteristics of the filter 12 are set so as to satisfy the inequality of the following equation (2). Wld in the formula (2) is the amount of fluctuation of the emission wavelength due to the initial wavelength variation of the light source 3 and the temperature change. Wcut_off-Wcut_on is the upper limit wavelength at which the transmittance becomes 50% when light is incident from the normal direction of the filter 12, and the direction inclined by a predetermined angle (for example, 30 degrees) from the normal direction of the filter 12. It is a difference wavelength from the upper limit wavelength at which the transmittance becomes 50% when light is incident from the above. By satisfying the equation (2), the filter 12 can transmit all the light rays emitted from the telecentric optical system 11 with a transmittance of 50% or more. Thereby, the spectral characteristics of the filter 12 can be improved.
Wcut_off-Wcut_on> Wld ... (2)

FIG. 15 is a diagram comparing the characteristics of the optical system 25 according to the first comparative example and the telecentric optical system 11 according to the present embodiment. The left side of the upper part of FIG. 15 shows the optical characteristics of the optical system 25 according to the first comparative example, and the right side of the upper part shows the optical characteristics of the optical system 11 according to the present embodiment. Further, the left side of the lower part of FIG. 15 shows the transmission characteristics of the filter 12 according to the first comparative example, and the right side of the lower part shows the transmission characteristics of the filter 12 according to the present embodiment. From the upper part of FIG. 15, it can be seen that this embodiment can make the CRA smaller than that of the first comparative example. Further, from the lower part of FIG. 15, in the present embodiment, even if the transmission bandwidth of the filter 12 is narrower than that of the first comparative example, the wavelength fluctuation range of the reflected light can be contained within the transmission bandwidth.

As described above, in the first embodiment, since the telecentric optical system 11 having the Fresnel surface 14 is provided in the light receiving device 1, the direction of the light emitted from the telecentric optical system 11 can be made substantially parallel to the optical axis. can. As a result, the CRA when the light transmitted through the telecentric optical system 11 is incident on the filter 12 can be reduced, and the spectral characteristics of the filter 12 can be improved.

(Second Embodiment)
FIG. 16 is a diagram showing an optical configuration of the light receiving device 1a according to the second embodiment. The light receiving device 1a of FIG. 16 includes a telecentric optical system 11a having an optical configuration different from that of FIG. 2, a filter 12, and an imaging unit 13. The telecentric optical system 11a of FIG. 16 has a front group optical system 21a and a rear group optical system 22a. The front group optical system 21a has, for example, four lenses arranged in order in the optical axis direction. The number and shape of the lenses can be changed to those other than those shown in FIG.

A filter 12 is integrally formed in the rear group optical system 22a. The rear group optical system 22a has a glass substrate having a substantially uniform thickness. The surface of the glass substrate facing the front group optical system 21a is the Fresnel surface 14. Further, a coating layer 23a is provided on the surface of the glass substrate on the image pickup unit 13 side. The coating layer 23a is a layer that functions as a filter 12, and transmits light in a predetermined wavelength band and does not transmit light in other wavelength bands.

As described above, the rear group optical system 22a of FIG. 16 is different from the rear group optical system 22a of FIG. 2 in that it has a glass substrate having a uniform thickness. Further, the rear group optical system 22a of FIG. 16 is different from the rear group optical system 22a of FIG. 2 in that the surface of the rear group optical system 22a facing the front group optical system 21a is a Fresnel surface 14.

The lens length L4 of the telecentric optical system 11a of FIG. 16 can be made approximately the same as the lens length L1 of the telecentric optical system 11a of FIG. Specifically, the lens length can be controlled by adjusting the internal lens configurations of the front group optical system 21a and the rear group optical system 22a. This lens length L4 is shorter than the lens length L3 of the second comparative example shown in FIG. 9A.

FIG. 17 is a diagram showing a curved surface shape before forming the Fresnel surface 14 on the glass substrate of FIG. 16 and a detailed shape of the Fresnel surface 14. Similar to FIG. 5, the Fresnel surface 14 formed on the glass base material of FIG. 16 is provided with a plurality of divided regions concentrically from the center of the optical axis of the glass base material, and the curved surface of each divided region is formed on the glass base material. It is formed by moving it toward the central surface.

FIG. 18 is a diagram showing a correspondence relationship between the image height (mm) of the telecentric optical system 11a and the light ray incident angle (degrees) according to the second embodiment. As can be seen by comparing FIG. 18 and FIG. 6, the telecentric optical system 11a according to the second embodiment has a coating that can reduce the CRA and functions as a filter 12, similarly to the telecentric optical system 11a according to the first embodiment. Since light substantially parallel to the optical axis can be incident on the layer 23a, the spectral characteristics of the filter 12 can be improved.

A resin member may be provided instead of the glass base material described above. Even if it is a resin member, the surface on the front group optical system 21a side can be made into a Fresnel surface 14, and the surface on the imaging unit 13 side can be provided with a coating layer 23a to function as a filter 12.

As described above, in the second embodiment, a glass base material or a resin base material having a substantially uniform thickness is provided inside the telecentric optical system 11a, and the surface of the base material on the front group optical system 21a side is a Fresnel surface. Since the coating layer 23a is provided on the surface of the imaging unit 13 to function as the filter 12, the CRA can be reduced with a simple structure, and the spectral characteristics of the filter 12 can be improved as in the first embodiment.

(Third Embodiment)
Although the first and second embodiments described above have described an example in which the rear group optical system 22 inside the telecentric optical system 11 has a Fresnel surface 14, a configuration without a Fresnel surface 14 is also conceivable.

FIG. 19 is a diagram showing an optical configuration of the light receiving device 1b according to the third embodiment. The light receiving device 1b of FIG. 19 includes a telecentric optical system 11b having no Fresnel surface 14. The telecentric optical system 11b of FIG. 19 includes a front group optical system 21b and a rear group optical system 22b. The optical configuration of the front group optical system 21b is almost the same as that in FIGS. 2 and 16. In the rear group optical system 22b, the resin base material 22d is bonded to the surface of the flat glass base material 22c on the front group optical system 21b side, and the coating layer 23a is provided on the surface of the glass base material 22c on the image pickup portion 13 side. There is. The resin base material 22d is thicker toward the center of the optical axis and thinner toward the periphery. By thinning the peripheral side of the resin base material 22d in this way, the CRA can be made small, and the light transmitted through the resin base material 22d can be made substantially parallel to the optical axis even without the Fresnel surface 14.

FIG. 20 is a diagram showing the correspondence between the image height (mm) of the telecentric optical system 11b and the light ray incident angle (degree 9) according to the third embodiment. As shown in the figure, the CRA is reduced regardless of the image height. can do.

As described above, in the third embodiment, the resin base material 22d bonded to the glass base material 22c is provided in the rear group optical system 22b inside the telecentric optical system 11b, and the thickness of the resin base material 22d is set as the optical axis. Since the thickness is gradually reduced from the center side to the peripheral edge, the CRA can be reduced without providing the Fresnel surface 14. Further, since the coating layer 23a is formed on the surface of the glass base material 22c on the image pickup unit 13 side to function as the filter 12, the spectral characteristics of the filter 12 can be improved even though the optical configuration is simple.

(Detailed configuration of electronic system 2)
The electronic system 2 provided with the light receiving device 1 according to the first to third embodiments described above irradiates the object with the light emitted by the light source 3, receives the reflected light, and the light source 3 emits the light. The distance to the object can be measured based on the time difference between the time and the time when the light receiving device 1 receives the reflected light.

FIG. 21 is a detailed block diagram of an electronic system 2 including a light source 3 and a light receiving device 1. The light source 3 may have one light emitting element 31 or may have a plurality of light emitting elements 31. The light emitting element 31 emits light by the electric power from the driver 32. The driver 32 controls the timing of supplying electric power to the light emitting element 31 by the signal from the light receiving device 1.

The light receiving device 1 includes, for example, a light receiving unit 33, a TDC 34, a calculation unit 35, a trigger generation unit 36, a control unit 37, and an interface unit 38.

The light receiving unit 33 has a SPAD array 39 and a read circuit 40. The SPAD array 39 is formed by arranging a plurality of SPADs (Single Photon Avalanche Diodes) in a one-dimensional or two-dimensional direction. A photoelectric conversion element other than SPAD may be provided. When any SPAD in the SPAD array 39 detects light, an electric signal having an amplitude corresponding to the amount of light is output. The read circuit 40 reads an electric signal output from any SPAD in the SPAD array 39. The TDC 34 measures the time difference between the timing of the electric signal read by the reading circuit 40 and the timing of the trigger generation unit 36 transmitting the trigger signal to the driver 32. The calculation unit 35 performs various signal processing based on the output signal of the TDC 34. The signal processing performed by the calculation unit 35 includes, for example, a process of measuring the distance to the object based on the time difference between the time when the light emitting element 31 emits light and the time when the light receiving unit 33 receives the reflected light. I'm out.

The light receiving unit 33 may receive not only the reflected light from the object but also noise light such as sunlight. Since the timing at which the noise light is received is different from the timing at which the original reflected light is received, the light source 3 repeatedly emits light, and the light receiving device 1 repeatedly receives the reflected light and repeats the distance measurement accordingly. , The distance may be measured in a state where the influence of noise light is removed by averaging a plurality of distance measurement results. Therefore, the calculation unit 35 may be provided with a histogram generation unit 35a. The histogram generation unit 35a averages the distance measurement results of a plurality of times, and measures the distance from the plurality of distance measurement results by a majority vote.

The control unit 37 controls each unit in the light receiving device 1. The distance measurement result calculated by the calculation unit 35 is sent to the outside via the control unit 37 and the interface unit 38.

The trigger generation unit 36 determines the timing at which the light source 3 emits light, and outputs a trigger signal. This trigger signal is received by the driver 32. The driver 32 drives the light source 3 in synchronization with the reception timing of the trigger signal.

The control system of the light receiving device 1 shown in FIG. 21 can be chipped together with the optical system or chipped separately from the optical system and mounted on the support substrate 4 of FIG.

The technology according to the present disclosure (the present technology) can be applied to various products. For example, the technology according to the present disclosure is realized as a device mounted on a moving body of any kind such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, a personal mobility, an airplane, a drone, a ship, and a robot. You may.

FIG. 22 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile control system to which the technique according to the present disclosure can be applied.

The vehicle control system 12000 includes a plurality of electronic control units connected via the communication network 12001. In the example shown in FIG. 22, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an outside information detection unit 12030, an in-vehicle information detection unit 12040, and an integrated control unit 12050. Further, as a functional configuration of the integrated control unit 12050, a microcomputer 12051, an audio image output unit 12052, and an in-vehicle network I / F (interface) 12053 are shown.

The drive system control unit 12010 controls the operation of the device related to the drive system of the vehicle according to various programs. For example, the drive system control unit 12010 provides a driving force generator for generating the driving force of the vehicle such as an internal combustion engine or a driving motor, a driving force transmission mechanism for transmitting the driving force to the wheels, and a steering angle of the vehicle. It functions as a control device such as a steering mechanism for adjusting and a braking device for generating a braking force of a vehicle.

The body system control unit 12020 controls the operation of various devices mounted on the vehicle body according to various programs. For example, the body system control unit 12020 functions as a keyless entry system, a smart key system, a power window device, or a control device for various lamps such as headlamps, back lamps, brake lamps, blinkers or fog lamps. In this case, the body system control unit 12020 may be input with radio waves transmitted from a portable device that substitutes for the key or signals of various switches. The body system control unit 12020 receives inputs of these radio waves or signals and controls a vehicle door lock device, a power window device, a lamp, and the like.

The vehicle exterior information detection unit 12030 detects information outside the vehicle equipped with the vehicle control system 12000. For example, the image pickup unit 12031 is connected to the vehicle exterior information detection unit 12030. The vehicle outside information detection unit 12030 causes the image pickup unit 12031 to capture an image of the outside of the vehicle and receives the captured image. The vehicle exterior information detection unit 12030 may perform object detection processing or distance detection processing such as a person, a vehicle, an obstacle, a sign, or a character on the road surface based on the received image.

The imaging unit 12031 is an optical sensor that receives light and outputs an electric signal according to the amount of the light received. The image pickup unit 12031 can output an electric signal as an image or can output it as distance measurement information. Further, the light received by the imaging unit 12031 may be visible light or invisible light such as infrared light.

The in-vehicle information detection unit 12040 detects information in the vehicle. For example, a driver state detection unit 12041 that detects the driver's state is connected to the in-vehicle information detection unit 12040. The driver state detection unit 12041 includes, for example, a camera that images the driver, and the in-vehicle information detection unit 12040 determines the degree of fatigue or concentration of the driver based on the detection information input from the driver state detection unit 12041. It may be calculated, or it may be determined whether or not the driver has fallen asleep.

The microcomputer 12051 calculates the control target value of the driving force generator, the steering mechanism, or the braking device based on the information inside and outside the vehicle acquired by the vehicle exterior information detection unit 12030 or the vehicle interior information detection unit 12040, and the drive system control unit. A control command can be output to 12010. For example, the microcomputer 12051 realizes ADAS (Advanced Driver Assistance System) functions including vehicle collision avoidance or impact mitigation, follow-up driving based on inter-vehicle distance, vehicle speed maintenance driving, vehicle collision warning, vehicle lane deviation warning, and the like. It is possible to perform cooperative control for the purpose of.

Further, the microcomputer 12051 controls the driving force generator, the steering mechanism, the braking device, and the like based on the information around the vehicle acquired by the vehicle exterior information detection unit 12030 or the vehicle interior information detection unit 12040. It is possible to perform coordinated control for the purpose of automatic driving, etc., which runs autonomously without depending on the operation.

Further, the microcomputer 12051 can output a control command to the body system control unit 12020 based on the information outside the vehicle acquired by the vehicle exterior information detection unit 12030. For example, the microcomputer 12051 controls the headlamps according to the position of the preceding vehicle or the oncoming vehicle detected by the external information detection unit 12030, and performs coordinated control for the purpose of anti-glare such as switching the high beam to the low beam. It can be carried out.

The audio-image output unit 12052 transmits an output signal of at least one of audio and an image to an output device capable of visually or audibly notifying the passenger of the vehicle or the outside of the vehicle. In the example of FIG. 22, an audio speaker 12061, a display unit 12062, and an instrument panel 12063 are exemplified as output devices. The display unit 12062 may include, for example, at least one of an onboard display and a heads-up display.

FIG. 23 is a diagram showing an example of the installation position of the imaging unit 12031.

In FIG. 23, the vehicle 12100 has image pickup units 12101, 12102, 12103, 12104, 12105 as the image pickup unit 12031.

The imaging units 12101, 12102, 12103, 12104, 12105 are provided at positions such as, for example, the front nose, side mirrors, rear bumpers, back doors, and the upper part of the windshield in the vehicle interior of the vehicle 12100. The imaging unit 12101 provided on the front nose and the imaging unit 12105 provided on the upper part of the windshield in the vehicle interior mainly acquire an image in front of the vehicle 12100. The imaging units 12102 and 12103 provided in the side mirrors mainly acquire images of the side of the vehicle 12100. The imaging unit 12104 provided on the rear bumper or the back door mainly acquires an image of the rear of the vehicle 12100. The images in front acquired by the imaging units 12101 and 12105 are mainly used for detecting a preceding vehicle or a pedestrian, an obstacle, a traffic light, a traffic sign, a lane, or the like.

Note that FIG. 23 shows an example of the photographing range of the imaging units 12101 to 12104. The imaging range 12111 indicates the imaging range of the imaging unit 12101 provided on the front nose, the imaging ranges 12112 and 12113 indicate the imaging ranges of the imaging units 12102 and 12103 provided on the side mirrors, respectively, and the imaging range 12114 indicates the imaging range of the imaging units 12102 and 12103. The imaging range of the imaging unit 12104 provided on the rear bumper or the back door is shown. For example, by superimposing the image data captured by the imaging units 12101 to 12104, a bird's-eye view image of the vehicle 12100 as viewed from above can be obtained.

At least one of the imaging units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of the image pickup units 12101 to 12104 may be a stereo camera composed of a plurality of image pickup elements, or may be an image pickup element having pixels for phase difference detection.

For example, the microcomputer 12051 has a distance to each three-dimensional object within the imaging range 12111 to 12114 based on the distance information obtained from the imaging units 12101 to 12104, and a temporal change of this distance (relative velocity with respect to the vehicle 12100). By obtaining can. Further, the microcomputer 12051 can set an inter-vehicle distance to be secured in front of the preceding vehicle in advance, and can perform automatic braking control (including follow-up stop control), automatic acceleration control (including follow-up start control), and the like. In this way, it is possible to perform coordinated control for the purpose of automatic driving or the like in which the vehicle travels autonomously without depending on the operation of the driver.

For example, the microcomputer 12051 converts three-dimensional object data related to a three-dimensional object into two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, utility poles, and other three-dimensional objects based on the distance information obtained from the imaging units 12101 to 12104. It can be classified and extracted and used for automatic avoidance of obstacles. For example, the microcomputer 12051 distinguishes obstacles around the vehicle 12100 into obstacles that can be seen by the driver of the vehicle 12100 and obstacles that are difficult to see. Then, the microcomputer 12051 determines the collision risk indicating the risk of collision with each obstacle, and when the collision risk is equal to or higher than the set value and there is a possibility of collision, the microcomputer 12051 is used via the audio speaker 12061 or the display unit 12062. By outputting an alarm to the driver and performing forced deceleration and avoidance steering via the drive system control unit 12010, driving support for collision avoidance can be provided.

At least one of the imaging units 12101 to 12104 may be an infrared camera that detects infrared rays. For example, the microcomputer 12051 can recognize a pedestrian by determining whether or not a pedestrian is present in the captured image of the imaging units 12101 to 12104. Such pedestrian recognition includes, for example, a procedure for extracting feature points in an image captured by an imaging unit 12101 to 12104 as an infrared camera, and pattern matching processing for a series of feature points indicating the outline of an object to determine whether or not the pedestrian is a pedestrian. It is done by the procedure to determine. When the microcomputer 12051 determines that a pedestrian is present in the captured images of the imaging units 12101 to 12104 and recognizes the pedestrian, the audio image output unit 12052 outputs a square contour line for emphasizing the recognized pedestrian. The display unit 12062 is controlled so as to superimpose and display. Further, the audio image output unit 12052 may control the display unit 12062 so as to display an icon or the like indicating a pedestrian at a desired position.

The example of the vehicle control system to which the technique according to the present disclosure can be applied has been described above. The technique according to the present disclosure can be applied to, for example, the imaging unit 12031 among the configurations described above. Specifically, the above-mentioned light receiving circuit, light receiving device, or distance measuring device can be mounted on the imaging unit 12031. By applying the technique according to the present disclosure to the imaging unit 12031, accurate distance information can be obtained in a wide FOV (field of view), and the functionality and safety of the vehicle 12100 can be enhanced.

The present technology can have the following configurations.
(1) A telecentric optical system with a Fresnel surface and
A filter that transmits light in a predetermined wavelength band from the light that has passed through the telecentric optical system,
A light receiving device including an imaging unit that photoelectrically converts light that has passed through the filter.
(2) The telecentric optical system is
The front group optical system that diverges the main ray of the incident peripheral luminous flux,
It has a rear group optical system that parallelizes the main light beam of the peripheral luminous flux that has passed through the front group optical system.
The light receiving device according to (1), wherein the rear group optical system has the Fresnel surface.
(3) The rear group optical system has a first surface which is arranged to face the front group optical system and a second surface which is arranged to face the filter.
The light receiving device according to (2), wherein the second surface is a Fresnel surface.
(4) The light receiving device according to (3), wherein the degree of curvature of the first surface is larger than the degree of curvature of the second surface.
(5) The light receiving device according to any one of (2) to (4), wherein the rear group optical system has a lens whose thickness decreases from the center of the optical axis toward the peripheral edge.
(6) The rear group optical system has a transparent base material having a uniform thickness and has a uniform thickness.
The transparent base material has a third surface arranged on the front group optical system side and a fourth surface arranged on the imaging unit side.
The third surface is a Fresnel surface,
The light receiving device according to (2), wherein the filter is a layer coated on the fourth surface.
(7) The telecentric optical system is incident with the reflected light emitted from the light source and reflected by the object.
The filter has Wcut_on as the upper limit wavelength at which the transmittance becomes 50% when light is incident from a direction inclined by a predetermined angle from the normal direction of the filter, and when light is incident from the normal direction of the filter. When the lower limit wavelength at which the transmittance becomes 50% is Wcut_off and the amount of change in the emission wavelength of the light source due to the initial wavelength variation of the light source and the temperature change is Wld, the transmittance has a transmission characteristic satisfying Wcut_on−Wcut_off> Wld. The light receiving device according to any one of (1) to (6).
(8) The light receiving device according to any one of (1) to (7), wherein the telecentric optical system has a glass base material having a rectangular outer shape and a Fresnel surface.
(9) The light receiving device according to any one of (1) to (7), wherein the telecentric optical system has a resin base material having a rectangular outer shape and a Fresnel surface.
(10) The telecentric optical system has a convex resin base material and a flat glass base material bonded to the resin base material.
The light receiving device according to (9), wherein the filter is a layer coated on the surface of the glass substrate.
(11) The telecentric optical system is incident with the reflected light emitted from the light source and reflected by the object.
The light receiving device has a distance measuring unit that measures the distance to the object by the time difference between the timing when the light source emits light and the timing when the light receiving device receives the reflected light (1) to. The light receiving device according to any one of (10).
(12) A light source that emits light and
A light receiving device that receives the reflected light that is emitted by the light source and reflected by the object.
An electronic system including a support substrate that supports the light source and the light receiving device.
The light receiving device is
Telecentric optics with Fresnel surface and
A filter that transmits light in a predetermined wavelength band from the light that has passed through the telecentric optical system,
An electronic system comprising an imaging unit that photoelectrically converts light that has passed through the filter.
(13) The light receiving device has a distance measuring unit that measures the distance to the object by the time difference between the timing when the light source emits light and the timing when the light receiving device receives the reflected light. 12) The electronic system according to.
(14) The telecentric optical system is
The front group optical system that diverges the main ray of the incident peripheral luminous flux,
It has a rear group optical system that parallelizes the main light beam of the peripheral luminous flux that has passed through the front group optical system.
The electronic system according to (12), wherein the rear group optical system has the Fresnel surface.
(15) The rear group optical system has a first surface which is arranged to face the front group optical system and a second surface which is arranged to face the filter.
The electronic system according to (14), wherein the second surface is a Fresnel surface.
(16) The electronic system according to (15), wherein the degree of curvature of the first surface is larger than the degree of curvature of the second surface.
(17) The electronic system according to any one of (14) to (16), wherein the rear group optical system has a lens whose thickness decreases from the center of the optical axis toward the peripheral edge.
(18) The rear group optical system has a transparent base material having a uniform thickness and has a uniform thickness.
The transparent base material has a third surface arranged on the front group optical system side and a fourth surface arranged on the imaging unit side.
The third surface is a Fresnel surface,
The electronic system according to (14), wherein the filter is a layer coated on the fourth surface.
(19) The telecentric optical system is incident with the reflected light emitted from the light source and reflected by the object.
The filter has Wcut_on as the upper limit wavelength at which the transmittance becomes 50% when light is incident from a direction inclined by a predetermined angle from the normal direction of the filter, and when light is incident from the normal direction of the filter. When the lower limit wavelength at which the transmittance becomes 50% is Wcut_off and the amount of change in the emission wavelength of the light source due to the initial wavelength variation of the light source and the temperature change is Wld, the transmittance has a transmission characteristic satisfying Wcut_on-Wcut_off> Wld. The electronic system according to any one of (12) to (18).
(20) The electronic system according to any one of claims 12 to 19, wherein the telecentric optical system has a glass substrate having a rectangular outer shape and a Fresnel surface.

The aspects of the present disclosure are not limited to the individual embodiments described above, but also include various modifications that can be conceived by those skilled in the art, and the effects of the present disclosure are not limited to the contents described above. That is, various additions, changes and partial deletions are possible without departing from the conceptual idea and purpose of the present disclosure derived from the contents defined in the claims and their equivalents.

1 Receiver, 2 Electronic system, 3 Light source, 4 Support substrate, 11, 11a, 11b Telecentric optical system, 12 Band pass filter, 13 Imaging unit, 14 Frenel plane, 20 Optical axis, 21, 21a, 21b Front group optical system , 22, 22a, 22b Rear group optical system, 23 lens, 23a coating layer, 25 optical system, 26 optical system, 220 glass base material, 221 resin base material, 31 light emitting element, 32 driver, 33 light receiving part, 34 TDC, 35 arithmetic unit, 36 trigger generation unit, 37 control unit, 38 interface unit, 39 SPAD array, 40 read circuit,

Claims (20)

Telecentric optics with Fresnel surface and
A filter that transmits light in a predetermined wavelength band from the light that has passed through the telecentric optical system,
A light receiving device including an imaging unit that photoelectrically converts light that has passed through the filter. The telecentric optical system is
The front group optical system that diverges the main ray of the incident peripheral luminous flux,
It has a rear group optical system that parallelizes the main light beam of the peripheral luminous flux that has passed through the front group optical system.
The light receiving device according to claim 1, wherein the rear group optical system has the Fresnel surface. The rear group optical system has a first surface which is arranged to face the front group optical system and a second surface which is arranged to face the filter.
The light receiving device according to claim 2, wherein the second surface is a Fresnel surface. The light receiving device according to claim 3, wherein the degree of curvature of the first surface is larger than the degree of curvature of the second surface. The light receiving device according to claim 2, wherein the rear group optical system has a lens whose thickness decreases from the center of the optical axis toward the peripheral edge. The rear group optical system has a transparent base material having a uniform thickness and has a uniform thickness.
The transparent base material has a third surface arranged on the front group optical system side and a fourth surface arranged on the imaging unit side.
The third surface is a Fresnel surface,
The light receiving device according to claim 2, wherein the filter is a layer coated on the fourth surface. The telecentric optical system is incident with the reflected light emitted from the light source and reflected by the object.
The filter has Wcut_on as the upper limit wavelength at which the transmittance becomes 50% when light is incident from a direction inclined by a predetermined angle from the normal direction of the filter, and when light is incident from the normal direction of the filter. When the lower limit wavelength at which the transmittance becomes 50% is Wcut_off and the amount of change in the emission wavelength of the light source due to the initial wavelength variation of the light source and the temperature change is Wld, the transmittance has a transmission characteristic satisfying Wcut_on−Wcut_off> Wld. The light receiving device according to claim 1. The light receiving device according to claim 1, wherein the telecentric optical system has a glass base material having a rectangular outer shape and a Fresnel surface. The light receiving device according to claim 1, wherein the telecentric optical system has a resin base material having a rectangular outer shape and a Fresnel surface. The telecentric optical system has a convex resin base material and a flat glass base material bonded to the resin base material.
The light receiving device according to claim 9, wherein the filter is a layer coated on the surface of the glass substrate. The telecentric optical system is incident with the reflected light emitted from the light source and reflected by the object.
The light receiving device has a distance measuring unit that measures the distance to the object by the time difference between the timing when the light source emits light and the timing when the light receiving device receives the reflected light. The light receiving device according to the description. A light source that emits light and
A light receiving device that receives the reflected light that is emitted by the light source and reflected by the object.
An electronic system including a support substrate that supports the light source and the light receiving device.
The light receiving device is
Telecentric optics with Fresnel surface and
A filter that transmits light in a predetermined wavelength band from the light that has passed through the telecentric optical system,
An electronic system comprising an imaging unit that photoelectrically converts light that has passed through the filter. 12. The light receiving device has a distance measuring unit that measures the distance to the object by the time difference between the timing at which the light source emits light and the timing at which the light receiving device receives the reflected light. The electronic system described. The telecentric optical system is
The front group optical system that diverges the main ray of the incident peripheral luminous flux,
It has a rear group optical system that parallelizes the main light beam of the peripheral luminous flux that has passed through the front group optical system.
The electronic system according to claim 12, wherein the rear group optical system has the Fresnel surface. The rear group optical system has a first surface which is arranged to face the front group optical system and a second surface which is arranged to face the filter.
The electronic system according to claim 14, wherein the second surface is a Fresnel surface. The electronic system according to claim 15, wherein the degree of curvature of the first surface is larger than the degree of curvature of the second surface. The electronic system according to claim 14, wherein the rear group optical system has a lens whose thickness decreases from the center of the optical axis toward the peripheral edge. The rear group optical system has a transparent base material having a uniform thickness and has a uniform thickness.
The transparent base material has a third surface arranged on the front group optical system side and a fourth surface arranged on the imaging unit side.
The third surface is a Fresnel surface,
The electronic system according to claim 14, wherein the filter is a layer coated on the fourth surface. The telecentric optical system is incident with the reflected light emitted from the light source and reflected by the object.
The filter has Wcut_on as the upper limit wavelength at which the transmittance becomes 50% when light is incident from a direction inclined by a predetermined angle from the normal direction of the filter, and when light is incident from the normal direction of the filter. When the lower limit wavelength at which the transmittance becomes 50% is Wcut_off and the amount of change in the emission wavelength of the light source due to the initial wavelength variation of the light source and the temperature change is Wld, the transmittance has a transmission characteristic satisfying Wcut_on-Wcut_off> Wld. The electronic system according to claim 12. The electronic system according to claim 12, wherein the telecentric optical system has a glass substrate having a rectangular outer shape and a Fresnel surface.

Images