JP7725239B2 - Lens device, imaging device, and in-vehicle system - Google Patents

Description

The present invention relates to a lens device used in imaging devices such as vehicle-mounted cameras.

Many lens devices have multiple lenses fitted into the inner circumference of a lens barrel. In such lens devices, the dimensional accuracy of the lens barrel is important in order to hold each lens with high positional accuracy and improve optical performance. Patent Document 1 discloses a lens barrel that holds multiple lenses, with a circumferential groove recessed from the image side to the object side between an outer barrel section that holds the lens closest to the object and extends toward the image side, and an inner barrel section located inside it that holds the lens closest to the image side, and a reinforcing rib within this circumferential groove. This lens barrel is molded from resin, and the dimensional accuracy of the lens barrel is improved by evenly arranging gates for molding the resin relative to the reinforcing rib.

JP 2017-53932 A

However, the lens barrel disclosed in Patent Document 1 may encounter problems over the wide temperature range (e.g., −40°C to +95°C) required for the operating environment of an in-vehicle camera. Specifically, at low temperatures, the lens barrel shrinks according to its linear expansion coefficient, which may cause it to tighten too tightly against the lens, resulting in damage or deformation of the lens. Furthermore, at high temperatures, thermal expansion may cause a gap to form between the lens barrel and the lens, which may lead to misalignment of the lens and result in a deterioration of optical performance.
The present invention provides a lens device that can maintain a lens well over a wide temperature range.

One aspect of the present invention provides a lens device comprising a lens and a holding member for holding the lens. The holding member includes a plurality of protrusions that protrude toward the optical axis, with abutment portions of each of the plurality of protrusions abutting against the outer periphery of the lens. A plurality of openings that penetrate the holding member in the optical axis direction are provided on the opposite side of the plurality of protrusions from the optical axis, corresponding to each of the plurality of protrusions. When viewed in the optical axis direction, the inner circumferential surfaces on both radial sides of the openings have an arc shape centered on the optical axis, and the entire abutment portion of each of the plurality of protrusions is located within an angular range centered on the optical axis from one end to the other circumferential end of the corresponding opening.

Note that an imaging device using the above-described lens device and an in-vehicle system including such an imaging device also constitute another aspect of the present invention.

This invention allows lenses to be maintained well over a wide temperature range, ensuring stable, high optical performance.

FIG. FIG. 2 is a cross-sectional view of a lens unit according to an embodiment. FIG. 10A to 10C are diagrams showing variations of the contact portion of the lens barrel in the embodiment. 5A and 5B are diagrams showing the positional relationship between a contact portion of a lens barrel and an opening in the embodiment. FIG. 10 is a diagram showing angle regions in an embodiment. 10A and 10B are diagrams showing the magnitude relationship and positional relationship between a first angle region and a second angle region in an embodiment. FIG. 10 is a diagram showing the relationship between the difference angle and the generated stress in the example. 10A and 10B are diagrams showing the magnitude relationship and positional relationship between the first and third angle regions in the embodiment; 10A to 10C are diagrams showing variations in the shape of the hole in the embodiment. FIG. 1 is a functional block diagram of an in-vehicle system using a lens unit according to an embodiment. 1 is a schematic diagram of a vehicle equipped with the above-described in-vehicle system. 4 is a flowchart showing the operation of the in-vehicle system.

The following describes an embodiment of the present invention with reference to the drawings.

Figure 1 shows the lens barrel (holding member) 4 of a lens unit as a lens device according to a first embodiment of the present invention. Figure 2 shows a cross section along the optical axis of the lens unit 1, which is composed of the lens barrel 4 and the lenses 2 and 3 held by it. The lens unit 1 can be used in vehicle-mounted cameras, cameras for mobile devices, and other imaging devices.

Lens 2 and 3 are each made of plastic or glass so that their peripheral edges are circular. Lenses 2 and 3 are held by lens barrel 4 so that their optical axes coincide with each other, forming a wide-angle lens. Lens 3 is the object-side lens, and lens 2 is the image-side lens with a smaller diameter than lens 3.

The radial support portion 46 of the lens barrel 4 abuts against the entire outer periphery of the lens 3, holding the lens 3 in the radial direction, and the thrust support portion 47 of the lens barrel 4 abuts against the back surface of the lens 3, holding the lens 3 in the optical axis direction.

A recess 50 is formed in the center of the thrust support 47 (the inner periphery of the lens barrel 4), recessed from the object side toward the image side so that the lens 2 can be accommodated. The image-side surface of the recess 50 forms a thrust support 44 that abuts against the back surface 21 of the lens 2 and holds the lens 2 in the optical axis direction. Furthermore, protrusions 42 that protrude radially inward (toward the optical axis) are formed at multiple locations (three locations in this embodiment) around the periphery of the inner periphery of the recess 50. An abutment 45 is formed at the inner diameter end of each protrusion 42 as an arcuate surface with a length in the circumferential direction. The lens 2 is press-fitted into the three abutment portions 45 from the object side. The three abutment portions 45 abut against three locations on the outer periphery (outer periphery) of the lens 2 to hold the lens 2 in the radial direction.

The three protrusions 42 are spaced at equal intervals of 120° in the circumferential direction. The portion of the inner surface of the recess 50 other than the protrusions 42 forms a recess 41 that is spaced radially outward from the outer surface of the lens 2. This allows the lens 2 to be stably held at three points in the circumferential direction, and also reduces the difficulty of manufacturing the lens barrel 4 compared to supporting the entire circumference of the lens 3, such as with the radial support portion 46. This is because high processing precision is required for the portion that supports the lens 2, but with a three-point holding configuration, precision is only required for the abutment portion 45.

In addition, a hole 43 is provided as an opening corresponding to each protrusion 42 on the radially outer side (opposite the optical axis) of each protrusion 42 in the thrust receiving portion 47. Each hole 43 extends circumferentially in an arc shape, penetrating the thrust receiving portion 47 in the optical axis direction, and its circumferential length is longer than the circumferential length of the abutment portion 45 (protrusion 42). By forming such a hole 43, a deformable portion 49 is formed between the protrusion 42 and the corresponding hole 43, which has a thin radial thickness, extends circumferentially, and is radially deformable.

The hole 43 has an inner peripheral surface 433 that extends in an arc shape concentric with the outer periphery of the lens 2. Forming the inner peripheral surface 433 in this manner facilitates uniform thickness of the deformable portion 49. If the deformable portion 49 has a non-uniform thickness, problems such as reduced dimensional accuracy and sink marks may occur when manufacturing the lens barrel 4 by injection molding. While the protrusion 42 is exaggerated in the figure for clarity, in reality, the protrusion amount of the protrusion 42 is small enough not to affect the uniformity of the deformable portion 49's thickness. Furthermore, stresses within the deformable portion 49 caused by shrinkage of the lens barrel 4 due to temperature changes or press-fitting of the lens 2 against the three abutment portions 45 may be concentrated in the thinnest portions, potentially damaging the deformable portion 49. For this reason, it is preferable to form at least the inner peripheral surface 433 on the protruding portion side of the hole 43 so that it extends in an arc shape concentric with the outer periphery of the lens 2.

FIG. 3 shows the lens barrel 4 as viewed in the optical axis direction. A first angular range 481 is a circumferential angular range centered on the optical axis, extending from one circumferential end 451 to the other circumferential end 452 of each contact portion 45 ( i.e. , the entire circumferential direction of the contact portion 45). A second angular range 482 is a circumferential angular range extending from one circumferential end 431 to the other circumferential end 432 of the hole 43 corresponding to that contact portion 45. Here, the one circumferential end 431 and the other circumferential end 432 of the hole 43 each represent the vertices of the arc-shaped ends. The first angular range 481 and the second angular range 482 are set so that the entire first angular range 481 (i.e., the entire circumferential direction of the contact portion 45) falls within the second angular range 482. In the lens unit 1 configured as described above, when pressure is applied to the contact portions 45 from the outer peripheral surface of the lens 2, the deformable portions 49 deform radially outward, thereby reducing stress generated within the lens 2 compared to when this deformation does not occur. This prevents excessive stress from being generated within the lens 2 when the lens 2 is press-fitted into the three contact portions 45 or when there is a difference in the amount of thermal deformation due to temperature changes due to differences in the linear expansion coefficients of the lens barrel 4 and the lens 2 (for example, when the lens barrel 4 shrinks more than the lens 2 in a low-temperature environment). Furthermore, by deforming the deformable portions 49 to press-fit the lens 2 into the contact portions 45, the contact of the contact portions 45 with the outer peripheral surface of the lens 2 can be maintained even if the lens barrel 4 expands more than the lens 2 in a high-temperature environment. As a result, degradation of optical performance due to misalignment or tilt of the optical axis of the lens 2 can be avoided.

As shown in Figure 3, it is desirable that the hole 43 and the protrusion 42 each have a shape that is symmetrical in the circumferential direction with respect to a plane (plane of symmetry) 453 that passes through the circumferential center of the abutment portion 45 and the optical axis. This ensures that the stress acting on the abutment portion 45 from the deformable portion 49 and the protrusion 42 is distributed evenly in the circumferential direction, enabling more stable support of the lens 2. However, as long as it does not affect the deformation of the deformable portion 49, the hole 43 and the protrusion 42 do not need to be symmetrical, and the plane that passes through the circumferential center of the hole 43 and the optical axis and the plane that passes through the circumferential center of the protrusion 42 and the optical axis do not need to coincide.

According to this embodiment, the lens 2 can be maintained well over a wider temperature range than conventionally possible, ensuring the stable high optical performance of the lens unit 1. Furthermore, according to this embodiment, it is possible to select glass as the material for the lens 2 that could not be selected with conventional configurations, and it is possible to select a material with a higher linear expansion coefficient as the material for the lens barrel 4.

In this embodiment, the abutment portion 45 is described as having a length in the circumferential direction and is formed in a shape that abuts against the outer peripheral surface of the lens 2 with a surface. However, as shown in Figures 4(a) and (b), the abutment portion 45 may have a shape that does not have a length in the circumferential direction, and abuts against the outer peripheral surface of the lens 2 at a point or along a line extending in the optical axis direction. In this case, as shown in Figure 5, the first angle range 481 is a circumferential position (angular position) and is represented by a single straight line in the figure, but the entire circumferential direction of the abutment portion 45 falls within the second angle range 482, just like in Figure 3.

Also, as shown in Figure 6, one circumferential end 431 and the other circumferential end 432 of the hole 43 may be formed as linear shapes extending radially. In this case, too, the entire circumferential length of the abutment portion 45 (the entire first angle range 481) falls within the second angle range 482, just like in Figure 3.

Next, we will explain the lens unit of Example 2 of the present invention. Figure 7 shows the lens barrel 4 of the lens unit of Example 2 as viewed in the optical axis direction. The configuration and shape of the lens barrel 4 are the same as those of Example 1.

In Figure 7, the interior angle α of the first angle range 481 and the interior angle β of the second angle range 482 are smaller than the interior angle β. This is also true for Example 1, and the stress generated within the lens barrel 4 can be prevented from occurring excessively within the lens 2 by deformation of the deformable portion 49 between the abutment portion 45 and the hole portion 43.

Furthermore, as shown in Figure 7, it is preferable that the bisectors of the interior angles α and β coincide with each other when viewed in the optical axis direction. This makes it possible to move the abutment portion 45 in the normal direction to the outer peripheral surface of the lens 2 by deforming the deformable portion 49, thereby preventing the generation of excessive stress within the lens 2 while maintaining a stable abutment state with the lens 2. Note that the bisectors of the interior angles α and β may be offset from each other.

Furthermore, the larger the differential angle θ, which is equivalent to half the difference between the interior angles α and β, the easier it is for the abutment portion 45 to move in the normal direction to the outer peripheral surface of the lens 2. Figure 8 shows the results of a simulation of the relationship between the differential angle θ and the stress generated in the deformable portion 49. The stress decreases sharply when the differential angle θ is between 0° and approximately 5°, and then decreases more gradually from there towards 30°. As the differential angle θ is increased from there, the structural strength of the abutment portion 45 decreases. For this reason, it is preferable that the differential angle θ be between 5° and 30°.

Without the hole 43, the lens barrel 4 is less likely to deform, and much of the stress that is generated acts on the lens 2. In contrast, by providing the hole 43 and generating stress in the deformable section 49 or by deforming the deformable section 49, it is possible to hold the lens 2 with precision while mitigating the stress acting on the lens 2.

Figure 9 also shows the lens barrel 4 as viewed in the optical axis direction. In Figure 9, the circumferential angular range from one circumferential end 434 to the other circumferential end 435 of the inner circumferential surface (arc line: not including the arc-shaped inner end surface having vertices 431 and 432) 433 on the protruding portion side of the hole 43 is defined as a third angular range 483 (=γ). The first angular range (α) 481 and the third angular range 483 (γ) are set so that the entire first angular range 481 (i.e., the entire abutment portion 45) falls within the third angular range 483.

It is also preferable that the bisectors (circumferential centers) of the first angle range (α) 481 and the third angle range 483 (γ) coincide with each other. In other words, it is preferable that the first angle range 481 (i.e., the abutment portion 45) and the third angle range 483 are circumferentially symmetric with respect to a plane (plane of symmetry) 4831 that passes through the circumferential center of the abutment portion 45 and the optical axis. Note that the bisectors of the first angle range 481 and the third angle range 483 may be offset from each other.

In the above examples, the hole 43 has an arc shape, but the hole 43 may have other shapes. For example, it may be rectangular as shown in Figure 10(a) or circular as shown in Figure 10(b).

Figure 11 shows the configuration of an in-vehicle camera 10 as an imaging device according to a third embodiment of the present invention, and an in-vehicle system (driving assistance device) 600 equipped with the same. The in-vehicle system 600 is held by a movable vehicle (mobile device) such as an automobile (vehicle), and is a system for assisting the driving (piloting) of the vehicle based on image information of the surroundings of the vehicle acquired by the in-vehicle camera 10.

Figure 12 shows a vehicle 700 as a mobile device equipped with an in-vehicle system 600. In Figure 12, the imaging range R of the in-vehicle camera 10 is set in front of the vehicle 700, but the imaging range R may also be set behind or to the side of the vehicle 700.

11 and 12 , the in-vehicle system 600 includes an in-vehicle camera 10, a vehicle information acquisition device 20, a control device (controller, ECU: Electronic Control Unit) 30, and a warning device (warning unit) 40. As shown in FIG. 11 , the in-vehicle camera 10 also includes an imaging unit 101 , an image processing unit 102 , a parallax calculation unit 103 , a distance acquisition unit (acquisition unit) 104 , and a collision determination unit 105. The processing unit is made up of the image processing unit 102 , the parallax calculation unit 103 , the distance acquisition unit 104 , and the collision determination unit 105. The imaging unit 101 is an imaging device that includes the lens unit of Example 1 or 2 and an imaging element such as a CCD sensor or a CMOS sensor, and captures an image of an object.

The flowchart in Figure 13 shows an example of the operation of the in-vehicle system 600. The in-vehicle system 600 (mainly the control device 30) executes this process in accordance with a computer program.

First, in step S1, the imaging unit 101 captures images of objects (targets) such as obstacles and pedestrians around the vehicle, and acquires a plurality of image data (parallax image data).

In step S2, vehicle information is acquired by the vehicle information acquisition device 20. Vehicle information includes the vehicle speed, yaw rate, steering angle, etc.

In step S3, the image processing unit 102 performs image processing on the multiple image data acquired by the imaging unit 101. Specifically, image feature analysis is performed to analyze feature quantities such as the amount and direction of edges in the image data and density values. Here, the image feature analysis may be performed on each of the multiple image data, or may be performed on only some of the multiple image data.

In step S4, the parallax calculation unit 103 calculates parallax (image shift) information between the multiple image data acquired by the imaging unit 101. As a method for calculating the parallax information, known methods such as the SSDA method and the area correlation method can be used, and therefore a description thereof will be omitted here. Note that steps S2, S3, and S4 may be performed in the above order, or may be performed in parallel with each other.

In step S5, distance information about the distance to the target object captured by the imaging unit 101 is acquired (calculated) by the distance acquisition unit 104. The distance information can be calculated based on the parallax information calculated by the parallax calculation unit 103 and internal and external parameters of the imaging unit 101. Note that the distance information here refers to information about the relative position to the target object, such as the distance to the target object, the defocus amount, and the image shift amount, and may directly represent the distance value of the target object in the image or may indirectly represent information corresponding to the distance value.

Then, in step S6, the collision determination unit 105 determines whether the distance to the object is within a preset distance range using the vehicle information acquired by the vehicle information acquisition device 20 and the distance information calculated by the distance acquisition unit 104. This makes it possible to determine whether an object exists within a preset distance around the vehicle and to determine the possibility of a collision between the vehicle and the object. If an object exists within the set distance, the collision determination unit 105 determines that there is a "possibility of collision" (step S7), and if there is no object within the set distance, it determines that there is "no possibility of collision" (step S8).

Next, when the collision determination unit 105 determines that there is a "possibility of collision," it notifies (transmits) the determination result to the control device 30 and the warning device 40. At this time, the control device 30 controls the vehicle based on the determination result of the collision determination unit 105 (step S6), and the warning device 40 issues a warning to the vehicle user (driver, passengers) based on the determination result of the collision determination unit 105 (step S7). Note that the notification of the determination result may be sent to at least one of the control device 30 and the warning device 40.

The control device 30 can control the movement of the vehicle by outputting control signals to the vehicle's drive units (engine, motor, etc.). For example, it performs control such as applying the brakes, releasing the accelerator, turning the steering wheel, and generating control signals to generate braking force on each wheel to suppress the output of the engine or motor. The warning device 40 also warns the user by, for example, emitting a warning sound (alarm), displaying warning information on the screen of a car navigation system, or vibrating the seat belt or steering wheel.

The in-vehicle system 600 of this embodiment can effectively detect objects through the above processing, making it possible to avoid collisions between the vehicle and the object. In particular, by applying the optical systems according to the above-mentioned embodiments to the in-vehicle system 600, it becomes possible to detect objects and determine collisions over a wide angle of view while miniaturizing the entire in-vehicle camera 10 and increasing the degree of freedom in placement.

There are various methods for calculating distance information. As an example, a case will be described in which a split-pupil image sensor having a plurality of pixels regularly arranged in a two-dimensional array is used as the image sensor of the image sensor 101. In a split-pupil image sensor, each pixel is composed of a microlens and a plurality of photoelectric conversion units, and can receive a pair of light beams passing through different regions in the pupil of the optical system and output a pair of image data from each photoelectric conversion unit.

Then, the image shift amount for each region is calculated by a correlation calculation between the paired image data, and image shift map data representing the distribution of the image shift amount is calculated by the distance acquisition unit 104. Alternatively, the distance acquisition unit 104 may further convert the image shift amount into a defocus amount to generate defocus map data representing the distribution of the defocus amount (distribution on a two-dimensional plane of the captured image). Furthermore, the distance acquisition unit 104 may acquire distance map data of the distance to the object converted from the defocus amount.

The in-vehicle system 600 and the mobile device 700 may also be equipped with a notification device (notification unit) for notifying the manufacturer of the in-vehicle system or the dealer of the mobile device in the event that the mobile device 700 collides with an obstacle. For example, the notification device may be one that sends information (collision information) related to the collision between the mobile device 700 and an obstacle to a pre-set external notification destination via email or the like.

In this way, by adopting a configuration in which the notification device automatically notifies collision information, it is possible to promptly take measures such as inspection and repair after a collision occurs. The destination of the collision information may be an insurance company, a medical institution, the police, or any other party set by the user. Furthermore, the notification device may be configured to notify the destination not only of collision information but also of malfunction information of each part and information on consumption of consumables. The detection of the presence or absence of a collision may be performed using distance information acquired based on the output from the above-mentioned image sensor , or may be performed by another detection unit (sensor).

In this embodiment, the in-vehicle system 600 is applied to driving assistance (collision damage reduction), but the application is not limited to this. The in-vehicle system 600 may also be applied to cruise control (including an all-speed tracking function), autonomous driving, etc. Furthermore, the in-vehicle system 600 is not limited to vehicles such as automobiles, but can be applied to moving bodies such as ships, aircraft, industrial robots, etc. Furthermore, the application is not limited to moving bodies, but can be applied to various devices that use object recognition, such as intelligent transport systems (ITS).
(Other Examples)
The present invention can also be realized by supplying a program that realizes one or more of the functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program.The present invention can also be realized by a circuit (e.g., an ASIC) that realizes one or more of the functions.

The embodiments described above are merely representative examples, and various modifications and variations are possible when implementing the present invention.

In the above-described embodiment, the lens device is described as being applied to an on-board camera 10 as a distance measuring device, but it may also be applied to on-board cameras other than distance measuring devices. For example, the on-board camera may be placed at the rear or side of the vehicle, and the acquired image information may be displayed on a display unit (monitor) inside the vehicle to provide driving assistance. In this case, components used for distance measurement, such as a parallax calculation unit, distance acquisition unit, and collision determination unit, may not be provided.

Furthermore, in the above-described embodiment, the lens device is described as being applied to an imaging unit in an in-vehicle system, but this is not limiting. For example, the lens device may be applied to imaging devices such as digital still cameras, digital video cameras, and silver halide film cameras, or may be applied to optical instruments such as telescopes or image projection devices such as projectors.

1 Lens units 2, 3 Lens 4 Lens barrel 42 Protrusion 43 Hole 481 First angle range 482 Second angle range

Claims (18)

Lenses and
a holding member for holding the lens;
the holding member includes a plurality of protrusions that protrude toward the optical axis, and a contact portion of each of the plurality of protrusions contacts an outer periphery of the lens,
a plurality of openings penetrating in the optical axis direction are provided on the holding member on the opposite side of the optical axis from the plurality of protrusions, the openings corresponding to the plurality of protrusions,
When viewed in the optical axis direction, the inner circumferential surfaces on both radial sides of the opening have an arc shape centered on the optical axis, and the entire abutment portion of each of the multiple protrusions is located inside an angular range centered on the optical axis from one end to the other end of the corresponding opening in the circumferential direction. The lens device described in claim 1, characterized in that the portion of the holding member between the protrusion and the corresponding opening is a deformable portion that is radially deformable. The abutment portion has a circumferential length,
When viewed in the optical axis direction, an angular range centered on the optical axis from one end to the other end in the circumferential direction of the contact portion is defined as a first angular range, and the angular range from one end to the other end in the circumferential direction of the opening corresponding to the contact portion is defined as a second angular range,
3. The lens device according to claim 1, wherein the entire first angular range is within the second angular range. The lens device described in claim 3, characterized in that half of the difference between the interior angle of the first angle range and the interior angle of the second angle range is greater than or equal to 5° and less than or equal to 30°. A lens device according to claim 1 or 2, characterized in that the abutment portion has no circumferential length and abuts against the outer periphery of the lens at a point or line. A lens device according to any one of claims 1 to 5, wherein the protrusion and the opening each have a shape that is symmetrical with respect to a plane passing through their circumferential centers and the optical axis. A lens device as described in any one of claims 1 to 6, characterized in that, when viewed in the optical axis direction, the entire abutment portion of each of the multiple protrusions is located within an angular range centered on the optical axis from one end to the other end of an arc line on the protrusion side of the opening corresponding to the protrusion. The abutment portion has a circumferential length,
When viewed in the optical axis direction, the angular range from one end to the other end in the circumferential direction of the abutment portion is defined as a first angular range, and the angular range from one end to the other end of the arc line is defined as a third angular range,
8. The lens device according to claim 7, wherein the center of the first angular range and the center of the third angular range in the circumferential direction coincide with each other. 9. The lens device according to claim 1, wherein inner end surfaces on both sides in the circumferential direction of the opening have an arcuate shape. An imaging device comprising: the lens device according to claim 1 ; and an imaging element that captures an image of an object through the lens. The imaging device according to claim 10 ;
and a processing unit that processes image information acquired by the imaging device. 12. The in-vehicle system according to claim 11 , further comprising a determination unit that determines the possibility of a collision between the vehicle and the object based on the image information. 13. The in-vehicle system according to claim 12 , further comprising a notification device that notifies an external party of information relating to a collision between the vehicle and the object. A moving device comprising the imaging device described in claim 10, capable of holding and moving the imaging device. The moving device according to claim 14 , further comprising a determination unit that determines the possibility of a collision with the object based on image information acquired by the imaging device. The moving device according to claim 15 , further comprising a control unit that outputs a control signal for controlling movement when it is determined that there is a possibility of collision with the object. The mobile device according to claim 15 or 16 , further comprising a warning unit that issues a warning to a user of the mobile device when it is determined that there is a possibility of a collision with the object. The mobile device according to any one of claims 15 to 17 , further comprising a notification unit that notifies an external device of information relating to the collision with the object.