Distance measuring device and electronic device

Abstract

[Problem] To provide a distance measurement device capable of reducing a decrease in distance measurement accuracy according to a subject distance. [Solution] A distance measurement device (1) is provided with a light source unit (113) comprising a light-emitting element array (210) in which a plurality of light-emitting elements are arranged and a microlens array (230) in which a plurality of microlenses are arranged, a light-receiving unit (120) comprising a light-receiving element array (310) in which a plurality of light-receiving elements are arranged, and an optical system (160) in which the light-emitting element array (210) and the microlens array (230) are arranged, the optical system (160) includes an image-side telecentric lens (130) and is configured to project light from the light source unit onto a subject via the image-side telecentric lens, and to cause the light receiving unit to receive reflected light from the subject via the image-side telecentric lens. The micro lens array and the image side telecentric lens form an afocal system. The offset amount is set such that the distance between the light receiving element array and the image-side principal point of the image-side telecentric lens is greater than the focal length of the image-side telecentric lens.

Description

Technical Field

[0001] The present invention relates to a distance measuring device. Background Art

[0002] There is known a time-of-flight (TOF) distance measurement method that measures the distance to a subject (subject distance) by measuring a time difference between irradiating light and detecting reflected light.

[0003] Patent Document 1 discloses a configuration that includes an aperture stop based on changes in the imaging position of the light-receiving optical system in order to suppress a decrease in the signal-to-noise ratio caused by external light and increase the robustness of the light-receiving system. Patent Document 2 discloses a configuration that slightly shifts the image sensor surface from the lens imaging position in order to reduce the image height dependency on the light-collecting position caused by distortion and the like.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2019-53040

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2015-161854 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] However, the configurations disclosed in Patent Documents 1 and 2 do not mention changing the imaging position according to the subject distance. Therefore, depending on the subject distance, the image focused by the light-receiving optical system may be blurred, and reflected light from the subject may be received across multiple light-receiving elements, thereby deteriorating the distance measurement accuracy.

[0010] An object of the present invention is to provide a distance measuring device capable of reducing a decrease in distance measurement accuracy according to the distance to an object.

[0011] Solutions for solving problems

[0012] A distance measuring device according to one aspect of the present invention includes: a light source unit including a light emitting element array having a plurality of light emitting elements and a microlens array having a plurality of microlenses; a light receiving unit including a light receiving element array having a plurality of light receiving elements; and an optical system including an image-side telecentric lens configured to project light from the light source unit onto a subject via the image-side telecentric lens and to cause the light receiving unit to receive reflected light from the subject via the image-side telecentric lens. The microlens array and the image-side telecentric lens form an afocal system. An offset is set so that the distance between the light receiving element array and the image-side principal point of the image-side telecentric lens is greater than the focal length of the image-side telecentric lens.

[0013] Other objects and features of the present invention will be described in the following examples.

[0014] Effects of the Invention

[0015] The present invention can provide a distance measuring device capable of reducing a decrease in distance measurement accuracy according to the object distance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a block diagram of a distance measuring device.

[0017] Figure 2 is a schematic diagram of a light source unit.

[0018] Figure 3 This is a schematic diagram of the light-receiving element array.

[0019] Figure 4 The behavior of projecting light is shown.

[0020] Figure 5 The behavior of the projection light projected onto the subject is shown.

[0021] Figure 6 Shown is the shift of the focusing position according to the subject distance in a two-lens lens configuration.

[0022] Figure 7 The behavior of the light receiving element array receiving reflected light corresponding to the distance to the subject is shown.

[0023] Figure 8 The behavior when the assembly position of the light emitting element array is changed is shown.

[0024] Figure 9 The behavior when the assembly position of the light receiving element array is changed is shown.

[0025] Figure 10 The following diagram shows the size of the light-collecting image when the assembly positions of the light-emitting element array and the light-receiving element array are changed. DETAILED DESCRIPTION

[0026] Now, with reference to the accompanying drawings, a detailed description will be given of embodiments according to the present invention. Corresponding elements in the respective drawings will be denoted by the same reference numerals, and repeated description thereof will be omitted.

[0027] (First embodiment)

[0028] A specific configuration of the distance measuring device according to the first embodiment will now be described with reference to the drawings.

[0029] [Overall configuration of distance measuring equipment]

[0030] Figure 1 1 is a schematic diagram showing the configuration of a distance measuring device 1 according to the present embodiment. The distance measuring device 1 includes a light projecting unit 110 , a measuring unit (light receiving unit) 120 , an image-side telecentric lens 130 , an overall control unit 140 , and a beam splitter 150 .

[0031] The light projection unit 110 includes a light source unit 113 and a light source control unit 114, wherein the light source unit 113 includes a light emitter 111 and an optical element 112. The light emitter 111 includes a light emitting element array 210, wherein in the light emitting element array 210, Figure 2 A plurality of light emitting elements 211 are shown.

[0032] The measuring unit 120 includes a light receptor 121, a time-to-digital converter (TDC) array unit 122, a signal processing unit 123, and a measurement control unit 124. The overall control unit 140 performs overall operational control of the distance measuring device 1. The overall control unit 140 includes, for example, a CPU, ROM, and RAM, and controls each part of the distance measuring device 1 by loading a program stored in the ROM into the RAM and executing the program via the CPU. At least a portion of the overall control unit 140 may be implemented as a dedicated hardware circuit.

[0033] Each of the multiple light-emitting elements 211 in the light source unit 113 emits pulsed light and is projected into space through the image-side telecentric lens 130. The pulsed light emitted from the multiple light-emitting elements 211 is projected to different angles of view in space. The projected light is irradiated onto the subject, and at least a portion of the light reflected by the subject is received by the light receiver 121 through the image-side telecentric lens 130. The optical system 160, which includes the image-side telecentric lens 130 and the beam splitter 150, projects light from the light source unit 113 onto the subject through the image-side telecentric lens 130. The optical system 160 also receives reflected light from the subject through the image-side telecentric lens 130 and causes the measurement unit 120 to receive it. The beam splitter 150 is arranged between the image-side telecentric lens 130 and the light source unit 113, and between the image-side telecentric lens 130 and the measurement unit 120.

[0034] The time from the emission of light by the light emitting element 211 to the reception of light by the light receiver 121 is the time of flight TOF, and this time is measured by the TDC array unit 122. However, in a single measurement, noise components due to noise light such as ambient light and dark counts cannot be eliminated, and the distance measurement error increases due to the influence of noise in the measurement circuit, etc. Therefore, the TDC array unit 122 repeats the time measurement from the emission of light to the reception of light, and the signal processing unit 123 creates a histogram of the measurement results, removes the noise components, and averages the measurement results. The obtained time of flight TOF can be substituted into the following formula (1) to obtain the distance L to the subject with high accuracy, where c is the speed of light:

[0035] L = TOF × c / 2 (1)

[0036] [Light source unit]

[0037] Figure 2 1 is a schematic diagram of the light source unit 113 constituting the light projection unit 110 according to the present embodiment. The light source unit 113 includes a light emitting element array 210 , a collimator lens array 220 , and a microlens array 230 .

[0038] The light emitting element array 210 is a two-dimensional array of vertical cavity surface emitting lasers (VCSELs) as a plurality of light emitting elements 211 on a substrate. The light emitting element 211 is not limited to VCSELs, but the plurality of light emitting elements 211 are preferably arranged in a one-dimensional or two-dimensional array. For example, the light emitting element 211 may be an edge emitting laser or an LED (light emitting diode). In the case of using an edge emitting laser as the light emitting element 211, a laser bar in which a plurality of edge emitting lasers are arranged one-dimensionally on a substrate, or a laser bar stack in which these plurality of edge emitting lasers are stacked to form a two-dimensional light emitting element array can be used as the light emitting element array 210. In the case of using an LED as the light emitting element 211, a plurality of LEDs arranged in a two-dimensional array on a substrate can be used as the light emitting element array 210.

[0039] In the distance measuring device 1 according to the present embodiment, in order to suppress the influence of ambient light, the wavelength of the light emitted from the light emitting element 211 is preferably in the near-infrared band. However, the wavelength used is not limited to this example. VCSEL is produced by a semiconductor process using materials used for conventional edge-emitting lasers and surface-emitting lasers. The main material that makes VCSEL emit light with a wavelength in the near-infrared band is GaAs-based semiconductor material. In this case, the dielectric multilayer film that forms the distributed Bragg reflector (DBR) mirror constituting the VCSEL may include two thin films (GaAs / AlGaAs) that are alternately and periodically stacked and made of materials with different refractive indices. The wavelength of the light to be emitted can be changed by adjusting the combination and composition of the elements of the compound semiconductor.

[0040] The VCSELs that make up the VCSEL array (light-emitting element array 210) include electrodes for injecting current and holes into the active layer, and by controlling the injection timing, arbitrary pulsed light or modulated light can be emitted. Therefore, a light source control unit 114 is provided. The light source control unit 114 can cause at least a portion of the light-emitting elements 211 to emit light at an arbitrary period. For example, the light source control unit 114 can independently drive each of the light-emitting elements 211, or drive each row or column of the VCSEL array, or drive each specific area.

[0041] Due to the diffraction phenomenon at the aperture of the VCSEL, the light emitted from the VCSEL, which serves as the light-emitting element 211, is generally divergent light. Therefore, in order to control the divergence angle of this divergent light or convert it into parallel light, a collimator lens array 220 is configured, wherein a plurality of collimator lenses 221 are arranged in a two-dimensional array in the collimator lens array 220. In this embodiment, the plurality of collimator lenses 221 constituting the collimator lens array 220 are arranged in a one-to-one correspondence with the light-emitting element 211. For example, the light emitted from the VCSEL array and collimated by the collimator lens array 220 is converted into parallel light in a direction perpendicular to the VCSEL array substrate. In the case where the radiation angle from the VCSEL is small due to the aperture diameter, etc., the collimator lens 221 can be omitted.

[0042] Behind the collimator lens array 220, a microlens array 230 is provided, wherein a plurality of microlenses 231 are arranged in a two-dimensional array in the microlens array 230. In other words, the collimator lens array 220 is provided between the light emitting element array 210 and the microlens array 230.

[0043] [Light receiving element]

[0044] Figure 3 FIG2 is a schematic diagram of a light receiving element array 310 constituting the light receiving device 121 according to this embodiment. The light receiving element array 310 is configured by arranging a plurality of light receiving elements 311 in a two-dimensional array. Each of the light receiving elements 311 includes a plurality of sub-light receiving elements 312. Each of the sub-light receiving elements can be driven independently.

[0045] exist Figure 3 In FIG, the light receiving element 311 includes 3×3 sub-light receiving elements, but it may include m×n (where m and n are natural numbers) sub-light receiving elements.

[0046] [Light projection and reception]

[0047] Figure 4 The state of the projected light after the light emitted from the plurality of light emitting elements 211 passes through the image-side telecentric lens 130 is shown.

[0048] The microlens 231 (microlens array 230) and the image-side telecentric lens 130 form an afocal system. Therefore, the light from the image-side telecentric lens 130 is projected at an angle corresponding to the image height (the positional relationship between the microlens 231 and the image-side telecentric lens 130) and is projected in parallel. Therefore, when viewed from the image-side telecentric lens 130, the width d of the projected light is b(three-dimensional thickness) is projected with the same width (three-dimensional thickness) at any distance from the subject (independent of the distance to the subject). Where p is the diameter of the light emitted from the light emitting element 211 on the microlens 231 (microlens array 230), f M is the focal length of the microlens 231, f L is the focal length of the image-side telecentric lens 130, and the width d of the projected light b It can be expressed by the following formula (2). However, when the width d of the projected light is b When the width d of the projected light is larger than the pupil diameter of the image side telecentric lens 130, the width d of the projected light is b When the light emission diameter p is larger than the arrangement period (pitch) of the microlenses 231 , the light emission diameter p is limited by the arrangement period (pitch) of the microlenses 231 .

[0049] d b =pf L / f M (2)

[0050] This configuration omits the collimator lens 221 , but in a case where the diffusion of light emitted from the light emitting element 211 increases, the collimator lens 221 may be inserted between the light emitting element 211 and the microlens 231 to collimate the light.

[0051] Now refer to Figure 5 (a) to (c) will give Figure 4 Description of the state of the projected light when viewed on the subject described in . Figure 5 (a) to (c) show the state of the projection light projected onto the subject 501. Figure 5 In (a) to (c) of FIG. 5 , the projection light is projected onto the subject 501 as a projection image 502 . Figure 5 The projected image size d in (a) to (c) b and Figure 4 The width d of the projected light b Equal to each other. Figure 5 (a), (b), and (c) show the subject 501 in order of proximity to the image-side telecentric lens 130 .

[0052] like Figure 5 As shown in (a) to (c), the distance between the projected light beams increases with the distance from the image side telecentric lens 130, but the projected image size d b In other words, the distance between the projection light beams that pass through the image side telecentric lens 130 and illuminate the subject 501 (projection light interval) changes according to the distance to the subject 501. On the other hand, the width of each of the multiple projection light beams (projection image size db ) does not change according to the distance to the subject 501. Figure 5 As shown in (d), the emission light from the predetermined light-emitting element 211 can be received only by the predetermined light-receiving element 311 in the light-receiving element array 310, and a one-to-one correspondence can be created between the plurality of light-emitting elements 211 and the plurality of light-receiving elements 311. Therefore, sequential driving can be achieved, which drives only some of the plurality of light-emitting elements 211, and drives only the light-receiving elements 311 corresponding to the portion of the light-receiving elements 211 that have been caused to emit light. Therefore, the plurality of light-receiving elements 311 can share a single TDC, which can reduce the pixel size, and thus this configuration is effective for higher resolution.

[0053] [Converged image shift and concentrated image size increase according to subject distance in a dual-lens configuration]

[0054] Figure 6 Shows how the focused image shifts according to the subject distance in a two-lens configuration using different image-side telecentric lenses for light emission and light reception.

[0055] Figure 6 (a) shows how light projected from the image side telecentric lens 131 is reflected by subjects 611, 612, and 613 at different distances from the image side telecentric lens 131, and how it is received via the image side telecentric lens 132. At this time, the subject 611 is a subject at a subject distance that provides the best imaging performance (focused subject). The subjects 612 and 613 are subjects that are closer to and farther away from the image side telecentric lenses 131 and 132, respectively, relative to the subject 611 (out-of-focus subjects). The light beams reflected at the subjects 611, 612, and 613 are reflected light beams 621, 622, and 623, respectively.

[0056] At this time, the incident angle of the light receiving side to the image side telecentric lens 132 is different according to the distance to the subject (here, the focused image shifts), so the focused positions of the reflected light beams 621, 622 and 623 after passing through the image side telecentric lens 132 are also different. Figure 6 (b) shows this state on the light receiving element 311. The reflected light beam 621 focused on the light receiving element 311 is a focused image 631. The reflected light beam 622 focused on the light receiving element 311 is a focused image 632. The reflected light beam 623 focused on the light receiving element 311 is a focused image 633. The focused images 632 and 633 are shifted in a certain direction relative to the focused image 631. Since the subjects 612 and 613 are out of focus, they are blurred, and each of the focused images 632 and 633 is larger than the focused image 631 (herein referred to as the focused image size increase).

[0057] Therefore, due to the shift of the concentrated image and the increase in the size of the concentrated image, the concentrated image may spread across adjacent light-receiving elements. In this case, the one-to-one correspondence between the light-emitting element 211 and the light-receiving element 311 may be lost, and the distance measurement accuracy may be reduced.

[0058] However, in the use according to the present embodiment, Figure 1 In the illustrated configuration of the beam splitter 150, no shift of the focused image occurs (i.e., a configuration in which at least a portion of the optical system 160 is shared by the light source unit 113 and the measurement unit 120). Therefore, in order to achieve a one-to-one correspondence between the light emitting element 211 and the light receiving element 311 and to reduce the degradation of distance measurement accuracy, it may be necessary to reduce the increase in the size of the focused image.

[0059] [Positional relationship between the image-side telecentric lens and the light-receiving element to minimize the increase in the size of the focused image]

[0060] Figure 7 It is explained that the light receiving element array 310 can be placed at a focal length f of the telecentric lens 130 on the image side. L Further positions reduce the spotlight and increase the image size.

[0061] Figure 7 (a) shows how reflected light beams from an infinitely distant subject 701, a shortest distance measurable subject 702, and a longest distance measurable subject 703 are focused on the light receiving element array 310 via the image side telecentric lens 130. These subject distances are L1 (=∞), L2 (≠∞), and L3 (≠∞). a0 is the distance between the image side principal point of the image side telecentric lens 130 and the light receiving element array 310, and S is the shift amount relative to a0 (where the direction of the light receiving element array 310 when viewed from the image side telecentric lens 130 is positive). Figure 7 (a) omits the beam splitter 150.

[0062] As the subject distance decreases, the influence of the reduction in distance measurement accuracy due to the increase in the size of the condensed image becomes significant. In this case, the subject distance L2 is the shortest subject distance within a range where the distance measurement accuracy satisfies a certain threshold.

[0063] On the other hand, as the subject distance increases, the effect of reduced distance measurement accuracy becomes more significant due to a decrease in the amount of reflected light from the subject that can be captured by the image-side telecentric lens 130. In this case, subject distance L3 is the longest subject distance within a range where the distance measurement accuracy meets a certain threshold.

[0064] At this time, the size d of the focused image on the light receiving element 311 is ss It can be expressed by the following formula (3), where Dp is the pupil diameter of the image-side telecentric lens 130:

[0065] d ss =D p ×|(a0-a) / a| (3) D p =f L / F (where F is the F number of the image-side telecentric lens 130), a=(1 / f L -1 / L) -1 (where L is the subject distance), and a0=f L +S. Figure 7 (b) and (c) show equation (3). Here, the focal length f of the image side telecentric lens 130 is L The aperture is 9mm and the F-number is 5.6.

[0066] Figure 7 (b) shows the case where a0=f L (S = 0 μm) focused image size d ss The relationship between the distance L and the subject. Figure 7 (c) shows the case where a0=f L +80 μm (S=80 μm) focused image size d ss The relationship between and the subject distance L. Figure 7 In (b), the subject at infinity is in focus, so as the subject distance L increases, the focused image size d ss Reduced, and at infinity, the focused image size d ss Gradually approaches zero. As the distance L to the subject decreases, the size of the focused image d ss On the other hand, Figure 7 In (c), at the subject distance L = L0 = (1 / f L -1 / a0) -1 At the spotlight image size d ss becomes minimum, and the focused image size d ss Increases as the position moves away from L0.

[0067] Therefore, in order to enable measurement of the subject distance for a subject that is not at infinity and is located between the subject distances L2 and L3, the distance a0 between the image side principal point of the image side telecentric lens 130 and the light receiving element array 310 may preferably be a0=f L +S(S>0).

[0068] As described above, the present embodiment sets the offset so that the distance a0 between the image side principal point of the image side telecentric lens 130 and the light receiving element array 310 is longer than the focal length f of the image side telecentric lens 130. LThe offset is configured to satisfy a0 = f L +S (S>0). This can reduce the influence of the increase in the size of the condensed image due to the subject distance.

[0069] (Second embodiment)

[0070] [Increase in concentrated image size due to manufacturing variations]

[0071] In the first embodiment, the distance a0 between the image side principal point of the image side telecentric lens 130 and the light receiving element array 310 is set to a0=f L +S (S>0) is used to reduce the increase in the size of the concentrated image. However, in practice, when assembling the light-emitting element array 210 and the light-receiving element array 310, they may deviate from the intended assembly position due to manufacturing variations. Now consider the manufacturing variations of the light-emitting element array 210 and the light-receiving element array 310 in the optical axis direction.

[0072] First, in the case where the light emitting element array 210 is displaced from the intended assembly position, refer to Figure 4 The described afocal system including the microlenses 231 (microlens array 230) and the image-side telecentric lens 130 is not ideal. To make it an ideal afocal system, the focal position of the microlens array 230 can be consistent with the focal position of the image-side telecentric lens 130, but the two focal positions may not match due to manufacturing variations. Figure 8 This status is shown. Figure 8 (a) shows the state of an ideal afocal system, and Figure 8 (b) shows a state where the afocal system is displaced from the ideal afocal system due to manufacturing variations. Here, the microlens array 230 is displaced by δM from the ideal position (the direction of the image-side telecentric lens 130 when viewed from the microlens array 230 is positive). At this time, the projection light emitted from the image-side telecentric lens 130 is projected in a diffuse manner according to the subject distance L. Here, Figure 8 The width d of the projected light in (b) b ' can be represented by the following formula (3)'.

[0073] d b '=d b ×|(L e -L) / L e |(3)'

[0074] As mentioned above, in d b Larger than the pupil diameter D of the image-side telecentric lens 130 p In the case of b =D p . L e =(1 / f L-1 / (f L -δM)) -1 As can be understood from formula (3), when δM is negative, the light is at L=L e (d b On the other hand, when δM is positive, d b 'Always expands according to the distance to the subject, so when δM is positive, the width d of the projected image b ' is always larger (the size of the light-collecting image on the light-receiving element 311 also increases). Therefore, unless otherwise specified, δM>0 is used in the following text.

[0075] Here, in Figure 8 In (a), the size d of the focused image when the projected light is reflected by the subject and is focused again by the image side telecentric lens 130 sb It can be expressed by the following formula (4). Similarly, Figure 8 The size of the focused image d in case (b) sb ' can be expressed by the following formula (5):

[0076] d sb =d b ×f L / (Lf L ) (4)

[0077] d sb '=d b '×f L / (Lf L )=d b ×|(L e -L) / L e |×f L / (Lf L )

[0078] =d b ×((-L e +L) / L e )×f L / (Lf L ) (5)

[0079] Since L>>f L , so equations (4) and (5) can be approximated by the following equations (4)' and (5)' respectively:

[0080] d sb =d b ×f L / L(4)'

[0081] d sb '=d b ×((-Le +L) / L e )×f L / L(5)'

[0082] According to formula (4)' and (5)', as Figure 8 As in (b), when the afocal system is shifted from the ideal afocal system, the size of the focused image will become larger (-L e +L) / L e times.

[0083] Next, Figure 9 A state is shown in which the light receiving element array 310 is displaced from an intended assembly position. Figure 9 (a) is similar to Figure 7 (a) of FIG. 1 shows a configuration in which the distance a0 between the image side principal point of the image side telecentric lens 130 and the light receiving element array 310 is set to a0=f L +S, thereby reducing the degradation of distance measurement accuracy caused by the increase in the size of the concentrated image. Figure 9 (b) shows that the position of the light receiving element array 310 changes from Figure 9 The state shown in (a) is shifted by δS. When viewed from the light receiving element array 310 , δS is positive in the direction of the image-side telecentric lens 130 . Figure 9 The size d of the light-collecting image on the light-receiving element array 310 in (a) is ss It can be expressed by equation (3). The pupil diameter of the telecentric lens 130 on the image side is D p In the case of Figure 9 The size d of the light-collecting image on the light-receiving element array 310 in (b) ss ' can be expressed by the following formula (6):

[0084] d ss '=D p ×|(a0-δS-a) / a| (6)

[0085] Where a=(1 / f L -1 / L) -1 And a0=(1 / f L -1 / L0) -1 Here, since L>>f L And L0>>f L , so Equation (6) can be approximated by the following Equation (6)':

[0086] d ss '=D p ×|f L (L-L0) / LL0-δS / f L |(6)'

[0087] The final focused image size d on the light receiving element array 310 s It is determined by the width of the projected light and the position of the light receiving element array 310 (the blur degree of the focused image), and can therefore be expressed by the following equation (7):

[0088] d s =d sb '+d ss '

[0089] ={d b ×((-L e +L) / L e )×f L / L}+{D p ×|f L (L-L0) / LL0-δS / f L |} (7)

[0090] At this time, it is assumed that there is no difference in the direction of the manufacturing variation (positive or negative) in the optical axis direction of the light receiving element array 310. For δS = ±α (α>0), d s Preferably, L=L min and L = L max The time intervals are equal, where L min is the shortest measurable subject distance, L max is the longest measurable subject distance. For δS = α, the focused image size d s When L=L min The maximum is at δS = -α, and for δS = -α, the focused image size d s When L=L max Therefore, it is preferable to satisfy the following formula (8):

[0091] {d b ×((-L e +L min ) / L e )×f L / L min}+{D p ×|f L (L min -L0) / L min L0-α / f L |}

[0092] ={d b ×((-L e +L max ) / L e )×f L / L max}+{D p×|f L (L max -L0) / L max L0+α / f L |} (8)

[0093] By modifying equation (8), L0 can be expressed by the following equation (9):

[0094] L0 = (2L min L max ) / {(1-pF / f M )L min +(1+pF / f M )L max} (9)

[0095] Therefore, the distance a0 between the image-side principal point of the image-side telecentric lens 130 and the light-receiving element array 310 can be expressed by the following equation (10):

[0096] a0 = (1 / f L -1 / L0) -1 (10)

[0097] Figure 10 The size d of the focused image at this time is shown s . Figure 10 (a) shows the calculation condition in Expression (10). Figure 10 (b) illustrates the focused image size d for δS = 40 μm s The relationship between the distance L to the subject, and Figure 10 (c) illustrates the focused image size d for δS = -40 μm s The relationship between the distance L and the subject. Figure 10 (b) and Figure 10 In (c), L min =1m and L max =50m. Figure 10 (b) and Figure 10 (c) It can be understood that the focused image size d s exist Figure 10 (b) where L = 1m and Figure 10 The L=50m in (c) is approximately equal.

[0098] As described above, this embodiment can suppress the variation in the manufacturing variation direction, and by setting a0=(1 / f L -1 / L0) -1 To allow the same amount of change, where L0 = (2L min L max ) / {(1-pF / f M)L min +(1+pF / f M )L max Therefore, this embodiment can reduce the increase in the size of the concentrated image due to manufacturing variations and suppress the reduction in distance measurement accuracy. In other words, this embodiment can be robust against manufacturing variations.

[0099] (Third embodiment)

[0100] In the second embodiment, the distance a0 between the image-side principal point of the image-side telecentric lens 130 and the light-receiving element array 310 is expressed by equation (10), but a0 may be within a range where the size of the focused image does not exceed a predetermined threshold. More specifically, a0 may satisfy the following conditional equation (11):

[0101] (1 / f L -1 / L0) -1 -Fδ < a0 < (1 / f L -1 / L0) -1 +Fδ (11)

[0102] Wherein F is the F number of the image-side telecentric lens 130 , and δ is the permissible circle of confusion of the image-side telecentric lens 130 .

[0103] In the case where the optical characteristics of the microlens 231 and the image-side telecentric lens 130 are ideal, the allowable circle of confusion δ can be regarded as the diffraction limit and is expressed by the following expression (12):

[0104] δ=2.44Fλ (12)

[0105] Here, λ is the wavelength of light emitted from the plurality of light emitting elements 211 .

[0106] Although the preferred embodiments of the present invention have been described as exemplary embodiments, the present invention is not limited to these embodiments, and various modifications and changes can be made within the gist thereof.

[0107] (Other embodiments)

[0108] The distance measurement device described above can be implemented in any electronic device having a processing component that operates to perform predetermined processing using the distance information. Such electronic devices include camera devices, computer devices (such as personal computers, tablet computers, media players, PDAs, etc.), mobile phones, smartphones, game consoles, robots, drones, vehicles, etc. These are merely examples, and the distance measurement device according to the present invention can also be implemented in other electronic devices.

[0109] The present invention can provide a program that implements one or more functions of the above-mentioned embodiments to a system or device via a network or storage medium, and can be implemented by one or more processors configured to read and execute the program in a computer in the system or device. It can also be implemented by a circuit (such as an ASIC) that implements one or more functions.

Claims

1. A distance measuring device, comprising: a light source unit including a light emitting element array in which a plurality of light emitting elements are arranged and a microlens array in which a plurality of microlenses are arranged; a light receiving unit comprising a light receiving element array in which a plurality of light receiving elements are arranged; as well as an optical system including an image-side telecentric lens and configured to project light from the light source unit onto a subject via the image-side telecentric lens and cause the light receiving unit to receive reflected light from the subject via the image-side telecentric lens, wherein the microlens array and the image-side telecentric lens form an afocal system, and The offset is set so that the distance between the light receiving element array and the image side principal point of the image side telecentric lens is greater than the focal length of the image side telecentric lens.

2. The distance measuring device according to claim 1, wherein The optical system further includes a beam splitter, and Wherein, the beam splitter is arranged between the image side telecentric lens and the light source unit and between the image side telecentric lens and the light receiving unit.

3. The distance measuring device according to claim 1 or 2, wherein: The light source unit and the light receiving unit share at least a portion of the optical system.

4. The distance measuring device according to claim 1, wherein The number of the image-side telecentric lens is one.

5. The distance measuring device according to any one of claims 1 to 4, wherein: The plurality of light emitting elements correspond to the plurality of light receiving elements on a one-to-one basis.

6. The distance measuring device according to any one of claims 1 to 5, wherein: The light source unit further includes a collimator lens array in which a plurality of collimator lenses are arranged, and the collimator lens array is disposed between the light emitting element array and the microlens array.

7. The distance measuring device according to any one of claims 1 to 6, wherein: The plurality of light emitting elements are arranged two-dimensionally, wherein the plurality of light receiving elements are arranged in two dimensions, and Wherein, the plurality of micro lenses are arranged in two dimensions.

8. The distance measuring device according to any one of claims 1 to 7, wherein: a0 is the distance between the light receiving element array and the image side principal point of the image side telecentric lens, L min is the shortest measurable subject distance, L max The longest measurable subject distance, f L is the focal length of the image side telecentric lens, F is the F number of the image side telecentric lens, p is the emission diameter of the light emitted from each of the plurality of light emitting elements on the microlens array, and f M When is the focal length of each of the plurality of microlenses, the following equation is satisfied: a0=(1 / f L -1 / L0) -1 L0=(2L min L max ) / {(1-pF / f M )L min +(1+pF / f M )L max },as well as Wherein, the offset is a0-f L .

9. The distance measuring device according to any one of claims 1 to 8, wherein: When the emission diameter of light emitted from each of the plurality of light emitting elements on the microlens array is larger than the arrangement period of the plurality of microlenses, the emission diameter is made equal to the arrangement period of the plurality of microlenses.

10. The distance measuring device according to any one of claims 1 to 9, wherein: The following conditional expressions are met: a0-Fδ <a0<a0+Fδ, Wherein, a0 is the distance between the light receiving element array and the image side principal point of the image side telecentric lens, F is the F number of the image side telecentric lens, and δ is the permissible circle of confusion of the image side telecentric lens.

11. The distance measuring device according to any one of claims 1 to 10, wherein: Satisfy the following formula: δ=2.44Fλ, Here, λ is the wavelength of light emitted from each of the plurality of light emitting elements, F is the F number of the image-side telecentric lens, and δ is the permissible circle of confusion of the image-side telecentric lens.

12. The distance measuring device according to any one of claims 1 to 11, further comprising: a light source control unit configured to control the light source unit, The light source control unit causes at least a portion of the plurality of light emitting elements to emit light in a random cycle.

13. The distance measuring device according to any one of claims 1 to 12, wherein: Light emitted from a predetermined light emitting element among the plurality of light emitting elements is received by a predetermined light receiving element among the plurality of light receiving elements.

14. The distance measuring device according to any one of claims 1 to 13, wherein: Each of the plurality of light receiving elements includes a plurality of sub-light receiving elements.

15. An electronic device comprising: The distance measuring device according to any one of claims 1 to 14; as well as A processing component is configured to perform predetermined processing using the distance information obtained by the distance measuring device.

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