Light emission control device, light emission control method, position estimation device, and position estimation method

Abstract

Provided are a light emission control device, a light emission control method, a position estimation device, and a position estimation method that make it possible to reduce the influence of heat resulting from light emission by a target for estimating the position of a camera. The light emission control device comprises: a camera control unit (70) that controls the exposure timing of a camera that has captured an image of a plurality of targets when estimating the position of the camera; and a light emission control unit (72) that causes the plurality of targets to emit pulsed light in accordance with the exposure timing of the camera. The position estimation device (50) comprises: the light emission control device; and a position estimation unit (62) that estimates the position of the camera on the basis of the image of the plurality of targets captured by the camera.

Description

Light emission control device, light emission control method, self-position estimation device, and self-position estimation method

[0001] The present invention relates to a target light emission control device and light emission control method for self-position estimation of a camera, as well as a self-position estimation device and self-position estimation method.

[0002] Traditionally, portable three-dimensional coordinate measuring machines (CMMs) have been mounted on robots to automatically measure large workpieces. While portable CMMs are meeting accuracy requirements of several tens of micrometers, bridge-type CMMs are currently being used to address high-precision requirements of 10 micrometers or less.

[0003] Furthermore, measurement methods using laser trackers or markers are known as techniques to achieve an accuracy of several tens of micrometers (see, for example, Patent Document 1). These methods include a base station equipped with an elevation and azimuth swivel function, and further equipped with a distance sensor or camera to calculate the distance and orientation of the measurement head. With this measurement method, because the movable range of the swivel mechanism and the measuring range of the distance sensor are long, measurements can be taken over a wide area.

[0004] However, in measurement methods using laser trackers or markers, the measurement accuracy tends to deteriorate as the distance between the base station and the measurement head increases, mainly due to the limitations of the angle accuracy of the swivel mechanism.

[0005] On the other hand, a method is known for estimating the camera's own position (position and orientation) from images taken with a camera of targets whose positions in three-dimensional space are known (see, for example, Patent Document 2). This method has the advantage of being able to easily obtain high accuracy (5 μm or less) with a relatively simple mechanism by relating the position of each target in three-dimensional space with the position of each target in the captured image and performing calculations.

[0006] Japanese Patent Publication No. 2020-148515 Japanese Patent Publication No. 2022-30807

[0007] Incidentally, when estimating the self-position of a camera, a target that emits light by itself (for example, an LED (Light-Emitting Diode) panel) may be used as a target. When performing self-position estimation using such a target, by causing only the target corresponding to the location photographed by the camera to emit light (light up) among the target group, heat transfer to the workpiece can be suppressed, and energy savings can be achieved.

[0008] However, when only some of the targets emit light, the locations where heat is generated due to the light emission will be unevenly distributed both spatially and temporally. As shown in FIG. 8, as the light-emitting locations (gray targets) in the target group TG transition in the order of AA in VIII A, AB in VIII B, and AC in VIII C as the camera CAM moves, the location where heat is generated due to the light emission (heat-generating location) and the location where the heat generated by the light emission is released (cooling location) will be sequentially interchanged. Thus, when the heat-generating locations and the cooling locations are unevenly distributed in the target group TG, distortion due to thermal expansion occurs, which can be a factor in the error of self-position estimation.

[0009] The present invention has been made in view of such circumstances, and an object thereof is to provide a light emission control device, a light emission control method, a self-position estimation device, and a self-position estimation method capable of reducing the influence of heat caused by the light emission of a target for self-position estimation of a camera.

[0010] The light emission control device according to the first aspect of the present invention includes a camera control unit that controls the exposure timing of a camera when performing self-position estimation of a camera that has photographed a plurality of targets, and a light emission control unit that causes the plurality of targets to emit pulsed light in accordance with the exposure timing of the camera.

[0011] The light emission control device according to the second aspect of the present invention, in the first aspect, the light emission control unit causes the plurality of targets to emit pulsed light in a batch.

[0012] The light emission control device according to the third aspect of the present invention, in the first or second aspect, the light emission control unit makes the exposure timing of the camera coincide with the light emission timing of the plurality of targets.

[0013] In the light emission control device according to the fourth aspect of the present invention, in any of the first to third aspects, the light emission control unit randomly sets an interval between the light emission start times of a plurality of targets.

[0014] In the light emission control device according to the fifth aspect of the present invention, in any of the first to fourth aspects, the light emission control unit causes targets that overlap with the imaging range of the camera among the plurality of targets to emit light during the exposure time of the camera, and causes the plurality of targets to emit light in a time-division manner for each group outside the exposure time of the camera.

[0015] The self-position estimation device according to the sixth aspect of the present invention includes the light emission control device according to any of the first to fifth aspects and a self-position estimation unit that estimates the self-position of the camera based on an image obtained by capturing a plurality of targets with a camera.

[0016] The light emission control method according to the seventh aspect of the present invention includes a step of controlling the exposure timing of a camera when estimating the self-position of the camera that has captured a plurality of targets, and a step of causing the plurality of targets to emit light in pulses according to the exposure timing of the camera.

[0017] The self-position estimation method according to the eighth aspect of the present invention includes a step of controlling the light emission of a plurality of targets by the light emission control method according to the seventh aspect, and a step of estimating the self-position of the camera based on an image obtained by capturing the plurality of targets with the camera.

[0018] According to the present invention, by limiting the light emission time of the targets used for estimating the self-position of the camera, it is possible to reduce the influence of heat caused by light emission.

[0019] This is a block diagram showing the self-position estimation system according to this embodiment. This is a schematic configuration diagram showing the general configuration of the self-position estimation system according to this embodiment. This is an explanatory diagram for explaining the camera projection model. This is a timing chart for explaining the target light emission control according to Embodiment 1. This is a timing chart for explaining the target light emission control according to Embodiment 2. This is a perspective view for explaining the target light emission control according to Embodiment 3. This is a timing chart for explaining the target light emission control according to Embodiment 3. This is a perspective view for explaining the target light emission control.

[0020] Embodiments of the present invention will be described below with reference to the attached drawings.

[0021] [Self-Position Estimation System] Figure 1 is a block diagram showing the self-position estimation system 10 according to this embodiment. Figure 2 is a schematic diagram showing the general configuration of the self-position estimation system 10 according to this embodiment.

[0022] As shown in Figures 1 and 2, the self-position estimation system 10 comprises a probe head 12, a target plate 14, and a self-position estimation device 50. The self-position estimation device 50 is an example of the self-position estimation device of the present invention. In this embodiment, the self-position estimation device 50 is configured separately from the probe head 12, but the probe head 12 may have at least some of the functions of the self-position estimation device 50.

[0023] The probe head 12 is a portable three-dimensional coordinate measuring machine that measures the three-dimensional coordinates of a workpiece (not shown). The probe head 12 is equipped with a contact-type or non-contact-type probe 18. The probe 18 may be a contact-type (touch probe type) or a non-contact-type (laser type, optical type) probe, as long as it is capable of measuring the three-dimensional coordinates of the workpiece. Examples of non-contact probes include laser scanners, point lasers, and line lasers. By holding the probe head 12 and performing measurements, the three-dimensional coordinates at the measurement points of the workpiece can be obtained.

[0024] The probe head 12 has a self-position estimation function, and when the camera 20 mounted on the probe head 12 photographs the target group 16, the self-position estimation device 50 described later can estimate the probe head 12's own position (position and orientation).

[0025] As shown in Figure 2, the target plate 14 has a main surface (target placement surface) 14a on which multiple (numerous) target groups 16 are arranged. That is, the main surface 14a of the target plate 14 is divided into multiple regions, and a target group (panel) 16 is provided in each region. In other words, the target plate 14 has a structure in which multiple target groups 16 are arranged adjacently (closely) in a two-dimensional manner on its main surface 14a. Each target group 16 is formed in a hexagonal shape (honeycomb shape), and the distance between the centers of adjacent target groups 16 is constant. Furthermore, each target group 16 has a common structure, and as will be described later, each target group 16 is provided with multiple (numerous) targets 24.

[0026] In this embodiment, as an example, the planar shape of each target group 16 is shown to be hexagonal (honeycomb-shaped), but it is not limited to this, and polygonal shapes such as triangles, squares, trapezoids, rhombuses, and pentagons can be applied as appropriate. However, from the viewpoint of strength and ease of manufacture, it is preferable that each target group 16 is hexagonal.

[0027] As shown in Figure 2, the target group 16 is provided with multiple (many) targets 24 arranged in a two-dimensional manner. Each target 24 is formed as a point or dot. Each target 24 may also be composed of a small point-shaped light source (point light source), such as an LED (Light-Emitting Diode). In the target group 16, each target 24 is spaced apart from each other, and the relative positions of the targets 24 are known. The shape and size of each target 24 in the target group 16 are also known.

[0028] [Self-Position Estimation Device] Next, the self-position estimation device 50 will be described. As shown in Figure 1, the self-position estimation device 50 is composed of, for example, a personal computer and includes a calculation processing unit 52 and a storage unit 54. A camera 20 mounted on the probe head 12 is connected to the self-position estimation device 50. The method of connection to the camera 20 is not particularly limited and may be connected via a cable, or via a wired or wireless network.

[0029] The storage unit 54 stores control programs and various data. The storage unit 54 is composed of, for example, a hard disk drive (HDD) or a solid state drive (SSD). The storage unit 54 may also include temporary memory elements composed of, for example, DRAM (Dynamic Random Access Memory) or SRAM (Static Random Access Memory), which are RAM (Random Access Memory), and may function as a work area for the arithmetic processing unit 52.

[0030] The memory unit 54 stores the target images, which will be described later. The memory unit 54 also stores information (target group information) regarding the shape, size, and arrangement of each target 24 that make up the target group 16.

[0031] The arithmetic processing unit 52 executes various arithmetic processes performed by the self-position estimation device 50. The arithmetic processing unit 52 comprises an arithmetic circuit composed of various processors and memory. The various processors include CPUs (Central Processing Units), GPUs (Graphics Processing Units), ASICs (Application Specific Integrated Circuits), and programmable logic devices [for example, SPLDs (Simple Programmable Logic Devices), CPLDs (Complex Programmable Logic Devices), and FPGAs (Field Programmable Gate Arrays)]. The various functions of the arithmetic processing unit 52 may be implemented by a single processor, or by multiple processors of the same or different types.

[0032] The arithmetic processing unit 52 functions as the image acquisition unit 60, the self-position estimation unit 62, the camera control unit 70, and the light emission control unit 72 by reading and executing the control program stored in the storage unit 54. The self-position estimation unit 62 includes a feature point detection unit 64 and an optimization calculation unit 66.

[0033] Note that the image acquisition unit 60 is an example of the image acquisition unit of the present invention. The self-position estimation unit 62 is an example of the self-position estimation unit of the present invention. The camera control unit 70 and the light emission control unit 72 are examples of light emission control devices.

[0034] [Camera Projection Model] Before describing the self-position estimation process performed by the self-position estimation device 50 of this embodiment, we will now explain the camera projection model that serves as its premise. Figure 3 is an explanatory diagram for illustrating the camera projection model.

[0035] As shown in Figure 3, the world coordinate system (world coordinate system) Σ ｗ O is a coordinate system that represents a position in three-dimensional space (real space), with the origin being O. ｗ Let X be mutually orthogonal. ｗ Axis, Y ｗ axis, Z ｗIt is a three-dimensional orthogonal coordinate system with an axis as the coordinate axis. Note that the world coordinate system Σ ｗ Any coordinate system may be used as long as it can specify the position (three-dimensional position) in the three-dimensional space. The camera coordinate system Σ ｃ has the optical axis center O of the camera 20 ｃ as the origin, and the right direction from the origin O ｃ is the X ｃ axis, the downward direction is the Y ｃ axis, and the optical axis direction is the Z ｃ axis, which is a three-dimensional orthogonal coordinate system. The image coordinate system Σ ｓ has the upper left corner of the image plane IP, which is at a focal length f away from the origin O ｃ of the camera coordinate system Σ ｃ in the Z ｃ direction, as the origin, and has U and V axes in directions parallel to the X ｃ axis and the Y ｃ axis respectively, which is a two-dimensional orthogonal coordinate system (pixel coordinate system).

[0036] First, the coordinates (x ｗ , y ｗ , z ｗ ) of a point P (object point) in the three-dimensional space in the world coordinate system Σ ｗ can be converted into the coordinates (x, y, z) in the camera coordinate system Σ ｃ using the rotation matrix R and the translation vector t of the camera 20 as shown in the following equation (1).

[0037] Here, [R|t] w,c is a transformation matrix (external parameter matrix) for coordinate transformation from the world coordinate system Σ ｗ to the camera coordinate system Σ ｃ , and represents the pose and position of the camera 20 in the world coordinate system Σ ｗ . Each component r w,c , r 11 , …, r 12 , t 33 , t x , t y , t z is called the external parameter of the camera.

[0038] Next, the camera coordinate system Σ ｃIf point P, located at (x, y, z) as viewed from the image plane IP, has coordinates (pixel coordinates) of the projected point Q as (u, v), then the following relationships shown in equations (2) to (7) hold.

[0039]

[0040]

[0041]

[0042]

[0043]

[0044] Here, (x', y') is the camera coordinate system Σ ｃ This represents the coordinates of the projected point when point P, located at (x, y, z) as viewed from the camera, is projected onto the normalized image plane (z=1). Furthermore, (x'', y'') represents the coordinates of the projected point (distorted point) when point P is projected onto the normalized image plane, taking into account the lens distortion of the camera 20.

[0045] Also, yf ｘ , f ｙ This indicates the focal length in the x and y directions, expressed in pixels. Also, c ｘ , c ｙ This is the image coordinate system Σ ｓ This indicates the optical center in (the position where the optical axis of camera 20 intersects the image plane IP, the optical center on a pixel-by-pixel basis). Also, k １ , k ２ , k ３ is the radial strain coefficient, and p １ , p ２ is the tangential distortion coefficient. In this specification, the focal length f ｘ , f ｙ , optical center c ｘ , c ｙ These are called the internal parameters of camera 20, and the distortion coefficient k １ , k ２ , k ３ , p １ , p ２ This is called the distortion parameter of camera 20.

[0046] The self-position of the camera 20 obtained in the self-position estimation process of this embodiment is determined in the world coordinate system Σ in the camera projection model described above. ｗ A matrix [R|t] showing the orientation and position of camera 20. w,c This is equivalent to determining (the external parameters of camera 20).

[0047] [Self-Position Estimation Method] Next, the processing procedure (an example of a self-position estimation method) of the self-position estimation process performed by the self-position estimation device 50 of this embodiment will be described. At the start of the self-position estimation process, it is assumed that the camera 20 has already been calibrated and that the camera matrix K, which includes the intrinsic parameters (focal length, optical center) and distortion parameters (distortion coefficient) of the camera 20, is known.

[0048] First, as shown in Figure 2, the camera 20 mounted on the probe head 12 captures images of the target group 16. The camera control unit 70 controls the exposure timing of the camera 20 (for example, the start time of exposure and the exposure time (exposure duration)). The light emission control unit 72 controls the light emission of the targets 24 of the target group 16 according to the exposure timing of the camera 20.

[0049] The image (target image) captured by camera 20 is transmitted to self-position estimation device 50. When the target image is transmitted to self-position estimation device 50, the image acquisition unit 60 acquires the target image and stores it in the storage unit 54.

[0050] Next, the self-position estimation unit 62 estimates the camera 20's own position (position and orientation) based on the target image captured by the camera 20. The following describes the processing performed by the self-position estimation unit 62.

[0051] First, the feature point detection unit 64 performs a feature point detection process to detect multiple feature points from the target image.

[0052] Specifically, the feature point detection unit 64 reads the target image from the storage unit 54. Then, the feature point detection unit 64 performs predetermined image processing (such as grayscale conversion) on the read target image, detects feature points (image points) that indicate the position of each target 24 (target image) from the target image, and determines the coordinates (pixel coordinates) of each feature point on the target image (image plane IP; see Figure 3). The position of the centroid of the target 24 is detected as a feature point on the target image.

[0053] In the feature point detection process described above, the feature points detected on the target image are Q ｉ This is shown, and its coordinates (2D coordinates) are (u ｉ , v ｉ ) (where i is a variable (a number uniquely assigned to each feature point) and is a natural number greater than or equal to 2). Note that, if necessary, each feature point Q ｉ Coordinates (u ｉ , v ｉ Apply lens distortion correction to the image.

[0054] Furthermore, point P of an object in three-dimensional space j The coordinates indicating the position of each target 24 on the target plate 14 are (x ｗｊ , y ｗｊ , z ｗｊ If we assume that (where j is a variable (a number uniquely assigned to each object point) and is a natural number greater than or equal to 2), then from the camera projection model shown in Figure 3, we can formulate it as follows: Equation (8).

[0055] In equation (8), K is the camera matrix representing the intrinsic parameters of camera 20, and is known.

[0056] Here, the error function E is defined as shown in equation (9) below.

[0057] The error function E defined by equation (9) is given by the feature points Q on the target image. ｉ and the object point P in three-dimensional space jThis is an error function that shows the correspondence with (points indicating the positions of each target 24), and the error function E is minimized when the combination of these points is in a projection relationship with each other.

[0058] The optimization unit 66 finds the transformation matrix [R|t] that minimizes the error function E through nonlinear optimization. The transformation matrix [R|t] obtained by the optimization unit 66 is the world coordinate system Σ ｗ This shows the self-position (position and orientation) of camera 20.

[0059] The self-position estimation unit 62 stores the information indicating the position and orientation of the camera 20 (camera self-position information) obtained as described above in the storage unit 54. The camera self-position information stored in the storage unit 54 is used when calculating the three-dimensional coordinates of the workpiece using the probe head 12.

[0060] [Target Light Emission Control] In the self-position estimation system 10 according to this embodiment, light emission control is performed in the self-position estimation process to reduce the effect of heat caused by the illumination of the target 24 of the target group 16.

[0061] (Example 1) Figure 4 is a timing chart for explaining the light emission control of the target according to Example 1. Figure 4 shows the light emission control according to Example 1 in comparison with Comparative Example 1.

[0062] As shown in Figure 4, in Comparative Example 1 (continuous illumination), the targets 24 in all target groups (panels) 16 of the target plate 14 continue to emit light while the self-position estimation process is being performed. The camera 20 captures the continuously emitting targets 24 each time self-position estimation is performed (every frame).

[0063] In Comparative Example 1, the entire surface of the target plate 14 emits light continuously, regardless of the timing of the camera 20's shooting and the camera 20's shooting range (field of view). Therefore, unlike the example shown in Figure 8, there is no uneven distribution of heat-generating areas due to the light emission. However, in Comparative Example 1, thermal expansion occurs because heat is continuously generated across the entire surface of the target plate 14. The effect of this thermal expansion increases as the light emission time lengthens and the amount of thermal energy accumulated in the target plate 14 increases.

[0064] In contrast, in Example 1 (pulsed emission), the emission time of the target plate 14 is limited to an emission time T1 determined according to the exposure time TE1 of the camera 20. That is, in Example 1, the target group 16 of the target plate 14 emits pulsed light collectively only for the emission time T1. Here, the emission time T1 and the interval from the end of emission to the start of emission (emission interval) T2 are adjusted considering the effect of heat generated with the emission of light from the target 24. For example, the more susceptible the target plate 14 is to thermal expansion (for example, having a structure with low heat dissipation efficiency, including a material with a large coefficient of linear thermal expansion), the longer the emission interval T2 may be, or the shorter the emission time T1 may be. Furthermore, the emission time T1 and the emission interval T2 may be adjusted according to the light intensity I1 (for example, the amount of light per unit area of ​​the target plate 14). For example, the larger the light intensity I1, the longer the emission interval T2 may be, or the shorter the emission time T1 may be.

[0065] According to Example 1, the effect of heat associated with light emission can be suppressed by shortening the light emission time of the target 24. Furthermore, according to Example 1, the light emission time of the target 24 can be shortened compared to Comparative Example 1, so power consumption due to light emission can be reduced, and energy saving can be achieved.

[0066] In the example shown in Figure 4, the exposure timing of the camera 20 (exposure start time and exposure time TE1) and the light emission timing of the target 24 (light emission start time and light emission time T1) are the same, but they may be different. However, if the exposure time TE1 of the camera 20 is long, it becomes more susceptible to camera shake (for example, shake when the camera 20 moves). Also, if the exposure time TE1 of the camera 20 is long, it becomes more susceptible to ambient light other than the light from the target 24. On the other hand, if the light emission time T1 is long and the light emission interval T2 is short, the heat dissipation efficiency decreases. Therefore, it is preferable to match the exposure time TE1 of the camera 20 with the light emission time T1 of the target 24.

[0067] Furthermore, in Example 1, it is preferable to make the light intensity I1 during pulsed emission greater (brighter) than the light intensity I2 during continuous emission. For example, if the light intensity I1 during pulsed emission is five times the light intensity I2 during continuous emission (I1 = 5 × I2), the exposure time TE1 (= T1) required to obtain the same exposure amount (integral value of light intensity × exposure time and received light amount) as during continuous emission becomes one-fifth of TE2. Thus, according to Example 1, the exposure time TE1 can be shortened, and the effect of camera shake 20 can be suppressed.

[0068] Furthermore, the intensity of ambient light is considered to be lower than the light from target 24, and its change over time is also considered to be small. Therefore, by shortening the exposure time TE1, the amount of ambient light received can be reduced (to a level darker than the amount of light received from target 24). This makes it possible to suppress the influence of ambient light.

[0069] (Example 2) Figure 5 is a timing chart illustrating the target light emission control according to Example 2. Figure 5 shows the light emission control according to Example 2 in comparison with Comparative Example 2. In Figure 5, the timing of the start of pulsed light emission is indicated by an upward arrow.

[0070] As shown in Figure 5, in Comparative Example 2, the interval d2 of the start times of pulsed emission from target 24 is equal. When pulsed emission is performed as in Example 1, the current value supplied to target 24 becomes larger and the current supply time becomes shorter compared to the case of continuous emission. When switching the start and stop of current supply at high speed, high-frequency EMI (Electromagnetic Interference) radiation and conducted noise (EMI noise) may occur during current switching.

[0071] EMI noise has peaks at the power supply switching frequency and its harmonics. Furthermore, as in Comparative Example 2, when the start times of pulse emission from target 24 are equally spaced, the energy of the EMI noise concentrates at the power supply switching frequency and its harmonics, resulting in a large peak value for the EMI noise. Such EMI noise can affect the operation of each part of the self-position estimation system 10 and can cause errors in the self-position estimation process.

[0072] In contrast, in Example 2, the start time of the pulse emission is varied. For example, the interval d1 of the pulse emission start times is set to be non-equal and irregular (random). In Example 2, the start time of the pulse emission is randomized, and the time from the start to the end of the pulse emission and the corresponding exposure time of the camera 20 are kept constant.

[0073] In Embodiment 2, the light emission control unit 72 modulates the switching frequency that switches the supply of current to the target 24 ON / OFF within a certain range. Here, as a modulation method for the switching frequency, for example, a spread spectrum method can be applied. When modulating the switching frequency using a spread spectrum method, for example, a spreading code such as a random sequence, a PN (Pseudorandom Noise) sequence, an M sequence (Maximum Length Sequence), or a uniform random number can be used.

[0074] According to Example 2, by varying the start time of pulse emission, the energy of EMI noise can be dispersed to frequencies around the switching frequency. This reduces the peak value of EMI noise and suppresses the influence of EMI noise on the operation of each part of the self-position estimation system 10.

[0075] In Embodiment 2, the exposure timing of the camera 20, i.e., the exposure trigger signal, may also be modulated in the same manner. That is, the pulse emission time after modulation may be matched with the exposure time of the camera 20. This allows the exposure time of the camera 20 to be shortened in accordance with the pulse emission, thereby suppressing the effects of camera shake and ambient light.

[0076] Furthermore, in Example 2, the start time of pulse emission was randomized, and the time from the start to the end of pulse emission (emission time) and the corresponding exposure time of the camera 20 were kept constant, but this is not limited to this. For example, the emission time (exposure time) for each frame may be different from each other. In this case, the amount of light of the target 24, the emission time and the exposure time of the camera 20 may be adjusted so that the exposure amount (= light amount × exposure time) for each frame is approximately equal. Also, the exposure amounts for each frame do not have to be equal. For example, the exposure amounts for each frame may be made approximately equal by increasing or decreasing the exposure amount through signal processing. Here, "approximately equal" or "approximately equal" is not limited to cases where the exposure values ​​are strictly equal, but also includes cases where they can be treated as substantially equal within a certain error range at the average level of the art.

[0077] (Example 3) In Examples 1 and 2, the entire surface of the target plate 14 was pulsed, but this is not the only option. For example, the target group 16 of the target plate 14 may be divided into multiple groups, and each group may be pulsed in a time-division manner.

[0078] Figures 6 and 7 are perspective views and timing charts, respectively, illustrating the target light emission control according to Embodiment 3.

[0079] In Example 3, the target group 16 of the target plate 14 is divided into groups G1 to G6. As shown in Figure 6, the target groups 16 of groups G1 to G6 are arranged regularly (periodically). Note that the number of groups is not limited to six.

[0080] Figures 6 and 7 show the same pattern applied to the emission time of each target group 16 belonging to the same group.

[0081] As shown in Figure 7, in Embodiment 3, pulse emission of group A1 of the target group 16, which includes the portion overlapping with the field of view of the camera 20, and pulse emission of groups G1 to G6 are performed sequentially in a time-division manner. Here, the light emission control unit 72 sets the emission timing of the pulse emission of group A1 in accordance with (approximately matching) the exposure time of the camera 20. In addition, the light emission control unit 72 sets the emission timing of the pulse emission of groups G1 to G6 other than group A1 during times other than the exposure time of the camera 20. Then, the emission cycle of groups A1 and G1 to G6 is repeated during the self-position estimation process.

[0082] Here, group A1 of the target group 16 that overlaps with the field of view of camera 20 changes (moves) over time as camera 20 moves. Here, group A1 at the start of the self-position estimation process may be predetermined in association with the initial position of camera 20. Alternatively, group A1 during the self-position estimation process may be detected by a detection unit (e.g., a position sensor, linear encoder, or linear scale) for detecting the position of camera 20 or probe head 12. Such a detection unit may be provided in the self-position estimation system 10 or independently of the self-position estimation system 10. Furthermore, group A1 during the self-position estimation process may be determined from camera self-position information obtained by the self-position estimation unit 62. If the initial position is used as group A1 at the start of the self-position estimation process and the subsequent movement of group A1 is determined from camera self-position information, the above-mentioned detection unit can be omitted.

[0083] In the example shown in Figure 7, the start times of pulse emission for group A1 and groups G1 to G6 are equally spaced, but this is not limited to this. Therefore, as in Example 2, there may be variation in the start times of pulse emission for group A1 and groups G1 to G6. In this case, the amount of light and emission time of the target 24 and the exposure time of the camera 20 may be adjusted so that the exposure amount for each frame is approximately the same.

[0084] According to Example 3, in addition to the localized emission of group A1 of the target group 16 that overlaps with the field of view of the camera 20, time-division emission is performed for each group G1 to G6, thereby preventing uneven distribution of heat-generating areas.

[0085] Furthermore, according to Example 3, EMI noise can be reduced by distributing the drive current supplied to the target plate 14 over time.

[0086] Furthermore, according to Example 3, by distributing the drive current supply, the drive power required during pulsed emission is reduced compared to the case where the entire surface of the target plate 14 is illuminated (see the light intensity in the case of full surface illumination in Figure 7). In other words, in Example 3, a power supply with low supply capacity can be used, which can reduce the overall cost of the device.

[0087] Furthermore, the order of light emission for each group is not limited to the order of group A1 and G1-G6 shown in Figure 7. For example, the order of light emission for group A1 and G1-G6 may differ in each repeating cycle. Alternatively, group A1 may be illuminated in each cycle, while only a portion of group G1-G6 (for example, only group G1-G3 in one cycle, and only group G4-G6 in the next cycle) may be illuminated. In other words, as long as the current supply to the target plate 14 can be distributed over time to mitigate the localization (uneven distribution) of heat generation, the number of groups of target group 16 that emit pulsed light in one cycle and their order of light emission are not limited.

[0088] 10...Self-position estimation system, 12...Probe head, 14...Target plate, 16...Target group, 18...Probe, 20...Camera, 24...Target, 50...Self-position estimation device, 52...Calculation processing unit, 54...Storage unit, 60...Image acquisition unit, 62...Self-position estimation unit, 70...Camera control unit, 72...Light emission control unit

Claims

1. A light emission control device comprising: a camera control unit that controls the exposure timing of the camera when performing self-position estimation of the camera that has photographed multiple targets; and a light emission control unit that causes the multiple targets to emit pulsed light according to the exposure timing of the camera.

2. The light emission control device according to claim 1, wherein the light emission control unit causes the plurality of targets to emit pulsed light simultaneously.

3. The light emission control device according to claim 1, wherein the light emission control unit synchronizes the exposure timing of the camera with the light emission timing of the plurality of targets.

4. The light emission control device according to claim 1, wherein the light emission control unit randomly sets the interval between the light emission start times of the plurality of targets.

5. The light emission control device according to claim 1, wherein the light emission control unit causes the target among the plurality of targets that overlaps with the shooting range of the camera to emit light during the exposure time of the camera, and causes the plurality of targets to emit light in a time-division manner in groups outside of the exposure time of the camera.

6. A self-position estimation device comprising: a light emission control device according to any one of claims 1 to 5; and a self-position estimation unit that estimates the self-position of the camera based on images of the plurality of targets captured by the camera.

7. A light emission control method comprising: controlling the exposure timing of a camera when performing self-position estimation of a camera that has photographed multiple targets; and causing the multiple targets to emit pulsed light according to the exposure timing of the camera.

8. A self-position estimation method comprising the steps of: controlling the emission of light from the plurality of targets using the light emission control method described in claim 7; and estimating the self-position of the camera based on images of the plurality of targets captured by the camera.

Images