Distance measuring device

Abstract

This invention provides a distance measuring device that can determine the mask pixel in real time according to the time elapsed since the start of pulsed light emission, thereby improving the accuracy of distance measurement to the workpiece. [Solution] The distance measuring device comprises a light-emitting unit that emits pulsed light, a light-receiving unit having a plurality of pixels, each receiving detection light reflected from the workpiece and generating a received signal, a mask determination unit that determines a mask pixel among the plurality of pixels of the light-receiving unit according to the time elapsed since the start of pulse light emission, a mask control unit that performs mask processing to restrict the use of the received signal of the mask pixel for measuring the distance to the workpiece, and a distance measuring unit that measures the distance to the workpiece based on the mask processing and the received signal of each pixel.

Description

Technical Field

[0004] , ,

[0005] , , ,

[0001] The present disclosure relates to a distance measuring device.

Background Art

[0002] Conventionally, there is known a lidar device including a pulsed light irradiation unit that irradiates pulsed light so as to scan a target field of view, and a light receiving system that receives reflected light of the pulsed light reflected by an object existing in the target field of view. In this lidar device, the light receiving system includes at least an imaging optical element and a TOF sensor having a light receiving unit. The target field of view is projected onto the light receiving unit by the imaging optical element. The TOF sensor sets an activation region in a part of the light receiving unit according to the scan of the pulsed light, and measures the distance to the object using a signal from the activation region (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the lidar device of Patent Document 1, pulsed light is projected at a constant period, and the scan angle of the mirror is changed according to the projection timing. Then, when the lidar device changes the scan angle, it changes the position of the activation region where the signal light enters.

[0005] Furthermore, in a TOF sensor, the light that enters the light-receiving unit a short time after the pulse light is emitted is reflected light from a detection object located close to the device. In this case, since the detection object is at a close distance, the reflected light enters a wide area of ​​the light-receiving unit. On the other hand, the light that enters the light-receiving unit a long time after the pulse light is emitted is reflected light from a detection object located far from the device. In this case, since the detection object is at a far distance, the reflected light enters a narrow area of ​​the light-receiving unit. In other words, the area in the light-receiving unit where reflected light from the detection object enters changes depending on the elapsed time since the pulse light was emitted. In Patent Document 1, the activation area does not follow this change in the light-entering area due to the elapsed time, so the accuracy of distance measurement based on the signal obtained by the light-receiving unit becomes insufficient.

[0006] This disclosure provides a distance measuring device that can determine a mask pixel according to the time elapsed since the start of pulsed light emission, thereby improving the accuracy of distance measurement to a workpiece. [Means for solving the problem]

[0007] One aspect of the present disclosure is a distance measuring device for measuring the distance to a workpiece, comprising: a light-emitting unit that emits pulsed light; a light-receiving unit having a plurality of pixels, each of which receives detection light reflected from the workpiece and generates a received signal; a mask determination unit that determines a mask pixel among the plurality of pixels of the light-receiving unit according to the time elapsed since the start of pulsed light emission; a mask control unit that performs a masking process to restrict the use of the received signal of the mask pixel for measuring the distance to the workpiece; and a distance measuring unit that measures the distance to the workpiece based on the masking process and the received signal for each pixel. [Effects of the Invention]

[0008] According to this disclosure, the mask pixel can be determined in real time according to the time elapsed since the start of pulsed light emission, thereby improving the accuracy of distance measurement to the workpiece. [Brief explanation of the drawing]

[0009] [Figure 1] Block diagram showing an example configuration of a distance measuring device in an embodiment of this disclosure. [Figure 2] A diagram illustrating mask settings and distance measurement without mask processing, using comparative examples. [Figure 3A] This figure shows the first example of the light-receiving spot and mask at different distances to the test workpiece. [Figure 3B] This figure shows a second example of the light-receiving spot and mask at different distances to the test workpiece. [Figure 4] A diagram showing an example of the projection axis and reception axis of a distance measuring device. [Figure 5] This figure shows the first example of the timing of light emission, the timing of light reception, and a mask corresponding to the timing of the received light. [Figure 6] This figure shows a second example of the timing of light emission, the timing of light reception, and a mask corresponding to the timing of the received light. [Figure 7] This figure shows the first example of multiple mask settings and mask processing. [Figure 8] A second example of multiple mask settings and mask processing is shown in this figure. [Figure 9] This figure shows a third example of multiple mask settings and mask processing. [Figure 10] Figure 4 shows an example of multiple mask settings and mask processing. [Figure 11] Figure 5 shows an example of multiple mask settings and mask processing. [Modes for carrying out the invention]

[0010] The embodiments will be described in detail below, with reference to the drawings as appropriate. However, unnecessary details may be omitted. For example, detailed explanations of already well-known matters or explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding for those skilled in the art. The accompanying drawings and the following explanation are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter described in the claims.

[0011] In addition, the "part" or "device" referred to in the embodiments is not limited to a physical configuration mechanically realized by hardware, but also includes those in which the functions of the configuration are realized by software such as a program. Also, even if the function of one configuration is realized by two or more physical configurations, or the functions of two or more configurations are realized by one physical configuration, it does not matter.

[0012] FIG. 1 is a block diagram showing a configuration example of a distance measurement device 100 according to an embodiment of the present disclosure. The distance measurement device 100 derives (e.g., calculates) the flight time of light according to the TOF (Time Of Flight) method and measures (e.g., calculates) the distance based on the flight time. The flight time is the time as the difference between the light emission timing (light emission time) of a predetermined light emission light (e.g., light emission pulse) and the light reception timing (light reception time) of the light reception light (e.g., light reception pulse) reflected by the detection object. Also, the distance measurement device 100 detects, for example, the presence or absence of an object (workpiece) to be detected based on the flight time of light according to the TOF method, or detects (measures) the distance between the distance measurement device 100 and the workpiece. The distance measurement device 100 is a TOF sensor, a distance measurement sensor, an object detection sensor, etc., and is, for example, a one-dimensional distance measurement device (1D-TOF).

[0013] The distance measurement device 100 includes a light emission unit 110, a light collection unit 120, a light reception unit 130, a control unit 140, a distance measurement unit 150, a display control unit 155, and an output unit 160. The light emission unit 110 includes a light emission lens 111, a light emission element 112, and a light emission circuit 113. The light collection unit 120 includes a light reception lens 121. The control unit 140 includes a timing generation unit 141, a mask generation unit 142, and a mask control unit 143.

[0014] The light emission unit 110 emits light. The light emission unit 110 may emit light multiple times, or may emit light according to a predetermined light emission cycle, for example.

[0015] The projection lens 111 is disposed in front of the projection element 112 (the side from which light exits), and collects or diffuses the light projected from the projection element 112.

[0016] The projection element 112 includes a light-emitting element such as a laser diode, and projects predetermined light. The projection element 112 projects light in a predetermined direction, for example. The projection element 112 projects invisible light (e.g., infrared light), and may project visible light. The light projected by the projection element 112 (also referred to as projection light) can be reflected by the workpiece 50, for example. The projection element 112 projects light according to the projection conditions (e.g., projection timing, projection period, number of projection times) determined by the control unit 140. The projection light EL is pulse light, for example. The projection circuit 113 drives the projection element 112 according to the projection conditions (e.g., the projection timing generated by the timing generation unit 141).

[0017] The condensing unit 120 condenses the light incident on the condensing unit 120.

[0018] The light receiving lens 121 is disposed in front of the light receiving element 131 (the side from which light enters), and condenses the light incident on the light receiving lens 121. The condensed light may include the detection light reflected by the workpiece 50.

[0019] The light receiving unit 130 receives the light condensed by the condensing unit 120.

[0020] The light receiving element 131 includes a light receiving element such as a photo diode (PD), and receives predetermined light. The light receiving element 131 receives invisible light (e.g., infrared light), and may receive visible light. The light received by the light receiving element 131 (also referred to as received light) may include the light in which the projection light EL projected by the projection element 112 is condensed by the condensing unit 120 after being reflected by the workpiece 50. The light receiving element 131 generates a received signal from the received light RL.

[0021] Furthermore, the light-receiving element 131 has multiple pixels (for example, multiple pixels), and each pixel receives the light-receiving light RL. Based on the light-receiving light RL of each pixel, the light-receiving element 131 generates a light-receiving signal for each pixel.

[0022] The light receiving circuit 132 performs IV conversion (current-to-voltage conversion) on the received light signal and amplifies the signal. Therefore, the light receiving circuit 132 performs IV conversion on the received light signal for each pixel and amplifies the signal. The light receiving circuit 132 may also include a comparator circuit. The comparator circuit outputs a predetermined high-level signal when the signal level of the received light signal is above a predetermined threshold, and outputs a predetermined low-level signal when the signal level of the received light signal is below the predetermined threshold. In other words, the comparator circuit generates a binarized received light signal.

[0023] The distance measuring device 100 includes a processor and memory (not shown). The processor may include an MPU (Microprocessing Unit), a CPU (Central Processing Unit), a DSP (Digital Signal Processor), etc. The processor may also be composed of various integrated circuits (e.g., LSI (Large Scale Integration), FPGA (Field Programmable Gate Array)). The processor implements various functions by executing programs held in memory. The processor includes various functional units, such as a control unit 140, a distance measuring unit 150, and a display control unit 155.

[0024] The memory may include RAM and ROM, and may also include other storage devices. The memory may include volatile memory and non-volatile memory. The memory may be detachable from the distance measuring device 100. The memory includes various information, data, etc. For example, the memory may hold information about the mask, which will be described later.

[0025] The control unit 140 controls the processing of each part of the distance measuring device 100.

[0026] The timing generation unit 141 generates the light emission timing. The light emission timing is generated, for example, to match a predetermined light emission period. The timing generation unit 141 may also generate light emission conditions (e.g., light emission period, number of light emission cycles) including the light emission timing. Information on the light emission conditions may be stored in memory. The timing generation unit 141 notifies the light emission conditions, including the light emission timing, of the light emission circuit 113 of the light emission unit 110. Note that the light emission timing does not have to be periodic.

[0027] The mask generation unit 142 generates a mask MK. A mask MK is a set of mask pixels, which are the pixels on the light-receiving element 131 that will undergo the masking process described later. A mask MK is generated for each pixel included in the light-receiving unit 130. Therefore, as the pixels of the light-receiving element 131 are subdivided, the shape of the mask MK can be precisely set. Multiple types of mask MKs may be provided, meaning that multiple mask MKs with different mask pixel positions and ranges may be provided. Information about at least one mask MK is stored in memory.

[0028] Furthermore, the mask generation unit 142 has a timer. The mask generation unit 142 recognizes the time elapsed since the start of light emission EL (also referred to as the light emission time) according to the time measured by the timer. The mask generation unit 142 determines (sets) which mask MK to apply according to the light emission time. Therefore, the position and shape of the mask MK relative to the light receiving element 131 change according to the light emission time. Note that "according to the light emission time," that is, "according to the time elapsed since the start of light emission," means that the mask pixels also change according to the change in time, and that the mask pixels are determined in accordance with time. "According to time" includes switching at predetermined intervals as well as switching in real time.

[0029] The mask control unit 143 performs a masking process SM based on the generated mask MK. The masking process SM is a process that restricts the use of the mask pixel signals for measuring the distance to the workpiece 50. A specific example of the masking process SM will be described later. The masking process SM reduces the influence of the mask pixel signals on the distance measurement of the workpiece 50. Alternatively, the mask control unit 143 may instruct other components (e.g., the light receiving unit 130, the distance measuring unit 150) to perform the masking process SM instead of the mask control unit 143 performing it. The mask control unit 143 sends the light receiving signal from the light receiving unit 130, that is, the light receiving signal from each pixel of the light receiving element 131, to the distance measuring unit 150.

[0030] The distance measuring unit 150 acquires the received light signal from the mask control unit 143. Specifically, the distance measuring unit 150 acquires the received light signal for each pixel of the light receiving element 131 that has been processed by the mask control unit 143. The distance measuring unit 150 converts the received light signal for each pixel into a distance value. For example, the distance measuring unit 150 acquires information on the emission timing of the emitted light EL and calculates the time of flight (TOF) for each pixel based on the emission timing of the emitted light EL and the received light timing indicated by the received light signal for each pixel. Then, the distance measuring unit 150 calculates the distance value for each pixel based on the TOF and the speed of light.

[0031] The distance measuring unit 150 measures (for example, calculates) the distance (distance value) to the workpiece 50 based on the distance value of each pixel. The distance measuring unit 150 may calculate the distance value to the workpiece 50 by averaging the distance values ​​of each pixel, or it may calculate a statistical value other than the average value as the distance value by performing statistics other than averaging. The measured distance from the distance measuring device 100 to the workpiece 50 is also called the measured distance value. The distance measuring unit 150 sends information including information about the measured distance value to the display control unit 155. The distance measuring unit 150 is capable of deriving the distance value through calculation, and can also be called a distance calculation unit or distance calculation unit.

[0032] The display control unit 155 controls the display to show various types of information. These types of information may include, for example, information about each pixel of the light-receiving element 131, information about the mask MK, i.e., information about the mask pixels, information about the light-receiving signal of each pixel, information about the distance value of each pixel, information about the measured distance value, or other information.

[0033] The display control unit 155 may display various types of information on the output unit 160, or it may display various types of information on an external device (for example, an external PC or display device). When the display control unit 155 displays various types of information on an external device, it may transmit various types of information and display instructions to the external device via a communication cable or communication device provided by the distance measuring device 100. The external device acquires various types of information and display instructions from the distance measuring device 100 and displays various types of information according to the display instructions. The distance measuring unit 150 sends information including information related to the measured distance value to the output unit 160.

[0034] The output unit 160 outputs various types of information. The output unit 160 may output data in a way that is imperceptible to the user of the distance measuring device 100 (for example, by outputting data to an output line or by storing data in memory). Alternatively, the output unit 160 may be equipped with a display unit such as an indicator light (e.g., an LED), a display, or a speaker, and output data in a way that is perceptible to the user (i.e., by displaying or sounding the data to the user). The output unit 160 may output information such as the amount of light received by the light receiving element 131 (signal level of the received light signal), the measured distance to the workpiece 50, and whether or not the workpiece 50 is present.

[0035] Next, we will explain the details of the masking process SM.

[0036] Multiple masking processes (e.g., masking processes SM1 to SM4) are possible as masking processes SM, as illustrated below. The masking control unit 143 controls the system to execute at least one of the multiple masking processes SM.

[0037] The masking process SM1 is a process in which a light-shielding member (shutter) that blocks the received light RL, including the detected light, is placed on the mask pixel 130m. In other words, the light-receiving unit 130 may, according to instructions from the mask control unit 143, drive a motor (not shown) to place the light-shielding member in front of the light-receiving element 131. Multiple light-shielding members may be prepared in advance to match multiple masks MK. The light-shielding member is physically placed in real space and blocks the received light RL directed toward the mask MK (mask pixel 130m). In this case, assuming that ambient light is not taken into account, the mask pixel 130m does not receive the detected light, so the amount of received light RL, i.e., the signal level of the mask pixel signal, becomes 0. Note that the light-shielding member may reduce the light without making the signal level of the received light RL 0.

[0038] The masking process SM2 is a process that prevents the received signal of the mask pixel 130m from being sent to the distance measuring unit 150. In other words, the light receiving unit 130 does not have to send the mask pixel signal to the mask control unit 143 according to instructions from the mask control unit 143. For example, the light receiving unit 130 may have a switch to toggle each pixel of the light receiving element 131 on or off. The light receiving unit 130 may prevent the generation of a mask image signal by turning off the switch for the mask pixel 130m. Alternatively, the light receiving unit 130 or the control unit 140 may have a switch to toggle the on / off state (connected state and disconnected state) of the transmission path through which the signal is transmitted from the light receiving circuit 132 to the mask control unit 143. The light receiving unit 130 or the control unit 140 may prevent the mask image signal from being sent to the mask control unit 143 by turning off the switch for the transmission path.

[0039] The masking process SM3 is a process that does not calculate the distance value of the mask pixel based on the light received signal of the mask pixel. In other words, the distance measuring unit 150 does not need to convert the mask pixel signal into a distance value according to instructions from the mask control unit 143. In this case, the distance measuring unit 150 does not generate a distance value for the mask pixel.

[0040] The masking process SM4 is a process that excludes the distance values ​​of the mask pixels from the distance values ​​used to measure the distance to the workpiece 50. In other words, the distance measuring unit 150 does not have to use the distance values ​​of the mask pixels in calculating the measured distance values, that is, it does not have to use them in the statistics (e.g., averaging) of the distance values ​​of each pixel, according to instructions from the mask control unit 143.

[0041] The mask control unit 143 controls the execution of at least one mask processing SM from among several types of mask processing SMs. The mask control unit 143 may specify which mask processing to perform, for example, by the user via an input device.

[0042] Figure 2 illustrates the mask setting and the first example of distance measurement without mask processing, using a comparative example.

[0043] In Figure 2, the photodetector 131 contains 25 pixels arranged in a 5x5 grid. Each pixel receives the light RL. In the photodetector 131, pixels near the center receive the light RL, while pixels near the edges, such as the four corners, do not. In this case, for pixels that receive the light RL, the amount of light received is large, and because the signal level of the received signal is above the threshold, the received pulse becomes High, and a normal distance value (e.g., 2.2m) is derived according to the time position of the received pulse. On the other hand, for pixels that do not receive the light RL, the amount of light received is small, and because the signal level of the received signal is below the threshold, the received pulse becomes Low, and an abnormal distance value (e.g., 3.4m) is derived because the time position of the received pulse cannot be determined. The comparative example will include both normal and abnormal distance values. Therefore, when the distance values ​​of each pixel are averaged, a detected distance (measured distance value) of 2.6m is obtained. As a result, there is a discrepancy between the measured distance value and the normal distance value, and the accuracy of the measured distance value becomes insufficient.

[0044] In contrast, in this embodiment, the distance measuring device 100 can prevent abnormal distance values ​​from being used in measuring the distance to the workpiece 50 by mask setting and mask processing SM. Therefore, even if the distance values ​​of each pixel are averaged, the distance measuring device 100 can obtain a value close to the normal distance value (for example, 2.2m), thus suppressing the discrepancy between the measured distance value and the normal distance value and improving the accuracy of the measured distance value.

[0045] Next, we will explain how to generate the mask MK.

[0046] Before actually measuring the distance to the workpiece 50 to be detected, the distance measuring device 100 places a test workpiece 50T at a predetermined position relative to the distance measuring device 100 and emits test light onto the test workpiece 50T. The light receiving unit 130 receives the test detection light reflected by the test workpiece 50T and generates a test light reception signal. In this case, the light receiving unit 130 generates a test light reception signal for each pixel. Based on the test light reception signal for each pixel, the mask generation unit 142 recognizes the detection light receiving pixels that received the test detection light and the detection light non-receiving pixels that did not receive the test detection light. The set of detection light receiving pixels is also called a light receiving spot SP. The mask generation unit 142 generates a mask MK using the detection light non-receiving pixels as mask pixels 130m. The mask generation unit 142 stores the information of the generated mask MK in memory.

[0047] The position of the test workpiece 50T relative to the distance measuring device 100 is movable, and the distance between the distance measuring device 100 and the test workpiece 50T is variable. The distance measuring device 100 evaluates the relationship between the distance to the test workpiece 50T and the light-receiving spot SP at each distance between the distance measuring device 100 and the test workpiece 50T.

[0048] Figure 3A shows a first example of the light-receiving spot SP and mask MK at different distances to the test workpiece 50T. The distances to the test workpiece 50T are exemplified as X1(m) (e.g., 1m), X2(m) (e.g., 2m), X3(m) (e.g., 3m), X4(m) (e.g., 4m), and X5(m) (e.g., 5m). Figure 3 also shows the light-receiving spot SP in front of the light-receiving element 131. Furthermore, Figure 3 shows examples of masks MKa, MKb, MKc, MKd, and MKe.

[0049] The closer the test workpiece 50T is to the distance measuring device 100, the wider the range of light RL received from the test workpiece 50T becomes, and the larger the light-receiving spot SP becomes. As a result, the range of pixels that do not receive detected light becomes narrower, and the mask MK becomes smaller. In Figure 3, mask MKa is the smallest, and as an example, mask MKa may include the state where there is no mask MK. On the other hand, the further the test workpiece 50T is from the distance measuring device 100, the narrower the range of light RL received from the test workpiece 50T becomes, and the smaller the light-receiving spot SP becomes. As a result, the range of pixels that do not receive detected light becomes wider, and the mask MK becomes larger. Furthermore, the shape of the light-receiving spot SP may have a concave shape corresponding to the area of ​​the light-emitting element 112.

[0050] Furthermore, if the light-receiving spot SP has the concave shape described above, it is preferable to make the mask shape match the shape of the light-receiving spot SP as closely as possible, as shown in Figure 3B. Figure 3B shows a second example of the light-receiving spot SP and mask MK for each distance to the test workpiece 50T. With this configuration, the distance measuring device 100 can perform distance measurement (signal processing) while eliminating noise components in distance measurement, which is expected to improve the accuracy of distance measurement to the workpiece 50.

[0051] Figure 4 shows an example of the light projection axis and light receiving axis of the distance measuring device 100. Figure 4 shows a side view of the positional relationship between the light receiving lens 121 and light receiving element 131 of the distance measuring device 100 and the test workpiece 50T.

[0052] In the distance measuring device 100, for example, the light-emitting axis and the light-receiving axis are not coaxial. In this case, the center position of the light-receiving spot SP changes depending on the distance to the test workpiece 50T. For example, comparing the cases where the distance to the test workpiece 50T is between 1m and 5m, the position of the light-receiving spot SP is at the lowest when the distance to the test workpiece 50T is 1m, and at the uppermost position when the distance to the test workpiece 50T is 5m. The mask generation unit 142 generates a mask MK for pixels in the light-receiving element 131 where the light-receiving spot SP is absent. Note that in the distance measuring device 100, the light-emitting axis and the light-receiving axis may be coaxial.

[0053] In Figure 3, the closer the test workpiece 50T is to the distance measuring device 100, the smaller the mask MK becomes. As the test workpiece 50T moves away from the distance measuring device 100, the mask MK appears near the four corners of the light-receiving element 131 and gradually becomes larger. In Figure 3, the center position of the mask MK is in the same position, but this is not limited to this. For example, if the light-emitting axis and light-receiving axis of the distance measuring device 100 are not coaxial, the center position of the light-receiving spot SP gradually changes according to the distance between the test workpiece 50T and the distance measuring device 100. In this case, the center position of the mask MK may move according to the distance between the test workpiece 50T and the distance measuring device 100 in accordance with the center position of the light-receiving spot SP.

[0054] Furthermore, the distance measuring device 100 measures distance optically, but the speed of light is constant under the same environment, and the time corresponding to the distance (elapsed light emission time) is uniquely determined. Therefore, the light receiving spot SP is determined according to the distance to the test workpiece 50T, and thus it is determined according to the elapsed light emission time. Consequently, the mask MK is also determined according to the distance to the test workpiece 50T, and thus it is determined according to the elapsed light emission time. For example, X1 (m) corresponds to Y1 (seconds). X2 (m) corresponds to Y2 (seconds). X3 (m) corresponds to Y3 (seconds). X4 (m) corresponds to Y4 (seconds). X5 (m) corresponds to Y5 (seconds). In other words, the mask generation unit 142 generates a mask MK corresponding to the distance to the test workpiece 50T, that is, a mask MK corresponding to the elapsed light emission time.

[0055] In Figure 3, the distance measuring device 100 performed the confirmation of the light-receiving spot SP and the generation of the mask MK in 1m units, but the confirmation of the light-receiving spot SP and the generation of the mask MK may also be performed in other units of distance (for example, 10cm units, 1cm units).

[0056] Next, we will explain the operation of the distance measuring device 100 when measuring the distance to the workpiece 50.

[0057] Figure 5 shows a first example of the emission timing of the light source EL as an emission pulse, the reception timing of the light source RL as a reception pulse, and the mask MK corresponding to the timing of the light source RL. The horizontal axis in Figure 5 represents time. Figure 5 illustrates that the distance measuring device 100 directly measures the distance to the workpiece 50 according to the TOF method.

[0058] The projected light EL is projected, for example, according to the projection period. As discussed above with test workpiece 50T, the closer the distance from the distance measuring device 100 to the workpiece 50, the shorter the time it takes for the light to travel back and forth between the distance measuring device 100 and the workpiece 50. Also, as mentioned above, the closer the distance to the workpiece 50, the larger the light receiving spot SP and the smaller the mask MK. Therefore, the mask control unit 143 controls the mask MK to decrease in accordance with the projection time. For example, the mask control unit 143 selects and determines (sets) a mask MK held in memory according to the projection time.

[0059] Figure 5 illustrates the sequential reduction of mask MK every Y1 second. For example, the mask control unit 143 selects and sets mask MKa 0 to Y1 seconds after the start of light emission from the light source EL (for example, immediately after 0 seconds as shown in the timing of Figure 5). Mask MKa is the smallest range mask MK and includes cases where no mask MK is provided (no pixels are masked). The mask control unit 143 selects and sets mask MKb 1 to Y2 seconds after the start of light emission from the light source EL (for example, immediately after Y1 second in Figure 5). The mask control unit 143 selects and sets mask MKc 1 to Y3 seconds after the start of light emission from the light source EL (for example, immediately after Y2 seconds in Figure 5). The mask control unit 143 selects and sets mask MKd 1 to Y3 to Y4 seconds after the start of light emission from the light source EL (for example, immediately after Y3 seconds in Figure 5). As an example, the mask control unit 143 selects and sets the mask MKe 4 to 5 seconds after the start of light emission from the light source EL (for example, immediately after 4 seconds in Figure 5).

[0060] More specifically, there are, for example, six mask switching periods (or mask switching timings / light reception timings) in Figure 5. Mask MKa is set at the first mask switching timing (0 seconds), and this mask MKa remains set during the first mask switching period (0 seconds to Y1 second). As soon as the first timing ends, at the second timing (Y1 second), the mask switches from MKa to Mkb and is set to MKb. During the second mask switching period (Y1 second to Y2 second), the mask remains set to MKb. Similarly, as soon as the second timing ends, at the third timing (Y2 second), the mask switches from MKb to Mkc. During the third mask switching period (Y2 second to Y3 second), the mask remains set to MKc. During the fourth mask switching period (Y3 second to Y4 second), the mask remains set to MKd. During the fifth mask switching period (Y4 second to Y5 second), the mask remains set to MKe. During the sixth mask switching period (Y5 second to Y6 second), the mask remains set to MKf. In this way, each mask switches sequentially at each timing, and the mask remains set during each mask switching period.

[0061] Furthermore, Figure 5 shows, as an example, that the received light RL is received 2.5 seconds after the start of light emission EL. At this timing, the mask MKc is set. The receiving spot SP in the light receiving element 131 where the received light RL is received is located inside the mask MKc, meaning that all or most of the received light RL is received by pixels where the mask MKc is not set (also called unmasked pixels).

[0062] Therefore, the distance measuring device 100 can accurately measure the distance to the workpiece 50 based on the distance value obtained as a normal value, without using the mask pixel signal (mask pixel 130m) or the mask processing SM applied to the mask pixel signal to measure the distance to the workpiece 50.

[0063] The mask switching period is set to the order of nanoseconds (ns). It should be noted that this nanosecond order is just one example; it does not have to be this order. For example, it could be in the order of seconds (S), milliseconds (ms), microseconds (μm), or femtoseconds (fs).

[0064] Figure 6 shows a second example of the emission timing of the light source EL as an emission pulse, the reception timing of the light source RL as a reception pulse, and the mask MK corresponding to the timing of the light source RL. The horizontal axis in Figure 6 represents time. Figure 6 illustrates how the distance measuring device 100 measures the distance to the workpiece 50 according to the indirect TOF method.

[0065] In the distance measuring device 100, there are two time intervals: a first period T11 in which gate 1 is turned on and gate 2 is turned off, and a second period T12 in which gate 2 is turned on and gate 1 is turned off. The first period T11 and the second period T12 appear alternately.

[0066] In the case of an indirect TOF 2-Tap system, for example, at least two types of masks are prepared and stored in memory: a mask MK used in the first period T11 (e.g., mask MKa) and a mask MK used in the second period T12 (e.g., mask MKc). The mask control unit 143 selects and sets the mask MK according to the light emission elapsed time, specifically based on whether the light emission elapsed time is included in the first period T11 or the second period T12.

[0067] The projected light EL is projected over the first period T11, but not during the second period T12. The received light RL, obtained by the reflection of the projected light EL by the workpiece 50, is received over the latter half of the first period T11 and the first half of the second period T12. The receiving spot SP of the received light RL received in the latter half of the first period T11 is located within the pixels inside the mask pixels where mask MKa is set. If mask MK is not set as mask MKa, then all pixels of the light-receiving element 131 are assumed to be located within the pixels inside the mask pixels. The receiving spot SP of the received light RL received in the first half of the second period T12 is also located within the pixels inside the mask pixels where mask MKc is set. The distance measuring unit 150 calculates a distance value for each pixel based on the ratio of the light reception time in the first period T11 (the time from the start to the end of light reception in the first period T11) and the light reception time in the second period T12 (the time from the start to the end of light reception in the second period T12).

[0068] Therefore, the distance measuring device 100 can accurately measure the distance to the workpiece 50 based on the distance value obtained as a normal value, without using the mask pixel signal (mask pixel 130m) or the mask processing SM applied to the mask pixel signal to measure the distance to the workpiece 50.

[0069] Note that Figure 6 shows an example where at least two types of masks are provided, one used in the first period T11 (e.g., mask MKa) and one used in the second period T12 (e.g., mask MKc), but this is not limited to this. The masks used in the first period T11 and the second period T12 may have the same mask shape; in other words, there may be only one type of mask MK. Furthermore, even if there are at least two types of masks, one used in the first period T11 (e.g., mask MKa) and one used in the second period T12 (e.g., mask MKc), it is possible to switch between masks MKa and MKc during the first illumination, but use only mask MKc during subsequent illuminations.

[0070] Although Figure 6 illustrates a two-tap indirect TOF method, the distance measuring device 100 of this embodiment can also be applied to other tapping methods of the indirect TOF method (for example, a four-tap method).

[0071] Next, we will explain the process of setting multiple masks and the mask processing SM.

[0072] The mask generation unit 142 can set multiple masks MK for the light-receiving element 131 at different timings. In other words, the mask generation unit 142 can change the mask shape. In this case, the mask control unit 143 can perform one or more types of mask processing SM on mask pixels for which different masks MK have been set at different timings.

[0073] Figure 7 shows a first example of multiple mask settings and mask processing SM. In Figure 7, similar to Figure 5, it is illustrated that the workpiece 50 is positioned relative to the distance measuring device 100 so that it receives the receiving light RL at Y2.5 seconds from the start of the emission of the emitted light EL.

[0074] More specifically, there are, for example, six mask switching periods (or mask switching timings / light reception timings) in Figure 7. Mask MKa is set at the first mask switching timing (0 seconds), and this mask MKa remains set during the first mask switching period (0 seconds to Y1 second). As soon as the first timing ends, at the second timing (Y1 second), the mask switches from MKa to Mkb and is set to MKb. During the second mask switching period (Y1 second to Y2 second), the mask remains set to MKb. Similarly, as soon as the second timing ends, at the third timing (Y2 second), the mask switches from MKb to Mkc. During the third mask switching period (Y2 second to Y3 second), the mask remains set to MKc. During the fourth mask switching period (Y3 second to Y4 second), the mask remains set to MKd. During the fifth mask switching period (Y4 second to Y5 second), the mask remains set to MKe. During the sixth mask switching period (Y5 second to Y6 second), the mask remains set to MKf. In this way, each mask switches sequentially at each timing, and the mask remains set during each mask switching period. Note that in Figure 7, some details are omitted compared to Figure 5, and two consecutive mask switching periods (for example, the first and second mask switching periods, the third and fourth mask switching periods, and the fifth and sixth mask switching periods) are shown together as a single mask switching period, with masks MKa, MKc, and MKe being used as examples. Note that Y6 seconds corresponds to 0 seconds in the next cycle.

[0075] In Figure 7, the light source EL is emitted multiple times, the light source RL including the detection light is received multiple times, and a different mask MK is set for each received light source RL.

[0076] The distance measuring device 100 emits the first emitted light EL and receives the first received light RL, and sets the first mask MK (for example, mask MKc). The distance measuring device 100 performs mask processing SM using mask MKc and measures (for example, calculates) the distance to the workpiece 50 based on the received signal of each pixel, that is, obtains the first measured distance value (D) (for example, about 2m to 3m).

[0077] The mask control unit 143 determines the second mask MK to be applied during the second light reception based on the first measured distance value (D). For example, the second mask MK is larger than the first mask MK, and the mask MK is determined to be mask MKd. Therefore, the mask control unit 143 can set a mask MK that is appropriate to the actual distance to the workpiece 50.

[0078] The distance measuring device 100 emits a second light EL and receives a second light RL. Mask MKd is set as the second mask MK. Based on the received signal of each pixel and the mask processing SM using mask MKd, the distance measuring device 100 measures (for example calculates) the distance to the workpiece 50, that is, obtains the second measured distance value (D') (for example 2.5m).

[0079] In other words, the mask control unit 143 sets the first mask MK according to the elapsed light emission time. Then, the mask control unit 143 sets the second mask MK according to the first measured distance value (D). In this way, the mask control unit 143 may change the current mask MK using the previous measurement results of the distance to the workpiece 50, that is, it may change the mask shape, that is, it may change the mask pixels 130m. As a result, the distance measuring device 100 can set a mask MK that more closely conforms to the shape of the light-receiving spot SP, which is a collection of detection light-receiving pixels that receive detection light from the workpiece 50, and can further suppress the occurrence of abnormal distance values, thereby further improving the accuracy of distance measurement to the workpiece 50.

[0080] The distance measuring device 100 may repeat the mask setting MK and mask processing SM not only twice, but three or more times. In this case, the mask generation unit 142 may determine the mask shape for the Nth time (where N is an integer of 2 or more) according to the (N-1)th measured distance value. In this case, the mask generation unit 142 may gradually limit the distance measurement range by gradually increasing the size of the mask during multiple mask settings. In this case, the distance measuring device 100 can reduce the amount of calculation required to calculate the measured distance value and reduce power consumption. The distance measuring device 100 may also specify the distance measurement range (or the measurement range of the light emission time corresponding to the distance) via an input device and perform the mask setting MK and mask processing limited to the specified measurement range.

[0081] Figure 8 shows a second example of multiple mask settings and mask processing SM. In Figure 8, similar to Figure 5, it is illustrated that the workpiece 50 is positioned relative to the distance measuring device 100 so that it receives the receiving light RL at a time of Y2.5 seconds from the start of emission of the emitted light EL.

[0082] More specifically, there are, for example, six mask switching periods (or mask switching timings / light reception timings) in Figure 8. Mask MKa is set at the first mask switching timing (0 seconds), and this mask MKa remains set during the first mask switching period (0 seconds to Y1 second). As soon as the first timing ends, at the second timing (Y1 second), the mask switches from MKa to Mkb and is set to MKb. During the second mask switching period (Y1 second to Y2 second), the mask remains set to MKb. Similarly, as soon as the second timing ends, at the third timing (Y2 second), the mask switches from MKb to Mkc. During the third mask switching period (Y2 second to Y3 second), the mask remains set to MKc. During the fourth mask switching period (Y3 second to Y4 second), the mask remains set to MKd. During the fifth mask switching period (Y4 second to Y5 second), the mask remains set to MKe. During the sixth mask switching period (Y5 second to Y6 second), the mask remains set to MKf. In this way, each mask switches sequentially at each timing, and the mask remains set during each mask switching period. Note that in Figure 8, some details are omitted compared to Figure 5, and two consecutive mask switching periods (for example, the first and second mask switching periods, the third and fourth mask switching periods, and the fifth and sixth mask switching periods) are shown together as a single mask switching period, with masks MKa, MKc, and MKe being used as examples. Note that Y6 seconds corresponds to 0 seconds in the next cycle.

[0083] In Figure 8, the light source EL is emitted once and the light source RL is received once, and different masks MK are set at different timings for each received light source RL. In other words, multiple different mask processes SM (also called composite mask processes) are performed for each received light source RL.

[0084] The distance measuring device 100 emits one flash of light EL and receives one flash of detected light RL. At this time, the mask generation unit 142 sets the first mask MK (e.g., mask MKc) according to the elapsed time of light emission, and the mask control unit 143 controls the execution of mask process SM1 or mask process SM2 as the first mask process SM. In other words, the mask control unit 143 instructs the light receiving unit 130 to physically place a light-shielding member in front of the mask pixel 130m. As a result, the light-shielding member blocks the light (received light RL) that is about to enter the mask pixel 130m. Alternatively, the mask control unit 143 instructs the light receiving unit 130 not to generate a mask pixel signal for the received light RL received by the mask pixel 130m by mask MKc.

[0085] Next, the distance measuring unit 150 calculates the distance value of each pixel based on the light received signal of each pixel of the light receiving element 131, taking into account the results of mask processing SM1 or mask processing SM2. The distance measuring unit 150 calculates the measured distance value (D) based on the distance value of each pixel, for example by averaging the distance values. Here, since mask processing SM1 or mask processing SM2 is taken into account, a masked pixel signal is not generated. In other words, the distance measuring unit 150 calculates the measured distance value (D) based on the distance value of each unmasked pixel.

[0086] Next, the mask generation unit 142 calculates the time from the start of light emission of the emitted light EL to the received light RL (also referred to as the light reception measurement time) (e.g., Y 2.5 seconds) based on the measured distance value (D) and the speed of light. The mask generation unit 142 sets the second mask MK (e.g., mask MKd) according to the light reception measurement time, and the mask control unit 143 controls the execution of mask processing SM3 or mask processing SM4 as the second mask processing SM. In other words, the mask control unit 143 does not send the pixel signal of the mask pixel to the distance measurement unit 150. Alternatively, the mask control unit 143 does not allow the distance value of the mask pixel generated by the distance measurement unit 150 to be used in the derivation of the measured distance value. The second mask MK is basically a larger mask MK than the first mask MK.

[0087] Next, the distance measuring unit 150 calculates the distance value for each pixel based on the pixel signal of each pixel of the light-receiving element 131, taking into account the results of the mask processing SM3 or mask processing SM4. The distance measuring unit 150 calculates the measured distance value (D') based on the distance value of each pixel, for example by averaging the distance values. Here, since the mask processing SM3 or mask processing SM4 is taken into account, either a distance value for the masked pixel is not generated, or even if a distance value for the masked pixel is generated, it is not used in the measured distance value (D'). In other words, the distance measuring unit 150 calculates the measured distance value (D') based on the distance value of each unmasked pixel.

[0088] Furthermore, the distance measuring device 100 may emit light EL multiple times and receive light RL multiple times, similar to the first example shown in Figure 7. In this case, the mask control unit 143 may set multiple different masks MK and perform multiple different masking processes when receiving light RL each time, as described above. Also, the masks MK from the second emission and reception onward may be determined based on the first mask for that reception, which was determined by the measured distance value (D') from the previous reception.

[0089] Figure 9 shows a third example of multiple mask settings and mask processing SM.

[0090] More specifically, there are, for example, six mask switching periods (or mask switching timings / light reception timings) in Figure 9. Mask MKa is set at the first mask switching timing (0 seconds), and this mask MKa remains set during the first mask switching period (0 seconds to Y1 second). As soon as the first timing ends, at the second timing (Y1 second), the mask switches from MKa to Mkb and is set to MKb. During the second mask switching period (Y1 second to Y2 second), the mask remains set to MKb. Similarly, as soon as the second timing ends, at the third timing (Y2 second), the mask switches from MKb to Mkc. During the third mask switching period (Y2 second to Y3 second), the mask remains set to MKc. During the fourth mask switching period (Y3 second to Y4 second), the mask remains set to MKd. During the fifth mask switching period (Y4 second to Y5 second), the mask remains set to MKe. During the sixth mask switching period (Y5 second to Y6 second), the mask remains set to MKf. In this way, each mask switches sequentially at each timing, and the mask remains set during each mask switching period. Note that in Figure 9, some details are omitted compared to Figure 5, and two consecutive mask switching periods (for example, the first and second mask switching periods, the third and fourth mask switching periods, and the fifth and sixth mask switching periods) are shown together as a single mask switching period, with masks MKa, MKc, and MKe being used as examples. Note that Y6 seconds corresponds to 0 seconds in the next cycle.

[0091] The third example shown in Figure 9 is similar to the second example shown in Figure 8, but the timing of the second mask setting and mask processing SM is different. The timing of the second mask setting and mask processing SM may be immediately after the calculation of the first measured distance value (D) (see [A] in Figure 9), or it may be at a predetermined (e.g., fixed) timing in the light projection cycle (see [B] in Figure 9).

[0092] Thus, by performing a composite masking process as shown in Figure 8 or Figure 9, the distance measuring device 100 can improve the accuracy of the mask MK setting in a single light emission and reception cycle, enabling high-speed and high-precision measurement of the distance to the workpiece 50. In other words, the distance measuring device 100 can improve the accuracy of the measured distance value within one light emission cycle by different means (different masks MK and masking processes).

[0093] Figure 10 shows a fourth example of multiple mask settings and mask processing SM. In Figure 10, similar to Figure 5, it is illustrated that the workpiece 50 is positioned relative to the distance measuring device 100 so that it receives the receiving light RL at Y2.5 seconds from the start of the emission of the emitted light EL.

[0094] More specifically, there are, for example, six mask switching periods (or mask switching timings / light reception timings) in Figure 10. Mask MKa is set at the first mask switching timing (0 seconds), and this mask MKa remains set during the first mask switching period (0 seconds to Y1 second). As soon as the first timing ends, at the second timing (Y1 second), the mask switches from MKa to Mkb and is set to MKb. During the second mask switching period (Y1 second to Y2 second), the mask remains set to MKb. Similarly, as soon as the second timing ends, at the third timing (Y2 second), the mask switches from MKb to Mkc. During the third mask switching period (Y2 second to Y3 second), the mask remains set to MKc. During the fourth mask switching period (Y3 second to Y4 second), the mask remains set to MKd. During the fifth mask switching period (Y4 second to Y5 second), the mask remains set to MKe. During the sixth mask switching period (Y5 second to Y6 second), the mask remains set to MKf. In this way, each mask switches sequentially at each timing, and the mask remains set during each mask switching period. Note that in Figure 10, some details are omitted compared to Figure 5, and two consecutive mask switching periods (for example, the first and second mask switching periods, the third and fourth mask switching periods, and the fifth and sixth mask switching periods) are shown together as a single mask switching period, with masks MKa, MKc, and MKe being used as examples.

[0095] In Figure 10, the distance measuring device 100 emits a light source EL multiple times and receives a light source RL containing the detection light multiple times, similar to the first example shown in Figure 7. The light source EL is emitted, for example, according to a predetermined emission cycle. Also, similar to the second example shown in Figure 8, the distance measuring device 100 sets multiple different masks MK and performs multiple different mask processing SM when receiving the light source RL each time. In other words, the distance measuring device 100 performs composite mask processing. Note that for the second and subsequent light receptions, the mask setting and mask processing SM may be performed only once. In the fourth example of Figure 10, the explanation of the same process as in the second example of Figure 8 is omitted or simplified.

[0096] First, we assume that the workpiece 50 is a moving object and that its position changes according to the elapsed time of light emission. In this case, the distance between the distance measuring device 100 and the workpiece 50 will be different each time the received light RL from the workpiece 50 is received.

[0097] The distance measuring device 100 emits the first emitted light EL and receives the first received light RL. At this time, the mask control unit 143 sequentially switches masks according to the elapsed time of emitted light. In Figure 10, the first received light RL is received at the timing of mask MKc. The mask control unit 143 controls the device to execute either mask process SM1 or mask process SM2 as the first mask process SM for the first reception of light.

[0098] Next, the distance measuring unit 150 calculates the distance value of each pixel based on the light received signal of each pixel of the light receiving element 131, taking into account the results of the mask processing SM1 or mask processing SM2. Then, the distance measuring unit 150 calculates the measured distance value (D) based on the distance value of each pixel (in this case, each unmasked pixel).

[0099] Next, the mask control unit 143 calculates the reception measurement time of the first received light RL based on the measured distance value (D) and the speed of light. The mask control unit 143 sets the second mask MK (e.g., mask MKd) for the first reception according to the first reception measurement time and controls the execution of mask process SM3 or mask process SM4 as the mask process SM.

[0100] Next, the distance measuring unit 150 calculates a distance value for each pixel based on the light received signal for each pixel of the light receiving element 131, taking into account the results of the mask processing SM3 or mask processing SM4. Then, the distance measuring unit 150 calculates a measured distance value (D') based on the distance value of each pixel (in this case, each unmasked pixel).

[0101] Next, the distance measuring device 100 emits a second beam of light EL and receives a second beam of light RL. At this time, the mask control unit 143 sequentially switches masks according to the elapsed time of beam emission. In Figure 10, the second beam of light RL is received at the timing of mask MKe. In other words, the elapsed time from the start of beam emission is different for the second beam reception compared to the first beam reception timing. This is because the workpiece 50 is moving. Specifically, the workpiece 50 is moving away from the distance measuring device 100. The mask control unit 143 controls the device to execute either mask processing SM1 or mask processing SM2 as the mask processing.

[0102] Next, the distance measuring unit 150 calculates the distance value of each pixel based on the light received signal of each pixel of the light receiving element 131, taking into account the results of the mask processing SM1 or mask processing SM2. Then, the distance measuring unit 150 calculates the measured distance value (D) based on the distance value of each pixel (in this case, each unmasked pixel).

[0103] Next, the mask control unit 143 calculates the reception measurement time for the second received light RL based on the measured distance value (D) and the speed of light. The mask control unit 143 sets the second mask MK (e.g., mask MKf) for the second reception according to the second reception measurement time and controls the execution of mask processing SM3 or mask processing SM4 as a masking process. Note that mask MKf is a larger mask MK than mask MKe and has fewer unmasked pixels.

[0104] Next, the distance measuring unit 150 calculates a distance value for each pixel based on the light received signal for each pixel of the light receiving element 131, taking into account the results of the mask processing SM3 or mask processing SM4. Then, the distance measuring unit 150 calculates a measured distance value (D') based on the distance value of each pixel (in this case, each unmasked pixel).

[0105] In this way, even when the workpiece 50 is moving, the distance measuring device 100 can change the mask shape according to the elapsed time of light emission, thereby setting a mask MK suitable for the light reception timing regardless of the position of the workpiece 50. Furthermore, by generating a second mask MK according to the first measured distance value (D) each time the received light RL is received, the device 100 can suppress the second received light RL from not being received by an unmasked pixel, suppress the distance value of the unmasked pixel from becoming an abnormal value, and further improve the accuracy of the measured distance value.

[0106] Figure 11 shows a fifth example of multiple mask settings and mask processing SM. In Figure 11, as in Figure 5, it is illustrated that the workpiece 50 is positioned relative to the distance measuring device 100 so that it receives the receiving light RL at Y2.5 seconds from the start of the emission of the emission light EL. In Figure 11, the explanation of the same processes as in Figure 10 is omitted or simplified.

[0107] More specifically, there are, for example, six mask switching periods (or mask switching timings / light reception timings) in Figure 11. Mask MKa is set at the first mask switching timing (0 seconds), and this mask MKa remains set during the first mask switching period (0 seconds to Y1 second). As soon as the first timing ends, at the second timing (Y1 second), the mask switches from MKa to Mkb and is set to MKb. During the second mask switching period (Y1 second to Y2 second), the mask remains set to MKb. Similarly, as soon as the second timing ends, at the third timing (Y2 second), the mask switches from MKb to Mkc. During the third mask switching period (Y2 second to Y3 second), the mask remains set to MKc. During the fourth mask switching period (Y3 second to Y4 second), the mask remains set to MKd. During the fifth mask switching period (Y4 second to Y5 second), the mask remains set to MKe. During the sixth mask switching period (Y5 second to Y6 second), the mask remains set to MKf. In this way, each mask switches sequentially at each timing, and the mask remains set during each mask switching period. Note that in Figure 11, some details are omitted compared to Figure 5, and two consecutive mask switching periods (for example, the first and second mask switching periods, the third and fourth mask switching periods, and the fifth and sixth mask switching periods) are shown together as a single mask switching period, with masks MKa, MKc, and MKe being used as examples. Note that Y6 seconds corresponds to 0 seconds in the next cycle.

[0108] In Figure 11, the distance measuring device 100 emits a light source EL multiple times and receives a light source RL containing the detection light multiple times, similar to Figure 10. The light source EL is emitted, for example, according to a predetermined emission period. Also, similar to Figure 10, the distance measuring device 100 sets multiple different masks MK and performs multiple different mask processing SM when receiving the light source RL each time. In other words, the distance measuring device 100 performs composite mask processing. Note that for the second and subsequent light receptions, the mask setting and mask processing SM may be performed only once.

[0109] In Figure 11, it is assumed that the workpiece 50 is not a moving object, but rather that its position does not change according to the time elapsed since the light was projected; in other words, the workpiece 50 is at a fixed point. In this case, the distance between the distance measuring device 100 and the workpiece 50 is the same at the time of receiving the light RL from the workpiece 50 each time.

[0110] First, the distance measuring device 100 performs mask setting and mask processing SM twice for the first emitted light EL and received light RL, as in Figure 10. That is, the distance measuring device 100 roughly sets the first mask MK according to the emitted light elapsed time and performs mask processing SM1 or SM2, and then sets the second mask MK in detail according to the first measured distance value (D) and performs mask processing SM3 or SM4.

[0111] Next, unlike in Figure 10, the distance measuring device 100 performs mask setting and mask processing only once for the second emitted light EL and received light RL, instead of twice. Specifically, since the workpiece 50 is at a fixed point, the distance measuring device 100 has already determined the accurate distance to the workpiece 50 through two mask setting and mask processing SM during the first emission and reception of light. Therefore, from the first mask processing during the second reception of light, a mask MK (e.g., mask MKd) is set according to the first measured distance value (D) during the first reception of light, that is, the same mask MK as the second mask MK during the first reception of light is set, and mask processing SM1 or SM2 is performed.

[0112] Thus, when the workpiece 50 is at a fixed point, the distance measuring device 100 can perform distance measurement from the first mask setting, which has a mask shape that precisely matches the shape of the received light RL from the workpiece 50 (i.e., the receiving spot SP), for the second and subsequent light emission and reception. Therefore, the distance measuring device 100 can perform distance measurement to the workpiece 50 at high speed and with high accuracy.

[0113] Next, we will explain the mask MK that takes ambient light into account.

[0114] If there is light other than the reflected light (also called ambient light) reflected by the workpiece 50 from the projected light EL, the ambient light will also affect the derivation of the distance value. As a result, the accuracy of the derivation of the distance value of the pixel that receives ambient light (ambient light-receiving pixel) among the multiple pixels of the light-receiving element 131 will decrease. Ambient light may include, for example, lighting present in the measurement environment, or projected and reflected light from other light devices.

[0115] The light-receiving unit 130 keeps each pixel of the light-receiving element 131 in a state where it can receive light (for example, by turning on the power of the pixel) when the light-emitting unit 110 is not emitting light, and determines the light-receiving status of each pixel. The light-receiving unit 130 determines that the light received when the light-emitting unit 110 is not emitting light is ambient light. The light-receiving unit 130 may perform such ambient light reception determination, for example, when the distance measuring device 100 is started up or when a predetermined switch (for example, a switch for performing ambient light determination) is pressed. The light-receiving unit 130 stores information of the ambient light-receiving pixels that have received ambient light in memory.

[0116] The mask generation unit 142 may generate a mask MK that includes ambient light receiving pixels in the mask pixels 130m. This mask MK information is stored in memory. The mask generation unit 142 may generate a mask MKe that takes ambient light into account for each of the various shapes of mask MK (e.g., mask MKa to mask MKf). The mask generation unit 142 may also generate both a mask MK that takes ambient light into account and a mask MK that does not take ambient light into account for each of the various shapes of mask MK. By setting the generated mask MK that takes ambient light into account, the mask control unit 143 can exclude the effect of ambient light and derive the measurement distance value with high accuracy.

[0117] Furthermore, while the example given for the mask MK that takes ambient light into account is to define the shape of the mask MK so that ambient light receiving pixels are included in the mask pixels 130m, this is not limited to this. The mask MK may also be generated by excluding the detection light receiving pixels, which receive detection light in response to the emission of the emission light EL, from the mask pixels 130m. By setting the mask MK that takes into account the generated ambient light and detection light, the mask control unit 143 can receive detection light while suppressing the effect of ambient light, and can derive the measurement distance value with even greater accuracy. In other words, the number of pixels that receive detection light (effective pixels) can be maximized.

[0118] Furthermore, a detection light receiving pixel is a pixel whose signal level of the received light RL does not become 0 when ambient light obtained when no light is being emitted is removed from the received light RL. This is because, when detection light is being received, the detection light should remain after removing ambient light from the received light RL.

[0119] Furthermore, the mask control unit 143 may use coefficients or the like to reduce the influence of the distance value of the ambient light receiving pixel and the detection light receiving pixel on the measurement of the distance to the workpiece 50. For example, the mask control unit 143 may reduce the influence of the pixel by weighting the distance value of the pixel with a coefficient less than 1, such as a weighted average. Alternatively, the mask control unit 143 may control the system to reduce the signal level of the received light signals from the ambient light receiving pixel and the detection light receiving pixel obtained by the light receiving unit 130, or it may control the system to reduce the distance values ​​of the ambient light receiving pixel and the detection light receiving pixel obtained by the distance measuring unit 150. In this way, the mask control unit 143 can suppress the influence of the received light signals from the ambient light receiving pixel and the detection light receiving pixel on the measured distance value.

[0120] Next, we will explain the manual adjustment of the mask MK.

[0121] The mask generation unit 142 may manually generate the mask MK based on input information received from the user via an input device (e.g., keyboard, mouse, buttons, keys, microphone). In this case, the mask generation unit 142 may manually fine-tune the mask MK held in memory, or it may manually generate the mask MK from the beginning so that the mask pixels do not include the light-receiving spot SP obtained by the test workpiece 50T. In this case, the display control unit 155 may display information on the light-receiving spot SP using the test workpiece 50T, information on the detection light-receiving pixels (i.e., light-receiving spot SP) obtained as a past (e.g., previous) measurement result, the mask pixels of the generated mask MK, and information on the mask MK used in a past (e.g., previous) distance measurement on the display device of the distance measuring device 100, etc. The user may check the display on the display device to recognize the positions of the detection light-receiving pixels and mask pixels in the light-receiving element 131, and specify, for example, an arbitrary mask shape for the current measurement via the input device. As a result, the mask generation unit 142 may manually generate the mask MK via the input device. In this case, the mask generation unit 142 may manually generate multiple different masks MK according to the light emission time.

[0122] As a result, the distance measuring device 100 can be manually adjusted via an input device if, for example, the mask MK prepared in advance using a test workpiece 50T does not correspond favorably to the detection light receiving pixels using the actual workpiece 50.

[0123] Similarly, the mask generation unit 142 may manually generate a mask MK that takes into account ambient light receiving pixels, or a mask MK that takes into account ambient light receiving pixels and detection light receiving pixels, via an input device. In this case, the display control unit 155 may cause the distance measuring device 100 or an external display device to display the information of the above-mentioned mask MK.

[0124] Furthermore, the display control unit 155 may specify, for example, via an input device, which information from the displayable information should be displayed and which information should not be displayed. For example, the display control unit 155 may specify at least one of the information from the detected light receiving pixel information and the mask MK (i.e., the mask pixel 130m) information to be displayed on the display device and which information to not be displayed on the display device. It may also be possible to switch between displaying and not displaying on the display device. This allows the user to specify areas (e.g., pixels) that they wish to check and areas that they do not wish to check.

[0125] Thus, the distance measuring device 100 of this embodiment can track the change in shape of the mask pixel 130m, or mask MK, in real time according to the time elapsed since the start of pulse light emission (transmission time). Therefore, the distance measuring device 100 can suppress abnormal values ​​in the distance values ​​for each pixel corresponding to the received light signal for each pixel used to measure the distance to the workpiece 50, and can measure the distance to the workpiece with high accuracy. In addition, the distance measuring device 100 can improve the signal-to-noise ratio and reduce the processing load.

[0126] (modified version) Next, I will explain some variations.

[0127] Masking can be done mechanically or software-based. Mechanical masking involves preventing the emitted light EL from reaching the light receiving unit 130 (for example, preventing it from entering or blocking it). Software-based masking involves the light receiving unit 130 receiving the emitted light EL, but the mask control unit 143 sets a threshold for each pixel and prevents signals below that threshold (received light RL) from being used for distance measurement.

[0128] In the above embodiment, the masking process has mainly been described as mechanical masking, but software-based masking is also included. Software-based masking may include the mask control unit 143 setting a threshold for each pixel that takes into account the shape of the light-receiving spot SP of the light-receiving unit 130 for the received light RL, and preventing signals (received light RL) below the set threshold from being input to the distance measuring unit 150, or ignoring them as signals for distance calculation even if they are input to the distance measuring unit 150.

[0129] Furthermore, the "threshold set for each pixel" in this software-based masking process is the threshold at which light necessary to obtain the signal from the light-receiving spot SP, which is essential for distance measurement, is recognized as a received signal. The mask control unit 143 may set this threshold for all pixels, or it may set this threshold only for pixels other than those from which the signal from the light-receiving spot SP is to be obtained. In addition, the mask control unit 143 may perform a combined masking process (combined masking process) in which, after passing through the mask MK by mechanical masking, signals below the threshold are not used for distance measurement by further software-based masking.

[0130] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to these examples. It is clear to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of the present invention. Furthermore, the components in the above embodiments may be combined in any way without departing from the spirit of the invention.

[0131] <Summary of the embodiments of this disclosure> Based on the above, embodiments of this disclosure describe at least the following. Note that the components etc. in parentheses are examples of those corresponding to the embodiments described above, but are not limited to these.

[0132] (Item 1) A distance measuring device (distance measuring device 100) for measuring the distance to a workpiece (workpiece 50), A light-emitting unit (light-emitting unit 110) that emits pulsed light (electroluminescent light), A light receiving unit (light receiving unit 130) having multiple pixels, each of which receives detection light reflected from the workpiece and generates a light receiving signal, A mask determination unit (mask generation unit 142) determines a mask pixel (mask pixel 130m) from among the plurality of pixels of the light receiving unit according to the time elapsed since the start of pulse light emission, A mask control unit (mask control unit 143) performs a masking process (mask processing SM) that restricts the use of the light-receiving signal of the mask pixel for measuring the distance to the workpiece, A distance measuring unit (distance measuring unit 150) measures the distance to the workpiece based on the masking process and the light-receiving signal for each pixel, A distance measuring device equipped with the following features.

[0133] Depending on the time elapsed since the pulse light began to be emitted, different pixels receive the detection light in response to the pulse light. The shorter the distance from the distance measuring device, the shorter the time it takes for the light to travel back and forth, and the more pixels receive the detection light. The longer the distance from the distance measuring device, the longer the time it takes for the light to travel back and forth, and the fewer pixels receive the detection light. As a result, the distance measuring device can track the time elapsed since the pulse light began to be emitted by changing the mask pixels, i.e., the shape of the mask, in real time. Therefore, it is possible to suppress abnormal values ​​in the distance value corresponding to the received signal used to measure the distance to the workpiece, and to measure the distance to the workpiece with high accuracy.

[0134] (Item 2) The masking process includes placing a light-shielding member that blocks the detected light in front of the mask pixel, The distance measuring device described in item 1.

[0135] As a result, the distance measuring device can physically suppress the detection light from being received by the mask pixels. Therefore, no light reception signal is generated for the mask pixels, and it is not used to measure the distance to the workpiece.

[0136] (Item 3) The masking process includes not sending the light-receiving signal of the mask pixel to the distance measuring unit. A distance measuring device as described in item 1 or 2.

[0137] As a result, the distance measuring device does not send the received signal to the distance measuring unit even when it receives detection light on the mask pixel, thus preventing it from being used to measure the distance to the workpiece.

[0138] (Item 4) The distance measuring unit is Based on the light-receiving signal for each pixel, the distance value for each pixel is calculated. The distance to the workpiece is measured based on the distance value for each pixel. The masking process includes not calculating the distance value of the mask pixel based on the light-receiving signal of the mask pixel. A distance measuring device as described in any one of items 1 to 3.

[0139] As a result, the distance measuring device generates a light-receiving signal for the mask pixel, but does not calculate a distance value from the light-receiving signal. Therefore, it is possible to prevent the device from being used to measure the distance to the workpiece based on this distance value.

[0140] (Item 5) The distance measuring unit is Based on the light-receiving signal for each pixel, the distance value for each pixel is calculated. The distance to the workpiece is measured based on the distance value for each pixel. The masking process includes excluding the distance value of the mask pixel from the distance value used to measure the distance to the workpiece. A distance measuring device as described in any one of items 1 to 4.

[0141] As a result, even if the distance measuring device calculates the distance value of the mask pixels, it excludes this distance value from the distance value used to measure the distance to the workpiece, thus preventing its use in measuring the distance to the workpiece.

[0142] (Item 6) The mask determination unit determines the mask pixels multiple times, The mask control unit performs the masking process multiple times. The distance measuring unit performs the measurement of the distance to the workpiece based on the masking process multiple times. The mask determination unit determines the current mask pixels by changing the previous mask pixels based on the results of the previous measurement of the distance to the workpiece. A distance measuring device as described in any one of items 1 through 5.

[0143] As a result, the distance measuring device limits the area of ​​unmasked pixels (excluding masked pixels from the second measurement onward) to pixels that receive detection light from the workpiece. This further suppresses the occurrence of abnormal distance values ​​for unmasked pixels and improves the accuracy of distance measurement to the workpiece.

[0144] (Item 7) The mask control unit repeats the process of changing the mask pixels and executing the masking process. Distance measuring device as described in item 6.

[0145] As a result, the distance measuring device can suppress the occurrence of abnormal distance values ​​for unmasked pixels as it repeats the process of changing the mask pixels and performing the masking process, thereby improving the accuracy of distance measurement to the workpiece.

[0146] (Item 8) The mask determination unit specifies a time range for determining the mask pixels from the time from the start of pulse light projection. Distance measuring device as described in item 6 or 7.

[0147] This allows the distance measuring device to perform limited masking by specifying a time range (i.e., distance range) for determining the mask pixels. Therefore, the distance measuring device can limit the masking process and improve the processing speed related to measuring the distance to the workpiece.

[0148] (Item 9) The light-emitting unit emits the pulsed light once, The light receiving unit receives the detection light once, The distance measuring unit is Based on the light-receiving signal for each pixel, the distance value for each pixel is calculated. The distance to the workpiece is measured based on the distance value for each pixel. The previous masking process included placing a light-shielding member that blocks the detected light in front of the light-receiving unit, or not sending the light-receiving signal of the mask pixel to the distance measuring unit. The masking process described above includes not calculating the distance value of the mask pixel based on the light-receiving signal of the mask pixel, or excluding the distance value of the mask pixel from the distance value used to measure the distance to the workpiece. A distance measuring device as described in any one of items 6 through 8.

[0149] This allows the distance measuring device to perform multiple determinations and masking processes for different mask pixels in response to a single light reception, enabling high-speed and high-precision deduction of the distance to the workpiece.

[0150] (Item 10) The mask determination unit includes, among the plurality of pixels, the ambient light receiving pixels, which are pixels that received light when the pulsed light was not being emitted, in the mask pixels. A distance measuring device as described in any one of items 1 through 9.

[0151] This prevents the distance measuring device from using the received signal from an ambient light receiving pixel, which receives light other than the detected light (ambient light), to measure the distance to the workpiece. In other words, the distance measuring device can prevent a decrease in the accuracy of measuring the distance to the workpiece due to ambient light.

[0152] (Item 11) The mask determination unit excludes from the mask pixels the detection light receiving pixels that received the detection light when the pulse light was emitted, among the ambient light receiving pixels. Distance measuring device as described in item 10.

[0153] This allows the distance measuring device to prioritize using the received signal of the detected light for measuring the distance to the workpiece, for pixels that receive both ambient light and detected light.

[0154] (Item 12) The mask control unit reduces the influence on the measurement of the distance to the workpiece, which is determined by the distance value of the detection light receiving pixel based on the received signal of the detection light receiving pixel that received the detection light when the pulsed light was emitted, among the ambient light receiving pixels. Distance measuring device as described in item 10.

[0155] In ambient light receiving pixels, the detection light receiving pixels receive both detection light and ambient light. Compared to receiving only detection light, this can result in a lower signal-to-noise ratio and potentially worsen the accuracy of the distance measurement. In contrast, distance measuring devices can be adjusted to minimize the influence of the distance value of the detection light receiving pixels among the ambient light receiving pixels. This allows detection light to be used to measure the distance to the workpiece while suppressing the influence of ambient light.

[0156] (Item 13) It further includes a display control unit (display control unit 155) that controls the display of information, The light-emitting unit emits the pulsed light multiple times, The light receiving unit receives the detected light multiple times, The mask determination unit determines the mask pixels multiple times, The display control unit, The display device displays at least one of the information of the detection light receiving pixel that received the previous detection light and the information of the previous mask pixel. The mask determination unit receives information about the mask pixels input via the input device and determines the mask pixels to be used when receiving the detection light in the current instance. A distance measuring device as described in any one of items 1 through 12.

[0157] This allows the user to manually determine the mask pixels with high precision by checking the detection light receiving pixels and mask pixels from the previous detection light reception, and judging the accuracy of the range of the actual detection light receiving pixels relative to the mask pixels.

[0158] (Item 14) The display control unit specifies at least one of the information from the detected light receiving pixel information and the mask pixel information to be displayed on the display device and the information not to be displayed on the display device. Distance measuring device as described in item 13.

[0159] This allows the distance specification device to, for example, specify which information the user wishes to see from among the information about displayable pixels, and which information the user does not wish to see is not displayed. Therefore, the distance specification device can display the information necessary for the user in an easy-to-view manner. [Industrial applicability]

[0160] This disclosure is useful for distance measuring devices and the like that can determine mask pixels in real time according to the time elapsed since the start of pulsed light emission, thereby improving the accuracy of distance measurement to the workpiece. [Explanation of Symbols]

[0161] 50 Work 100 Distance measuring device 110 Light-emitting unit 111 Floodlight Lens 112 light-emitting elements 113 Floodlight Circuit 120 Light-gathering section 121 Light-receiving lens 130 Light receiving part 131 Photodetector 132 Light receiving circuit 140 Control Unit 141 Timing generation unit 142 Mask generation unit 143 Mask Control Unit 150 Distance measuring unit 160 Output section MK, MKa, MKb, MKc, MKd, MKe, MKf Masks SP light receiving spot

Claims

1. A distance measuring device for measuring the distance to a workpiece, A light-emitting unit that emits pulsed light, A light receiving unit having multiple pixels, wherein each pixel receives detection light reflected from the workpiece and generates a light receiving signal, A mask determination unit determines a mask pixel among the plurality of pixels of the light receiving unit according to the time elapsed since the start of pulse light emission, A mask control unit that performs mask processing to restrict the use of the light-receiving signal of the mask pixel for measuring the distance to the workpiece, A distance measuring unit measures the distance to the workpiece based on the masking process and the light-receiving signal for each pixel, A distance measuring device equipped with the following features.

2. The masking process includes placing a light-shielding member that blocks the detected light in front of the mask pixel, The distance measuring device according to claim 1.

3. The masking process includes not sending the light-receiving signal of the mask pixel to the distance measuring unit. The distance measuring device according to claim 1.

4. The distance measuring unit is Based on the light-receiving signal for each pixel, the distance value for each pixel is calculated. The distance to the workpiece is measured based on the distance value for each pixel. The masking process includes not calculating the distance value of the mask pixel based on the light-receiving signal of the mask pixel. The distance measuring device according to claim 1.

5. The distance measuring unit is Based on the light-receiving signal for each pixel, the distance value for each pixel is calculated. The distance to the workpiece is measured based on the distance value for each pixel. The masking process includes excluding the distance value of the mask pixel from the distance value used to measure the distance to the workpiece. The distance measuring device according to claim 1.

6. The mask determination unit determines the mask pixels multiple times, The mask control unit performs the masking process multiple times. The distance measuring unit performs the measurement of the distance to the workpiece based on the masking process multiple times. The mask determination unit determines the current mask pixels by changing the previous mask pixels based on the results of the previous measurement of the distance to the workpiece. The distance measuring device according to claim 1.

7. The mask control unit repeats the process of changing the mask pixels and executing the masking process. The distance measuring device according to claim 6.

8. The mask determination unit specifies a time range for determining the mask pixels from the time from the start of pulse light projection. The distance measuring device according to claim 6 or 7.

9. The light-emitting unit emits the pulsed light once, The light receiving unit receives the detection light once, The distance measuring unit is Based on the light-receiving signal for each pixel, the distance value for each pixel is calculated. The distance to the workpiece is measured based on the distance value for each pixel. The previous masking process included placing a light-shielding member that blocks the detected light in front of the light-receiving unit, or not sending the light-receiving signal of the mask pixel to the distance measuring unit. The masking process described above includes not calculating the distance value of the mask pixel based on the light-receiving signal of the mask pixel, or excluding the distance value of the mask pixel from the distance value used to measure the distance to the workpiece. The distance measuring device according to claim 6 or 7.

10. The mask determination unit includes, among the plurality of pixels, the ambient light receiving pixels, which are pixels that received light when the pulsed light was not being emitted, in the mask pixels. The distance measuring device according to claim 1.

11. The mask determination unit excludes from the mask pixels the detection light receiving pixels that received the detection light when the pulse light was emitted, among the ambient light receiving pixels. The distance measuring device according to claim 10.

12. The mask control unit reduces the influence on the measurement of the distance to the workpiece, which is determined by the distance value of the detection light receiving pixel based on the received signal of the detection light receiving pixel that received the detection light when the pulsed light was emitted, among the ambient light receiving pixels. The distance measuring device according to claim 10.

13. It further comprises a display control unit that controls the display of information, The light-emitting unit emits the pulsed light multiple times, The light receiving unit receives the detected light multiple times, The mask determination unit determines the mask pixels multiple times, The display control unit, The display device displays at least one of the information of the detection light receiving pixel that received the previous detection light and the information of the previous mask pixel. The mask determination unit receives information about the mask pixels input via the input device and determines the mask pixels to be used when receiving the detection light in the current instance. The distance measuring device according to claim 1.

14. The display control unit specifies at least one of the information from the detected light receiving pixel information and the mask pixel information to be displayed on the display device and the information not to be displayed on the display device. The distance measuring device according to claim 13.

Images