Distance measurement methods and distance measuring devices

Abstract

Distance measurement method in which a light source configured to emit pulsed light with respect to an object and a distance sensor are used, wherein the distance sensor includes a charge-generating surface in which charges are generated according to the incident reflected light of the pulsed light reflected from the object, and a charge-accumulating surface in which the charges generated in the charge-generating surface are accumulated, wherein the distance measurement method comprises: Transferring the charges generated in the charge-generating surface to the charge-accumulating surface during a first period with respect to an emission period of the pulsed light, in order to accumulate the charges in the charge-accumulating surface during the first period; Transferring the charges generated in the charge-generating surface to the charge-accumulating surface during a second period, which differs in timing from the first period and is similar in width to the first period, in order to accumulate the charges in the charge-accumulating surface during the second period; Arithmetizing a distance to an object based on the amount of charge accumulated in the charge-accumulating area during the first period and the amount of charge accumulated in the charge-accumulating area during the second period; and when emitting the pulsed light from the light source, the emission of the pulsed light, whose light intensity-stable period within the emission period of the pulsed light is preset to be longer than each of the first and second periods, from the light source, wherein the pulsed light is emitted after a start time of the first period when the pulsed light is emitted from the light source, and wherein a delay time of the emission timing of the pulsed light with respect to the start time of the first period is preset to a time that corresponds to a minimum value of a linearity surface of a distance measurement profile, which indicates a correlation between an actual distance and a distance determined by the distance sensor.

Description

Technical area

[0001] The present invention relates to a distance measuring method and a distance measuring device. background

[0002] Known distance measuring devices include time-of-flight (TOF) type distance sensors (see, for example, JP 2005-235893). A distance measuring device disclosed in JP 2005-235893 includes a distance sensor provided with a light-receiving layer, a photogate electrode for transferring charges, and a floating diffusion layer for storing the charges. In this distance measuring device, charges generated in the light-receiving layer due to incident pulsed light are allowed to flow into the floating diffusion layer by imparting pulse signals to the photogate electrode. The flowing charges are accumulated in the floating diffusion layer as signal charges. The charges accumulated in the floating diffusion layer are read out as an output corresponding to the amount of accumulated charges. A distance to an object is calculated based on the output.

[0003] An optical rangefinder is known from DE 10 2010 063 579 A1.

[0004] A rangefinder is known from JP 2012 - 215 480 A.

[0005] From DE 197 04 496 A1 a method and a device for determining the phase and / or amplitude information of an electromagnetic wave is known. Summary of the inventionTechnical problem

[0006] In a distance measuring device such as the one disclosed in the above-mentioned JP 2005-235893, even if a drive signal of a light source has a rectangular waveform, a light intensity signal of pulsed light emitted from the light source will have a trapezoidal waveform including a rising period, a light intensity stable period, and a falling period. During the rising period, the light intensity gradually increases and reaches a predetermined value. During the light intensity stable period, the light intensity remains at the predetermined value or greater. During the falling period, the light intensity drops below the predetermined value and gradually decreases. The present inventors have intensively investigated this and found that such a trapezoidal wave of the light intensity signal of the pulsed light may degrade the distance measuring accuracy of the distance measuring device.

[0007] Therefore, there is a need for improvements in distance measurement accuracy in this technical field. Problem solving

[0008] A distance measuring method according to one aspect of the present invention is a distance measuring method in which a light source configured to emit pulsed light with respect to an object and a distance sensor are used, wherein the distance sensor includes a charge generation area in which charges are generated according to incident reflection light of the pulsed light reflected from the object, and a charge accumulation area in which the charges generated in the charge generation area are accumulated, the distance measuring method including: transferring the charges generated in the charge generation area to the charge accumulation area during a first period with respect to an emission period of the pulsed light, so as to accumulate the charges in the charge accumulation area during the first period;Transferring the charges generated in the charge-generating area to the charge-accumulating area during a second period that is different in timing from the first period and similar in width to the first period, thereby accumulating the charges in the charge-accumulating area during the second period; Arithmetizing a distance to an object based on an amount of charges accumulated in the charge-accumulating area during the first period and an amount of charges accumulated in the charge-accumulating area during the second period;and when emitting the pulsed light from the light source, emitting the pulsed light, whose light intensity stable period within the emission period of the pulsed light is preset to be longer than each of the first and second periods, from the light source, wherein the pulsed light is emitted after a start time of the first period when the pulsed light is emitted from the light source, and wherein a delay time of the emission timing of the pulsed light with respect to the start time of the first period is preset to a time corresponding to a minimum value of a linearity surface of a distance measurement profile indicating a correlation between an actual distance and a distance detected by the distance sensor;

[0009] A distance measuring device according to one aspect of the present invention is a distance measuring device that includes a light source configured to emit pulsed light with respect to an object, and a distance sensor configured to include a charge generating area in which charges are generated according to incident reflected light of the pulsed light reflected from the object, and a charge accumulating area in which the charges generated in the charge generating area are accumulated, wherein the distance measuring device includes: a charge transfer unit configured to transfer the charges generated in the charge generating area with respect to an emission period of the pulsed light during a first period to the charge accumulating area so as to accumulate the charges in the charge accumulating area during the first period, and configuredtransferring the charges generated in the charge-generating area to the charge-accumulating area during a second period, different from the first period in timing and similar to the first period in width, so as to accumulate the charges in the charge-accumulating area during the second period; a distance arithmetic element configured to arithmetic a distance to the object based on an amount of charges accumulated in the charge-accumulating area during the first period and an amount of charges accumulated in the charge-accumulating area during the second period; and a light source driving element configured to drive the light source to emit the pulsed light, whose light intensity stable period within the emission period of the pulsed light is preset to be longer than each of the first and second periods, from the light source,wherein the pulse light is emitted after a start time of the first period when the pulse light is emitted from the light source, and wherein a delay time of the emission timing of the pulse light with respect to the start time of the first period is set in advance to a time corresponding to a minimum value of a linearity surface of a distance measurement profile indicating a correlation between an actual distance and a distance detected by the distance sensor.

[0010] In such inventions, pulsed light is emitted from the light source, and the reflected light from the object enters the distance sensor. Charges are generated in the charge-generating area of ​​the distance sensor according to the incident and reflected light. The charges generated in the charge-generating area are transferred to the charge-accumulating area during the first and second periods to be accumulated in the charge-accumulating area. The first and second periods differ in timing and are of similar width. The distance to the object is determined based on the amount of charge accumulated during the first and second periods.

[0011] In a case where the light intensity signal of the pulsed light emitted from the light source has a trapezoidal waveform including a rising period and a falling period, as mentioned above, compared to a case where the light intensity signal has a rectangular waveform, the amount of charge generated in the charge generating area decreases in the rising period and increases in the falling period. Similarly, for example, in a case where the first period overlaps with the rising period and the second period overlaps with the falling period, the amount of charge accumulated in the charge accumulating area decreases during the first period compared to the case of the rectangular wave, and the amount of charge accumulated in the charge accumulating area increases during the second period compared to the case of the rectangular wave.In this way, the amounts of charge used to determine the distance to the object may change due to the influence of the rising and falling periods. As a result, the distance measurement accuracy may be affected.

[0012] Here, with respect to the pulsed light emitted from the light source, the light intensity stable period within the pulsed light emission period is set in advance to be longer than both the first and second periods. Accordingly, with respect to the amount of charge accumulated in the charge accumulating area in each of the first and second periods, a percentage of the amount of charge accumulated in accordance with the light intensity stable period increases, and the percentage of the amount of charge accumulated in accordance with the rising period and falling period decreases. Therefore, it is possible to reduce the influences of the rising period and falling period on the distance measurement accuracy. As a result, the distance measurement accuracy can be improved.

[0013] When pulsed light is emitted from the light source, the pulsed light can be emitted after the start time of the first period. In this case, the percentage of the amount of charge accumulated in the charge-accumulating area during the second period increases more than the amount of charge accumulated during the light intensity-stable period of the pulsed light. As a result, the distance measurement accuracy can be improved, especially for short distances.

[0014] A delay time of the pulsed light emission timing relative to the start time of the first period can be set in advance to a time corresponding to a minimum value of a linearity range of a distance measurement profile, which indicates a correlation between an actual distance and a distance detected by the distance sensor. In such a case, it is possible to measure under a condition that a zero distance is shifted to a distance at the minimum value. Therefore, even with respect to a distance range below the minimum value, distance measurement accuracy can be improved.

[0015] The distance sensor may include a plurality of charge-accumulating areas and a plurality of transfer electrodes configured to transfer the charges generated in the charge-generating area to the plurality of charge-accumulating areas. Transfer signals with mutually different phases may be applied to the plurality of charge electrodes. In such a case, each time the pulse light is emitted once, the generated charges are accumulated in other charge-accumulating areas in such a way that the distance to the object can be determined. Therefore, it is possible to prevent deterioration in distance measurement accuracy due to time variation in the distance to the object.

[0016] The distance sensor may include a transfer electrode configured to transfer the charges generated in the charge-generating area to the charge-accumulating area, and the transfer electrode may be provided with a transfer signal with a phase shifted intermittently at a predetermined timing. In such a case, distance measurement can be performed by at least one transfer electrode and one charge-accumulating area. Accordingly, it is possible to downsize the distance sensor. Advantageous invention effects

[0017] According to an embodiment of the present invention, it is possible to provide a distance measuring method and a distance measuring apparatus capable of improving distance measuring accuracy. Short description of drawings Fig. 1 is a configuration diagram of a distance measuring device according to the present embodiment. Fig. 2 is a cross-sectional view illustrating a configuration of a distance image sensor. Fig. 3 is a schematic plan view of the distance image sensor. Fig. 4 is a view illustrating a configuration of the distance sensor. Fig. Figure 5 is a cross-sectional view of the configuration along the line VV in Fig. 4. Fig. Fig. 6 is a view showing potential profiles in the vicinity of a second main surface of a semiconductor substrate along the line VV in Fig. 4 illustrated. Fig. 7 is a view illustrating deterioration of distance measurement accuracy in the distance measurement method according to a comparative example. Fig. 8 is a distance measurement profile illustrating a correlation between an actual distance and a distance determined by the distance measurement method according to the comparative example. Fig. 9 is an example of a timing chart of various signals in a distance measuring method according to the present embodiment. Fig. 10 is another example of a timing chart of the various signals in the distance measuring method according to the present embodiment. Fig. 11 is a flowchart illustrating a method of setting a light intensity stable period and a delayed irradiation time. Fig. 12 is an example of the distance measurement profile. Fig. 13 is a view illustrating a configuration of a distance sensor according to a modification. Fig. 14 is a timing diagram of various signals in a distance measuring method according to the modification. Description of embodiments

[0018] An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that elements with common elements and features are denoted by the same reference numerals, and redundant explanations are omitted here.

[0019] Fig. 1 is a configuration diagram of a distance measuring device according to the embodiment.

[0020] A distance measuring device 10 measures a distance d to an object OJ. The distance measuring device 10 includes a distance image sensor RS, a light source LS, a display DSP, and a control unit. The control unit includes a drive element (light source drive element) DRV, a control element CONT, and an arithmetic element (distance arithmetic element) ART. The light source LS emits pulsed light Lp with respect to the object OJ. The light source LS includes, for example, a laser irradiation device and an LED. The distance image sensor RS is a charge distribution type distance image sensor. The distance image sensor RS is mounted on a wiring board WB.

[0021] The control unit (drive element DRV, control element CONT, and arithmetic element ART) includes an arithmetic circuit such as a central processing unit (CPU), a memory such as random access memory (RAM) and read-only memory (ROM), a power supply circuit, and hardware such as a readout circuit including an A / D converter. This control unit may partially or entirely comprise an integrated circuit such as an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA).

[0022] The drive element DRV applies a drive signal S Dto the light source LS in accordance with a control of the control element CONT and drives the light source LS in such a manner that the pulse light Lp is emitted toward the object OJ. The control element CONT not only controls the drive element DRV but also outputs first and second transfer signals S1 and S2 to the distance sensor RS. The control element CONT controls the display DSP to display arithmetic results of the arithmetic element ART. The arithmetic element ART reads each amount of charges Q1, Q2 from the distance image sensor RS. The arithmetic element ART arithmetically calculates the distance D based on the read amounts of charges Q1, Q2 and outputs the arithmetic results to the control element CONT. An arithmetic method for the distance D will be described later with reference to Fig. 7. The arithmetic results of the arithmetic element ART are input to the display from the control element CONT. The display DSP shows the arithmetic signals.

[0023] In the distance measuring device 10, the drive signal S D applied to the light source LS in such a way that pulsed light Lp is emitted from the light source LS. When the pulsed light Lp emitted from the light source LS enters the object OJ, reflected pulsed light Lr is reflected by the object OJ and emitted therefrom. The reflected light Lr emitted by the object OJ enters the charge-generating surface of the distance image sensor RS.

[0024] The distance image sensor RS outputs the amounts of charges Q1, Q2 that are synchronized with the first and second transfer signals S1, S2 and collected per pixel. The output amounts of charges Q1, Q2 are applied to the arithmetic element ART in synchronization with the drive signal S DThe arithmetic element ART arithmeticates the distance D per pixel based on the input quantity of charges Q1, Q2, and the arithmetic results are input to the control element CONT. The arithmetic results input to the control element CONT are transmitted to and displayed on the display DSP.

[0025] Fig. 2 is a cross-sectional view of a configuration of the distance image sensor.

[0026] The distance image sensor RS is a front-illuminated distance image sensor. The distance image sensor RS includes a semiconductor substrate 1 and a light-intercepting layer LI. The semiconductor substrate 1 includes first and second main surfaces 1a, 1b opposite each other. The second main surface 1b is a light-incident surface. The distance image sensor RS is bonded to the wiring board WB by an adhesive surface FL, with the side of the first main surface 1a of the semiconductor substrate 1 facing the wiring board WB. The adhesive surface FL includes an insulating adhesive and a filler. The light-intercepting layer LI is arranged in front of the second main surface 1b of the semiconductor substrate 1. The reflected light LR enters the distance image sensor RS from the second main surface 1b of the semiconductor substrate 1.

[0027] Fig. Figure 3 is a schematic plan view of the distance image sensor. It should be noted that the light intercepting layer LI in Fig. 3 is omitted.

[0028] The semiconductor substrate 1 of the distance image sensor RS includes an image pickup surface 1A containing a plurality of distance sensors P(m, n) arranged in a two-dimensional manner. Each of the distance sensors P(m, n) outputs the above-mentioned two quantities of charges Q1, Q2. Accordingly, the reflected light LR reflected from the object OJ is formed in the image pickup surface 1A, and a distance image of the object OJ is obtained. One distance sensor P(m, n) functions as a pixel. It should be noted that two or more distance sensors P(m, n) can function as a pixel.

[0029] Fig. 4 is a view illustrating a configuration of the distance sensor. Fig. Figure 5 is a cross-sectional view of the configuration along the line VV in Fig. 4. It should be noted that the light intercepting layer LI in Fig. 4 is omitted.

[0030] As mentioned above, the distance image sensor RS includes the light intercepting layer LI in front of the second main surface 1b, which is the light incident surface. An aperture LIa is formed in an area corresponding to each of the distance sensors P(m, n) of the light intercepting layer LI. The aperture LIa is rectangular in shape. Here, the aperture LIa is formed into a rectangle. The light passes through the aperture LIa of the light intercepting layer LI and enters the semiconductor substrate 1. Accordingly, the aperture LIa defines a light-receiving area in the semiconductor substrate 1. The light intercepting layer LI includes a metal such as aluminum and the like.

[0031] The semiconductor substrate 1 includes a first semiconductor surface 3 of the p-type and a second semiconductor surface 5 of the p --type with a lower impurity concentration than the first semiconductor surface 3. The first semiconductor surface 3 is arranged on the side of the first main surface 1a. The second semiconductor surface 5 is arranged on the second main surface 1b. The semiconductor substrate 1 can be grown, for example, on a p-type semiconductor substrate, a p - -type epitaxial layer with a lower impurity concentration than that of the semiconductor substrate. An insulating layer 7 is formed on the second main surface 1b (second semiconductor surface 5) of the semiconductor substrate 1.

[0032] Each of the distance sensors p(m, n) is a charge distribution type distance sensor. Each of the distance sensors p(m, n) includes a photogate electrode PG, first and second charge accumulating areas FD1, FD2, and first and second transfer electrodes TX1, TX2. The photogate electrode PG is arranged corresponding to the aperture LIa. An area corresponding to the photogate electrode PG in the semiconductor substrate 1 (second semiconductor area 5) (a lower photogate electrode PG in Fig. 5) acts as a charge-generating surface, where charges are generated according to the incident reflected light LR of the pulsed light Lp reflected from the object OJ. The photogate electrode PG corresponds to the shape of the aperture LIa and is rectangular when viewed from above. Here, the photogate electrode PG is shaped like a rectangle, similar to the aperture LIa.

[0033] The first and second charge accumulating areas FD1, FD2 are arranged to sandwich the photogate electrode PG. The first and second charge accumulating areas FD1, FD2 are arranged separately from the photogate electrode PG. Each of the first and second charge accumulating areas FD1, FD2 is rectangular in shape when viewed from above. In the present embodiment, each of the first and second charge accumulating areas FD1, FD2 is square in shape when viewed from above and is similar to each other in shape. The first and second charge accumulating areas FD1, FD2 are n-type semiconductor areas with high impurity concentrations formed in the second semiconductor area 5. The first and second charge accumulating areas FD1, FD2 accumulate charges generated in the charge generating area as signal charges.

[0034] The first transfer electrode TX1 is arranged on the insulating layer 7 and between the first charge-accumulating area FD1 and the photo-gate electrode PG. The first transfer electrode TX1 is arranged separately from both the first charge-accumulating area FD1 and the photo-gate electrode PG. The first transfer electrode TX1 transfers the charges generated in the charge-generating area to the first charge-accumulating area FD1 during a first period T1 (see Fig. 7) in accordance with the first transfer signal S1 (see Fig. 7). The first period T1 corresponds to an emission period T T of the pulse light Lp (see Fig. 7).

[0035] The second transfer electrode TX2 is arranged on the insulating layer 7 and between the second charge-accumulating area FD2 and the photo-gate electrode PG. The second transfer electrode TX2 is arranged separately from both the second charge-accumulating area FD2 and the photo-gate electrode PG. The second transfer electrode TX2 transfers the charges generated in the charge-generating area to the second charge-accumulating area FD2 during a second period T2 (see Fig. 7), in accordance with the second transfer signal S2 (see Fig. 7 with a different phase than that of the first transfer signal S1. The second period T2 differs from the first period T1 in timing and is similar in width to the first period T1.

[0036] As mentioned above, the control element CONT outputs the first and second transfer signals S1, S2. The first and second transfer signals S1, S2 output by the control element CONT are applied to the first and second transfer electrodes TX1, TX2. Accordingly, the first and second transfer electrodes TX1, TX2 distribute the charges generated in the charge-generating area and transfer them to the first and second charge-accumulating areas FD1, FD2. Therefore, a part of the control element CONT and the first and second transfer electrodes TX1, TX2 function as a charge transfer unit.

[0037] Each of the first and second transfer electrodes TX1, TX2 is rectangular in shape when viewed from above. Here, each of the first and second transfer electrodes TX1, TX2 is formed in a rectangle and is similar in shape. The long sides of the first and second transfer electrodes TX1, TX2 are shorter than the long sides of the photogate electrode PG.

[0038] The insulating layer 7 is provided with contact holes for exposing the surface of the second semiconductor area 5. Conductors 13 for connecting the first and second charge-accumulating areas FD1, FD2 to their outer surfaces are arranged in the contact holes.

[0039] Here, the expression “concentration of foreign matter is high” represents that the concentration of foreign matter is, for example, equal to or greater than 1×10 17 cm -3and is indicated by a "+" attached to the conductivity type. On the other hand, an expression "impurity concentration is low" represents that the impurity concentration is equal to or less than 10×10 15 cm -3 high, and is indicated by a “-” attached to the conductivity type.

[0040] The thickness / impurity concentration of each semiconductor area is as follows: First semiconductor area 3: Thickness 10 to 1000 µm / Impurity concentration 1×10 12 up to 10 19 cm -3 ; second semiconductor surface 5: thickness 1 to 50 µm / impurity concentration 1×10 12 up to 10 15 cm -3 ; first and second charge accumulating surfaces FD1, FD2: thickness 0.1 to 1 µm / impurity concentration 1×10 18 up to 10 20 cm -3 .

[0041] A reference potential, such as a ground potential, is applied to the semiconductor substrate 1 (first and second semiconductor surfaces 3, 5) through a back gate or a through electrode, or the like. The semiconductor substrate 1 comprises Si, the insulating layer 7 comprises SiO2, and the photogate electrode PG and the first and second transfer electrodes TX1, TX2 comprise polysilicon. It should be noted that other materials may be included in these elements.

[0042] There is a 180-degree shift between the phase of the first transfer signal S1 applied to the first transfer electrode TX1 and the phase of the second transfer signal S2 applied to the second transfer electrode TX2. The light incident on each of the distance sensors P(m, n) is converted into charges in the semiconductor substrate 1 (second semiconductor surface 5). A portion of the charges thus generated is allowed to migrate as signal charges to the first transfer electrode TX1 or the second transfer electrode TX2 via potential gradients. The potential gradient is formed by the voltage applied to the photogate electrode PG and the first and second transfer electrodes TX1, TX2.

[0043] When a positive potential is applied to the first transfer electrode TX1 or the second transfer electrode TX2, a potential of a surface of the semiconductor substrate 1 (second semiconductor surface 5) under the first transfer electrode TX1 or the second transfer electrode TX2 becomes lower in terms of electrons than a potential of a surface of the semiconductor substrate 1 (second semiconductor surface 5) under the photogate electrode PG. Accordingly, negative charges (electrons) are attracted toward the first transfer electrode TX1 or the second transfer electrode TX2, and the negative charges are accumulated in potential wells formed by the first and second charge-accumulating surfaces FD1, FD2. Each of the n-type semiconductors contains a positively ionized donor and has the positive potential, attracting the electrons.When a potential lower than the positive potential (e.g., the ground potential) is applied to the first transfer electrode TX1 or the second transfer electrode TX2, a potential barrier is created by the first transfer electrode TX1 or the second transfer electrode TX2. Therefore, the charges generated in the semiconductor substrate 1 are not drawn into the first and second charge-accumulating areas FD1, FD2.

[0044] Fig. Fig. 6 is a view showing potential profiles in the vicinity of the second main surface of the semiconductor substrate along the line VV in Fig. 4 illustrated.

[0045] In Fig. 6 downward directions represent positive directions of potentials. Fig. 6 shows a potential φ TX1 an area just below the transfer electrode TX1, a potential φ TX1 an area just below the second transfer electrode TX2, a potential φ PGthe charge generating area just below the photo-gate electrode PG, a potential φ FD1 the first charge accumulating surface FD1 and a potential φ FD2 the second charge accumulating area FD2.

[0046] If the potentials (φ TX1 , φ TX2 ) of the areas under the adjacent first and second transfer electrodes TX1, TX2 without bias voltage are defined as reference potentials, the potential φ PG the area (charge-generating area) directly under the photogate electrode PG is set higher than the reference potentials. The potential φ PG the charge generating area is higher than the potentials φ TX1 , φ TX2 . Therefore, the potential profile is formed like a depression pointing downwards in the drawings in the charge generating area.

[0047] An accumulative operation of the charges is carried out with reference to Fig. 6. When the phase of the first transfer signal S1 applied to the transfer electrode TX1 is zero degrees, the positive potential is applied to the first transfer electrode TX1. The second transfer electrode TX2 is applied with a potential in the opposite phase, namely, a potential in a phase of 180 degrees (for example, the ground potential). The photogate electrode PG is applied with a potential between the potential applied to the first transfer electrode TX1 and the potential applied to the second transfer electrode TX2. In such a case, as shown in Fig. 6a, the potential φ TX of the semiconductor under the first transfer electrode TX1 below the potential φ PG of the charge-generating area. Therefore, the charges e generated in the charge-generating area are allowed to flow into the potential well of the first charge-accumulating area FD1.

[0048] On the other hand, the potential φTX2 of the semiconductor under the second transfer electrode TX2. Therefore, the charges do not flow into the potential well of the second charge-accumulating area FD2. Accordingly, the charges are collected and accumulated in the potential well of the first charge-accumulating area FD1. Since the first and second charge-accumulating areas FD1 and FD2 are doped with n-type impurities, their potentials are reset in the positive direction.

[0049] When the phase of the second transfer signal S2 applied to the second transfer electrode TX2 is zero degrees, the positive potential is applied to the second transfer electrode TX2. The first transfer electrode TX1 is applied with a potential in the opposite phase, that is, a potential in a phase of 180 degrees (for example, a ground potential). The photogate electrode PG is applied with a potential between the potential applied to the first transfer electrode TX1 and the potential applied to the second transfer electrode TX2. In such a case, as shown in Fig. 6, the potential φ TX2 of the semiconductor just below the second transfer electrode TX2 below the potential φ PG of the charge-generating area. Therefore, the negative charges e generated in the charge-generating area are allowed to flow into the potential well of the second charge-accumulating area FD2.

[0050] On the other hand, the potential φ TX1 of the semiconductor under the first transfer electrode TX1. Therefore, the charges do not fall into the potential well of the first charge-accumulating area FD1. Accordingly, the charges are collected and accumulated in the potential well of the second charge-accumulating area FD2.

[0051] In this way, the charges are collected and accumulated in the potential wells of the first and second charge-accumulating surfaces FD1 and FD2. The charges accumulated in the potential wells of the first and second charge-accumulating surfaces FD1, FD1 are read out from the outside of the surfaces.

[0052] Fig. Fig. 7 is a view illustrating deviation of distance measurement accuracy in a distance measurement method according to a comparative example. Specifically, Fig. 7(a) is a timing diagram of various signals in a case where a light intensity signal of pulsed light at a time when the pulsed light is emitted from the light source has an ideal rectangular waveform. Fig. Figure 7(b) is a timing diagram of different signals in an actual case. Fig. 7(c) is a view comparing a light intensity signal of reflected light when the light returns to an image pickup surface.

[0053] First, with reference to Fig. 7(a) describes a case where a light intensity signal S Lp of pulsed light Lp at a time when the pulsed light Lp is emitted from the light source LS has the ideal square wave waveform. Fig. 7(a) illustrates a drive signal S D , which is applied to the light source LS, through the control element CONT, the light intensity signal S Lpof the pulsed light Lp, when the pulsed light Lp is emitted from the light source LS, an intensity signal S Lr reflected light Lr when the reflected light Lr returns to an image pickup surface 1A, a first transfer signal S1 to be applied to the first transfer electrode TX1, and a second transfer signal S2 to be applied to the second transfer electrode TX2.

[0054] As in Fig. 7(a), the drive signal SD, the light intensity signal S Lp , S Lr and the first and second transfer signals S1, S2 are all pulse signals having the ideal square waveform. These signals are all configured to be at a low level in a state before the drive signal S D is applied to the light source LS.

[0055] The drive signal S D is a pulse signal of pulse width Tp. The pulse width Tp of the drive signal S Dis equivalent to a setting value of a pulse width of the light intensity signal S Lp In such a case, since the light intensity signal S Lp has the ideal square wave waveform, the pulse width of the light intensity signal S Lp equivalent to the pulse width Tp of the drive signal S D according to the setting. The drive signal S D is set to a low level after being set to a high level during the pulse width Tp. The light intensity signal S Lp increases simultaneously with a start time for applying the drive signal S D and the light intensity signal S Lp is set to a level corresponding to the light intensity of the pulsed light Lp. The light intensity signal S Lp falls after the pulse width Tp and is set to a low level.

[0056] In synchronization with the emission of the pulsed light Lp, the first and second transfer signals S1, S2 are applied to the first and second transfer electrodes TX1, TX2 in antiphase. Specifically, the first transfer signal S1 synchronizes with the light intensity signal S Lp by a phase difference of zero degrees and is applied to the first transfer electrode TX1 during the pulse width Tp so as to be set to a high level. The second transfer signal S2 is synchronized with the light intensity signal S Lpby a phase difference of 180 degrees and is applied to the second transfer electrode TX2 during the pulse width Tp so as to be set to a high level. Periods when the first and second transfer signals S1, S2 are set to a high level are the first and second periods T1, T2, respectively. The first and second periods T1, T2 differ in timing and are similar in width. In such a case, each width of the first and second periods T1, T2 is equivalent to the pulse width Tp of the drive signal S. D .

[0057] The light intensity signal S L r increases simultaneously with time as the reflected light Lr returns to the image pickup surface 1A, and the light intensity signal S Lr is set to a level corresponding to the light intensity of the reflected light S Lr The light intensity signal S Lrfalls, according to the pulse width Tp and is set to the low level. In such a case, the pulse width of the light intensity signal S Lr equivalent to the pulse width Tp of the drive signal SD. A phase difference Td between the light intensity signal S Lp and the light intensity signal S Lr is the time of flight of light. The phase difference Td corresponds to the distance d from the distance image sensor RS to the object OJ.

[0058] The charges generated in the charge generating area in accordance with the incident reflection light Lr are transferred to the first charge accumulating area FD1 during the first period T1 when the first transfer signal S1 is at high level with respect to an emission period T T of the pulsed light Lp is set so as to be accumulated in the first charge accumulating area FD1 during the first period T1. The emission period T Tof the pulsed light Lp is a period when the light intensity signal S Lp is not at the low level. In such a case, the width of the emission period T T equivalent to the pulse width Tp of the drive signal S D .

[0059] The charges generated in the charge generating area in accordance with the incident reflected light Lr are transferred to the second charge accumulating area FD2 during the second period T2 when the second transfer signal S2 is set to the high level so as to be accumulated in the second charge accumulating area FD2 during the second period T2.

[0060] The charges are generated in the charge-accumulating area during a period when the reflected light Lr enters the area. Therefore, an amount of charges Q1 accumulated in the first charge-accumulating area FD1 will be an amount of charges to be accumulated during a period within the first period T1 when the light intensity signal S Lr and the first transfer signal S1 overlap. Furthermore, an amount of charges Q2 accumulated in the second charge accumulating area FD2 will be an amount of charges to be accumulated during a period within the second period T2 when the light intensity signal S Lr and the second transfer signal S2 overlap.

[0061] The distance d is arithmetized by the following formula (1), based on the rate (distribution rate) of the quantity of charges Q1 and the quantity of charges Q2. It should be noted that c represents the speed of light. Distance d=(c / 2)×(Tp×Q2 / (Q1+Q2))

[0062] A measurable distance range d in such a case depends on the width of each of the first and second periods T1, T2, and the measurable distance is a distance in which the phase difference Td is set within the width of each of the first and second periods T1, T2. In other words, when the phase difference Td becomes equivalent to the width of each of the first and second periods T1, T2, the distance d becomes a maximum value of the measurable distance d. Therefore, a distance measurement range, which is a width of a distance range to be measured, can be set based on the width of each of the first and second periods T1, T2. It should be noted that "measurable" indicates that the distance d can be theoretically calculated by the above-mentioned formula (1).

[0063] With reference to Fig. 7(b) and Fig. 7(c), the actual case is described below. As in Fig. 7(b), the light intensity signal S Lp , S Lr Trapezoidal waveforms. Each of the light intensity signals S Lp , S Lr increases gradually and reaches a predetermined value during a rise period T R and remains at the predetermined value or greater during a light intensity stable period T S and then falls below the predetermined value and decreases gradually during a falling period T F In such a case, the emission period T T of the pulse light Lp longer than the pulse width Tp of the drive signal S D .

[0064] It should be noted that the light intensity stable period T S not only shows one period when the light intensity signals S Lp , S LR become constant, but also indicates a period when the light intensity signals S Lp, S Lrmaintained, for example, at or within 5% of the maximum value. In a case where the period when the light intensity signals S Lp , S Lr become constant, as the light intensity stable period T S is a period in which the rising period T R and falling period T F from the emission period T T of the pulse light Lp are subtracted, the light intensity stable period T S In such a case, the emission period T T of the pulse light Lp equivalent to a sum of the width of the falling period T F and the pulse width Tp of the drive signal S D .

[0065] As in Fig. 7(c), decreases in the actual case compared to a case where the light intensity signals S Lp , S Lrthe ideal square wave waveforms, the amount of charges Q1 by an amount of charges Q1 due to an influence of the increasing period T R . Furthermore, the amount of charges Q2 increases by an amount of charges Q2 due to an influence of the falling period T F . Thus, in the distance measurement method according to the comparative example, the distance measurement accuracy is impaired because the charge distribution ratio differs from the ideal case.

[0066] Fig. 8 is a distance measurement profile illustrating a correlation between an actual distance and a distance determined by the distance measurement method according to the comparative example.

[0067] In Fig. 8, an actual distance d is taken along the abscissa, and a distance determined by the distance measuring method according to the comparative example (a calculated distance) d caltaken along the ordinate. The pulse light Lp, whose pulse width Tp of the drive signal S D 30 ns is determined and used for the measurement. Distances in the abscissa and ordinate are distance-measurable ranges when the width is set to 30 ns, as in the first and second periods T1, T2, similar to the pulse width Tp of the drive signal S D A linear line B is a straight line that passes through the origin of coordinates and has a slope of 1.

[0068] As in Fig. 8, the distance measurement profile is divided into a linearity surface A line and non-linearity surfaces A short , A long The linearity area A line is an area where the actual distance d and calculated distance d cal are essentially similar (equivalent) and where a difference in the calculated distance d cal from the actual distance d (|dd cal| / d × 100 (%) ) is at or below a tolerance limit. The linearity area A line For example, is an area where the difference is several percent or less. In the linearity area A line the difference is so small that the distance measurement accuracy is high. In the linearity area A line measured data are essentially plotted on the linear line B.

[0069] On the other hand, the non-linearity surfaces A shorts A long surfaces other than the linearity surface A line . Those areas include an area where the actual distance d and calculated distance d cal are not equivalent in one area, , at least the linearity area A line In other words, the non-linearity surfaces A short , A long contain an area where the actual distance d and calculated distance d calare equivalent in an area that is not adjacent to the linearity area A line The area where the actual distance d and the calculated distance d cal are not equivalent, an area indicates where the difference exceeds the tolerance limit, for example, the difference exceeds several percent. The non-linearity area A short is defined at a closer position to the short distance as linearity area A line plotted. The non-linearity surface A long is plotted in a closer position to a long distance than the linearity area A line .

[0070] In the non-linearity surfaces A short , A long The measured data are plotted in positions offset from the linear line B. In the non-linearity areas A short , A longthe difference is so large that the distance measurement accuracy is low. This is because the influence of the amount of charges q2 with respect to the amount of charges Q2 in the non-linearity area A short becomes large. Furthermore, it is because the influence of the amount of charges q1 with respect to the amount of charges Q1 in the non-linearity surface A long grows up.

[0071] Fig. 9 is an example of a timing chart of various signals in a distance measuring method according to the present embodiment.

[0072] As in Fig. 9, in the example of the distance measuring method according to the present embodiment, the pulse width Tp of the drive signal S D preset to be an extension time Tx longer than the width of each of the first and second periods T1, T2. Accordingly, the width of the light intensity stable period T Sof the pulsed light Lp coming from the light source L S emitted is preset to be longer than the width of each of the first and second periods T1, T2. Similar to the comparison example, it should be noted that the first and second periods T1, T2 are different in timing and of similar width.

[0073] In such a case, with respect to the amounts of charges of Q1, Q2 accumulated in the first and second charge accumulating areas FD1, FD2, a percentage of increases in accordance with the light intensity stable period T S of the pulsed light Lp. Therefore, with respect to the amount of charges q1, which is less than the ideal case due to the rise period T R decreases, the influence of such a quantity of charges q1 becomes small with respect to the quantity of charges Q1. Furthermore, with respect to the quantity of charges q2, which decreases compared to the ideal case due to the decreasing period TF increases, the influence of such a quantity of charges q2 becomes small with respect to the quantity of charges Q2. As a result, the influences of the increasing period T R and falling period T F of the light intensity signal S Lp in terms of distance measurement accuracy. Accordingly, the distance measurement accuracy can be improved.

[0074] Fig. 10 is another example of the timing chart of the various signals in the distance measuring method according to the present embodiment.

[0075] As in Fig. As illustrated in Fig. 10, in another example of the distance measuring method according to the present embodiment, the pulse width Tp of the drive signal S D preset to be longer than the width of each of the first and second periods T1, T2 by the extension time Tx. In addition, the drive signal S Dpreset to be applied later than the first transfer signal S1 by a delayed emission time (delay time) Ty.

[0076] In such a case, with respect to the amount of charges Q2 accumulated in the second charge accumulation area FD2, the percentage of charges in accordance with the light intensity stable period T F of the pulsed light Lp continues to accumulate. Accordingly, with regard to the amount of charges q2, which ideally increases due to the decreasing period T F increases, the influence of such a quantity of charges q2 with respect to the quantity of charges Q2 remains small. This reduces the influence of the falling period T F of the light intensity signal S Lpin terms of distance measurement accuracy, especially for short distances. As a result, distance measurement accuracy can be improved, especially for short distances. When calculating the distance d, it should be noted that a distance corresponding to the delayed transmission time Ty is necessarily offset.

[0077] With reference to Fig. 11 describes a method of setting, in advance, the light intensity stable period T F and the delayed broadcast time Ty. Fig. 11 is a flowchart illustrating a method of setting the light intensity stable period and delayed emission time. Fig. 12 is an example of the distance measurement profile.

[0078] As in Fig. As illustrated in Figure 11, various measurement conditions are first set as initial settings, similar to the distance measurement method according to the comparative example (step S01). Specifically, the width of each of the first and second periods T1, T2 is set to a value T0 corresponding to the distance range to be measured, and the distance measurement range is set. The pulse width Tp of the drive signal S D is similarly set to T0. The delayed emission time Ty is set to zero. According to the delayed emission time Ty, an offset d ofs the delayed emission time Ty with respect to the calculated distance d cal set to zero.

[0079] Next, the distance measurement profile, which shows the relationship between the calculated distance d cal and the actual distance d (step S02). As in Fig. 12, the distance measurement profile is converted into the linearity area Aline and the non-linearity surfaces A short , A long divided.

[0080] Next, a distance d line the linearity surface A line and a minimum value d short of the distance range d line checked and a time range T line and a minimum value T short of which according to the aforementioned distance range d line and the minimum value d short calculated (step S03). Here the minimum value d short the linearity surface Aline a value of the distance range of the non-linearity surface A short .

[0081] Next, the measurement conditions are set again (step S04). Specifically, the pulse width Tp of the drive signal S D on T0+(T0-T line ). The delayed broadcast time Ty is set to T shortThe offset d is set according to the delayed transmission time Ty. ofs the delayed emission time Ty with respect to the calculated distance d cal on the short The width of each of the first and second periods T1, T2 is not changed.

[0082] Next, the distance measurement profile is prepared again (step S05). Next, it is determined whether the desired linearity properties are determined in the distance measurement profile (step S06). Specifically, the distance range d line the linearity surface A line and the minimum value d short the linearity surface A line determined whether they are within the desired range. The wider the distance range d line, the wider the distance range that can be measured with high accuracy. Furthermore, the smaller the minimum value d short , the shorter the minimum distance that can be measured with high accuracy becomes.

[0083] In a case where the answer in step S06 is Yes, the process is terminated. Accordingly, the minimum value T short of the time domain T line preset as delayed broadcast time Ty. Furthermore, the time range T line corresponding to the linearity area A line in advance as the light intensity stable period T S It should be noted that the pulse width Tp of the transfer electrodes is, of course, set in advance when the light intensity stable period T S is set in advance. In a case where the answer in step S06 is No, the process moves to step S03, and the processes from step S03 to S06 are repeated.

[0084] In the present embodiment, it may be that the influences of the increasing period T R and falling period T Fnot completely disappear and the entire distance measuring range is not considered as the linearity area A line with high distance measurement accuracy. However, by adjusting the light intensity stable period T S is set long in advance, the percentages of the increasing period T are reduced R and falling period T F within the emission period T T of the pulsed light Lp relative. Therefore, it is possible to determine the influences of the increasing period T R and falling period T F Accordingly, a percentage of the linearity area A line with high distance measurement accuracy across the entire distance measurement range. As a result, distance measurement accuracy is improved.

[0085] As mentioned above, in the distance measuring method according to the present embodiment, when the pulse light Lp from the light source L Sis emitted, the pulse light Lp is emitted, whose light intensity stable period T S within the emission period T T of the pulsed light Lp from the light source L S is preset to be longer than each of the first and second periods T1, T2.

[0086] The distance measuring device 10 according to the present embodiment includes the driving element DRV configured to drive the light source L S to drive the pulse light Lp, whose light intensity stable period T S within the emission period T T of the pulse light Lp is preset to be longer than each of the first and second periods T1, T2.

[0087] Accordingly, with respect to the amounts of charges Q1, Q2 accumulated in the first and second charge accumulating areas FD1, FD2 during each of the first and second periods T1, T2, the percentage of the amount increases according to the light intensity stable period T S accumulated charges and the percentages of the amounts of decrease in accordance with the increasing period T R and falling period T F accumulated charges. Therefore, with regard to the amount of charges Q1, which differs from the ideal case due to the rise period T R decreases, the influence of such a quantity of charges q1 with respect to the quantity of charges Q1 is small. Furthermore, with respect to the quantity of charges q2, which is smaller than in the ideal case due to the decreasing period T F increase, the influence of such a quantity of charges q2 relative to the quantity of charges Q2 is small. As a result, the influences of the rise period T Rand falling period T F of the light intensity signal S Lp in terms of distance measurement accuracy. Accordingly, the distance measurement accuracy can be improved.

[0088] In the distance measuring method based on the above-mentioned formula (1), the pulse widths Tp of the drive signal S D As long as the width of each of the first and second periods T1, T2 is adjusted, it is possible to measure from the distance where the phase difference Td is zero to the distance where the phase difference Td is equivalent to the width of each of the first and second periods T1, T2. However, even if the pulse width Tp of the drive signal S D is set as long as the width of each of the first and second pulse periods T1, T2 actually decreases the width of the light intensity stable period T S due to the influences of the increasing period T R and falling period T F. On the other hand, if the pulse width T P of the drive signal S D is deliberately set long in advance, in such a way that the width of the light intensity stable period T S is deliberately set long in advance, it is possible to compensate for the influence caused by the decrease in the width of the light intensity stable period T S caused.

[0089] Furthermore, when the pulsed light Lp is emitted from the light source LS, the pulsed light Lp is emitted later than the start time of the first period T1 by the delayed irradiation time Ty. Accordingly, with respect to the amount of charges Q2 accumulated in the second charge accumulating area FD2 during the second period T2, the percentage of the amount of charges increases in accordance with the light intensity stable period T. Saccumulated charges continue to increase. As a result, distance measurement accuracy can be improved, especially for short distances.

[0090] Furthermore, the delayed radiation time Ty of the emission timing of the pulse light Lp with respect to the start time of the first period T1 is set in advance to the minimum value T short corresponding to the minimum value d short the linearity surface A line of the distance measurement profile, which shows the correlation between the distance d determined by the actual distance d cal and the distance sensor P(m, n). In such a case, it is possible to measure under a condition where the distance is zero to the minimum value d short Therefore, it is possible to increase the distance measurement accuracy even with respect to the distance range below the minimum value d short to improve.

[0091] Furthermore, the distance sensors P(m, n) include the first and second charge accumulating areas FD1, FD2 and the first and second transfer electrodes TX1, TX2 configured to transfer the charges generated in the charge accumulating areas to the first and second charge accumulating areas FD1, FD2. The first and second transfer signals S1, S2 are applied to the first and second transfer electrodes TX1, TX2, respectively. There is a 180-degree shift between the phases of the first and second transfer signals S1, S2. Accordingly, each time the pulse light Lp is emitted once, the generated charges are accumulated in each of the first and second charge accumulating areas FD1, FD2, and the distance d to the object OJ can be determined. Therefore, it is possible to prevent deterioration of the distance measurement accuracy due to the time variation of the distance d to the object OJ.

[0092] A modification of the present embodiment will be described below. Fig. Fig. 13 is a view illustrating a configuration of a distance sensor according to the modification. It should be noted that a light intercepting layer LI is Fig. 13 is omitted.

[0093] As in Fig. As illustrated in Figure 13, a distance sensor P(m, n) according to the modification includes a photogate electrode PG, a first charge accumulating area FD1, and a first transfer electrode TX1. The distance sensor P(m, n) according to the modification differs from the above-mentioned embodiment in that it does not include the second charge accumulating area FD2 and the second transfer electrode TX2.

[0094] The photogate electrode PG has a rectangular ring shape when viewed from above. In the present modification, the photogate electrode PG has a square ring shape when viewed from above. A periphery of the photogate electrode PG corresponds to a periphery of the distance sensor P(m, n). The first charge accumulating area FD1 is formed within the square ring of the photogate electrode PG. The first charge accumulating area FD1 has a rectangular shape when viewed from above. In the present embodiment, the first charge accumulating area FD1 has a square shape. The first charge accumulating area FD1 when viewed from above is located at a substantial center of the distance sensor P(m, n).

[0095] The first transfer electrode TX1 is arranged between the photogate electrode PG and the first charge accumulating area FD1. The first transfer electrode TX1 has a rectangular ring shape when viewed from above. In the present modification, the first charge accumulating area FD1 has a square ring shape when viewed from above.

[0096] Fig. 14 is a timing chart of various signals in a range method according to the modification.

[0097] As in Fig. As illustrated in Figure 14, the first transfer signal S1 applied to the first transfer electrode TX1 is given a phase shifted intermittently at a predetermined timing. In the present modification, the first transfer signal S1 is given a phase shifted by 180 degrees at a time point of 180 degrees. The first transfer signal S1 is synchronized with a drive signal S Dat a time of zero degrees and has a phase difference of 180 degrees compared to the drive signal S D at the time of 180 degrees.

[0098] In the present modification, an amount of charge Q1 accumulated in the first charge-accumulating area FD1 at a time of 0 degrees and an amount of charge Q2 accumulated in the first charge-accumulating area FD1 at a time of 180 degrees are alternately read out. A distance d is calculated based on these charge amounts Q1, Q2.

[0099] In this way, the distance sensor P(m, n) includes the first transfer electrode TX1 configured to transfer the charges generated in the charge-generating area to the first charge-accumulating area FD1. The first transfer electrode TX1 is supplied with the first transfer signal S1 with a phase shifted by 180 degrees from time to time. In such a case, distance measurement can be performed by at least one transfer electrode TX1 and one first charge-accumulating area FD1. Therefore, the distance sensor P(m, n) can be downsized.

[0100] The present invention should not be limited to the aforementioned embodiment. For example, in the above-mentioned embodiment, the extension time Tx and the delayed emission time Ty are set in preparation of the distance measurement profile, but the embodiment should not be limited thereto. If there is known information regarding a signal waveform of the light intensity signal S Lp of the pulsed light Lp when the pulsed light Lp from the light source L S emitted, the extension time Tx and delayed emission time Ty can be adjusted based on the information. For example, if the width of the light intensity stable period T S is known, a difference between the width of each of the first and second periods T1, T2 and the width of the light intensity stable period T S than the extension time Tx.

[0101] Furthermore, if the width of the rise period T R of the light intensity signal S Lp is known, a value that determines the width of the rise period T R from the pulse width Tp of the drive signal S D subtracted as the width of the light intensity stable period T S Similarly, the extension time Tx can be calculated based on the considered width of the light intensity stable period T S be set.

[0102] Furthermore, when the pulse light Lp is emitted from the light source LS, the pulse light Lp can be emitted before the start time of the first period T j In such a case, the value of the delayed emission time Ty is negative. In a range close to the maximum value of the distance range that can be measured by the above-mentioned formula (1), that is, for example, the non-linearity area A long , the influence of the rise period T Rof the light intensity signal S Lp large. In other words, in this area, the influence of the amount of charges q1 relative to the amount of charges Q1 that deviates from the ideal is large. By setting the delayed radiation time Ty to a negative value, the influence of the amount of charges q1 relative to the amount of charges Q1 becomes small, which improves the distance measurement accuracy in this area.

[0103] In the distance image sensor RS, each of the distance sensors P(m, n) is arranged two-dimensionally, but each of them can be a line sensor arranged one-dimensionally. It should be noted that a two-dimensional image can also be obtained by rotating a line sensor or scanning with two line sensors.

[0104] The RS distance image sensor is not limited to the front-illuminated distance image sensor. The RS distance image sensor can also be a back-illuminated distance image sensor.

[0105] The charge generating area where the charges are generated in accordance with the incident light may include a photodiode (for example, an embedded photodiode).

[0106] The conductivity types (ie, p-type and n-type) of the distance image sensor RS according to the present embodiment may be replaced with each other to be opposite to those described above. Industrial applicability

[0107] The present invention is applicable to a distance measuring method and a distance measuring apparatus. List of reference symbols 10 Distance measuring device A line Linearity surface d distance d short Minimum value of linearity area FD1 first charge accumulating area FD2 second charge accumulating area P Distance sensor PG photogate electrode S1 first transfer signal S2 second transfer signal T1 first period T2 second period TX1 first transfer electrode (charge transfer unit) TX2 second transfer electrode (charge transfer unit) L S light source CONT control element (charge transfer unit) DRV drive element (light source drive element) ART arithmetic element (distance arithmetic element) OJ Object Lp pulse light Lr reflected light T S light intensity stable period T T Emission period of pulsed light Ty delayed broadcast time (delay time Q1, Q2 set of charges

Claims

[1] A distance measuring method in which a light source configured to emit pulsed light with respect to an object and a distance sensor are used, the distance sensor including a charge generating area in which charges are generated according to incident reflected light of the pulsed light reflected from the object, and a charge accumulating area in which the charges generated in the charge generating area are accumulated, the distance measuring method comprising: Transferring the charges generated in the charge generating area to the charge accumulating area during a first period with respect to an emission period of the pulse light, so as to accumulate the charges in the charge accumulating area during the first period; Transferring the charges generated in the charge-generating area to the charge-accumulating area during a second period that is different in timing from the first period and similar in width to the first period, so as to accumulate the charges in the charge-accumulating area during the second period; Arithmetizing a distance to an object based on an amount of charge accumulated in the charge accumulating area during the first period and an amount of charge accumulated in the charge accumulating area during the second period; and when emitting the pulsed light from the light source, emitting the pulsed light whose light intensity stable period within the emission period of the pulsed light is set in advance to be longer than each of the first and second periods, from the light source, wherein the pulse light is emitted after a start time of the first period when the pulse light is emitted from the light source, and wherein a delay time of the emission timing of the pulse light with respect to the start time of the first period is set in advance to a time corresponding to a minimum value of a linearity surface of a distance measurement profile indicating a correlation between an actual distance and a distance detected by the distance sensor. [2] Distance measuring method according to claim 1, wherein the distance sensor includes a plurality of charge accumulating surfaces and a plurality of transfer electrodes configured to transfer the charges generated in the charge generating surface to the plurality of charge accumulating surfaces, and the majority of transfer electrodes are given transfer signals with different phases. [3] Distance measuring method according to claim 1 or 2, wherein the distance sensor includes a transfer electrode configured to transfer the charges generated in the charge-generating area to the charge-accumulating area, and the transfer electrode is given a transfer signal having a phase shifted intermittently at a predetermined timing.

4. A distance measuring device comprising: a light source configured to emit pulsed light with respect to an object, and a distance sensor configured to include a charge generating area in which charges are generated according to incident reflected light of the pulsed light reflected from the object, and a charge accumulating area in which the charges generated in the charge generating area are accumulated, the distance measuring device comprising: a charge transfer unit configured to transfer the charges generated in the charge generation area with respect to an emission period of the pulsed light to the charge accumulating area during a first period, thereby accumulating the charges in the charge accumulating area during the first period, and configured to transfer the charges generated in the charge generation area to the charge accumulating area during a second period, different from the first period in timing and similar to the first period in width, thereby accumulating the charges in the charge accumulating area during the second period; a distance arithmetic element configured to arithmeticize a distance to the object based on an amount of charges accumulated in the charge accumulating area during the first period and an amount of charges accumulated in the charge accumulating area during the second period; and a light source driving element configured to drive the light source to emit the pulse light, whose light intensity stable period within the emission period of the pulse light is preset to be longer than each of the first and second periods, from the light source, wherein the pulse light is emitted after a start time of the first period when the pulse light is emitted from the light source, and wherein a delay time of the emission timing of the pulse light with respect to the start time of the first period is set in advance to a time corresponding to a minimum value of a linearity surface of a distance measurement profile indicating a correlation between an actual distance and a distance detected by the distance sensor.

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