JP3591962B2 - Distance measuring device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a distance measuring apparatus that measures a distance to a distance measurement target by triangular distance measurement, and is suitably applied to, for example, an AF mechanism of a camera. More specifically, a plurality of charge transfer channel units are arranged in a ring shape (loop shape) to form a cyclic shift register (ring unit). The cyclic shift register gradually circulates signal charges according to charge transfer pulses while gradually circulating the signal charges. The present invention relates to a distance measuring device configured to add a signal charge to a distance measuring device.
[0002]
[Prior art]
As a distance measuring device for measuring the distance to the object to be measured, Japanese Patent Publication No. 5-22843 discloses a ring-shaped charge transfer unit for integrating signals and simultaneously removing external light to the ring unit. One having skim means has been proposed. According to this, when the signal charges are not at a sufficient level, the signal charges are sequentially added while being transferred in the ring portion which is a cyclic shift register, so that a signal charge having a good S / N ratio can be obtained.
[0003]
[Problems to be solved by the invention]
However, when the signal charges are transferred to a circulating shift register configured using a CCD (charge coupled device) or the like, when the transfer efficiency is less than 100%, a signal is circulated to a rear register (charge transfer channel) so that the signal charges are circulated. Signal charges gradually leak. For this reason, the distribution of the signal charge injected into the cyclic shift register changes little by little while continuing to circulate. Then, when performing the distance measurement operation, the change in the signal charge distribution causes an error in the operation result. In particular, when a non-signal portion exists in the charge transfer channel of the cyclic shift register, the amount of charge in the charge transfer channel adjacent to the non-signal portion gradually changes. This will be described with reference to FIG.
[0004]
FIG. 10A is a schematic diagram showing the distribution of charges in the cyclic shift register before the transfer is repeated, and shows uniform charge portions 51 to 63 of the charge transfer channel (for example, corresponding to the region irradiated with external light). 1), a uniform charge amount (1) is injected, and non-signal portions 71 to 74 are formed between the uniform charge portions 51 to 63. This cyclic shift register leaves 10% of the signal charge per transfer. That is, 10% of the charge amount (2) of the charge amount (1) remains as a residual charge in the charge transfer channel before the transfer.
[0005]
At this time, if the entire charge is transferred once, the charge distribution becomes as shown in FIG. That is, the charge of the uniform charge portion 51 is transferred to the charge transfer channel on the left side and is reduced to 90% of the initial charge amount (1), but the charge of the uniform charge portions 52 to 63 is the same as the charge remaining at the time of transfer. Since the amount of charge is left in the previous charge transfer channel, it does not change eventually. Further, the non-signal portion 71 has the charge amount (2) due to the residual charge of the uniform charge portion 63.
[0006]
When the charge is further transferred once, the distribution of the charge becomes as shown in FIG. That is, since the charge of the uniform charge portion 51 has already been reduced to 90% at the stage of FIG. 10B, it is reduced to 81% of the initial charge amount (1), and the residual charge of the uniform charge portion 51 is the initial charge. The charge amount is 9% of (1). Since the uniform charge portion 52 retains 10% of the charge, the addition of 9% from the uniform charge portion 51 results in a charge amount of 99% of the initial value.
[0007]
When the charge is further transferred once, the distribution of the charge is as shown in FIG. That is, the charge of the uniform charge portion 51 is about 73% of the initial charge amount (1), and the charge of the uniform charge portion 52 is about 97% of the initial value. Further, the charge of the uniform charge portion 53 is slightly reduced. Conversely, charges are gradually accumulated in the non-signal portions 71 to 73. As described above, when the transfer efficiency of the charge transfer channel is less than 100%, particularly, the amount of charge in the non-signal portion and the charge transfer channel adjacent thereto is gradually changed while the transfer is repeated. However, there has been a problem that the size becomes larger.
[0008]
Therefore, an object of the present invention is to provide a distance measuring apparatus having a cyclic shift register (ring section), which can perform accurate distance measurement even when a non-signal section exists in a charge transfer channel. It is to provide.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a distance measuring apparatus of the present invention is a distance measuring apparatus that repeatedly emits a pulsed light beam to a distance measuring object, receives reflected light thereof, and performs triangulation. A light projecting means for projecting light onto the object to be measured, a plurality of photoelectric conversion elements for receiving reflected light from the object to be measured and performing photoelectric conversion, and integrating a signal charge output from the photoelectric conversion element Signal charge supply means for transferring and transferring the signal charge supplied from the signal charge supply means in one direction, and a plurality of charge transfer channels. And a circulating shift register in which signal charges injected from the signal charge supplying means via the signal charge injecting means are accumulated while being circulated, and generated in the charge transfer channel of the circulating shift register. Calculating means for performing distance measurement while ignoring signal charges existing in at least one of the charge transfer channels adjacent to the non-signal portion, wherein the calculating means is configured to reduce the number of times of accumulation of signal charges in the cyclic shift register. It is characterized in that the number of charge transfer channels corresponding to charge signals to be ignored increases as the number of charge transfer channels increases.
[0012]
In one embodiment of the present invention, the number of charge transfer channels of the signal charge injection means is greater than the number of charge transfer channels of the cyclic shift register.
[0013]
In one embodiment of the present invention, a transfer electrode to which a charge transfer pulse is applied is provided over the charge transfer channel via a gate insulating film.
[0014]
In one embodiment of the present invention, at least one of the charge transfer channels of the cyclic shift register is provided with a floating gate electrode portion for detecting a transferred signal charge amount via a gate insulating film.
[0015]
That is, the distance measuring apparatus according to the present invention is characterized in that signal charges of several charge transfer channels adjacent to the non-signal portion of the charge transfer channel of the cyclic shift register are ignored during distance measurement calculation. As a result, in a cyclic shift register having a charge transfer channel with a transfer efficiency of less than 100%, the signal charge of the charge transfer channel adjacent to the non-signal charge transfer channel causes a small amount of transfer leakage every time transfer is performed, resulting in a small charge amount. Is smaller than the initial value, but the distance calculation is performed ignoring those signal charges, so that the measurement result is not affected and a correct distance measurement result can be obtained.
[0016]
Further, in the distance measuring apparatus of the present invention, if the decrease of the signal charge of the charge transfer channel adjacent to the non-signal portion is small due to the reason that the number of times of transfer of the charge in the cyclic shift register is small, etc. Reduce the number of charge transfer channels corresponding to signal charges to ignore. In addition, if the signal charge of the charge transfer channel adjacent to the non-signal portion is greatly reduced due to a large number of charge transfers in the cyclic shift register or the like, the charge transfer channel corresponding to the signal charge to be ignored in the distance measurement calculation. Increase the number of. In other words, since the signal charge to be ignored is changed in accordance with the change in the signal charge of the charge transfer channel due to the charge transfer, the signal charge of more photoelectric conversion elements can be used accordingly, and the distance measurement calculation is performed from a wide range. It becomes possible.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[0019]
(First embodiment)
FIG. 1 is a schematic diagram showing a main part of the distance measuring apparatus of the present embodiment, and FIGS. 2 to 4 are time charts for explaining an operation sequence of the distance measuring apparatus of the present embodiment. In FIG. 1, a sensor array 11 includes a plurality of photoelectric conversion elements (pixels) S for converting received light into electric charges. ₁ ~ S ₅ Consists of In the present embodiment, the sensor array 11 is S ₁ ~ S ₅ Although the description will be made assuming that the pixel is composed of five pixels, in practice, the number of pixels can be arbitrarily set, and the pixel is generally composed of 20 or more photoelectric conversion elements depending on the distance measurement range and the required distance measurement accuracy. Is preferred.
[0020]
In each integration section 12, each pixel S of the sensor array 11 ₁ ~ S ₅ Is integrated. The clear unit 13 provided adjacent to each of the integrating units 12 empties (clears) the electric charge integrated by the integrating unit 12 when the ICG pulse is applied. The first storage unit 14 is ST ₁ The charge is received from the integration unit 12 by a pulse, and the second storage unit 15 that is paired with the first storage unit 14 ₂ The charge is received from the integrator 12 by a pulse. When the SH pulse is applied to the shift unit 16 at the timing shown in FIG. 2, the charges stored in the first storage unit 14 and the second storage unit 15 are transferred to the plurality of charge transfer channels 1. _A ~ 12 _A All move to the linear CCD 17 (signal charge injection means). In the present embodiment, the integration unit 12, the clear unit 13, the first storage unit 14, the second storage unit 15, and the shift unit 16 constitute a signal charge supply unit.
[0021]
Multiple charge transfer channels 1 _A ~ 12 _A The transfer clock pulse CK is supplied to the linear CCD (signal charge injection means) 17 having the timing shown in FIG. ₁ , CK ₂ Are alternately applied, and these transfer clock pulses CK ₁ , CK ₂ Accordingly, the electric charges moved from the first accumulation unit 14 and the second accumulation unit 15 are transferred in the transfer direction I in the linear CCD 17. Here, the transfer clock pulse is described as having two phases, but any number of transfer clock pulses may be used.
[0022]
In the present embodiment, the charge transfer channel 1 _A ~ 12 _A Above the transfer clock pulse CK via a gate oxide film (not shown) ₁ , CK ₂ Is applied.
[0023]
A plurality of charge transfer channels 1 are provided at the end of the linear CCD 17 on the transfer direction I side. _B ~ 12 _B Are connected in a ring shape. Transfer clock pulse CK to ring CCD 18 ₁ , CK ₂ Are applied alternately, and each charge transfer channel 1 _B ~ 12 _B Are transferred in the transfer direction II and circulate around the ring CCD 18.
[0024]
Each charge transfer channel 1 of the linear CCD 17 _A ~ 12 _A At the transfer clock pulse CK ₁ , CK ₂ Is transferred in the transfer direction I. Charge transfer channel 1 _A At the transfer clock pulse CK ₂ Is transferred to the next charge transfer channel, and the next transfer clock pulse CK ₁ The charge transfer channel 12 of the ring CCD 18 _B Will be forwarded to However, the charge transfer channel 1 of the ring CCD 18 _B The charge originally existing in the charge transfer channel 12 _B Is transferred to the charge transfer channel 12 _B In, the respective charges are added together.
[0025]
Here, the number of charge transfer channels of the linear CCD 17 and the number of charge transfer channels of the ring CCD 18 are made to match, and _A And 1 _B , 2 _A And 2 _B , 3 _A And 3 _B , ..., ..., 11 _A And 11 _B , 12 _A And 12 _B Are always added. However, the charge transfer channel 1 where no signal charge is injected from the sensor array 11 _A , 2 _A Since there is no charge initially, no signal [charge] portion is formed in the ring CCD 18 in response to this.
[0026]
When the CCD CLR signal is applied to the CCD clear unit 20, the charge transfer channel 1 _B Charge becomes empty. Accordingly, the CCDCLR signal is applied to the CCD clear unit 20 at the timing indicated in the initialization mode of the operation sequence of FIG. ₁ , CK ₂ Is applied, the electric charge existing in the ring CCD 18 always becomes the electric charge transfer channel 1 _B , The charges are emptied in the CCD clear section 20, and all the charges in the ring CCD 18 can be emptied (reset state).
[0027]
The output unit 21 is connected to the charge transfer channel 6 _B The output amplifier 101 is connected to a floating gate electrode portion 102 provided above via a gate oxide film, and is connected to the charge transfer channel 6. _B Is converted into a voltage, and an OS signal is output to an external device at the timing shown in FIG. The reset potentials RD and RS ₁ Pulse is connected, and RS is connected at the timing shown in FIG. ₁ When the pulse is applied, the floating electrode unit 102 is reset to the reset potential RD.
[0028]
The device shown in FIG. 5 is an example in which the distance measuring device provided with the ring CCD (circulating shift register) 18 described in FIG. 1 is applied to an automatic focusing device of a camera. The autofocus device handles signals from a short-distance / high-reflectance subject to a long-distance / low-reflectance subject, and therefore requires an extremely large dynamic range (typically about 1: 1000). Therefore, it is difficult to secure a sufficient dynamic range in the signal processing circuit, and various measures have been taken. In the example described here, if the signal level is high, the accumulation addition operation in the ring CDD 18 is stopped after several accumulations, and if the signal level is low, the accumulation is repeated several hundred times, which is sufficient for the distance measurement operation. To obtain a proper signal level. Since the distance measuring apparatus shown in FIG. 5 includes two devices similar to those shown in FIG. 1, here, the same members as those in FIG. 1 are denoted by the same reference numerals with "R" or "L". It shall be added.
[0029]
In FIG. 5, a pulsed light beam emitted from the IRED 201 that emits near-infrared light is condensed by the light projecting lens 207 and strikes the subject 221. Part of the near-infrared light reflected by the subject 221 is condensed by the light receiving lens 208R to form a light receiving image 222R on the sensor array 11R. The near-infrared light condensed by passing through the light receiving lens 208L forms a light receiving image 222L on the sensor array 11L.
[0030]
The IRED drive circuit 202 drives the IRED 201 to blink at a predetermined cycle. The signal charge integration units (signal charge supply units) 12R to 16R and 12L to 16L integrate the signal charges of the respective sensor arrays 11R and 11L and accumulate them at predetermined timing in the linear CCDs (signal charge injection units) 17R and 17L. Supply the charge.
[0031]
The signal charges supplied to the linear CCD 17R are injected into the circulating shift register 18R according to a transfer clock which is one of the drive pulses 203 generated by the AF processing circuit 206. Similarly, the signal charge supplied to the linear CCD 17L is also injected into the cyclic shift register 18L. The signal charges circulating in the circulating shift registers 18R and 18L are read from the floating electrode units 102R and 102L and transferred to the AF processing circuit 206 via the output amplifiers 101R and 101L. The AF processing circuit 206 obtains a distance D to the subject 221 from the position Xr of the light reception image 222R on the sensor array 11R and the position Xl of the light reception image 222L on the sensor array 11L.
[0032]
The AF processing circuit 206 includes an A / D converter 204, a CPU 210, and a memory 211, and drives the sensor arrays 11R and 11L, the signal integrators 12R to 16R and 12L to 16L, and the cyclic shift registers 18R and 18L. And generates a drive pulse 203 for controlling the operation.
[0033]
In FIG. 5, the three lenses of the light projecting lens 207, the light receiving lens 208R, and the light receiving lens 208L are on the same straight line, the distance between the light receiving lenses 208R and 208L is B, and the distance between the light receiving lens 208R and the light projecting lens 207 is K. The subject 221 is separated from the light projecting lens 207 by a distance D in the vertical direction. The distance between the sensor array 11R and the sensor array 11L is also B, and the sensor arrays 11R and 11L are set apart from the light receiving lenses 208R and 208L by a common focal length f for each lens. Further, the distance from one end of the sensor array 11R to the light receiving image 222R is Xr, and the distance from one end of the sensor array 11R to the vertical projection point of the principal point of the light receiving lens 208R to the sensor array 11R is ΔX. The distance from one end of the sensor array 11L to the light receiving image 222R is Xl, and the distance from one end of the sensor array 11L to the vertical projection point of the main point of the light receiving lens 208L onto the sensor array 11L is ΔX.
[0034]
Here, since two triangles each having the principal point of the light receiving lenses 208R and 208L as a common vertex are similar,
D / K = f / (Xr−ΔX)... ▲ 1 ▼
D / (B + K) = f / (X1-ΔX) (2)
Holds. By eliminating K from these equations (1) and (2) and solving for D,
D = B · f / (X1−Xr)... ③
It becomes. That is, since B and f are constant and known values, if the positions Xr and Xl of the light-receiving images 222R and 222L on the sensor arrays 11R and 11L are detected, the distance D to the subject 221 can be obtained by triangulation. .
[0035]
FIG. 6 is an enlarged view of the structure from the sensor array 11 to the linear CCD 17 in the apparatus shown in FIG. Hereinafter, the flow of charges in the distance measuring apparatus of the present embodiment will be described with reference to FIGS.
[0036]
First, in FIG. 5, the AF processing circuit 206 causes the IRED 201 to blink via the IRED drive circuit 202. Therefore, the light receiving images 222R and 222L caused by the light beam from the IRED 201 also blink. That is, when the IRED 201 is turned on, light-receiving images 222R and 222L appear on the sensor arrays 11R and 11L, and the light-receiving image signals and external light are transmitted to the pixels (photoelectric conversion elements) S of the sensor arrays 11R and 11L. ₁ ~ S ₅ Is converted into an electric charge. When the IRED 201 is turned off, the pixels S of the sensor arrays 11R and 11L are turned off. ₁ ~ S ₅ , Only external light hits, and only this external light is converted into electric charges.
[0037]
In FIG. 6, one pixel (sensor) S in the sensor array 11 ₂ The signal charge photoelectrically converted in the step (a) passes through the path 301 and is integrated by the integration unit 12. Then, by applying an ICG pulse to the ICG line connected to the clear unit 13 at the timing shown in FIG. 2, the signal charges in the integrating unit 12 flow out to a ground line (not shown) through the path 302. That is, the charge of the integration section 12 is cleared. Therefore, by controlling the ICG pulse, it is possible to obtain a function as a so-called electronic shutter that arbitrarily changes the time for accumulating the electric charge in the integration section 12.
[0038]
The pulse ST from the ICG pulse shown in FIG. ₁ , ST ₂ Time t ₁ , T ₂ Is the integration time. Each integration unit 12 has a first storage unit 14 and a second storage unit 15 at adjacent positions. The first integrator 14 includes the ST shown in FIG. ₁ At the timing of the pulse, the charge flows from the integrator 12 via the path 304. In addition, the second storage unit 15 stores ST ₂ At the timing of the pulse, charge flows from the integrator 12 via the path 303. The first storage unit 14 and the second storage unit 15 are alternately arranged, and a shift unit 16 is provided thereunder.
[0039]
When the shift pulse SH is applied to the shift unit 16, the charge stored in the first storage unit 14 is transferred to the charge transfer channel of the linear CCD 17 via the path 306. Further, the electric charge accumulated in the second accumulation unit 15 is transferred to the electric charge transfer channel of the linear CCD 17 via the path 305.
[0040]
By the way, as shown in FIG. ₁ Since the AF processing circuit 206 controls the pulse so as to be output in synchronization with the light-off state of the IRED 201 (immediately before the light-on), the first accumulation unit 14 has a charge caused by external light that has hit the sensor array 11. Is accumulated. ST ₂ Since the AF processing circuit 206 controls the pulse so as to be output in synchronization with the lighting state of the IRED 201 (immediately before turning off), the second accumulation unit 15 stores the signal reflected from the subject that has hit the sensor array 11. And the extraneous light component are accumulated. The charges accumulated in the first accumulation unit 14 and the second accumulation unit 15 by the SH pulse are transferred to the charge transfer channel 3 shown in FIG. _A ~ 12 _A Respectively. Therefore, the odd-numbered charge transfer channels 3 _A , 5 _A , 7 _A , 9 _A , 11 _A The charge corresponding to the external light is stored in the even-numbered charge transfer channel 4. _A , 6 _A , 8 _A , 10 _A , 12 _A , The sum of the signal reflected from the subject and the charge of the external light is transferred.
[0041]
Note that charge transfer channel 1 _A , 2 _A Is a charge transfer channel added due to the configuration of the linear CCD 17 and the circulating shift register 18, but initially becomes a non-signal portion in which signal charges from the sensor array 11 are not directly transferred from the shift portion 16.
[0042]
The cyclic shift register 18 receives the clock pulse CK ₁ , CK ₂ The charge is transferred in the transfer direction II in FIG. As shown in FIG. 2, the SH pulse is generated in synchronization with one rotation of the cyclic shift register 18, and is further turned on and off of the IRED 201 and the pulse ST. ₁ , ST ₂ Are synchronized with the SH pulse, each charge transfer channel 1 of the cyclic shift register 18 is _B ~ 12 _B Always has the same pixel S ₁ ~ S ₅ , And the signal charges obtained by integrating the charges from are added.
[0043]
In the distance measuring apparatus shown in FIG. 5, in the initialization mode shown in FIG. 3, the time t explained in FIG. ₁ And time t ₂ But,
t ₁ = T ₂ = 0
ST under the condition ₁ , ST ₂ , ICG, CK ₁ , CK ₂ Are output. t ₁ = T ₂ By setting = 0, the charge of the integration unit 12 becomes empty. Further, by applying the pulse of the CCD CLR for a period in which the electric charge makes three rounds of the circulation shift register 18, the electric charge remaining in the first accumulation unit 14, the second accumulation unit 15, the linear CCD 17, and the circulation shift register 18 is reduced. All are eliminated via the CCD clear unit 20 shown in FIG. After the electric charge of each part is completely emptied, the pulse of the CCD CLR is stopped as shown in FIG. 3, and the mode is shifted to the integration mode.
[0044]
In this integration mode,
t ₁ = T ₂ $ 0
ICG, ST under the condition ₁ , ST ₂ , SH, CK ₁ , CK ₂ Are operated at a predetermined timing shown in FIG. At this time, as described above, the charge due to the external light when the IRED 201 is turned off is transferred to the charge transfer channel 3 of the linear CCD 17 via the first accumulation unit 14. _A , 5 _A , 7 _A , 9 _A , 11 _A And further added one after another in the cyclic shift register 18 and accumulated. Similarly, the charge obtained by adding the signal component reflected from the subject and the external light component when the IRED 201 is turned on is transferred to the charge transfer channel 4 of the linear CCD 17 via the second storage unit 15. _A , 6 _A , 8 _A , 10 _A , 12 _A And further added one after another in the cyclic shift register 18 and accumulated.
[0045]
An OS signal, which is an output signal of the output unit 21, is transmitted to the AF processing circuit 206 via the amplifiers 101R and 101L. When the OS signal reaches a level sufficient to perform the distance measurement calculation, the mode shifts to the read mode shown in FIG. 3, in which the SH pulse is stopped and the addition of the signal charge is stopped. The OS signal is output at the timing shown in FIG. 4. To facilitate the A / D conversion of this signal and capture it, the transfer clock pulse CK is used. ₁ , CK ₂ Lower the frequency of FIG. 4 shows a transfer clock pulse CK having a frequency of 240 kHz. ₁ , CK ₂ Is the transfer clock pulse CK having a frequency of 15 kHz. _A , CK _B (Reset pulse RS at this time ₁ ).
[0046]
The level of the OS signal A / D converted by the A / D converter 204 provided in the AF processing circuit 206 is written to the memory 211 via the CPU 210. The data written in the memory 211 is as follows in the output order of the OS signal of the distance measuring operation.
[0047]
No signal level
No signal level
Pixel S ₁ Outside light component hit
Pixel S ₁ Outside light component + signal component
Pixel S ₂ Outside light component hit
Pixel S ₂ Outside light component + signal component
…………………
Pixel S ₅ Outside light component hit
Pixel S ₅ Outside light component + signal component
[0048]
Therefore, the following operation is performed to calculate each pixel S ₁ ~ S ₅ Can be extracted.
Level of non-signal part-level of non-signal part = 0
(Pixel S ₁ -Light component + signal component)-(pixel S ₁ = External light component that hits) = pixel S ₁ Signal hits
(Pixel S ₂ -Light component + signal component)-(pixel S ₂ = External light component that hits) = pixel S ₂ Signal hits
…………………………………………………………
(Pixel S ₅ -Light component + signal component)-(pixel S ₅ = External light component that hits) = pixel S ₅ Signal hits
[0049]
The positions Xr and Xl of the light-receiving images 222R and 222L can be obtained from the result of performing the above processing on the two cyclic shift registers 18R and 18L shown in FIG. Further, by substituting these positions Xr and Xl into Equation (3), the distance D to the subject 221 can be calculated.
[0050]
FIG. 7 shows a sensor array 11, an integration unit 12, a clear unit 13, a first storage unit 14, a second storage unit 15, and a shift unit 16 of the distance measuring apparatus shown in FIG. FIG. 3 is a schematic diagram of a signal integration section), a linear CCD 17, a cyclic shift register 18, and the like. In FIG. 7, the sensor array 11 has ten pixels S ₁ ~ S ₁₀ The description will be made assuming that it is composed of In addition, light rays from the IRED 201 reflected from the subject and external light impinge on the sensor array 11, and a light receiving image 222 is formed.
[0051]
FIG. 8 shows each charge transfer channel 1 when the accumulation operation is performed in this state. _B ~ 22 _B And the pixel S ₁ ~ S ₁₀ 2 shows the distribution of the signal level. In FIG. 8A, each charge transfer channel 1 _B ~ 22 _B 1 is a charge distribution obtained by one accumulation in the cyclic shift register 18 (that is, one lighting of the IRED 201). Reference numeral 2 shown by a thin line indicates a charge amount distribution when accumulation in the cyclic shift register 18 is repeated 10 times. _B ~ 22 _B Is 100% ideal. Further, 3 shown by a broken line is a charge amount distribution when the transfer efficiency is about 99.5%.
[0052]
When the above-described calculation of (external light component + signal component)-(external light component) is performed based on the charge amount distribution 2, the power distribution of the IRED 201 that hits the sensor array 11 when the transfer efficiency is ideal is obtained. From this power distribution, as shown in FIG. 8B, the received light image 4 of the IRED 201 is reproduced, and based on this, the ideal position X (for example, the peak position or the center of gravity) of the received light image 4 can be obtained. .
[0053]
Similarly, the power distribution of the IRED 201 that hits the sensor array 11 can be obtained by performing the calculation of (external light component + signal component) − (external light component) from the charge amount distribution 3. As shown in FIG. 8C, the received light image 5 of the IRED 201 is reproduced from the power distribution, and the position X of the received light image 5 can be obtained from the reproduced light. However, at this time, the charge transfer channel 1 _B ~ 22 _B Is less than 100%, a false light-receiving image 6 appears next to the light-receiving image 5 and becomes noise in the distance measurement calculation.
[0054]
Therefore, the charge transfer channel 1 _B ~ 22 _B No signal part 1 _B , 2 _B (Charge transfer channel 1 is generated by the first lighting of LRED 201) _A , 2 _A Charge transfer channel 3 adjacent to the non-signal portion formed in _B , 4 _B (Pixel S ₁ , S ₂ (Corresponding to) is ignored, and both are set to 0. If the calculation of (external light component + signal component)-(external light component) is then performed, a more accurate power distribution of the IRED 201 that strikes the sensor array 11 is obtained. From this power distribution, as shown in FIG. _B ~ 22 _B Ya 1 _A ~ 22 _A Even if the transfer efficiency is less than 100%, the light-receiving image 7 of the IRED 201 without noise can be reproduced. That is, the false light receiving image 6 as shown in FIG. 8C disappears, noise in the distance measurement calculation can be reduced, and accurate distance measurement can be performed. In addition, the non-signal part 1 _B , 2 _B The signal charge appearing in the above is naturally ignored as noise, and the distance measurement calculation is performed.
[0055]
FIG. 9 is a diagram corresponding to FIG. 8 in the case where the power of the IRED 201 that hits the sensor array 11 is smaller than in the case of FIG. 8 and accumulation is repeated 20 times. In FIG. 9A, each charge transfer channel 1 _B ~ 22 _B Is a charge distribution obtained by accumulation 20 times in the circulating shift register 18 (that is, 20 times of lighting of the IRED 201), which is an ideal one with a transfer efficiency of 100%. . Reference numeral 33 indicated by a broken line indicates a charge amount distribution when the transfer efficiency is about 99.5%.
[0056]
When the calculation of (external light component + signal component) − (external light component) is performed from the charge amount distribution 32, the power distribution of the IRED 201 that hits the sensor array 11 is obtained. From this power distribution, as shown in FIG. 9B, the received light image 34 of the IRED 201 is reproduced, and from this, an ideal position X (for example, a peak position or a center of gravity) of the received light image 34 can be obtained.
[0057]
Similarly, the power distribution of the IRED 201 that hits the sensor array 11 can be obtained by performing the calculation of (external light component + signal component) − (external light component) from the charge amount distribution 33. From this power distribution, the received light image 35 of the IRED 201 is reproduced as shown in FIG. However, in this case, the charge transfer channel 1 _B ~ 22 _B The signal level of the false light receiving image 36 generated due to the transfer efficiency of less than 100% is higher than that of the true light receiving image 35. For example, the peak position of the signal level is set as the position of the light receiving image. When obtaining, the peak position XX of the false light receiving image 36 is adopted as the position of the light receiving image.
[0058]
Therefore, when the number of signal accumulations is large, the charge transfer channel 1 _B ~ 22 _B No signal part 1 _B , 2 _B 3 adjacent to _B , 4 _B , And the next 5 _B , 6 _B Any signal level is assumed to be 0 by disregarding the amount of charge of. Then, the calculation of (external light component + signal component)-(external light component) is performed to determine the power distribution of the IRED 201 that hits the sensor array 11, and from this power distribution, as shown in FIG. The light receiving image 37 of the IRED 201 without the image is reproduced. That is, the charge transfer channel 1 _B ~ 22 _B Even if the transfer efficiency is less than 100%, the false light receiving image 36 disappears, and the correct position X is obtained.
[0059]
As described above, in the present embodiment, the circulating shift register 18 is configured to convert external light that has hit the sensor array 11 or a signal reflected from a subject into electric charges, and accumulate the electric charges gradually while circulating the electric charges. In the ranging device used, the charge transfer channel 1 of the cyclic shift register 18 _B ~ 22 _B No signal part 1 _B , 2 _B The adjacent signal charge (in the direction opposite to the charge circulation direction when viewed from the non-signal portion) is ignored during the distance measurement calculation (that is, the accumulated charge = 0). As a result, even if the charge transfer efficiency is less than 100%, it is possible to prevent the generation of a false light-receiving image, obtain an accurate position of the light-receiving image, and calculate this to obtain an accurate distance to the subject. It becomes. Even if the distance measurement operation is performed ignoring the predetermined signal charges, the pixels corresponding to the ignored signal charges are only a part of the pixels on which the actual light-receiving image is formed. Has almost no effect on ranging. In the present embodiment, since the first storage unit 14 and the second storage unit 15 are used as a pair, the signal charges of the even number of charge transfer channels are ignored. May ignore the signal charges of the odd number of charge transfer channels.
[0060]
Also, for example, when the signal charge is small and the number of accumulations in the cyclic shift register 18 is large, the charge transfer channel 1 _B ~ 22 _B When the influence of the non-signal portion becomes wide, by increasing the charge transfer channels corresponding to the signal charges to be ignored in the distance measurement calculation, it is possible to prevent the generation of a false light receiving image even if the charge transfer efficiency is less than 100%. It is possible to obtain an accurate position of the received light image, calculate the position, and obtain an accurate distance to the subject.
[0061]
(Second embodiment)
Next, a second embodiment of the present invention will be described.
[0062]
In the distance measuring apparatus of the present embodiment, at least one dummy pixel is provided adjacent to the pixel of the sensor array, and the same external light as that for the pixel of the sensor array is incident on the dummy pixel, and the distance is measured. At the time of distance calculation, signal charges caused by dummy pixels are ignored. Specifically, in the signal processing unit of the distance measuring apparatus having the structure shown in FIG. ₃ ~ S ₁₀ And a pixel S corresponding to the charge transfer channel adjacent to the non-signal portion. ₁ , S ₂ As a dummy (a light receiving image is not formed) so that the signal charge is not used for the distance measurement calculation.
[0063]
That is, the pixel S ₁ , S ₂ Is transferred to the circulating shift register 18 and the accumulation operation is repeated. If the charge transfer efficiency is less than 100%, the pixel S ₁ , S ₂ Charge transfer channel 3 in the range _B ~ 6 _B Signal charge of the charge transfer channel 1 _B ~ 22 _B No signal part 1 _B , 2 _B Because it is adjacent to, it leaks under the influence. However, the pixel S ₁ , S ₂ Is ignored during the distance measurement calculation as a dummy, so that the ₂ And has no effect on the result of the distance calculation.
[0064]
As described above, in the distance measuring apparatus according to the present embodiment, the pixel group S necessary for performing the distance measurement is set. ₃ ~ S ₁₀ , A dummy pixel S that ignores the signal charge amount during the distance measurement calculation ₁ , S ₂ And the dummy pixel S ₁ , S ₂ Charge transfer channel 3 corresponding to _B ~ 6 _B (The non-signal portion 1 in the circulating shift register 18). _B , 2 _B Since the influence of the influence is not received by the signal charges used in the distance measurement calculation because it is adjacent to the object, it is possible to obtain an accurate distance to the subject by ignoring the influence during the distance measurement calculation.
[0065]
【The invention's effect】
As described above, according to the present invention, a plurality of charge channels arranged in a ring and a cyclic shift register are provided, and when performing a distance measurement operation, adjacent to a no-signal portion generated in the charge transfer channel. Since the signal charge existing in at least one of the charge transfer channels is ignored, and the number of accumulations of the signal charge in the cyclic shift register is increased, the number of charge transfer channels corresponding to the charge signal to be ignored is increased. Even if the non-signal portion occurs, the position of the received light image can be obtained as accurately as possible, and the distance measurement can be performed with high accuracy.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a main part of a distance measuring apparatus according to a first embodiment of the present invention.
FIG. 2 is a time chart for explaining an operation sequence of the distance measuring apparatus according to the first embodiment of the present invention.
FIG. 3 is a time chart for explaining an operation sequence of the distance measuring apparatus according to the first embodiment of the present invention.
FIG. 4 is a time chart for explaining an operation sequence of the distance measuring apparatus according to the first embodiment of the present invention.
FIG. 5 is a diagram illustrating an example in which the distance measuring apparatus according to the first embodiment of the present invention is applied to an AF apparatus of a camera.
FIG. 6 is a schematic diagram illustrating a main part of the distance measuring apparatus according to the first embodiment of the present invention.
FIG. 7 is a schematic diagram illustrating a main part of the distance measuring apparatus according to the first embodiment of the present invention.
FIG. 8 is a diagram for explaining the operation of the distance measuring apparatus according to the first embodiment of the present invention.
FIG. 9 is a diagram for explaining the operation of the distance measuring apparatus according to the first embodiment of the present invention.
FIG. 10 is a diagram for explaining a problem of a conventional distance measuring device.
[Explanation of symbols]
11 Charge distribution of charge transfer channel in one accumulation
2 Charge distribution of charge transfer channel when accumulated 10 times with transfer efficiency of 100%
3 Charge distribution of the charge transfer channel when accumulated 10 times with a transfer efficiency of 99.5%
4 Reception image reproduced from power distribution on sensor array when accumulated 10 times with transfer efficiency of 100%
5 Reception image reproduced from power distribution on sensor array when accumulated 10 times at 99.5% transfer efficiency
6. False reception image
7 Light reception image when signal charge of pixel with false light reception image is ignored
11 Sensor array
12 Integrator
13 Clear part
14 First storage unit
15 Second storage unit
16 Shift section
17 linear CCD (signal charge injection means)
18 Circular shift register
101 output amplifier
102 Floating gate electrode
201 IRED
202 IRED drive circuit
203 drive pulse
204 A / D converter
206 AF processing circuit
207 Floodlight lens
208 Receiving lens
210 CPU
211 memory
221 subject
222 Reception image on sensor array

Claims (4)

A distance measuring device that repeatedly emits a pulsed light beam to an object to be measured, receives reflected light thereof, and performs triangulation.
Light emitting means for emitting light to the object to be measured,
A plurality of photoelectric conversion elements that receive reflected light from the object to be measured and perform photoelectric conversion.
Signal charge supply means for integrating and transferring the signal charge output from the photoelectric conversion element,
Signal charge injecting means having a plurality of charge transfer channels and transferring signal charges supplied from the signal charge supplying means in one direction;
A cyclic shift register in which a plurality of charge transfer channels are arranged in a ring shape and signal charges injected from the signal charge supply means via the signal charge injection means are accumulated while being circulated;
Calculating means for calculating a distance by ignoring signal charges existing in at least one of the charge transfer channels adjacent to a non-signal portion generated in the charge transfer channel of the cyclic shift register;
With
A distance measuring apparatus, wherein the arithmetic means increases the number of charge transfer channels corresponding to a charge signal to be ignored as the number of times of accumulation of the signal charge in the cyclic shift register increases. 2. The distance measuring apparatus according to claim 1, wherein the number of the charge transfer channels of the signal charge injection means is larger than the number of the charge transfer channels of the cyclic shift register. The distance measuring device according to claim 1, wherein a transfer electrode to which a charge transfer pulse is applied is provided on the charge transfer channel via a gate insulating film. The floating gate electrode section for detecting the amount of transferred signal charges is provided on at least one of the charge transfer channels of the cyclic shift register via a gate insulating film. 4. The distance measuring device according to any one of 3.

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