JP2002098525A - Range finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase an accuracy of range measurement in the case that an object to be measured has a small reflective index and the range from the object to be measured is great, by measuring the range while lowering a level of clamp signal on the basis of inferring the case. SOLUTION: The clamp signal is set to a large level, and a first measurement is curried out. In the case that the range value of the first measurement is not less than a determined range value, the clamp signal is set to a small level, and a second measurement is curried out (e.g. S56). Then, the range value D2 of the second measurement is judged whether it is larger than a set value B or not (e.g. S60). In the case that the range value D2 is larger than the set value, the clamp signal is set to the large level (e.g. S64), and a third measurement is curried out (e.g. S68). In the other case that the range value D2 of the second measurement is not larger than the set value B in the step S60, the clamp signal is set to the small level under a constant condition (e.g. S82), and the third measurement is carried out (e.g. S86).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device for measuring a distance to an object to be measured, and more particularly to an active distance measuring device suitably used for a camera or the like.

[0002]

2. Description of the Related Art An active type distance measuring device used for a camera or the like is an infrared light emitting diode (hereinafter, "IRED").
That. ) Is projected toward the object to be measured, and reflected light of the projected light flux is detected by a position detecting element (hereinafter, referred to as “PS”).
D ". ), The signal output from the PSD is subjected to arithmetic processing by a signal processing circuit and an arithmetic circuit and output as distance information, and the CPU detects the distance to the object to be measured. In addition, since errors may occur in distance measurement using only one light projection, light projection is performed a plurality of times to obtain a plurality of distance information, and the plurality of distance information is integrated by an integration circuit and averaged. Is common.

Conventionally, as such active type distance measuring devices, Japanese Patent Application Laid-Open Nos. 8-94919 and 8-9 have been disclosed.
What is described in 4920 gazette is known. FIG.
FIG. 2 shows a configuration diagram of a distance measuring device described in these publications as a distance measuring device according to a first related art.

In the distance measuring device shown in FIG.
The driver 112 drives the IRED 114 to output infrared light under the control of, and emits the infrared light to an object to be measured via a light projection lens (not shown). The infrared light reflected by the object to be measured is focused on a PSD 116 via a light receiving lens (not shown), and the PSD 116 outputs two signals I1 and I2 according to the position where the reflected light of the infrared light is received. Is output. The first signal processing circuit 118 outputs the signal I
The second signal processing circuit 120 removes the stationary light component that becomes the noise contained in the signal I2, and removes the stationary light component that becomes the noise contained in the signal I2.

The arithmetic circuit 132 outputs an output ratio (I1 / (I1) based on the signals I1 and I2 from which the stationary light component has been removed.
1 + I2)) is calculated, and an output ratio signal corresponding to the distance to the object to be measured is output. The integrating circuit 134 improves the S / N ratio by integrating the output ratio signal output from the arithmetic circuit 132 many times in this manner. This integration circuit 1
34 (hereinafter referred to as “AF signal”).
Is based on the distance to the object to be measured. Then, CPU 110 outputs A
Based on the F signal, a predetermined calculation is performed to obtain a distance signal, and based on the distance signal, the lens driving circuit 136 is controlled to move the lens 138 to a focus position.

FIG. 23 is a diagram showing the relationship between the AF signal output from the integration circuit 134 of the first prior art and the distance to the object to be measured. In the graph shown in this figure, the horizontal axis is the reciprocal (1 / L) of the distance L to the object to be measured.
The vertical axis represents the output ratio (I1 / (I1 + I2)), that is, the AF signal. As shown in this figure, a certain distance L
4 and below, the output ratio is substantially linear with respect to the reciprocal (1 / L) of the distance L, and the distance L is large (1 / L is small).
Then, the output ratio decreases. However, when the distance L is longer than the distance L4, the influence of the noise component becomes larger as the distance L increases. Assuming that the noise component is In (In ≧ 0), the output ratio is (I1 + In) / (I1 + In + I2 + In), and the output ratio fluctuates in a direction of increasing (i.e., the direction of the output ratio 50%) beyond the distance L4. . Moreover, since In occurs randomly, it becomes unstable depending on the distance measurement conditions.
This is because as the distance L increases, the intensity of the reflected light received by the PSD 116 decreases and the noise component In relatively increases. When this happens,
The distance L to the object to be measured cannot be uniquely determined from the output ratio.

Therefore, as shown in FIG. 24, when the far-side signal I2 outputted from the second signal processing circuit 120 is smaller than the clamp signal Ic, the clamp circuit 130 for outputting the clamp signal Ic is connected to the second signal processing circuit. It is provided between 120 and the arithmetic circuit 132. However, even in that case, as shown in FIG. 27 described later, the distance output is fixed to a certain distance on the long distance side, and the deviation from the design value increases.

The following is known as a distance measuring device for solving such a problem. FIG.
FIG. 2 is a configuration diagram of a distance measuring apparatus according to a second related art. In this figure, only the light receiving side is shown. In the distance measuring apparatus shown in this figure, the signals I1 and I2 output from the PSD 140 are applied to the stationary light removing circuits 142 and 14 respectively.
After the steady light component is removed by each of the four, the signals are input to both the arithmetic circuits 146 and 148. Arithmetic circuit 146
Performs an operation of I1 / (I1 + I2) on the basis of the signals I1 and I2 from which the stationary light component has been removed to obtain an output ratio, and the integrating circuit 150 integrates the output ratio. on the other hand,
The arithmetic circuit 148 calculates I1 + I2 to obtain the light amount, and the integrating circuit 152 integrates the light amount. Then, the selection unit 160 selects one of the output ratio and the light amount, and obtains the distance to the distance measurement target based on the selection. The selection unit 160 is a process in the CPU.

FIG. 26 is a configuration diagram of a distance measuring apparatus according to a third prior art. In this figure, only the light receiving side is shown. In the distance measuring device shown in FIG.
After the steady light components are removed by the steady light removing circuits 172 and 174, respectively, the signals I1 and I2 output from are input to one end of the switch 176. The switch 176 is controlled by the CPU, and causes one of the outputs of the steady light removing circuits 172 and 174 to be input to the integrating circuit 178. An integrating circuit 178 integrates either one of the input signals I1 and I2, and a calculating section 180 calculates I1 / (I1 +
I2) is calculated to obtain the output ratio.
In step 82, the calculation of I1 + I2 is performed to obtain the light amount. Then, the selection unit 184 selects one of the output ratio and the light amount, and obtains the distance to the distance measurement target based on the selected one.
Note that the operation units 180 and 182 and the selection unit 184
This is processing in the PU.

The distance measuring devices (FIGS. 25 and 26) according to the second and third prior arts both have an output ratio (I1 / (I1 + I2) when the distance L to the object to be measured is small.
)), And when the distance L is large, the distance L is calculated based on the light amount (I1 + I2). By doing so, the distance L can be uniquely determined. Things.

[0011]

As described above, the distance measuring devices according to the second and third prior arts (FIGS. 25 and 26)
Can solve the problems of the distance measuring apparatus (FIGS. 22 and 24) according to the first conventional technique. However, the distance measuring apparatus according to the second prior art (FIG. 25) needs to provide two sets of the arithmetic circuit and the integrating circuit.
As compared with the conventional distance measuring apparatus (FIGS. 22 and 24), there is a problem that the circuit scale is increased and the cost is increased. On the other hand, the distance measuring apparatus according to the third prior art (FIG. 26) has a smaller
Since the signals I1 and I2 cannot be detected simultaneously, the distance measuring apparatus according to the second prior art (FIG.
If the distance L is to be obtained with the same S / N ratio as in 5), 2
It takes twice as long.

Further, any of the distance measuring apparatuses according to the prior arts described above are designed to operate favorably when the reflectance of the object to be measured (subject) to the infrared light output from the IRED is a standard value. However, when the reflectance of the object to be measured is small, the values of the signals I1 and I2 output from the PSD become small, and an accurate measured value may not be obtained.
This problem is particularly serious when the distance to the object to be measured is large. This will be described with reference to the calculation results shown in FIGS.

FIG. 27 is a graph showing the relationship between the distance signal and the distance obtained by the distance measuring apparatus according to the first prior art when the reflectance of the object to be measured is 36% of the standard value. . FIG. 28 is a graph showing the relationship between the distance signal and the distance obtained by the distance measuring device according to the first conventional technique when the reflectance of the object to be measured is low at 9%. FIG.
11 is a graph showing a relationship between a distance signal and a distance obtained by a distance measuring device according to each of the second and third conventional techniques when the reflectance of the object to be measured is 36% of a standard value.
FIG. 30 is a graph showing the relationship between the distance signal and the distance obtained by the distance measuring device according to each of the second and third conventional techniques when the reflectance of the object to be measured is low at 9%. is there. In these figures, two parallel parts are shown.
The broken line indicates the allowable range of the ranging error.

A distance measuring apparatus according to the first prior art (FIG. 24)
Then, as shown in FIG. 27, when the reflectance of the object to be measured is 36% of the standard value, the distance signal always falls within the allowable range of the ranging error, but barely falls within the allowable range depending on the distance. ing. On the other hand, as shown in FIG. 28, when the reflectance of the object to be measured is 9%, which is low, the distance signal may be out of the allowable range of the ranging error depending on the distance. In the ranging devices according to the second and third prior arts, as shown in FIG. 29, when the reflectance of the ranging object is 36% of the standard value, the distance signal falls within the allowable range of the ranging error. Always on, which is an improvement over that shown in FIG. On the other hand, as shown in FIG. 30, when the reflectivity of the object to be measured is low at 9%, the distance signal may be out of the allowable range of the distance measurement error depending on the distance, as shown in FIG. Is the same as

As described above, when the reflectance of the object to be measured is low, the distance signal may be out of the allowable range of the ranging error depending on the distance, and the ranging accuracy may be deteriorated. Therefore,
In order to solve such a problem, in the distance measuring apparatus according to the first prior art (FIG. 24), the second signal processing circuit 1 is used.
When the far-side signal I2 outputted from the signal 20 is smaller than the clamp signal Ic, a clamp circuit for outputting the clamp signal Ic is provided between the second signal processing circuit 120 and the arithmetic circuit 132 to reduce the level of the clamp signal Ic. It is possible to do.

FIG. 31 shows a case where the level of the clamp signal Ic is reduced and the reflectivity of the object to be measured is 36% of the standard value, which is obtained by the first prior art distance measuring apparatus. 6 is a graph showing a relationship between a distance signal and a distance. FIG. 32 shows a distance signal obtained by the distance measuring apparatus according to the first prior art when the level of the clamp signal Ic is reduced and the reflectance of the object to be measured is 9%, which is low. 6 is a graph showing a relationship between the distance and the distance. FIG.
As shown in FIG. 1, the level of the clamp signal Ic is small,
When the reflectivity of the object to be measured is a standard value, the distance signal always falls within the allowable range of the distance measurement error, and this is improved as compared with that shown in FIG. on the other hand,
As shown in FIG. 32, when the level of the clamp signal Ic is low and the reflectance of the object to be measured is low, the distance signal is within the allowable range of the distance measurement error, though it is barely within the allowable range depending on the distance. ing.

However, even if the level of the clamp signal Ic is reduced, the following problem still arises when the external light luminance is relatively large. FIG. 33 shows the first case where the level of the clamp signal Ic is reduced and the external light luminance is large and the reflectance of the object to be measured is 36% of the standard value.
6 is a graph showing a relationship between a distance signal and a distance obtained by a distance measuring device according to the related art. FIG. 34 shows the first conventional distance measurement when the level of the clamp signal Ic is reduced and the external light luminance is high and the reflectance of the object to be measured is low at 9%. 5 is a graph showing a relationship between a distance signal obtained by the device and a distance. As shown in these figures, when the external light luminance is large, the allowable range of the distance measurement error is wide, but nevertheless, even when the reflectance of the distance measurement target is a standard value or low, Depending on the distance, the distance signal may be out of the allowable range of the ranging error, and the ranging accuracy may be deteriorated. This is because when the external light luminance is large, the first signal processing circuit 118 and the second signal processing circuit 1
This is because the stationary light is not sufficiently removed in each of the lenses 20 and a distance measurement error occurs due to this.

In order to solve the above problems, an IR
It is conceivable to increase the amount of light projected from the ED or to increase the diameter of the light projecting lens or the light receiving lens. FIG.
Reference numeral 5 denotes a distance obtained by the distance measuring apparatus according to the first conventional technique when the light projection amount from the IRED is quadrupled and the reflectance of the distance measuring object is 36% of a standard value. It is a graph which shows the relationship between a signal and distance. FIG.
When the amount of light projected from the RED is quadrupled, and when the reflectance of the object to be measured is 9%, which is low, the distance signal and the distance obtained by the distance measuring apparatus according to the first related art are used. It is a graph which shows a relationship. As shown in these figures, the distance signal always falls within the allowable range of the ranging error regardless of whether the reflectance of the ranging object is a standard value or low. However, IRED
Increasing the amount of light projected from the lens increases costs, and increasing the diameter of the light projecting lens and the light receiving lens increases the size.

Therefore, the present invention has been made to solve the above problem, and even when the reflectance of the object to be measured is small and the distance to the object to be measured is large, the distance can be accurately determined. It is an object of the present invention to provide a distance measuring device which can be obtained and does not increase cost and size.

[0020]

Means for Solving the Problems [1] One aspect of the side distance device according to the present invention is a light projecting means for projecting a light beam toward an object to be measured, and a light projecting onto the object to be measured. The reflected light of the luminous flux is received at a light receiving position on a position detection element corresponding to the distance to the distance measurement target, and based on the light receiving position, if the received light amount is constant, the longer the distance, the greater the distance. A light-receiving unit that outputs a far-side signal that is a large value and a near-side signal that is a larger value as the distance is shorter if the amount of received light is constant,
The far-side signal is input and compared with the level of the clamp signal. If the level of the far-side signal is equal to or higher than the level of the clamp signal, the far-side signal is output. A calculating means for calculating a ratio between the near side signal and the signal output from the clamping means to output an output ratio signal; integrating the output ratio signal to integrate the output ratio signal; Integrating means for outputting an integrated signal according to the result; controlling the projection of the light beam in the light projecting means, the level of the clamp signal in the clamping means, and the total sum of the integration period of the output ratio signal in the integrating means. And control means for detecting a distance measurement value based on the integration signal output from the integration means, wherein the control means comprises:
The clamp signal is set to a first level, the sum of the integration period of the output ratio signal in the integration means is set to a first number, and a first sum is set based on the integration signal output from the integration means. Detecting a distance measurement value, and (b) when the first distance measurement value is a value on the far side that is equal to or longer than a first set distance, the clamp signal is set to a second level smaller than the first level. Setting the sum of the integration periods of the output ratio signal in the integration means to a second number, detecting a second distance measurement value based on the integration signal output from the integration means, and (c) Or) when the second distance value is a value closer to the second set distance, or when the second distance value is not a value closer to the second set distance, and When a value obtained by subtracting the first distance measurement value from the distance measurement value is smaller than a first set value, Set No. to the first level,
The sum of the integration periods of the output ratio signal in the integration means is set to a third number, and a third distance measurement value is detected based on the integration signal output from the integration means. Calculating a distance to the object to be measured based on a sum of the distance value and the third distance measurement value; and (d) determining that the second distance measurement value is the second distance measurement value.
When the clamp signal is not closer to the set distance and the value obtained by subtracting the first measured value from the second measured value is not smaller than the first set value, the clamp signal is set to the second set value. Level, the sum of the integration periods of the output ratio signal in the integration means is set to a third number, and a third ranging value is detected based on the integration signal output from the integration means, The distance to the distance measurement target is calculated based on the sum of the second distance measurement value and the third distance measurement value.

Note that the first number, the second number, and the third number may be the same or different.

According to this aspect, when the external light luminance is relatively high and the reflectivity of the object to be measured is large, even if the second distance measurement value is detected as a near value, the second distance measurement value is detected. Is smaller than the second set distance, the clamp signal is set to the first high level, a third distance value is detected, and the first and second distance values are detected. The distance to the distance measurement target is calculated based on the sum of the third distance measurement values. For this reason, the distance to the object to be measured can be accurately detected.

[2] Another aspect of the side distance device according to the present invention is a light projecting means for projecting a light beam toward a distance measuring object, and a reflection of the light beam projected on the distance measuring object. The light is received at a light receiving position on the position detecting element corresponding to the distance to the object to be measured, and based on the light receiving position, if the received light amount is constant, the far side increases as the distance increases. Signals,
If the amount of received light is constant, a light receiving means for outputting a near side signal having a larger value as the distance becomes shorter, and a level of the far side signal is inputted and compared with the level of a clamp signal, and the level of the far side signal is obtained. Is greater than or equal to the level of the clamp signal, and outputs the far-side signal; otherwise, the clamp means for outputting the clamp signal, and the ratio between the near-side signal and the signal output from the clamp means. And an output means for outputting an output ratio signal; an integrating means for integrating and integrating the output ratio signal; and outputting an integrated signal according to the integration result; and projecting the light beam in the light projecting means. Controlling the level of the clamp signal in the clamp means and the sum of the integration period of the output ratio signal in the integration means, and controlling the level of the integration signal output from the integration means. Control means for detecting a distance measurement value based on the following formula: (a) setting the clamp signal to a first level, and calculating the sum of integration periods of the output ratio signal in the integration means. Detecting a first distance measurement value based on the integration signal output from the integration means while setting the first distance measurement value to a first number, and (b) detecting the first distance measurement value which is equal to or greater than a first set distance. And setting the clamp signal to a second level smaller than the first level, and setting the sum of the integration period of the output ratio signal in the integration means to a second number. A second ranging value is detected based on the integration signal output from the integrating means, and (c) a value obtained by subtracting the first ranging value from the second ranging value is a first set value. When the value is smaller than the first value or when the first distance value is subtracted from the second distance value, The clamp signal is set to the first level when the second distance measurement value is not smaller than a fixed value and the second distance measurement value is a value farther than a third set distance, and the output ratio signal of the integration means is set. The sum of the integration periods is set to a third number, a third distance value is detected based on the integration signal output from the integration means, and the first distance value and the third distance value are detected. Calculating the distance to the object to be measured based on the sum of the values; (d) a value obtained by subtracting the first distance value from the second distance value is not smaller than a first set value; When the second distance value is not a value farther than the third set distance, the clamp signal is set to the second level, and the sum of the integration period of the output ratio signal in the integrating means is set to the second level. A third distance measurement value is detected based on the integration signal output from the integration means by setting the number to three. Then, the distance to the distance measurement target is calculated based on the sum of the second distance measurement value and the third distance measurement value.

Note that the first number, the second number, and the third number may be the same or different.

According to this other aspect, even when the value obtained by subtracting the first distance measurement value from the second distance measurement value is not smaller than the first set value, the second distance measurement value becomes the third distance measurement value. If the value is farther than the set distance, the clamp signal is set to the first level, a third distance value is detected, and measurement is performed based on the sum of the first distance value and the third distance value. The distance to the distance target is calculated. Therefore, when the reflectance of the object to be measured is approximately equal to the reference reflectance, the clamp signal is set to the first level and the third distance measurement value is detected. It is prevented from being detected as a value closer to the design value. For this reason, the distance to the object to be measured can be accurately detected.

[3] Still another aspect of the side-distance device according to the present invention is a light-emitting unit that emits a light beam toward the object to be measured, and a light-emitting unit that projects the light beam onto the object to be measured. Reflected light,
Receives light at a light receiving position on the position detecting element according to the distance to the distance measurement target, based on the light receiving position, if the received light amount is constant, a far side signal that is larger as the distance is longer, If the amount of received light is constant, a light receiving means for outputting a near side signal having a larger value as the distance becomes shorter, and a level of the far side signal is inputted and compared with the level of a clamp signal, and the level of the far side signal is obtained. Is greater than or equal to the level of the clamp signal, and outputs the far-side signal; otherwise, the clamp means for outputting the clamp signal, and the ratio between the near-side signal and the signal output from the clamp means. And an output means for outputting an output ratio signal; an integrating means for integrating and integrating the output ratio signal; and outputting an integrated signal according to the integration result; and projecting the light beam in the light projecting means. , The clamp Control means for controlling a level of the clamp signal in a stage and a sum of integration periods of the output ratio signal in the integration means, and detecting a distance measurement value based on the integration signal output from the integration means; Wherein the control means (a) sets the clamp signal to a first level, sets the sum of the integration period of the output ratio signal in the integration means to a first number, and outputs the sum from the integration means. Detecting a first distance value based on the integrated signal thus obtained, and (b) determining the first distance value as a first distance value.
When the value is on the far side of the set distance or more, the clamp signal is set to a second level smaller than the first level, and the sum of the integration period of the output ratio signal in the integration means is set to the second level. (C) detecting a second distance measurement value based on the integration signal output from the integration means while setting the number to a number;
The sum of the first distance measurement value and the first distance measurement value is not larger than a second set value or a value obtained by subtracting the first distance measurement value from the second distance measurement value is a third value. Setting the clamp signal to the first level when the value is not larger than a set value and a value obtained by subtracting the first distance value from the second distance value is smaller than a first set value; Setting the sum of the integration period of the output ratio signal in the integration means to a third number, detecting a third distance value based on the integration signal output from the integration means, Calculating a distance to the distance measurement target based on a sum of the distance measurement value and the third distance measurement value;
(D) the sum of the first distance measurement value and the first distance measurement value is a second
Is larger than the set value of the second distance measurement value and the first
When the value obtained by subtracting the distance measurement value is larger than the third set value,
Alternatively, the sum of the first distance measurement value and the first distance measurement value is a second distance measurement value.
Or a value obtained by subtracting the first distance measurement value from the second distance measurement value is not larger than a third value and the first distance measurement value is not larger than the second distance measurement value. When the value obtained by subtracting the distance measurement value is not smaller than the first set value, the clamp signal is set to the second level, and the sum of the integration period of the output ratio signal in the integration means is set to a third number. And a third distance measurement value is detected based on the integration signal output from the integration means, and the distance measurement is performed based on a sum of the second distance measurement value and the third distance measurement value. Calculate the distance to the object.

Note that the first number, the second number, and the third number may be the same or different.

According to this, the sum of the first distance measurement value and the first distance measurement value is larger than the second set value, and a value obtained by subtracting the first distance measurement value from the second distance measurement value is obtained. When the value is larger than the third set value, the clamp signal is set to the second level to detect the third distance value, and the distance measurement target is determined based on the sum of the second distance value and the third distance value. Calculate the distance to the object. For this reason, when the reflectance of the object to be measured is small, the clamp signal is set to the first level and the third measured value is detected, so that the third measured value is on the far side from the design value. Detection as a value is reduced. For this reason, the distance to the object to be measured can be accurately detected.

[4] Still another aspect of the side-distance device according to the present invention is a light-emitting unit that emits a light beam toward a distance-measuring object, and a light-emitting device that projects the light beam onto the distance-measuring object. Reflected light,
Receives light at a light receiving position on the position detecting element according to the distance to the distance measurement target, based on the light receiving position, if the received light amount is constant, a far side signal that is larger as the distance is longer, If the amount of received light is constant, a light receiving means for outputting a near side signal having a larger value as the distance becomes shorter, and a level of the far side signal is inputted and compared with the level of a clamp signal, and the level of the far side signal is obtained. Is greater than or equal to the level of the clamp signal, and outputs the far-side signal; otherwise, the clamp means for outputting the clamp signal, and the ratio between the near-side signal and the signal output from the clamp means. And an output means for outputting an output ratio signal; an integrating means for integrating and integrating the output ratio signal; and outputting an integrated signal according to the integration result; and projecting the light beam in the light projecting means. , The clamp Control means for controlling a level of the clamp signal in a stage and a sum of integration periods of the output ratio signal in the integration means, and detecting a distance measurement value based on the integration signal output from the integration means; Wherein the control means (a) sets the clamp signal to a first level, sets the sum of the integration period of the output ratio signal in the integration means to a first number, and outputs the sum from the integration means. Detecting a first distance value based on the integrated signal thus obtained, and (b) determining the first distance value as a first distance value.
When the value is on the far side of the set distance or more, the clamp signal is set to a second level smaller than the first level, and the sum of the integration period of the output ratio signal in the integration means is set to the second level. (C) detecting a second distance measurement value based on the integration signal output from the integration means while setting the number to a number;
The sum of the first distance value and the second distance value is not larger than a second set value or a value obtained by subtracting the first distance value from the second distance value is a third value. Setting the clamp signal to the first level when the value is not larger than a set value and a value obtained by subtracting the first distance value from the second distance value is smaller than a first set value; Setting the sum of the integration period of the output ratio signal in the integration means to a third number, detecting a third distance value based on the integration signal output from the integration means, Calculating a distance to the distance measurement target based on a sum of the distance measurement value and the third distance measurement value;
(D) the sum of the first distance measurement value and the second distance measurement value is a second
Is larger than the set value of the second distance measurement value and the first
When the value obtained by subtracting the distance measurement value is larger than the third set value,
Alternatively, the sum of the first distance measurement value and the second distance measurement value is a second distance measurement value.
Or a value obtained by subtracting the first distance measurement value from the second distance measurement value is not larger than a third value and the first distance measurement value is not larger than the second distance measurement value. When the value obtained by subtracting the distance measurement value is not smaller than the first set value, the clamp signal is set to the second level, and the sum of the integration period of the output ratio signal in the integration means is set to a third number. And a third distance measurement value is detected based on the integration signal output from the integration means, and the distance measurement is performed based on a sum of the second distance measurement value and the third distance measurement value. Calculate the distance to the object.

The first number, the second number, and the third number may be the same or different.

According to this, the sum of the first distance measurement value and the first distance measurement value is larger than the second set value and the value obtained by subtracting the first distance measurement value from the second distance measurement value is When the value is larger than the third set value, the clamp signal is set to the second level, a third distance value is detected, and the distance measurement target is determined based on the sum of the second distance value and the third distance value. Calculate the distance to the object. For this reason, when the reflectance of the object to be measured is small, the clamp signal is set to the first level and the third measured value is detected, so that the third measured value is on the far side from the design value. Detection as a value is reduced. For this reason, the distance to the object to be measured can be accurately detected.

[5] Still another aspect of the side distance device according to the present invention is a light projecting means for projecting a light beam toward the object to be measured, and a light source for projecting the light beam onto the object to be measured. Reflected light,
Receives light at a light receiving position on the position detecting element according to the distance to the distance measurement target, based on the light receiving position, if the received light amount is constant, a far side signal that is larger as the distance is longer, If the amount of received light is constant, a light receiving means for outputting a near side signal having a larger value as the distance becomes shorter, and a level of the far side signal is inputted and compared with the level of a clamp signal, and the level of the far side signal is obtained. Is greater than or equal to the level of the clamp signal, and outputs the far-side signal; otherwise, the clamp means for outputting the clamp signal, and the ratio between the near-side signal and the signal output from the clamp means. And an output means for outputting an output ratio signal; an integrating means for integrating and integrating the output ratio signal; and outputting an integrated signal according to the integration result; and projecting the light beam in the light projecting means. , The clamp Control means for controlling a level of the clamp signal in a stage and a sum of integration periods of the output ratio signal in the integration means, and detecting a distance measurement value based on the integration signal output from the integration means; Wherein the control means (a) sets the clamp signal to a first level, sets the sum of the integration period of the output ratio signal in the integration means to a first number, and outputs the sum from the integration means. Detecting a first distance value based on the integrated signal thus obtained, and (b) determining the first distance value as a first distance value.
When the value is on the far side of the set distance or more, the clamp signal is set to a second level smaller than the first level, and the sum of the integration period of the output ratio signal in the integration means is set to the second level. (C) detecting a second distance measurement value based on the integration signal output from the integration means while setting the number to a number;
The sum of the second distance value and the second distance value is not larger than a second set value or a value obtained by subtracting the first distance value from the second distance value is a third value. Setting the clamp signal to the first level when the value is not larger than a set value and a value obtained by subtracting the first distance value from the second distance value is smaller than a first set value; Setting the sum of the integration period of the output ratio signal in the integration means to a third number, detecting a third distance value based on the integration signal output from the integration means, Calculating a distance to the distance measurement target based on a sum of the distance measurement value and the third distance measurement value;
(D) the sum of the second distance measurement value and the second distance measurement value is the second
Is larger than the set value of the second distance measurement value and the first
When the value obtained by subtracting the distance measurement value is larger than the third set value,
Alternatively, the sum of the second distance measurement value and the second distance measurement value is the second distance measurement value.
Or a value obtained by subtracting the first distance measurement value from the second distance measurement value is not larger than a third value and the first distance measurement value is not larger than the second distance measurement value. When the value obtained by subtracting the distance measurement value is not smaller than the first set value, the clamp signal is set to the second level, and the sum of the integration period of the output ratio signal in the integration means is set to a third number. And a third distance measurement value is detected based on the integration signal output from the integration means, and the distance measurement is performed based on a sum of the second distance measurement value and the third distance measurement value. Calculate the distance to the object.

The first number, the second number, and the third number may be the same or different.

According to this, the sum of the first distance measurement value and the first distance measurement value is larger than the second set value and the value obtained by subtracting the first distance measurement value from the second distance measurement value is When the value is larger than the third set value, the clamp signal is set to the second level, a third distance value is detected, and the distance measurement target is determined based on the sum of the second distance value and the third distance value. Calculate the distance to the object. For this reason, when the reflectance of the object to be measured is small, the clamp signal is set to the first level and the third measured value is detected, so that the third measured value is on the far side from the design value. Detection as a value is reduced. For this reason, the distance to the object to be measured can be accurately detected.

[6] Still another aspect of the side-distance device according to the present invention is a light-emitting unit that emits a light beam toward the object to be measured, and a light-emitting unit that projects the light beam onto the object to be measured. Reflected light,
Receives light at a light receiving position on the position detection element according to the distance to the distance measurement target, and based on the light receiving position, if the received light amount is constant, a far side signal that has a larger value as the distance increases, If the amount of received light is constant, a light receiving means for outputting a near side signal which has a larger value as the distance is shorter, and a level of the far side signal which is inputted and compared with the level of a clamp signal, and the level of the far side signal Is greater than or equal to the level of the clamp signal, and outputs the far-side signal; otherwise, the clamp means for outputting the clamp signal, and the ratio of the near-side signal to the signal output from the clamp means. And an output means for outputting an output ratio signal; an integration means for integrating the output ratio signal into an integration capacitor for integration; and outputting an integration signal according to the integration result; Throw Controlling the level of the clamp signal in the clamp means and the sum of the integration period of the output ratio signal in the integration means, and detecting a distance measurement value based on the integration signal output from the integration means. Means; (a) setting the clamp signal to a first level;
(B) detecting a first distance measurement value based on the integration signal output from the integration means by setting a sum of integration periods of the output ratio signal in the integration means to a first number; The signal is set to a second level, and the sum of the integration period of the output ratio signal in the integration means is set to a second number smaller than the first number, and the integration signal output from the integration means is set to the second number. Detecting a second distance value based on the
(C) adding a predetermined value to the second distance measurement value to obtain the second distance measurement value;
Is calculated, and the distance to the object to be measured is calculated based on the sum of the first measured value and the corrected second measured value.

In still another aspect, the second level of the clamp signal in the detection of the second distance value is the first level of the clamp signal in the detection of the first distance value. Is preferably the same as or smaller than

[7] Still another aspect of the side-distance device according to the present invention is a light-emitting device that emits a light beam toward a distance-measuring object, Reflected light,
Receives light at a light receiving position on the position detection element according to the distance to the distance measurement target, and based on the light receiving position, if the received light amount is constant, a far side signal that has a larger value as the distance increases, If the amount of received light is constant, a light receiving means for outputting a near side signal which has a larger value as the distance is shorter, and a level of the far side signal which is inputted and compared with the level of a clamp signal, and the level of the far side signal Is greater than or equal to the level of the clamp signal, and outputs the far-side signal; otherwise, the clamp means for outputting the clamp signal, and the ratio of the near-side signal to the signal output from the clamp means. And an output means for outputting an output ratio signal; an integration means for integrating the output ratio signal into an integration capacitor for integration; and outputting an integration signal according to the integration result; Throw Controlling the level of the clamp signal in the clamp means and the sum of the integration period of the output ratio signal in the integration means, and detecting a distance measurement value based on the integration signal output from the integration means. Means; (a) setting the clamp signal to a first level;
(B) detecting a first distance measurement value based on the integration signal output from the integration means by setting a sum of integration periods of the output ratio signal in the integration means to a first number; The signal is set to a second level, and the sum of the integration period of the output ratio signal in the integration means is set to a second number smaller than the first number, and the integration signal output from the integration means is set to the second number. Detecting a second distance value based on the
(C) adding a predetermined value to the second distance measurement value to obtain the second distance measurement value;
(D) setting the clamp signal to a third level, and setting the sum of the integration periods of the output ratio signal in the integration means to a third number smaller than the first number Detecting a third distance measurement value based on the integration signal output from the integration means, and (e) adding a predetermined value to the third distance measurement value to obtain the third distance measurement value. And (f)
The distance measurement is performed based on a sum of the first distance measurement value and the corrected second distance measurement value or based on a sum of the second distance measurement value and the corrected third distance measurement value. Calculate the distance to the object.

In this case, it is desirable that the second number and the third number be the same.

In still another aspect, the second level of the clamp signal in the detection of the second distance value is the first level of the clamp signal in the detection of the first distance value. And the third level of the clamp signal in the detection of the third distance value is the same as or smaller than the first level of the clamp signal in the detection of the first distance value. Small is preferred.

In another aspect, the predetermined value added for correcting the second distance measurement value and the predetermined value added for correcting the third distance measurement value are different from each other. Are preferably the same.

According to these, when the distance measurement is performed continuously and the distance to the object to be measured is detected based on a plurality of distance measurement values, the integration processing of the first distance measurement value detection and the second measurement are performed. In the integration process of the distance value detection, a change occurs in the characteristics of the integration capacitor. Is corrected by adding the value of the second distance measurement value, it is possible to correct a change in the second distance measurement value due to a change in the characteristic of the integration capacitor. For this reason, the distance to the object to be measured can be accurately detected.

[0042]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description. Hereinafter, a case will be described in which the active distance measuring apparatus according to the present embodiment is applied as a distance measuring apparatus of an automatic focusing camera.

(First Embodiment) First, the overall configuration of the distance measuring apparatus according to the present embodiment will be described. FIG. 1 is a configuration diagram of a distance measuring apparatus according to the present embodiment.

The CPU 1 controls the entire camera including the distance measuring device, and controls the entire camera including the distance measuring device based on programs and parameters stored in the EEPROM 2 in advance. In the distance measuring apparatus shown in this figure, the CPU 1 controls the driver 3 to control the emission of infrared light from the IRED (infrared light emitting diode) 4. Also, the CPU 1 is an auto-focus IC
(Hereinafter referred to as “AFIC”) While controlling the operation of 10, an AF signal output from AFIC 10 is input. Further, the CPU 1 inputs the value of the external light luminance measured by the photometric sensor 71.

In particular, the CPU 1 according to the present embodiment is characterized by including a control unit 1A. This control unit 1A
Controls the level of the clamp signal in the clamp circuit 13 and the total sum of the integration period of the output ratio signal in the integration circuit 15, and detects a distance measurement value based on the integration signal output from the integration circuit 15. Then, the control unit 1A performs various comparisons, calculations, and operations based on the distance measurement values.
By performing control or the like, an accurate distance measurement value is obtained.

The infrared light emitted from the IRED 4 is
The light is projected on a distance measuring object via a light projecting lens (not shown) arranged on the front surface of the ED 4, a part of the light is reflected, and the reflected light is transmitted to the front surface of a PSD (position detecting element) 5. The light is received at any position on the light receiving surface of the PSD 5 via a light receiving lens (not shown) disposed on the light receiving lens. This light receiving position is
This is based on the distance to the object to be measured. And P
SD5 outputs two signals I1 and I2 according to the light receiving position. The signal I1 is a near-side signal having a larger value as the distance is shorter if the amount of received light is constant.
Reference numeral 2 denotes a far-side signal that has a larger value as the distance increases if the received light amount is constant. The sum of signals I1 and I2 is P
SD5 represents the amount of reflected light received, and the output ratio (I1 /
(I1 + I2)) represents the light receiving position on the light receiving surface of the PSD 5, that is, the distance to the object to be measured. The near-side signal I1 is input to the PSDN terminal of the AFIC 10, and the far-side signal I2 is input to the PSDF terminal of the AFIC 10. However, in practice, a signal in which a stationary light component I0 is added to each of the near-side signal I1 and the far-side signal I2 may be input to the AFIC 10 due to external conditions.

The AFIC 10 is an integrated circuit (IC) and includes a first signal processing circuit 11, a second signal processing circuit 12, a clamp circuit 13, an arithmetic circuit 14, and an integrating circuit 15. The first signal processing circuit 11 receives the signal I1 + I0 output from the PSD 5, removes the stationary light component I0 included in the signal, and outputs the near-side signal I1. The processing circuit 12 receives the signal I2 + I0 output from the PSD 5, removes the stationary light component I0 included in the signal, and outputs the far-side signal I2.

The clamp circuit 13 includes the second signal processing circuit 1
2, the level of the clamp signal Ic and the level of the far-side signal I2 at a certain level are compared. If the former is larger, the clamp signal Ic is output. If not, the far-side signal I2 is output. The signal I2 is output as it is. Hereinafter, the signal output from the clamp circuit 13 is represented by I2c.

The arithmetic circuit 14 includes a near-side signal I1 output from the first signal processing circuit 11 and a signal I2c (far-side signal I2 and clamp signal I2c) output from the clamp circuit 13.
c), and output ratio (I1 /
(I1 + I2c)) and outputs an output ratio signal indicating the result. The integrating circuit 15 receives the output ratio signal and integrates the output ratio with the integrating capacitor 6 connected to the CINT terminal of the AFIC 10 many times, thereby improving the S / N ratio. In particular, it is important to improve the S / N ratio by increasing the integrated number when the distance to the object to be measured is large, from the integrated number when the distance is small. Then, the integrated output ratio is output from the SOUT terminal of the AFIC 10 as an AF signal. CPU1
Receives the AF signal output from the AFIC 10, performs a predetermined operation, converts the AF signal into a distance signal, and sends the distance signal to the lens driving circuit 7. The lens driving circuit 7 causes the taking lens 8 to perform a focusing operation based on the distance signal.

Next, the first signal processing circuit 1 of the AFIC 10
1, more specific circuit configurations of the clamp circuit 13 and the integration circuit 15 will be described. FIG. 2 is a circuit diagram of the first signal processing circuit 11 and the integrating circuit 15 in the distance measuring apparatus according to the present embodiment. FIG. 3 is a circuit diagram of the clamp circuit 13 in the distance measuring apparatus according to the present embodiment. The second signal processing circuit 12 has the same circuit configuration as the first signal processing circuit 11.

The first signal processing circuit 11 receives the near-side signal I1 including the steady-state light component I0 output from the PSD 5 and receives the steady-state light component I0 included therein as shown in FIG. And outputs the near side signal I1. The current (I
1 + I0) is input to the negative input terminal of the operational amplifier 20 of the first signal processing circuit 11 via the PSDN terminal of the AFIC 10. The output terminal of the operational amplifier 20 is a transistor 2
1, and the collector terminal of the transistor 21 is connected to the base terminal of the transistor 22. The collector terminal of the transistor 22 is connected to the negative input terminal of the operational amplifier 23.
4 is connected. Further, the cathode terminal of the compression diode 24 is connected to the collector terminal of the transistor 22, and the compression diode 2 is connected to the + input terminal of the operational amplifier 23.
5 are connected to the respective cathode terminals, and the first reference power source 26 is connected to the anode terminals of the compression diodes 24 and 25, respectively.

A stationary light removing capacitor 27 is externally connected to the CHF terminal of the AFIC 10, and is connected to a base terminal of a steady light removing transistor 28 in the first signal processing circuit 11. Have been. The stationary light removing capacitor 27 and the operational amplifier 23 are connected via a switch 29.
Is controlled by the CPU 1. The collector terminal of the steady light removing transistor 28 is connected to the negative input terminal of the operational amplifier 20, and the emitter terminal of the transistor 28 is grounded via the resistor 30.

The circuit diagram of the clamp circuit 13 is shown in FIG. The + input terminal of the determination comparator 37 of the clamp circuit 13 is connected to the collector terminal of the transistor 22 of the second signal processing circuit 12 and to the input terminal of the arithmetic circuit 14 via the switch 38. On the other hand, the − input terminal of the comparator for determination 37 is +
Like the transistor 22 and the compression diode 24 connected to the input terminals, the collector terminal of the transistor 51 and the cathode terminal of the compression diode 52 are connected to the input terminal of the arithmetic circuit 14 via the switch 39. ing.

The clamp current source 41 is connected to the base terminal of the transistor 51. The clamp current source 41 is a plurality of sets in which a constant current source and a switch are connected in series, and a plurality of sets are connected in parallel. Each switch is controlled by the CPU 1 to open and close. Then, the clamp current source 41 inputs the clamp current, which is the sum of the currents from the respective constant current sources corresponding to the closed switches, to the base terminal of the transistor 51. This clamp current becomes the base current of the transistor 51, and the collector potential corresponding to the magnitude of the current is input to the negative input terminal of the comparator 37 for determination.

The output terminal of the comparator 37 is connected to the switch 39, and the output signal of the comparator 37 is input to the switch 39. Further, the output terminal of the comparator 37 for determination is connected to the switch 38 via the inverter 40, and the output signal of the comparator 37 for determination is inverted before being input. Therefore, the switches 38 and 39 are in a relationship in which one is turned on and the other is turned off by the output signal from the comparator 37 for determination.

The circuit configuration of the integration circuit 15 is shown in FIG. The integration capacitor 6 externally connected to the CINT terminal of the AFIC 10
4 and connected to a constant current source 63 via a switch 62, and to an operational amplifier 6 via a switch 65.
4 and connected directly to the operational amplifier 64
Of the AFIC
It is output from 10 SOUT terminals. These switches 6
0, 62 and 65 are controlled by a control signal from the CPU 1. Also, the + input terminal of the operational amplifier 64 includes:
The second reference power supply 66 is connected.

The outline of the operation of the AFIC 10 configured as described above will be described with reference to FIGS. When the IRED 4 is not emitting light, the CPU 1 turns on the switch 29 of the first signal processing circuit 11. At this time, the steady light component I0 output from the PSD 5 is input to the first signal processing circuit 11 and is current-amplified by the operational amplifier 20 and the current amplifier including the transistors 21 and 22, and the compressed diode 24
, And is converted into a voltage signal, and this voltage signal is input to the negative input terminal of the operational amplifier 23. If the signal input to the operational amplifier 20 is large, the compression diode 24
, The signal output from the operational amplifier 23 is large, and therefore the capacitor 27
Is charged. Then, the base current is supplied to the transistor 28, so that the collector current flows through the transistor 28, and the signal input to the operational amplifier 20 among the signals I0 input to the first signal processing circuit 11 decreases. And when the operation of this closed loop is stable,
All of the signal I0 input to the first signal processing circuit 11 flows to the transistor 28, and the capacitor 27 stores a charge corresponding to the base current at that time.

When the CPU 1 turns on the IRED 4 and turns off the switch 29, the PSD 1
5 of the signal I1 + I0
Flows as a collector current through a transistor 28 to which a base potential is applied by the charge stored in the capacitor 27. It is logarithmically compressed by the diode 24, converted into a voltage signal, and output. That is, the first signal processing circuit 11 removes the steady light component I0 and outputs only the near-side signal I1. The near-side signal I1 is input to the arithmetic circuit 14. On the other hand, the second signal processing circuit 12 also
As in the first signal processing circuit 11, the stationary light component I0 is removed and only the far-side signal I2 is output.
Is input to the clamp circuit 13.

The far-side signal I 2 input to the clamp circuit 13
Is input to the + input terminal of the comparator for determination 37 of the clamp circuit 13. The clamp current output from the clamp current source 41 flows as the base current of the transistor 51, and the potential (clamp signal Ic) of the collector terminal of the transistor 51 generated by the clamp current is determined by the comparator 3.
7 to the-input terminal. The far-side signal I2 and the clamp signal Ic are compared in magnitude by the comparator 37, and one of the switches 38 and 39 is turned on and the other is turned off according to the comparison result. That is, when the far-side signal I2 is larger than the clamp signal Ic, the switch 38 is turned on, the switch 39 is turned off, and the far-side signal I2c is output as the output signal I2c of the clamp circuit 13.
2 is output. If the magnitude relationship is reversed, switch 3
8 is turned off, the switch 39 is turned on,
The clamp signal 13 is used as the output signal I2c of the clamp circuit 13.
c is output.

The signal I2c output from the clamp circuit 13
And the near-side signal I output from the first signal processing circuit 11
1 is input to the arithmetic circuit 14, where the output ratio (I1 / (I1 + I2c)) is calculated and output by the arithmetic circuit 14.
The output ratio is input to the integration circuit 15. IRED4
Is a predetermined number of times, the integration circuit 15
The switch 60 is turned on, the switches 62 and 65 are turned off, and the integrating capacitor 6 is discharged by a current corresponding to an output ratio for each of a predetermined number of calculations, and its potential drops from VREF2 ( 1st integration). Then, when the pulse emission of the predetermined number of times is completed, the switch 60 is turned off, the switch 62 is turned on, and the potential of the integration capacitor 6 lowered by the first integration is kept constant from the constant current source 63. The current increases (second integration). The CPU 1 monitors the potential of the integrating capacitor 6, measures the time required to return to the original potential, determines the AF signal based on the time, and further determines the distance to the distance measurement target.

FIG. 4 shows the relationship between the AF signal thus obtained and the distance L to the object to be measured. FIG. 4 is a diagram showing the relationship between the AF signal output from the integration circuit of the distance measuring apparatus according to the present embodiment and the distance to the distance measurement target. In the graph shown in this figure, the horizontal axis is the reciprocal (1 / L) of the distance L to the object to be measured, and the vertical axis is the output ratio (I1).
/ (I1 + I2)), that is, the AF signal. As shown in this figure, when the distance L to the object to be measured is less than a certain distance L4 (L≤L4), the signal output from the clamp circuit 13 is I2, and the output ratio is I1 / (I1 + I2). The output ratio is substantially linear with respect to the reciprocal (1 / L) of the distance L. The output ratio decreases as the distance L increases (1 / L decreases). The distance L is equal to or greater than the distance L4 (L ≧
L4), the signal output from the clamp circuit 13 is I
c, and the output ratio is I1 / (I1 + Ic). In this case as well, the output ratio decreases as the distance L increases. As described above, when the clamp circuit 13 is used, the distance L to the object to be measured can be uniquely and stably determined from the output ratio (AF signal).

The CPU 1 controls the AF thus obtained.
Based on the signal, a distance signal indicating the amount of extension of the photographing lens 8 is calculated, and the distance signal is sent to the lens drive circuit 7 to cause the photographing lens 8 to perform a focusing operation. FIG.
FIG. 3 is an explanatory diagram of conversion from an AF signal to a distance signal in the distance measuring apparatus according to the embodiment. In the graph shown in this figure,
The horizontal axis is the reciprocal (1 / L) of the distance L to the object to be measured, the left vertical axis is the AF signal, and the right vertical axis is the distance signal. Further, in this graph, the relationship between the distance L and the AF signal and the relationship between the distance L and the distance signal are shown. In particular, the distances L2, L3, L4, and L5 (where,
For each of L2 <L3 <L4 <L5, the AF signal is y2, y3, y4 and y5, and the distance signal is x2.
, X3, x4 and x5.

Here, the range of distance L ≦ L4 and the distance L
> L4, the AF signal has a substantially linear relationship with the reciprocal of the distance L (1 / L).
Is the reciprocal of the distance L (1 / L)
Is substantially linear with respect to. In each of the range L <L4 and the range L ≧ L4, the relationship between the AF signal and the distance signal is also substantially linear.

Therefore, it is possible to convert the AF signal y to the distance signal x by using the conversion equation represented by the linear equation. That is, in the range where the AF signal y exceeds the reference level for judging the presence or absence of the clamp effect (the range where the distance L is less than L4), the AF signal y is obtained by the following conversion formula (1). x = A2 · y + B2 (1) where the parameters A2 and B2 are expressed by the following equations (2) and (3).
Is represented by A2 = (x3−x2) / (y3−y2) ‥‥ (2) B2 = x2−y2 · A2 ‥‥ (3)

On the other hand, a range in which the AF signal y is equal to or less than the reference level for judging the presence or absence of the clamp effect (a range in which the distance L is equal to or greater than L4).
Then, it is determined by the following conversion equation (4). x = A3 · y + B3 (4) where the parameters A3 and B3 are expressed by the following equations (5) and (6).
Is represented by A3 = (x5−x4) / (y5−y4) ‥‥ (5) B3 = x4−y4 · A3 ‥‥ (6)

Here, equations (1) and (4) are different transformation equations. Further, when the AF signal y is equal to or less than the farthest AF signal value INFDATA corresponding to the farthest setting value of the photographing lens 8, the distance signal x is changed to the farthest distance signal value corresponding to the farthest setting value of the photographing lens 8. By using AFINF, more stable focusing control of the taking lens can be performed.

The parameters A2, B2, A3 and B3, the farthest AF signal value INFDATA and the farthest signal value
AFINF is obtained at the time of manufacture for each camera in which the distance measuring device is incorporated, and is stored in advance in the EEPROM 2 or the like. Then, these parameters are read out by the CPU 1 at the time of distance measurement, and the calculation of Expression (1) or Expression (4) is performed, and the AF signal y is converted into the distance signal x.

However, when the reflectance of the object to be measured is small and the distance to the object to be measured is large, the values of the signals I1 and I2 output from the PSD 5 become small, and it is easy to determine that the object is infinity. . 6A and 6B are diagrams illustrating the relationship between the distance to the object to be measured and the distance signal. FIG. 6A shows the case where the reflectance of the object to be measured is 36% of the standard value, and FIG. 6B shows the case where the reflectance of the object to be measured is 9% which is the low reflectance. As shown in FIG. 6A, when the reflectance of the object to be measured is 36% of the standard value, the distance signal has a value substantially proportional to the reciprocal (1 / L) of the distance L to the object to be measured. can get. However, as shown in FIG. 6B, when the reflectivity of the object to be measured is 9% of the low reflectivity, when the distance L to the object to be measured is small, the reciprocal (1 / L) is obtained. Is obtained. When the distance L is large (for example, the distance Ls in the figure), the value is not proportional to the reciprocal (1 / L).
It is out of the allowable range of the ranging error.

On the other hand, even if the reflectance of the object to be measured is low, the distance L to the object to be measured can be reduced by reducing the value of the clamp signal Ic in the clamp circuit 13. A distance signal having a value substantially proportional to the reciprocal (1 / L) of the distance signal or a distance signal having a value falling within an allowable range of the ranging error can be obtained. The distance measuring apparatus according to the present embodiment utilizes the above, and even when the reflectance of the object to be measured is small and the distance to the object to be measured is large, the distance to the object to be measured is determined. It is precisely obtained.

Next, the operation of the distance measuring apparatus according to this embodiment will be described.

FIGS. 7 and 8 are flowcharts of the AF ranging process in the ranging apparatus according to the present embodiment. FIG.
FIG. 4 is a diagram illustrating a charging voltage of an integrating capacitor in an AF ranging process of the ranging device according to the embodiment. The operation described below is performed under the control of the CPU 1.

The AF ranging process of the ranging device according to the present embodiment is started by half-pressing a release button (not shown) of the camera. First, as shown in S10 of FIG. Charging is performed. The first quick charge is CPU
This is performed by applying the power supply voltage Vcc to the integration capacitor 6 through the integration circuit 15 according to the control signal output from 1 (t1 to t2 in FIG. 9).

Then, the flow shifts to S12, where a first clamp current is set. The setting of the first clamp current is performed by the CPU 1
This is performed by outputting a control signal from and selecting a clamp current output from the clamp circuit 13. This first clamp current is set to, for example, 1 nA.

Then, the flow shifts to S14, where a second quick charge is performed. The second quick charge is performed by applying the voltage VREF2 to the integrating capacitor 6 through the integrating circuit 15 according to the control signal output from the CPU 1 (t2 in FIG. 9).
To t3).

Then, the flow shifts to S16, where a first distance measuring operation is performed. In the first distance measuring operation, the IRED 4 emits light a predetermined number of times, the reflected light reflected by the object to be measured is received by the PSD 5, and the first integration (FIG. 7) is performed in which a voltage corresponding to the distance to the object to be measured is discharged. 9 after t3 to t4), the second integration (t4 to t5 in FIG. 9) is performed, and the first distance measurement value D1 is calculated according to the total integration time of the second integration. In this first ranging operation, for example, 166 light emission and integration are performed. Note that the first distance value D1 and a second distance value D, which will be described later,
The second and third distance measurement values D3 are values that decrease as the distance from the distance measurement target increases.

Then, the flow shifts to S18, where a luminance judgment is made. The luminance determination is a process of inputting the value of the external light luminance measured by the photometric sensor 71 and determining whether the measured external light luminance value is smaller than a predetermined set value. S1
When it is determined in step 8 that the external light luminance value is not smaller than the predetermined set value, the process proceeds to S20.

At S20, a third quick charge is performed. Similar to the first quick charge, the third quick charge is performed by applying the power supply voltage Vcc to the integrating capacitor 6 through the integrating circuit 15 according to a control signal output from the CPU 1 (t5 to t6 in FIG. 9).

Then, the flow shifts to S22, where a first clamp current is set. The setting of the first clamp current is performed in the same manner as in S12. Then, the flow shifts to S24, where a fourth quick charge is performed. The fourth quick charge is performed by applying the voltage VREF2 to the integration capacitor 6 through the integration circuit 15 in accordance with the control signal output from the CPU 1 in the same manner as the second quick charge (t6 to t7 in FIG. 9).

Then, the flow shifts to S26, where a second distance measuring operation is performed. In the second distance measuring operation, the IRED 4 emits light a predetermined number of times, the reflected light reflected by the object to be measured is received by the PSD 5, and a voltage corresponding to the distance to the object to be measured is discharged by a first integration (FIG. 9, the second integration (t8 to t9 in FIG. 9) is performed, and the second distance measurement value D2 is calculated according to the total integration time of the second integration. In the second distance measuring operation, I
Light emission of the RED 4 and integration of the integration capacitor 6 are performed.
For example, in the second ranging operation, light emission and integration are performed 164 times.

Then, the flow shifts to S28, where a second distance measurement value D2 is set.
Is performed. This correction process is performed by adding a predetermined value to the second distance measurement value D2 calculated in S26 to obtain a second distance measurement value D2. Here, the predetermined value is, for example, -15 when the second distance measurement value D2 is 1000 counts corresponding to a distance of 3.5 m and the second distance measurement value D2 is 1900 counts corresponding to a distance of 0.8 m. ~
Set within the range of +40 counts.

Then, the flow shifts to S30, where the first distance measurement value D1 is stored.
The distance signal is calculated based on the second distance value D2.
That is, the sum of the first distance measurement value D1 and the second distance measurement value D2 is used as the AF signal y, and the above equation (1) or equation (4) is used.
Calculates the distance signal x. Then, after calculating the distance signal, the AF distance measurement processing ends.

When it is determined in S18 that the external light luminance value is smaller than the predetermined set value, the flow shifts to S32, where the first distance measurement value D1 calculated in the first distance measurement operation is set in advance. It is determined whether the value is equal to or less than the set value A1. If it is determined in S32 that the first distance value D1 is not less than the set value A1, the process proceeds to S34, and it is determined whether the first distance value D1 is larger than a preset value A2. .

At S34, first distance value D1 is set to set value A2.
If it is determined that the distance is larger than the distance, the process proceeds to S36, and a distance signal is calculated based on the first distance measurement value D1. That is, the AF signal y is obtained by doubling the first distance value D1.
The distance signal x is calculated by the above equation (1) or (4). Then, after calculating the distance signal, the AF distance measurement processing ends.

On the other hand, when it is determined in S34 that the first distance measurement value D1 is not larger than the set value A2, the flow shifts to S38, where the third quick charge is performed. Similar to the first quick charge, the third quick charge is performed by applying the power supply voltage Vcc to the integrating capacitor 6 through the integrating circuit 15 in accordance with the control signal output from the CPU 1 (t5 to t5 in FIG. 9).
t6).

Then, the flow shifts to S40, where a first clamp current is set. The setting of the first clamp current is performed in the same manner as in S12. Then, the flow shifts to S42, where a fourth quick charge is performed. The fourth quick charge is performed by applying the voltage VREF2 to the integration capacitor 6 through the integration circuit 15 in accordance with the control signal output from the CPU 1 in the same manner as the second quick charge (t6 to t7 in FIG. 9).

Then, the flow shifts to S44, where a second distance measuring operation is performed. The second ranging operation is the same processing as S26, in which the IRED 4 emits light a predetermined number of times, the light reflected by the ranging object is received by the PSD 5, and a voltage corresponding to the distance to the ranging object is received. Is discharged (from t7 in FIG. 9).
After performing t8), the second integration (t8 to t9 in FIG. 9) is performed, and the second distance measurement value D2 is calculated according to the total integration time of the second integration.
Is calculated.

Then, the flow shifts to S46, where a second distance value D2 is stored.
Is performed. This correction process is performed by adding a predetermined value to the second distance measurement value D2 calculated in S44 to obtain a second distance measurement value D2. Here, the predetermined value is, for example, -15 when the second distance measurement value D2 is 1000 counts corresponding to a distance of 3.5 m and the second distance measurement value D2 is 1900 counts corresponding to a distance of 0.8 m. ~
Set within the range of +40 counts.

Then, the flow shifts to S48, where the first distance measurement value D1 is set.
The distance signal is calculated based on the second distance value D2.
That is, the sum of the first distance measurement value D1 and the second distance measurement value D2 is used as the AF signal y, and the above equation (1) or equation (4) is used.
Calculates the distance signal x. Then, after calculating the distance signal, the AF distance measurement processing ends.

When it is determined in S32 that the first distance measurement value D1 is equal to or less than the set value A1, it is determined that the distance to the object to be measured is long, and the process proceeds to S50. S5
At 0, the third quick charge is performed. Similar to the first quick charge, the third quick charge is performed by applying the power supply voltage Vcc to the integrating capacitor 6 through the integrating circuit 15 in accordance with the control signal output from the CPU 1 (t5 to t5 in FIG. 9).
t6).

Then, the flow shifts to S52, where a second clamp current is set. The setting of the second clamp current is performed by the CPU 1
This is performed by outputting a control signal from and selecting a clamp current output from the clamp circuit 13. As the second clamp current, a current smaller than the first clamp current is set, for example, 0.5 nA.

Then, the flow shifts to S54, where a fourth quick charge is performed. The fourth quick charge is performed in the same manner as the second quick charge, in accordance with a control signal output from the CPU 1.
This is performed by applying the voltage VREF2 to the integrating capacitor 6 through the step 5 (t6 to t7 in FIG. 9).

Then, the flow shifts to S56, where a second distance measuring operation is performed. The second ranging operation is the same processing as S26, in which the IRED 4 emits light a predetermined number of times, the light reflected by the ranging object is received by the PSD 5, and a voltage corresponding to the distance to the ranging object is received. Is discharged (from t7 in FIG. 9).
After performing t8), the second integration (t8 to t9 in FIG. 9) is performed, and the second distance measurement value D2 is calculated according to the total integration time of the second integration.
Is calculated.

Then, the flow shifts to S58, where the second distance value D2 is stored.
Is performed. This correction process is performed by adding a predetermined value to the second distance measurement value D2 calculated in S56 to obtain a second distance measurement value D2. Here, the predetermined value is, for example, -15 when the second distance measurement value D2 is 1000 counts corresponding to a distance of 3.5 m and the second distance measurement value D2 is 1900 counts corresponding to a distance of 0.8 m. ~
Set within the range of +40 counts.

Then, the flow shifts to S60, where a second distance measurement value D2 is set.
Is larger than a set value B set in advance. When it is determined that the second distance measurement value D2 is larger than the set value B, the flow shifts to S62, and a fifth quick charge is performed.
The fifth quick charge is performed by applying the power supply voltage Vcc to the integration capacitor 6 through the integration circuit 15 in accordance with the control signal output from the CPU 1 in the same manner as the third quick charge (t9 to t10 in FIG. 9).

Then, the flow shifts to S64, where a first clamp current is set. The setting of the first clamp current is performed in the same manner as in S12. Then, the flow shifts to S66, where sixth quick charge is performed. The sixth quick charge is performed by applying the voltage VREF2 to the integration capacitor 6 through the integration circuit 15 according to the control signal output from the CPU 1 in the same manner as the fourth quick charge (t10 to t11 in FIG. 9).

Then, the flow shifts to S68, where a third distance measuring operation is performed. The third distance measuring operation is performed in the same manner as the second distance measuring operation of S56. The IRED 4 is made to emit light a predetermined number of times. First integration for discharging a voltage corresponding to the distance (FIG. 9
After performing t11 to t12), the second integration (t1 in FIG. 9)
2 to t13), and the third distance measurement value D3 is calculated according to the total integration time of the second integration. In the third ranging operation, light emission of the IRED 4 and integration of the integrating capacitor 6 are performed with a smaller number of times than the first ranging operation. For example, in the third ranging operation, light emission and integration are performed 164 times.

Then, the flow shifts to S70, for obtaining the third distance value D3.
Is performed. This correction process is performed by adding a predetermined value to the third distance measurement value D3 calculated in S68 to obtain a third distance measurement value D3. Here, the predetermined value is, for example, -15 when the third distance measurement value D3 is 1000 counts corresponding to the distance of 3.5 m and the third distance measurement value D3 is 1900 counts corresponding to the distance of 0.8 m. ~
Set within the range of +40 counts.

Then, the flow shifts to S72, where the first distance measurement value D1 is set.
And a distance signal is calculated based on the third distance value D3.
That is, the sum of the first distance measurement value D1 and the third distance measurement value D3 is used as the AF signal y, and the above equation (1) or equation (4) is used.
Calculates the distance signal x. Then, after calculating the distance signal, the AF distance measurement processing ends.

If it is determined in S60 that the second distance value D2 is not larger than the set value B, the process proceeds to S74.
Move to In S74, the value (D1 + D1) obtained by adding the first distance value D1 and the first distance value D1 is larger than the preset value C, and the first distance value D1 is calculated from the second distance value D2. It is determined whether the subtracted value (D2-D1) is greater than a preset value E1.

At S74, the value (D1 + D1) obtained by adding the first distance value D1 and the first distance value D1 is greater than the set value C, and the first distance value D1 is obtained from the second distance value D2. When it is determined that the value (D2-D1) obtained by subtracting is larger than the set value E1, the process proceeds to S80.

On the other hand, the value obtained by adding the first distance value D1 and the first distance value D1 (D1 + D1) is not larger than the set value C or the value obtained by subtracting the first distance value D1 from the second distance value D2. (D2
When it is determined that -D1) is not larger than the set value E1, the process proceeds to S76. In S76, the second distance value D2
It is determined whether or not a value (D2-D1) obtained by subtracting the first distance measurement value D1 is smaller than a preset value E2. Here, the set value E2 is set to a numerical value larger than the set value E1.

If it is determined in step S76 that the value obtained by subtracting the first distance measurement value D1 from the second distance measurement value D2 (D2-D1) is smaller than the set value E2, the process proceeds to step S62. On the other hand, when it is determined in S76 that the value (D2-D1) obtained by subtracting the first distance measurement value D1 from the second distance measurement value D2 is not smaller than the set value E2, the process proceeds to S78.

In S78, it is determined whether or not the second distance value D2 is smaller than a preset value F. here,
As the set value F, a numerical value smaller than the set value B is set. S
When it is determined at 78 that the second distance measurement value D2 is smaller than the set value F in advance, the process proceeds to S62. On the other hand, S78
When it is determined that the second distance measurement value D2 is not smaller than the set value F in advance, the process proceeds to S80.

In S80, a fifth quick charge is performed. The fifth quick charge is performed by applying the power supply voltage Vcc to the integration capacitor 6 through the integration circuit 15 in accordance with the control signal output from the CPU 1 in the same manner as the third quick charge (t9 to t10 in FIG. 9).

Then, the flow shifts to S82, where a second clamp current is set. The setting of the second clamp current is performed in the same manner as in S52. Then, the flow shifts to S84, where sixth quick charging is performed. The sixth quick charge is performed by applying the voltage VREF2 to the integration capacitor 6 through the integration circuit 15 according to the control signal output from the CPU 1 in the same manner as the fourth quick charge (t10 to t11 in FIG. 9).

Then, the flow shifts to S86, where a third distance measuring operation is performed. The third distance measuring operation is performed in the same manner as the second distance measuring operation of S56. The IRED 4 is made to emit light a predetermined number of times. First integration for discharging a voltage corresponding to the distance (FIG. 9
After performing t11 to t12), the second integration (t1 in FIG. 9)
2 to t13), and the third distance measurement value D3 is calculated according to the total integration time of the second integration. In the third ranging operation, light emission of the IRED 4 and integration of the integrating capacitor 6 are performed with a smaller number of times than the first ranging operation. For example, in the third ranging operation, light emission and integration are performed 164 times.

Then, the flow shifts to S88, for obtaining the third distance measurement value D3.
Is performed. This correction process is performed by adding a predetermined value to the third distance measurement value D3 calculated in S86 to obtain a third distance measurement value D3. Here, the predetermined value is, for example, -15 when the third distance measurement value D3 is 1000 counts corresponding to the distance of 3.5 m and the third distance measurement value D3 is 1900 counts corresponding to the distance of 0.8 m. ~
Set within the range of +40 counts.

Then, the flow shifts to S90, where the second distance value D2 is stored.
And a distance signal is calculated based on the third distance value D3.
That is, the sum of the second distance measurement value D2 and the third distance measurement value D3 is used as the AF signal y, and the above equation (1) or equation (4) is used.
Calculates the distance signal x. Then, after calculating the distance signal, the AF distance measurement processing ends.

Thereafter, when the release button is fully depressed, the CPU 1 controls the lens drive circuit 7 based on the obtained distance to cause the photographing lens 8 to perform an appropriate focusing operation, and furthermore, the shutter ( (Not shown) is opened to perform exposure.

FIGS. 10 and 11 show the results of distance measurement by the distance measuring apparatus according to the present embodiment.

FIG. 10 shows high luminance (high luminance in a luminance range lower than the set value of S18 in FIG. 7) and a reflectance of 90%.
The data is obtained when the distance is measured for the% distance measurement target. In FIG. 10, “with AFD 90” means a case in which the determination processing in S60 of FIG. 8 is performed and the distance is measured. Further, “AFD 90 is absent” means that the distance is measured without performing the determination process in S60 of FIG. Considering FIG. 10, it can be seen that by performing the determination processing in S <b> 60, a distance measurement result close to the set value is obtained in the distance signal on the long distance side.

FIG. 11 shows data when the distance is measured for a distance measuring object having a reflectance of 36%. In FIG. 11, "S
“AHDATA present” means that the determination process in S78 of FIG. 8 is performed and the distance is measured. Also, "SAHDA
"No TA" means a case where the distance is measured without performing the determination process in S78 of FIG. Considering FIG. 11, S78
It can be understood that the distance measurement result close to the set value in the distance signal can be obtained in the range of the distance reciprocal value of 0.08 to 0.10.

FIG. 12 is a diagram showing the relationship between the distance reciprocal and the AF signal.

FIG. 12 shows data when the same object to be measured is continuously measured. However, as shown in FIG. 12, in the case of continuous distance measurement, since the first distance measurement value in the first distance measurement and the second distance measurement value thereafter change the characteristic of the integrating capacitor, both are not necessarily the same. Not a value.

Therefore, in the distance measuring apparatus according to the present embodiment,
The number of integrations in the second ranging operation is smaller than the number of integrations in the first ranging operation. Thereby, in FIG. 12, the inclination of the characteristic of the second ranging operation can be matched with the inclination of the characteristic of the first ranging operation. In the distance measuring apparatus according to the present embodiment, the correction is performed by adding a predetermined value to the second distance measurement value obtained by the second distance measurement operation. Thereby, the second distance measurement value can be increased, and can be set to a value equivalent to the first distance measurement value.

FIGS. 13 to 15 show that the object to be measured has a reflectance of 36.
%, 9%, and 90%, the distance measurement results when the clamp current is set large (the clamp signal level is set high) and when the clamp current is set small (the clamp signal level is set low) It is shown.

As described above, according to the distance measuring apparatus of the present embodiment, when the external light luminance is relatively high and the reflectance of the object to be measured is large, the second distance value D2 is closer to the near side. Even if it is detected as a value, when the second distance value D2 is a value closer to the second set distance, the clamp signal is set to the first high level and the third distance value is set. D3 is detected,
The distance to the distance measurement target is calculated based on the sum of the first distance measurement value D1 and the third distance measurement value D3. For this reason, the distance to the object to be measured can be accurately detected.

Even when the value obtained by subtracting the first distance value D1 from the second distance value D2 is not smaller than the set value E2,
When the second distance value D2 is smaller than the set value F and farther than the predetermined distance, the clamp signal is set to the first level, and the third distance value D3 is detected. The distance to the distance measurement target is calculated based on the sum of the distance measurement value D1 and the third distance measurement value D3. Therefore, when the reflectance of the object to be measured is about the same as the reference reflectance, the clamp signal is set to the first level and the third measured value D3 is detected, so that the third measured value is obtained. D3 is prevented from being detected as a value closer to the design value. For this reason, the distance to the object to be measured can be accurately detected.

The first distance value D1 and the first distance value D
1 is greater than the set value C and the second distance measurement value D2 is
When the value obtained by subtracting the distance measurement value D1 is larger than the set value E1, the clamp signal is set to the second level, the third distance measurement value D3 is detected, and the second distance measurement value D2 and the third distance measurement value D3 are detected. The distance to the object to be measured is calculated based on the sum of the distance values D3. Therefore, when the reflectance of the object to be measured is small, the clamp signal is set to the second level and the third measured value D3 is detected, so that the third measured value D3 is farther than the designed value. Is reduced as a value on the side. For this reason, the distance to the object to be measured can be accurately detected.

In the case where distance measurement is performed continuously and the distance to the object to be measured is detected based on a plurality of distance measurement values, the integration processing of the first distance measurement value detection and the second distance measurement value detection are performed. Changes in the characteristics of the integration capacitor 6 in the integration process of FIG.
The sum of the integration periods in the distance measurement value detection and the second distance measurement value detection is made different, and the second distance measurement value is corrected by adding a predetermined value to the second distance measurement value. 2 can correct the fluctuation of the distance measurement value. For this reason, the distance to the object to be measured can be accurately detected.

In the distance measuring apparatus according to the present embodiment, A
In the ranging operation of the F ranging process, the integration operation is performed by discharging the voltage of the integration capacitor 6 many times in accordance with the output ratio output from the arithmetic circuit 14. It is not limited to such things,
As the integration operation, the integration capacitor 6 may be charged according to the output ratio.

In the distance measuring apparatus according to the present embodiment, A
In the distance measuring operation of the F distance measuring process, the first integration by discharging the integration capacitor 6 and the second integration by charging are performed, and the distance is detected from the time required for the second integration. Is not limited to such, and discharges or charges (first integration) with respect to the integrating capacitor 6 in accordance with the output ratio, and the voltage value reduced by the discharging or the voltage value increased by the charging is A / D-conversion may be performed, and the distance may be detected based on the result.

(Second Embodiment) Next, a distance measuring apparatus according to a second embodiment will be described.

In the distance measuring apparatus according to the first embodiment, it is determined whether or not a value (D1 + D1) obtained by adding the first distance value D1 and the first distance value D1 in S74 of the AF distance processing is larger than the set value C. Is one of the determination conditions. In the distance measuring apparatus according to the present embodiment, whether the value (D1 + D2) obtained by adding the first distance value D1 and the second distance value D2 is larger than the set value C or not is determined. Alternatively, a value obtained by adding the second distance measurement value D2 and the second distance measurement value D2 (D2 + D
Whether 2) is greater than the set value C is one of the determination conditions in S74. Note that the distance measuring device according to the present embodiment has
This is the same as the distance measuring device according to the first embodiment.

FIGS. 16 and 17 show the relationship between the distance and the AF signal (AFDATA) when the determination conditions in S74 are changed.

FIG. 16 shows a reference reflectance of 36%.
This is data when the distance is measured for the object to be measured. FIG.
Considering the case No. 6, when the judgment condition is D1 + D1 (D1 +
(When D1> C), when D1 + D2 (D1 + D
2> C), the characteristic change rate is small at a distance of 8.5 m. When D2 + D2 (when D2 + D2> C)
Furthermore, the characteristic change is small.

FIG. 17 shows data when the distance is measured for a distance measuring object having a reflectance of 9%. Considering FIG. 17, when the determination condition is D1 + D1 (D1 + D1> C), when D1 + D2 (D1 + D2> C),
The characteristic change rate at a distance of 4.25 m is small. Also, D
When 2 + D2 (when D2 + D2> C), the characteristic change is further small.

FIGS. 18 and 19 show the distance measurement results (comparative examples) when the distance was measured without performing the determination processing of S74 in the AF distance measurement processing of FIGS.

Considering FIG. 18, when the distance is measured for a distance measuring object having a reflectance of 9%, sufficient linearity is obtained. However, when distance measurement is performed on a distance measurement target having a reflectance of 36%, the distance signal is calculated to be larger on the far side of 8.5 m or more. In the distance measurement in FIG. 18, the set value E2 is set to a small value (30).

Considering FIG. 19, a sufficient linearity is obtained when the distance is measured for an object having a reflectivity of 36%. However, when distance measurement is performed on a distance measurement target having a reflectance of 9%, the distance signal is calculated to be smaller in a distance range of 4.25 to 6 m.

FIGS. 20 and 21 show the results of distance measurement by the distance measuring apparatus according to the present embodiment and the distance measuring apparatus according to the first embodiment.
It is a distance measurement result when the distance measurement is performed by performing the determination processing of S74 in the AF distance measurement processing.

FIG. 20 shows data obtained as a result of distance measurement for a distance measurement target having a reflectance of 36%. Considering FIG. 20, in all of the determination conditions D1 + D1, D1 + D2, and D2 + D2, the same distance measurement result as the design value is obtained, and sufficient linearity is obtained.

FIG. 21 shows data obtained as a result of distance measurement for a distance measurement target having a reflectance of 9%. Considering FIG. 21,
In the determination condition D1 + D1, the distance signal is calculated to be smaller in the distance range of 4.5 to 6 m. When this is compared with the characteristic of the reflectance of 9% (broken line) in FIG. 19, it can be seen that the distance range in which the distance signal is calculated to be smaller is reduced, and the distance measurement accuracy is improved.

In the judgment condition D1 + D2, 4.75 to 6 m
The distance signal is calculated to be smaller in the distance range of. When this is compared with the characteristic of the reflectance of 9% (broken line) in FIG. 19, it can be seen that the distance range in which the distance signal is calculated to be smaller is also reduced, and the distance measurement accuracy is improved. Under the determination condition D2 + D2, the same distance measurement result as the design value is obtained, and sufficient linearity is obtained.

As described above, according to the distance measuring apparatus of the present embodiment, the distance measurement result closer to the design value can be obtained by setting the determination condition of S74 in the AF distance measurement processing from D1 + D1 to D1 + D2 or D2 + D2. The distance measurement accuracy can be improved.

[0136]

As described above in detail, according to the present invention, when the external light luminance is relatively high and the reflectance of the object to be measured is large, the second distance measurement value is detected as a near value. However, if the second distance value is closer to the second set distance, the clamp signal is set to the first high level, and the third distance value is detected. The first ranging value and the third
Is calculated based on the sum of the distance measurement values. For this reason, the distance to the object to be measured can be accurately detected.

Even when the value obtained by subtracting the first distance measurement value from the second distance measurement value is not smaller than the set value, the second distance measurement value is smaller than the set value and is farther from the predetermined set distance. If the value is the value, the clamp signal is set to the first level, the third distance value is detected, and the distance to the distance object is determined based on the sum of the first distance value and the third distance value. Is calculated. Therefore, when the reflectance of the object to be measured is approximately equal to the reference reflectance, the clamp signal is set to the first level and the third distance measurement value is detected. It is prevented from being detected as a value closer to the design value. For this reason, the distance to the object to be measured can be accurately detected.

When the sum of the first distance measurement value and the first distance measurement value is larger than the set value and the value obtained by subtracting the first distance measurement value from the second distance measurement value is larger than the set value, the clamp is performed. The second signal
And the third distance measurement value is detected, and the distance to the distance measurement target is calculated based on the sum of the second distance measurement value and the third distance measurement value. For this reason, when the reflectance of the object to be measured is small, the clamp signal is set to the second level and the third measured value is detected, so that the third measured value is on the far side from the design value. Detection as a value is reduced. For this reason, the distance to the object to be measured can be accurately detected.

In the case where distance measurement is continuously performed to detect the distance to the object to be measured based on a plurality of distance measurement values, the integration processing of the first distance measurement value detection and the second distance measurement value detection are performed. Changes in the integration capacitor characteristic in the integration processing of (1), the sum of the integration periods in the first distance measurement value detection and the second distance measurement value detection is made different, and a predetermined value is set in the second distance measurement value. By adding and correcting, it is possible to correct a change in the second distance measurement value due to a change in the characteristic of the integration capacitor. For this reason, the distance to the object to be measured can be accurately detected.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a distance measuring device according to a first embodiment.

FIG. 2 is a circuit diagram of a first signal processing circuit and an integrating circuit in the distance measuring apparatus according to the first embodiment.

FIG. 3 is a circuit diagram of a clamp circuit in the distance measuring device according to the first embodiment.

FIG. 4 is a diagram showing a relationship between an AF signal output from an integration circuit of the distance measuring apparatus according to the first embodiment and a distance to a distance measurement target.

FIG. 5 is an explanatory diagram of a conversion from an AF signal to a distance signal in the distance measuring apparatus according to the first embodiment.

FIG. 6 is a diagram illustrating a relationship between a distance to a distance measurement target and a distance signal.

FIG. 7 is a flowchart showing an operation of the distance measuring apparatus according to the first embodiment.

FIG. 8 is a flowchart showing an operation of the distance measuring apparatus according to the first embodiment.

FIG. 9 is a timing chart in the operation of the distance measuring apparatus according to the first embodiment.

FIG. 10 is a diagram showing a distance measurement result of the distance measurement device according to the first embodiment.

FIG. 11 is a diagram illustrating a distance measurement result of the distance measurement device according to the first embodiment.

FIG. 12 is a diagram showing a relationship between a distance reciprocal and an AF signal in continuous ranging.

FIG. 13 is a diagram showing distance measurement data when the object to be measured has a reflectance of 36%.

FIG. 14 is a diagram showing distance measurement data when the object to be measured has a reflectance of 9%.

FIG. 15 is a diagram showing distance measurement data when the object to be measured has a reflectance of 90%.

FIG. 16 is a diagram showing the relationship between the distance and the AF signal (AFDATA) when the determination conditions in S74 are changed in the AF distance measurement processing.

FIG. 17 is a diagram showing the relationship between the distance and the AF signal (AFDATA) when the determination conditions in S74 are changed in the AF distance measurement process.

FIG. 18 is a diagram illustrating a distance measurement result (comparative example) when performing distance measurement without performing the determination processing of S74 in the AF distance measurement processing.

FIG. 19 is a diagram illustrating a distance measurement result (comparative example) when the distance is measured without performing the determination processing of S74 in the AF distance measurement processing.

FIG. 20 is a diagram showing a distance measurement result in the distance measurement device according to the second embodiment.

FIG. 21 is a diagram showing a distance measurement result in the distance measurement device according to the second embodiment.

FIG. 22 is a configuration diagram of a distance measuring apparatus according to a first related art.

FIG. 23 shows A output from the first prior art integrating circuit;
FIG. 4 is a diagram illustrating a relationship between an F signal and a distance to a distance measurement target.

FIG. 24 is a configuration diagram of a modified example of the distance measuring apparatus according to the first related art.

FIG. 25 is a configuration diagram of a distance measuring apparatus according to a second related art.

FIG. 26 is a configuration diagram of a distance measuring apparatus according to a third conventional technique.

FIG. 27 shows a case where the reflectance of the object to be measured is 36%.
9 is a graph showing a relationship between a distance signal and a distance obtained by a distance measuring device according to a first related art.

FIG. 28 is a graph showing a relationship between a distance signal and a distance obtained by the distance measuring apparatus according to the first related art when the reflectance of the distance measuring object is 9%.

FIG. 29 illustrates a case where the reflectance of the object to be measured is 36%.
9 is a graph showing a relationship between a distance signal and a distance obtained by a distance measuring device according to each of the second and third conventional techniques.

FIG. 30 is a graph showing a relationship between a distance signal and a distance obtained by a distance measuring device according to each of the second and third conventional techniques when the reflectance of the distance measuring object is 9%.

FIG. 31 shows a case where the level of the clamp signal Ic is reduced and the reflectance of the object to be measured is 36%.
9 is a graph showing a relationship between a distance signal and a distance obtained by a distance measuring device according to a first related art.

FIG. 32 shows a distance signal, a distance and a distance signal obtained by the distance measuring apparatus according to the first prior art when the level of the clamp signal Ic is reduced and the reflectivity of the distance measuring object is 9%. 6 is a graph showing the relationship of.

FIG. 33 shows a case where the level of the clamp signal Ic is reduced, the external light luminance is large, and the reflectance of the object to be measured is 3;
9 is a graph showing a relationship between a distance signal and a distance obtained by the distance measuring apparatus according to the first related art when the ratio is 6%.

FIG. 34 shows a case where the level of the clamp signal Ic is reduced, the external light luminance is large, and the reflectance of the object to be measured is 9;
6 is a graph showing the relationship between the distance signal and the distance obtained by the distance measuring device according to the first conventional technique when the distance is%.

FIG. 35 is a diagram illustrating a first case where the amount of light projected from the IRED is quadrupled and the reflectance of the object to be measured is 36%.
6 is a graph showing a relationship between a distance signal and a distance obtained by a distance measuring device according to the related art.

FIG. 36 shows a distance signal and a distance signal obtained by the distance measuring apparatus according to the first conventional technique when the amount of light projected from the IRED is quadrupled and the reflectivity of the distance measuring object is 9%. It is a graph which shows the relationship with distance.

[Explanation of symbols]

1 CPU, 2 EEPROM, 3 driver, 4 IRED (light emitting diode), 5
PSD (Position Detector), 6 ... Integrating capacitor, 7
... Lens drive circuit, 8 ... Shooting lens, 10 ...
· AFIC (autofocus IC), 11: first signal processing circuit, 12: second signal processing circuit, 13: clamp circuit, 14: arithmetic circuit, 15: integrating circuit,
71 ・ ・ ・ Photometric sensor

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Claims (10)

[Claims] A light projecting unit for projecting a light beam toward the object to be measured, and a reflecting light of the light beam projected on the object to be measured according to a distance to the object to be measured. The light is received at the light receiving position on the position detection element, and based on the light receiving position, if the received light amount is constant, the far side signal is larger as the distance is longer, and if the received light amount is constant, the distance is shorter. A light receiving unit that outputs a near-side signal having a larger value, and receives the far-side signal and compares the level with a level of a clamp signal. If the level of the far-side signal is equal to or greater than the level of the clamp signal, Clamping means for outputting the far-side signal, and otherwise outputting the clamp signal, and calculating a ratio between the near-side signal and the signal output from the clamp means to output an output ratio signal Means for integrating the output ratio signal Integrating means for outputting an integration signal according to the integration result; light emission of the light beam by the light emitting means; level of the clamp signal in the clamp means; and integration period of the output ratio signal in the integration means. And control means for controlling each of the sums of the above, and detecting a distance measurement value based on the integration signal output from the integration means, wherein the control means: Setting the sum of the integration period of the output ratio signal in the integration means to a first number, and detecting a first ranging value based on the integration signal output from the integration means; b) setting the clamp signal to a second level smaller than the first level when the first distance value is a value farther than the first set distance; Setting the sum of the integration periods of the output ratio signal to a second number and detecting a second distance measurement value based on the integration signal output from the integration means; and (c) the second distance measurement. When the value is closer to the second set distance, or when the second measured value is not closer to the second set distance and the second measured value is smaller than the second set distance. When the value obtained by subtracting the distance measurement value of 1 is smaller than a first set value, the clamp signal is set to the first level, and the sum of the integration period of the output ratio signal in the integration means is set to a third value. A third distance measurement value is detected based on the integration signal output from the integration means with the number set to a number, and the measurement is performed based on the sum of the first distance measurement value and the third distance measurement value. Calculating a distance to a distance target; and (d) the second distance measurement value is not a value closer than a second set distance and the second distance measurement is performed. When the value obtained by subtracting the first distance measurement value from the value is not smaller than a first set value, the clamp signal is set to the second level, A sum is set to a third number, a third distance value is detected based on the integration signal output from the integration means, and a sum of the second distance value and the third distance value is detected. A distance measuring device that calculates a distance to the object to be measured based on the distance. 2. A light projecting means for projecting a light beam toward an object to be measured, and reflecting light of the light beam projected on the object to be measured according to a distance to the object to be measured. The light is received at the light receiving position on the position detection element, and based on the light receiving position, if the received light amount is constant, the far side signal is larger as the distance is longer, and if the received light amount is constant, the distance is shorter. A light receiving unit that outputs a near-side signal having a larger value, and receives the far-side signal and compares the level with a level of a clamp signal. If the level of the far-side signal is equal to or greater than the level of the clamp signal, Clamping means for outputting the far-side signal, and otherwise outputting the clamp signal, and calculating a ratio between the near-side signal and the signal output from the clamp means to output an output ratio signal Means for integrating the output ratio signal Integrating means for outputting an integration signal according to the integration result; light emission of the light beam by the light emitting means; level of the clamp signal in the clamp means; and integration period of the output ratio signal in the integration means. And control means for controlling each of the sums of the above, and detecting a distance measurement value based on the integration signal output from the integration means, wherein the control means: Setting the sum of the integration period of the output ratio signal in the integration means to a first number, and detecting a first ranging value based on the integration signal output from the integration means; b) setting the clamp signal to a second level smaller than the first level when the first distance value is a value farther than the first set distance; Setting the sum of the integration periods of the output ratio signal to a second number and detecting a second distance measurement value based on the integration signal output from the integration means; and (c) the second distance measurement. When the value obtained by subtracting the first distance value from the value is smaller than a first set value, or when the value obtained by subtracting the first distance value from the second distance value is equal to the first set value. When the second distance measurement value is not smaller than the value and the second distance measurement value is a value farther than the third set distance, the clamp signal is set to the first level; The sum of the integration periods is set to a third number, and a third distance measurement value is detected based on the integration signal output from the integration means, and the first distance measurement value and the third distance measurement are detected. Calculating the distance to the object to be measured based on the sum of the values; and (d) subtracting the first distance measurement value from the second distance measurement value. When the value is not smaller than the first set value and the second distance measurement value is not a value farther than the third set distance, the clamp signal is set to the second level. The sum of the integration periods of the output ratio signal is set to a third number, and a third ranging value is detected based on the integration signal output from the integrating means, and the second ranging value and the third ranging value are detected. A distance measuring device that calculates a distance to the distance measurement target based on a sum of third distance measurement values. 3. A light projecting means for projecting a light beam toward the object to be measured, and reflecting light of the light beam projected on the object to be measured in accordance with a distance to the object to be measured. The light is received at the light receiving position on the position detection element, and based on the light receiving position, if the received light amount is constant, the far side signal is larger as the distance is longer, and if the received light amount is constant, the distance is shorter. A light receiving unit that outputs a near-side signal having a larger value, and receives the far-side signal and compares the level with a level of a clamp signal. If the level of the far-side signal is equal to or greater than the level of the clamp signal, Clamping means for outputting the far-side signal, and otherwise outputting the clamp signal, and calculating a ratio between the near-side signal and the signal output from the clamp means to output an output ratio signal Means for integrating the output ratio signal Integrating means for outputting an integration signal according to the integration result; light emission of the light beam by the light emitting means; level of the clamp signal in the clamp means; and integration period of the output ratio signal in the integration means. And control means for controlling each of the sums of the above, and detecting a distance measurement value based on the integration signal output from the integration means, wherein the control means: Setting the sum of the integration period of the output ratio signal in the integration means to a first number, and detecting a first ranging value based on the integration signal output from the integration means; b) setting the clamp signal to a second level smaller than the first level when the first distance value is a value farther than the first set distance; Setting the sum of the integration periods of the output ratio signal to a second number and detecting a second distance measurement value based on the integration signal output from the integration means; (c) the first distance measurement Value and the first distance value are the second
Or the value obtained by subtracting the first distance value from the second distance value is not larger than the third value, and the first distance value from the second distance value. When the value obtained by subtracting the distance measurement value is smaller than a first set value, the clamp signal is set to the first level, and the sum of the integration period of the output ratio signal in the integration means is set to a third number. A third distance measurement value is detected based on the integration signal output from the integration means set, and the distance measurement target is determined based on a sum of the first distance measurement value and the third distance measurement value. Calculating the distance to the object; (d) the sum of the first distance measurement value and the first distance measurement value is a second distance value;
Is larger than the set value of the second distance measurement value and the first
When the value obtained by subtracting the distance measurement value is larger than the third set value,
Alternatively, the sum of the first distance measurement value and the first distance measurement value is a second distance measurement value.
Or a value obtained by subtracting the first distance measurement value from the second distance measurement value is not larger than a third value and the first distance measurement value is not larger than the second distance measurement value. When the value obtained by subtracting the distance measurement value is not smaller than the first set value, the clamp signal is set to the second level, and the sum of the integration period of the output ratio signal in the integration means is set to a third number. And a third distance measurement value is detected based on the integration signal output from the integration means, and the distance measurement is performed based on a sum of the second distance measurement value and the third distance measurement value. A distance measuring device that calculates the distance to an object. 4. A light projecting means for projecting a light beam toward an object to be measured, and reflecting light of the light beam projected on the object to be measured according to a distance to the object to be measured. The light is received at the light receiving position on the position detection element, and based on the light receiving position, if the received light amount is constant, the far side signal is larger as the distance is longer, and if the received light amount is constant, the distance is shorter. A light receiving unit that outputs a near-side signal having a larger value, and receives the far-side signal and compares the level with a level of a clamp signal. If the level of the far-side signal is equal to or greater than the level of the clamp signal, Clamping means for outputting the far-side signal, and otherwise outputting the clamp signal, and calculating a ratio between the near-side signal and the signal output from the clamp means to output an output ratio signal Means for integrating the output ratio signal Integrating means for outputting an integration signal according to the integration result; light emission of the light beam by the light emitting means; level of the clamp signal in the clamp means; and integration period of the output ratio signal in the integration means. And control means for controlling each of the sums of the above, and detecting a distance measurement value based on the integration signal output from the integration means, wherein the control means: Setting the sum of the integration period of the output ratio signal in the integration means to a first number, and detecting a first ranging value based on the integration signal output from the integration means; b) setting the clamp signal to a second level smaller than the first level when the first distance value is a value farther than the first set distance; Setting the sum of the integration periods of the output ratio signal to a second number and detecting a second distance measurement value based on the integration signal output from the integration means; (c) the first distance measurement Value and the second distance value are the second
Or the value obtained by subtracting the first distance value from the second distance value is not larger than the third value, and the first distance value from the second distance value. When the value obtained by subtracting the distance measurement value is smaller than a first set value, the clamp signal is set to the first level, and the sum of the integration period of the output ratio signal in the integration means is set to a third number. A third distance measurement value is detected based on the integration signal output from the integration means set, and the distance measurement target is determined based on a sum of the first distance measurement value and the third distance measurement value. Calculating the distance to the object; (d) the sum of the first distance measurement value and the second distance measurement value is a second distance measurement value;
Is larger than the set value of the second distance measurement value and the first
When the value obtained by subtracting the distance measurement value is larger than the third set value,
Alternatively, the sum of the first distance measurement value and the second distance measurement value is a second distance measurement value.
Or a value obtained by subtracting the first distance measurement value from the second distance measurement value is not larger than a third value and the first distance measurement value is not larger than the second distance measurement value. When the value obtained by subtracting the distance measurement value is not smaller than the first set value, the clamp signal is set to the second level, and the sum of the integration period of the output ratio signal in the integration means is set to a third number. And a third distance measurement value is detected based on the integration signal output from the integration means, and the distance measurement is performed based on a sum of the second distance measurement value and the third distance measurement value. A distance measuring device that calculates the distance to an object. 5. A light projecting means for projecting a light beam toward an object to be measured, and reflecting light of the light beam projected on the object to be measured according to a distance to the object to be measured. The light is received at the light receiving position on the position detection element, and based on the light receiving position, if the received light amount is constant, the far side signal is larger as the distance is longer, and if the received light amount is constant, the distance is shorter. A light receiving unit that outputs a near-side signal having a larger value, and receives the far-side signal and compares the level with a level of a clamp signal. If the level of the far-side signal is equal to or greater than the level of the clamp signal, Clamping means for outputting the far-side signal, and otherwise outputting the clamp signal, and calculating a ratio between the near-side signal and the signal output from the clamp means to output an output ratio signal Means for integrating the output ratio signal Integrating means for outputting an integration signal according to the integration result; light emission of the light beam by the light emitting means; level of the clamp signal in the clamp means; and integration period of the output ratio signal in the integration means. And control means for controlling each of the sums of the above, and detecting a distance measurement value based on the integration signal output from the integration means, wherein the control means: Setting the sum of the integration period of the output ratio signal in the integration means to a first number, and detecting a first ranging value based on the integration signal output from the integration means; b) setting the clamp signal to a second level smaller than the first level when the first distance value is a value farther than the first set distance; Setting the sum of the integration periods of the output ratio signal to a second number and detecting a second distance measurement value based on the integration signal output from the integration means; and (c) the second distance measurement. Value and the second distance value are the second
Or the value obtained by subtracting the first distance value from the second distance value is not larger than the third value, and the first distance value from the second distance value. When the value obtained by subtracting the distance measurement value is smaller than a first set value, the clamp signal is set to the first level, and the sum of the integration period of the output ratio signal in the integration means is set to a third number. A third distance measurement value is detected based on the integration signal output from the integration means set, and the distance measurement target is determined based on a sum of the first distance measurement value and the third distance measurement value. Calculating the distance to the object; (d) the sum of the second distance measurement value and the second distance measurement value is the second distance measurement value;
Is larger than the set value of the second distance measurement value and the first
When the value obtained by subtracting the distance measurement value is larger than the third set value,
Alternatively, the sum of the second distance measurement value and the second distance measurement value is the second distance measurement value.
Or a value obtained by subtracting the first distance measurement value from the second distance measurement value is not larger than a third value and the first distance measurement value is not larger than the second distance measurement value. When the value obtained by subtracting the distance measurement value is not smaller than the first set value, the clamp signal is set to the second level, and the sum of the integration period of the output ratio signal in the integration means is set to a third number. And a third distance measurement value is detected based on the integration signal output from the integration means, and the distance measurement is performed based on a sum of the second distance measurement value and the third distance measurement value. A distance measuring device that calculates the distance to an object. 6. A light projecting means for projecting a light beam toward an object to be measured, and reflecting light of the light beam projected on the object to be measured in accordance with a distance to the object to be measured. The light is received at the light receiving position on the position detection element, and based on the light receiving position, if the received light amount is constant, the far side signal is larger as the distance is longer, and if the received light amount is constant, the distance is shorter. A light receiving unit that outputs a near-side signal having a larger value, and receives the far-side signal and compares the level with a level of a clamp signal. If the level of the far-side signal is equal to or greater than the level of the clamp signal, Clamping means for outputting the far-side signal, and otherwise outputting the clamp signal, and calculating a ratio between the near-side signal and the signal output from the clamp means to output an output ratio signal Means for integrating the output ratio signal Integrating means for integrating and integrating the result of the integration, and outputting an integrated signal according to the integration result; light emission of the light beam by the light emitting means, level of the clamp signal by the clamp means, and output by the integration means. Control means for controlling each of the sums of the integration periods of the ratio signal and detecting a distance measurement value based on the integration signal output from the integration means, wherein: (a) the clamp signal Is set to a first level, and the sum of the integration period of the output ratio signal in the integration means is set to a first number, and a first distance measurement value is set based on the integration signal output from the integration means. (B) setting the clamp signal to a second level, and setting the sum of the integration periods of the output ratio signal in the integration means to a second number smaller than the first number Detecting a second distance measurement value based on the integration signal outputted from said integrating means Te, (c) the a second distance measurement value by adding a predetermined value the second
A distance measurement device that calculates the distance to the object to be measured based on the sum of the first distance measurement value and the corrected second distance measurement value. 7. The second level of the clamp signal in detecting the second distance measurement value is equal to or smaller than the first level of the clamp signal in detecting the first distance measurement value. The distance measuring apparatus according to claim 6. 8. A light projecting means for projecting a light beam toward the object to be measured, and reflecting light of the light beam projected on the object to be measured in accordance with a distance to the object to be measured. The light is received at the light receiving position on the position detection element, and based on the light receiving position, if the received light amount is constant, the far side signal is larger as the distance is longer, and if the received light amount is constant, the distance is closer A light receiving unit that outputs a near-side signal having a larger value, and receives the far-side signal and compares the level with a level of a clamp signal. If the level of the far-side signal is equal to or greater than the level of the clamp signal, Clamping means for outputting the far-side signal, and otherwise outputting the clamp signal, and calculating a ratio between the near-side signal and the signal output from the clamp means to output an output ratio signal Means for integrating the output ratio signal Integrating means for integrating and integrating the result of the integration, and outputting an integrated signal according to the integration result; light emission of the light beam by the light emitting means, level of the clamp signal by the clamp means, and output by the integration means. Control means for controlling each of the sums of the integration periods of the ratio signal and detecting a distance measurement value based on the integration signal output from the integration means, wherein: (a) the clamp signal Is set to a first level, and the sum of the integration period of the output ratio signal in the integration means is set to a first number, and a first distance measurement value is set based on the integration signal output from the integration means. (B) setting the clamp signal to a second level, and setting the sum of the integration periods of the output ratio signal in the integration means to a second number smaller than the first number Detecting a second distance measurement value based on the integration signal outputted from said integrating means Te, (c) the a second distance measurement value by adding a predetermined value the second
(D) setting the clamp signal to a third level; and setting the sum of the integration periods of the output ratio signal in the integration means to a third number smaller than the first number. Detecting a third distance measurement value based on the integration signal output from the integration means; and (e) adding a predetermined value to the third distance measurement value to obtain the third distance measurement value.
(F) based on the sum of the first distance measurement value and the corrected second distance measurement value, or based on the second distance measurement value and the corrected third distance measurement value. A distance measuring device that calculates a distance to the object to be measured based on a sum of distance measurement values. 9. The second level of the clamp signal in detecting the second distance value is equal to or smaller than the first level of the clamp signal in detecting the first distance value. 9. The method according to claim 8, wherein the third level of the clamp signal in detecting the third distance value is equal to or smaller than the first level of the clamp signal in detecting the first distance value. 3. The distance measuring device according to 1. 10. The predetermined value added for correcting the second distance measurement value and the predetermined value added for correcting the third distance measurement value are the same numerical value. , Claim 8
Or the distance measuring device according to 9.