JP3116510B2 - Focus information output device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus information output device used for a camera or a video camera.

[0002]

2. Description of the Related Art Cameras and video cameras equipped with an automatic focusing device (autofocusing device) for automatically adjusting the focus of a taking lens are known. The autofocus device includes a detection unit that detects a focus adjustment state of a photographic lens, and an adjustment unit that moves the photographic lens according to a detection result of the detection unit. There are roughly two detection methods in the detection unit. One is a distance measurement method that measures the distance to a subject by applying the principle of triangulation, and the other is a focus detection method that detects a focus adjustment state of a photographing lens. In the former ranging method, a pair of light beams that have passed through two lenses other than the photographing lens are formed on a pair of image sensors, and the distance to a subject is measured based on the amount of image shift on the image sensors. In the latter focus detection method, a pair of light beams from a subject passing through different regions of the photographing lens are formed on a pair of image sensors, and a photographing lens is formed based on the amount of image shift on the image sensors. To detect the defocus amount indicating the focus adjustment state.

Normally, a charge storage type light receiving element array is used in the above-mentioned image sensors, and charges are stored in accordance with the light intensity of a subject image formed on each image sensor to correspond to the light intensity distribution. Output the quantized data. For example, when one rod-shaped subject is measured for distance or focus is detected by a pair of image sensors arranged in parallel on the left and right with respect to the ground plane, the quantized data as shown in FIG. Is output. Noise such as dark current of the sensor itself is superimposed on these quantized data in addition to the signal corresponding to the subject image. In particular, when the ambient temperature is high and the subject brightness is low, the noise level increases, A large error occurs in the result of distance measurement or focus detection. In this specification, the measurement of the photographing distance by the distance measurement method and the detection of the defocus amount by the focus detection method may be referred to as distance measurement. Further, the distance measuring device and the focus detection device are referred to as a focus information output device.

In order to suppress the influence of the noise, there is a method of filtering the output data of the image sensor to remove the noise. For example, if each of the left and right sensors has n elements, the m-th left data DATAL (m)
And the m-th right data DATAR (m) are represented by the following equations, respectively. DATAL (m) = ｛DATAL (m-1) + Kf × DATAL (m) + DATAL (m + 1)｝ / (Kf + 2) ・ ・ ・ (1) DATAR (m) = ｛DATAR (m-1 ) + Kf × DATAR (m) + DATAR (m + 1)｝ / (Kf + 2) (2) Here, Kf is a constant of 1 or more. The filter effect becomes smaller as the value becomes larger than 1. If Kf is too small, the effect of data averaging is increased and fine pattern data is lost, which is inappropriate for a subject having such a fine pattern. That is, the constant Kf is set to an optimal value in consideration of the noise removal effect. FIG.
4 shows the data after the filter processing. Compared to FIG. 13, the high-frequency components are averaged, and the slope of the graph is gentle. Here, an example of filter processing for cutting relatively high frequencies has been described, but other various filter processing is also considered.

Next, a description will be given of a method for obtaining the photographing distance to the subject or the defocus amount of the photographing lens based on the image shift amount of the left and right sensor data after the filter processing, that is, the phase difference. Here, the left and right data strings are mutually shifted to obtain a correlation, and the photographing distance to the subject or the defocus amount of the photographing lens is detected from the shift amount indicating a high degree of correlation. That is, the calculated shift amount indicates the shooting distance to the subject in the distance measurement method, and indicates the defocus amount of the shooting lens in the focus detection method. First, the operation shown in the following equation is performed in a certain range (o
This is performed at an integer from ffset to offset + Ks (constant). f (shift) = Σ | DATAL (INT ((SL-shift) / 2) + i) -DATAR (INT ((SR + shift) / 2) + i)) | (3) where the function f (shift) represents the degree of correlation between the data of the left and right sensors, an operation for obtaining the function f (shift) is called a correlation operation, and f (shift) is called a correlation function. Σ is i = 0
(W-1) indicates the sum, and INT () indicates ()
Is a function that truncates the fractional part in and gives only the integer part. SL and SR are constants that determine the position of the region where the left and right correlations are made, respectively, and W is a constant that gives the width of the correlation region between the left and right data strings.

[0006] Also, the value of shift that gives the minimum or minimum value to the function f (shift), that is, shi indicating a high degree of correlation.
The value of ft is a value related to the shooting distance or the defocus amount, and is hereinafter referred to as a shift value. This shift value is
Since the value of ift is an integer, it is a discrete value in increments of one, but as shown in FIG. 15, based on the value of f (shift) in the vicinity where f (shift) is the minimum value or the minimum value. Interpolation is performed to find the value after the decimal point. Here, in the vicinity where the correlation function f (shift) takes a minimum value, the slopes L1 and L2 of f (shift) are calculated by the following equation. L1 = f (shift0) -f (shift0-1) (4) L2 = f (shift0 + 2) -f (shift0 + 1) (5) Note that L1 and L2 are also scales indicating the contrast of the subject. These values increase when distance measurement or focus detection of a high contrast object is performed. next,
The shift value Smin that gives the minimum value is given by the following equation. Smin = shift0 + {f (shift0 + 1) -f (shift0) -L2} / (L1-L2) (6) Further, the value of f (shift) when shift = Smin, that is,
The value of H shown in FIG. 15 is given by: H = f (Smin) = f (shift0) + L1 × {f (shift0 + 1) −f (shift0) −L2} / (L1−L2) (7) . This H indicates the magnitude of the degree of correlation between the left and right subject images, and the smaller the value H, the more the left and right images are correlated.

Here, the gradients L1 and L2 given by the above equations (4) and (5) are approximately equal even if their magnitudes are approximately equal.
In many cases, a sufficiently high interpolation accuracy can be obtained, and L = −L1 =
When L2, that is, when L = f (shift0−1) −f (shift0) = f (shift0 + 2) −f (shift0 + 1) (4) ′, the above equations (6) and (7) are obtained. Smin = shift0 + {f (shift0-1) -f (shift0 + 1)} / 2L (6) 'H = f (Smin) = f (shift0)-{f (shift0-1) -f (shift0 + 1) )｝ / 2 (7) 'Here, since the value of L1, L2, or the value of L and the value of H indicate the contrast of the subject and the degree of correlation between the left and right subject images, respectively, these two types are used. The reliability of the shift value obtained by the expression (6) or (6) ′ is determined based on the magnitude of the value of, and this value is used as a distance measurement result or a focus detection result or an erroneous measurement due to false focusing. It is determined whether the distance is determined. The value of L1, L2 or L is larger than a certain threshold value (the contrast of the subject is sufficiently high), and
When the value of H is smaller than a certain threshold value (the degree of correlation between the left and right subject images is sufficiently high), equation (6) is used, or
(6) Let Smin obtained by the equation be a shift value.

The shift value thus obtained is proportional to 1 / distance as shown in FIG. 11 in the case of the above-described distance measuring method. On the other hand, in the case of the focus detection method, the horizontal axis in FIG. 11 indicates the defocus amount of the photographing lens, and the photographing lens is in focus at a certain reference shift value (defocus amount 0).
At other times, the difference between the shift value and the reference shift value and the sign indicate the defocus amount of the photographing lens, that is, the defocus amount and the defocus direction indicating the front focus or the rear focus.

[0009]

As described above, in the conventional focus information output apparatus, as shown in FIG. 10, the dark current noise of the sensor increases when the ambient temperature is high, and the image of the object is particularly low when the luminance of the object is low. The noise component becomes relatively large with respect to the signal, causing an error in the distance measurement or focus detection result. Therefore, for example, in the filter processing of the above-described equations (1) and (2), when the constant Kf is reduced to increase the tendency of high-frequency cut and the filtering effect is increased, erroneous distance measurement is reduced. Since the information of the pattern is lost, it is unsuitable for a subject having a fine pattern.
The erroneous distance measurement that occurs at the time of high temperature and low luminance will be described in more detail. If the correlation operation is performed without sufficiently removing noise components such as dark current, other minimum values appear in addition to the minimum value corresponding to the subject image as shown in FIG. 17, for example, and a plurality of minimum values exist. There is. In FIG. 17, the minimum values Smin1 and Smin2 appear in addition to the shift value Smin3 of the subject. Here, if Smin1 or Smin2 is mistakenly set as the shift value, erroneous distance measurement occurs.

When the ambient temperature changes, the shift value of the correlation calculation result is changed by the temperature change of the optical system or the like as shown in FIG.
Changes as shown in FIG. The adjustment of the automatic focusing device is performed at a specific temperature. However, if the difference between the ambient temperature at the time of the adjustment and the ambient temperature at the time of use becomes large, the error of the shift value becomes a considerable amount. Further, when the correlation operation is performed in the range from offset0 to S4, if the shift value when measuring the infinite distance (corresponding to R0 in FIG. 11) at 20 ° C. is S2, the ambient temperature changes. When the temperature reaches 40 ° C., the shift value at the infinite distance R0 becomes offset0, and the correlation function f (shift) becomes a monotonically increasing function, making it impossible to obtain a minimum value. Also, (4) to (7)
In order to perform the interpolation calculation of the shift value of the equation or the equations (4) ', (6)', and (7) ', the function f near the minimum value is used.
(Shift) value is required. For this reason, in the correlation calculation range from offset0 to S4, distance measurement becomes impossible on the infinite side. Conversely, when the temperature is low (at 0 ° C. in FIG. 11), the same can be said on the close side, and the distance cannot be measured on the close side.

As described above, there is a problem that the shift value changes due to the temperature change, and further the range of the distance that can be measured changes.
This problem is caused by the correlation calculation range (offset 0 to S in FIG. 11).
If (4) is set to a value larger than this, the problem can be solved. However, the time required for the correlation calculation becomes longer, so that the value cannot be set too large.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a focus information output device which prevents a decrease in distance measurement performance and focus detection performance due to a change in ambient temperature.

[0013]

Means for Solving the Problems The invention of claim 1 will be described in association with FIG. 1 which is a claim correspondence diagram.
The present invention provides an optical system 1 for forming an image of a light beam from a subject on at least a pair of charge storage type light receiving element arrays 100 and 101.
02, which is applied to a focus information output device that performs focus detection based on output data of a pair of light receiving element arrays 100 and 101, and a temperature detection unit 103 that detects an ambient temperature. Storage time control means 104 for controlling the storage time of the charge storage type light receiving element arrays 100 and 101 in accordance with the ambient temperature, thereby achieving the above object. The invention of claim 2 will be described with reference to FIG. 2 which is a claim correspondence diagram. The invention of claim 2 is an optical system that forms a light beam from a subject on at least a pair of charge storage type light receiving element arrays 100 and 101. Having system 102;
A temperature detecting means 103 which is applied to a focus information output device which performs focus detection based on output data of a pair of light receiving element arrays 100 and 101 and detects an ambient temperature;
And filter means 105 for removing noise components included in the output data 0, 101.
Achieves the above object by changing the noise reduction rate according to the ambient temperature. Here, the noise reduction ratio indicates how much a high frequency component higher than a predetermined frequency is removed. The higher the noise reduction ratio, the higher the removal ratio. The invention of claim 3 will be described with reference to FIG. 5 which is a claim correspondence diagram. The invention of claim 3 is an optical system that forms a light beam from a subject on at least a pair of charge storage type light receiving element arrays 100 and 101. System 102
A correlation calculating means 106 for shifting the output data strings of the light receiving element arrays 100 and 101 to each other to calculate a correlation between the two data strings, and a maximum correlation based on the correlation calculated by the correlation calculating means 106. A maximum correlation value detecting means 107 for detecting the degree, a shift value detecting means 108 for detecting a shift value which is a shift amount when the maximum value is detected, and a focus information output device for performing focus detection based on the shift value. A temperature detection unit 103 that is applied and detects an ambient temperature, and according to the ambient temperature detected by the temperature detection unit 103,
Shift control means 111 for controlling the shift start position by changing the data to be compared first in the output data string by the correlation degree calculating means 106, thereby achieving the above object. Claim 4 corresponding to FIG. 5 which is a claim correspondence diagram.
According to the fourth aspect of the present invention, a light beam from a subject is converted into at least a pair of charge storage type light receiving element arrays 100,
An optical system 102 for forming an image on 101 and a light receiving element array 10
Correlation degree calculating means 106 for shifting the respective output data strings 0 and 101 to each other to calculate the degree of correlation between the two data strings, and a local maximum for detecting the maximum degree of correlation from the degree of correlation calculated by the degree of correlation calculation means 106 A correlation value detecting means 107, a shift value detecting means 108 for detecting a shift value which is a shift amount when a local maximum value is detected, and a focus information output apparatus for performing focus detection based on the shift value, and Temperature detecting means 103 for detecting the
And a correction means for correcting the shift value in accordance with the ambient temperature detected in step (3), thereby achieving the above object.

[0014]

According to the first aspect, the charge storage type light receiving element array according to the ambient temperature detected by the storage time control means.
The accumulation time of 0, 101 is controlled. According to the second aspect, the noise reduction rate to be removed is changed according to the ambient temperature detected by the filter means 105. According to the third aspect, the shift start position of the correlation degree calculating means is controlled according to the ambient temperature detected by the shift control means 111.
According to the fourth aspect, the shift value is corrected according to the ambient temperature detected by the correction unit 112.

[0015]

6 and 7 show the configuration of an embodiment in which the distance measuring device or the focus detecting device of the present invention is applied to a camera. As described above, a charge storage type light receiving element is used for the image sensor. There are several methods for quantizing the output value from each light receiving element. In this embodiment, two quantization methods will be described. FIG. 6 shows a configuration in which an output voltage corresponding to the amount of charge stored in each element of the image sensor is converted by an A / D converter. FIG. 7 shows that the output voltage of each element of the image sensor is a predetermined value. A configuration in a case where quantization is performed by measuring an accumulation time until the value becomes a value will be described. It is assumed that both the distance measuring method and the focus detecting method described above are applied to both the configurations of FIGS. 6 and 7, and the distance measuring optical system or the focus detecting optical system is not directly related to the present invention. Therefore, illustration and description thereof are omitted.

In FIG. 6, a CPU 1 comprises a microcomputer and its peripheral parts, performs sequence control of a camera, controls charge accumulation of an image sensor, and performs distance measurement calculation or focus detection calculation based on output data thereof. Perform The CPU 1 is connected to an image sensor 2 and a temperature detection circuit 3 for detecting the temperature of the camera. The image sensor 2 starts accumulating the electric charge according to the accumulation start signal of the CPU 1, and ends the accumulation according to the accumulation end signal of the CPU 1 after a predetermined time from the start of the accumulation. When the accumulation is completed, the CPU 1 reads out the accumulated charges, that is, the sensor data, from each element of the image sensor 2, performs A / D conversion and performs a correlation operation, and calculates a shooting distance or a defocus amount. Further, the temperature detection circuit 3 detects the ambient temperature of the camera at a necessary timing according to an instruction from the CPU 1, and the CPU 1 reads the detection result and performs A / D
Convert.

In FIG. 7, a CPU 1A comprises a microcomputer and its peripheral parts, controls the sequence of the camera, controls the charge accumulation of the image sensor, and calculates the distance or focus based on the output data. Perform The CPU 1A is connected to an image sensor 4 and a temperature detection circuit 3 for detecting the temperature of the camera. The image sensor 4 is an IC that measures the accumulation time until the accumulated charge of each element reaches a predetermined voltage and performs quantization. The accumulation is started by the accumulation start signal of the CPU 1A, and the first element reaches the predetermined voltage. The response signal A is output at the time, and the response signal B is output when all the elements reach the predetermined voltage or when a predetermined time has elapsed from the output of the response signal A. When the response signal B is output, C
The sensor data is read by the PU 1A, and the shooting distance or the defocus amount is calculated by the correlation operation. The temperature detection circuit 3 is the same as the circuit shown in FIG.
The temperature of the camera is detected at a necessary timing according to the instruction of PU1A.

FIGS. 8 and 9 are flowcharts showing the operation of the embodiment shown in FIG. First, in step S101, the accumulation time Ts is set based on the photometric value. In general, the charge accumulation time is often set based on the photometry result. For example, when the subject is bright, the accumulation time is set short, and when the subject is dark, the accumulation time is set long. In the present embodiment, description will be made on the assumption that a photometric value has already been given by a photometric circuit (not shown). In the following step S102, the ambient temperature is detected, and the detection result is set to t. In step S103, a limit Tlim of the accumulation time is set based on the ambient temperature t. The accumulation time limit Tlim is
When the noise level due to the dark current of the charge storage type light receiving element is low, the value is set to a long value when the temperature is low, and when the noise level is high, the value is set to be short when the noise level is high.

FIG. 10 shows the limit Tlim of the accumulation time with respect to the ambient temperature t. Limit Tlim indicated by dotted line
Is a value corresponding to each temperature region when the ambient temperature t is divided into three temperature regions of low temperature, medium temperature, and high temperature. In addition,
The method of dividing the temperature region is not limited to this embodiment. For example, the temperature region may be divided into two regions, that is, a region at a high temperature and another region, or four or more regions. Further, the limit Tlim may be set continuously according to the ambient temperature t as shown by a solid line.

In step S104 of FIG. 8, an accumulation start signal is output from the CPU 1 to the image sensor 2 to start the accumulation of electric charges. In step S105, it is determined whether or not the accumulation time Ts has elapsed. Step S107
If not, the process proceeds to step S106.
In step S106, it is determined whether or not the limit Tlim of the accumulation time has elapsed.
07, and if not passed, returns to step S105. Note that these times Ts and Tlim are determined in step S1.
This is the elapsed time from the start of the charge accumulation in 04.
Next, in step S107, an accumulation end signal is output from the CPU 1 to the image sensor 2 to end the accumulation. By performing the processing from steps S101 to S107, the storage time limit Tlim is set shorter according to the ambient temperature t when the temperature is high and longer when the temperature is low, and the accumulation is not performed for the set time limit or longer. I have. As a result, the dark current noise is suppressed to be low at high temperatures, erroneous distance measurement is reduced, and the distance of a darker subject can be measured at low temperatures.

After the storage is completed in step S107, the output values of the respective elements of the image sensor 2 which are stored in step S108 are read out, quantized, and step S1 is performed.
Go to 09. In step S109, it is determined whether or not the ambient temperature t is lower than 10 ° C. If the temperature is lower than 10 ° C, the process proceeds to step S111 to perform the first filter processing and perform the first filter processing.
If so, the process proceeds to step S110, where the detected temperature t is 3
It is determined whether the temperature is lower than 0 ° C. If the temperature is lower than 30 ° C., the process proceeds to step S112 to perform the second filter processing. If the temperature is 30 ° C. or higher, the process proceeds to step S213 and the third filter process is performed.
Is performed.

Here, the third filter processing at the time of high temperature is performed based on the second filter processing at the time of medium temperature, and has a higher noise removing effect. The first filter processing at the time of low temperature is performed. , A filter process having a lower noise removal effect is performed based on the second filter process at the medium temperature. For example, the value of the constant Kf in the above equations (1) and (2) is set to 3, 2, and 1 by the first, second, and third filter processes, respectively, and (8), (9),
The filter processing represented by the equations (10), (11), (12), and (13) is performed. DATAL (m) = ｛DATAL (m-1) + 3 × DATAL (m) + DATAL (m + 1)｝ / 5 (8) DATAR (m) = ｛DATAR (m-1) +3 × DATAR (m) + DATAR (m + 1)｝ / 5 ・ ・ ・ ・ (9) DATAL (m) = ｛DATAL (m-1) + 2 × DATAL (m) + DATAL (m + 1)｝ / 4 ・ ・ ・ (10) DATAR (m) = ｛DATAR (m-1) + 2 × DATAR (m) + DATAR (m + 1)｝ / 4 ・ ・ ・ (11) DATAL (m) = ｛DATAL ( m-1) + DATAL (m) + DATAL (m + 1)｝ / 3 ・ ・ ・ (12) DATAR (m) = ｛DATAR (m-1) + DATAR (m) + DATAR (m + 1)｝ / 3 (13) In the present embodiment, the temperature is divided into three temperature regions of low temperature, medium temperature, and high temperature in accordance with the ambient temperature t, and filter processing with a different noise reduction rate is performed for each temperature region. However, the number of divisions of the temperature region is not limited to the present embodiment. For example, the temperature region may be divided into two regions, that is, a high temperature region and other regions, or may be divided into four or more regions and appropriate filter processing may be performed in each temperature region. Good, or the constant Kf of the equations (1) and (2) is continuously set according to the ambient temperature t. Unishi may be.

Next, steps S111, S112, S1
Upon completion of each filter process in step 13, the process proceeds to step S201 in FIG. 9, and the correlation start position offset is calculated and set by the following equation. offset = INT {offset0 + Kt × (t−20)} (14) where offset0 is a certain reference temperature (here, 20
℃) to ensure distance measurement of subjects at infinity of
fset value, t is the ambient temperature detected in step S102, and Kt is a temperature coefficient representing a change amount of the shift value when the temperature rises by 1 ° C. In the following step S202, the variable shift is set to a certain range from offset (offset to of
fset + Ks (constant)), the operation of the expression (3) is performed, and the operations of the expressions (4) to (7) or the operations of the expressions (4) ′, (6) ′, and (7) ′ are performed. Thus, the shift value Smin and L and H representing the reliability thereof are obtained.

Here, the relationship between the shift value and the photographing distance when the ambient temperature t is used as a parameter will be described with reference to FIG. As described above, the start position of the correlation calculation, that is, the shift start position of the output data of the pair of image sensors is set in accordance with the ambient temperature, so that the calculation range of the correlation calculation (the range in which the variable shift changes) is Off at 20 ° C
From set0 to S4 (= offset0 + Ks), S at 40 ° C
From 1 to S3 (= S1 + Ks), and at 0 ° C., from S2 to S5 (= S2 + Ks). The shooting distance corresponding to each calculation range is affected even when the ambient temperature changes. It is possible to always measure the distance from R1 to R5. Furthermore, since the range in which the variable shift of the correlation function f (shift) changes is always Ks, the calculation amount of the correlation calculation is constant and the calculation time is constant.

Next, in step S203 of FIG. 9, it is determined whether or not the ambient temperature t is lower than 10 ° C. If it is lower than 10 ° C., the process proceeds to step S205, otherwise, the process proceeds to step S20.
Proceed to 4. In step S204, it is determined whether or not the ambient temperature t is lower than 30 ° C.
6; otherwise, to step S207. In steps S205 to S207, the above-described step S202
In order to judge the reliability of the shift value Smin obtained in the above, the judgment standards Hlim and Llim are set according to the ambient temperature t. These criteria Hlim and Llim are set broadly when the ambient temperature t is 10 ° C. or higher and lower than 30 ° C. and when the temperature is low, and are stricter when the temperature is high. In other words, at high temperatures where the influence of sensor data noise is large, the criterion is stricter to prevent erroneous distance measurement due to noise. Conversely, at low temperatures with less sensor data noise, the criterion is broadened to measure low-contrast subjects. It can be so. In the present embodiment, the temperature area is divided into three temperature areas of low temperature, medium temperature, and high temperature in accordance with the ambient temperature t, and the criterion is set for each temperature area. However, the method of dividing the temperature area is limited to this embodiment. Alternatively, for example, an appropriate determination criterion may be set in each temperature region by dividing into two regions, that is, a high temperature region and other regions, or four or more regions, or the determination criterion may be continuously determined according to the ambient temperature t. You may make it set dynamically.

In steps S208 and S209 after the determination criteria Hlim and Llim are set, it is determined whether or not the distance measurement has been performed based on the set determination criteria. If the determination criteria are not satisfied, the process proceeds to step S210 to disable the distance measurement. age,
All processing ends. Step S208, S209
If the determination criterion is satisfied, the process proceeds to step S211 to enable distance measurement, and the temperature of the shift value is corrected in step S212. This temperature correction process is performed in step S20.
The following calculation is performed on the shift value Smin calculated in step 2. Shift value = Smin−Kt × (t−20) (15) where t is the ambient temperature detected in step S102,
Kt is a temperature coefficient representing the amount of change in the shift value when the temperature rises by 1 ° C. By this processing, a constant shift value is always obtained even when the ambient temperature t changes. After this temperature correction processing, all processing ends.

FIG. 12 is a flowchart showing the operation of the embodiment circuit shown in FIG. First, in step S301, the ambient temperature t is detected, and in the following step S302, a limit Tlim of the accumulation time is set according to the ambient temperature t. As shown in FIG. 10, the limit Tlim of the accumulation time is set to a long value at a low temperature when the noise level due to the dark current of the charge accumulation type light receiving element is small, and is set to a short value at a high temperature at which the noise level becomes large. I do. As described above, the temperature is divided into three temperature regions of low temperature, medium temperature, and high temperature in accordance with the ambient temperature t, and the accumulation time limit Tlim indicated by a dotted line is set for each region. As described above, the accumulation time limit Tlim is set to be short at high temperatures and long at low temperatures, and the accumulation is not performed for more than the set limit Tlim time. As a result, dark current noise is reduced at high temperatures. Incorrect distance measurement is prevented, and at low temperatures, a dark subject can be measured. The method of dividing the temperature region is not limited to the present embodiment. For example, the temperature region may be divided into two regions, that is, a high temperature region and other regions, or four or more regions, or may be continuously formed according to the ambient temperature t. Storage time limit Tlim
May be set.

Next, in step S303, an accumulation start signal is output from the CPU 1A to the image sensor 4 to start charge accumulation. In a succeeding step S304, the image sensor 4
By monitoring the response signal A, it is determined whether or not the output of any of the elements has reached a predetermined voltage. If the output has reached the predetermined voltage, the process proceeds to step S305, and if not, the process proceeds to step S306. In step S306, it is determined whether or not the limit Tlim time set in step S302 has elapsed. If the limit Tlim has elapsed, the process proceeds to step S308, in which distance measurement is disabled, and all processing ends. On the other hand, the limit Tli
If m hours have not elapsed, the process returns to step S304.
The limit Tlim time is an elapsed time from the accumulation start time in step S303. Step S304
When it is determined that the output of any one of the elements has reached the predetermined voltage, the process proceeds to step S305, where the response signal B is monitored to determine whether the outputs of all the elements have reached the predetermined voltage, or the response signal A is output. It is determined whether or not a predetermined time has elapsed since then, and the process waits until one of the determination conditions is affirmed. Either the output of all elements has reached the predetermined voltage or the response signal A
When the response signal B is output after a predetermined time has elapsed from the output of the image sensor 4, the sensor data quantized by the image sensor 4 is read. Thereafter, the process proceeds to step S109 in FIG. 8 to continue the above-described processing.

In the configuration of the above embodiment, the image sensors 2 and 4 use the charge storage type light receiving element array as the temperature detection circuit 3
Is a temperature detecting means, a microcomputer (CPU)
1, 1A respectively constitute an accumulation time control means, a filter means, a correlation degree calculation means, a maximum correlation value detection means, a shift value detection means, a reliability judgment means, a contrast calculation means, a shift control means and a correction means.

[0030]

As described above, according to the first aspect of the present invention, the accumulation time of the charge accumulation type light receiving element array is controlled in accordance with the ambient temperature. Noise and the like can be reduced, distance measurement accuracy and focus detection accuracy can be improved, and distance measurement and focus detection can be performed on a darker subject that could not be measured conventionally at low temperatures. According to the second aspect of the present invention, the noise reduction rate to be removed is changed in accordance with the ambient temperature, so that a more appropriate filter processing than in the past in which the filter processing with a high noise reduction rate is performed regardless of the ambient temperature. This makes it possible to prevent erroneous distance measurement due to noise, and also enables distance measurement and focus detection for a darker object that could not be measured conventionally at low temperatures. According to the third aspect of the present invention, the shift start position is controlled in accordance with the ambient temperature, so that distance measurement and focus detection in a predetermined range can be always performed even when the ambient temperature changes. Further, according to the invention of claim 4, since the shift value is corrected in accordance with the ambient temperature, a distance measurement error and a focus detection error caused by a temperature change of the optical system and the like are reduced, and the ambient temperature changes. However, it is possible to maintain constant ranging performance and focus detection performance.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims.

FIG. 2 is a diagram corresponding to claims.

FIG. 3 is a diagram corresponding to claims.

FIG. 4 is a diagram showing a configuration of one embodiment.

FIG. 5 is a diagram showing a configuration of one embodiment.

FIG. 6 is a flowchart showing the operation of the embodiment shown in FIG. 6;

FIG. 7 is a flowchart showing the operation of the embodiment shown in FIG. 6;

FIG. 8 is a diagram showing a relationship between an ambient temperature and a limit value of an accumulation time.

FIG. 9 is a diagram illustrating a relationship between a shift value and a shooting distance when ambient temperature is used as a parameter.

FIG. 10 is a flowchart showing the operation of the embodiment shown in FIG. 7;

FIG. 11 is a diagram showing output data of a pair of image sensors.

FIG. 12 is a diagram showing output data of a pair of image sensors after filtering.

FIG. 13 is a diagram illustrating an interpolation calculation of a shift value.

FIG. 14 is a diagram showing the relationship between the ambient temperature and the amount of dark current noise of the image sensor.

FIG. 15 is a diagram illustrating a correlation calculation result when a plurality of minimum values exist.

[Explanation of symbols]

 Reference Signs List 1, 1A microcomputer (CPU) 2, 4 image sensor 3 temperature detection circuit 100, 101 light receiving element array 102 optical system 103 temperature detection means 104 accumulation time control means 105 filter means 106 correlation degree calculation means 107 maximum correlation value detection means 108 Shift value detection means 111 Shift control means 112 Correction means

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-166509 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02B ⁷ /28-7/40 G03B 3 / 00-3/12

Claims (4)

(57) [Claims] 1. A focus information output device, comprising: an optical system for forming an image of a light beam from a subject onto at least a pair of charge storage type light receiving element rows, and performing focus detection based on output data of the pair of light receiving element rows. A focus detecting means for detecting an ambient temperature; and a storage time controlling means for controlling a storage time of the charge storage type light receiving element array according to the ambient temperature detected by the temperature detecting means. Information output device. 2. A focus information output device comprising: an optical system for forming an image of a light beam from a subject onto at least a pair of charge storage type light receiving element arrays, and performing focus detection based on output data of the pair of light receiving element arrays. A temperature detecting unit for detecting an ambient temperature; and a filter unit for removing a noise component included in each output data of the light receiving element array, wherein the filter unit removes a noise component according to the ambient temperature. The focus information output device characterized by changing. 3. A luminous flux from a subject is converted into at least a pair of electric charges.
The optical system for forming an image on the storage type light receiving element array and the output data strings of the light receiving element array are shifted from each other to
A correlation degree calculating means for calculating the degree of correlation of the data sequence, and a maximum value based on the correlation degree calculated by the correlation degree calculating means.
A maximum correlation value detection means for detecting a degree of correlation , and a shift value which is a shift amount when the maximum value is detected.
And a shift value detecting means for detecting the focus information output for performing focus detection based on said shift value
In the device, a temperature detection means for detecting the ambient temperature, depending on the ambient temperature detected by the temperature detecting means, wherein
The comparison is made at the beginning of the output data sequence by the correlation degree calculating means.
Shift system that controls shift start position by changing data
And a focus information output device. 4. The method according to claim 1, wherein the luminous flux from the subject is converted into at least one pair of electric charges.
The optical system for forming an image on the storage type light receiving element array and the output data strings of the light receiving element array are shifted from each other to
A correlation degree calculating means for calculating the degree of correlation of the data sequence, and a maximum value based on the correlation degree calculated by the correlation degree calculating means.
A maximum correlation value detection means for detecting a degree of correlation , and a shift value which is a shift amount when the maximum value is detected.
And a shift value detecting means for detecting the focus information output for performing focus detection based on said shift value
In the device, in accordance with the temperature detection means for detecting the ambient temperature, ambient temperature detected by the temperature detecting means and the sheet
Correction means for correcting the shift value.
Focus information output device.