JPH10122855A - Rangefinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rangefinder for accurately rangefinding even when a flare is incident. SOLUTION: The rangefinder used for an automatic focus regulator for focusing an optical equipment by detecting relative interval of first and second subject images formed of luminous fluxes from the subjects passed through a pair of lenses disposed at a predetermined interval comprises a means for correcting influence of noise due to a flare caused by 'stray light' superposed on at least obtained first or second subject image in accordance with the prescribed method and procedure (S1-S24). In the case of quantizing the image as an image signal by a line sensor due to the noise caused by external factor of sensing noise, it is corrected with respect to the stray light superposed on the image. Further, it is also corrected with respect to not only uniform stray light but also stray light having a gradient.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring apparatus for measuring a distance to a subject and automatically adjusting the focus of, for example, an optical device according to the distance.

[0002]

2. Description of the Related Art Conventionally, noise caused by an external factor among sensing noises in an automatic focusing device, which is superimposed on a subject image when the subject image is quantized as an image signal by a line sensor. Have been disclosed. As one such prior art, there is correction of "flare" which is one of stray light as disclosed in Japanese Patent Application Laid-Open No. 5-264892. JP-A-5
The content disclosed in Japanese Patent Application Laid-Open No. 264892 will be briefly described below. When a subject image is obtained as a first image signal and a second image signal as shown in a graph of FIG.
If the difference between the sum of the first image signal amount and the sum of the second image signal amount, that is, the area: S (1) and the area: S (2) in FIG. The average value of the image signal amount of
7, that is, the difference between AVE (1) and AVE (2) in FIG. 7 as a correction value, the smaller of the image signal amounts, ie, the first image in FIG. The flare is corrected by uniformly adding Δ to the signal.

[0003] In addition, a description will be given based on the respective graphs in the upper, middle, and lower stages of FIG. 8 showing an example of an image signal. This shows a case where noise is present.
Note that all the noise in FIG. 8 is illustrated as being superimposed only on the second image signal. In the case where there is no noise shown in the upper part, but in the case where there is uniform noise shown in the middle part, the second image signal (1) is superimposed with the noise (2) and is superimposed on the second image signal (2). Become. When the second image signal (1) and the second image signal (2) are compared, no lateral displacement occurs. That is, in the case of a uniform noise such as the noise (2), it does not affect the relative image interval of the image signal, and does not become an error in focus adjustment in principle. But,
The noise (2) affects the reliability of the relative image interval of the image signal calculated by the correlation operation and lowers the reliability. If the reliability is low, the repetition reproducibility deteriorates and a repetition error occurs, resulting in a focus adjustment error. Noise in reality
Examples such as (2) are rare, and errors in focus adjustment are insignificant. In such a case, if the correction method according to the prior art is applied, the noise (2) is corrected and the error of the focus adjustment is improved, and thus the correction according to the prior art is effective.

[0004]

However, in the case where noise having a gradient shown in the lower part of FIG. 8 exists, the second image signal (1) is superimposed with the noise (3) and the second image signal (1) is superimposed on the second image signal (1). Image signal (3). Comparing the second image signal (1) and the second image signal (3), the positions of the maximum value and the minimum value have moved as shown by arrows A, B, and C, and the second
Is shifted rightward with respect to the second image signal (1). In other words, in the case of noise having a gradient such as noise (3), it affects the relative image interval of the image signal, and also reduces the reliability of the correlation operation.
Causes large errors in focusing. In such a case, noise (3)
Is incomplete, and the focus adjustment error cannot be improved. At best, the reliability of the correlation operation is slightly improved. Therefore, in this case, the correction according to the related art is not effective.

As described above, in the prior art, it can be said that the correction of noise having a low frequency of occurrence and having a small influence is effective, but the noise having a high frequency of occurrence and having a large influence has almost no effect. . The distance measuring apparatus of the present invention has been made in view of such a problem, and an object of the present invention is to provide a distance measuring apparatus capable of measuring a distance with high accuracy even when a flare is incident.

[0006]

Accordingly, the present invention takes the following measures in order to solve the above-mentioned problems and achieve the object. The distance measuring apparatus according to the present invention detects, for example, a relative image interval between first and second object images formed by light beams from an object passing through a pair of lenses arranged at a predetermined interval. A distance measuring device that can be used for, for example, an automatic focusing device that performs focusing of a predetermined optical device, and corrects the influence of noise due to stray light superimposed on the first and second subject images based on a predetermined method. It is a distance measuring device provided with means. Further, in the distance measuring apparatus of the present invention, stray light superimposed on the subject image when the subject image is quantized as an image signal by the line sensor is corrected by noise due to an external factor in the sensing noise. Is what you do. Further, it is possible to effectively correct not only uniform stray light but also stray light having a gradient, so that a distance measuring device used for a high-precision automatic focusing device of an optical device such as a camera can be effectively used. An apparatus is provided.

More specifically, [1] optical means for receiving a light beam from an object and splitting the light beam into a pair of light beams separated by a predetermined distance, and disposed substantially at an image forming position of the pair of light beams, A light-receiving element array having a pair of light-receiving sections and outputting a pair of image signals relating to the object; a storage unit for storing a correction value for correcting a sensitivity variation unique to the pair of light-receiving elements; Means for detecting a noise signal component contained in one of the image signals equivalently by correcting the pair of image signals using a value, and comparing the corrected image signals with each other; and Calculating means for removing the noise signal component, and calculating a distance to the object based on a mutual interval between the pair of image signals after the noise removing calculation. provide. [2] The distance measuring apparatus according to [1], wherein the noise signal component detection unit sets a regression line by a “least square method” based on the two image signals after the sensitivity variation correction. .

[0008]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a conceptual diagram illustrating the signal processing method of the present invention in a graph. A first image signal having a graph curve as shown in FIG.
When the noise component (that is, the stray light component) indicated by oblique lines is superimposed on the second image signal, the present invention corrects the first image signal as indicated by dotted lines, The focus adjustment is performed with high precision.

FIG. 2 shows a basic structure of a sensor and an optical system constituting the distance measuring apparatus in the present embodiment. Line sensor (L) 1a and line sensor (R) 1b
Is a line sensor composed of a number of segments, and an optical system (L) 2a composed of a convex lens or the like and an optical system
(R) 2b face each other as a pair of left and right, and receive a light beam from an object (not shown) focused by each convex lens as an object image in a planar manner. The left and right optical axes are arranged at a predetermined interval (that is, the distance of the base line length). The characteristics of the pair of left and right line sensors 1a and 1b are basically the same, and the same is adopted for the optical system. Therefore, normally, a light beam from a subject alone is detected with equal sensitivity. When the same subject is observed from different positions by a predetermined interval by a pair, the shapes of the obtained subject images are slightly different, and accordingly, the signals generated respectively are also slightly different.

The luminous flux from the object is transmitted to a line sensor (L) 1a by an optical system (L) 2a and an optical system (R) 2b.
A first subject image and a second subject image are formed on the line sensor (R) 1b. Based on these images,
Line sensor (L) 1a and line sensor (R) 1b
Respectively quantizes as a first image signal and a second image signal, and senses a signal necessary for focus adjustment control of an optical device such as a camera.

Further, since the line sensor (L) 1a and the line sensor (R) 1b are divided into a plurality of blocks, a relative image interval of the subject image with respect to a plurality of subjects is calculated. It is also possible to perform focus adjustment based on

Next, FIG. 3 illustrates a circuit block diagram of the distance measuring apparatus according to the present embodiment. A portion indicated by a dashed line in the figure for performing the automatic focus adjustment is a chip called an AFIC (autofocus IC) 4 which is formed of, for example, one IC chip. The AFIC 4 includes a sensor control and signal processing circuit 3, a line sensor (L) 1a and a line sensor (R) 1b, and is electrically connected bidirectionally. Further, the sensor control and signal processing circuit 3
The CPU 5 is connected to a CPU 5 provided outside the AFIC 4, and the CPU 5 is connected to an EEPROM 6.

The AFIC 4 mainly performs sensing processing of the subject image, and the CPU 5 calculates the "stray light correction" and the relative image interval of the subject image, which are the features of the present invention, based on the sensed data signal. , Image signal correction,
Other corrections and predetermined control of an actuator or the like related to focus adjustment of a camera or the like are performed. Also, E
The EPROM 6 functions as means for storing and holding various data such as correction data of the image signal. The characteristic control of the embodiment of the present invention is mainly performed inside the CPU 5 based on execution of a later-described predetermined program. In the distance measuring apparatus according to the present invention having the above-described component configuration and circuit configuration, "correction of stray light" which is a feature of the present invention as described below is executed.

It is assumed that the distance measuring apparatus of the present invention having the configuration shown in FIGS. 2 and 3 has obtained a first image signal and a second image signal as shown in FIG. At this time, the stray light, which is noise superimposed on the second image signal, is a portion indicated by a dotted line in FIG. 4, and after this noise component is detected by the detection means, the stray light is detected based on the above-described program. This is to correct the image signal correctly by a predetermined correction method. If the correction method is conceptually and simply described with a graph, a signal obtained by subtracting the second image signal from the first image signal is generated as shown by a graph curve in FIG. Next, a regression line as shown in FIG. Then, the data represented by the obtained regression line is used as correction data for correcting included noise components.

The detailed correction method will be sequentially described below with reference to the flowchart of FIG. First, a subroutine "initialization of AFIC" is executed (S1). Specifically, the line sensor (L) 1a and the line sensor (R)
Reset of 1b, reset of the sensor control and signal processing circuit 3, setting of sensor sensitivity, setting of sensor mode, and the like are performed.

Next, a subroutine "quantization of subject image"
, The subject image is quantized (S2). That is, the AFIC 4 is controlled from the start of signal integration to integration monitoring and integration end. In some cases, the signal integration is forcibly terminated.

Subsequently, a subroutine "read / store" for reading out the first image signal and the second image signal quantized in the above step S2 from the AFIC 4 and storing them in the RAM in the CPU 5 is executed (S3). Note that R
The AM is a first storage unit, and refers to a RAM of the RAM provided in the CPU 5 to which a predetermined storage area is allocated.

Here, in step S4, a line sensor
(I) A variable i indicating a “sensor address” (corresponding to a plurality of continuous blocks) of the (L) 1a and the line sensor (R) 1b, or variables x and xx, which are intermediate data for obtaining a regression line equation. , Y, and xy are substituted with 0 or the like, reset, and initialized in advance (S4).

Next, in step S5, the sensor address i is incremented and the sensor address is shifted one by one (S5). Difference data obtained by subtracting the second image signal amount from the first image signal amount is generated as a variable Δ (that is, Δ (i)) (S6).

In the following steps S7 to S10, calculations based on the respective equations as shown in the flowchart are respectively performed, and intermediate data for obtaining a regression line equation described later is prepared. That is, the line sensor address (i)
The difference data Δ (i) of the unit is totalized (S7, S
8, S9, S10). Then, in step S11, the sensor address i is the last address n of the sensor address.
(Or the total number of unit sensors constituting the line sensor) is determined, and during the period of i <n, the process returns to step S5 to perform the calculation for summing the intermediate data of the regression line equation. The processing is executed in the loop processing composed of steps S5 to S10, and when i = n, it means that the calculation regarding the image signals (that is, sensor data) for all the sensors of the line sensor has been completed. The processing exits from the loop processing and proceeds to the next step S12.

The following steps S12 to S15 are processing steps for obtaining b representing the slope of the linear equation, which is a parameter of the equation of the regression line, and a representing the Y-intercept. (S1
2, S13, S14, S15).

Next, in step S16, the sensor address i is reset to 0 again (S16), and a preparation is made for the subsequent loop processing of steps S17 to S22. Step S17
Then, the sensor address i is incremented by one, and the sensor address is shifted one by one (S17). In step S18, the value of the regression line corresponding to the sensor address i, that is, the detection value of the stray light component that is noise, or
A correction value for stray light is obtained (S18). Step S19
Then, the process branches to the next step depending on whether the correction value for the stray light obtained in step S18 is a positive or negative value. If this correction value is a negative value, step S
20 and subtracts the correction value from the first image signal (S2).
0). On the other hand, if the value is a positive value, the process proceeds to step S21,
A correction value is added to the second image signal (S21).

Step S22 is the same as step S11 described above.
Similarly to the above, it is determined whether or not the sensor address i is equal to the last address n of the sensor address (or the total number of unit sensors of the line sensor). If i <n, the process returns to step S17, and loop processing is executed in steps S17 to S21 in which the correction of the first image signal or the second image signal is repeated. When i = n, it is determined that the correction has been completed as needed for the image signals (that is, sensor data) for all the sensors of the line sensor, and the process exits from the loop processing and proceeds to the next step S23. .

Here, the storage destinations of the first image signal and the second image signal read out in step S3, and the first image signal and the second image corrected in step S20 and step S21. The storage destination of the signal is separately set (for example, R and R as the main storage area of the EEPROM and the CPU).
If the AM is provided, the first storage holding means and the second storage holding means exist independently. On the other hand, if these are combined, the first storage and holding means and the second storage and holding means will be common.

After exiting the loop processing in step S22, in step 23, a subroutine "correlation / interpolation operation" for calculating a relative image interval between the first image signal and the second image signal is executed (step 23). S23). The method of calculating the relative image interval and the like may be performed by applying a technique of the related art, and a detailed description thereof will be omitted. Finally, a subroutine "data conversion" is executed to execute an operation for adjusting the focus of the optical system or the like using the calculated data (S24). This conversion method and the like may be performed by applying a technique of the related art, and thus the detailed description thereof will be omitted.

The embodiment described above has been described in detail mainly on the "stray light correction" which is the gist of the present invention. Therefore, the description is omitted for the essential items in the focus adjustment of a camera or the like, for example, in which the distance measuring device will be used. Among them, items related to the present invention are determined by the distance measuring device. The converted data (including the control signal) can be provided as a parameter to the drive system for controlling the optical system by using a conventional technique for focusing at the time of automatic focus adjustment in the camera.

(Modification) In the distance measuring apparatus according to the present invention,
The detecting means for detecting the noise signal component may set a regression line by the “least square method” based on the two image signals after the sensitivity variation correction. In the above-described embodiment, the sensor data is programmed to be always corrected. However, for example, when the inclination or the Y intercept of the obtained regression line is within a predetermined range, the correction is not necessarily performed. The processing may be performed without correction.

Further, depending on the state of the image signal (for example, low contrast), it may not be necessary to obtain even the equation of the regression line. Therefore, according to the omission of such substantially unnecessary operation processing steps, simple and quick ranging can be performed. (Other Modifications) Various modifications can be made without departing from the gist of the present invention.

Although the embodiments have been described above, the present invention includes the following inventions. [1] An optical unit for receiving a light beam from an object and dividing the light beam into a pair of light beams separated by a predetermined distance, and a pair of light receiving units substantially arranged at an image forming position of the pair of light beams. A light-receiving element array that outputs a pair of image signals relating to the object; a storage unit that stores a correction value for correcting a sensitivity variation unique to the pair of light-receiving element rows; and the pair using the correction value. Means for equivalently detecting a noise signal component included in one of the image signals by correcting the image signals of the above, and comparing the image signals after the correction, and removing the detected noise signal component. Calculating means for calculating the distance to the object based on the mutual interval between the pair of image signals after the noise removal calculation.

[2] The noise signal component detecting means:
The distance measuring apparatus according to [1], wherein a regression line based on the least squares method is set based on the two image signals after the sensitivity variation correction.

In addition, the present invention includes the following invention. (1) A distance measuring device that detects a subject distance based on a relative image interval between first and second subject images formed by light fluxes (from) passing through a pair of lenses arranged at a predetermined interval. , A first line sensor that receives a first subject image and outputs a first image signal, a second line sensor that receives a second subject image and outputs a second image signal, A first storage unit for storing the first and second image signals; an image signal subtraction unit for generating a signal obtained by subtracting the second image signal from the first image signal; and the image signal subtraction unit. Linear approximation means for obtaining a regression line of the generated signal; and the first and second regression lines determined by the linear approximation means as image signals based on stray light components included in the first and second image signals. Image signal correcting means for correcting an image signal; A second memory holding means for storing and holding the first and second image signal corrected by means,
Correlation calculating means for calculating a relative image interval of the subject image based on the first and second image signals corrected by the image signal correcting means, and a relative image of the subject image calculated by the correlation calculating means A data conversion unit for generating information necessary for focus adjustment based on the interval.

(2) When the value of the regression line obtained by the linear approximation means is negative, the image signal correction means adds the absolute value of the correction value to the first image signal, and The distance measuring apparatus according to (1), wherein when the obtained value of the regression line is positive, a correction value is added to the second image signal.

(3) The first line sensor and the second line sensor are divided into a plurality of blocks, and a relative image interval of a subject image calculated for each block, or calculation for one selected block. The distance measurement apparatus according to (1), wherein information necessary for adjusting the focus of the camera is generated based on a relative image interval of the subject image to be performed.

(4) The distance measuring apparatus according to (1), wherein the first storage unit and the second storage unit are common. Further, the following inventions are also included.

(1 ') The focus of the camera is detected by detecting the relative image distance between the first and second object images formed by the light beams from the object passing through a pair of lenses arranged at a predetermined interval. An automatic focus adjustment device for a camera for generating information necessary for adjustment and adjusting the focus of the camera.
A first line sensor for receiving a subject image and outputting a first image signal; a second line sensor for receiving a second subject image and outputting a second image signal; First storage and holding means for storing and storing the image signal, image signal subtracting means for generating a signal obtained by subtracting the second image signal from the first image signal, and a regression line of the signal generated by the image signal subtracting means Signal correction for correcting the first and second image signals by using the linear approximation means for obtaining the first and second image signals as the image signals due to the stray light components included in the first and second image signals. Means, second storage and holding means for storing and holding the first and second image signals corrected by the image signal correcting means, and based on the first and second image signals corrected by the image signal correcting means. , Correlation calculation to calculate relative image spacing of subject images Automatic focus adjustment for a camera, comprising: a step; and data conversion means for generating information necessary for the focus adjustment of the camera based on the relative image interval of the subject image calculated by the correlation calculation means. apparatus.

(2 ') The image signal correcting means, when the value of the regression line obtained by the linear approximation means is negative,
An absolute value of the correction value is added to the first image signal, and when the value of the regression line obtained by the linear approximation unit is positive, the correction value is added to the second image signal. ') An automatic focusing device for a camera according to (1).

(3 ') The first line sensor and the second line sensor are divided into a plurality of blocks, and the relative image interval of the subject image calculated for each block or the selected one block (1 ′) The automatic focus adjusting device for a camera according to (1 ′), which generates information necessary for adjusting the focus of the camera based on the calculated relative image interval of the subject image. (4 ') The automatic focus adjusting device for a camera according to (1'), wherein the first storage and holding means and the second storage and holding means are shared.

[0038]

According to the distance measuring apparatus of the present invention, the noise caused by an external factor among the sensing noises is a uniform noise superimposed on the subject image when the subject image is quantized as an image signal by the line sensor. Accurate distance measurement can be performed by effectively correcting not only stray light but also stray light having a gradient. Further, it is possible to provide a distance measuring device which is highly accurate, simple and inexpensive, and which can be used for an automatic focusing device such as a camera.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram graphically showing a signal correction process according to the present invention.

FIG. 2 is a perspective view showing a basic configuration of the apparatus according to the embodiment.

FIG. 3 is a circuit block diagram of an automatic focusing apparatus used in the embodiment.

FIG. 4 is a graph showing an example of an image signal and noise according to the embodiment.

FIG. 5 is a graph showing an example of intermediate data during execution of the embodiment;

FIG. 6 is a flowchart illustrating a procedure for distance measurement according to the embodiment;

FIG. 7 is a graph conceptually showing a conventional signal correction process.

FIG. 8 is a graph showing an example of a conventional image signal and noise.

[Explanation of symbols]

 1a: Line sensor (L), 1b: Line sensor (R), 2a: Optical system (L), 2b: Optical system (R), 3: Sensor control and signal processing circuit, 4: AFIC, 5: CPU (correction) Calculation means including means), 6 ... EEPROM (storage means), S1 to S24 ... processing steps for distance measurement.

Claims (2)

[Claims] 1. An optical unit for receiving a light beam from an object and dividing the light beam into a pair of light beams separated by a predetermined distance; and a pair of light receiving units disposed at an image forming position of the pair of light beams. A light-receiving element array that outputs a pair of image signals related to the object, a storage unit that stores a correction value for correcting a sensitivity variation unique to the pair of light-receiving element rows, and using the correction value. Means for correcting the pair of image signals and comparing the corrected image signals with each other to equivalently detect a noise signal component included in one of the image signals; and Calculating means for removing the distance, and calculating a distance to the object based on a mutual interval between the pair of image signals after the noise removal calculation. 2. The distance measuring apparatus according to claim 1, wherein the noise signal component detecting means sets a regression line by a least square method based on the two image signals after the sensitivity variation correction.