JP2003083746A - Optical range finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical range finder without stadia wires and capable of automatically and precisly measuring a distance in a whole measuring distance region without performing visual reading. SOLUTION: The optical range finder is equipped with a staff 101 having a known scale, a collimation telescope 11 which is equipped with a collimation system wherein an optical system for picking up the image of the staff 101 is arranged in the order of an object lens L1, a focus lens L2, a branched optical system P1, a fixed focal surface FP and an eyepiece L3 from the staff 101 and an image pickup system provided in the branched light path branched by the branched optical system P1 and having an area sensor 17 having a light receiving surface 17i set at the position equivalent to the fixed focal surface FP, and an arithmetic means 23c setting the space between the staff 101 and the light receiving surface 17i of the area sensor 17 to the distance between object images and operating an optical variable used in the operation of a distance, on the basis of the number of pixels wherein the image of the staff 101 occupies the pixels of the area sensor 17 and calculating the distance based on the optical variable value corresponding to the number of pixels.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring machine for measuring a level, a distance and the like by using an optical device including an imaging optical system such as an objective lens. The present invention relates to a distance measuring device that processes image data to automatically measure the distance.

[0002]

2. Description of the Related Art Auto level is known as one of surveying instruments. The conventional auto level has a configuration and functions for level measurement and stadia distance measurement. The measurement work includes a work in which the worker enters the visual measurement result measured through the eyepiece lens in the carrying notebook. In the distance measurement, a level gauge between two stadia lines arranged at a position symmetrical to the horizontal line in the field of view is read, and the horizontal distance is calculated from the read value of the level scale, the multiplier, and the addend. Skilledness was required to read this staff.

In this conventional auto-level distance measurement, the length (scale) of an object image within a fixed vertical field of view is measured, the imaging magnification at that time is calculated, and the focal length is determined by this imaging magnification. The measurement distance was calculated by adding an addend to the value obtained by dividing (the focal length of the inner focus lens at the infinity in-focus position). At this time, the reading field of view is set to 1 of the focal length.
When set to / 100, the measurement distance is 100 x [scale reading] + [stadia addend]. In the current inner focus telescope,
Multipliers = 100 and addends = 0 can be set regardless of the measured distance when the measured distance from the actual distance is 10 m and the error at 30 m or more is 0.4% or less.

As a further improved conventional auto level, there is a digital level in which a CCD line sensor is mounted in a branch system branched from the optical path of a telescope. This conventional digital level requires dedicated staff having a pattern array corresponding to the mounted level and distance analysis means. However, the dedicated staff has a drawback that the distance analysis means, that is, the staff pattern arrangement is not effective if the digital level is different. That is, the level and distance analysis means function only when a dedicated staff is prepared, and the operation is characterized in that the distance analysis means (digital level) and the dedicated staff work mutually. For this reason, the mutual support operation cannot cope with the majority of staffs on the market other than the dedicated staff.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical distance measuring device capable of performing automatic precision calculation over the entire measuring distance without visual reading. Another object of the present invention is to provide an optical distance measuring device which can be measured by a general-purpose staff without depending on mutual assistance between the dedicated staff and the distance analysis means.

[0006]

SUMMARY OF THE INVENTION According to the present invention, which achieves this object, an object having a known size and an optical system for imaging the object have an objective lens, an inner focus lens, a branching optical element, a fixed focal plane, and an eyepiece in order from the object side. Optical system including a collimation system arranged in this order, and an image pickup system including an area sensor arranged at a position equivalent to the fixed focal plane in the branched optical path branched by the branching optical element. And an arithmetic means for calculating an optical variable used for distance calculation based on the number of pixels occupied by the area sensor of the object image, and calculating a distance with an optical variable value according to the number of pixels. The optical variable used for the distance calculation is an optical variable that constitutes an object-image distance which is a distance between the object and the image plane of the area sensor, a front focal length, a principal point distance, a rear focal length, and an imaging magnification. including. The optical variable, the front focal length, the principal point interval, the rear focal length, and the imaging magnification are functions of the occupied pixel number that varies depending on the object distance based on the optical design data of the optical system. In this embodiment, the functional form for obtaining the focal length, the principal point interval, and the imaging magnification as optical variables whose independent variable is the occupied pixel number that changes depending on the object distance can be defined by b / (p−a) + c. . However, p is the number of pixels occupied by an image of an object of known size formed on the area sensor of the imaging system,
Or, it is an average value thereof, and a, b, and c are undetermined coefficients that are predetermined based on the optical design data. The computing unit computes the distance between the reference position and the object by the following formula (1) for the imaging system, with the distance between the reference position with respect to the housing supporting the optical system and the fixed focal plane as a mechanical distance. Distance = F (p) × [m (p) + 2 + 1 / m (p)] + HH ′ (p) − [mechanical distance] (1) where F (p) is the imaging system of an object of known size. The number of pixels occupied by the image on the area sensor, or its average value p
Is a focal length, m (p) is the number of pixels occupied by an image of an object of known size on the area sensor of the image pickup system, or an image-forming magnification having an average value p thereof as a variable, and HH '(p) is known. The number of pixels occupied by the image of the dimensional object on the area sensor of the imaging system, or the principal point interval with the average value p as a variable. The imaging magnification of the imaging system, the focal length, the principal point interval is represented by the number of pixels occupied by the image, and the object of known dimension is a surveying standard, and is a periodic object that is applied or printed on the surface of the standard as a periodic object. One or more cycles of the scale can be the object image.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the embodiments of the present invention, the pixels of the image occupying pixel number are used as the pixels of the area sensor, and the image forming magnification, focal length, and principal point interval of the image pickup system are represented by the image occupying pixel number. It is characterized in that the image magnification, the focal length, and the principal point interval are calculated as a function of an arbitrary image occupied pixel number. The object is a scale of staff or staff, whose image becomes a periodic image, for example, a tool of a surveying instrument. Then, the number of pixels occupied by the imaging scale of the installation staff at an arbitrary distance is recognized, the imaging magnification, the focal length, the principal point interval are calculated, and the distance is calculated.

The present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a surveying instrument to which the present invention is applied. This optical system is an example of an automatic level or digital level optical system, and the present embodiment is applied to the digital level collimation telescope 11.

In this embodiment, a staff 101 having a surveying scale on its surface is used as an object of known size. The illustrated staff 101 stands vertically at a predetermined survey point, and a scale provided on one surface of the staff 101 indicates the height from the survey point (installation position).

The optical system of the digital level collimation telescope 11 is housed in a lens barrel 31, and an object, that is, the objective lens L1, a focusing lens L2, an optical compensator 13, and a branch optical system are arranged in this order from the staff 101 side. P1,
The focusing screen 15 and the eyepiece lens L3 are provided. The focusing lens L2 is supported by the lens barrel 31 so as to be movable along the optical axis O, and is moved along the optical axis O by the focusing lens driving device 19. The focusing screen 15 is
One of the surfaces is arranged so as to be the fixed focal plane FP, and a cross line is provided on one surface of the focusing screen 15.
The optical compensator 13 has a function of compensating so that the focus position does not change even when the lens barrel 31 is tilted, and has a function of erecting the image formed by the objective lens L1 and the focusing lens L2.

The branch optical system P1 includes a focusing screen 15, a collimation system (observation optical path) toward the eyepiece L3, and the area sensor 1.
It has a function of branching to an image pickup system (image pickup optical path) heading for 7. The area sensor 17 is a so-called CCD or CMOS.
Is a two-dimensional image sensor such as. This area sensor 17
Is disposed at a position where the light receiving surface 17i is equivalent to the fixed focal plane FP.

The focusing lens driving device 19 includes a motor, a speed reducing mechanism, and a clutch mechanism. The rotation of the motor is decelerated by the speed reduction mechanism and transmitted to the focusing lens L2 via the clutch mechanism to drive the focusing lens L2 with high accuracy. The clutch mechanism has a configuration capable of switching between the automatic focus adjustment mode and the manual focus adjustment mode.

In this surveying instrument, as the input section 20, an input key 2 including a power key, an escape key, a cursor key, a backlight key, a menu key, an enter key, etc.
1a, an AF / measurement switch 21b, and an AF / MF changeover switch 22 are provided. AF / measurement switch 21
Reference numeral b is a switch for executing automatic focus adjustment processing and automatic measurement processing, and the AF / MF switch 22 is a switch for switching between automatic focus adjustment and manual focus adjustment.

Further, this surveying instrument has an automatic focus adjustment process,
A main circuit 23 for controlling automatic measurement processing and the like is built in. The main circuit 23 drives the area sensor 17 to capture an image, inputs the captured image data in pixel units, performs A / D conversion, and executes image processing such as white balance adjustment and edge enhancement in the image processing circuit 23a, Write to the frame memory 23b. The data written in the frame memory 23b is D
The image processing circuit 23a and the CPU 2 are transferred to the RAM.
The 3c jointly read the predetermined data with the built-in calculation software and calculate the level and distance. The calculated level,
The distance and the like are displayed on the LCD panel 24. In the figure, reference numeral 26 is a power source.

Next, the surveying principle of this embodiment using this digital level will be described with reference to FIG. In this figure, the equivalent objective lens 51 is an objective lens L1 of the collimating telescope 11, a focusing lens L2,
Optical compensator 13, branch prism P1, optical system 15
Is an equivalent optical system in which is shown as one equivalent lens. The front focal position 52 is the front focal position of the collimating telescope 11, the front principal point 53 is the front principal point position of the collimating telescope 11, the rear principal point 54 is the rear principal point position of the collimating telescope 11, and the rear focal point. Reference numeral 55 is a rear focal position of the collimation telescope 11. Fixed focal plane FP
Is a fixed image forming surface on the eyepiece side, and the light receiving surface 17i is a fixed image forming surface on the imaging side, and these are set at equivalent positions. Reference numeral IRF is an infrared cut filter. The symbol MS is the machine center of the digital level 10 and is the reference position.

The object distance d1 is the distance between the staff 101 and the front focal point 52, the front principal point distance d2 is the distance between the front focal point 52 and the front principal point 53, and the principal point distance d3 is the front principal point 53. Distance between rear principal points 54, rear focal length d4
Is the distance between the rear principal point 54 and the rear focal point 55, and the image forming distance d5 is the distance between the rear focal point 55 and the fixed focal plane FP in the case of the collimation system, but the image forming distance d5 'in the image pickup system is , The distance d51 from the rear focus 55 to the branch point and the light receiving surface 1 from the branch point
It is the sum of the distances d52 to 7i.

The inner focus telescope optical system includes the main elements of the lens, the object distance (Z), the front focal length (F), the principal point distance (HH '), the rear focal length (F'), and the image formation. It can be expressed as a distance (Z '). The distance between objects (L) is given by the formula L = Z + F + HH '+ F' + Z '. Assuming that the distance from the lens barrel reference position of the inner focus telescope optical system to the light receiving surface 17i is d, the distance D from the reference position to the object is given by the equation D = Z + F + HH '+ F' + Z'-d ... . Furthermore, in the formula, since both the object point and the image point are in the air,
Substituting F = F ', Z = m * F, and Z' = F / m, the distance D is given by the formula: D = F * (m + 2 + 1 / m) + HH'-d ... Therefore, the distance from the reference distance to the object can be represented by F (P), m (P), and HH '(P) which are functions of the occupied pixels. The imaging distance Z ′ of the collimation system is from the rear focus 55 to the focusing screen FP (d5), and the imaging distance Z ′ of the imaging system is
From the rear focal point 55 to the light receiving surface 17i (d5 '= d51 +
d52).

Since the image plane of the telescope optical system of the inner focus is fixed, it is necessary to move the focusing lens L2 of the inner focus according to the near and far images. When the focusing lens L2 moves, according to the movement, the main elements of the lens, that is, the optical variable, the object distance (Z), the front focal length (F), the principal point distance (HH '), the rear focal distance (F'), The imaging distance (Z ') all changes. The image magnification at any distance is calculated from the design data, and the value obtained by dividing the image size of the image of the known object size on the image plane by the known pixel interval is the number of occupied pixels, so the focal length, principal point interval, Imaging magnification can be defined as a function of the number of occupied pixels. Therefore, if the number of occupied pixels is known, the distance can be calculated by an equation. The pixels of the number of pixels occupied by the image may be pixels of the area sensor or pixels of the line sensor.

The distance calculation according to the present embodiment is performed away from the concept of multiplier and addend, and the distance is calculated assuming that the optical variable changes.
It is characterized in that the variable of the optical variable, that is, the parameter is the number of pixels occupied by an image of known scale. When the object-image distance d is represented by the optical variable of the equivalent optical system in FIG. 2, the object-image distance = [object distance] + [front focal length] + [principal point interval] + [rear focal length] + [conclusion] Image distance] or d = d1 + d2 + d3 + d4 + d5 '. Therefore, the distance calculation reference (machine center MS) is set in the actual holding mechanism (lens barrel, housing) of the optical lens system, and the distance between the machine center MS and the imaging plane FP is [machine distance] d.
6, and the distance obtained by subtracting this from the object-image distance d is the distance from the machine center MS. That is, the common point between the equivalent lens 51 and the actual constituent optical lens system is only the object point and the image point.
Therefore, the distance D from the machine center MS to the staff 101
Is the distance = [object distance] + [front focal length] + [principal point interval]
+ [Rear focal length] + [imaging distance] − [machine distance] or D = d1 + d2 + d3 + d4 + d5′−d6.

A value obtained by dividing the front focal length d2 by the object distance d1 is the imaging magnification, and the imaging distance d5 is the rear focal length d4.
Since the value is equal to the value obtained by dividing by, the imaging magnification is m, and the distance calculation formula using this as an optical variable is as follows. Distance = (m + 1) × [front focal length] + [principal point interval] +
(1 / m + 1) x [rear focal length]-[machine distance] = (m + 2 + 1 / m) x [focal length] + [principal point interval]-
[Machine distance] or D = (m + 1) × d2 + d3 + (1 / m + 1) × d4-
d6 = (m + 2 + 1 / m) × d4 + d3-d6 However, [focal length] = [front focal length] = [rear focal length].

Further, the imaging magnification m, [focal length] d2,
Let d4 and [principal point interval] d3 be a function of the number of pixels occupied by the image formation of the known object, and let the average value p of the number of pixels occupied by the image for one cycle of the scale on the area sensor surface be an independent variable. Letting F (p), m (p), and HH '(p) be the optical variables, imaging magnification, magnification focal length, and principal point spacing at this time, the distance calculation formula is expressed by the following formula (1). To be done. Distance = F (p) × [m (p) + 2 + 1 / m (p)] + HH ′ (p) − [mechanical distance] (1) From this equation, the optical variables F (p), m (p) ), HH '(p), the distance can be accurately measured.

Here, the number of occupied pixels is illustrated in FIG. The pattern 102, the capital letter 103, the pitch scale 105, that is, the image occupied by each image of the 5 mm scale S1 of 10 mm / cycle (5 mm pitch) and the 10 mm scale S2 of 20 mm / cycle (10 mm pitch) is
It can be seen that the number of occupied pixels is different depending on the distance to the installed staff 101.

Imaging magnification corresponding to the distance to the target,
Optical design values of the number of pixels (pixels) occupied by the target, focal length, principal point spacing, focal length f, principal point spacing HH ', and magnification m
The relationship with the function value of is shown in the column of optical design values in Table 1. The target is the 5 mm scale S1 of the staff 101, and the occupied pixel number is the occupied pixel number of one cycle of the 5 mm scale S1.

[0024]

[Table 1]

In the present invention, the focal length, the principal point interval, and the imaging magnification, that is, the focal length as an optical variable whose number of occupied pixels which changes according to the object distance are independent variables,
The functional form of the principal point interval and the imaging magnification with respect to the variable P is defined as a functional expression of b × (pa−) γ + c. However, a, b, and c are undetermined coefficients of focal length, principal point interval, and magnification, and γ is a coefficient for correcting the difference between the design value and the actual measurement value. Focal length,
The principal point interval and the imaging magnification can be calculated by this functional form.

Here, γ is a coefficient for correcting the difference between the design value and the actual measurement value. As a result of calculation by substituting an arbitrary value for γ, it was found that the calculation accuracy can be secured even when γ = -1. When γ = −1, the above function formula can be defined as the following formula (2). b / (p−a) + c (2) However, p is the number of pixels per one cycle of the scale or its average value.

The indefinite coefficients of the focal length, the principal point spacing and the imaging magnification can be calculated by this functional expression (2). For example, 3 points with different distances, distances 100m, 10m and 1m
Table 2 shows the relationship between the number of pixels in each pixel and each design value. In Table 2, X1, X2, and X3 are the number of occupied pixels at each distance, Y1, Y2, and Y3 are the focal lengths at each distance, the principal point spacing, and the design value of the magnification, and a, b, and c are at each distance. It is an undetermined coefficient of focal length, principal point interval, and magnification.

[0028]

[Table 2]

Here, the undetermined coefficients a, b, and
When c is ao, bo, co, the undetermined coefficients ao, bo, co can be defined by the following equations. ao = [X3 * (X2-X1) * (Y3-Y2) -X1 * (X3-X2) * (Y2-Y1)] / [(X2-X1) * (Y3-Y2)-(X2-X1) * (Y 2-Y1)] bo ＝ (Y1-Y2) * (X1-ao) * (X2-ao) / (X2-X1) co ＝ Y1-bo / (X1-ao) Imaging magnification (paraxial) m, focal length d
4. The principal point interval d3 can be converted into the number of pixels per scale cycle. However, "*" is a multiplier symbol. The values a, b, and c in Table 2 are the focal length, principal point interval, and imaging magnification that have changed in this way.

Further, numerical examples of the focal length, the principal point interval, and the imaging magnification calculated by substituting the undetermined coefficients a, b, and c in the above 100 m, 10 m, and 1 m into the functional expression (2) are shown. Focal length F (p) = 313083.228 / (P + 1301.115) -48.034 Principal point interval HH (p) = 34349 / (P + 755.424) +124.262 Imaging magnification m (p) =-1.20003 × 10 ¹² / (P + 50806564 ) −23625.022 The occupied pixel number P is measured, and the distance to the target object (staff 101) can be calculated by the above three equations and the equation (1) described above. It should be noted that these functional forms, expressions, etc. are stored in advance in a memory as a calculation algorithm, and are read and processed by the CPU 23c during distance measurement.

The above calculation formula is for three points, but the values calculated by the above function meter at each distance in Table 1 are
The values are shown in the function value column of Table 1. Evaluation of the values approximated in this way, that is, the difference between the design value and the function value,
The results are shown in Table 3.

[0032]

[Table 3] As described above, according to the present embodiment, it can be understood that the accuracy can be approximated from 1 m to 100 m with high accuracy.

As described above, according to this embodiment, the functions of the focal length F (p), the principal point distance HH (p), and the imaging magnification m (p) are obtained in advance for each digital level model and stored in the memory. If it is stored in, the distance can be calculated by measuring the number of pixels occupied on the scale of the staff by simply inputting the staff to be used and the scale unit of the staff.

Next, an embodiment for detecting the number of pixels occupied by an image of one cycle of scale, that is, one cycle of graduation will be described. Since there is no unified manufacturing standard for the staff on the market, the standard scale structure of the staff 101 will be described with reference to FIGS. FIG. 5 shows the staff 10 observed in the field of view 151 of the collimating telescope 11.
The state of the first scale surface (display surface) is shown. The scale display of the staff 101 is the long distance pattern 102,
Large character string 103 for long distance, small character string 104 for short distance, and 5 mm scale S1, 10 mm scale S2
The pitch scale 105 is composed of. Note that normally,
The ground color of the scale surface of the staff 101 is white, the long distance pattern 102, the character strings 103 and 104, and the pitch scale 1
05 is painted or imprinted in black or red.

The character height of each number in the large character string 103 is 5
It is 0 mm, and the character height of each number in the small character string 104 is 6
mm. The upper side of each number of the character strings 103 and 104 and the upper side of the scale (black band) of the pitch scale 105 are set so as to be located on the same horizontal line when the staff 101 is installed vertically, and each number is set. The height above the upper side is the height indicated by that number.

The long-distance pattern 102 is a black circle attached to the upper part of each numeral of the large character string 103.
It indicates that the number is 1 × 1000 mm (1 m). For example, in Figure 5, 3 black circles are 3 x 1000 mm
It indicates that it is a (3 m) unit, and two black circles are 2 x 100
It is displayed that it is in the 0 mm range. Large character string 103
Is composed of a single digit and the unit is 100 mm (10 cm). For example, the number “2” in the large character string 103 in FIG. 5 indicates that it is on the order of 2 × 100 = 200 mm. Figure 5
In this case, three black circles are added as the long-distance pattern 102 above the character “2” of the large character string 103, so the number 2 of this large character string 103 is 3000 + 20.
It can be seen that 0 = 3200 mm range is shown.

The small character string 104 is indicated by a three-digit number, the minimum unit (first lower digit) is 1 cm (10 mm), the second digit is 10 cm, and the third digit is 100 cm. .
For example, in FIG. 4, the three-digit number “323” of the small character string 104 indicates that it is 323 × 10 = 3230 mm, 323 cm, or 3 m23 cm.

The pitch scale 105 is composed of two rows, and the 5 mm scale S1 in the left row is a repetition of bright and dark bands of 10 mm cycle formed in units of 5 mm, and the right row has 1 row.
The 0 mm scale S2 is a repetition of bright and dark bands with a cycle of 20 mm, which is formed in units of 10 mm. In the case of visual measurement, the pitch scale 105 is usually used at a short distance.
In this embodiment, the number of pixels occupied by the image of one scale of the 5 mm scale S1 or the 10 mm scale S2 of the pitch scale 105 is a fraction. Detects to the decimal point by calculation.

Further, in the case of visual leveling, the operator has a level (level height) in the visual field of the collimation telescope 11 that the horizontal line 53 overlaps with the long-distance pattern 102 of the scale surface of the staff 101 and the character string. The numbers 103 and 104 and the pitch scale 105 are read and substituted into a predetermined mathematical formula for calculation. The distance is determined by reading the long distance pattern 102 on the scale surface of the staff 101 where the upper and lower stadia lines 54 and 55 overlap, the numbers in the character strings 103 and 104, and the pitch scale 105 to read the stadia line 1
The length between 54 and 155 is calculated, and the calculated length is substituted into a predetermined mathematical expression for calculation. In FIG. 5, reference numeral 152 is a vertical line of a crosshair, and the intersection of the vertical line 152 and the horizontal line 153 is the collimation axis (optical axis) O of the collimation telescope 11.
Passes through.

Next, an embodiment of the reading process of the number of pixels occupied by the image of the scale of the pitch scale 105 of the staff 101 by the digital level 10 will be described with reference to FIG. First, the operator collimates the staff 101 installed at the survey point by the collimation telescope 11 and drives the focusing lens L2 to drive the staff 1
Focus on 01. Then, image data (pixel data) for one frame captured by operating the area sensor 17
Are written in the frame memory 23b. Here, the image data is a value obtained by binarizing the pixel output proportional to the brightness incident on each pixel of the area sensor 17 and converting it into a numerical value. Capture one frame) and write it in the frame memory 23b.

The automatic scale reading process is performed by the image on the light receiving surface 17i of the area sensor 17, the vertical line 52, the horizontal line 53, the upper line, the lower line 52, and the upper line.
It is based on the pixel positions and coordinates of the virtual image of 55.

(1-1) Pixel data in a line in the vertical direction is read at a predetermined horizontal detection start position, and a simple average value is obtained. In the normal collimation survey, the horizontal detection start position is used when collimating the staff in the collimation telescope.
Normally, the intersection of the crosshairs is made to coincide with the scale of the horizontal center of the staff, so the center position of this staff corresponds to the horizontal detection start position. However, depending on the staff, the scale portion may not be located near the center of the staff, and in such a case, the position shifted left and right from the center is set as the horizontal detection start position. The pixel data to be used is all the vertical data of the horizontal detection start position determined by the staff, or only a part of the data.

In the case of a monochrome area sensor, data for one column of pixels is read, and for a color area sensor, data for two columns of pixels is read. However, when the color area sensor uses only a specific color component for detection, one row is enough. For example, when the color area sensor includes R, G, and B primary color filters and uses only the G component, only the pixel data of the pixel column to which the G filter is attached is used.

(1-2) The obtained average value of pixel data for one column and each pixel data are compared with a predetermined threshold value one by one, and each pixel data is binarized. As a result, bright and dark pixel data is obtained.

(1-3) The number of consecutive pixel data of the same level is sequentially obtained from the binarized pixel data. Figure 4
In the area (B) of, white level; 5, black level; 5, white level; 5, black level; 6, white level;
... In the area (C) of FIG. 4, from the bottom,
White level: 3, Black level: 3, White level: 4, Black level: 3, White level: 1, Black level: 5, White level: 5,
Black level: 2, white level: 2, ...

(1-4) Same level (white or black level)
The absolute value of the difference between the number of continuous pixel data and the number of continuous pixel data of the same level (white level is white level, black level is black level) is calculated. In the area of FIG. 4B, white-white = 0, black-black = 1, white-white =
It is 0. In the area of FIG. 4C, white-white = 1, black-
Black = 0, white-white = 3, black-black = 2, white-white = 4, black-black = 3, white-white = 3.

(1-5) The average value of the differences between the obtained numbers of continuous pixel data at the same level is obtained. In the area of FIG. 4 (B), it is 0.33, and in the area of FIG. 4 (C), it is 2.28.

(1-6) If the average value of the differences obtained in (1-5) is less than or equal to a predetermined threshold value, the column is judged to be a scale portion. On the contrary, when the average value of the differences is not less than the predetermined threshold value, it is determined that the column is not the scale portion. Here, for example, when the predetermined threshold value is 1, since it is smaller than the threshold value in FIG.
Since (C) is larger than the threshold value, it is determined that it is not the scale portion.

(1-7) When it is judged that it is the scale part,
Move the column to be analyzed by 1 pixel or 2 pixels or more to the left or right, and execute the process from (1-1) to (1-6). Detect the column that is judged not to be the scale. Repeat until. If it is judged from the first detection result that it is not the scale part, until the scale part is detected, (1-
The processing from 1) to (1-6) is repeated while moving one pixel or two pixels to the left or right.

(1-8) The average value per column of the number of consecutive pixel data of the same level obtained in (1-3) is obtained, and the pitch scale 105 is set between the columns which greatly change in the adjacent columns. The boundary is defined by the 5 mm scale S1 and the 10 mm scale S2 (FIGS. 5 and 6).

In order to find the periodicity, it is possible to execute Fourier transform on one row of pixel data to detect the presence / absence of a peak value. However, since many Fourier transforms perform sum of products operation, the processing time is long. turn into. On the other hand, according to the method of the present embodiment, since the periodicity can be found by counting and subtracting the number of pixel data, simple processing of calculating the average value, and calculation, the detection time can be shortened.

The calculation method of the interpolated value is selected from the number of pixels included in one side of an arbitrary image of the scale. In the present embodiment, one is selected from two types of interpolation value calculation methods. The vertical period of the scale portion of the actual staff is a fixed value of 10 mm for the 5 mm scale S1 and 20 mm for the 10 mm scale S2. On the other hand, since the horizontal length of the scale differs depending on the step, even if the ratio of the lengths of the sides in the same vertical direction and the horizontal direction is obtained, the value changes depending on the number of steps. However, the ratio obtained from the same step has a substantially constant value regardless of the measured distance. That is, by determining the ratio between the horizontal direction and the vertical direction, comparing it with the value obtained from the ideal value, and determining which value is the closest, it is possible to determine what the scale is.

(2-1) The black level (black) part is detected from the image of the scale part, and the horizontal side (any of H1 to H3) and the vertical side (V1 to V4) of the black level part shown in FIG. (Any one of the above) is obtained to determine the number of pixels occupied and the stage.

(2-2) Any one side of the black part (H1
Which interpolation value calculation method is to be used is determined based on the number of pixels occupied by H3 and any of V1 to V4) and the information on the number of stages. In this embodiment, two interpolation value calculation methods are set and used according to the number of pixels included in one side. In the present embodiment, the interpolation method is divided according to the length of the vertical side of the scale.

According to this method, if the lengths of the two sides of the black portion (dark portion) of the scale can be identified, the scale is partially missing and the black pixel data is discontinuous. Even in this case, the calculation method of the interpolated value can be determined.

When the length of the side is less than a predetermined value (the number of pixels occupied by the side is less than the predetermined value), the accurate cycle of the scale portion is obtained by Fourier transform, and the interpolated value is calculated from the phase of the obtained position. The details will be described below. (3-1) Obtain the number of pixels included in one cycle of the black and white data of the scale at a plurality of points and calculate the average value thereof. (3-2) The calculated number of pixels is set to one cycle size and 10 mm
The Fourier transform is performed by using the data of the 5 mm scale S1 portion of the cycle for 10 cycles, and the spectrum of the cycle is calculated. There is a spectrum characteristic as a means to know what frequency (cycle) is included in a certain waveform, and if the spectrum is obtained by performing Fourier transform using data of about 10 cycles, the most A peak appears in the cycle part. In the case of this embodiment, a peak is found in a portion having a period corresponding to the number of pixels of 10 mm. The cycle at which the spectrum peaks is the exact cycle of the waveform.

(3-3) The period (number of pixels) in (3-2) is increased by 1%, the spectrum at that time is obtained, compared with the previous spectrum, and when it is large, the period is increased by 2% and the spectrum is increased. Ask for. On the contrary, when it is smaller than the previous spectrum, the period is reduced by 1% to obtain the spectrum. In this way
When the spectrum is obtained by changing the cycle in order, the spectrum becomes maximum at a certain cycle and then decreases again. The period when the spectrum becomes maximum is the exact period.

If the correct cycle is obtained as described above, the number of pixels or the average number of pixels occupied by one cycle of the scale of the pitch scale 105 can be accurately obtained. The number of pixels thus obtained is used as p in this embodiment.

When the length of the side is equal to or greater than a predetermined value (the number of pixels occupied by the side is equal to or greater than the predetermined value) In this case, sufficient resolution can be obtained only by using the number of pixels. The interpolation value is calculated from the ratio based on the number of pixels of. That is, the number of pixels included in one scale cycle is counted.

The present invention is premised on the principle of manufacturing staff and staff that "scales have a periodicity with high spatial accuracy", and the scale patterns arranged at regular intervals form an imaging spatial frequency depending on the distance. Since it is different, the result of automatically analyzing the imaging spatial frequency is applied. Compared with the conventional method, it has the following effects and advantages. This scale 1 cycle or scale 2 cycles or more is used as the target image of the occupied pixel number, and the imaging magnification is measured by measuring the optical image of a known length by the occupied pixel number.

The conventional visual stadia measurement was a measurement by the following formula. Distance = [stadia multiplier] x [scale reading] + [stadia addend] Here, if the stadia multiplier is decomposed, [stadia multiplier] = [focal length] / [stadia line interval] Substituting: Distance = [focal length] / [stadia line spacing] x [scale reading] + [addend] = [focal length] / [[stadia line spacing] / [scale reading]] + [addend] = [Focal length] / [imaging magnification] + [addend]

On the other hand, in this embodiment, the distance is
It becomes the following formula (1). Distance = F (p) × [m (p) +1] + F ′ (p) × [1 + 1 / m (p)] + HH ′ (p) − [machine distance] = F (p) × [m (p) + 2 + 1 / M (p)] + HH '(p)-[machine distance] (1) F (p) is the number of pixels occupied by the image of the object of known size on the area sensor of the imaging system, or its average value p , F '(p) is the number of pixels occupied by the image of the object of known size on the area sensor of the image pickup system, or its average value p is the rear focal length, but the object point , When both image points are in air, F (p) = F '(p) HH' (p)
Is the number of pixels occupied by the image of the object of known size on the area sensor of the imaging system, or the principal point interval with an average value p thereof as a variable, and m (p) is the image of the object of known size on the area sensor of the imaging system. The number of pixels occupied by, or its average value p
Is the imaging magnification with variable.

The addend of this embodiment is [addend] = F (p) × [m (p) +2] + HH ′ (p) − [machine distance], and the addend is strictly in the entire pixel occupied area. Calculated. The multiplier also treats the focal length as a variable and is strictly calculated in the entire pixel occupation area. Therefore, compared to the conventional method in which the infinite focal length is fixed, the strict calculation formula does not approximate the focal length, the principal point distance, and the imaging magnification. That is, in order to form an image at a fixed position in accordance with the change in the distance of the object point, it means that the strict measurement is performed by calculating the focal length, the principal point interval, and the imaging magnification according to the change in distance.

As a result, in the distance measurement, it is possible to avoid the error of the visual measurement, and it is possible to omit the limited distance condition that the error of the measured distance is less than 0.4% with respect to the actual distance at 10 m and 30 m or more. Highly accurate measurement is possible in all areas. The minimum scale interval differs depending on the unit (mail, feet, or feet inches), but the conversion factor is different, and if the distance is fixed and compared, the imaging spatial frequency differs by the amount multiplied by the conversion factor. Therefore, any object having a known constant spatial frequency can be used in the distance measuring device of the present invention.

As described above, this embodiment has an advantage that it is not limited to an object as a mutual aid with the analysis means, for example, a bar code, and basically, it is possible to measure if the scale can be imaged for only one cycle. That is, it becomes possible to measure if the arrangement dimension of the discrete light receiving surface group consisting of pixels arranged at regular intervals on the image plane of the optical system, for example, CCD, is known in advance and the object dimension, for example, staff scale is known. In addition, according to the digital level of the present embodiment, visual reading via the eyepiece lens is unnecessary. If it is a digital level with a built-in memory, the measurement result can be written in the memory, so a notebook is not necessary. As described above, according to the present embodiment, even a general surveying staff can measure a distance as long as a certain spatial frequency is known in advance, and an object (barcode staff) as a mutual aid with the analyzing means can be measured. ) Is not limited to.

[0066]

As is apparent from the above description, the present invention is
The object-to-image distance is the distance between the object of known size and the image plane of the area sensor, and the front focal length, principal point interval, rear focal length and Since the image pickup magnification is converted into a function of the number of pixels and the calculating means for calculating the distance between object images is provided, if the dimensions of the object are known, various objects can be used to automatically measure the distance. .

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a surveying instrument to which the present invention is applied.

FIG. 2 is a diagram illustrating a surveying principle of the embodiment.

FIG. 3 is a diagram showing a relationship between an image of a scale imaged by the embodiment and pixels of an area sensor, FIG.
FIG. 4 is a diagram showing a case of a long distance, and FIG.

FIG. 4 is a diagram illustrating a process of reading the number of pixels on the pitch scale in the same embodiment.

FIG. 5 is a diagram showing an example of a relationship between a staff used for distance measurement by the survey instrument, a collimation field of view, and a captured image.

FIG. 6 is an enlarged view of a capital letter and a pitch scale of a staff that is imaged by the surveying instrument.

FIG. 7 is an enlarged view of a pitch scale of the staff.

[Explanation of symbols]

11 collimation telescope L1 objective lens L2 focusing lens 13 Optical compensator P1 branch optical system 15 Focus plate L3 eyepiece 17 area sensor 17i light receiving surface 19 Focusing lens drive 20 Input section 21a Input key 21b AF / measurement switch 22 AF / MF selector switch 23 Main circuit 23a image processing circuit 23b frame memory 23c CPU (calculation means) 26 power supply 51 Equivalent objective lens 52 Front focus position 53 Front principal point 54 Rear principal point 55 Rear focus 101 staff D distance d Distance between objects d1 Object distance d2 front principal point distance d3 principal point interval d4 rear focal length d5 Imaging distance FP fixed focal plane MS machine center O optical axis

Claims (6)

[Claims] 1. An object having a known size, and an optical system for imaging the object, a collimation system in which an objective lens, an inner focus lens, a branching optical element, a fixed focal plane, and an eyepiece lens are sequentially arranged from the object side. An optical system including an imaging system including an area sensor disposed in a position equivalent to the fixed focal plane in a branched optical path branched by the branching optical element; and an area sensor for the object image, An optical distance measuring device comprising an arithmetic means for calculating an optical variable used for distance calculation based on the number of occupied pixels. 2. An optical variable used for the distance calculation is a variable of a distance between object images, which is a distance between the object and an image plane of an area sensor, a front focal length, a principal point distance, a rear focal distance, and a result. The optical distance measuring device according to claim 1, which is an image magnification. 3. The optical variable, the front focal length, the principal point interval, the rear focal length, and the imaging magnification are a function of the number of occupied pixels which varies according to the object distance based on the optical design data of the optical system. The optical distance measuring device according to claim 1 or 2. 4. The function form for obtaining the focal length, the principal point interval, and the imaging magnification as optical variables whose independent variable is the occupied pixel number that changes depending on the object distance is b / (p−a) + c. The optical distance measuring device according to claim 1 or 2. However, p is the number of pixels occupied by the image of the object of known size formed on the area sensor of the imaging system, or the average value thereof, and a, b, and c are predetermined based on the optical design data. It is an undetermined coefficient. 5. The calculation means calculates the distance between the reference position and the object using the distance between the reference position with respect to the housing supporting the optical system and the fixed focal plane as a mechanical distance, and ) The optical distance measuring device according to any one of claims 1 to 4, wherein Distance = F (p) × [m (p) + 2 + 1 / m (p)] + HH ′ (p) − [mechanical distance] (1) where F (p) is the imaging system of an object of known size. The focal length with the number of pixels occupied by the image on the area sensor or its average value p as a variable, m (p) is the number of pixels occupied by the image on the area sensor of the imaging system of the object of known size, or its average value p The image forming magnification, HH '(p), which is a variable, is the number of pixels occupied by an image of an object of known size on the area sensor of the image pickup system, or a principal point interval having an average value p thereof as a variable. 6. The object of known size is a surveying staff, and one or more cycles of a scale as a periodic object applied or printed on the surface of the staff is an object image. The optical distance measuring device according to claim 1.