RU2331919C2 - Projector encoding - Google Patents

Abstract

FIELD: information technology.

SUBSTANCE: projection camera projects array of spot electromagnetic rays to the measured spatial region. Each of these rays contains information that identifies uniquely this ray and is expressed in the form of code and is connected functionally with equation of line of this ray movement. These rays are fixed with the reading device in such spatial region where they can be uniquely identified using codes containing in these rays. Thereby, if the codes of at least two different rays will be registered in the N point belonging to defined zone, than the coordinates of the N point respectively chosen system of coordinates are found as an answer to the set of equations of line. However, performance of reading devices is synchronised.

EFFECT: digitalisation of the objects surface points in one working cycle.

4 dwg

Description

The technical field to which the invention relates.

1. Digitization of 3-dimensional objects.

2. Positioning.

The level of technology.

This invention is intended to digitize points in space. It can be used to digitize objects in order to create their computer models, to position any actuators without the use of sophisticated precision mechanics, or to solve other problems requiring unambiguous identification of points in space.

Currently, the digitization of points in space is reduced to finding their coordinates. For this, many devices are used, which can be divided into several groups according to the principle of operation. The first group includes optical theodolites and levels. To find the coordinates of a point, they use the principle of two intersecting lines. The second group is mechanical scanners: from small digitizers to large coordinate machines. The third group uses the location method to find the coordinates of the point, i.e. measuring the time it takes for a wave to reach a measured point. This group includes total stations, laser, electromagnetic, ultrasound scanners and recently appeared sensors from Canesta (patent No. 6323942). The fourth group uses the principle of mathematical analysis of distortion of a special image projected onto an object. This group includes projection scanners. The fifth group is based on photogrammetry, the science of determining the shape, size and position of objects from their photographic images.

This method proposes to digitize points in space using an array of narrowly directed rays, each of which contains information that uniquely identifies this ray. Thanks to this, a system consisting of an electron-optical reader (hereinafter referred to as a reader) and a computing device can identify each point in space where the rays intersect. Although the scope of this method can be much wider than just determining the coordinates of points in space, in the future, it is the solution to this problem that will be considered in the description of the invention.

By the combination of essential features, the closest of the listed analogues is the method used in projection 3D scanning. When using this method, a special image is projected onto the digitized object, which is recorded by a photo or video camera. According to the degree of distortion of this image, the computer program calculates the coordinates of the points on the surface of the object. As the projected image using direct contrast stripes. If the camera or video camera is located at an angle to the projector, then a narrow section of the object’s surface highlighted by this strip is recorded on its matrix, which is, in fact, a ready-made spline for a 3D computer model. By turning the object around its axis with a certain given step and fixing every time all new projection images, they get many such splines from which the 3D modeling program creates a computer model of the object. This is not the only method used in projection scanning. Another option is to project a strip consisting of two closely spaced stripes of different colors. It also analyzes projection distortion. This time, changes are not recorded in form, but in color at the border of these two stripes. This is due to the dependence of the sharply received image of the strip on the matrix of the photo or video camera on the distance between the lens and the surface of the object. The computer program takes into account the nature of the blur and calculates the probable coordinates of the points on the surface of the object.

The idea of remote marking of points in space using the projection of coded rays, embodied in this invention, allows for the digitization of the entire region of space or an object in one working cycle.

Disclosure of the invention.

The disclosure of the invention is shown by the example of finding the coordinates of points in space. To do this, narrowly directed electromagnetic rays are projected into the measured area of space using a digital projection apparatus (hereinafter the projector). Each pixel of the projector matrix is a small source of a ray of light. Let the settings of the projector lens and its orientation in space relative to the selected coordinate system be known, namely, the directing vector of the optical axis and the angle of rotation of the projector around this axis. Then the coordinates of the directing vector of the line along which such a beam propagates will be functions of the coordinates of the pixel on the matrix:

l = l (i, j);

m is m (i, j);

n = n (i, j).

Knowing these functions, the coordinates of the projector and the coordinates of the pixel (i, j), we can write the equation of the line along which the beam emitted by this pixel propagates.

Xn, Yn, Zn are the coordinates of the projector;

t is a variable parameter.

To solve this problem, information about the coordinates (i, j) of a pixel on the projector matrix is presented in binary code and radiated into space by the same pixel as a series of pulses. A logical unit must correspond to one characteristic of the pixel radiation, a logical zero to another. To describe the principle of operation of the system, it does not matter what this difference will be, it is important that it can be registered with a reader. The length of the series depends on the number of pixels in the matrix. For coding a million pixels, a series length of 20 bits is sufficient. Thus, the entire code can be transmitted by sequential projection of 20 frames (see Figure 1). The upper part shows the projector matrix and two arbitrary pixels. One, with coordinates on the matrix p ₁ (731, 801), the other with coordinates p ₂ (101, 217), as well as the codes emitted by these pixels. The first 10 bits of the code are the value of the Jth pixel coordinate on the projector matrix in binary form, the second 10 bits is the value of the Ith pixel coordinate on the matrix. The lower part schematically shows the states of these two pixels on the matrix in the first 4 and last 4 frames out of 20. Thanks to the lens, the radiation of each pixel has the form of a narrow beam converging at the focal point of the beam. In a zone of space where rays from neighboring pixels do not mix with each other, they can be registered with reading devices and identified by their codes. Reading can occur both directly in the area where the projection is performed, and at a distance, in the case of reflection of rays from any surface. Knowing the coordinates of the projector and the functions l (i, j), m (i, j), n (i, j), we can find the equation of the line for each ray identified in this way. To determine the coordinates of a point, it is necessary that two beams intersect in it. To do this, you need a second projector, the coordinates of which must not coincide with the coordinates of the first projector (see Figure 2). If the surface of a certain object appears in the region of intersection of rays at the point N, then the reader will register at this point two reflected electromagnetic rays and, accordingly, two codes (hereinafter the integrated code). Codes should not be mixed with each other. Technically, this can be achieved in several ways. Let, for definiteness, codes be transmitted sequentially, first with one projector, then with another. The length of the integrated code, if a million pixels are used in projectors, will be 40 bits. Having received the integrated code, the program of the computing device will calculate the coordinates of the point by solving the system of equations of two intersecting straight lines: the first, passing along the beam from the Lijth pixel of the matrix of the first projector, the second, passing along the beam from the Mijth pixel of the matrix of the second projector. The process of calculating the coordinates of a point is based on the laws of geometry. They say that if the equations of two lines intersecting at one point are given, then the coordinates of this point can be calculated (see Figure 3).

X _A , Y _A , Z _A - coordinates of point A (1st projector) belonging to the line AN;

l _A , m _A , n _A - coordinates of the directing vector of the line AN;

t _A is a variable parameter of the equation of the line AN.

The equation of the line BN will be:

XB, Y _B , Z _B - coordinates of point B (2nd projector) belonging to the line BN;

l _B , m _B , n _B - coordinates of the directing vector of the line BN;

t _B is a variable parameter of the equation of the line BN.

The coordinates of the point N will be a solution to the system of equations of two lines AN and BN. Since the matrix of the projectors emit a lot of rays, in the area of their intersection, it becomes possible to determine in this way the coordinates of any point belonging to this area.

A brief description of the drawings.

Figure 1

1 - projector matrix;

p ₁ (101, 217) - pixel with coordinates i = 101, j = 217;

p ₂ (731, 801) - pixel with coordinates i = 731, j = 801;

K1, K2, K3, K4 ... K17, K18, K19, K20 - projections of the first 4 and last 4 frames out of 20 in the process of projecting codes with pixels p ₁ (101, 217) and p ₂ (731 , 801).

Figure 2

A is the first projector;

In - the second projector;

1 - matrix of the first projector;

2 - matrix of the second projector;

3 - reading device;

4 - digitized object;

Cod Lij - serial binary code emitted by the Lij-th pixel of the 1st projector;

Cod Mij - serial binary code emitted by the Mij-th pixel of the 2nd projector;

Cod Lij + Cod Mij - integrated code reflected from the surface of the object at point N.

Figure 3

A - point (1st projector) belonging to the line AN;

B - point (2nd projector) belonging to the line BN;

N is the measured point of space;

,

,

- проекции направляющего вектора

на оси координат;

,

,

- projections of the guide vector

on the coordinate axis;

,

,

- проекции направляющего вектора

на оси координат.

,

,

- projections of the guide vector

on the coordinate axis.

Figure 4

α is the angle of rotation of the optical axis of the first projector around the axis OY;

β is the angle of rotation of the optical axis of the first projector around the OZ axis;

OO ₁ is the optical axis of the first projector;

OO ₁ ″ - the optical axis of the projector after double rotation through the angle α and angle β;

A ₀₀ A _0J A _IJ A _I0 is the projection of the matrix of the first projector onto a plane perpendicular to its optical axis and spaced from the projector at a distance of OO ₁ ;

N is the projection of an arbitrary pixel with coordinates (i, j) on the plane A ₀₀ A _0J A _IJ A _I0 ;

N ″ - the point obtained by turning the point N through the angle α and angle β.

The implementation of the invention.

Finding the coordinates of the points on the surface of the object can be carried out using two projectors, one reader and a computer. Before the start of digitization, a system of Cartesian coordinates with a start at point O and direct measurements is selected, the data necessary to determine the equations of lines along which the rays emitted by each pixel of the first and second projector are found is found. Namely:

X _A , Y _A , Z _A - coordinates of the first projector;

X _B , Y _B , Z _B - coordinates of the second projector;

α is the angle of rotation of the optical axis of the first projector around the axis OY;

β is the angle of rotation of the optical axis of the first projector around the OZ axis;

γ is the angle of rotation of the optical axis of the second projector around the axis OY;

θ is the angle of rotation of the optical axis of the second projector around the axis OZ.

The following shows a possible variant of finding the coordinates of the guide vectors of the rays emitted by the pixels of the matrix of the first projector.

Let the projector matrix contain J horizontal pixels and I vertical pixels. We place the projector at the origin so that its optical axis coincides with the axis OX. A frame A ₀₀ A _0J A _IJ A _{I0 is} projected onto a flat surface perpendicular to the optical axis of the projector and located at a distance a ₁ = | OO ₁ | from it, shown in the drawing (see Figure 4). Measured distances | A ₀₀ A ₁₀ | and | A ₀₀ A _0J | and relations are calculated:

Relative to the selected coordinate system, the coordinates of an arbitrary point N, which is a projection onto this pixel surface with coordinates (i, j), will be equal to:

x = a ₁

the index "1" in all cases indicates membership in the first projector.

. Повернем оптическую ось проектора, а вместе с ней и вектор

, вначале вокруг оси OY на угол α, а затем вокруг оси OZ на угол β. В результате этих двух поворотов вектор

перейдет в вектор

, координаты которого выразятся в матричной форме следующим образом:These coordinates will also be the coordinates of the guide vector.

. Let's turn the optical axis of the projector, and with it the vector

, first around the OY axis by the angle α, and then around the OZ axis by the angle β. As a result of these two turns, the vector

will go into vector

whose coordinates are expressed in matrix form as follows:

Similarly for the second projector:

Thus, the equations of lines along which the rays from each pixel of the first projector propagate are defined:

and equations of lines along which rays from each pixel of the second projector propagate:

One necessary condition should be emphasized. Projectors, a reading device and a digitized object must be mutually stationary during the translation of the integrated code. However, this requirement will decrease with the use of stabilizing systems for projectors and readers, as well as an increase in the translation speed of the integrated code. The projectors and reader are synchronized and controlled by a computer. Its memory stores codes that will be emitted by the pixels of the first and second projector. Each code represents the binary coordinates of the corresponding pixel on the matrix. Let projection arrays contain one million pixels each. The length of the code depends on the number of pixels in the matrix of the projector, and in this case it is enough that its length is 20 bits. Thus, for digitization, projection of 20 frames by the first projector and 20 frames by the second projector will be required.

,

. Здесь верхний индекс указывает на номер стека, а нижний на номер проектора. Эти координаты подставляются соответственно в 1-е и 2-е уравнения, где вычисляются координаты направляющих векторов лучей, излучаемых этими пикселями.The program starts with the fact that the data that are the values of the first bits of the codes emitted by the pixels of the matrix of the first projector are sequentially read from the computer's memory. From this data, the first frame is formed, which is projected onto the digitized object. Simultaneously with the projection of the frame, the exposure of the sensor matrix begins. It registers the rays reflected from the surface of the object. For each pixel of this matrix a region is allocated in the computer memory with a volume of 40 bits, simulating the operation of the stack. The data of the first frame recorded by these pixels is entered there. Then the program reads data from all second digits and the cycle repeats. When the first projector consecutively projects all 20 frames, it turns off and the second projector starts working in the same way. The results recorded by the pixels of the matrix of the reader continue to be stored in the same stacks. When the projection of the 40th frame ends, the stacks will be completely filled with data. The contents of an arbitrary Nth stack form an integrated code of two intersecting rays at points N. Next, a program is launched that directly calculates the coordinates of the points on the surface of the object. The data stored in each stack, it converts into the coordinates of the pixels of the first and second projectors

,

. Here, the superscript indicates the stack number, and the subscript indicates the projector number. These coordinates are substituted respectively in the 1st and 2nd equations, where the coordinates of the directing vectors of the rays emitted by these pixels are calculated.

The coordinates of the first projector - X _A , Y _A , Z _A and the calculated coordinates of the directing vectors of the straight line AN are substituted into the 3rd equation:

The coordinates of the second projector - XB, Y _B , Z _B and the calculated coordinates of the directing vectors of the line BN are substituted into the 4th equation:

The coordinates of point N of the surface of the object will be a solution to the system of these two equations. The solutions of N such systems determine the coordinates of N points on the surface of the object.

Claims (1)

A projection coding method for digitizing space points, comprising the steps of: selecting a coordinate system and directly measuring the data necessary to determine the equations of lines along which the rays emitted by the projectors propagate; project using an at least one projector into the measured region of space an array of narrowly directed electromagnetic rays, each of which contains information that uniquely identifies this beam, while this information is expressed as a code and is functionally related to the equation of the straight line along which this beam propagates ; using at least one reader, these beams are recorded in that area of space where they can be uniquely identified by the codes contained in these beams, while if codes from at least two different beams are recorded at the point N belonging to the specified area , then the coordinates of the point N relative to the selected coordinate system are found as a solution to the system of equations of lines along which these rays propagate; projectors and reading devices are synchronized and controlled by a computer, in the memory of which codes corresponding to projected beams into space are stored.

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