TWI444597B - Apparatus and method for measuring distances - Google Patents

Description

Distance measuring device and method

The present invention relates to an apparatus and method for measuring distance, and more particularly to an apparatus and method for measuring distance using light.

Engineering techniques often require distance measurements, such as engineering surveying, dynamic distance measurement during vehicle travel, and reversing detection distance. Distance measurement is also often performed in various electronic devices. For example, a digital camera performs autofocus by measuring the distance between the lens and the object to be photographed, and the projector can realize autofocus by measuring the distance between the projection lens and the projection screen.

Typical distance measurement methods include pulse method, phase method, and the like. The principle of the pulse method is: the light emitter emits a light pulse to the object to be tested, and the light receiver is disposed at the light emitter for receiving the light signal reflected by the object to be tested, by calculating the period from the transmission to the reception of the light pulse Calculate the distance of the object to be measured at the time. The principle of the phase method is: the light emitter emits the phase-modulated optical signal to the object to be tested, and the optical signal reflected by the object to be measured is superimposed with the original light at the optical receiver, and is received by the calculation optical receiver. The phase of the optical signal to calculate the distance of the object to be measured.

The above-mentioned distance measurement method requires a complicated instrument, and requires subsequent high-precision circuit systems to perform calculations.

In view of this, it is necessary to provide a distance measuring device having a simple structure.

In addition, it is necessary to provide a distance measurement method.

A distance measuring device includes a lens group, an optical receiver and a computing module. An object to be measured is imaged at the light receiver through the lens group, and the light receiver receives an image formed by the object to be measured through the lens group and generates a corresponding image sensing signal. The lens group has a focal plane that is at a non-perpendicular angle to the optical axis. The computing module calculates the distance between the object to be measured and the distance measuring device by using the imaging formula of the lens group to perform high frequency selection.

A distance measuring method includes: receiving an image of an object to be measured, and generating a corresponding image sensing signal; performing high frequency selection on the image sensing signal; and calculating the object to be measured according to the image signal of the high frequency portion The distance.

The distance measuring device and method perform high frequency selection by using an image formed by the object to be measured through the lens group to obtain a boundary between the focus and the non-focus, and then restore the object to be measured by the imaging formula of the lens group. The distance.

12‧‧‧ lens group

16‧‧‧ objects to be measured

202‧‧‧First lens

14‧‧‧Optical Receiver

200‧‧‧ focal plane

204‧‧‧second lens

162, 164, 166, 168‧‧ ‧ position of the object to be measured

162', 164', 166', 168'‧‧‧ image grayscale high position

30‧‧‧Objects to be imaged

304‧‧‧First lens group

308‧‧‧ sensor

182‧‧‧data receiving unit

186‧‧‧Comparative unit

190‧‧‧ data output unit

302‧‧‧Switch

306‧‧‧second lens group

18, 310‧‧‧ Calculation Module

184‧‧‧First calculation unit

188‧‧‧Second calculation unit

1 is a schematic structural view of a distance measuring device according to a preferred embodiment of the present invention.

2 is a light path diagram of distance measurement performed by the distance measuring device shown in FIG. 1.

3 is an induced voltage curve of an image gradation received by the optical receiver shown in FIG. 1 in an embodiment.

4 is a schematic structural view of an image forming apparatus using a distance measuring device according to a preferred embodiment of the present invention.

FIG. 5 is a schematic structural diagram of the computing module shown in FIG. 1.

6 is a flow chart of a distance measuring method according to a preferred embodiment of the present invention.

Referring to FIG. 1, a preferred embodiment of the distance measuring device of the present invention includes a lens group 12 and a light receiver 14.

The lens group 12 is disposed between an object to be measured 16 and the light receiver 14. The light receiver 14 senses an image formed by the object 16 to be measured through the lens group 12 and generates a sensing signal.

The lens group 12 includes a first lens 202 and a second lens 204. The object to be measured 16 is sequentially imaged through the first lens 202 and the second lens 204 on the light receiver 14. In this embodiment, the first lens 202 is a convex lens, and the focal plane 200 of the second lens 204 has a predetermined non-vertical angle with the optical axis.

The light receiver 14 is configured to sense an image formed by the object 16 to be measured through the lens group 12 and generate a corresponding sensing signal. In this embodiment, the sensing signal can be obtained by scanning the gradation of the image received by the optical receiver 14. The principle is that by scanning the image received by the light receiver 14, a series of induced voltage values corresponding to the gray level of the image can be obtained, and after sampling, a set of discrete images representing the gray level of the image can be generated. The scanning signal can be expressed in a matrix form.

Referring to Fig. 2, it is an optical path diagram for performing distance measurement by the distance measuring device shown in Fig. 1. When the distance measurement is performed, the object to be measured 16 and the light receiver 14 are respectively located on both sides of the lens group 12. Within the effective imaging range of the lens group 12, the distance between the object 16 to be measured and the lens group 12 can be mapped and reflected as different positions of the gray level of the image received on the light receiver 14. . By scanning the light receiver 14 The upper image is analyzed and the high point of the gray scale is analyzed, and then the mapping calculation is performed to obtain the distance between the object to be measured 16 and the distance measuring device. As shown in FIG. 2, when the object to be measured 16 is at the positions of 162, 164, 166, and 168, respectively, the high points of the gradations on the image formed by the lens group 12 are 162', 164', 166', respectively. 168'.

Please refer to FIG. 3 , which is an image induced voltage curve received by the light receiver 14 after the object 16 to be measured is imaged by the lens group 12 in an embodiment. In the figure, when the optical receiver 14 scans the focus of the object 16 to be measured through the lens group 12, the image gradation is higher, and thus the image induced voltage is higher, and when the focus is not at the focus, the image is Like the lower gray level, the image induced voltage is lower. At the boundary between the focus and the non-focus, a more pronounced grayscale step is formed.

The computing module 18 shown in FIG. 1 can calculate the distance between the object 16 to be measured and the distance measuring device by calculating the image scanning signal generated by the optical receiver 14. The discrete induced voltage value of the gray scale of the representative image is subjected to a predetermined operation to obtain a frequency domain distribution of the image of the object to be measured 16 transmitted through the lens group 12 on the light receiver 14. In the image frequency, the high frequency portion is shown as a region where the image gradation change rate is high. In this embodiment, the predetermined operation is a two-dimensional Fourier transform.

The results of the above predetermined calculations are compared and screened to obtain the portion with the highest frequency in the frequency distribution. Since the gradient of the gray level of the image at the boundary between the focus and the non-focus is most obvious during the imaging process, the portion with the highest frequency in the frequency domain distribution of the image corresponds to the focus of the object 16 to be measured imaged at the light receiver 14. The focal point of non-focus.

The distance between the object to be measured 16 and the distance measuring device can be calculated by performing the second predetermined operation on the portion of the image signal having the highest frequency. The second time The predetermined operation may be: first obtaining a gray point of the image, that is, a position of the focus and the non-focus boundary by a two-dimensional Fourier transform, and then graying the image by the imaging formula of the lens group 12. The position of the high point is mapped to the distance from the lens group 12, so that the distance between the object to be measured 16 and the distance measuring device can be calculated.

Please refer to FIG. 4, which is a schematic diagram of the distance measuring device of the present invention used in an image forming apparatus. The imaging device can be a camera, a detector, or the like. The imaging device includes a switch 302, a first lens group 304, a second lens group 306, a sensor 308, a computing module 310, and the like.

When the object to be imaged 30 is located in front of the imaging device, the switch 302 can switch the light reflected or emitted by the object 30 to be imaged to the first lens group 304 or the second lens group 306 as needed, respectively Used for photo imaging or distance measurement.

The first lens group 302 is configured to focus the light reflected or emitted by the image forming object 30 onto the sensor 308 to provide the sensor 308 to take a picture or image sample of the object 30 to be imaged.

The second lens group 306 is a lens group 12 shown in FIG. 1 having a focal plane that is at a non-perpendicular angle to the optical axis for forming a distance on the sensor 308 that reflects the object 30 to be imaged. An image of a grayscale high point of a near and far image.

The sensor 308 is configured to image the light obtained by the first lens group 302 or the second lens group 306 to form an electrical signal reflecting the imaged image.

The calculation module 310 is configured to calculate the image signal obtained by the sensor 308 when the switch 302 is switched to the second lens group 306, so that the object to be imaged 30 and the imaging device can be obtained. the distance.

The imaging device shown in FIG. 4 uses the switch 302 to perform conversion between imaging and ranging A sensor 308 can be utilized for multiplexing to achieve imaging and distance measurements.

Referring to FIG. 5, each functional module of the computing module 18 includes a data receiving unit 182, a first computing unit 184, a comparing unit 186, a second computing unit 188, and a data output. Unit 190.

The data receiving unit 182 is configured to receive the image scanning signal generated by the optical receiver 14 and transmit the image scanning signal to the first computing unit 184. The image scanning signal generated by the optical receiver 14 can be a discrete two-dimensional image signal, which is represented in a matrix form.

The first calculating unit 184 is configured to perform a first predetermined calculation on the image scanning signal transmitted by the data receiving unit 182. In this embodiment, the first predetermined calculation is a discrete two-dimensional Fourier transform. After the first predetermined calculation, the first calculating unit 184 generates a frequency domain signal and transmits the signal to the comparing unit 186.

The comparing unit 186 is configured to compare the frequency domain signals generated by the first calculating unit 184 to obtain an image signal corresponding to the portion with the highest frequency, and the comparing unit 186 has the highest frequency in the frequency domain signal. The image signal is transmitted to the second computing unit 188.

The second calculating unit 188 is configured to perform a second predetermined calculation on the image signal sent by the comparing unit 186, thereby obtaining a distance between the object to be measured 16 and the distance measuring device. The distance calculated by the second calculating unit 188 is output via the data output unit 190.

Referring to Figure 6, the distance measurement method of the present invention comprises the following steps:

Step 402: The object 16 to be measured is imaged on the optical receiver 14 through the lens group 12, and the optical receiver 14 scans to obtain a discrete two-dimensional image signal. The image signal is transmitted to the computing module 18.

In step 404, the data receiving unit 182 of the computing module 18 receives the two-dimensional image signal and transmits the two-dimensional image signal to the first computing unit 184.

Step 406, the first calculating unit 184 performs a first predetermined calculation on the received two-dimensional image signal to obtain a frequency domain distribution of the two-dimensional image, and generates a frequency signal. In this embodiment, the first predetermined calculation is a discrete two-dimensional Fourier transform.

In step 408, the comparing unit 186 compares the frequency signals generated by the first calculating unit 184 to obtain an image signal of a higher frequency portion.

In step 410, the second calculating unit 188 performs the second predetermined calculation on the image signal of the higher frequency portion generated by the comparing unit 186, and calculates the object to be measured 16 and the image according to the imaging formula of the lens group 12. The distance between the distance measuring devices. In this embodiment, the second predetermined calculation is a discrete two-dimensional Fourier transform.

In step 412, the data output unit 190 outputs the distance calculated by the second calculating unit 188.

The distance measuring device and method perform high frequency selection by an image formed by the object to be measured through the lens group to obtain a boundary between the focus and the non-focus, and then the image is restored by the imaging formula of the lens group. Measure the distance of the object.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above description is only a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above-described embodiments, and those skilled in the art will be able to make equivalent modifications or variations in accordance with the spirit of the present invention. Should be covered in the scope of the following patent application .

12‧‧‧ lens group

16‧‧‧ objects to be measured

202‧‧‧First lens

18‧‧‧Computation Module

14‧‧‧Optical Receiver

200‧‧‧ focal plane

204‧‧‧second lens

Claims (7)

A distance measuring device includes a lens group, a light receiver and a computing module, wherein the object to be measured is imaged at the light receiver through the lens group, and the light receiver receives the object to be measured through the lens group The image is formed and the corresponding image sensing signal is generated. The improvement is that the lens group has a focal plane that is at a non-perpendicular angle to the optical axis, and the computing module performs high frequency selection on the image sensing signal by using the lens. The imaging formula of the group calculates the distance between the object to be measured and the distance measuring device; wherein the computing module includes a first calculating unit, a comparing unit, and a second calculating unit, and the first calculating unit is configured to The image sensing signal is subjected to frequency domain conversion, and the comparing unit is configured to select a portion of the high frequency according to the frequency domain conversion result of the first calculating unit, where the second calculating unit is configured to borrow the image signal of the high frequency portion The distance of the object to be measured is calculated from the imaging formula of the lens group. The distance measuring device of claim 1, wherein the image of the object to be measured transmitted through the lens group on the light receiver has a map indicating a distance between the object to be measured and the distance measuring device. Like grayscale high. The distance measuring device of claim 1, wherein the object to be measured is formed within a focal length of the lens group, and a focus with a higher image gradation is formed on the light receiver, the focus is The position on the light receiver corresponds to the distance between the object to be measured and the lens group. The distance measuring device of claim 1, wherein the first calculating unit performs a Fourier transform on the image sensing signal to frequency-convert the image sensing signal, the second calculating unit is high The image signal of the frequency portion is Fourier transformed, and the distance of the object to be measured is calculated by the imaging formula of the lens group. A distance measurement method comprising: Receiving an image of the object to be measured, and generating a corresponding image sensing signal; performing frequency domain conversion on the image sensing signal; determining a high frequency portion of the frequency of the image sensing signal by comparing; The image signal is subjected to a predetermined calculation; the distance of the object to be measured is calculated according to an imaging formula of the object to be measured. The distance measuring method according to claim 5, wherein the step of performing frequency domain conversion on the image sensing signal is performed by Fourier transforming the image sensing signal. The distance measuring method of claim 5, wherein the predetermined calculation is a Fourier transform.