CN105357520B - Measure the method and device of camera exposure time - Google Patents

Abstract

The invention provides a method and device for measuring camera exposure time. The method includes: for a plurality of light-emitting devices placed in front of the camera under test to form a two-dimensional array, control the light-emitting devices in different columns or rows to light up and extinguish sequentially according to different light-emitting periods; an image of the controlled light-emitting device array; and determining a reference column or reference row of light-emitting devices in the image, and calculating an exposure time of the camera under test based on the light-emitting period of the reference column or reference row of light-emitting devices, wherein the reference Each light-emitting device of the column or reference row of light-emitting devices has the closest brightness in the image, or, the number of light-emitting devices in the light-emitting state of the reference column or reference row of light-emitting devices in the image is not less than a predetermined threshold. The method and device for measuring the exposure time of the camera provided by the invention can calculate the exposure time of the camera according to the images captured by the camera, which not only has high precision, but also has low cost and is easy to implement.

Description

Method and device for measuring camera exposure time

technical field

The invention relates to the technical field of image processing, in particular to a method and device for measuring camera exposure time.

Background technique

Camera exposure time is the time interval from when the shutter opens to when it closes, during which time an object can leave an image on the film. The exposure time depends on the needs, and different applications may require different exposure times. When evaluating a camera product, it is important to obtain the exposure time that the camera actually used when capturing the image. However, many camera products, especially USB cameras, do not output its current exposure time. Therefore, there is a need for a method or device for measuring camera exposure time.

Contents of the invention

Aiming at the deficiencies of the prior art, on the one hand, the present invention provides a method for measuring the exposure time of a camera, the method comprising: for a plurality of light emitting devices arranged in a two-dimensional array in front of the camera under test, according to different light emitting periods Control the light-emitting devices in different columns or rows to emit light and turn off sequentially; receive the image of the controlled light-emitting device array captured by the camera under test; and determine the reference column or reference row of light-emitting devices in the image, and based on the The exposure time of the camera under test is calculated by the light-emitting period of the light-emitting devices of the reference column or row, wherein the brightness of each light-emitting device of the light-emitting devices of the reference column or row is the closest in the image, or the brightness of the light-emitting devices of the reference column is the closest Or the number of light-emitting devices in the light-emitting state of the reference row of light-emitting devices in the image is not less than a predetermined threshold.

In one embodiment of the present invention, the light-emitting period used to control the light-emitting devices of each column or row increases proportionally with the increase of the number of columns or rows.

In one embodiment of the present invention, when multiple columns or rows of light-emitting devices appear in the image and the brightness of each light-emitting device is close, select a column or row with the largest light-emitting period as the reference column or row of light-emitting devices .

In one embodiment of the present invention, it is determined whether the light emitting device is in a light emitting state by determining whether the pixel value of the light emitting device at a corresponding position in the image exceeds a preset threshold.

In one embodiment of the present invention, the light emitting device is a light emitting diode.

On the other hand, the present invention is also a device for measuring the exposure time of a camera. The device includes: a control module, which is used to control a plurality of light-emitting devices arranged in a two-dimensional array in front of the camera under test according to different light-emitting periods. The light-emitting devices in different columns or rows are sequentially illuminated and extinguished; the receiving module is used to receive the image of the controlled light-emitting device array captured by the camera under test; and the analysis module is used to determine the reference column or row in the image. A reference row of light-emitting devices, and calculate the exposure time of the camera under test based on the light-emitting period of the reference column or reference row of light-emitting devices, wherein the brightness of each light-emitting device of the reference column or reference row of light-emitting devices in the image is The number of light-emitting devices that are closest to, or, said reference column or reference row light-emitting device in said image in a light-emitting state is not less than a predetermined threshold.

In one embodiment of the present invention, the light-emitting period used to control the light-emitting devices of each column or row increases proportionally with the increase of the number of columns or rows.

In an embodiment of the present invention, when there are multiple columns or rows of light-emitting devices in the image and the brightness of each light-emitting device is close, the analysis module selects a column or a row with the largest light-emitting period as the reference column or row. Reference row luminaire.

In one embodiment of the present invention, the analysis module determines whether the light emitting device is in a light emitting state by determining whether the pixel value of the light emitting device at a corresponding position in the image exceeds a preset threshold.

In one embodiment of the present invention, the light emitting device is a light emitting diode.

The method and device for measuring the exposure time of the camera provided by the invention can calculate the exposure time of the camera according to the images captured by the camera, which not only has high precision and low cost, but also is easy to implement.

Description of drawings

The following drawings of the invention are hereby included as part of the invention for understanding the invention. The accompanying drawings illustrate embodiments of the invention and description thereof to explain principles of the invention.

In the attached picture:

FIG. 1 shows a flow chart of a method for measuring camera exposure time according to an embodiment of the present invention;

2 shows an example of a two-dimensional array of light emitting devices placed in front of the camera under test according to an embodiment of the present invention; and

Fig. 3 shows a structural block diagram of an apparatus for measuring camera exposure time according to an embodiment of the present invention.

detailed description

In the following description, numerous specific details are given in order to provide a more thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without one or more of these details. In other examples, some technical features known in the art are not described in order to avoid confusion with the present invention.

It should be understood that the invention can be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the/the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. It should also be understood that the terms "consists of" and/or "comprising", when used in this specification, identify the presence of stated features, integers, steps, operations, elements and/or parts, but do not exclude one or more other Presence or addition of features, integers, steps, operations, elements, parts and/or groups. As used herein, the term "and/or" includes any and all combinations of the associated listed items.

In order to thoroughly understand the present invention, detailed steps and detailed structures will be provided in the following description, so as to illustrate the technical solution of the present invention. Preferred embodiments of the present invention are described in detail below, however, the present invention may have other embodiments besides these detailed descriptions.

Embodiments of the present invention provide a method for measuring camera exposure time, which is used to calculate the camera exposure time from images captured by the camera. The method is described in detail below in conjunction with FIG. 1 . Fig. 1 shows a flowchart of a method 100 for measuring camera exposure time according to an embodiment of the present invention. As shown in Figure 1, the method 100 includes the following steps:

Step 101: For the plurality of light-emitting devices arranged in a two-dimensional array in front of the camera under test, control the light-emitting devices in different columns (or rows) to emit light and turn off sequentially according to different light-emitting periods.

Exemplarily, the light emitting device may be a light emitting diode (LED). M*N light-emitting diodes can be placed in front of the camera under test to form a light array of M rows and N columns, and each light-emitting diode in each column is controlled to light up and turn off sequentially according to different light-emitting periods. Or the light emitting diodes in each row are controlled to emit light and turn off sequentially according to different light emitting periods.

FIG. 2 shows an example of a two-dimensional array of light emitting devices placed in front of a camera under test according to an embodiment of the present invention. As shown in FIG. 2 , each small circle represents a light emitting device, and the light emitting device is an LED. In Fig. 2, an LED lamp array with M rows and N columns is shown. For the sake of simplicity, only M=3, and the following is only an exemplary description of the light-emitting diodes in each of the N columns being controlled to emit light sequentially according to different light-emitting periods. and off. Similarly, those of ordinary skill in the art can understand that the light emitting diodes in each row are controlled to emit light and turn off sequentially according to different light emitting periods.

As shown in FIG. 2 , N rows of light arrays are arranged in a horizontal line in front of the camera under test (not shown), so that the light bars are at the edge of the image of the camera under test. N rows of lamp arrays can also be referred to as N groups of lamp arrays, and the lamps in each group are arranged vertically. These N groups of lamps can be numbered as 1-N from left to right.

Through the controller, the LEDs can be controlled to light up in sequence according to the pre-designed pattern, that is, each column of LEDs can be controlled to light up and turn off in sequence according to different light-emitting cycles, and the image of the controlled LED light array can be captured by the camera under test. Specifically, for the 3 lights in the i-th group, these 3 lights are controlled to turn on for a period of time Ti in turn, that is:

0) Turn on the first light among the three lights;

1) Wait for Ti time;

2) Turn off the first light among the three lights, and turn on the second light among the three lights;

3) Waiting for Ti time;

4) Turn off the second lamp in the three lamps, and turn on the third lamp in the three lamps;

5) Waiting for Ti time;

6) Turn off the third of the three lights and go back to 0) to start over.

The time Ti used by each group of lamps can form an increasing geometric sequence, which is used to control the light-emitting period of each column (or row) of light-emitting devices to increase proportionally with the increase of the number of columns (or rows). Using a geometric sequence can make the relative error limit of the measured value consistent within the measurement range. Exemplarily, T1=1/3ms, T(i+1)=1.2Ti.

Step 102: Receive an image of the controlled light emitting device array captured by the camera under test.

Exemplarily, any wireless transmission or wired transmission technology known to those of ordinary skill in the art can be used to receive the image captured by the camera under test about the controlled light-emitting device array, so as to determine based on the image captured by the camera under test The exposure time of the camera under test.

Step 103: Determine the reference column (or reference row) light-emitting device in the captured image, and calculate the exposure time of the camera under test based on the light-emitting period of the reference column (or reference row) light-emitting device, wherein the reference column (or reference row) light-emitting device Each light-emitting device of the reference row) light-emitting device has the closest brightness in the image, or the number of light-emitting devices in the light-emitting state of the reference column (or reference row) light-emitting device in the image is not less than a predetermined threshold. If in step 101 the lighting and extinguishing of the light-emitting devices is controlled column by column, then in step 103 a reference column of light-emitting devices is determined in the captured image. On the contrary, if in step 101 the light-emitting devices are controlled to turn on and off by row, then in step 103 the reference row of light-emitting devices is determined in the captured image.

In one embodiment of the present invention, a column (or row) with the closest brightness of each light-emitting device can be found in the image as a reference column (or row) of light-emitting devices. For example, each light-emitting device can be judged by visual inspection. Whether the brightness in the image is close, or whether the brightness of each light emitting device in the image is close can be judged through cooperation of a brightness detection device (for example, a brightness sensor) and a processor. If the light-emitting and extinguishing of the light-emitting devices are controlled by column, continue to refer to the example of FIG. 2 . In Figure 2, for the captured light array image, we can find the group with the closest brightness of the three lights in the image among the N light groups, and set it as the i-th group, then the measured value of the exposure time is 3Ti . This is because when the integer multiple of the change period (3Ti) of the lamp group is close to the exposure time, the brightness of the three lamps will be very close to each other. Thus, an estimate of the exposure time for the measured time can be derived. Similarly, those of ordinary skill in the art can understand the process of calculating the exposure time of the camera under test based on the light-emitting period of the light-emitting devices of the reference row when the light-emitting devices are controlled by row to turn on and off.

When the brightness of each light-emitting device of multiple rows of light-emitting devices is close in the captured image, select the column with the largest luminous period (that is, when the brightness of three lamps in multiple groups is all close in Fig. ) as the reference column light-emitting device. Similarly, when multiple rows of light-emitting devices appear in the captured image and the brightness of each light-emitting device is close, the row with the largest light-emitting period is selected as the reference row of light-emitting devices.

In the captured image, if the row (or row) of light-emitting devices with the closest brightness is found by the naked eye, the method of calculating the exposure time of the camera under test based on its light-emitting period can be directly read with the naked eye, which is suitable for applications where the accuracy of the exposure time is not high Scenarios where the camera exposure time is estimated quickly without . If the brightness detection device cooperates with the processor to find a column (or row) of light emitting devices with the closest brightness, the process of calculating the exposure time of the camera under test based on its lighting cycle can be completed by the processor, for example, can be performed by the processor Some calculations get the exposure time of the camera under test to realize automatic measurement with high precision.

In another embodiment of the present invention, a row (or a row) of light-emitting devices whose number of light-emitting devices in the light-emitting state is not less than a predetermined threshold can be found in the captured image as a reference column (or row) of devices. For example, taking controlling the lighting and extinguishing of the light-emitting devices by row as an example, the array of light-emitting devices is controlled to be turned on and off in a pre-designed pattern. Exemplarily, N*M LEDs are arranged in M rows and N columns, where N>=4, M>=1. The lamps in each i row and j column can be in the time period j*Ti～(j+1)*Ti, (j+N)*Ti～(j+N+1)*Ti, (j+2N)*Ti～( j+2N+1)*Ti, ... light up, wherein, Ti is the same time parameter in each row, and increases with i in the form of a geometric sequence. Exemplarily, Ti=1 ms*N ^i/2 .

In the captured image, for example, whether the light-emitting device is in a light-emitting state can be determined by determining whether the pixel value of the light-emitting device at a corresponding position in the image exceeds a preset threshold. For example, if the preset threshold is 200, then when the pixel value of any LED light at the corresponding position in the captured image is greater than 200, it is determined that the LED light is on, otherwise it is not on.

Let Si be the number of lighted lamps in each row, then the smallest i that makes Si not less than a predetermined threshold can be found, for example, the smallest i that makes Si>=3, then Si*Ti is the measured value. The condition of Si>=3 can ensure that the measured value is greater than Ti. Since only the light that is turned on when the camera is exposed will be photographed, the method in this embodiment can measure the camera exposure time. The method in this embodiment is suitable for scenarios that have high requirements for estimation of exposure time or require automatic measurement. The method for measuring camera exposure time according to the above-mentioned embodiments of the present invention calculates the camera exposure time according to the images captured by the camera, which not only has high precision and low cost, but also is easy to implement.

According to another aspect of the present invention, a device for measuring camera exposure time is also provided. Fig. 3 shows a structural block diagram of an apparatus 300 for measuring camera exposure time according to an embodiment of the present invention. As shown in FIG. 3 , the device 300 includes a control module 301 , a receiving module 302 and an analysis module 303 . Wherein, the control module 301 may include a processor, which is used to control the light emitting devices in different columns (or rows) to emit light and Off; the receiving module 302 may include a network cable interface, a USB interface and a corresponding controller for receiving the image of the controlled light emitting device array captured by the camera under test; the analysis module 303 may include a processor for determining the captured image The reference column (or reference row) light-emitting device in the image, and the exposure time of the camera under test is calculated based on the light-emitting period of the reference column (or reference row) light-emitting device. Wherein, each light-emitting device of the reference column (or reference row) of light-emitting devices has the closest brightness in the image, or, the number of light-emitting devices in the reference column (or reference row) of light-emitting devices that are in a light-emitting state in the image is not less than a predetermined threshold .

In one embodiment of the present invention, the light-emitting period used to control each column (or each row) of the light-emitting device increases proportionally with the increase of the number of columns (or rows).

In one embodiment of the present invention, when multiple columns (or rows) of light-emitting devices appear in the captured image and the brightness of each light-emitting device is close, the analysis module 303 selects a column (or row) with the largest light-emitting period as the reference column (or row) Reference row) light emitting device.

In one embodiment of the present invention, the analysis module 303 determines whether the light emitting device is in the light emitting state by determining whether the pixel value of the corresponding position of the light emitting device in the image exceeds a preset threshold.

In one embodiment of the present invention, the light emitting device is a light emitting diode.

The specific process of the operation of each module above can be understood with reference to the embodiment described in FIG. 1 , which will not be repeated here. Each module of the embodiment of the present invention may be realized by hardware, or by a software module running on one or more processors, or by a combination thereof. Those skilled in the art should understand that a microprocessor or a digital signal processor (DSP) can be used in practice to implement some or all functions of some or all components in the device for measuring camera exposure time according to the embodiment of the present invention. The present invention can also be implemented as an apparatus or an apparatus program (for example, a computer program and a computer program product) for performing a part or all of the methods described herein. Such a program for realizing the present invention may be stored on a computer-readable medium, or may be in the form of one or more signals. Such a signal may be downloaded from an Internet site, or provided on a storage carrier, or provided in any other form.

The present invention has been described through the above-mentioned embodiments, but it should be understood that the above-mentioned embodiments are only for the purpose of illustration and description, and are not intended to limit the present invention to the scope of the described embodiments. In addition, those skilled in the art can understand that the present invention is not limited to the above-mentioned embodiments, and more variations and modifications can be made according to the teachings of the present invention, and these variations and modifications all fall within the claimed scope of the present invention. within the range. The protection scope of the present invention is defined by the appended claims and their equivalent scope.

Claims (8)

1. A kind of 1. method for measuring the camera exposure time, it is characterised in that methods described includes：

   For being placed in before tested camera into multiple light-emitting devices of two-dimensional array, different lines are controlled according to different light periods Or each light-emitting device luminous and extinguishing successively do not gone together；

   Receive the image of the array of light emitting devices through control captured by the tested camera；And

   Determine the reference column or reference row light-emitting device in described image, and based on the reference column or reference row light-emitting device Light period calculates the time for exposure of the tested camera,

   Wherein, reference column or the reference row light-emitting device be the brightness in described image of each light-emitting device it is immediate one row or A line, or be the maximum row or one of light period in the immediate multiple row of each light-emitting device brightness in described image or multirow OK；Or the quantity of the reference column or reference row the light-emitting device light-emitting device in luminance in described image is not Less than predetermined threshold.
2. 2. the method as described in claim 1, it is characterised in that for control it is each row or each row light-emitting device light period with The increase equal proportion of columns or line number is incremented by.
3. 3. method as claimed in claim 2, it is characterised in that by determining light-emitting device corresponding position in described image Pixel value whether exceed predetermined threshold value and determine whether light-emitting device is in luminance.
4. 4. the method as described in any one of claim 1-3, it is characterised in that the light-emitting device is light emitting diode.
5. 5. a kind of device for measuring the camera exposure time, it is characterised in that described device includes：

   Control module, for for being placed in before tested camera into multiple light-emitting devices of two-dimensional array, according to different luminous Periodic Control different lines or each light-emitting device luminous and extinguishing successively do not gone together；

   Receiving module, for receiving the image of the array of light emitting devices through control captured by the tested camera；And

   Analysis module, for determining reference column or reference row light-emitting device in described image, and it is based on the reference column or base There won't be any problem the light period of light-emitting device calculates the time for exposure of the tested camera,

   Wherein, reference column or the reference row light-emitting device be the brightness in described image of each light-emitting device it is immediate one row or A line, or be the maximum row or one of light period in the immediate multiple row of each light-emitting device brightness in described image or multirow OK；Or the quantity of the reference column or reference row the light-emitting device light-emitting device in luminance in described image is not Less than predetermined threshold.
6. 6. device as claimed in claim 5, it is characterised in that for control it is each row or each row light-emitting device light period with The increase equal proportion of columns or line number is incremented by.
7. 7. device as claimed in claim 6, it is characterised in that the analysis module is by determining light-emitting device in described image Whether the pixel value of middle corresponding position exceedes predetermined threshold value to determine whether light-emitting device is in luminance.
8. 8. the device as described in any one of claim 5-7, it is characterised in that the light-emitting device is light emitting diode.