JP2015064212A - Illumination statistic measurement device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring technology of illumination statistic capable of measuring statistic other than average intensity of a light field that affects the color and texture of an object sensed by a human.SOLUTION: A luminance image generation unit 1 photographs a space as a target of calculation of illumination statistic using a wide angle lens, and calculates the luminance values of pixels constituting the image obtained by the photographing or calculates the differential values of the luminance values. On the basis of the calculated luminance values and the differential values of them, a statistic calculation unit 2 calculates the statistic of a histogram about the luminance values of the pixels of the image or the differential values of them.

Description

  The present invention relates to a technique for calculating statistics related to lighting.

  In an environment where people live, illumination light always includes indirect reflections from walls and floors, and there may be multiple light sources. In such an environment, the lighting has a complex spatial pattern of light intensity from various directions. This pattern is called the light field.

  Conventionally, an illuminometer has been widely used as a device for measuring the brightness of an optical field such as a room. The illuminometer currently in wide use is a portable device that receives illumination light collected from various directions via an optical lens by a light receiving element and records and displays only the average intensity thereof.

  Here, it is known that the average intensity of the light field hardly affects the perceptual impression such as the color and texture of the object placed in the light field (see, for example, Non-Patent Document 1).

L.T.Maloney, B.A.Wandell, “Color constancy: a method for recovering surface spectral reflectance”, Journal of the Optical Society of America A, 1986, Vol.3, P.29-33.

  Conventional illuminometers cannot measure statistics other than the average intensity of illumination (light field) that affect the color and texture of objects perceived by humans.

  An object of the present invention is to provide an illumination statistic measuring apparatus and method for measuring a statistic other than the average intensity of a light field that affects the color and texture of an object perceived by a human.

  According to the illumination statistic measurement device according to one aspect of the present invention, a space that is an object of calculation of illumination statistic is photographed using a wide-angle lens, and the luminance value of each pixel constituting the image obtained by the photographing Or a luminance image generation unit that calculates a differential value thereof, and a statistic calculation unit that calculates a statistical value relating to the histogram of the luminance value of the pixel of the image or the differential value based on the calculated luminance value or the differential value thereof; ,including.

  Statistics other than the average intensity of the light field that affect the color and texture of objects perceived by humans can be measured.

The block diagram for demonstrating the example of an illumination statistic measurement apparatus. The flowchart for demonstrating the example of the illumination statistic measuring method. The flowchart for demonstrating the example of the illumination statistic measuring method.

  Embodiments of the present invention will be described below with reference to the drawings.

  The structure of the light field changes in a complex manner depending on the nature of the light source and the environment, but the impression of the lightness and texture of objects perceived by humans changes according to low-order statistics relating to a simple histogram of the light field. Therefore, it is considered that a relative change in the texture and impression of an object perceived by humans can be predicted only by calculating low-order statistics relating to these histograms.

  Based on such an idea, in the embodiments of the present invention described below, for example, low-order statistics (average luminance, standard deviation, skewness, kurtosis, etc.) of an image of a light field photographed through a fisheye lens are calculated. Is done.

  As shown in FIG. 1, the illumination statistic measuring apparatus according to an embodiment of the present invention includes, for example, a luminance image generation unit 1, a statistic calculation unit 2, and a display unit 3. The lighting statistic measurement method has the steps shown in FIG.

  The illumination statistic measurement device is arranged in a light field that is a target of measurement of the statistic.

  The luminance image generation unit 1 shoots a space that is subject to calculation of illumination statistics using a wide-angle lens with a wide angle of view, and calculates the luminance value of each pixel constituting the image obtained by the shooting or a differential value thereof. Calculate (step S1). The calculated luminance value or its differential value is provided to the statistic calculator 2.

  As illustrated in FIG. 1, the luminance image generation unit 1 includes a lens unit 11, a light receiving unit 12, and a luminance value conversion unit 13, for example. As described below, the lens unit 11, the light receiving unit 12, and the luminance value conversion unit 13 perform the processing from step S11 to step S13 shown in FIG. 2, thereby realizing the processing in step S1.

  The lens unit 11 is a wide-angle lens with a wide angle of view, and the wide-angle lens with a wide angle of view disposed on the top of the illumination statistic measuring device allows the top view of the illumination statistic measuring device to be viewed at a viewing angle of, for example, 180 degrees. The captured image is formed (step S11). A wide-angle lens with a wide angle of view is, for example, a fisheye lens.

  The light receiving unit 12 captures the image formed by the lens unit 11 with the light receiving element, and converts the image into a digital image V (x, y) having the number of pixels m × n (step S12). m and n are integers of 8 or more. m = n may be sufficient. x is an integer from 1 to m and y is an integer from 1 to n. The type of the light receiving element or the analog / digital converter is not limited. The digital image V (x, y) is, for example, a gray scale image signal. The digital image V (x, y) is provided to the luminance value conversion unit 13.

  Although m and n are 8 or more, they may be integers that are not too large. That is, the digital image V (x, y) may be a low resolution image.

  The luminance value conversion unit 13 converts the pixel value V (x, y) of each pixel of the digital image into a luminance value according to, for example, the following power function (step S13). When the later-described differentiating unit 14 is not provided, the converted luminance value is set to I (x, y) and provided to the statistic calculation unit 2.

  Here, A and γ are conversion parameters, which are predetermined values. These conversion parameters are estimated in advance. For example, the pixel value is measured by irradiating the light receiving unit 12 with visible light having various luminances, and the above equation is applied to the data by the least square method.

  Note that the luminance image generation unit 1 may further include a differentiation unit 14. When the differentiating unit 14 is provided, the luminance value converted by the luminance value converting unit 13 is provided to the differentiating unit 14. The differentiating unit 14 calculates the differential value of the luminance value of each pixel constituting the image obtained by the above photographing. Differentiation of the luminance value of the pixel of the image is performed by using a predetermined differential operator or a predetermined differential filter. As described above, when the differentiating unit 14 is provided, the differential value of the luminance value is set to I (x, y) instead of the converted luminance value, and is provided to the statistic calculation unit 12. .

  The statistic calculation unit 2 calculates a statistic related to the histogram of the luminance value of the pixel of the image or its differential value based on I (x, y), that is, based on the calculated luminance value or its differential value. (Step S2). The statistics relating to the calculated histogram are provided to the display unit 3.

  The statistics relating to the histogram are, for example, the average value of the luminance value of the image pixel or the differential value thereof, the luminance value of the image pixel or the standard deviation of the differential value, and the luminance value of the image pixel or the differential value thereof. It is at least one of the skewness and the luminance value of the pixel of the image or the kurtosis of its differential value. The statistics regarding these histograms are defined as follows, for example.

  The average value of the luminance value of the pixel of the image or its differential value is a mean defined by the following equation, for example.

  The standard deviation of the luminance value of the pixel of the image or its differential value is, for example, sd defined by the following equation.

  The skewness of the luminance value of the pixel of the image or its differential value is skew defined by the following equation, for example.

  The luminance value of the pixel of the image or the kurtosis of the differential value is, for example, kurtosis defined by the following equation.

  The display unit 3 displays a statistic relating to the calculated histogram (step S3). The calculated statistics regarding the histogram are displayed as numbers or graphs, for example.

  The larger the standard deviation and the skewness, the higher the glossiness and the lower the lightness. Also, the greater the kurtosis, the sharper the impression of gloss. The average does not affect the appearance of the object, but it is useful for adjusting the exposure time of the camera as in the existing luminometer.

  According to the lighting statistics measurement device, it is possible to easily know parameters that have a large effect on the gloss and brightness of objects perceived by humans (lighting environment (light field) parameters that have a large effect on human perception). . Accordingly, it is possible to examine the arrangement of effective lighting in shooting of a product or a person or display of a store in consideration of gloss and brightness perceived by humans while viewing displayed parameter values.

  Any of the statistics related to the above-mentioned histogram is a simple statistic with a low dimension and can be obtained with a small amount of calculation. Therefore, by calculating only the statistics related to these low-dimensional and simple histograms, the lighting statistic calculation device can be made compact, lightweight, and energy-saving.

  Further, since the amount of calculation can be further reduced by reducing the image resolution, the lighting statistic calculation device can be further reduced in size, weight, and energy saving.

[Modifications, etc.]
Instead of the display unit 3 or together with the display unit 3, the output unit 4 may be provided in the illumination statistic measuring device. In this case, the statistic related to the histogram calculated by the statistic calculator 2 is provided to the output unit 4. The output unit 4 outputs a statistic regarding the calculated histogram (step S4). For example, the calculated statistic regarding the histogram is output as digital data to an external device such as a camera. This makes it possible to adjust shooting parameters in an external device such as a camera according to the illumination.

  The various processes described above are not only executed in time series according to the description, but may also be executed in parallel or individually as required by the processing capability of the apparatus that executes the processes. Needless to say, other modifications are possible without departing from the spirit of the present invention.

  When the above configuration is realized by a computer, the processing contents of the functions that each device should have are described by a program. By executing this program on a computer, the above processing functions are realized on the computer. The program describing the processing contents can be recorded on a computer-readable recording medium. An example of a computer-readable recording medium is a non-transitory recording medium. Examples of such a recording medium are a magnetic recording device, an optical disk, a magneto-optical recording medium, a semiconductor memory, and the like.

  This program is distributed, for example, by selling, transferring, or lending a portable recording medium such as a DVD or CD-ROM in which the program is recorded. Furthermore, the program may be distributed by storing the program in a storage device of the server computer and transferring the program from the server computer to another computer via a network.

  A computer that executes such a program first stores, for example, a program recorded on a portable recording medium or a program transferred from a server computer in its own storage device. When executing the process, this computer reads a program stored in its own recording device and executes a process according to the read program. As another execution form of the program, the computer may read the program directly from the portable recording medium and execute processing according to the program, and each time the program is transferred from the server computer to the computer. The processing according to the received program may be executed sequentially. The above-described processing may be executed by a so-called ASP (Application Service Provider) type service that realizes a processing function only by an execution instruction and result acquisition without transferring a program from the server computer to the computer. Good.

  In the above embodiment, the processing functions of the apparatus are realized by executing a predetermined program on a computer. However, at least a part of these processing functions may be realized by hardware.

[Application example]
Hereinafter, application examples of the present invention will be described.

  The first application example is a preliminary examination of lighting device arrangement in the production of live-action video works such as movies. In a live-action video work such as a movie, using a lighting statistic measurement device that adjusts the illumination using a light or reflector to shoot the subject in the desired form, even if the subject is not on the spot, By placing the lighting statistic measuring device at a desired position, the color and texture of the subject to be photographed can be predicted to some extent.

  The second application example is a preliminary study of outdoor lighting in the production of live-action video works such as movies. In outdoor filming, the lighting conditions are greatly affected by the weather. It is difficult to know whether or not it is the weather that allows the subject to be photographed in a desired form only by readily available weather data. However, it is possible to know whether the weather is suitable for photographing by installing an illumination statistic measuring device at or around the photographing location and monitoring the external output data. In addition, it is also possible to search for a more suitable place for photographing by carrying and moving the illumination statistic measuring device.

  The third application example is evaluation of the light environment of a building. In buildings such as houses, restaurants, and public facilities used by humans, the quality of the light environment in the interior is particularly emphasized. The light environment changes in a complex manner depending on the arrangement of walls and windows, and the number and arrangement of lights. By using the lighting statistic measurement device, one of useful indexes for evaluating the quality of the light environment can be provided as an objective numerical value that does not depend on the subjectivity of the designer or the client.

DESCRIPTION OF SYMBOLS 1 Luminance image generation part 11 Lens part 12 Light receiving part 12 Statistics calculation part 13 Luminance value conversion part 14 Differentiation part 2 Statistics calculation part 3 Display part 4 Output part

Claims (7)

A luminance image generation unit that shoots a space that is subject to calculation of illumination statistics using a wide-angle lens, and calculates a luminance value of each pixel constituting the image obtained by the shooting or a differential value thereof,
A statistic calculation unit that calculates a statistic relating to a histogram of the luminance value of the pixel of the image or the differential value thereof based on the calculated luminance value or the differential value thereof;
Lighting statistics measurement device including In the lighting statistic measuring device according to claim 1,
The statistics related to the histogram are the luminance value of the pixel or the average value of the differential value, the standard value of the luminance value of the pixel or the differential value, the skewness of the luminance value of the pixel or the differential value, and the At least one of the luminance value of the pixel or the kurtosis of its differential value,
Lighting statistics measurement device. In the lighting statistic measuring device according to claim 2,
The input image is assumed to be composed of m × n pixels, and the luminance value of the pixel (x, y) or a differential value thereof is I (x, y).
The average value of the luminance value of the pixel or its differential value is a mean defined by the following equation:

The standard deviation of the luminance value of the pixel or its differential value is sd defined by the following equation:

The skewness of the luminance value of the pixel or its differential value is skew defined by the following equation:

The luminance value of the pixel or the kurtosis of its differential value is kurtosis defined by the following equation:

Lighting statistics measurement device. In the lighting statistic measuring device according to any one of claims 1 to 3,
The input image is a low resolution image having 8 × 8 or more pixels.
Lighting statistics measurement device. In the lighting statistic measuring device according to any one of claims 1 to 4,
A display unit for displaying statistics regarding the calculated histogram;
An illumination statistic measuring device further comprising: In the lighting statistic measurement device according to any one of claims 1 to 5,
An output unit for outputting statistics on the calculated histogram;
An illumination statistic measuring device further comprising: Luminance image generation unit that shoots a space for calculation of illumination statistics using a wide-angle lens and calculates a luminance value or a differential value of each pixel constituting an image obtained by the shooting Steps,
A statistic calculator that calculates a statistic relating to a histogram of the luminance value of the pixel of the image or its differential value based on the calculated luminance value or its differential value;
Lighting statistics measurement method including

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