Detection method of sinusoidal grating sensing capability based on contrast modulation
Technical Field
The invention relates to the technical field of vision test, in particular to a detection method of sinusoidal grating perception capability based on contrast modulation.
Background
A sinusoidal grating is a special type of grating, which consists of a carrier and a modulation signal together. The carrier may be in the form of a blank or random noise, etc., and the modulation signal is a sinusoidal grating. The application of raster stimulation to cortical visual function testing is different from letter identification such as the E-word on the eye chart. The former relies more on spatial frequency and contrast information contained in the stimulus, while the latter relies on spatial structure information in the stimulus.
Human individuals have varying abilities to perceive sinusoidal raster stimuli. Generally, the smaller the contrast of the sinusoidal grating is, the harder it is for a person to recognize and perceive the sinusoidal grating, and therefore, the perception capability of the sinusoidal grating of an individual human can be tested by changing the contrast of the sinusoidal grating.
Disclosure of Invention
Based on the technical problems in the background art, the invention provides a detection method of the sensing capability of a sinusoidal grating based on contrast modulation;
the invention provides a detection method of sinusoidal grating perception capability based on contrast modulation, which comprises the following steps:
s1, constructing a grating stimulation function based on the average grating brightness, the grating contrast, the grating spatial frequency, the random carrier, the carrier contrast, the grating orientation and the grating phase;
s2, taking preset values of grating average brightness, grating spatial frequency and carrier contrast, taking a first value of grating phase, taking a second value of random carrier, and taking a value C in a grating contrast value range under the condition that the grating orientation is A or BxSubstituting the target grating stimulus image into a grating stimulus function to obtain a target grating stimulus image;
s3, displaying a target grating stimulus diagram to the testee, and receiving a predicted grating direction input by the testee;
s4, when the predicted raster orientation input by the testee is the same as the raster orientation of the target raster stimulus diagram, let Cx=Cx× (1-R) executing step S2 until the predicted raster orientation inputted by the testee is different from the raster orientation of the target raster stimulus diagram, otherwise, let Cx=Cx× (1+ R) executing step S2, until the predicted raster orientation inputted by the testee is the same as the raster orientation of the target raster stimulus diagram, outputting the target raster stimulus diagram, wherein R is a ratio constant;
and S5, outputting the grating contrast of the target grating stimulus pattern, wherein the grating contrast of the target grating stimulus pattern is the grating perception capability of the testee.
Preferably, step S1 specifically includes:
grating stimulus function:
l(x,y)=Lmean×{1+R(x,y)×Cr×{c×sin[2πf(y cosθ-x sinθ)+φ]h, wherein, LmeanIs the average brightness of the grating, C is the grating contrast, f is the grating spatial frequency, R (x, y) is the random carrier, CcCarrier contrast, theta for grating azimuth, and phi for grating phase.
Preferably, in step S2, when A is 0, B is pi/2; when A is pi/4, B is 3 pi/4.
Preferably, in step S2, the first value ranges from 0 to 2 pi.
Preferably, the first value takes any one of values of 0 to 2 pi each time step S2 is performed.
Preferably, the second value is a random value each time step S2 is performed.
The invention shows grating stimulus diagrams with different grating contrasts and different directions to a testee, the testee identifies the grating direction in the grating stimulus diagrams, when the direction identification of the testee is correct, the grating contrast of the grating stimulus diagrams is reduced, the identification difficulty of the testee is increased, and the grating stimulus diagrams are output until the testee cannot identify the grating stimulus diagrams; when the orientation identification of the tested person is incorrect, the grating contrast of the grating stimulus diagram is improved, the identification difficulty of the tested person is reduced, until the tested person is correctly identified, the grating stimulus diagram is output, and the grating perception capability corresponding to the grating stimulus diagram is obtained, so that the grating perception capability test of the tested person is completed.
Drawings
FIG. 1 is a schematic flow chart of a detection method for sensing capability of a sinusoidal grating based on contrast modulation according to the present invention;
FIG. 2 is a graph of grating stimulus for different grating contrasts in a grating stimulus function of the present invention;
FIG. 3 is a graph of the grating stimulus for a grating orientation of π/2 in the grating stimulus function of the present invention;
FIG. 4 is a graph of grating stimulus for a grating orientation of 0 in the grating stimulus function of the present invention;
FIG. 5 is a graph of the grating stimulus for a grating orientation of π/4 in the grating stimulus function of the present invention;
FIG. 6 is a graph of the grating stimulus for a grating orientation of 3 π/4 in the grating stimulus function of the present invention;
fig. 7 is a diagram illustrating a random carrier in the present invention.
Detailed Description
Referring to fig. 1, the method for detecting sensing capability of a sinusoidal grating based on contrast modulation provided by the invention comprises the following steps:
step S1, constructing a grating stimulation function based on the grating average brightness, the grating contrast, the grating spatial frequency, the random carrier, the carrier contrast, the grating orientation, and the grating phase, which specifically includes:
grating stimulus function:
l(x,y)=Lmean×{1+R(x,y)×cc×{C×sin2πf(y cosθ-x sinθ)+φ]h, wherein, LmeanIs the average brightness of the grating, C is the grating contrast, f is the grating spatial frequency, R (x, y) is the random carrier, CcCarrier contrast, theta for grating azimuth, and phi for grating phase.
Step S2, taking a value C in the range of grating contrast ratio value under the condition that the average grating brightness, the grating space frequency and the carrier contrast ratio are preset values, the grating phase is taken as a first value, the random carrier is taken as a second value and the grating direction is A or BxSubstituting the target grating stimulus image into a grating stimulus function to obtain a target grating stimulus image, wherein when A is 0, B is pi/2; when A is pi/4, B is 3 pi/4; the value range of the first value is 0 to 2 pi, and the first value takes any value from 0 to 2 pi when the step S2 is executed each time; the second value is a random number value each time step S2 is executed.
Referring to fig. 2, 3, 4, 5, 6, 7, in a specific embodiment LmeanThe actual measurement time can be (0.0-500.0 cd/m) for the average brightness of the grating2) And optionally adjusting. But the adjustment is performed before the measurementAfter the measurement is finished, the measurement can not be adjusted again in the whole measurement process, and after one measurement is finished, the measurement can be adjusted again before the next measurement is carried out; the grating spatial frequency f, i.e. how many periods there are within the spatial range of a one-degree view; phi is the phase of the grating, and the purpose of randomly changing phi is to increase the difficulty of identifying the direction of the grating of the measured object.
As shown in fig. 2, the grating contrast C gradually decreases from left to right, and the smaller C, the greater the difficulty level corresponding to the measurement; the larger C, the smaller the difficulty level corresponding to the measurement.
Referring to fig. 3 to 6, during the test, θ usually selects two values (e.g., 0 and pi/2, pi/4 and 3 pi/4), and θ included in the target raster stimulus pattern for each occurrence is randomly selected from the two values, so that the user needs to determine which value θ included in the target raster stimulus pattern is.
As shown in FIG. 7, R (x, y) is a carrier wave formed by random noise points, CcThe carrier contrast is from left to right, the carrier contrast of the random carrier of the first graph and the second graph is greater than that of the third graph and the fourth graph, and the difficulty of identifying the third graph and the fourth graph by the tested person is greater than that of the first graph and the second graph.
And step S3, displaying the target grating stimulus diagram to the testee, and receiving the predicted grating orientation input by the testee.
Step S4, when the predicted raster orientation inputted by the testee is the same as the raster orientation of the target raster stimulus diagram, let Cx=Cx× (1-R) executing step S2 until the predicted raster orientation inputted by the testee is different from the raster orientation of the target raster stimulus diagram, otherwise, let Cx=Cx× (1+ R), step S2 is executed until the predicted raster orientation inputted by the testee is the same as the raster orientation of the target raster stimulus diagram, and R is a ratio constant.
And step S5, outputting the grating contrast of the target grating stimulus image, wherein the grating contrast of the target grating stimulus image is the grating perception capability of the testee.
In a specific scheme, the grating contrast is displayed to a tested personIs CxWhen the predicted grating direction input by the testee is the same as the grating direction of the target grating stimulus diagram, the grating contrast of the grating stimulus diagram is reduced, the recognition difficulty of the testee is increased, and the grating stimulus diagram is output until the testee cannot recognize the target grating stimulus diagram; when the orientation identification of the testee is incorrect, the grating contrast of the grating stimulus diagram is improved, the identification difficulty of the testee is reduced, and the grating stimulus diagram is output until the testee identifies correctly, wherein R is a ratio constant and is used for controlling the test precision, and the smaller R is, the higher the test precision is.
And outputting the grating contrast of the target grating stimulus image, wherein the grating contrast of the target grating stimulus image is the grating perception capability of the tested person, thereby completing the grating perception capability test of the tested person.
In the embodiment, the grating stimulus diagrams with different grating contrasts and different directions are displayed to the testee, the testee identifies the grating directions in the grating stimulus diagrams, when the direction identification of the testee is correct, the grating contrast of the grating stimulus diagrams is reduced, the identification difficulty of the testee is increased, and the grating stimulus diagrams are output until the testee cannot identify the grating stimulus diagrams; when the orientation identification of the tested person is incorrect, the grating contrast of the grating stimulus diagram is improved, the identification difficulty of the tested person is reduced, until the tested person is correctly identified, the grating stimulus diagram is output, and the grating perception capability corresponding to the grating stimulus diagram is obtained, so that the grating perception capability test of the tested person is completed.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.