JP2016158812A - Font assessment method, apparatus, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an assessment method, apparatus, and program for calculating, for each type of fonts, a decimal visual acuity required to read characters, for example, with a size of 7.2 pt from a visual distance of 30 cm at a best reading speed.SOLUTION: The assessment method causes a computer to calculate, using the following expression D=A/(B×C), a decimal visual acuity required when a subject reads a prescribed font under a prescribed condition using a character size A obtained from a result of a readability assessment test of a prescribed font, a prescribed-condition visual angle B, and a minimum separable acuity C obtained by measuring the visual acuity of the subject by a visual acuity test.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a font evaluation method, apparatus, and program.

  Conventionally, a readability evaluation test for measuring a standard reading speed of a low vision patient or a sighted person, a character size suitable for reading, and the like has been proposed.

  Based on the character size obtained in the readability evaluation test, for example, a character size suitable for reading for a low vision patient can be obtained. The value of the character size gives the necessary magnification when the patient reads a newspaper or the like. Also, if the document is printed using characters of the same size suitable for reading, the patient can read the document without using a reading aid such as a loupe. As described above, based on the character size obtained in the readability evaluation test, it is possible to quantify a reading environment suitable for a low vision patient to read.

  For example, MNREAD-J and MNREAD-Jk are known as charts used in the readability evaluation test.

  FIG. 1 is a diagram showing an MNREAD-J chart.

  The text on the MNREAD-J chart is a sample that similarly requires visual information processing and eye movements that are required in everyday reading. The MNREAD-J chart is composed of 19 sentences with different contents. Each sentence is designed to have a character size of 1.3 to -0.5 LOGMAR (equivalent to about 0.05 to 3.16 in decimal visual acuity) when read from a standard measurement distance of 30 cm.

  Each sentence is composed of 30 characters without including punctuation marks, and is printed on 3 lines per line. The number of kanji per sentence is limited to 8 characters, and all kanji are selected from educational kanji. The word does not extend over two lines, and the content of the text is readable by any Japanese from junior high school students up to elementary school age.

  The MNREAD-Jk chart is different from the MNREAD-J chart in that each sentence is composed of 24 characters in which nine hiragana words are arranged at random with a space in between.

  In the readability evaluation test, each sentence of MNREAD-J or MNREAD-Jk is read out in order from the top of the chart to the bottom, and the subject is read from the standard measurement distance. The test results are plotted with the character size of each sentence as the horizontal axis and the reading speed of correctly read characters as the vertical axis.

  FIG. 2 is a diagram for explaining the results of the readability evaluation test.

  The critical character size (CPS), maximum reading speed (MRS) and reading visual acuity (RA) are obtained from the results of the readability evaluation test.

  The critical character size (CPS) is the smallest character size that the subject can read at his / her best reading speed. As shown in FIG. 2, the reading speed is usually constant when the character size is relatively large. When the character size is reduced, the character size immediately before the reading speed starts to drop suddenly is the critical character size.

  At character sizes greater than the critical character size, reading speed is almost constant and maximum. The average reading speed when the character size is larger than the critical character size is a representative value of the maximum reading speed (MRS). The maximum reading speed is a reading speed that can be achieved when the subject is not restricted by the character size, that is, when sufficient enlargement or contrast is obtained.

  Reading acuity (RA) is the smallest character size that the subject can somehow read. The reading speed is reduced for characters smaller than the critical character size, but the text can still be read. If the character size is further reduced, the entire sentence cannot be read and only a few characters can be read. This eyesight that can be read as much as possible is called reading eyesight.

  FIG. 3 is a diagram for explaining that the character size is represented by a viewing angle.

  The viewing angle is an angle when characters are projected onto the retina through the lens of the eyeball E.

  In the example illustrated in FIG. 3, the viewing angle θ when the character “large” is projected onto the retina of the eyeball E is illustrated.

  The viewing angle θ is an angle when the character is viewed from a predetermined distance, and a unit of radians, degrees, or minutes can be used.

  The viewing angle when a character having a size of 7.2 pt is viewed from a distance of 30 cm can be expressed by the equation shown in FIG. FIG. 3 shows a formula for obtaining the viewing angle in units of radians, degrees, and minutes.

JP 2012-247920 A

Koichi Oda, “MNREAD-J, Jk Chart Manual”, [online], May 18, 2002, [searched September 17, 2014], Internet <URL: http://www.cis.twcu.ac. jp / ~ k-oda / MNREAD-J / MNREAD-J-JkMan020518.pdf>

  In a conventional readability evaluation test, a standard reading speed of a low vision patient or a sighted person, and a character size suitable for reading can be measured.

  On the other hand, for example, the fractional visual acuity required when a character having a size of 7.2 pt can be read at the best reading speed from a viewing distance of 30 cm cannot be calculated for each type of font.

  This specification provides an evaluation method, apparatus, and program for calculating, for each font type, decimal visual acuity required when, for example, a character having a size of 7.2 pt can be read from a viewing distance of 30 cm at the best reading speed. The task is to do.

According to the method disclosed in the present specification, for a subject, a character size A obtained from the result of the readability evaluation test of a predetermined font, and a viewing angle B when a character of a predetermined size is viewed from a predetermined distance, Using the minimum separation threshold C obtained by measuring the visual acuity of the subject by visual acuity test, the decimal visual acuity D required when reading the predetermined font of the predetermined size from the predetermined distance is: Finding it using an equation
D = A / (B × C)
The computer runs.

In addition, according to the apparatus disclosed in the present specification, the character size A obtained from the result of the readability evaluation test of the predetermined font and the viewing angle B when the character of the predetermined size is viewed from a predetermined distance are given to the subject. And a minimum separation threshold C obtained by measuring the visual acuity of the subject by visual acuity test, and a decimal visual acuity D required when reading the predetermined font of the predetermined size from the predetermined distance. , The operation part to be calculated using the following equation:
D = A / (B × C)
Prepare.

Further, according to the program disclosed in the present specification, the character size A obtained from the result of the readability evaluation test of the predetermined font and the viewing angle B when the character of the predetermined size is viewed from the predetermined distance to the subject. And a minimum separation threshold C obtained by measuring the visual acuity of the subject by visual acuity test, and a decimal visual acuity D required when reading the predetermined font of the predetermined size from the predetermined distance. , Using the following formula,
D = A / (B × C)
Let the computer run.

  According to the above-described method disclosed in the present specification, for example, the fractional visual acuity required when reading a character having a size of 7.2 pt from a viewing distance of 30 cm at the best reading speed is calculated for each type of font. An evaluation method can be realized.

  Further, according to the apparatus disclosed in the present specification described above, for example, the decimal visual acuity required when reading a character having a size of 7.2 pt from the viewing distance of 30 cm at the best reading speed is calculated for each type of font. An evaluation method can be realized.

  Further, according to the program disclosed in the present specification described above, the fractional visual acuity required for reading, for example, a character having a size of 7.2 pt from the viewing distance of 30 cm at the best reading speed is calculated for each type of font. An evaluation method can be realized.

It is a figure which shows a MNREAD-J chart. It is a figure explaining the result of a readability evaluation test. It is a figure explaining expressing a character size with a viewing angle. 1 is a diagram illustrating one embodiment of an apparatus disclosed herein. It is a figure explaining the virtual body and real body of a character. Explaining how to calculate the fractional visual acuity D required to read a 7.2pt character from the viewing distance of 30cm at the best reading speed based on the critical character size obtained in the readability evaluation test for a given font It is a figure (the 1). Explaining how to calculate the fractional visual acuity D required to read a 7.2pt character from the viewing distance of 30cm at the best reading speed based on the critical character size obtained in the readability evaluation test for a given font It is a figure (the 2). It is a figure explaining calculating the fractional visual acuity D which can read a 7.2pt character as much as possible from the viewing distance of 30 cm based on the reading visual acuity obtained by the readability evaluation test of a predetermined font (the 1) . It is a figure explaining calculating the fractional visual acuity D which can read a 7.2pt character as much as possible from the viewing distance of 30 cm based on the reading visual acuity obtained by the readability evaluation test of a predetermined font (the 2) .

  Hereinafter, a preferred embodiment of an apparatus disclosed in the present specification will be described with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments, but extends to the invention described in the claims and equivalents thereof.

  FIG. 4 is a diagram illustrating an embodiment of an apparatus disclosed in the present specification.

  Based on the character size obtained from the readability evaluation test, the device 10 calculates the decimal visual acuity required when reading a character having a size of 7.2 pt, for example, from a viewing distance of 30 cm at the best reading speed. Calculate separately. As described above, the critical character size as the character size obtained from the readability evaluation test is known as a useful index that quantitatively represents the visual acuity of the subject.

  By using the apparatus 10, for example, it is possible to realize an evaluation method for calculating a fractional visual acuity required for viewing a character having a size of 7.2 pt from the viewing distance of 30 cm at the best reading speed for each type of font. This will be described below.

  Usually, in the visual acuity test, the minimum separation threshold of the subject is measured as visual acuity using a Landolt ring or a Snellen index. The fractional visual acuity is the reciprocal of the minimum separation threshold measured. The minimum separation threshold represents a difference in the visual acuity of the subject, and the smaller the minimum separation threshold, the higher the visual acuity of the subject.

  However, when a subject identifies different fonts, it is known that even if the character size is the same, there are fonts that are easy to read and fonts that are difficult to read due to different character shapes.

  Therefore, if a subject can easily compare a font that is easy to read, it is expected to be useful as an index when developing a font that is easy for many people to identify, such as a so-called universal font.

  For example, by using an easy-to-read font, the limited print area can be effectively used by making the minimum readable character size smaller than the character size of a hard-to-read font.

  Here, the terms of characters, fonts, and glyphs used in this specification will be described below. A character is a code for transmitting linguistic information, is composed of a combination of lines and points, and is used for charts such as a readability evaluation test and a visual acuity measurement. The characters include those printed on a print medium such as paper, as well as those displayed on a display device such as a liquid crystal display, as well as a photoset dial or digital font.

  The font means a collection of a plurality of characters in which the style, characteristics, tendency, and the like representing the characters are consistently formed. Within the same font, it means a set of characters with the same glyph shape and a consistent balance of line thicknesses. In addition, in computer typesetting or DTP that can enlarge, reduce, and transform a single character, It is meant to include a set of aligned characters. Often used as a synonym for typeface. In this specification, a typeface and a font are used without distinction.

  The letter shape means the design of “character”. Even if the design of the same character is different, if the line and point angles and the line thickness balance are different, the shape is different.

  The character size can be represented by, for example, points (pt: 1 pt = 1/72 inch).

  FIG. 5 is a diagram illustrating a virtual body and a real body of characters.

  As shown in FIG. 5, the predetermined character has a real body R that is a rectangular area inscribed in the character, and a virtual body V that is a rectangular area including the real body R and a margin surrounding the real body R. The sentence is formed by arranging virtual bodies V.

  The characters are designed so that one letter fits inside the real body. The real body is also called the face.

  For example, a font with a narrow line width such as Mincho type has a small actual body, and a font with a large line width such as Gothic type has a large actual body, so the margins surrounding the actual body R are different. May look different.

  If the actual body is square, the size of the actual body is represented by the length of one side. If the real body is rectangular, the dimensions of the real body are expressed based on the lengths of the short side and the long side.

  The description of the dimensions of the actual body also applies to the dimensions of the virtual body.

  The actual size ratio of characters is defined by the ratio of the dimensions of the real body and the virtual body.

  Hereinafter, the device 10 will be further described.

  The apparatus 10 includes a calculation unit 11, a storage unit 12, an input unit 13, a display unit 14, and a communication unit 16.

  The arithmetic unit 11 controls each element of the device 10 and performs various processes according to a predetermined program stored in the storage unit 12 in advance, and uses the storage unit 12 to temporarily store data generated during the processing. To do.

  The storage unit 12 may include a primary storage device and a secondary storage device. The storage unit 12 may include a drive that can read the storage medium 12a that stores a predetermined program.

  The input unit 13 is operated by a user or the like of the device 10 and inputs various types of information. For example, a keyboard, a mouse, a touch panel, or the like can be used as the input unit 13. The calculation unit 11 performs various processes using various types of information input from the input unit 13.

  The display unit 14 is controlled by the calculation unit 11 and displays various types of information. For example, a liquid crystal panel can be used as the display unit 14.

  The communication unit 16 is controlled by the calculation unit 11 to exchange data with the outside. The communication unit 16 can transmit and receive data via an external network. The device 10 can input information used for operation from the outside via the communication unit 16. Further, the device 10 calculates, via the communication unit 16, the result of calculating the fractional visual acuity required for reading a character having a size of 7.2pt from the viewing distance of 30cm at the best reading speed for each font type. Can be output to the outside.

  As the device 10, for example, a computer such as a microcomputer, a personal computer or a server, or a state machine such as a programmable logic controller can be used.

  Next, based on the character size obtained from the result of the readability evaluation test, for example, the decimal number required when the device 10 reads a character having a size of 7.2 pt from the viewing distance of 30 cm at the best reading speed. Processing for calculating visual acuity will be described below with reference to FIGS.

  First, based on the critical character size obtained from the result of the readability evaluation test, for example, the decimal visual acuity required when reading a character having a size of 7.2 pt from the viewing distance of 30 cm at the best reading speed is calculated. The process will be described below with reference to FIGS.

  The readability evaluation test was performed on a plurality of subjects using the MNREAD-J chart. As charts, three font charts of FS1, FS2, and FS3 were prepared. Each chart has the same sentence. Each sentence is a solid set, and there is no space between characters, that is, the characters are separated from the characters by the margin of the virtual body. Note that the number of subjects may be one. Moreover, you may perform a readability evaluation test using a MNREAD-Jk chart.

  Each subject read the text of each chart from a standard measurement distance of 30 cm, and a readability evaluation test was performed.

  The average minimum separation threshold representing the visual acuity of multiple subjects was 0.725, and the average decimal visual acuity was 1.38.

  An average value of critical character sizes obtained by performing a readability evaluation test using the charts of the fonts FS1, FS2, and FS3 is input to the apparatus 10 for each subject. Specific numerical values of the obtained critical character size are shown in FIG.

  In the device 10, in the process of calculating the fractional visual acuity required for viewing a character having a size of 7.2pt based on the critical character size of each font at the best reading speed from a viewing distance of 30cm, the size is The viewing angle is used when viewing a 7.2 pt character at a viewing distance of 30 cm.

  Here, the viewing angle when a character having a size of 7.2 pt is viewed at a viewing distance of 30 cm can be calculated as 29.106 minutes. Hereinafter, the viewing angle when the character of the predetermined size is viewed from a predetermined distance is referred to as a predetermined condition viewing angle. The predetermined condition viewing angle is input to the apparatus 10.

  In addition, the actual size ratio of the characters of each font FS1, FS2, and FS3 is input to the apparatus 10. Even for the same character, the actual size rate of kanji and the actual size rate of hiragana are different, and each actual size rate is input to the apparatus 10. Specific numerical values of the actual size ratio are shown in FIG. It should be noted that the font size data may be input to the apparatus 10 and the apparatus 10 may execute a predetermined program to obtain the actual character size ratio based on the font data.

  Next, the apparatus 10 obtains the character size of the actual body for each font FS1, FS2, and FS3. Specifically, the apparatus 10 obtains the product of a predetermined condition viewing angle (here 29.106) and the actual size as the character size of the actual body. Here, the 30 characters of each sentence of the MNREAD-J chart include 8 kanji characters and 22 hiragana characters, so the ratio of kanji and hiragana is added to the actual size ratio as a weight. For example, the actual size ratio of the font FS1 is calculated as 29.106 × (0.896 × 8 + 0.830 × 22) / 30.

  Next, the apparatus 10 obtains a spatial frequency for each font FS1, FS2, and FS3. Spatial frequency is the quotient of critical character size divided by the average minimum separation threshold of multiple subjects.

  Spatial frequency refers to the spatial resolution required to identify a character. When a subject can read even a small character, it means that the spatial frequency required to read the character is low. The smaller the spatial frequency, the easier it is to read the character.

  Next, the apparatus 10 calculates a virtual body MAR for each font FS1, FS2, and FS3. The virtual body MAR is a quotient obtained by dividing a predetermined viewing angle (here 29.106) by a spatial frequency.

  Next, the apparatus 10 calculates an actual body MAR for each font FS1, FS2, and FS3. The real body MAR is a quotient obtained by dividing the character size of the real body by the spatial frequency. The larger the real body MAR, the easier it is to identify the character.

  Next, the apparatus 10 calculates, for each font FS1, FS2, and FS3, a fractional visual acuity necessary for reading a character having a size of 7.2 pt from the viewing distance of 30 cm at the best reading speed. The fractional visual acuity required when reading a 7.2pt character from the viewing distance of 30cm at the best reading speed is calculated by the calculation based on the virtual body of the character and the calculation based on the actual body of the character. Is called.

  The calculation based on the virtual body of decimal visual acuity necessary for reading the characters of 7.2 pt from the viewing distance of 30 cm at the best reading speed is performed by obtaining the reciprocal of the virtual body MAR. The decimal visual acuity required when reading a 7.2 pt character from the viewing distance of 30 cm at the best reading speed is as follows. If the subject has a decimal visual acuity of at least this value, This means reading at the best reading speed when reading at a viewing distance of 30 cm.

  In other words, it can be determined that the smaller the calculated decimal visual acuity value is, the easier it is for the subject to read.

  Since the actually printed text is composed of a real body and characters having a virtual body including a margin surrounding the real body, the 7.2 pt character of the virtual body calculation is best at a viewing distance of 30 cm. The decimal visual acuity required when reading at a reading speed of 5 is an index reflecting the actual readability of the subject.

  In addition, the calculation based on the actual body of the fractional visual acuity necessary for reading the 7.2 pt character at the best reading speed at a viewing distance of 30 cm is performed by obtaining the reciprocal of the actual body MAR. In this case, the virtual body size of 7.2 pt can be converted into an actual body. For example, when comparing a font with a relatively large virtual body and a font with a relatively small virtual body, it is possible to evaluate the character itself excluding the difference in virtual body size. The calculation based on the actual body can be calculated by calculating the actual size ratio of the actual body of the predetermined condition viewing angle to calculate the character size (minute) of the actual body and replacing it with the predetermined condition viewing angle.

  Compared to the three fonts FS1, FS2 and FS3, the readability (small numerical value) is compared when the fractional visual acuity required for reading 7.2pt characters at the best reading speed at a viewing distance of 30cm is compared. Is the order of FS1, FS2, and FS3. Therefore, FS1 and FS2 have better readability than FS3.

  Compared to the two fonts FS1, FS2, and FS3, the fractional visual acuity required when reading the actual body-calculated 7.2pt character with the best reading speed at a viewing distance of 30cm is easier to read. (The numerical value is small) is the order of FS1, FS2, and FS3. FS1 and FS2 have better readability than FS3.

  In addition, when calculating the fractional visual acuity necessary for reading the 7.2 pt character described with reference to FIG. 6 at the best reading speed at a viewing distance of 30 cm, the calculated decimal visual acuity is shown in FIG. As shown, the critical character size obtained by conducting the readability evaluation test, a predetermined viewing angle, and the minimum separation threshold of the subject can be obtained.

  Here, the critical character size indicates the size of the character that makes it difficult for the subject to read the document at the maximum reading speed when the character size is smaller than this, and the predetermined condition viewing angle is the condition of the fractional visual acuity to be calculated (In this embodiment, the decimal visual acuity necessary for reading a 7.2 pt character at a viewing distance of 30 cm) is shown, and the reciprocal of the minimum separation threshold indicates the subject's decimal visual acuity.

  Therefore, the fractional visual acuity required when reading 7.2pt characters at the best reading speed at a viewing distance of 30cm is the fractional visual acuity of the subject and the maximum reading speed when the subject has a smaller character size. Is represented by the product of the character size that makes it difficult to read and the ratio of the viewing angle of the predetermined condition.

  The above is the description of the process of calculating the fractional visual acuity required when the device 10 reads the 7.2 pt character at the best reading speed at a viewing distance of 30 cm.

  Next, FIGS. 8 and 9 will be described.

  FIGS. 8 and 9 differ from FIGS. 6 and 7 in that instead of the critical character size, reading visual acuity (RA), which is the smallest character size from which the subject can read the text, is obtained from the readability evaluation test. It was. Therefore, it is possible to calculate the fractional visual acuity that is at least necessary to read the 7.2pt character at a viewing distance of 30 cm. The description of the calculation method is the same as that using the critical character size, and will be omitted.

  In the present invention, the above-described font evaluation method, apparatus, and program can be changed as appropriate without departing from the spirit of the present invention.

  In this specification, a method for calculating the fractional visual acuity necessary for reading a 7.2 pt character at the best reading speed at a viewing distance of 30 cm has been described. For example, a 5.0 pt character is converted to a 15 cm viewing distance. The fractional visual acuity required for reading at the best reading speed may be calculated. In this case, the calculated value of the predetermined condition viewing angle changes.

  For example, the present invention can also be applied to the results of readability evaluation tests using charts other than MNREAD-J and MNREAD-Jk.

  In the present invention, the character size obtained from the result of the readability evaluation test may not be the critical character size or the reading acuity. For example, the fractional visual acuity necessary for reading a character under a predetermined condition may be calculated based on the character size represented by the viewing angle at an arbitrary position on the horizontal axis in FIG.

  Further, in the present invention, the readability evaluation test includes a recognition threshold test in which evaluation is performed while changing the character size in units of one character.

  Furthermore, the device 10 may be a device that performs a readability evaluation test using a chart such as MNREAD-J and MNREAD-Jk. In this case, it is not necessary to input the critical character size or the reading visual acuity obtained from the result of the readability evaluation test again to the device 10.

DESCRIPTION OF SYMBOLS 10 Device 11 Calculation part 12 Storage part 13 Input part 14 Display part 15 Communication part R Real body V Virtual body E Eyeball

Claims (7)

Character size A obtained from the result of the readability evaluation test of a predetermined font for the subject,
Viewing angle B when a character of a predetermined size is viewed from a predetermined distance,
A minimum separation threshold C obtained by measuring the visual acuity of the subject by visual acuity test;
Using the following equation to determine the decimal visual acuity required when reading the predetermined font of the predetermined size from the predetermined distance:
D = A / (B × C)
The method that the computer performs. The predetermined font used in the readability evaluation test has a real body that is a rectangular area inscribed with characters, and a virtual body that is a rectangular area including a real body and a margin surrounding the real body,
The method according to claim 1, wherein the viewing angle B when the character of the predetermined size is viewed from a predetermined distance is a virtual body viewing angle or a real body viewing angle. The character size A is an average value of the character sizes obtained from the results of the readability evaluation test performed on a plurality of the subjects,
The method according to claim 1, wherein the minimum separation threshold C is an average value of minimum separation thresholds obtained by measuring visual acuity of the plurality of subjects by visual acuity test.   The method according to claim 1, wherein the readability evaluation test is performed using an MNREAD-J chart or an MNREAD-Jk chart.   The method of claim 4, wherein the character size A is a critical character size or reading acuity. Character size A obtained from the result of the readability evaluation test performed on the subject,
Viewing angle B when a character of a predetermined size is viewed from a predetermined distance,
A minimum separation threshold C obtained by measuring the visual acuity of the subject by visual acuity test;
Using the following equation to calculate the decimal visual acuity D required when the predetermined font of the predetermined size is read from the predetermined distance:
D = A / (B × C)
Equipment provided. Character size A obtained from the result of the readability evaluation test performed on the subject,
Viewing angle B when a character of a predetermined size is viewed from a predetermined distance,
A minimum separation threshold C obtained by measuring the visual acuity of the subject by visual acuity test;
Using the following equation to determine the decimal visual acuity D required when reading the predetermined font of the predetermined size from the predetermined distance:
D = A / (B × C)
A program to be executed by a computer.

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