JP2014165616A - Wearable display for low vision person - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wearable display capable of imaging and displaying a front visual field so that a low vision person may walk outdoor during night and such.SOLUTION: The wearable display has functions of imaging a user's outdoor front visual field, converting the image to easy-to-see contrast and brightness, and displaying. Particularly, it is preferable to make the wearable display to have functions of detecting a level difference of a ground surface in front of the user by an ultrasonic sensor and measuring a distance to an object in front of the user by using infra-red LED light, and to materialize both of the functions at a proper processing speed.

Description

  The present invention relates to a wearable display that enables a visually handicapped person to use outdoors at night or the like by displaying the front field of view in an easy-to-view manner.

Some low vision people (those who are not blind but have visual impairments that interfere with daily life) who are said to have more than 1 million people in Japan can easily see their vision due to improved image contrast and brightness. It is known that there is.
On the other hand, as a result of research on the life of low vision people in the research of the Hyogo Prefectural Welfare Community Development Research Institute, it was found that low vision people who normally walk with white canes concentrate on the tip of the cane. , Hard to notice obstacles about the height of the head. May collide. It was also found that there was a need to know the existence of moving objects such as bicycles and cars. In addition, at night (about 20lx), it was difficult to see people who were seen in the daytime, and it was difficult to walk at night.

Traditionally, devices for low vision people
・ Loupe ・ Magnifying reading device ・ Light-shielding glasses ・ Electronic glasses using Maxwell optics ・ Low-vision glasses for indoor use. An example of electronic glasses using Maxwell optical systems is described in Patent Document 1 below.

JP 2007-271743 A

  Conventional devices for low-vision persons, including those described in Patent Document 1, are mainly for indoor reading. That is, it can be used when the surrounding ambient light is relatively stable and the distance of the object to be viewed by the low vision person is constant, and cannot be used for walking at night.

  The present invention provides a wearable display that can capture and display a forward field of view so that a low vision person can walk outdoors at night.

The wearable display according to the invention is characterized in that it has a function of capturing an image of a user's front field of view outdoors and converting the image into a contrast and brightness that are easy for the user to view.
With such a wearable display, it is possible to adjust the contrast and brightness to display an image in the front view so that the user can easily see it even when used outdoors where ambient light is not stable. . Therefore, the wearable display of the invention can effectively assist walking even when a low vision person goes out at night or the like.

The wearable display of the invention has a function of detecting a step on the ground in front of the user by an ultrasonic sensor, and enables an object in front of the user by an optical system using infrared LED light, in order to enable a user to walk outdoors. It is preferable that these two functions can be realized at a processing speed that can follow the distance between the image and the object that fluctuates as the user walks.
The wearable display of the invention can be used outdoors by detecting the level difference with an ultrasonic sensor and warning the low vision person, and measuring the distance to the front obstacle with infrared LED light to inform the low vision person. It is possible to assist the low vision person walking more safely. In addition, if these functions can be realized at a processing speed that can follow the distance between the user and the image that fluctuates as the user walks, it is further advantageous in that the walking speed does not need to be particularly slow.

A camera for imaging the user's forward field of view is placed forward at a position close to the height of the user's eyes, and the camera and the display main body for displaying the above image can be attached to the head, It is also preferable that the image processing apparatus and the power source can be carried outside the head.
If the image processing apparatus and the power source can be carried by a person other than the head, the portion to be mounted on the head can be reduced in weight and the size can be reduced. As a result, the burden on the user during use can be reduced, and the appearance of the wearable display can also be improved.

The display main body may be provided with a lens for artificially enlarging the screen.
In order to be able to walk outdoors, a certain angle of view is required. According to the inventors' investigation (described later), a low vision person's walking is required to have an angle of view of a horizontal viewing angle of 31 degrees or more and a vertical viewing angle of 21 degrees or more. If the lens is attached to the display main body as described above, such a desirable angle of view can be realized in a lightweight and small display that is easy to use.

It is further preferable that the lens for enlarging the screen is a holographic optical element.
In the case of using a holographic optical element, the display can be further reduced in weight compared to the case of using a lens made of glass or the like.

In the wearable display of the invention, when the above camera has a high sensitivity with a low minimum subject illuminance so that the front field of view can be captured even at night when the surroundings are dark, and the above function for displaying the image has a high image contrast It is particularly advantageous if both the contrast enhancement processing effective for the image and the contrast enhancement processing effective when the image contrast is low are provided.
According to such a wearable display, even when the lighting environment is different at night or the like, image processing is automatically selected according to whether the object to be viewed is high contrast or low contrast, and presented to the user for easy viewing. Is possible.

By providing a line-of-sight detection function and a character recognition function, it is possible to detect the position of the target that the user is trying to see in the user's field of view. If the target is a character, the character recognition process is performed to A wearable display that can inform the user by voice is also very meaningful.
The line-of-sight detection function detects the position that the user is paying attention to in the user's field of view, and if there is a character at that position, the character recognition function can grasp the character, and if it can be notified by voice, the character is discriminated. This is because it is useful for those who have difficulty in low vision.

In the above case, it is particularly advantageous if a holographic optical element is used in the optical system for imaging the user's forward field of view.
This is because the front view can be imaged without the center of the camera view and the center of the user view being shifted. The camera does not block the user's field of view, and the position of the camera is not restricted by the arrangement of the half mirror.

  According to the wearable display of the invention, it is possible to display the image of the front view so that the user can easily see the outdoor view even when the ambient light is not stable. Therefore, even when a low vision person goes out at night, the walking can be effectively assisted.

It is a figure which shows the structural example of the wearable display by invention. It is a functional block diagram about the wearable display of FIG. It is a figure which shows an example of mounting | wearing about the wearable display comprised so that a signal processing part, a control part, etc. might be carried except a head. It is a figure which shows the investigation result which investigated the (gamma) value for making it an image easy for a low vision person to see. FIGS. 4 (a) and (b) are the results of color, (c) and (d) are black and white, and (e) and (f) are the results of black and white inversion. It is a figure which shows the trial example of the wearable display which uses an expansion lens in order to set it as a required angle of view. It is a schematic diagram which shows the optical system in the case of producing a holographic optical element as an expansion lens. It is the photograph which shows the sidewalk used for the experiment of the image processing regarding contrast. It is a photograph which shows the result of the image processing regarding contrast. FIG. 8A shows the original image, FIG. 8B shows the result of the contrast enhancement processing using linear transformation, and FIG. 8C shows the result of the histogram flattening processing. It is a figure which shows a test subject's evaluation about the result of the image processing regarding contrast. FIG. 9 (a) shows a case where the white line background is black, and FIG. 9 (b) shows a case where the white line background is beige. It is a functional block diagram about a wearable display provided with a gaze detection function and a character recognition function. It is a schematic diagram which shows the wearable display containing the imaging optical system for visual fields using a holographic optical element (HOE). The conceptual diagram of distance measurement of a front obstacle using infrared light is shown. It is a figure which shows the lighting / extinguishing drive circuit of LED. An example of imaging when the infrared LED is turned on / off is shown. FIG. 14 (a) is an image when the right LED is lit. (b) is an image when the right LED is turned off. (c) is an image when the left LED is lit. (d) is an image when the left LED is turned off. It is a figure which shows the detection process of the irradiation position of the infrared light in an image. FIG. 15 (a) is an image when the LED is lit. (b) is an image when the LED is turned off. (c) is a difference image between when the LED is turned on and when the LED is turned off. (d) An image obtained by binarizing the difference image. It is a graph which shows the relationship between the distance between the position where the left and right LED in an image was irradiated with respect to the distance of LED and a front obstruction. It is an experimental machine of a level difference detection device using an ultrasonic sensor. It is a figure which shows the concept of level | step difference detection.

A configuration example of the wearable display of the present invention is shown in FIG. 1, and its functional block diagram is shown in FIG.
An image of the field of vision in front of the low vision person is taken by an imaging optical system including a camera and a lens, and this image is processed by the image processing unit to generate a bright and high-contrast display image that is easy for the low vision person to see. Then, the generated image is displayed by a display optical system including a display display, a field angle enlargement lens, and the like. In addition, infrared LEDs (infrared light sources) are attached to both ends of the display, and the control unit controls the lighting and extinction of these LEDs and the imaging timing of the camera of the imaging optical system to capture images. . The distance to the front obstacle is measured by image processing that detects the irradiation position of the LED detected in the image. When the distance to the obstacle is less than the distance that is assumed to be dangerous, a low vision person is warned by an alarm device including a vibrator and a speaker.
Furthermore, the signal processing unit analyzes the output signal of the ultrasonic sensor toward the user's front ground and detects the level difference. Warning.
If this ultrasonic detector part is removed and the handy type is adopted, the directivity of the detection target can be provided, and the level difference detection accuracy is improved.

  As the low vision person walks, the field of view of the low vision person also changes. The above image processing, signal processing for distinguishing between steps and obstacles, and display processing are performed within 1/30 seconds to walk while receiving information on obstacles, relying on the video provided by the low vision person Is.

  In order to use this device when walking outdoors, a display display equipped with an imaging optical system such as a camera, infrared LED, and ultrasonic sensor can be attached to the head, and the signal processing unit, control unit, image processing unit The power source, the vibrator, and the speaker are desirably small and portable. FIG. 3 shows an example of wearing such a wearable display (including attached devices).

  In order to obtain the γ value, which is a parameter that affects the angle of view, contrast, and brightness of wearable displays for low vision users, the following surveys are conducted as specifications that allow low vision persons to walk at night. It was.

[Survey on images that low vision persons can recognize sidewalks in twilight hours (about 20 lx)]
In image processing, a γ value is known as a parameter that affects the contrast and brightness of an image. The γ value is a parameter for correcting the luminance value of the output image with respect to the input image. When the γ value is set to be larger than 1.0, the contrast is corrected together with the brightness. When the γ value is used as an index for image processing to generate an image that is easy for a low vision person to view, an image of a sidewalk in the twilight time zone is taken to examine the γ value that makes the image easy to see for the low vision person. Images with changed values (γ = 1.0, 1.5, 2.0, 2.5, 3.0, 4.0) were created and presented to 13 low visioners. The low vision person answered the image that the sidewalk was visible. In addition, depending on the low vision person, there are cases where it is easy to see not a color but a black and white binary image or a black and white inverted image, so the following six experiments were conducted.
B) Verification experiment of the presented image Target of image: Sidewalk during twilight time (sidewalk with curb, sidewalk with white line only)
・ Color 1 The image with the changed γ value of the image of the sidewalk with the curb is presented in 6 levels (γ = 1.0,
1.5, 2.0, 2.5, 3.0, 4.0), surveyed the image that low vision person could recognize the sidewalk (multiple answers).
・ Color 2 Change the γ value of the image of the sidewalk with only white lines and present the image in 6 levels (γ = 1.0,
1.5, 2.0, 2.5, 3.0, 4.0), surveyed the image that low vision person could recognize the sidewalk (multiple answers).
・ Monochrome 1 Color 1 image with γ = 1.0, 2.0, 4.0 converted to gray scale, 3 levels survey ・ Monochrome 2 Color 2 image with γ = 1.0, 2.0, 4.0 converted to gray scale, Investigation on 3 stages ・ Black and white inversion 1 Black and white 1 reverse image Investigation on 3 stages ・ Black and white inversion 2 Black and white 2 inversion image

The results of these surveys are shown in FIG. Figure 4 (a) is color 1, (b) is color 2, (c) is black and white 1, (d) is black and white 2, (e) is black and white inversion 1, and (f) is black and white inversion It is an experimental result of 2. NO1 to NO6 in Fig. 4 (a) and (b) are γ = 1.0, 1.5, 2.0, 2.5, 3.0,
Corresponds to the image changed to 4.0, NO1 to NO3 in Fig. 4 (c) (d) change the color image to γ = 1.0, 2.0, 4.0, convert it to grayscale, and monochrome processing It corresponds to the image that has been. NO1 to NO3 in Figs. 4 (e) and (f) correspond to images obtained by changing the color image to γ = 1.0, 2.0, 4.0, converting it to grayscale, performing black and white processing, and inverting it To do.
From these results, it was found that if the γ value is 2.5 or more for the color, the image is easy to see for the low vision person. Further, it is considered that a γ value of 4.0 or more is necessary for black and white images and black and white inverted images. As for the impression of the subject this time, there were many opinions that color is better than black and white.

B) Angle-of-view verification experiment For viewing angle verification, nine types of sight-blocking boxes with three horizontal widths (horizontal direction) (90mm, 125mm, 180mm) and three vertical widths (vertical direction) (15mm, 25mm, 40mm) Was used to investigate the smallest angle of view that answered "I am likely to walk". The results are shown in Table 1. Table 2 shows the viewing angle of the view blocking box.
From this result, it was found that the horizontal angle of 125 mm or more, the vertical width of 40 mm or more, that is, the vertical viewing angle of 21 degrees or more and the left and right viewing angle of 31 degrees or more are the angle of view necessary for a low vision person to walk. .
Therefore, it is desirable to use a display having such an angle of view as the display used in the apparatus of the present invention. However, a display with a large angle of view is heavier than a display with a small angle of view, and may be large as a device. As a method for solving this problem, it is desirable to use a small display and a magnifying lens that enlarges the display and presents it to the user. FIG. 5 is an example of a prototype when a magnifying lens is used.

  Furthermore, if a holographic optical element (HOE) produced by the optical system shown in FIG. 6 is used as this magnifying lens, the weight can be reduced as compared with a bulk optical element produced by conventional glass or the like. be able to. The HOE can be manufactured by recording interference fringes on the recording material using the reference light shown in FIG. 6 and the object light shown in FIG. When using the HOE produced in this way, if the HOE is irradiated with light similar to the reference light, the light is diffracted in the same direction as the object light, and the object light can be reproduced. By selecting the reference beam and the object beam, the HOE can be made as a magnifying lens. If a recording material is a photopolymer and a highly transmissive material is selected, a lens can be manufactured that is light and allows the front field of view to be seen through.

  As a result of a survey of low vision persons conducted by the Hyogo Prefectural Welfare Community Development Research Institute, it was found that the visibility is different depending on the color scheme of the object to be seen, that is, the color scheme of low contrast or high contrast. In any case, the image can be easily viewed by performing image processing that further enhances the contrast. However, in actual image processing, processing for enhancing a low-contrast color scheme is different from processing for enhancing a high-contrast color scheme. Therefore, in the present invention, as processing for emphasizing a high contrast color scheme, contrast enhancement processing performed by linearly converting the tone value of an image and histogram flattening processing as processing for emphasizing a low contrast color scheme are performed. It is desirable to incorporate.

[Contrast enhancement by linear transformation]
The calculation formula for the contrast enhancement processing is as follows.
Lout
= (Lin-Lave) x G + Loc (eq.1)
(0 ≤
Lout ≦ 255) (eq.2)
Lin: Brightness value of each pixel on the input screen Lave: Average value per screen of the input screen
Loc: Output median value (256/2 = 128 fixed) G: Emphasis magnification By this processing, the average luminance is calculated for each screen, and the value of the gradation value is increased by the magnification at the level according to the luminance. It is.
In the experiment for evaluating the wearable display of the present invention, the emphasis magnification was set to 200%, and this image processing was reflected on the image processing substrate, and the experiment was performed by displaying an image in real time.

[Histogram flattening]
When walking at night, it is conceivable that lighting for pedestrians changes due to lights such as street lights and store signs. In that case, even if the brightness is distributed at an extremely low value, the brightness distribution in the image is made uniform, and the histogram is made uniform so as to convert it into a video having a wide dynamic range. This histogram flattening is expressed by the following equation. Let p be the density value before conversion, and h (p) represents the appearance frequency at the density value p. Assuming that the total number of pixels is N, the density value p ′ after smoothing of the histogram is assumed that the range of p ′ is [0, 255].
It becomes.

  An evaluation experiment was conducted using the developed wearable display of the present invention. In the evaluation experiment, an experiment was conducted to examine the usefulness of the image processing of the wearable display of the present invention. The test subjects were 4 low-vision persons, the lighting environment was 2 types of 10 lx and 60 lx, and the objects to be viewed were 2 types imitating the sidewalk with black background, white line sidewalk, beige background, white line. . Figure 7 shows the sidewalk used in the experiment.

  Image processing includes contrast enhancement processing using linear transformation (hereinafter referred to as contrast enhancement processing), histogram flattening processing, a tone curve for performing intermediate contrast enhancement between the two, a plane for directly displaying a captured image, and image processing. None. An example of image processing is shown in FIG. FIG. 8 (a) is an original image (plane). The result of contrast enhancement processing using linear transformation is shown in FIG. 8 (b), and the result of histogram flattening processing is shown in FIG. Shown in c). A high-contrast color scheme arrow (left side) and a low-contrast color scheme arrow (right side) are imaged at the lower left of the original image. When contrast enhancement processing is performed on this, it can be seen from FIG. 8B that high contrast arrows are clear. On the other hand, in FIG. 8C, it can be seen that the low-contrast color arrows are easier to see than in the case of the original image and the contrast enhancement process by the histogram flattening process.

Each condition was presented to the sitting subject, and was evaluated in five stages: 5: very easy to see 4: easy to see 3: normal 2: hard to see 1: very hard to see. At that time, it was assumed that the standard plane was 3 :. The experimental results when the illuminance is 10 lx are shown in FIG.
The vertical bar in the figure represents the evaluation of each subject. When the background of the white line is black (Fig. 9 (a)), comparing the case where it is not applied and the case where it is not applied, the sidewalk which was not visible when it was not applied can be seen by attaching the wearable display of the present invention. I understand that. When image processing of a plane, contrast enhancement, histogram flattening, and tone curve is performed, a high-contrast sidewalk is an object, and thus the contrast enhancement effect is remarkable. Next, the tone curve is effective. On the other hand, when a white line background is beige and a low-contrast sidewalk is an object (FIG. 9B), it was found that the histogram flattening is more effective than the contrast enhancement processing.
From this result, it can be seen that the wearable display according to the present invention is desirably automatically selected and presented to the user according to whether the object to be viewed is high contrast or low contrast.

Many low-vision people can see simple figures, but it is difficult to distinguish complex shapes such as letters. Therefore, by installing the line-of-sight detection device on the above-mentioned display, it is possible to know the position that the user is paying attention in the user's field of view, and if there is a character at that position, the character recognition process can convey the character by voice, Furthermore, it becomes a useful display.
FIG. 11 shows a configuration example when the line-of-sight detection device is incorporated in this display. The eye of the low vision person who is looking at the display is imaged by the ophthalmic imaging optical system. Then, a black eye region is extracted from the image by binarization processing, and the center position of the black eye is detected by calculating the center of gravity of the region. The line of sight of the low vision person can be detected by referring to the correspondence map that associates the position of the black eye with the viewing direction in advance. Therefore, as shown in FIG. 10, the object of sight line is estimated by collating with the image of the visual field imaging optical system of this display. Is transmitted to the low-vision person through a speaker.

  If not only the magnifying lens but also the holographic optical element (HOE) is used in the field-of-view imaging optical system, the center of the camera's field of view and the center of the user's field of view can be imaged. . FIG. 11 shows a field-of-view imaging optical system using HOE. The light from the low vision person's field of view is diffracted by the transmissive HOE, and if this diffracted light is detected by a camera with a bandpass filter, the field of view from the position of the low vision person's eyes can be imaged. In general, if an image having the eye position as the center of the field of view is captured, the camera is placed at the eye position or a half mirror is used. When the camera is placed at the eye position, the camera blocks the user's view. If the half mirror is used, the field of view is transparent, but the position of the camera is restricted by the arrangement of the half mirror. On the other hand, when using the HOE, the field of view is also transparent, and the degree of freedom in designing the camera position is higher than when using a half mirror. In addition, when combined with a reflection-type holographic optical element, it can reduce the noise of background light, which is the light that goes straight to the camera, the light from an object in the real world, and the mixture with the light from the field of view. The user can see the display more easily. In addition, by using together with the above-described step detection function, not only the alarm device but also information emphasized on the display can be added.

Detection processing of front obstacles using infrared LEDs Ultrasonic sensors can be used to detect front obstacles, but obstacles depend on the material and shape of the front obstacle (people, walls, telephone poles, etc.). The distance measurement result to the object is different, and a stable result cannot be obtained. Therefore, in this apparatus, for obstacle detection ahead, distance measurement is performed using infrared light. A conceptual diagram of distance measurement using infrared light is shown in FIG. It is assumed that the infrared LED in the figure is provided at both ends of the glasses part of the wearable display of the present invention. The left and right LEDs are turned off and taken, and the distance to the obstacle is measured by performing the following image processing using these images. First, an image at the time of turning off is taken. Next, an image when the left LED is lit is taken. When the difference image of these images is calculated, only the portion where the infrared LED is lit as shown in the figure can be extracted. When the same processing is performed for the right LED and the difference between the lit positions in the left and right cases is obtained, the difference in position increases when the obstacle is close, and the difference in position decreases when the obstacle is far away. In the wearable display of the present invention, the distance to the obstacle is thereby measured, and if it is close, the user is warned. In the configuration in which the experiment was conducted, an acrylic lens was placed in front of an infrared light (wavelength 880 nm) LED, and the light from the LED was made parallel by this lens. The distance between these left and right LEDs is 11 cm that can be mounted on the eyeglass frame, and the light from the left and right LEDs irradiates almost the same position at a distance of 110 cm in front. In addition, a circuit (Fig. 13) that drives the left and right LEDs to turn on and off is fabricated, and these LEDs are repeatedly turned on for the right LED, right LED, left LED, and left LED in 40 ms. Images were taken with a central camera. FIG. 14 shows an example of an image captured under the condition that the distance to the front obstacle is 20 cm in a 20 lx environment.
In order to detect the position of the LED irradiated in the image, the following image processing was performed. An analysis example is shown in FIG. First, the difference between the image when the LED is turned on (FIG. 15 (a)) and the image when the LED is turned off (FIG. 15 (b)) is taken (FIG. 15 (c)). Then, this image is binarized by a fixed threshold value (FIG. 15 (d)). And the irradiation position of the infrared light in an image was calculated | required by detecting the gravity center position of this cut-out position. If such processing is performed on the images when the left and right LEDs are turned on and off, the distance between the centers of gravity of the areas irradiated with the left and right LEDs can be obtained, that is, the distance of the front obstacle is detected. be able to. FIG. 16 shows the result of an experiment for detecting the distance of the front obstacle in the environment of lighting 20 lx. In this experiment, the distance between the irradiated positions of the left and right LEDs in the image was obtained when the distance between the plate-shaped front obstacle and the infrared LED was changed to 12 cm, 52 cm, and 110 cm. As a result, it was found that when the distance to the front obstacle becomes smaller, the distance between the positions irradiated with the infrared LED in the image becomes larger and the distance to the obstacle can be detected. In general, in such a stereo measurement method, the detection accuracy is better as the distance between the LEDs is larger. This experimental result shows that an obstacle ahead of 12 cm to 110 cm can be detected even if the distance between LEDs, which is a distance corresponding to the width of the head or less, is 11 cm.

Step detection processing
FIG. 17 shows an example of an ultrasonic sensor for level difference detection that is assumed to be incorporated in the wearable display of the present invention. A cylindrical hood is attached to the tip of the ultrasonic sensor to remove noise caused by ultrasonic interference and improve detection accuracy. This unit senses the time from when the ultrasonic wave is emitted until the reflected wave returns, and detects the step by the process described below. A conceptual diagram of the step detection using this machine is shown in FIG. First, an average tave of n reflection times of the output of the ultrasonic sensor is taken. Then, an average t′ave of n ′ reflection times immediately after the n times is calculated. Then, if the difference between tave and t'ave is equal to or longer than a certain time, it is determined that there is a step. Based on this determination, an alarm output is issued to the alarm device mounted on this machine. The alarm device for the wearable display according to the present invention preferably includes a speaker and a vibration motor. When the wearable display of the present invention is used outdoors, it is considered that the frequency of step detection is high, and it is better to frequently use loudspeakers and not to cover the ears, which are sensory instruments for low vision persons to collect surrounding information. Therefore, it is desirable to output a warning for the step detection result by vibrating the vibration motor. Accordingly, the vibration motor is also used in the example of FIG.

Claims (8)

  A wearable display having a function of capturing an image of a user's front field of view outdoors and converting the image into a contrast and brightness that are easy for the user to view.   In order to enable the user to walk outdoors, it has a function to detect the step on the user's front ground using an ultrasonic sensor, and a function to measure the distance to an object in front of the user using an optical system that uses infrared LED light. The wearable display according to claim 1, wherein the two functions can be realized at a processing speed capable of following an image and a distance to an object that change as the user walks.   A camera for imaging the user's forward field of view is placed forward at a position close to the height of the user's eyes, and the camera and the display main body for displaying the above image can be attached to the head, The wearable display according to claim 2, wherein the image processing apparatus and the power source can be carried outside the head.   4. The wearable display according to claim 3, wherein a lens for enlarging the screen is attached to the display body.   The wearable display according to claim 4, wherein the lens is a holographic optical element.   The above-mentioned camera is a high-sensitivity sensor with low minimum subject illuminance so that it can capture the forward field of view even in the dark surroundings. Contrast enhancement processing effective when the image contrast is high as the above-mentioned function for displaying the image. And a contrast enhancement process effective when the contrast of the image is low. 6. The wearable display according to claim 3.   By providing a line-of-sight detection function and a character recognition function, it is possible to detect the position of the target that the user is trying to see in the user's field of view. If the target is a character, the character recognition process is performed to The wearable display according to claim 1, wherein the wearable display can notify the user by voice.   The wearable display according to claim 7, wherein a holographic optical element is used in an optical system for imaging a user's forward field of view.