495 results about "Blind persons" patented technology

The invention discloses a pair of blind person intelligent glasses based on binocular vision. The glasses comprise a glasses terminal and a cloud end. A data acquisition and transmission module, a voice interaction and feedback module and a power supply system are arranged in the glasses terminal, and the glasses terminal is used for acquiring and processing data and receiving and feeding back voice instructions; the cloud integrates a sensing module, a task planning module, an action module and a path planning and navigation module, the sensing module analyzes instructions and environment information, the task planning module extracts natural language intentions and generates task structures, the action module dynamically generates task templates to execute tasks, and the path planning and navigation module achieves fine-grained obstacle avoidance navigation. The environmental perception precision is improved through binocular vision and GPS fusion, the use threshold is reduced through natural language interaction, the complex task processing capacity of the system is improved through dynamic task decomposition, and the obstacle avoidance accuracy is improved through hierarchical path planning.

The invention discloses a blind person auxiliary interaction method and system based on a multi-modal large model and a storage medium, and belongs to the technical field of artificial intelligence, and the method comprises the steps: obtaining a user voice instruction and an external environment image, and carrying out the preprocessing of the obtained data; inputting the preprocessed data into a pre-trained multi-modal large model to obtain an environment understanding result; integrating the environment understanding result into feedback information for voice output, and adjusting output intonations according to environment characteristics; the acquisition method of the pre-trained multi-modal large model comprises the following steps: acquiring historical multi-modal data; and inputting the historical multi-modal data into a pre-constructed multi-modal large model, carrying out fine tuning on the trained multi-modal large model through a base layer in a frozen model to obtain a trained multi-modal large model, fusing multi-modal information through the multi-modal large model, accurately identifying a user intention and a corresponding object in a complex environment, and carrying out real-time identification on the user intention and the corresponding object in the complex environment. Therefore, accurate scene description is fed back.

The invention discloses a pull-type robot blind guiding system and method, and relates to the technical field of mobile service robots, the pull-type robot blind guiding system comprises a robot body, the robot body comprises an environment sensing and recognition module and a path planning module, the environment sensing and recognition module is used for obtaining three-dimensional point cloud information of the surrounding environment, and the path planning module is used for planning the three-dimensional point cloud information of the surrounding environment; generating an environment composite map according to the three-dimensional point cloud information; the path planning module analyzes the environment composite map by introducing artificial potential field factors, and generates a safe and collision-free initial path for the blind; the robot body is physically connected with the blind person through the rigid guide rod. Multi-sensor coupling is introduced, and artificial potential field factors are added, so that the obstacle avoidance capability of the blind guiding robot in a complex environment is improved, safe walking of the blind in indoor and outdoor scenes is ensured, and the life autonomy of the blind is remarkably improved.

The invention provides a blind person voice navigation auxiliary method with a built-in offline AI intelligent model, and relates to the technical field of computer processing, and the blind person voice navigation auxiliary method comprises the following steps: S01, collecting environment image data in real time through an infrared-visible light binocular camera, synchronously obtaining six-degree-of-freedom motion attitude data of an inertial measurement unit, the binocular infrared-visible light binocular camera comprises a thermal imaging sensing channel; s02, inputting the environment image data into a pre-trained multi-task neural network model, and generating a three-dimensional semantic map containing a blind sidewalk topological structure and a dynamic obstacle detection result; and S03, based on a deep reinforcement learning algorithm, carrying out space-time clustering analysis on the historical paths of the user, and constructing a personalized habit route database fused with human body turning inertia. The sensing precision, the path planning humanization, the positioning accuracy and the extreme weather adaptability of the navigation system in a complex environment are remarkably improved, and safe navigation of the blind is guaranteed.

The invention relates to a blind person travel assisting robot which comprises a hardware structure and a control module, and the control module comprises a navigation and positioning module, an AI intelligent control module and a remote monitoring module. The navigation and positioning module comprises map drawing, path planning and obstacle avoidance and fusion positioning, the AI intelligent control module comprises a sensor system, a voice interaction module, a tactile feedback module and an intelligent decision module, the hardware structure comprises a traction device and a mobile robot, and the traction device is provided with a touch feedback device. The touch feedback device comprises multiple sets of linear motors, obstacle information is coded through vibration of different frequencies, the mobile robot is of a circular structure, and a crawler belt is arranged at the bottom of the mobile robot. According to the auxiliary robot, through fusion of multiple positioning modes, the positioning precision and reliability are improved, it is ensured that the robot accurately knows the position of the blind person, and therefore the guiding service is better provided for the blind person.

The invention relates to the technical field of intelligent travel, in particular to a blind person positioning and yaw early warning device, system and method based on optical fiber vibration signals. Firstly, an optical fiber sensor network is laid in a hospital, vibration signals generated when the blind walk are obtained in real time, and step frequency, direction and vibration amplitude behavior data are obtained. Secondly, constructing a hospital space structure network, and determining an optimal path of the blind person from the current position to a target department through a path planning unit; and then positioning the position of the blind person in real time through a multi-sensor data fusion technology in combination with a blind person behavior data set and hospital space structure information. And finally, obtaining yaw information by calculating the yaw angle between the actual advancing path of the blind person and the standard path. And when the yaw angle exceeds a preset threshold value, the safety early warning unit sends out a correction prompt. Meanwhile, the device can dynamically adjust the path of the blind and give an early warning in advance according to temporary crowded areas or emergency situations occurring in hospitals, and walking safety is ensured.

The invention relates to the field related to application of visual obstacle avoidance, discloses an intelligent obstacle avoidance method and system based on machine vision, and establishes a technical scheme of cooperation of an electronic virtual blind sidewalk and an electronic tactile stick by adopting a machine vision scheme of synchronizing map positioning data through a cloud. According to the intelligent blind sidewalk system, the situations that the basic construction and maintenance of the blind sidewalk in daily life are insufficient and the occupation is serious can be effectively avoided, the problem that the blind person goes out difficultly is solved, the accurate going-out guiding and obstacle avoiding effects can be achieved through multi-party interaction linkage of real-time scene vision, cloud map data and the user blind stick equipment end, and high safety guarantee is provided for going out of the blind person.

The invention discloses an intelligent ring for a blind person, relates to the technical field of travel assistance for the blind person, and aims to solve the problem that an existing travel auxiliary tool for the blind person cannot provide comprehensive and timely travel assistance for the blind person, the intelligent ring comprises a wearing ring and a protection ring which are used for forming the ring, and is characterized in that a storage cavity is formed between the wearing ring and the protection ring; a 360-degree ultrasonic sensor array, a high-precision microprocessor, four groups of linear vibration feedback modules, a low-power-consumption Bluetooth 4.0 module and a rechargeable lithium battery are arranged in the accommodating cavity; the 360-degree ultrasonic sensor array comprises four sets of micro sensors which are located on the front side, the rear side, the left side and the right side of the containing cavity respectively, and the range of a single set of micro sensors is 120 degrees, so that all-directional coverage of the surrounding 360-degree space is achieved, and the blind can sense obstacles from all directions. The method has the advantage that the blind user can comprehensively and timely obtain the travel information.

The invention relates to a color temperature-based blind person color pattern emotion perception enhancement method and system, and the method comprises the steps: collecting a target image, and extracting the contour information and color information in the image; performing HSV judgment to obtain a cooling and heating classification result; mapping the cooling and heating classification result to a preset temperature interval, and generating a temperature control signal; according to the contour information, driving a target pin in the tactile array to protrude to form a tactile contour area; a temperature control signal is applied to the heating unit corresponding to the touch contour area, so that the temperature of the protruding pin is adjusted to be the target temperature corresponding to the cold and warm classification result. The method has the beneficial effects that the image color temperature is mapped into five grades of temperature gradients, so that a blind user can perceive a complete color emotion pedigree through touch, accurate touch expression of color emotion information is realized, and a visual color temperature-temperature sensing corresponding relation is established.

The invention discloses a road recognition early warning system and method for a blind guide stick, and belongs to the technical field of auxiliary travel of blind persons. Perturbation vibration signals generated when the blind guide stick makes contact with the ground are collected, and a perturbation vibration feature vector set is constructed; inputting the feature vectors into a multi-layer fusion feature analysis model, and extracting abnormal sensitive features such as low-amplitude periodic disturbance, heterogeneous feedback response and contact delay gradient change; constructing a perturbation anomaly risk map based on the features, and dividing risk levels; further extracting a high-risk area and identifying a dangerous point set; performing space fitting on the dangerous point and the blind guiding user path prediction trajectory, and judging whether a path crossing risk exists or not; if the intersection exists, multi-mode early warning including vibration, voice and directional prompt is triggered; according to the invention, accurate identification and dynamic early warning of small road abnormity can be realized, the blind guiding safety and environmental adaptability are improved, and the system has low power consumption and high real-time performance.

The embodiment of the invention provides a reading assisting device, method and equipment and a storage medium, the reading assisting device comprises a host and a shell, the host is detachably arranged on the shell, a scanning module is arranged on the host, and the host is further used for being connected with an earphone. When a user needs reading assistance, the user can take down the host from the shell of the reading assistance device and use the scanning module to scan newspapers or magazines, after the scanning module collects image information on the newspapers or magazines, the host recognizes characters in the image information, converts the recognized characters into voice data, and sends the voice data to the user. The voice data is played through the earphone, so that a user can acquire information on newspapers or magazines through voice. According to the embodiment of the invention, the external information acquisition mode of the blind can be expanded, so that the blind can know text information without relying on braille alphabets, and the technical problem that the external information acquisition mode of the blind is limited in the existing mode is solved.

The invention discloses an intelligent interaction system and an intelligent blind guiding walking stick, which have the function of sensing the road condition in front, and transmit the road condition information to a user by touching the rotating direction of a ball so as to help the user to avoid obstacles. In addition, when the user goes up and down stairs, the walking stick can remind the user of the current walking direction through the up-down movement of the touch ball, so that the walking safety and convenience of the blind are improved.

The invention discloses an active visual explanation system for blind person field travel, and belongs to the technical field of man-machine interaction. Based on the system, a user can selectively broadcast navigation obstacle avoidance or scenery description, real-time image information collected by a deep vision detection module is recognized through a deep neural network model, speed and type information of objects in front and below is obtained in combination with a positioning system, and when the user selects to broadcast navigation obstacle avoidance, the navigation obstacle avoidance or scenery description is broadcasted. After the audio instruction sequence corresponding to each sub-state is generated according to the shortest state sequence, the user acts under the guidance of the audio instruction, and each action can be fed back by the system, so that the correctness and efficiency of the traveling forward route operation are greatly improved; when the user selects to broadcast the beautiful scenery description, the AI model generates an audio instruction sequence according to the identified object information and informs the user of the audio instruction sequence; not only is the safety of the user during the on-site travel improved, but also the user can be helped to know the scenic spot in which the user participates, and the whole-process visual supervision is provided for the on-site travel of the user.

The invention relates to the technical field of intelligent walking assisting equipment, and discloses a blind person intelligent guiding walking assisting method and system based on deep learning. The intelligent guiding power-assisted walking method for the blind is applied to guiding power-assisted electronic equipment, and specifically comprises the following steps: S101, receiving a starting signal sent by a user terminal, starting a multi-source sensor array to collect environment data in parallel, executing a Kalman-Transform space-time alignment algorithm, establishing a multi-modal data space-time unified coordinate system, and establishing a multi-modal data space-time unified coordinate system; when gait phase changes are collected and detected, a multi-source sensor array is activated and dynamically triggered for high-precision scanning, and a threat evaluation model is generated to calculate an obstacle collision probability point cloud matrix; and S102, processing the obstacle collision probability point cloud matrix through Point VoxelNet to generate a three-dimensional environment skeleton. The cross-modal attention mechanism of the millimeter wave radar and the vision improves the rain and fog weather recognition accuracy, and in addition, the dynamic threat evaluation module is combined with the double-threshold early warning strategy, so that the collision false alarm rate is effectively reduced.

The invention relates to the technical field of speech synthesis, can be applied to business scenes of blind navigation, financial science and technology, medical health and the like, and discloses a navigation method based on environmental perception and path data, which comprises the following steps: acquiring environmental data through an environmental perception sensor, generating environmental perception data, and generating navigation path data in combination with a positioning module; a navigation instruction is generated through the voice synthesis module and is output through the voice broadcast module, a vibration feedback instruction is generated according to the environment sensing data and is output through the vibration module, a touch prompt instruction is generated according to the navigation path data and is output through the touch module, and real-time multi-mode feedback is provided. And the user can obtain accurate navigation information in a complex environment. According to the invention, voice, vibration and tactile feedback are generated by combining the environmental perception data and the navigation path data, and multi-modal navigation information is provided, so that the safety and navigation accuracy of a user in a complex environment are remarkably improved, and the collision risk and the probability of getting lost are reduced.

The invention discloses a tactile stick and a safe path navigation method thereof, electronic equipment and a storage medium, and is applied to the technical field of blind navigation. The method comprises the steps of planning a path according to a current position and a target position of a user, and generating an initial path; guiding a user to advance along the initial path; establishing a path width model, and obtaining a safe path width through the path width model; the position of the user is monitored in real time in the advancing process, and it is ensured that the user is within the safe path width range all the time. Through organic combination of the tactile stick and the visual camera, a cooperative working system is formed, and the position relation between a user and the safety path width is monitored in real time; through vibration feedback of different levels, the user is reminded to adjust the advancing direction in real time so as to ensure that the user always advances within the safe path width range of the path. And the safety and independence of visually impaired people are greatly improved.

The invention discloses a blind person navigation and positioning system and method, and relates to the technical field of intelligent assistance and positioning navigation, and the system comprises a positioning service unit and a navigation service unit. In the positioning service unit, an IMU module collects three-axis acceleration and three-axis angular velocity information of a user in real time and calculates motion data of the user; the GNSS module receives satellite signals in real time and calculates position data of a user; and the data processing module carries out positioning according to the data of the IMU module and the GNSS module, and sends the positioning result of the user to the navigation service unit. In the navigation service unit, a demand acquisition module is used for user interaction and acquiring terminal point information of a user; the path planning module generates an optimal path according to the starting point information and the terminal point information of the user; and the navigation guiding module guides the user to advance along the planned path through voice prompt. And more accurate navigation information is provided for the blind. According to the invention, real-time positioning and navigation services are provided for the blind, and the travel safety and convenience of the blind are enhanced.

The invention discloses a position guiding method, system and device for blind person travel and a medium, and relates to the technical field of blind person travel guiding. The method comprises the following steps: receiving current position information sent by a transmitting end, determining playing content based on the current position information, and playing according to the playing content; when a voice request of a blind person is received, identifying a target position in the voice request; a target route scheme is determined based on the current position information and the target position, the target route scheme comprises a plurality of sub-routes and mark points corresponding to the sub-routes, and the mark points comprise corresponding voice prompts; and playing a corresponding voice prompt according to the real-time position of the blind person sent by the transmitting end and the target route scheme. By implementing the technical scheme provided by the invention, accurate and timely position feedback can be provided for the blind, and the travel requirements of the blind in a complex urban environment are further met.

The invention discloses a blind guide stick local obstacle avoidance navigation method based on multi-sensor fusion, which comprises a telescopic blind guide stick, an RGB-D depth camera, a radar and other sensors and a high-performance processor, so as to realize accurate environmental perception and intelligent navigation functions and improve the travel safety and convenience of blind people and visually impaired people. The method comprises the following steps: acquiring depth information of a surrounding environment through an RGB-D depth camera, providing a three-dimensional perception capability of a scene, performing auxiliary correction on information acquired by the RGB-D depth camera through a plurality of sensors such as radar, transmitting the information acquired by the sensors to a high-performance processor, and performing SLAM (Simultaneous Localization and Map Construction) algorithm so as to obtain the three-dimensional perception capability of the scene. According to the method, information collected by multiple sensors is fused, the pose information of the current blind guiding stick is calculated, nonlinear optimization is carried out according to the calculated pose information and measured depth information, the result of nonlinear optimization is used for establishing an octree map of the environment, and a reasonable obstacle avoidance path is generated according to the octree map. And the obstacle avoidance path is fed back to the blind and visually impaired people in real time in a voice or vibration mode.

The invention discloses a wearable intelligent obstacle avoidance system, and belongs to the technical field of blind person auxiliary travel. The invention aims to solve the problem that the existing blind person travel auxiliary equipment is inconvenient to use or high in cost. The method includes the steps that an image collection module collects blind sidewalk obstacle images; the GPS positioning module obtains position coordinates of a user; the lightweight target detection model performs obstacle recognition on the blind sidewalk obstacle image based on the position coordinates of the user to obtain obstacle information; the monocular distance measurement module obtains a distance signal between the current position of the user and the obstacle according to the obstacle information; the control module sends the current distance signal to the prompt module and sends a danger prompt signal when the distance between the current position of the user and the obstacle is smaller than a set threshold value; the prompting module sends a distance signal to a user; an alarm is sent to a user according to the danger prompt signal; all the modules are integrated on the wearable article to form the wearable device. The method is used for assisting the blind in going out.

The invention discloses a method for improving blind person obstacle avoidance efficiency and safety based on a multi-mode large language model, and the method comprises the following steps: 1, obtaining environment data, including object position, distance and shape information, through a plurality of sensors, and carrying out environment perception and data collection; step 2, preprocessing the data acquired by the sensors, including data cleaning and feature extraction, and then fusing the data of different sensors by using a multi-modal big language model; 3, based on the fused environment understanding model, using a large language model to generate language description adaptive to perception of the blind; and 4, transmitting the language description to the blind user in a voice prompt or tactile feedback mode. According to the method for improving the obstacle avoidance efficiency and safety of the blind person based on the multi-mode large language model, the large language model is adopted to generate language description adaptive to perception of the blind person, and the blind person can better receive navigation information.

An intelligent blind guiding stick relates to the technical field of blind guiding sticks. The problem that the blind cannot travel autonomously is solved. A multifunctional system is integrated on the blind guiding stick, a traction assembly is arranged at the bottom of the blind guiding stick, and the multifunctional system comprises an information acquisition assembly, a data processing module and a positioning module. The information acquisition assembly comprises a voice interaction module and an image acquisition module; a map is embedded in the data processing module, target position coordinates are determined according to the information collected by the voice interaction module, different travel routes are formulated according to the current position coordinates of the blind guiding stick and sent to the voice interaction module for broadcasting, and the traction assembly is driven according to the travel routes to drive the blind guiding stick to move; traffic light recognition and license plate recognition are further embedded in the data processing module and used for recognizing traffic light information and license plate information in the image information, so that the traction assembly is driven to drive the blind guiding stick to move forwards or stop, autonomous travel is achieved, and the intelligent blind guiding stick is suitable for autonomous travel of low-vision blind persons.

The invention discloses a blind person intelligent navigation system based on multi-modal sensor fusion, and relates to the field of blind person intelligent navigation systems, and the blind person intelligent navigation system comprises an initialization module, a data acquisition module, a data processing module, a first judgment module, a second judgment module, a path correction module and a navigation prompt module. The initialization module generates an initial path according to the initial position and the target position and starts a path guiding mode; the data acquisition module synchronously acquires image, radar and inertial measurement data; the data processing module calculates an image coherence index and generates an auxiliary judgment mark; the first judgment module determines whether to switch an obstacle avoidance mode or not according to the index continuity and the auxiliary mark; a second judgment module evaluates a condition of return path guidance in an obstacle avoidance mode; the path correction module judges a path correction mode through the spatial relationship and the deviation coefficient; the navigation prompting module outputs guiding information according to the mode; according to the invention, the accuracy and stability of navigation mode switching can be improved.

The invention provides an environment identification method and system for assisting a blind person in going out, and relates to the technical field of environment identification, an environment monitoring image and object information are acquired, and the object information comprises a target position and a current position of an object; determining a local action track of the object through the environment monitoring image and the object information; the object moves according to the local action track; acquiring an obstacle on the local action track from the environment monitoring image; acquiring information of obstacles in real time to obtain obstacle information; determining a risk value of the obstacle relative to the object through the object information and the obstacle information; and when the risk value is equal to or greater than a preset risk threshold value, generating a risk avoiding strategy executed by the object. And measures are taken in advance before the danger occurs, so that the blind person is helped to actively avoid the obstacle instead of passively dealing with the danger after the danger occurs, and the probability of accidents in the traveling process of the blind person is reduced.

The invention discloses a direction identification method and system of blind person intelligent glasses in an outdoor environment, and relates to the technical field of direction positioning of the blind person intelligent glasses. And according to the current position of the blind person intelligent glasses and the current position of each feature of the stereo model, determining the primary direction of the blind person intelligent glasses in the outdoor environment, and carrying out primary direction identification in the stereo model. Therefore, a direction deviation value is determined according to the ultrasonic positioning information, the front side image and the characteristics recorded by the three-dimensional model in the primary direction; according to the direction deviation value, the primary direction and the moving direction of the blind intelligent glasses, the final direction of the blind intelligent glasses in the outdoor environment is determined, dynamic movement of the blind intelligent glasses is fully considered, and the accuracy of the final direction of the blind intelligent glasses in the outdoor environment is further guaranteed; and multi-stage identification from the primary direction to the final direction is realized.

A system and a method are disclosed for giving wayfinding signals to a Person with Reduced Mobility (PRM) toward a desired location, wherein the PRM is in a certain area and wherein the wayfinding signals are adapted to a disability of the PRM. Guiding the PRM can be implemented by wayfinding signal that can be delivered via a mobile device (MD) of the PRM or via one or more speakers or buzzers that are associated with the certain area. The certain area can be a mall, a train station, a vehicle, etc. When the PRM is a blind person, then the wayfinding signals can be audible signals that lead the user from a current location toward a desired location.

The invention discloses a pair of blind glasses based on an AI language vision large model, and the glasses comprise a glasses body which is used for being worn on the head of an external person; the image acquisition camera is mounted in the glasses body and is used for acquiring image data of obstacles in the external environment in real time; the processing module communicates with the image acquisition camera and is used for analyzing the acquired image data and generating detailed environmental understanding; and the natural language processing and intelligent feedback system communicates with the processing module and is used for receiving the detailed environmental understanding output by the processing module and generating voice output from the environmental understanding through voice synthesis. According to the glasses for the blind based on the AI language visual large model, voice is finally output by adopting a natural language processing and intelligent feedback system, and voice output in a complex environment can be realized.

The invention discloses an intelligent blind person walking stick based on artificial intelligence, and relates to the field of intelligent walking sticks, and the intelligent blind person walking stick comprises a sensing module used for collecting environmental physical information in the advancing direction of a user in real time, and a processing module used for receiving multi-source environmental information collected by the sensing module, establishing a dynamic three-dimensional space model of the current local environment by taking a landing point at the bottom end of the walking stick as a current origin of coordinates; when the user touches the walking stick to the ground once, a'drop point event 'is triggered once, the three-dimensional space model is updated based on new drop point data, and the space offset between the current drop point and the previous drop point is calculated, including the moving distance and the direction change; compared with a scheme only based on distance perception or fixed path navigation, the method has higher environment understanding capability, navigation adaptive capability and real-time correction capability.

The utility model discloses a safe intelligent door lock alarm system which comprises an intelligent coded lock, a human body sensing device and a timing alarm device. The door lock is provided with a body sensing device, and the distance between houses senses people outside the door; when the person outside the door stays for more than the specified time, the timing alarm device gives an alarm; and the information is transmitted to a mobile phone end APP through Wi-Fi or Bluetooth. And when confirming that the environment is dangerous, the resident sends help seeking information to the community security personnel. Aiming at a timing alarm device, the utility model provides a solution for preventing mistaken touch and resident disturbing, and a time limiting function is added to the timing alarm device through a timer. The intelligent door lock alarm system provided by the utility model is optimized by aiming at the problem that a traditional camera system door lock has a view blind area for the safety of vast residents, especially vulnerable groups such as solitary people, deaf-mutes, blind people and the like indoors or when the residents are not at home, and can improve the safety index of the solitary or vulnerable groups.

The invention discloses a hospital internal positioning, navigation and obstacle avoidance system for assisting a blind person in seeing a doctor, which adopts a visual SLAM (Simultaneous Localization and Mapping) algorithm, a multi-view stereo matching algorithm and a global optimization algorithm Bundle AdJustent to reconstruct a three-dimensional map in a hospital, and adopts a PnP algorithm and an RANSAC (Random Sample Consensus) algorithm to obtain three-dimensional coordinates of equipment. A large language model GPT-4o is adopted to analyze the dialogue between the blind person and medical staff to obtain the destination of the blind person, a navigation algorithm A * is combined with a three-dimensional map, built in advance, of a hospital where the device is located in a cloud server, a navigation path is formulated and played to the blind person in real time, action guidance is provided for the blind person, and the blind person can conveniently and rapidly enter the medical staff. And detecting and segmenting a front obstacle by adopting an instance segmentation algorithm YOLOv8-seg, obtaining information of the front obstacle in combination with the depth image and coordinate transformation, and broadcasting the position of the obstacle to the blind.