Electronic glasses and method for adjusting focal point distance

Abstract

To suppress inconvenience caused by mis-alignment of a focal point distance.SOLUTION: An electronic glass includes: a direct-current power source; a variable focal point lens operated by power from the direct-current power source; and a control unit for controlling the focal point distance of the variable focal point lens. The control unit changes the focal point distance to a preset predetermined distance and maintains the predetermined distance in a case where the output voltage of the direct-current power source becomes lower than a predetermined value.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to electronic glasses and a focal length adjustment method. [Background technology]

[0002] Patent Document 1 describes electronic eyeglasses having a DC power supply. When the output voltage of the DC power supply decreases, it may become impossible to adjust the focal length of a variable-focus lens. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 168570 Summary of the Invention [Means for solving the problem]

[0004] According to a first aspect of the present disclosure, there is provided electronic glasses comprising a DC power supply, a variable-focus lens operated by power from the DC power supply, and a control unit that controls a focal length of the variable-focus lens, wherein when an output voltage of the DC power supply falls below a predetermined value, the control unit changes the focal length to a predetermined distance that has been set in advance and maintains the focal length at the predetermined distance.

[0005] According to a second aspect of the present disclosure, there is provided a focal length adjustment method for electronic glasses including a DC power supply and a variable focus lens operated by power from the DC power supply, the focal length adjustment method including determining whether an output voltage of the DC power supply has fallen below a predetermined value, and if the output voltage has fallen below the predetermined value, changing a focal length of the variable focus lens to a predetermined distance, and maintaining the focal length at the predetermined distance.

[0006] The above summary of the invention does not list all of the necessary features of the present invention. Also, subcombinations of these features may also be inventions. [Brief description of the drawings]

[0007] [Figure 1] 1 is a perspective view of electronic glasses according to a first embodiment. [Diagram 2] 1 is a block diagram of a main configuration of electronic glasses according to a first embodiment. [Diagram 3] 1 is a schematic configuration diagram of a DC power supply according to a first embodiment. [Figure 4] 2 is a configuration diagram of each functional unit in a control unit according to the first embodiment. FIG. [Diagram 5] FIG. 2 is a flowchart of a focal length adjustment method according to the first embodiment. [Figure 6] FIG. 11 is a block diagram of a main configuration of electronic glasses according to a second embodiment. [Figure 7] FIG. 11 is a schematic configuration diagram of a DC power supply according to a second embodiment. [Figure 8] FIG. 11 is a configuration diagram of each functional unit in a control unit according to a second embodiment. [Figure 9] FIG. 11 is a flowchart of a focal length adjustment method according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The present invention will be described below through the embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0009] In the following description, the terms front, back, top, bottom, right, and left refer to the front, back, top, bottom, right, and left directions as seen by a wearer wearing electronic eyeglasses 1. The front-to-back direction is the direction in front of the wearer. The left-to-right direction is the direction perpendicular to the front-to-back direction and the vertical direction.

[0010] (First embodiment) Fig. 1 is a perspective view of electronic glasses 1 according to the first embodiment. Fig. 2 is a block diagram of the main configuration of the electronic glasses according to the first embodiment.

[0011] The electronic glasses 1 are, for example, electronic glasses for vision correction. The electronic glasses 1 may be worn on both ears, or on the head or only one ear. The electronic glasses 1 may be for one eye, not for both eyes. In the following, a case where the electronic glasses 1 are for both eyes will be described as an example.

[0012] The electronic glasses 1 include a glasses frame 11 , a pair of variable focus lenses 12 , a DC power source 13 , an operation unit 14 , and a control unit 16 .

[0013] The eyeglass frame 11 includes a front 20, a pair of temples 21, and a pair of end pieces 22.

[0014] The front 20 holds a pair of left and right variable focus lenses 12. The front 20 includes a pair of rims 311 and a bridge 312. The rim 311 holds the variable focus lens 12. The rim 311 is formed, for example, in an annular shape, and the variable focus lens 12 is fitted into the inner circumference of the annular shape. Note that the rim 311 is not limited to an annular shape as long as it has a shape capable of holding the variable focus lens 12. The variable focus lens 12 may be held by a member other than the rim 311. In this case, the eyeglass frame 11 does not need to include the rim 311. The bridge 312 connects the pair of rims 311.

[0015] The temples 21 are connected to the left and right ends of the front 20, respectively. Two temples 21 form a left-right pair and are connected to the front 20. The temples 21 are members extending in the front-rear direction. Each temple 21 is connected to the front 20 via, for example, a hinge (not shown). This allows the temples 21 to rotate with respect to the front 20.

[0016] The end pieces 22 are provided at the rear end of each temple 21 and are hung on the wearer's ears. The two end pieces 22 are a pair on the left and right, and are formed, for example, as ear hooks that are curved downward to engage with the wearer's ears. The end pieces 22 may be formed integrally with the temples 21 or may be formed separately. When the electronic glasses 1 are worn, the pair of left and right temples 21 hold the sides of the wearer's head, and the end pieces 22 are hung on the wearer's ears, thereby supporting the eyeglass frame 11.

[0017] The variable-focus lens 12 is a lens whose focal length can be changed electrically or mechanically. As an example of this embodiment, the variable-focus lens 12 is a lens whose focal length can be changed electrically, and the focal length is changed by changing the voltage applied to it (hereinafter referred to as the "applied voltage"). The variable-focus lens 12 has a dielectric material such as liquid crystal within the lens. The electronic glasses 1 change the dielectric constant by applying a voltage to this dielectric material, thereby controlling the refractive index.

[0018] As an example, the variable-focus lens 12 is a so-called liquid crystal lens having a liquid crystal layer whose refractive index varies depending on the direction (orientation state) through which light passes. Transparent electrodes for applying voltage are provided on both ends of the liquid crystal layer of the liquid crystal lens. Note that one liquid crystal layer acts only on polarized light in one direction. Therefore, in order to act on polarized light in various directions, the variable-focus lens 12 may have two liquid crystal layers arranged so that the orientation directions of the liquid crystal molecules are perpendicular to each other.

[0019] However, the variable-focus lens 12 is not limited to a liquid crystal lens, and may be, for example, a liquid lens. A liquid lens is a lens that uses the interface between two types of liquid that have different refractive indices and do not mix as a refractive surface (lens surface). In a liquid lens, the shape of the interface is changed by controlling the wettability of the liquid by applying a voltage, for example, and the focal length is changed by changing the shape of the interface.

[0020] The DC power supply 13 supplies power to the pair of variable-focus lenses 12 and the control unit 16. The DC power supply 13 is provided, for example, inside one or both of the pair of end pieces 22 as shown in Fig. 1. The DC power supply 13 itself may have a shape that functions as the end piece 22. In this case, the DC power supply 13 may be detachable from the rear end of one or both of the pair of temples 21.

[0021] 3 is a schematic configuration diagram of the DC power supply 13 according to the first embodiment. As shown in FIG. 3, the DC power supply 13 includes a main power supply 25, a standby power supply 26, and a switching unit 27.

[0022] The main power source 25 has a first battery. The first battery is, for example, a primary battery or a secondary battery. The main power source 25 supplies power stored in the first battery to the pair of variable-focus lenses 12 and the control unit 16. If the first battery is a primary battery, the first battery is replaceable. If the first battery is a secondary battery, the DC power source 13 has a charging connector 13C to which an external power source (for example, a DC power source) can be connected by wire to charge the first battery, as exemplified in FIG. 1.

[0023] The standby power supply 26 can supply power to the pair of variable-focus lenses 12 and the control unit 16 in place of the main power supply 25. The standby power supply 26 has a second battery. The second battery has, for example, a primary battery or a secondary battery. The standby power supply 26 can supply power stored in the second battery to the pair of variable-focus lenses 12 and the control unit 16. If the second battery has a primary battery, the second battery is replaceable. If the second battery is a secondary battery, the second battery can be charged by connecting an external power source (for example, a DC power source) by wire to the charging connector 13C.

[0024] The first battery and the second battery in the DC power source 13 may be charged by non-contact power supply. In this case, the non-contact power supply method may be any of the following: electromagnetic induction method, magnetic field (electric field) resonance method, electric field coupling method, and electromagnetic wave method.

[0025] The main power supply 25 may include one or more DCDC converters that step down or step up the output voltage of the first battery. Similarly, the backup power supply 26 may include one or more DCDC converters that step down or step up the output voltage of the second battery. The DCDC converter of the main power supply 25 and the DCDC converter of the backup power supply 26 may be shared by one DCDC converter.

[0026] The switching unit 27 can switch between a state in which power from the main power supply 25 is supplied to the pair of left and right variable focus lenses 12 and the control unit 16 (hereinafter referred to as the "normal state") and a state in which power from the backup power supply 26 is supplied to the pair of left and right variable focus lenses 12 and the control unit 16 (hereinafter referred to as the "backup power state"). In the normal state, power from the backup power supply 26 is not supplied to the pair of left and right variable focus lenses 12 and the control unit 16. In the backup power state, it is sufficient that at least the power from the backup power supply 26 is supplied to the pair of left and right variable focus lenses 12 and the control unit 16, and power from the main power supply 25 may be further supplied, or power from the main power supply 25 may not be supplied at all.

[0027] For example, the electronic glasses 1 have a power path 100 for supplying power to a pair of left and right variable-focus lenses 12 and a control unit 16. In a normal state, the switching unit 27 controls the electrical connection between the power path 100 and the output terminal of the main power source 25 to ON, and controls the electrical connection between the power path 100 and the output terminal of the backup power source 26 to OFF. On the other hand, for example, as a backup power state, the switching unit 27 controls the electrical connection between the power path 100 and the output terminal of the main power source 25 to OFF, and controls the electrical connection between the power path 100 and the output terminal of the backup power source 26 to ON. Note that, for example, as a backup power state, the switching unit 27 may control the electrical connection between the power path 100 and the output terminal of the backup power source 26 to ON while keeping the electrical connection between the power path 100 and the output terminal of the main power source 25 ON.

[0028] The switching unit 27 may have, for example, an electrical switch (including a contactless relay) such as a transistor, or a mechanical switch such as a contact relay. The electrical switch is, for example, a field effect transistor (FET) or an insulated gate bipolar transistor (IGBT).

[0029] The switching between the normal state and the standby power state in the switching unit 27 may be performed by the control unit 16 or by the switching unit 27 itself.

[0030] The operation unit 14 is operable by a person and accepts operations by the person. The operation unit 14 accepts, for example, an ON operation for turning on the power of the electronic glasses 1 and an OFF operation for turning off the power of the electronic glasses 1. When the operation unit 14 accepts an ON operation, it transmits an ON signal indicating that the ON operation has been performed to the control unit 16. When the operation unit 14 accepts an OFF operation, it transmits an OFF signal indicating that the OFF operation has been performed to the control unit 16. The operation unit 14 is provided, for example, on one of the pair of temples 21, and is arranged so that at least a portion of the operation is exposed to the outside of the temple. The portion includes a portion that is touched by a person.

[0031] The operation unit 14 may use a touch sensor or a mechanical switch such as a push button. The on operation and the off operation are, for example, a touch operation on the operation unit 14 or an operation of pressing a push button (hereinafter referred to as a "press operation"). Note that the on operation and the off operation may be, for example, the same operation. In this case, the operation of the operation unit 14 when the power is off is considered to be an on operation, and the operation of the operation unit 14 when the power is on is considered to be an off operation. When distinguishing between the on operation and the off operation, for example, the number of touch operations or press operations and the operation time (the time of touching or pressing) are different between the on operation and the off operation.

[0032] The control unit 16 is provided, for example, inside one or both of the pair of temples 21. The control unit 16 has, for example, a storage unit 30 and a control unit 31.

[0033] The storage unit 30 stores various information. The storage unit 30 may include, for example, a non-volatile or volatile semiconductor memory (for example, a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), or an EEPROM (Electrically Erasable Programmable Read Only Memory)).

[0034] The control unit 31 is, for example, a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). Fig. 4 is a configuration diagram of each functional unit in the control unit 31 according to the first embodiment. As shown in Fig. 4, the control unit 31 includes a determination unit 50, a focal length control unit 51, and an output unit 52. The determination unit 50, the focal length control unit 51, and the output unit 52 are realized by executing a program stored in the storage unit 43.

[0035] The program may be provided by a computer-readable storage medium. The program is read from the computer-readable storage medium, installed in the storage unit 43, and executed by the control unit 31. The program may be downloaded from an external device via a communication network.

[0036] Examples of computer-readable storage media may include electronic storage media, magnetic storage media, optical storage media, electromagnetic storage media, semiconductor storage media, etc. More specific examples of computer-readable storage media may include diskettes, hard disks, random access memories (RAM), read-only memories (ROM), erasable programmable read-only memories (EPROMs or flash memories), electrically erasable programmable read-only memories (EEPROMs), static random access memories (SRAMs), compact disk read-only memories (CD-ROMs), digital versatile disks (DVDs), Blu-ray (RTM) disks, memory sticks, integrated circuit cards, etc.

[0037] The determination unit 50 determines whether the output voltage Vm of the main power supply 25 is below the first threshold Vth1 (predetermined value). The determination unit 50 outputs the determination result of whether the output voltage Vm of the main power supply 25 is below the first threshold Vth1 to the focal length control unit 51. The output voltage Vm of the main power supply 25 may be the output voltage of the first battery, or may be the voltage after the output voltage of the first battery is stepped down or stepped up by the DC-DC converter. The output voltage Vm of the main power supply 25 may be the voltage between the main power supply 25 and the switching unit 27. The main power supply 25 may be the voltage of the power supply path 100 in a normal state.

[0038] A series of processes including the above-mentioned acquisition step in which the determination unit 50 acquires the output voltage Vm of the main power supply 25, the determination step in which the determination unit 50 determines whether the acquired output voltage Vm is lower than the first threshold value Vth1, and the output step in which the determination result is output to the focal length control unit 51 may be referred to as a "voltage determination process." This voltage determination process is executed periodically or at any timing in a normal state.

[0039] When the focal length control unit 51 receives an ON signal, it controls the focal length of each of the pair of variable-focus lenses 12. The focal length control unit 51 applies a voltage (applied voltage) to each of the pair of variable-focus lenses 12, and controls the focal length by controlling the applied voltage. Therefore, the control unit 31 can change the focal length of the pair of variable-focus lenses 12 by changing the applied voltage. When the focal length control unit 51 receives an OFF signal, it stops applying the applied voltage to the pair of variable-focus lenses 12.

[0040] The focal length control unit 51 can execute a first control and a second control when controlling the focal length. The first control is a control that constantly adjusts the focal length so that the visual target is focused on using the power of the main power supply 25. The first control is, for example, an autofocus process. The autofocus process is, for example, a process that executes a gaze detection step that detects the gaze direction of a person, a distance measurement step that measures the distance to an object in the detected gaze direction, and an automatic adjustment step that automatically adjusts the focal length of the electronic glasses 1 to the measured distance.

[0041] The second control is a control for maintaining the focal length at a predetermined distance D. The predetermined distance D is a focal length that is set in advance. The second control according to the first embodiment maintains the focal length at a predetermined distance D by using the power of the backup power supply 26. The predetermined distance D can be set to any value by the user. The predetermined distance D can be set for each of the pair of left and right variable-focus lenses 12. For example, the predetermined distance D (hereinafter referred to as the "predetermined distance D1") of one of the pair of left and right variable-focus lenses 12 (hereinafter referred to as the "first variable-focus lens") and the predetermined distance D (hereinafter referred to as the "predetermined distance D2") of the other variable-focus lens 12 (hereinafter referred to as the "second variable-focus lens") may be the same or different. Each piece of information on the predetermined distance D1 and the predetermined distance D2 is stored in advance in the storage unit 30.

[0042] The focal length control unit 51 selectively executes the first control and the second control. For example, while the main power supply 25 has enough power remaining to execute the first control, the focal length control unit 51 continuously executes the first control using the power of the main power supply 25. In other words, while the main power supply 25 has enough power remaining to execute the first control, the focal length control unit 51 continuously executes the first control in a normal state.

[0043] The period during which sufficient power remains in the main power supply 25 to perform the first control refers to, for example, a period during which the output voltage Vm of the main power supply 25 is equal to or greater than the first threshold value Vth1. When the voltage determination process by the determination unit 50 determines that the output voltage Vm is equal to or greater than the first threshold value Vth1, the focal length control unit 51 continues to perform the first control.

[0044] On the other hand, the focal length control unit 51 switches from the first control to the second control when there is insufficient power remaining in the main power supply 25 to perform the first control or when the power supply from the main power supply 25 is stopped. For example, when there is insufficient power remaining in the main power supply 25 to perform the first control, the focal length control unit 51 continuously performs the second control using the power of the standby power supply 26. In other words, while there is insufficient power remaining in the main power supply 25 to perform the first control, the focal length control unit 51 continuously performs the second control in the standby power supply state.

[0045] A case where there is not enough power remaining in the main power supply 25 to perform the first control or where the power supply from the main power supply 25 has stopped is, for example, a case where the output voltage Vm of the main power supply 25 falls below the first threshold value Vth1. When the voltage determination process by the determination unit 50 determines that the output voltage Vm falls below the first threshold value Vth1, the focal length control unit 51 switches from the first control to the second control.

[0046] For example, when it is determined that the output voltage Vm falls below the first threshold Vth1, the focal length control unit 51 controls the switching unit 27 to switch from the normal state to the standby power supply state. Then, the focal length control unit 51 stops the first control and executes the second control. Note that, when the main power supply 25 is charged and the output voltage Vm becomes equal to or higher than the second threshold Vth2 that is higher than the first threshold Vth1, the focal length control unit 51 may control the switching unit 27 to switch from the standby power supply state to the normal state and execute the first control. Note that the second threshold Vth2 is higher than the first threshold Vth1 in order to form a hysteresis, but may be the same value as the first threshold Vth1.

[0047] Here, the first threshold Vth1 may be set to, for example, the voltage value of the output voltage Vm when it becomes impossible to adjust the focal length of the variable-focus lens 12. For example, the first threshold Vth1 may be the lower limit of a voltage range (hereinafter, referred to as the "operable range") in which the electronic glasses 1 can operate normally. However, the first threshold Vth1 is not limited to this and may be set to any value.

[0048] The output unit 52 outputs predetermined information when the focal length is changed to a predetermined distance D by the focal length control unit 51. The output unit 52 outputs predetermined information, for example, when the first control is switched to the second control. The output of the predetermined information may be, for example, a mode that notifies at least one of the following: switching from the main power source 25 to the backup power source 26; low battery level; need for early charging; and that autofocus processing has been stopped due to low battery level. For example, the output mode of the predetermined information is performed in a mode that appeals to at least one of the human senses of sight, hearing, and touch. The output of the predetermined information may be, for example, a display of a message indicating the predetermined information, a warning sound or voice output, a flashing or lighting warning light, or a combination of two or more of them.

[0049] For example, when the focal length is changed to a predetermined distance D, the output unit 52 may display predetermined information on a partial area of ​​the lens of one or both of the pair of variable-focus lenses 12. As an example, the output unit 52 may display a message indicating the predetermined information, may display a warning mark as the predetermined information, or may display both as the predetermined information, on a partial area of ​​the lens of one or both of the pair of variable-focus lenses 12.

[0050] Furthermore, the output unit 52 may output the predetermined information to a device other than the electronic glasses 1. The device other than the electronic glasses 1 is an information terminal capable of wired or wireless communication with the electronic glasses 1, such as a mobile phone, a smartphone, a tablet terminal, a notebook computer, or a wearable terminal.

[0051] The focal length adjustment method according to the first embodiment will be described below with reference to Fig. 5. Fig. 50 is a flow diagram of the focal length adjustment method according to the first embodiment.

[0052] The determination unit 50 acquires the output voltage Vm of the main power supply 25 (step S101). Then, the determination unit 50 determines whether the acquired output voltage Vm is below the first threshold Vth1 (step S102). The focal length control unit 51 executes the first control when the output voltage Vm is equal to or greater than the first threshold Vth1 (step S103). For example, the focal length control unit 51 executes the first control such as autofocus processing when it is determined that the output voltage Vm is not below the first threshold Vth1 immediately after the electronic glasses 1A are turned on. Also, when the focal length control unit 51 is executing the first control, if it is determined that the output voltage Vm is not below the first threshold Vth1, it continues to execute the first control. After the process of step S103 is executed, the process returns to step S101.

[0053] When the output voltage Vm is equal to or greater than the first threshold Vth1, the processes of steps S101 to S103 are repeated, and the first control is therefore constantly executed. Here, the constant execution of the first control consumes power from the main power supply 25, and the output voltage Vm gradually decreases. When the output voltage Vm decreases and falls below the first threshold Vth1, in step S102, the determination unit 50 determines that the output voltage Vm is below the first threshold Vth1. When the determination unit 50 determines that the output voltage Vm is below the first threshold Vth1, the switching unit 27 switches from the normal state to the standby power supply state (step S104).

[0054] For example, when it is determined in step S102 that the output voltage Vm is below the first threshold Vth1, the focal length control unit 51 transmits a first control signal to the switching unit 27. When the switching unit 27 receives the first control signal, it switches from the normal state to the standby power supply state. However, this is not limited thereto, and the switching unit 27 may have a circuit configuration that switches from the normal state to the standby power supply state when the output voltage Vm falls below the first threshold Vth1 regardless of the first control signal.

[0055] Furthermore, when it is determined that the output voltage Vm is below the first threshold Vth1, the focal length control unit 51 switches from the first control to the second control that maintains the focal length at a predetermined distance D (step S105). In other words, when it is determined that the output voltage Vm is below the first threshold Vth1, the focal length control unit 51 changes the focal length to a preset predetermined distance D and maintains the focal length at the predetermined distance D.

[0056] As an example, when it is determined that the output voltage Vm falls below the first threshold Vth1, the focal length control unit 51 stops the autofocus process, changes the focal length to a predetermined distance D, and maintains the focal length at the predetermined distance D. The process of step S105 may be performed simultaneously with the process of step S104, or may be performed before step S104. In this way, for example, the focal length is constantly adjusted by the autofocus process in the normal state, and the focal length is maintained at the predetermined distance D in the standby power state.

[0057] When it is determined that the output voltage Vm is lower than the first threshold value Vth1, the focal length control unit 51 maintains the focal length at a predetermined distance D. As a result, even if the focal length of the variable-focal-length lens 12 cannot be adjusted due to a drop in the output voltage of the main power supply 25 or loss of the output voltage, the focal length can be maintained at the preset predetermined distance D using the power of the backup power supply 26, thereby reducing inconvenience to the user.

[0058] For example, when the output voltage Vm falls below the lower limit of a voltage range (hereinafter referred to as the "operable range") in which the electronic eyeglasses 1 can operate normally, the first control, such as the autofocus process, may not operate normally. As a result, the first control may be stopped with the focal length set to an inconvenient value for the user. For example, assume that the first control is stopped when a wearer who is doing housework or work at home happens to be looking at the scenery outside. In this case, the variable focus lens is focused on the scenery outside, i.e., a distant object. As a result, even if the wearer tries to resume housework or work, he or she may not be able to see objects located nearby, and may not be able to perform the housework or work.

[0059] On the other hand, when the output voltage Vm falls below the first threshold Vth1, the focal length control unit 51 according to the first embodiment can perform a second control to change and maintain the focal length of the variable-focus lens 12 at a predetermined distance D so that, for example, an object placed nearby is brought into focus. This can reduce the inconvenience to the wearer caused by being unable to focus.

[0060] Here, in the second control, the focal length control unit 51 can change and maintain the focal length so that the focus is on a distant object, not a near object, or an intermediate object between far and near. That is, the predetermined distance D can be set to, for example, either a first focal length, which is a focal length for viewing a distant object, or a second focal length, which is a focal length for viewing an object between intermediate and near.

[0061] For example, the user may set the specified distance D in advance by operating the operation unit 14 provided on the electronic glasses 1, or may set the specified distance D by operating an information terminal capable of communicating with the electronic glasses 1 (e.g., a mobile phone, a smartphone, a tablet device, a laptop computer, and a wearable device).

[0062] For example, when both the specified distance D1 and the specified distance D2 are set to the first focal length, the focal length control unit 51, for example, in step S105, changes and maintains both the focal length of the first variable-focus lens and the focal length of the second variable-focus lens to the first focal length.

[0063] For example, when both the specified distance D1 and the specified distance D2 are set to the second focal length, the focal length control unit 51, for example, in step S105, changes and maintains both the focal length of the first variable-focus lens and the focal length of the second variable-focus lens to the second focal length.

[0064] For example, the predetermined distance D1 may be set to the first focal length, and the predetermined distance D2 may be set to the second focal length. In this case, the focal length control unit 51 changes the focal length of the first variable-focus lens to the first focal length and maintains it there, and changes the focal length of the second variable-focus lens to the second focal length and maintains it there, for example, in step S105. With this configuration, the user can view objects from far to close.

[0065] After the process of step S105 is executed, the determination unit 50 acquires the output voltage Vm of the main power supply 25 in the standby power supply state (step S106), and determines whether the acquired output voltage Vm exceeds the second threshold value Vth2 (step S107). If the determination unit 50 determines that the output voltage Vm exceeds the second threshold value Vth2, the switching unit 27 switches from the standby power supply state to the normal state (step S108).

[0066] For example, when it is determined in step S107 that the output voltage Vm is greater than the second threshold Vth2, the focal length control unit 51 transmits a second control signal to the switching unit 27. When the switching unit 27 receives the second control signal, it switches from the standby power supply state to the normal state. However, this is not limited thereto, and the switching unit 27 may have a circuit configuration that switches from the standby power supply state to the normal state when the output voltage Vm exceeds the second threshold Vth2 regardless of the second control signal.

[0067] Furthermore, when it is determined that the output voltage Vm exceeds the second threshold Vth2, the focal length control unit 51 switches from the second control to the first control (step S109). In other words, when it is determined that the output voltage Vm exceeds the second threshold Vth2, the focal length control unit 51 cancels the maintenance of the focal length at the predetermined distance D, which is a fixed value. As an example, when it is determined that the output voltage Vm exceeds the second threshold Vth2, the focal length control unit 51 cancels the maintenance of the focal length at the predetermined distance D and resumes the autofocus process. The process of step S108 may be performed simultaneously with the process of step S107, or may be performed before step S107.

[0068] In step S107, if the determination unit 50 determines that the output voltage Vm is below the second threshold Vth2, the process proceeds to step S105, and the second control continues. In this way, if the focal length control unit 51 determines that the output voltage Vm is below the first threshold Vth1, the focal length control unit 51 stops the autofocus process and changes the focal length to the predetermined distance D. Then, the focal length control unit 51 maintains the focal length at the predetermined distance D until the main power supply 25 is charged, etc., and the output voltage Vm exceeds the second threshold Vth2.

[0069] As described above, the electronic glasses 1 according to the first embodiment include main power supply 25 and backup power supply 26. When the output voltage Vm of main power supply 25 falls below a predetermined value (first threshold value Vth1), the electronic glasses 1 use the power of backup power supply 26 to change and maintain the focal length at predetermined distance D. With this configuration, even if focal length adjustment in variable-focus lens 12 stops, the focal length can be maintained at the preset predetermined distance D, reducing the inconvenience to the user caused by an inability to focus.

[0070] Second embodiment The electronic glasses 1A according to the second embodiment will be described below. Fig. 6 is a block diagram of the main configuration of the electronic glasses 1A according to the second embodiment. The electronic glasses 1A according to the second embodiment differ from the first embodiment in that they do not include a backup power supply 26.

[0071] The electronic glasses 1A include a glasses frame 11, a pair of variable focus lenses 12, a DC power source 13A, an operation unit 14, and a control unit 16A.

[0072] Fig. 7 is a schematic diagram of a DC power supply 13A according to the second embodiment. As shown in Fig. 7, the DC power supply 13A includes a main power supply 25. Unlike the first embodiment, the DC power supply 13A does not include a standby power supply 26. Therefore, the DC power supply 13A supplies DC power from only one power supply system, i.e., the power of the main power supply 25, to the power supply path 100.

[0073] The control unit 16A is provided, for example, inside one or both of the pair of temples 21. The control unit 16A has, for example, a storage unit 30 and a control unit 31A.

[0074] The control unit 31A is, for example, a processor such as a CPU or an MPU. Fig. 8 is a configuration diagram of each functional unit in the control unit 31 according to the first embodiment. As shown in Fig. 8, the control unit 31A includes a determination unit 50A, a focal length control unit 51A, and an output unit 52. The determination unit 50A, the focal length control unit 51A, and the output unit 52 are realized by executing a program stored in the storage unit 43.

[0075] The determination unit 50A determines whether the output voltage Vm of the main power supply 25 is below the third threshold Vth3 (predetermined value). The determination unit 50 outputs the determination result of whether the output voltage Vm of the main power supply 25 is below the third threshold Vth3 to the focal length control unit 51A. The voltage determination process according to the second embodiment differs from the first embodiment in that it determines whether the output voltage Vm is below the third threshold Vth3 in the determination step. The third threshold Vth3 is a threshold for switching from the first control to the second control. The third threshold Vth3 is set so that the second control operates stably with the power of the main power supply 25 until a certain time has elapsed since the first control was switched to the second control.

[0076] The focal length control unit 51A can execute a first control and a second control when controlling the focal length. The first control according to the second embodiment is similar to that of the first embodiment. The second control according to the second embodiment differs from the first embodiment in that it uses the power of the main power supply 25. That is, the second control according to the second embodiment maintains the focal length at a predetermined distance D by using the power of the main power supply 25.

[0077] When the determination unit 50A determines that the output voltage Vm is not below the third threshold Vth3, the focal length control unit 51A executes the first control instead of the second control. On the other hand, when the determination unit 50A determines that the output voltage Vm is below the third threshold Vth3, the focal length control unit 51A switches from the first control to the second control. In other words, when the determination unit 51A determines that the output voltage Vm is below the third threshold Vth3, the focal length control unit 51A stops the first control and executes the second control. Note that, when the main power supply 25 is charged and the output voltage Vm becomes equal to or higher than the fourth threshold Vth4 that is higher than the third threshold Vth3, the focal length control unit 51A may stop the second control and execute the first control. Note that the fourth threshold Vth4 is larger than the third threshold Vth3 due to the formation of hysteresis, but may be the same value as the third threshold Vth3.

[0078] The focal length adjustment method according to the second embodiment will be described below with reference to Fig. 9. Fig. 9 is a flow diagram of the focal length adjustment method according to the second embodiment.

[0079] The determination unit 50A acquires the output voltage Vm of the main power supply 25 (step S201). Then, the determination unit 50A determines whether the acquired output voltage Vm is below the third threshold Vth3 (step S202). The focal length control unit 51A executes the first control when the output voltage Vm is equal to or greater than the third threshold Vth3 (step S203). For example, the focal length control unit 51A executes the first control such as an autofocus process when it is determined that the output voltage Vm is not below the third threshold Vth3 immediately after the electronic glasses 1A are turned on. Also, when the focal length control unit 51A executes the first control, it continues to execute the first control when it is determined that the output voltage Vm is not below the third threshold Vth3. After the process of step S203 is executed, the process returns to the process of step S201.

[0080] When the output voltage Vm is equal to or greater than the third threshold Vth3, the processes of steps S201 to S203 are repeated, and the first control is therefore constantly executed. Here, the first control is constantly executed, and as a result, the power of the main power supply 25 is consumed, and the output voltage Vm gradually decreases. When the output voltage Vm decreases and falls below the third threshold Vth3, in step S202, the determination unit 50A determines that the output voltage Vm is below the third threshold Vth3.

[0081] When the determination unit 50A determines that the output voltage Vm is below the third threshold Vth3, the focal length control unit 51A switches from the first control to the second control that maintains the focal length at a predetermined distance D (step S204). In other words, when the determination unit 50A determines that the output voltage Vm is below the third threshold Vth3, the focal length control unit 51A changes the focal length to a preset predetermined distance D and maintains the focal length at the predetermined distance D.

[0082] As an example, when it is determined that the output voltage Vm is below the third threshold Vth3, the focal length control unit 51A stops the autofocus process and changes the focal length to a predetermined distance D. In this way, when it is determined that the output voltage Vm is below the third threshold Vth3, the focal length control unit 51A maintains the focal length at the predetermined distance D. This makes it possible to change and maintain the focal length at the predetermined distance D before the adjustment of the focal length is stopped due to a drop in the output voltage of the main power supply 25. As a result, even when the adjustment of the focal length is stopped, the electronic glasses 1A maintain the focal length at the predetermined distance D desired by the user, so that the inconvenience of the wearer due to the inability to focus can be reduced. Note that the setting of the predetermined distance D is the same as in the first embodiment, and therefore a description thereof will be omitted.

[0083] After the process of step S204 is executed, the determination unit 50A acquires the output voltage Vm (step S205) and determines whether the output voltage Vm exceeds the fourth threshold Vth4 (step S206). When it is determined that the output voltage Vm exceeds the fourth threshold Vth4, the focal length control unit 51A switches from the second control to the first control (step S207). In other words, when it is determined that the output voltage Vm exceeds the fourth threshold Vth4, the focal length control unit 51A cancels the maintenance of the focal length at the fixed value, which is the predetermined distance D, and executes the first control. As an example, when it is determined that the output voltage Vm exceeds the fourth threshold Vth4, the focal length control unit 51A cancels the maintenance of the focal length at the predetermined distance D and resumes the autofocus process.

[0084] In step S206, when the determination unit 50A determines that the output voltage Vm is below the fourth threshold Vth4, the focal length control unit 51A continues the second control. In this way, when the focal length control unit 51A determines that the output voltage Vm is below the third threshold Vth3, it stops the autofocus process and changes the focal length to the predetermined distance D. Then, the focal length control unit 51A maintains the focal length at the predetermined distance D until the main power supply 25 is charged or the like and the output voltage Vm exceeds the fourth threshold Vth4.

[0085] As described above, when the output voltage Vm of the main power supply 25 falls below a predetermined value (third threshold value Vth3), the electronic glasses 1A according to the second embodiment change and maintain the focal length at the predetermined distance D. With this configuration, even if the focal length adjustment of the variable-focus lens 12 stops, the focal length can be maintained at the preset predetermined distance D, reducing the inconvenience to the user caused by an inability to focus.

[0086] The order of execution of each process, such as operations, procedures, steps, and stages in the devices, systems, programs, and methods shown in the claims, specifications, and drawings, is not specifically stated as "before," "prior to," or the like. It should also be noted that the order of execution of each process may be arbitrary, as long as the output of a previous process is not used in a subsequent process. Even if the operational flow in the claims, specifications, and drawings is explained using "first," "next," or the like for convenience, this does not mean that it is essential to execute the process in this order. [Explanation of symbols]

[0087] 1 electronic eyeglasses, 12 variable focus lens, 13 direct current power supply, 20 main power supply, 21 standby power supply, 31, 31A control unit

Claims

1. A DC power source; a variable focus lens operated by power from the DC power source; A control unit that controls the focal length of the variable-focus lens, The electronic eyeglasses, wherein, when the output voltage of the DC power supply falls below a predetermined value, the control unit changes the focal length to a preset predetermined distance and maintains the focal length at the predetermined distance.

2. The DC power supply is The main power supply; a standby power source capable of supplying power instead of the main power source; The electronic eyeglasses according to claim 1 , wherein the control unit maintains the focal length at the predetermined distance using power from the standby power supply when an output voltage of the main power supply falls below the predetermined value.

3. The control unit is capable of executing a first control for constantly adjusting the focal length so as to focus on a visual target, and a second control for maintaining the focal length at the predetermined distance, and when the output voltage falls below the predetermined value, the control unit switches from the first control to the second control. The electronic glasses according to claim 1 .

4. The DC power supply is The main power supply; a standby power source capable of supplying power instead of the main power source; The first control adjusts the focal length using power from the main power supply; The electronic glasses according to claim 3 , wherein the second control maintains the focal length at the predetermined distance by using power from the standby power supply.

5. The DC power supply supplies DC power from only one power supply system, The control unit switches from the first control to the second control when a voltage of the power supply system falls below the predetermined value. The electronic glasses according to claim 3 .

6. The variable focus lens comprises a pair of a first variable focus lens and a second variable focus lens held by a spectacle frame; the predetermined distance of the first variable focus lens is different from the predetermined distance of the second variable focus lens; The electronic glasses according to claim 1 .

7. The predetermined distance can be set to either a first focal length, which is a focal length for viewing a distant object, or a second focal length, which is a focal length for viewing an object located between a near distance and the distant distance and a middle distance between the near distance and the distant distance. The electronic glasses according to claim 1 .

8. The variable focus lens comprises a pair of a first variable focus lens and a second variable focus lens held by a spectacle frame; the predetermined distance of the first variable focus lens is set to the first focal length; The predetermined distance of the second variable focus lens is set to the second focal length. The electronic glasses according to claim 7.

9. when the focal length is changed to the predetermined distance, the control unit causes predetermined information to be displayed in a partial area of ​​the variable-focus lens. The electronic glasses according to claim 1 .

10. The electronic glasses according to claim 9 , wherein the predetermined information is information for notifying a user that a battery is low or that charging is required.

11. A method for adjusting a focal length of electronic glasses including a DC power source and a variable-focus lens operated by power from the DC power source, comprising the steps of: determining whether an output voltage of the DC power supply has fallen below a predetermined value; changing the focal length of the variable-focus lens to a predetermined distance when the output voltage falls below the predetermined value; maintaining the focal length at the predetermined distance; A focal length adjustment method including:

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