Optical device, data glasses comprising an optical device, method for operating an optical device

Abstract

Method and optical device (100), wherein the optical device (100) comprises several laser cavities (102) and an evaluation electronics (116), wherein the optical device (100) is configured to emit light from the several laser cavities (102) in parallel to each other, to receive a reflected part of the light in the several laser cavities (102), and to evaluate the reflected part of the light with the evaluation electronics (116).

Description

State of the art

[0001] The invention relates to an optical device, a pair of data glasses comprising the optical device, and a method for operating an optical device.

[0002] Optical devices are used, for example, in laser feedback interferometry (LFI). LFI is a technique that exploits the phenomenon of self-mixing. Disclosure of the invention

[0003] An optical device comprises multiple laser cavities and evaluation electronics. The optical device is configured to emit light from the multiple laser cavities in parallel to one another, receive a portion of the reflected light within the cavities, and evaluate the reflected light using the evaluation electronics. This optical unit is used, for example, as part of an LFI sensor that scans across an eye and observes an interference signal from the emitted and reflected light to determine the pupil's position.

[0004] According to a first readout possibility, the optical device comprises two laser cavities, wherein the optical device comprises a laser diode for each laser cavity, which is configured to emit the light from the respective laser cavity, wherein the part of the light reflected back into the two laser cavities hits the laser diode of the respective laser cavity, wherein the evaluation electronics are configured to evaluate a voltage drop at the semiconductor junction of the laser diodes.

[0005] According to a second readout option, the optical device comprises two laser cavities, wherein the optical device is configured to emit the light from the two laser cavities, wherein the optical device comprises a photodiode, wherein the photodiode is configured to detect the part of the light reflected back into the two laser cavities, and wherein the evaluation electronics are configured to evaluate a current at the photodiode.

[0006] It may be provided that the optical device offers both readout options, with the evaluation electronics designed to evaluate the current and the voltage drop.

[0007] For example, the individual laser cavities are arranged on the photodiode. The common photodiode sums the reflected portion of the light and allows the evaluation electronics to analyze the sum.

[0008] A particularly compact design, e.g., as a laser chip in a common laser module, is achieved, for example, by including a carrier board for the optical device, with the photodiode being arranged on the carrier board.

[0009] A particularly compact design is achieved, for example, by including a common lens in the optical system for the multiple laser cavities.

[0010] A particularly compact design is achieved, for example, by the optical device comprising the carrier board and a cylinder, with the lens being connected to the carrier board via the cylinder.

[0011] It may be provided that the optical device is designed to transmit the light in a non-frequency-modulated operating mode of the optical device.

[0012] A particularly compact design is achieved, for example, by having the optical system include individual optics, especially waver-level optics, for each laser cavity.

[0013] A particularly compact design is achieved, for example, by enclosing the optical device in a substrate, with the individual laser cavities arranged on the substrate.

[0014] Data glasses may be provided, the data glasses comprising the optical device.

[0015] One method for operating the optical device involves emitting light from one or more laser cavities in parallel to each other, receiving a reflected portion of the light in the cavities, and evaluating this reflected portion using the evaluation electronics. This allows an image to be generated based on the reflected portion of the light.

[0016] According to the first readout option, the procedure involves emitting light from the two laser cavities, with the evaluation electronics assessing a voltage drop at the semiconductor junction of the laser diodes.

[0017] According to the second readout option, the procedure provides that the light is emitted from the two laser cavities, whereby the part of the light reflected back into the two laser cavities is detected by the photodiode, and a current at the photodiode is evaluated by the evaluation electronics.

[0018] Further advantageous embodiments can be found in the following description and the drawing. The drawing shows: Fig. 1 a section through an optical device, Fig. 2 a perspective view of the optical setup, Fig. 3 an evaluation electronics for the optical device, Fig. 4 an image scanned with a first laser cavity of the optical device, Fig. 5 an image scanned with a second laser cavity of the optical device, Fig. 6 an image scanned with the first laser cavity and the second laser cavity, Fig. 7. A flowchart showing the steps of a procedure for operating the optical device.

[0019] In Fig. Figure 1 shows a section through an optical device 100.

[0020] The optical device 100 comprises a carrier board 102. A common photodiode 104 is arranged on the carrier board 102. In this example, the optical device 100 comprises three laser cavities 106. Fig. Figure 1 shows a cross-section through two laser cavities 106. Only two or more than three laser cavities 106 can be provided. In this example, the laser cavities 106 are arranged on the common photodiode 104. This means that the common photodiode 104 is arranged such that light incident on the laser cavities 106 is detected by the common photodiode 104. In this example, the laser cavities 106 are arranged in a common substrate 108. Each laser cavity 106 is provided with an optional individual optic, in particular a wave-level optic 110. The optical assembly 100 includes a common lens 112 for the laser cavities 106. The optical assembly 100 includes a cylinder 114. The lens 112 is connected to the carrier board 102 via the cylinder 114. The optical device 100 includes an evaluation electronics unit 116. The optical device 100 includes one laser diode 118 per laser cavity 106.

[0021] The optical device 100 is configured to emit light from the laser cavities 106. The photodiode 104 is configured to detect the portion of the light reflected back into the laser cavities 106. The evaluation electronics 116 are configured to evaluate a current at the photodiode 104.

[0022] In Fig. Figure 2 shows a perspective view of optical device 100.

[0023] In Fig. Figure 3 shows the optical device 100 and the evaluation electronics 116 for the optical device 100 schematically.

[0024] The optical device 100 and the evaluation electronics 116 are, for example, components of an LFI sensor.

[0025] The evaluation electronics 116 is designed to control a laser driver 304 via a control signal, for example a Digital Analog Converter (DAC) 302.

[0026] The laser driver 304 supplies a current signal. The evaluation electronics 116 are configured to apply the current signal to the respective laser cavity 106.

[0027] The evaluation electronics 116 includes a multiplexer 306, which is designed to switch the current signal discretely to the individual laser cavities 106 one after the other.

[0028] The evaluation electronics 116 are configured to generate a switching signal 308 for the multiplexer 306. The switching signal 308 can be digital or analog. For two laser cavities 106, the switching signal 308 can be binary coded to discretely select one of the two laser cavities 106 at a time. For multiple laser cavities 106, the switching signal 308 can be coded to select each laser cavity 106 individually or to select the multiple laser cavities 106 together. In this example, it is provided that the multiple laser cavities 106 are each operated with a portion of the current from the current signal of the laser driver 304 when the multiple laser cavities 106 are selected together.

[0029] In Fig. Figure 3 shows two laser cavities 106, each connected to the multiplexer 306 via a power line 310.

[0030] By supplying the respective laser cavity 106 with the current of the current signal, the laser diode 118 of the respective laser cavity 106 begins to emit coherent light.

[0031] In this example, the coherent light is shaped by the optional individual optics 110, for example by the waver-level optics.

[0032] The coherent light is shaped into a beam 310 via the common optics 112.

[0033] In an application for scanning an eye, the light is propagated through a projection system, e.g., through the projection system of smart glasses. The projection system and the smart glasses are in Fig. 3 not shown.

[0034] The data glasses are, for example, retinal projection glasses.

[0035] Light enters the eye. Light striking the retina is reflected by the retina. A portion of the reflected light is bounced back into the laser cavities 106. This reflected light interferes with the light emitted by the respective laser cavity 106. The interference of the locally oscillating wave of the emitted light with the wave of the light reflected back into the respective laser cavity 106 results in a modulation of the optical power.

[0036] The light striking photodiode 104 generates a current. This current characterizes the modulation. This means the modulation is measured by photodiode 104.

[0037] The evaluation electronics 116, in this example, includes a high-pass filter 312. The high-pass filter 312 is optional. The optional high-pass filter 312 suppresses the DC signal in the current from the photodiode 104. The evaluation electronics 116 also includes a transimpedance amplifier 314. The transimpedance amplifier 314 is configured to amplify the current from the photodiode 104 and convert the amplified current into a voltage signal. In this example, the high-pass filter 312 is arranged between the transimpedance amplifier 314 and the photodiode 104.

[0038] The evaluation electronics 116 includes an analog-to-digital converter (ADC) 316. The ADC 316 is designed to digitize the voltage signal.

[0039] It may be provided that a pair of smart glasses includes the optical device 100. The optical device 100 is, for example, arranged on the smart glasses such that it can directly scan the eye of a wearer of the smart glasses. Alternatively, the optical device 100 may be arranged on the smart glasses such that it can scan the eye of a wearer of the smart glasses via an optical element arranged in the smart glasses for this purpose, which deflects the light from the optical device 100 onto the wearer's eye.

[0040] Instead of evaluating the current, it may be possible to evaluate a voltage drop across the respective laser diode 118. For example, the evaluation electronics 116 are configured to evaluate a voltage drop at the semiconductor junction of the respective laser diode 118.

[0041] For example, to evaluate the voltage drop, the respective laser cavity 106 is designed in such a way that the part of the light reflected back into the respective laser cavity 106 hits the laser diode 106 of the respective laser cavity 106.

[0042] In one embodiment, the evaluation electronics 116 are designed to evaluate the voltage drop instead of the current.

[0043] In one embodiment, the evaluation electronics 116 are designed to evaluate the voltage drop and the current.

[0044] The evaluation electronics 116 are, for example, designed to execute one or more of the following different control modes: 1. High-frequency switching between the individual laser cavities 102, for example at 20 MHz. The high-frequency switching between the individual laser cavities 102 is carried out, for example, by generating a single pixel with a coherence wavelength and phase in one laser cavity 102 through the reflected part of the light from another laser cavity 102. 2. Parallel operation of multiple laser cavities 102. In parallel operation, an interference signal is generated in each of the parallel-operated laser cavities 102. In parallel operation, the photodiode 104 serves as a summing element for the interference signals. This means that the evaluation electronics 116 samples a maximum of the interference signals. 3. Both laser cavities 102 are operated close to the lasing threshold. When the laser cavities 102 are operated close to the lasing threshold, they emit in a multimode. This results in several potential laser modes. Consequently, each laser cavity 102 switches between stimulated and spontaneous emission. This changes the coherence wavelength, resulting in a higher speckle density.

[0045] In Fig. Figure 4 shows an image 400 scanned with a first laser cavity 102 of the optical device. Image 400 shows a single image of the scanned image captured only with the first laser cavity 102.

[0046] In Fig. Figure 5 shows an image 500 scanned with a second laser cavity 102 of the optical device. Image 500 shows a single image of the scanned image captured only with the second laser cavity 102.

[0047] In Fig. Figure 6 shows an image 600 scanned in parallel with the first laser cavity 102 and the second laser cavity 102. Image 600 shows a single image of the scanned image captured using only the first laser cavity 102 and the second laser cavity 102.

[0048] This means that image 600 shows a combination of a first single image, captured by the first laser cavity 102, and a second single image, captured by the second laser cavity 102. The pixel at a position in image 600 represents a combination of the pixels that are simultaneously captured in the first and second laser cavities 102 during scanning, e.g., of the eye. This results in a significantly denser speckle pattern.

[0049] In Fig. Figure 7 shows a flowchart with steps of a procedure for operating the optical device 100.

[0050] The procedure includes step 702.

[0051] In step 702, light is emitted from one laser cavity 102 or from multiple laser cavities 102 in parallel to each other, and a reflected portion of the light is received in the multiple laser cavities 102. Whether the light is emitted from only one laser cavity 102 or from multiple laser cavities 102 in parallel is determined, for example, by the control mode.

[0052] Then, step 704 is executed.

[0053] In step 704, the reflected part of the light is evaluated using the evaluation electronics 116.

[0054] In one embodiment of the method, the voltage drop at the semiconductor junction of the laser diodes 118 is evaluated using the evaluation electronics 116.

[0055] In one embodiment of the method, the part of the light reflected back into the two laser cavities is detected by the photodiode 104 in step 702, and a current at the photodiode 104 is evaluated by the evaluation electronics 116 in step 704.

[0056] To generate an image, steps 702 and 704 are repeated for each pixel of the image, for example, during scanning, such as scanning the eye. The brightness of a pixel is determined, for example, by the evaluation electronics 116, depending on the intensity of the current or the voltage drop.

Claims

[1] An optical device (100), characterized by , that the optical device (100) comprises several laser cavities (102) and an evaluation electronics (116), wherein the optical device (100) is configured to emit light from the several laser cavities (102) in parallel to each other, to receive a reflected part of the light in the several laser cavities (102), and to evaluate the reflected part of the light with the evaluation electronics (116). [2] The optical device (100) according to claim 1, characterized by, that the optical device (100) comprises two laser cavities (102), wherein the optical device (100) comprises a laser diode (118) for each laser cavity (102), which is configured to emit the light from the respective laser cavity (102), wherein the part of the light reflected back into the two laser cavities (102) hits the laser diode (118) of the respective laser cavity (102), wherein the evaluation electronics (116) are configured to evaluate a voltage drop at the semiconductor junction of the laser diode (118)n. [3] The optical device (100) according to claim 1, characterized by, that the optical device (100) comprises two laser cavities (102), wherein the optical device (100) is configured to emit light from the two laser cavities (102), wherein the optical device (100) comprises a photodiode (104), wherein the photodiode (104) is configured to detect the part of the light reflected back into the two laser cavities (102), and wherein the evaluation electronics (116) is configured to evaluate a current at the photodiode (104). [4] The optical device (100) according to claims 2 and 3, characterized by , that the evaluation electronics (116) are designed to evaluate the current and the voltage drop. [5] The optical device (100) according to one of claims 3 or 4, characterized by , that the individual laser cavities (102) are arranged on the photodiode (104). [6] The optical device (100) according to any one of claims 3 to 5, characterized by, that the optical device (100) comprises a carrier board, wherein the photodiode (104) is arranged on the carrier board. [7] The optical device (100) according to any one of the preceding claims, characterized by that the optical arrangement (100) for the multiple laser cavities (102) includes a common lens. [8] The optical device (100) according to claim 7, characterized by , that the optical device (100) comprises the carrier board and a cylinder, wherein the lens is connected to the carrier board via the cylinder. [9] The optical device (100) according to any one of the preceding claims, characterized by , that the optical device (100) is configured to transmit the light in a non-frequency modulated operating mode of the optical device (100). [10] The optical device (100) according to any one of the preceding claims, characterized by, that the optical arrangement (100) for each laser cavity (102) comprises individual optics, in particular waver-level optics. [11] The optical device (100) according to any one of the preceding claims, characterized by , that the optical device (100) comprises a substrate, wherein the individual laser cavities (102) are arranged on the substrate. [12] Smart glasses, characterized by , that the data glasses comprise the optical device (100) according to one of claims 1 to 11. [13] Method for operating an optical device (100) according to any one of claims 1 to 11, characterized by , that light is emitted from a laser cavity (102) or from the several laser cavities (102) in parallel to each other and a reflected part of the light is received in the several laser cavities (102) (702), and the reflected part of the light is evaluated with the evaluation electronics (116) (704). [14] Method according to claim 13 for operating an optical device (100) according to any one of claims 2 to 11, characterized by , that the light is emitted from the two laser cavities (102), whereby a voltage drop at the semiconductor junction of the laser diode (118)n is evaluated with the evaluation electronics (116) (704). [15] Method according to claim 14 for operating an optical device (100) according to any one of claims 3 to 11, characterized by , that the light is emitted from the two laser cavities (102), the part of the light reflected back into the two laser cavities (102) is detected by the photodiode (104) (702), and a current at the photodiode (104) is evaluated by the evaluation electronics (116) (704).

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