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JP-2026074752-A - Optical scanning device

JP2026074752AJP 2026074752 AJP2026074752 AJP 2026074752AJP-2026074752-A

Abstract

[Problem] To provide a device that can appropriately control the light emission intensity of a light-emitting device in order to control the brightness of a projected image to a brightness according to the irradiation data, while reducing the effect of the response delay of the photodetector, which is the basis for controlling the brightness of the projected image. [Solution] The drive current I supplied to the light source 21 is corrected so as to reduce the difference between the average values μL( G1 ) and μL( G2 ) of the measured luminance L of the luminous flux emitted from the light source 21, measured by the photodetector 24 for each of the multiple designated pixel groups G1 and G2 in the projected image Img, and the average values μLtg ( G1 ) and μLtg ( G2 ) of the target luminance Ltg of the luminous flux according to the irradiation data. [Selection Diagram] Figure 4

Inventors

  • 安藤 優

Assignees

  • スタンレー電気株式会社

Dates

Publication Date
20260507
Application Date
20241021

Claims (9)

  1. Light source and Optical deflector, A light receiver and, It has an irradiation control circuit, The irradiation control circuit drives an optical deflector and controls the brightness of the light source based on irradiation data which includes a plurality of pixel data in which a target brightness is set for each pixel. The light receiver sends the measured brightness of a first designated pixel group, set from two or more pixel data included in the irradiation data, to the irradiation control circuit. The irradiation control circuit calculates a first measured average value from the average value of the measured brightness of the first designated pixel group, and controls the brightness of the light source based on the first measured average value. An optical scanning device characterized by the following features.
  2. Light source and Optical deflector, A light receiver and, It has an irradiation control circuit, The irradiation control circuit drives the light deflector and controls the brightness of the light source with a drive current based on irradiation data which includes a plurality of pixel data in which a target brightness is set for each pixel. The light receiver sends to the irradiation control circuit the first measured brightness of a first designated pixel group set from two or more pixel data included in the irradiation data, and sends to the irradiation control circuit the second measured brightness of a second designated pixel group set from pixel data different from the two or more first designated pixel groups included in the irradiation data. The irradiation control circuit calculates a first measured average value from the first measured luminance, and calculates a second measured average value from the average value of the second measured luminance. A first average current value is calculated, which is the average value of the drive current of the light source with the brightness of each pixel in the first designated pixel group controlled, and a second average current value is calculated, which is the average value of the drive current of the light source with the brightness of each pixel in the second designated pixel group controlled. Correction data, which is the current-luminance characteristic, is calculated from the first current average value and the first measured average value and the second current average value and the second measured average value. The optical scanning device is characterized in that the irradiation control circuit controls the drive current of the light source based on the correction data.
  3. It has even more memory, The memory stores reference data, which is the initial current-luminance characteristic. The irradiation control circuit performs multiple cycles of driving the light source and the light deflector based on the irradiation data. In the first cycle, the reference data is read from the memory, and the drive current of the light source is set based on the reference data and the irradiation data. The optical scanning apparatus according to claim 2, characterized in that, in the second and subsequent cycles, the drive current of the light source is set based on the correction data calculated from the first current average value and the first measured average value and the second current average value and the second measured average value of the previous cycle.
  4. The aforementioned light source has multiple light sources, The irradiation data sets the target brightness of each of the plurality of light sources for each pixel. The irradiation control circuit controls the brightness of each of the plurality of light sources based on the target brightness of the corresponding irradiation data. The first designated pixel group and the second designated pixel group are set for each of the plurality of light sources, The light receiver sends the first measured brightness and the second measured brightness of each of the plurality of light sources to the irradiation control circuit. The irradiation control circuit calculates the first measured average value and the second measured average value and the first current average value and the second current average value for each of the plurality of light sources. The optical scanning apparatus according to claim 2, characterized in that the correction data is calculated for each of the plurality of light sources.
  5. The optical scanning apparatus according to claim 4, wherein the plurality of light sources include a red light source, a blue light source, and a green light source.
  6. The irradiation control circuit performs multiple cycles of driving the light source and the light deflector based on the irradiation data. The optical scanning apparatus according to claim 2, characterized in that, in a frame after the correction data has been calculated, the drive current of the light source is controlled based on the correction data.
  7. It also has a thermometer, Multiple reference data are stored in the memory according to the temperature. The optical scanning apparatus according to claim 3, wherein the irradiation control circuit reads temperature data from the thermometer and selects the reference data corresponding to the temperature data from a plurality of reference data.
  8. The irradiation control circuit controls the first designated pixel group and the second designated pixel group, A first condition is that the first target brightness, which is the average value of the target brightness in the irradiation data of the pixel data constituting the first designated pixel group, is within a predetermined range. A second condition is that the second target brightness, which is the average value of the target brightness in the irradiation data of the pixel data constituting the second designated pixel group, is within a predetermined range. A third condition is that the difference between the first target brightness and the second target brightness is greater than or equal to a predetermined value, The optical scanning device according to claim 2, characterized in that it is configured to satisfy the following conditions.
  9. The optical scanning apparatus according to claim 2, characterized in that the first measured brightness and the second measured brightness at each pixel are the brightness measured by the photodetector at the timing when the scanning of the optical deflector has passed the center of the pixel.

Description

This invention relates to an optical scanning device. In laser scanning projectors, a method has been proposed to control the laser power to maintain a constant brightness of the projected image. This involves measuring the light intensity using a photodiode and correcting the laser power according to the measured light intensity (see, for example, Patent Document 1). In this method, the light used for measurement by the photodiode is output to the row below and/or to the side of the projected image. However, when the measurement light is projected within the projection range, it becomes visible as light unrelated to the actual projected image, reducing the visibility of the image. To address this problem, a method has been proposed to correct the light source drive current so that the difference between the brightness based on the input image information and the brightness of the actually emitted light beam is eliminated (see, for example, Patent Document 2). When image information is input, if it is close to the APC (Automatic Brightness Control) data, the position of that image information is defined as the APC-dedicated projection position. Then, the brightness based on the image information at that position is compared with the brightness of the actually emitted light beam, and the brightness is corrected based on the comparison result. Depending on the image information, correction points are determined randomly for each pixel and at the edges. Japanese Patent Publication No. 2003-005110Japanese Patent Publication No. 2010-175671 A diagram illustrating the configuration of an optical scanning device as one embodiment of the present invention.A flowchart illustrating the functions of an optical scanning device.An explanatory diagram regarding data for brightness correction.Diagrams illustrating the reference data, brightness correction data, and correction data.An explanatory diagram showing the temperature dependence of the IL characteristics of red, green, and blue LDs. (composition) The optical scanning device shown in Figure 1, as one embodiment of the present invention, comprises a light source 21, an optical deflector 22, a light receiver 24, and an irradiation control circuit 100. The light source 21 is composed of laser diodes (LDs) that emit laser light or a beam of light in accordance with the drive current I supplied from the light source drive circuit 112 in response to the light emission command data from the irradiation control circuit 100. In this embodiment, the light source 21 is composed of three laser diodes (LDs) that emit laser light or beams of red (R), green (G), and blue (B) of different hues. The number of laser diodes constituting the light source 21 may be one, two, four, or five, instead of three. The optical deflector 22 is configured to deflect the laser light emitted from the light source 21 in accordance with the voltage supplied from the optical deflector drive circuit 122 in response to scanning command data from the irradiation control circuit 100, thereby forming a projected image Img (on the projection surface) by scanning it in the H-axis (horizontal) and V-axis (vertical) directions. The optical deflector 22 is, for example, composed of a MEMS mirror (see Japanese Patent Publication No. 2024-060686, Japanese Patent Publication No. 2024-007138, etc.). The optical deflector 22 may also consist of a horizontal mirror (for example, a resonant mirror formed by MEMS) that scans the laser light sent from the dichroic mirror in the horizontal direction, and a vertical mirror (for example, a galvanometer mirror) that scans the laser light reflected by the horizontal mirror in the vertical direction. The light receiver 24 receives a portion of the laser light emitted from the light source 21 and is configured to output a signal to the irradiation control circuit 100 corresponding to the brightness L or light intensity (for example, expressed in 256 gradations (brightness gradations)) of the laser light. The light receiver 24 is composed of, for example, a photodiode (PD). The irradiation control circuit 100 comprises an irradiation data processing circuit 102, a target brightness output circuit 104, a measured brightness calculation circuit 106, a correlation correction circuit 108, a light source drive current correction circuit 110, and a light deflector drive control circuit 120. The irradiation control circuit 100 and its components consist of a processing unit (e.g., CPU, processor core, etc.) and a storage device (memory, etc.). The irradiation control circuit 100 is configured to execute a specified task, described later, by having the processing unit (hardware) read a program (software) and data from the storage device, and then performing calculations on the data according to the program. (function) The functions of the optical scanning device with the above configuration will be explained using the flowchart in Figure 2. The irradiation data processing circuit 102