Optical scanning device

Abstract

The present invention provides 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 photodetector 24 measures the average values ​​μL(G1) and μL(G2) of the actual brightness L of the light beam emitted from the light source 21, corresponding to each of the multiple designated pixel groups G1 and G2 in the projected image Img, and the target brightness L of the light beam according to the irradiation data. tg Average value μL tg (G1), μL tg The drive current I supplied to the light source 21 is corrected so that the difference with (G2) is reduced.

Description

Technical Field

[0001] The present invention relates to an optical scanning device.

Background Art

[0002] In a laser scanning type projector, in order to keep the brightness of a projected image constant, when controlling the power of a laser, a method has been proposed in which the intensity of light is measured using a photodiode, and the power of the laser is corrected according to the measured light intensity (see, for example, Patent Document 1). At that time, the light for measurement by the photodiode is output below the projected image and / or beside the projected image. However, when the light for measurement is projected within the projection range, there is a problem that light unrelated to the actual projected image becomes visible, deteriorating the visibility of the video.

[0003] As a method for solving this problem, a method has been proposed in which the light source drive current is corrected so that there is no difference between the luminance based on the input image information and the luminance of the actually emitted luminous flux (see, for example, Patent Document 2). When image information is input, if it is a value close to the APC (Automatic Brightness Control) data after comparison, the position of the image information is defined as the APC dedicated projection position. Then, the luminance based on the image information at that position and the luminance of the actually emitted luminous flux are compared, and the luminance is corrected based on the comparison result. Depending on the image information, the correction location is determined at random end portions for each pixel.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, due to response delays in the photodiode (PD), the accuracy of the correction of the supply current to the laser diode (LD) may be significantly reduced. The projection period per pixel of the MEMS mirror device (MEMS device) that constitutes the optical deflector is short. For example, the projection conditions for the H-axis (horizontal axis) of the MEMS device are 3% non-projection ratio, 11° mechanical deflection angle (half-angle), and a sine wave with a frequency of 40kHz, resulting in 1280 pixels on the H-axis (horizontal axis). Under these conditions, even the pixel with the longest projection period (emission time) within the projection range (the pixel at the very edge) has an emission time of approximately 35ns. Therefore, the time that the PD constituting the photodetector 24 can use for measurement is shorter than that. Also, considering the processing in the subsequent ADC, the time required for processing may also be necessary, making correction at the pixel level difficult. In the case of MEMS devices with frequencies exceeding 40kHz, it may be less than 35ns. Furthermore, the time per pixel also decreases with an increase in the number of pixels due to higher resolution (e.g., 2160 pixels).

[0006] Therefore, the photodetector 24 is constrained to be able to measure within the emission time of at least one pixel. Furthermore, if a photodetector 24 (for example, a PD) with a rise time of 15 ns is used, nearly half of the pixel's time (35 ns) should not be measured (errors will occur). Even if the PD itself measures in time, correction processing requires converting it to a digital value using an ADC (analog-to-digital converter) in a later stage and inputting it to the microcontroller. When sampling voltage, it is necessary to sample after reaching a predetermined voltage, and it takes time from reaching the predetermined voltage to sampling. If the time until completion is long, it may not be possible to sample in time for the next sample, so it is preferable to reach the peak value as quickly as possible. For this reason, the constraints on selecting the PD that makes up the photodetector 24 become even stricter.

[0007] Furthermore, the selection of a photodetector (PD) must consider cost while also considering important parameters such as response speed, light sensitivity, and dark current. Naturally, selecting a PD with both high response speed and sensitivity will result in a higher cost. Also, since sensitivity and response time are influenced by the size of the PD, these constraints must also be considered during selection. As a result, it is difficult to simultaneously satisfy the selection of a PD constituting the photodetector 24 for correction at one pixel and other conditions, and it becomes necessary to compromise on one of the conditions, such as cost. Similar challenges also arise with optical deflectors other than MEMS devices.

[0008] Therefore, the present invention aims to provide a device that can appropriately control the light emission intensity of a light-emitting device in order to control the brightness of the projected image to a brightness according to the data, while reducing the effect of the response delay of the photodetector. [Means for solving the problem]

[0009] The optical scanning apparatus according to the first aspect of the present invention is 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. It is characterized by the following:

[0010] A second embodiment of the present invention is an optical scanning apparatus. 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 the first measured brightness of a first designated pixel group, which is set from two or more pixel data included in the irradiation data, to the irradiation control circuit, and sends the second measured brightness of a second designated pixel group, which is set from pixel data different from the two or more first designated pixel groups included in the irradiation data, to the irradiation control circuit. 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 irradiation control circuit is characterized by controlling the drive current of the light source based on the correction data. [Brief explanation of the drawing]

[0011] [Figure 1] A diagram illustrating the configuration of an optical scanning device as one embodiment of the present invention. [Figure 2] A flowchart illustrating the functions of an optical scanning device. [Figure 3] An explanatory diagram regarding data for brightness correction. [Figure 4] Diagrams illustrating the reference data, brightness correction data, and correction data. [Figure 5] An explanatory diagram showing the temperature dependence of the IL characteristics of red, green, and blue LDs. [Modes for carrying out the invention]

[0012] (composition) The optical scanning device shown in Figure 1, as an embodiment of the present invention, comprises a light source 21, an optical deflector 22, a light receiver 24, and an irradiation control circuit 100.

[0013] 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 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 a beam of light of different hues: red (R), green (G), and blue (B). The number of laser diodes constituting the light source 21 may be one, two, four, or five, instead of three.

[0014] 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, and to scan it in the H-axis (horizontal) and V-axis (vertical) directions, thereby forming a projected image Img (on the projection surface). The optical deflector 22 is composed of, for example, a MEMS mirror (see Japanese Patent Publication No. 2024-060686, Japanese Patent Publication No. 2024-007138, etc.). The optical deflector 22 may also be composed 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.

[0015] The light receiver 24 is configured to receive a portion of the laser light emitted from the light source 21 and output a signal to the irradiation control circuit 100 corresponding to the brightness L or light quantity (for example, expressed in 256 gradations (brightness gradations)) of the laser light. The light receiver 24 is composed of, for example, a photodiode (PD).

[0016] The irradiation control circuit 100 includes 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 an arithmetic processing unit (e.g., CPU, processor core, etc.) and a storage device (memory, etc.). The irradiation control circuit 100 is configured so that the arithmetic processing unit (hardware) reads a program (software) and data from the storage device, and performs arithmetic processing on the data according to the program, thereby executing a specified task described later.

[0017] (function) The functions of the optical scanning device with the above configuration will be explained using the flowchart in Figure 2.

[0018] The irradiation data processing circuit 102 acquires or receives irradiation data of the projected image from the input unit 20, which is an instruction signal input device such as an HDMI® or USB-C video input terminal or a processor (CPU) (Figure 2 / STEP 10). The irradiation data contains pixel data for each pixel, which includes the target brightness Ltg of three different color (R, G, B) light sources corresponding to each coordinate (x, y) in the projected image, i.e., each pixel. Furthermore, the irradiation data processing circuit 102 may receive light source temperature data representing the temperature of the light source 21 or its vicinity from the thermometer 210 (thermistor) (Figure 2 / STEP 12). The irradiation data processing circuit 102 transmits or outputs the irradiation data to the target brightness output circuit 104. The irradiation data processing circuit 102 may also transmit or output LD temperature data to the target brightness output circuit 104.

[0019] The target brightness output circuit 104 receives irradiation data from the irradiation data processing circuit 102 and determines the reference data f0(I,L) based on this data (Figure 2 / STEP 14). The reference data f0(I,L) is initial data representing the correlation or IL characteristic curve between the light source drive current I supplied to the light source 21 and the brightness L of the light source 21, for example, as schematically shown by the dashed line in Figure 4. The reference data f0(I,L) is read from the memory 40. The target brightness output circuit 104 transmits the reference data f0(I,L) to the correlation correction circuit 108.

[0020] Here, the target brightness output circuit 104 may also receive LD temperature data from the irradiation data processing circuit 102.

[0021] (move) Figure 5 shows the temperature dependence of the IL characteristic curves, which serve as reference data, for red LDs, blue LDs, and green LDs, from left to right. As shown with the red LD on the left side of Figure 5, when the output or brightness decreases with temperature changes even with the same light source drive current, it is preferable to have multiple reference data sets corresponding to different temperatures. That is, the memory 40 may store reference data f0(I,L) for each of several temperature ranges. For example, when a red LD is used in an output range up to 70mW, a common reference data set is used when the light source temperature is below 40°C. On the other hand, when the light source temperature is 40°C or higher, separate reference data sets are prepared for each temperature range (e.g., 40~60°C, 60~80°C) in order to achieve an output of 70mW. For reference data corresponding to fine changes in light source temperature, such as every 1°C, to be stored in the memory 40, the memory 40 needs to have a large capacity. This would be a bottleneck in implementation, especially for devices with small substrate sizes such as AR glasses, and would also be expensive. Reference data divided into temperature ranges is stored in memory 40, and fine-tuning is supplemented by corrections based on measured brightness, as described later.

[0022] In the first control cycle, since there is no projected image from the previous control cycle (previous projected image), the result of the determination process described later (Figure 2 / STEP 16) will be negative. Therefore, the correlation correction circuit 108 transmits the reference data f0(I,L) as is to the light source drive current correction circuit 110. Alternatively, the correlation correction circuit 108 refers to the reference data f0(I,L) and determines the target brightness L included in the irradiation data. tg The current value corresponding to this is calculated and transmitted. Then, the light source drive current correction circuit 110 refers to the reference data f0(I,L) and the target brightness L included in the irradiation data. tg Light emission command data (command value for light source drive current I) corresponding to the current value is transmitted to the light source drive circuit 112, and the light source drive circuit 112 controls the light source drive current I supplied to the light source 21 (Figure 2 / STEP22). Furthermore, the optical deflector drive control circuit 120 transmits scanning command data to the optical deflector drive circuit 122, and the optical deflector drive circuit 122 controls the voltage supplied to the optical deflector 22. As a result, the brightness L of the light source 21 corresponding to each pixel p(x,y) in the projected image is controlled, and the projected image is generated.

[0023] In the second and subsequent control cycles, since the measured data from the previous projection image is available from the photodetector, the measured luminance calculation circuit 106 receives the current value or signal output from the photodetector 24 and acquires the measured luminance based on the current value (Figure 2 / STEP 16). The "measured luminance" is data representing the luminance L of each hue (R, G, B) of the light source 21 corresponding to each pixel p(x, y) that constitutes the previous projection image. Since the irradiation data includes coordinate values ​​(x, y), when the light source 21 emits laser light to form the pixel with those coordinate values ​​(x, y), the photodetector 24 measures the luminance of (part of) the laser light, thereby synchronizing the emission timing of the light source 21 with the measurement timing of the photodetector 24. The measured luminance calculation circuit 106 transmits the measured luminance to the correlation correction circuit 108.

[0024] Here, regarding the measured brightness of each pixel, it is preferable to use the timing after the pixel has passed the center position while scanning each pixel as the acquisition timing. This is because, although the brightness is adjusted for each pixel, it takes time for the photodetector 24 (PD) to respond, and a slight timing difference may occur. Therefore, the timing is shifted from the timing when the pixel switches to allow the PD time to respond. For example, for a pixel where the optical deflector is scanned in 40ns, if the scanning of the pixel center occurs 20ns after the pixel switch, the measured brightness measured by the photodetector 24 at a predetermined timing between 20ns and 40ns after the switch to that pixel is taken as the measured brightness of that pixel.

[0025] The irradiation data processing circuit 102 determines whether or not to acquire brightness correction data (Figure 2 / STEP 16). First, it determines whether or not the measured brightness has been acquired. In the first control cycle, there is no projected image from the previous control cycle (previous projected image), and therefore the measured brightness has not been acquired and it is determined to be impossible. In the second and subsequent control cycles, where the measured brightness has been acquired, it further determines whether or not to acquire brightness correction data based on the irradiation data (Figure 2 / STEP 16).

[0026] The irradiation data processing circuit 102 selects two designated pixel groups, a first designated pixel group and a second designated pixel group, based on the target brightness data contained in the irradiation data received from the input unit 20. A designated pixel group is a group of two or more pixels. It consists of two or more pixels that are arranged consecutively in the scanning direction. In this embodiment, it is a group of pixels arranged in the H-axis direction.

[0027] The first designated pixel group is selected such that the first target luminance, which is the average value of the target luminances of the included pixels, falls within a predetermined range. Also, the second designated pixel group is selected such that the second target luminance, which is the average value of the target luminances of the included pixels, falls within a predetermined luminance range. Further, the first designated pixel group and the second designated pixel group are selected such that the first target luminance and the second target luminance have a luminance difference of a predetermined value or more. The predetermined luminance ranges including the first target luminance and the second target luminance are associated with the reference data f0(I, L), and are set to be further narrowed from the luminance ranges corresponding to the current values of I th or less I max . This is because the gradient of the current-luminance characteristic of the reference data f0(I, L) changes in the range below the threshold current I th and above the upper limit current I max . Therefore, as shown schematically by the solid line in FIG. 4, even if I th (and the low luminance range R - ) and I max (and the high luminance range R + ) vary due to temperature, deterioration, etc., the measured luminance is measured from a range with a constant gradient (intermediate luminance range R0) between I th and I max . th above I max and further narrowed from the luminance range corresponding to the following current values. This is because I th is less than and above the upper limit current I max in the range where the gradient of the current-luminance characteristic of the reference data f0(I, L) changes. Therefore, as shown schematically by the solid line in FIG. 4, even if I th (and the low luminance range R - ) and I max (and the high luminance range R + [[IDID=16]]) vary, the measured luminance is measured from a range with a constant gradient (intermediate luminance range R0) between I th and I max .

[0028] When the irradiation data satisfies the condition of selecting two designated pixel groups, namely the first designated pixel group and the second designated pixel group, new luminance correction data is calculated based on the irradiation data, and the acquisition of the luminance correction data is affirmed in order to update it from the reference data or the luminance correction data used in the previous cycle.

[0029] When the irradiation data does not satisfy the condition of selecting two designated pixel groups, namely the first designated pixel group and the second designated pixel group, if there is already luminance correction data used up to the previous time, the acquisition of the luminance correction data is affirmed in order to continue using it as it is.

[0030] If the illumination data does not meet the conditions for selecting the two designated pixel groups, the first and second designated pixel groups, or if there is no brightness correction data used in previous sessions, the data will not be acquired.

[0031] The selection of the first and second designated pixel groups, as described above, is performed separately for each hue (R, G, B) of the light source. In this embodiment, for the sake of simplicity, it is assumed that the first and second designated pixel groups selected for each hue (R, G, B) are the same. However, the first and second designated pixel groups may be different pixel groups for each hue (R, G, B). The first designated pixel group for red, the first designated pixel group for green, and the first designated pixel group for blue may be composed of different pixel groups. Also, the second designated pixel group for red, the second designated pixel group for green, and the second designated pixel group for blue may be composed of different pixel groups.

[0032] As the final decision on acquiring brightness correction data, the process may be performed only if the previous judgments are made for each hue and a positive judgment is made for acquisition of all hues. Alternatively, the process may be performed only for hues for which a positive judgment has been made for acquisition after the previous judgments have been made for each hue.

[0033] If it is decided to acquire brightness correction data, the brightness correction data is determined (Figure 2 / STEP20).

[0034] In the determination of whether or not to acquire brightness correction data (Figure 2 / STEP 16), if the conditions for selecting two designated pixel groups, the first designated pixel group and the second designated pixel group, are not met, the decision is made to continue using the brightness correction data used in previous attempts.

[0035] In the determination of whether or not to acquire brightness correction data (Figure 2 / STEP 16), if the conditions for selecting two designated pixel groups, the first designated pixel group and the second designated pixel group, are met, new brightness correction data is calculated for updating. The measured brightness of the first designated pixel group and the second designated pixel group is used to calculate the brightness correction data.

[0036] In the example in Figure 3, the first designated pixel group G1 consists of five pixels located at the left edge of the projected image Img, numbered 0, 1, 2, 3, and 4 from left to right. On the other hand, the second designated pixel group G2 consists of five pixels located at the right edge of the projected image Img, numbered 5, 6, 7, 8, and 9 from left to right. The upper right panel of Figure 3 shows the measured luminance L and its average value μL (G1) for each hue (R, G, B) of the light source 21 corresponding to each pixel 0, 1, 2, 3, and 4 constituting the first designated pixel group G1. The lower right panel of Figure 3 shows the measured luminance L and its average value μL (G2) for each hue (R, G, B) of the light source 21 corresponding to each pixel 5, 6, 7, 8, and 9 constituting the second designated pixel group G2.

[0037] The number of specified pixel groups may be three or more. The number of pixels constituting a specified pixel group may be changed in various ways, such as 3, 4, or any multiple of 6 or more, in addition to "5". The number of pixels constituting one specified pixel group may differ from the number of pixels constituting another specified pixel group. One specified pixel group and another specified pixel group may partially overlap. The leftmost and rightmost pixels in the projected image Img may not be included in any of the multiple pixels constituting a specified pixel group.

[0038] The correlation correction circuit 108, which receives the measured luminance from the measured luminance calculation circuit 106, calculates the first measured average value, which is the average value of the measured luminance of each pixel in the first designated pixel group G1. The first measured average value is calculated for each hue. In Figure 3, it is calculated for each of RGB. Similarly, the second measured average value, which is the average value of the measured luminance of each pixel in the second designated pixel group G2, is calculated for each hue.

[0039] Furthermore, the correlation correction circuit 108 calculates the first average drive current, which is the average value of the drive current of the pixels included in the first designated pixel group, and the second average drive current, which is the average value of the drive current of the pixels included in the second designated pixel group.

[0040] As schematically shown by the solid line in Figure 4, point P1, which corresponds to the first average drive current and the first measured average value, and point P2, which corresponds to the second average drive current and the second measured average value, are both considered to pass through two points in the intermediate luminance range R0 of the actual current-luminance characteristics.

[0041] The gradient of the current-luminance characteristic in the intermediate luminance range R0 is linear and constant. The correlation correction circuit 108 calculates the current-luminance characteristic f, which becomes the luminance correction data, from point P1, which is the first average drive current and the first measured average value, and point P2, which is the second average drive current and the second measured average value. amd Calculate (I,L). Current-luminance characteristic f amd The slope of (I,L) is, (2nd measured average value - 1st measured average value) / (2nd drive current average value - 1st drive current average value) It can be obtained from this. Furthermore, by adjusting it so that the obtained slope passes through P1 and P2, the current-luminance characteristic f amd (I,L) can be determined. Current-luminance characteristic f amd (I,L) is determined for each hue.

[0042] The obtained brightness correction data includes multiple pixels p that constitute the first designated pixel group G1 in the projection image Img shown on the left side of Figure 3. 11 , p 12 , ...p 1n1 (For example, n1=5) The measured luminance L(p) of each hue (R, G, B) of the light source 21 11 ), L(p 12 ), ‥L(p 1n1 The average value of ) μL(G1) = {L(p 11 )+L(p 12 )+‥+L(p 1n1 )} is included. Furthermore, the brightness correction data includes multiple pixels p that make up the second designated pixel group G2. 21 , p 22 , ...p 2n2 (For example, n2=5) The measured luminance L(p) of each hue (R, G, B) of the light source 21 21 ), L(p 22 ), ‥L(p 2n2 The average value of ) μL(G2) = {L(p 21 )+L(p22 )+‥+L(p 2n2 )} is included.

[0043] While the arithmetic mean is generally used as the "mean," any of the following can be used: the arithmetic mean, geometric mean, harmonic mean, or generalized mean, or any of these arithmetic mean or weighted sum.

[0044] Then, the light source drive current correction circuit 110 transmits light emission command data corresponding to the correction data f(I,L) to the light source drive circuit 112, and the light source drive current I supplied to the light source 21 is controlled by the light source drive circuit 112 (Figure 2 / STEP22). The light source drive current I is controlled according to the correction data f(I,L) for each hue. For example, as shown in Figure 4, the target brightness L of the light source 21 corresponding to a certain pixel tg is L tgm In this case, the light source driving current I0 according to the reference data f0(I,L) is corrected to the correction data f amd Light source driving current I according to (I,L) amd The data is corrected to (see the rightward arrow in Figure 4). Furthermore, the optical deflector drive control circuit 120 transmits the scan command data to the optical deflector drive circuit 122, and the optical deflector drive circuit 122 controls the voltage supplied to the optical deflector 22. As a result, the irradiation data and the correction data f amd A projected image is generated in which the brightness L (luminance gradation) of each pixel (coordinate values ​​(x, y)) is controlled according to (I, L).

[0045] (effect) In the optical scanning device with this configuration, the light source drive current I supplied to the light source 21 is corrected so that each of the luminance differences, including one luminance difference and the other luminance differences, is reduced. The "one luminance difference" refers to the multiple pixels p that constitute a designated pixel group G1 in the projected image Img. 11 , p 12 , ...p 1n1 The measured luminance L(p) of the luminous flux emitted from the light source 21, corresponding to each of the above. 11 ), L(p 12 ), ‥L(p 1n1 The average value of ) μL(G1) = {L(p 11 )+L(p12 )+‥+L(p 1n1 )} and the target brightness L of the luminous flux according to the irradiation data tg (p 11 ), L tg (p 12 ), ...L tg (p 1n1 ) Average value μL tg (G1) = {L tg (p 11 )+L tg (p 12 )+‥+L tg (p 1n1 )} is the difference between and . "Other luminance difference" is the difference between multiple pixels p that make up the other specified pixel group G2 in the projected image Img. 21 , p 22 , ...p 2n2 The measured luminance L(p) of the luminous flux emitted from the light source 21, corresponding to each of the above. 21 ), L(p 22 ), ‥L(p 2n2 The average value of ) μL(G2) = {L(p 21 )+L(p 22 )+‥+L(p 2n2 )} and the target brightness L of the luminous flux according to the irradiation data tg (p 21 ), L tg (p 22 ), ‥L tg (p 2n2 ) Average value μL tg (G2) = {L tg (p 21 )+L tg (p 22 )+‥+L tg (p 2n2 This is the difference between )} and . In other words, instead of the reference data f0(I,L), the correction data f amd The light source driving current I is controlled according to (I,L) (f0(I,L)→f in Figure 4). amd (See I,L and the right arrow).

[0046] The average values ​​μL(G1) and μL(G2) of the measured luminance of the light beam corresponding to each of the multiple pixels constituting the designated pixel groups G1 and G2 are used as the basis for correcting the light source drive current I. Therefore, even if the multiple pixels constituting the designated pixel groups G1 and G2 include pixels that degrade the accuracy of luminance measurement of the light beam in light of the photodetector 24, the effect of the response delay of the photodetector 24 is reduced. Then, the luminance L of the light beam emitted from the light source 21 corresponding to each pixel p(x,y) of the projected image Img is set to the target luminance L of the light beam corresponding to each pixel p(x,y) according to the irradiation data. tg From the perspective of approaching this goal, the accuracy of the correction of the light source driving current I based on the luminance measurement results will be improved.

[0047] (Other embodiments of the present invention) In the above embodiment, the reference data f(I,L) was determined according to the temperature of the light source 21 or its vicinity (for example, the substrate on which the light source 21 is mounted) as measured by the thermometer 210. However, in other embodiments, the thermometer 210 may be omitted, and the reference data f(I,L) may be determined independently of the light source temperature. This other embodiment may be applied when the correlation between the light source driving current I and the luminance L of the light source 21, or the IL characteristic curve, does not change significantly with the temperature of the light source 21.

[0048] Furthermore, if you want to control the brightness without changing it, you can use a laser with a higher output than necessary during laser selection. By using the maximum value when the temperature rises (e.g., 80°C) as the maximum value of the basic output, it can be used without problems. For example, with the red LD on the left side of Figure 5, if 40mW is sufficient brightness for the application, it will be possible to control the entire light source temperature range below 40mW. However, if a high-output light source 21 (LD) is used, the mechanism will become larger and the cost will increase, so the application in which it will be used needs to be considered.

[0049] The light receiver 24 may measure the brightness of a light beam in the latter half of the scanning period of each pixel constituting a plurality of designated pixel groups G1 and G2.

[0050] Furthermore, it can also be used for simpler feedback control using measured brightness. Steps 1 through 14 in Figure 2 are the same. In Step 16, instead of selecting two specified pixel groups, at least one specified pixel group is selected. In this case, when selecting the specified pixel group, it is sufficient that the average value of the target brightness of the pixels included is within a predetermined range. It is not necessary to set a predetermined brightness difference from the average values ​​of the other specified pixel groups.

[0051] Furthermore, when calculating the correction data in STEP 20, the measured average value, which is the average of the measured brightness of the pixels containing the specified pixel group, and the current average value, which is the average of the drive current of the pixels containing the specified pixel group, are used. In the correction data as well, the gradient of the current-brightness characteristic is the same as the reference data obtained in STEP 14, and the correction data f passes through the point determined by the measured average value and the current average value. amd Calculate (I,L).

[0052] Even in this case, since the specified pixel group is used, the effect of the response delay of the photodetector 24 is reduced, and the correction data f amd By using the corresponding drive current for (I,L), it becomes possible to operate in a way that approaches the target brightness.

[0053] Furthermore, while the current-luminance characteristic gradient is the same as the reference data, this approach is suitable for situations where the gradient is expected to change little due to factors such as temperature, such as when using only a single blue LD.

[0054] Furthermore, in determining the reference data in STEP 14, it is preferable to determine the reference data f(I,L) according to the temperature of the light source 21 or its vicinity (for example, the substrate on which the light source 21 is mounted) as measured by the thermometer 210.

[0055] This invention can be used in all types of optical scanning devices, such as image forming devices like projectors and lighting devices like vehicle lights. [Explanation of symbols]

[0056] 20...Input section 21‥Light source 22‥Optical deflector 24‥Receiver 40...memory 100... Irradiation control circuit 102... Irradiation data processing circuit 104...Target Brightness Output Circuit 106...Measured Brightness Calculation Circuit 108...Correlation Correction Circuit 110...Light source drive current correction circuit 112...Light source driving circuit 120... Optical deflector drive control circuit 122... Optical deflector drive circuit 210‥Thermometer Img‥Projected image

Claims

1. Light source and Optical deflector, A light receiver and, It has an irradiation control circuit, The irradiation control circuit drives a light deflector and controls the brightness of the light source based on irradiation data including 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 multiple 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 in 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.

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