JP2014186068A - Image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact projection projector which uses a MEMS and a semiconductor laser light source and is capable of maintaining white balance in tact even after reference light for controlling white balance is turned off.SOLUTION: An image display device includes: sensors for measuring ambient temperature and light source temperature; a Peltier element for cooling or heating a light source to a predetermined temperature level; temperature control means which controls temperature of the Peltier element to the predetermined level on the basis of values measured by the temperature sensors; correction means which detects reference light superimposed on an input image signal using a photosensor and controls light source drive means to keep the reference light constant; and light-shielding means for preventing the reference light from being projected onto a screen. Swing angle setting input means, which sets a swing angle of a reflective mirror on the basis of an external swing angle setting signal, turns the reference light off when the means determines that the reference light will escape the light shielding means to be projected on the screen, in which case the correction means, by itself or with the temperature control means, provides control to store the condition of the reference light just before being turned off.

Description

  The present invention relates to an image display apparatus using MEMS (Micro Electro Mechanical Systems) or the like.

  In recent years, small projection projectors using MEMS and semiconductor laser light sources have become widespread. For example, in Patent Document 1, “In an image projection apparatus that raster scans laser light using a MEMS resonant mirror and projects an image on a screen, the emission intensity of the laser light is adjusted in response to a change in the horizontal raster scan speed. A projector characterized by comprising control means for adjustment is described.

JP 2006-343397 A

  Patent Document 1 discloses a projector that projects an image by scanning a biaxial MEMS mirror in the horizontal and vertical directions and simultaneously modulating a laser light source. However, the semiconductor laser used in a small projection projector has a problem that the white balance of the display screen changes because the light quantity and forward current characteristics thereof change with temperature. In order to solve the problem, the reference light is projected outside the effective display area, and the white balance of the display screen is always controlled using the reference light. In addition, a light shielding plate for shielding the reference light is attached to the exit of the projector so that the reference light is not projected onto the screen.

  Further, when the deflection angle of the MEMS mirror is made smaller than a predetermined angle, there is a problem that the reference light is released from the light shielding plate and projected onto the screen and visually recognized as a bright spot by the observer.

  In the present invention, when the deflection angle of the MEMS mirror is smaller than a predetermined angle and the reference light is projected from the light shielding plate and projected onto the screen, the reference light is turned off so that the observer does not visually recognize it as a bright spot. Provided is a laser projection projector capable of maintaining a stable white balance even when turned off.

  In order to solve the above-described problems, the present invention employs, for example, the configuration described in the claims. As an example thereof, an image display device for projecting and displaying an image, a light source, light source driving means for driving the light source, a reflection mirror for reflecting light emitted from the light source and projecting it on an object, and the reflection mirror Mirror driving means for driving the image processing means, image processing means for signal processing of the input video signal, an optical sensor for measuring the light quantity of a plurality of light sources, a first temperature sensor for measuring the environmental temperature, and measuring the temperature of the light sources The temperature of the Peltier element is determined based on the measured values of the second temperature sensor, the Peltier element that cools or overheats the temperature of the light source to a predetermined value, and the first temperature sensor and the second temperature sensor. Temperature control means for controlling to a value, correction means for superimposing reference light on the input video signal, detecting the reference light by the photosensor, and controlling the light source driving means so that the reference light is constant; ,Previous A light shielding means for shielding the reference light from being projected onto the screen, and a deflection angle setting input means for setting a deflection angle of the reflection mirror based on a deflection angle setting signal from the outside, the deflection angle setting input means, When it is determined that the reference light deviates from the light shielding means and is projected onto the screen, the reference light is turned off, and the correction means, or the correction means and the temperature control means turn off the reference light. Control to keep the time state.

  According to the present invention, it is possible to provide a laser projection projector in which the white balance does not change even when the reference light is turned off.

It is explanatory drawing which showed the basic composition of the projection type projector of the present Example. It is the figure which showed the LD case temperature setting characteristic with respect to the environmental temperature of a present Example. It is explanatory drawing which showed the light quantity and the forward direction current characteristic of the monochromatic light source of a present Example. It is explanatory drawing which showed the internal structure of the image process part 2 of a present Example. FIG. 6 is a timing chart showing the operation of the image processing unit 2 of the present embodiment. It is explanatory drawing which showed the display position of the reference light of a present Example. It is the figure which showed the MEMS deflection angle and display luminance ratio of a present Example. It is the figure which showed the example of a display in the case of the MEMS deflection angle maximum of a present Example. It is the figure which showed the example of a display when the vertical direction MEMS deflection angle of a present Example is 1/2. It is the figure which showed the example of a display when the vertical / horizontal direction MEMS deflection angle of a present Example is each 1/2.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

  A configuration example of a projection type projector using MEMS in this embodiment is shown in FIG. The projection projector 1 includes an image processing unit 2, a laser driver 3, a laser 4, a reflection mirror 5, an optical sensor 6, a MEMS 7, a MEMS driver 8, a laser scanning locus 9, a display image 10, a light shielding plate 11, and a laser case temperature control unit 12. , Peltier element 13, thermal coupling structure 14 of Peltier element and laser case, first temperature sensor 15, second temperature sensor 16, and MEMS deflection angle setting input unit 17.

  The image processing unit 2 once stores a video signal input from the outside in the frame memory, generates a drive period signal (H synchronization signal, V synchronization signal) unique to the MEMS, and synchronizes with the signal to generate a video signal from the frame memory. Is read. Further, the laser driver 3 is controlled by the amount of light acquired from the optical sensor 6 to adjust the white balance to be constant. Details thereof will be described later. The laser driver 3 receives the image signal output from the image processing unit 2 and modulates the current value supplied to the laser 4 in proportion to the data value of the image signal. For example, the current amount to the laser 4 is increased when displaying a high gradation image, and the current amount to the laser 4 is decreased when displaying a low gradation image.

  For example, three lasers (4a, 4b, 4c) are used for the three primary colors Red, Green, and Blue, and modulation is performed for each RGB of the image signal, and RGB laser light is output. The RGB laser beams are combined by the reflection mirror 5. The reflection mirror 5 uses a special optical element that reflects a specific wavelength and transmits other wavelengths, and is generally called a dichroic mirror. For example, the reflection mirror 5a reflects all the laser light, the reflection mirror 5b transmits the laser light of the laser 4a and reflects the laser light of the laser 4b, and the reflection mirror 5c transmits the laser light of the lasers 4a and 4b and transmits the laser light of the laser 4c. It is a characteristic that reflects light. As a result, RGB laser beams can be combined into one.

  The synthesized laser beam is incident on the MEMS 7. The MEMS 7 has a biaxial rotation mechanism in one element, and the central mirror unit can vibrate in the horizontal direction and the vertical direction with the two axes. The vibration control of the mirror is performed by the MEMS driver 8. Although FIG. 1 shows an example in which the MEMS 7 has one element and two axes, it can also be configured by combining two MEMS having one element and one axis.

  The MEMS driver 8 generates a sine wave in synchronization with the H synchronization signal from the image processing unit 2, and generates a sawtooth wave in synchronization with the V synchronization signal to drive the MEMS 7. The MEMS 7 receives the sine wave and performs a sine wave movement in the horizontal direction, and simultaneously receives the sawtooth wave and performs a constant speed movement in one direction in the vertical direction. As a result, the laser beam is scanned along a locus such as the laser scanning locus 9 in FIG. 1, and the input image is projected by synchronizing the scanning with the modulation operation by the laser driver 4.

  Here, the optical sensor 6 is disposed so as to detect leakage light of RGB laser light synthesized by the reflection mirror 5. That is, the optical sensor 6 is disposed on the side of the laser 4c facing the reflection mirror 5c. The reflection mirror 5c has a characteristic of transmitting the laser beams of the lasers 4a and 4b and reflecting the laser beam of the laser 4c, but cannot have a characteristic of transmitting or reflecting 100%. 4a and 4b) or transmission (laser 4c).

  Therefore, by disposing the optical sensor 6 at the position shown in FIG. 1, the laser beam of several percent of the laser 4ca is transmitted and the laser beams of several percent of the lasers 4a and 4b are reflected and incident on the optical sensor 6. Can do. The optical sensor 6 measures the amount of incident laser light and outputs it to the image processing unit 2. In general, a photodiode or an OEIC (Opto-Electronic Integrated Circuit) for an optical disk drive can be used as the optical sensor 6.

  Since the operating temperature range of the laser 4 is narrower from 0 ° C. to 50 ° C. than other devices, temperature control is performed so that the laser case temperature falls within the above range. The temperature control is performed by the Peltier element 13 and the laser case temperature control unit 12 that controls the Peltier element 13. The Peltier element 13 is connected by a thermal coupling structure 14 of the laser 4, the Peltier element, and the laser case. FIG. 2 shows a characteristic example of the environmental temperature measured by the first temperature sensor 15 and the target set temperature of the laser case corresponding to the environmental temperature. This characteristic is an example in which the power consumption of the Peltier element is set to be as small as possible. The laser case temperature control unit 12 controls the Peltier element 13 so that the target temperature and the measured temperature of the second temperature sensor 16 are the same. A thermistor element can be used for the temperature sensors 15 and 16.

  Next, white balance control by the image processing unit 2 will be described with reference to FIGS. FIG. 3 is a diagram showing an operation in which the light quantity / forward current characteristic of the laser changes with temperature, and FIG. 4 is a diagram showing the internal configuration of the image processing unit 2.

  As shown in FIG. 3, the light quantity and forward current characteristics of the semiconductor laser change with temperature. In FIG. 3, there are two types of temperature conditions, T1 and T2, and there is a magnitude relationship of T1 <T2. In general, as the temperature increases, the forward current threshold current (Ith) tends to increase and the slope efficiency (η), which is the slope, tends to decrease. Therefore, when the drive current is constant, the amount of light changes as the temperature changes.

  For example, in the current characteristics when the temperature condition is T1, the light amount is P1 when the current is I1, and the light amount is P2 when the current is I2, but when this is the temperature condition T2, the light amount is P1 ′ when the current is I1. When the current is I2, the amount of light is P2 ′, and the amount of light decreases even when the same current is applied.

  Furthermore, since the amount of change in threshold value and slope efficiency is different for RGB, when the temperature changes, not only the brightness but also the white balance changes.

  Therefore, the light amounts L1 and L2 of the points P1 and P2 at the currents I1 and I2 at T1 are measured, and feedback control is performed so that the light amounts L1 and L2 are always constant. In general, such control is called APC (Auto Power Control). If the amount of RGB light is constant, the white balance does not change.

  Specifically, first, the light amounts L1 and L2 at two points (P1 and P2) at the temperature condition T1 are measured by the optical sensor 9, and the image processing unit 2 approximates the two points to a straight line. Then, the slope efficiency η of the approximate straight line and the point Ith that intersects the X axis where the light quantity of the approximate straight line is 0 are calculated. Similarly, the light amounts L1 'and L2' at the two points (P1 'and P2') at the temperature condition T2 are measured, and η 'and Ith' are calculated. The calculated η and η ′ and Ith and Ith ′ change depending on the temperature. However, η and Ith in the initial initial state are stored in the nonvolatile memory 3 (not shown), and η ′ after the temperature change is stored. The laser drive current is corrected so that the amount of light is constant according to the amount of change in Ith ′.

  That is, the current value is increased to I1 ′ so that the light amount at point P1 ′ is increased from L1 ′ to L1 and moved to P1 ″ so that the light amount is constant, and the light amount at point P2 ′ is increased from L2 ′ to L2 The current value is increased to I2 ′ so that the current value is moved to P2 ″. The calculation method for increasing the current values from I1 to I1 ′ and from I2 to I2 ′ is as follows. First, as shown by a one-dot chain line T1 ′ in FIG. Is added as an offset, and the slope efficiency variation is added to I1 and I2.

  Although the calculation process in the middle of the fluctuation value of the slope efficiency is a simple linear function equation, the calculation result is omitted. However, the calculation result is that the point P1 ″ is L1 × | 1 / η′−1 / η | and the point P2 ″ is L2 ×. | 1 / η'-1 / η |. The calculation result is expressed in absolute value because, when the temperature condition is T1> T2, the forward current characteristic of T2 has a tendency that Ith is smaller than T1 and the slope η is larger, This is because (1 / η′−1 / η) is a negative value.

  Next, FIG. 4 shows an example of the internal configuration of the image processing unit 2 for correcting the laser drive current. The image processing unit 2 temporarily stores (writes) the input video signal (video data) in the frame memory 202, and the stored video data is read in synchronization with the MEMS driving cycle. Control of writing to and reading from the frame memory 202 is performed by the synchronization processing unit 201. The synchronization processing unit 201 also supplies control signals (H synchronization signal, V synchronization signal) to the reference light generation unit 203 and the MEMS driver 8.

  The reference light generation unit 203 is a circuit that generates a timing and a reference light level for superimposing the reference light for acquiring the points P1 and P2 in FIG. 3 on the vertical blanking period of the video signal. Timings of superimposing the reference light on the vertical blanking period of the video signal are shown in FIGS.

  As shown in the input image signal waveform in FIG. 5, the points P1 and P2 of the reference light are superimposed on the vertical blanking period, and when the laser beam reaches the left end or the right end in the vertical blanking as shown in FIG. The timing of the overlapping position is adjusted so that the reference light is emitted. Further, the image processing unit 2 reduces the horizontal direction of the video signal so that the display area in the effective display period is inside the reference light compared to the vertical blanking, so that the reference light enters the effective display area. Things will disappear. Further, the position of the reference light is physically shielded by the light shielding plate 11 shown in FIG. 1 on the emission side of the MEMS 7, thereby making the reference light invisible.

  The adder 204 adds or switches the reference signal to the video signal at the timing and level generated by the reference light generation unit 203. Further, the reference light generation unit 203 generates the timings of the latch signals indicated by A1 and A2 in FIG. 5, the signal is connected to the APC processing unit 205, samples the output of the optical sensor 6, and the APC processing unit 205 Import inside. Based on the reference light data, the APC processing unit 205 uses the threshold current fluctuation values (Ith′−Ith) and the slope efficiency fluctuation values (L1 × | 1 / η′−1 / η |, L2 × |) described in FIG. 1 / η′−1 / η |) is calculated, and the gain circuit 301 and the offset circuit 302 in the laser driver 3 are controlled.

  Specifically, the gain circuit 301 is controlled by the fluctuation value of the slope efficiency, and the offset circuit 302 is controlled by the fluctuation value of the threshold current. The period for superimposing the reference signal is generally about several tens of us to several hundreds of us in consideration of the response time of the optical sensor 6.

  Next, an APC process and a laser case temperature control method when the MEMS deflection angle is changed will be described.

  The MEMS deflection angle setting input unit 17 in FIG. 1 receives the deflection angle setting signal set by the user and sets the horizontal and vertical MEMS deflection angle setting values in the MEMS driver 8. The MEMS driver 8 controls the MEMS deflection angle by changing the voltage amplitude of the MEMS drive signal (H direction sine wave, V direction sawtooth wave) according to the set value.

  FIG. 7 shows the relationship between the MEMS deflection angle and the luminance. The row of No. 1 in FIG. 7 is a case where the MEMS deflection angle is set to the maximum in both vertical and horizontal directions as shown in FIG. The row of No. 2 is a case where the vertical MEMS deflection angle is set to ½, as shown in FIG. 9, and the display area is ½ that of No. 1, but the luminance is doubled. Become. Further, the row of No. 3 is a case where the vertical and horizontal MEMS deflection angles are controlled to ½ as shown in FIG. 10, and the display area is ¼ that of No. 1, but the luminance is 4 times. By controlling the MEMS swing angle when displaying an image that requires attention, an image brighter than the normal display is output.

  When the horizontal deflection angle is also set small as shown in FIG. 10, the reference light (P1, P2) is removed from the light shielding area of the light shielding plate 11 and displayed as a bright spot on the screen. In this state, the MEMS deflection angle setting input unit 17 outputs a reference light extinction signal. The signal is connected to the APC processing unit 205 and the laser case temperature control unit 12. The APC processing unit 205 stops superimposing the reference light, that is, turns off the light.

  At this time, the values set in the gain circuit 301 and the offset circuit 302 of the laser driver 3 hold the set values immediately before the reference light is turned off. In addition, when the reference light extinction signal is input, the laser case temperature control unit 12 controls to maintain the laser case temperature just before the reference light extinction even if the environmental temperature changes. Since the laser case temperature does not change even if the environmental temperature changes due to the control, the white balance is maintained even if the reference light is turned off and the APC processing is turned off, so that a good display can be performed. In order to perform better display, it is preferable that the image is not composed of white and multi-level brightness as much as possible, for example, an image composed of primary colors and black.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

DESCRIPTION OF SYMBOLS 1 ... Projector unit, 2 ... Image processing part, 3 ... Laser driver, 4 ... Laser, 5 ... Reflection mirror, 6 ... Optical sensor, 7 ... MEMS, 8 ... MEMS driver, 9 ... Laser scanning locus | trajectory, 10 ... Display image, DESCRIPTION OF SYMBOLS 11 ... Light-shielding plate, 12 ... Laser case temperature control part, 13 ... Peltier element, 14 ... Thermal coupling structure, 15 ... 1st temperature sensor, 16 ... 2nd temperature sensor, 17 ... MEMS touch angle setting input part, DESCRIPTION OF SYMBOLS 201 ... Synchronization processing part, 202 ... Frame memory, 203 ... Reference light generation part, 204 ... Adder, 205 ... APC processing part, 301 ... Gain circuit, 302 ... Offset circuit

Claims (2)

An image display device for projecting and displaying an image,
A light source;
Light source driving means for driving the light source;
A reflection mirror that reflects the light emitted from the light source and projects it onto an object;
Mirror driving means for driving the reflecting mirror;
Image processing means for processing an input video signal;
An optical sensor for measuring the light quantity of a plurality of light sources;
A first temperature sensor for measuring environmental temperature;
A second temperature sensor for measuring the temperature of the light source;
A Peltier element that cools or superheats the temperature of the light source to a predetermined value;
Temperature control means for controlling the temperature of the Peltier element to a predetermined value based on measured values of the first temperature sensor and the second temperature sensor;
Correction means for superimposing reference light on an input video signal, detecting the reference light by the light sensor, and controlling the light source driving means so that the reference light becomes constant;
Light shielding means for shielding the reference light from being projected onto the screen;
A deflection angle setting input means for setting a deflection angle of the reflection mirror based on a deflection angle setting signal from the outside;
With
The deflection angle setting input means turns off the reference light when it is determined that the reference light deviates from the light shielding means and is projected onto the screen, and the correction means or the correction means and the temperature control means Is an image display device that controls to maintain the state when the reference light is extinguished.   2. The image display device according to claim 1, wherein when the deflection angle setting input unit determines that the reference light is projected from the light shielding unit and projected onto the screen, the display image has white and multi-level brightness. An image display device characterized by being an image that is not configured as much as possible.

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