JP2010256445A - Projection type display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply determine the thickness of a retardation plate of each liquid crystal panel of a projection type display apparatus. <P>SOLUTION: The projection type display apparatus 100 includes a liquid crystal panel 30G for modulating green light, and a liquid crystal panel 30R for modulating red light. The liquid crystal panel 30G has a retardation plate 64G. The liquid crystal panel 30R has a retardation plate 64R. The wavelength dispersion characteristics F_LC of retardation values of liquid crystal 34 are the same between the liquid crystal panel 30G and the liquid crystal panel 30R. The thickness dR of the retardation plate 64R is set in accordance with the thickness dG of the retardation plate 64G so that relation of a numerical formula (1) including a retardation value Re_LC(650) of the liquid crystal 34 for red light and a retardation value Re_REF(650) of the retardation plate 64G for the red light is formed. (1): dR=dG×(Re_LC(650))/Re_REF(650). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a projection display device using a liquid crystal panel.

  A retardation plate that compensates for the phase difference of light that has passed through the liquid crystal is installed in the liquid crystal panel (Patent Document 1). In a projection display device using a liquid crystal panel as a light modulator (light valve), a separate retardation plate is installed in each of a plurality of liquid crystal panels corresponding to different colors (red, green, blue) ( Patent Document 2 and Patent Document 3).

JP 2002-31426 A JP 2007-212997 A JP 2008-224959 A

  By the way, the chromatic dispersion characteristic (the property that the phase difference value is different for each wavelength) appears in the phase difference value of the liquid crystal of the liquid crystal panel. Therefore, it is desirable that the characteristics of the phase difference plate of each liquid crystal panel installed in the projection display device are individually selected for each liquid crystal panel (for each wavelength of incident light). However, it is necessary to individually perform a complicated operation for optimizing the characteristics of the phase difference plate according to the results of measurement and experiment for each of the plurality of liquid crystal panels. In view of the above circumstances, an object of the present invention is to easily determine the characteristics (thickness) of a retardation plate of each liquid crystal panel of a projection display device.

In order to solve the above-described problems, a projection display device according to the present invention includes a first liquid crystal panel that modulates light having a first wavelength and a second liquid crystal panel that modulates light having a second wavelength different from the first wavelength. And a projection optical system for projecting light modulated by each of the first liquid crystal panel and the second liquid crystal panel, the first liquid crystal panel has a first retardation plate, and the second liquid crystal panel is a second liquid crystal panel. The first liquid crystal panel and the second liquid crystal panel have a retardation plate, and the wavelength dispersion characteristics of the phase difference value of the liquid crystal are the same, and the first liquid crystal panel (or the second liquid crystal panel) with respect to the light of the second wavelength The thickness of the second retardation plate so that the relationship of the formula (A) including the retardation value Re_LC (λ2) of the liquid crystal and the retardation value Re_REF (λ2) of the first retardation plate for the second wavelength light is established. The length d2 is set according to the thickness d1 of the first retardation plate.
d2 = d1 (Re_LC (λ2) / Re_REF (λ2)) (A)

  In the above aspect, the second position of the second liquid crystal panel is determined according to the phase difference value Re_LC (λ2) of the first liquid crystal panel and the phase difference value Re_REF (λ2) of the first phase plate with respect to the light of the second wavelength. Since the thickness d2 of the retardation plate is set, it is not necessary to measure the wavelength dispersion characteristic of the retardation value of the second retardation plate to optimize the thickness. Therefore, there is an advantage that the thickness d2 of the second retardation plate can be easily determined. The thickness of the retardation plate means a dimension in a direction in which light is transmitted (direction of the optical axis).

A projection display device according to a preferred aspect of the present invention includes a third liquid crystal panel that modulates light having a third wavelength different from the first wavelength and the second wavelength, and the projection optical system includes the first liquid crystal panel, The light modulated by each of the second liquid crystal panel and the third liquid crystal panel is projected, and the third liquid crystal panel has the same wavelength dispersion characteristic of the phase difference value of the liquid crystal as the first liquid crystal panel and the second liquid crystal panel, A third retardation plate is provided, and the phase difference value Re_LC (λ3) of the liquid crystal of the first liquid crystal panel (or the second liquid crystal panel or the third liquid crystal panel) for the light of the third wavelength and the first for the light of the third wavelength. The thickness d3 of the third phase difference plate is set according to the thickness d1 of the first phase difference plate so that the relationship of the formula (B) including the phase difference value Re_REF (λ3) of the phase difference plate is established. D3 = d1 ・ (Re_LC (λ3) / Re_REF (λ3)) …… (B)

  In the above aspect, the work of optimizing the thickness of the third retardation plate of the third liquid crystal panel by measuring the wavelength dispersion characteristic of the retardation value in addition to the second retardation plate of the second liquid crystal panel. Is no longer necessary. Therefore, the effect that the thickness of each phase difference plate can be easily determined is particularly remarkable.

  In a more preferred aspect, the first wavelength light is green light, the second wavelength light is red light, and the third wavelength light is blue light. In the above aspect, the thickness of the second retardation plate corresponding to the red light and the thickness of the third retardation plate corresponding to the blue light are set by the calculations of the formulas (A) and (B), and the observer The thickness of the first retardation plate corresponding to the green light that is easily perceived by can be set with high accuracy according to the result of actually measuring the wavelength dispersion characteristic of the retardation value. Therefore, there is an advantage that a display quality deterioration due to insufficient phase difference compensation is hardly perceived by an observer.

  Note that “the chromatic dispersion characteristics of the retardation values are the same” for the liquid crystal of each liquid crystal panel means that the chromatic dispersion characteristics of the retardation values of the liquid crystals are completely matched in each liquid crystal panel, as well as the retardation of the liquid crystal. This includes the case where the chromatic dispersion characteristics of the values substantially match (substantially match) in each liquid crystal panel. In the case where the chromatic dispersion characteristics of the phase difference values substantially match, the liquid crystal panel design is intended so that the chromatic dispersion characteristics of the phase difference values of the liquid crystals match each other, but the manufacturing technology This includes a case where the wavelength dispersion characteristics of the phase difference values do not completely match in each liquid crystal panel as a result of the existence of errors due to the above constraints and the like.

  “The retardation plate is set to the thickness d” means that the thickness of the retardation plate is substantially set to the numerical value d in addition to the case where the thickness of the retardation plate is completely set to the numerical value d. Including the case where it is set. In the case where “the retardation plate is substantially formed with the thickness d”, the dimension of the thickness “d” is intended in the design of the retardation plate. This includes a case where the thickness of the retardation plate does not completely match the numerical value d as a result of the existence of an error caused by the error. That is, “the retardation plate is set to the thickness d” can be said in other words that the thickness of the retardation plate is set within an error range including the numerical value d.

  The present invention is also specified as a method for determining the characteristics (thickness) of a retardation plate. The method of the present invention includes a first process (for example, step S3 in FIG. 4) for specifying a retardation value Re_REF (λ2) for light of the second wavelength for the first retardation plate having a thickness d1, and light of the second wavelength. The thickness of the second retardation plate is calculated by the above formula (A) including the retardation value Re_LC (λ2) of the liquid crystal of the first liquid crystal panel and the retardation value Re_REF (λ2) specified in the first process. a second process (for example, step S4 and step S5 in FIG. 4) in which d2 is set in accordance with the thickness d1 of the first retardation plate. The effect similar to that of the projection display device of the present invention is realized by the above method. In a more preferred method, prior to the first step, the retardation value of the first retardation plate with respect to the light of the first wavelength is such that the retardation value of the liquid crystal of the first liquid crystal panel with respect to the light of the first wavelength (for example, FIG. 3). The phase difference value Re_LC (550)) is determined so as to determine the thickness d1 of the first retardation plate (for example, step S2 in FIG. 4).

It is a schematic diagram of the projection type display apparatus which concerns on embodiment of this invention. It is a schematic diagram which shows the structure of a liquid crystal panel. It is a graph which shows the phase difference value of a liquid crystal panel and a phase difference plate for every wavelength of incident light. It is a flowchart of the procedure which determines the thickness of each phase difference plate.

  FIG. 1 is a schematic view of a projection display device (projector) 100 according to one embodiment of the present invention. The projection display device 100 is a display device that projects a color image on a display surface (for example, a screen) 50. As shown in FIG. 1, the projection display device 100 includes an illumination device 10, a separation optical system 20, three liquid crystal panels 30 (30R, 30G, 30B), and a projection optical system 40.

  The illumination device 10 is a light source that emits illumination light (white light). The separation optical system 20 separates the illumination light into a plurality of monochromatic lights (red light, green light, blue light) and irradiates each liquid crystal panel 30. Specifically, the red light r of the illumination light enters the liquid crystal panel 30R after being reflected by the dichroic mirror 21 and the mirror 22. The green light g transmitted through the dichroic mirror 21 is reflected by the dichroic mirror 23 and enters the liquid crystal panel 30G. The blue light b transmitted through the dichroic mirror 23 enters the liquid crystal panel 30B after being reflected by the mirror 24 and the mirror 25.

  Each liquid crystal panel 30 is a light modulator (light valve) that modulates incident light to form an image. For example, a transmissive liquid crystal device in which the transmittance of a plurality of pixels arranged in a matrix is variably controlled is employed as the liquid crystal panel 30. The liquid crystal panel 30R modulates the red light r coming from the mirror 22 to form a red image. Similarly, the liquid crystal panel 30G forms a green image by modulating the green light g coming from the dichroic mirror 23, and the liquid crystal panel 30B forms a blue image by modulating the blue light b coming from the mirror 25.

  The projection optical system 40 projects the emitted light from each liquid crystal panel 30 onto the display surface 50. The projection optical system 40 includes a dichroic prism 42 that synthesizes light emitted from each liquid crystal panel 30 (red light, green light, and blue light), and a projection lens 44 that projects light emitted from the dichroic prism 42 onto the display surface 50. It is comprised including. Therefore, a color image is displayed on the display surface 50.

  FIG. 2 is a schematic diagram showing the structure of the liquid crystal panel 30 (30R, 30G, 30B). In FIG. 2, each element is illustrated as being separated for convenience, but in actuality, each element is in close contact with each other. As shown in FIG. 2, the liquid crystal panel 30 includes a first substrate 31 and a second substrate 32 that face each other. In the gap between the first substrate 31 and the second substrate 32, for example, a TN (Twisted Nematic) type or STN (Super TN) type liquid crystal 34 is sealed. The first substrate 31 is located on the light incident side (separation optical system 20 side), and the second substrate 32 is located on the light emission side (projection optical system 40 side). A polarizing plate 61 is disposed on the surface of the first substrate 31 opposite to the liquid crystal 34, and a polarizing plate 62 is disposed on the surface of the second substrate 32 opposite to the liquid crystal 34.

  Light incident on the liquid crystal 34 from the first substrate 31 side (linearly polarized light after passing through the polarizing plate 61) is converted into elliptically polarized light by adding a phase difference due to the birefringence of the liquid crystal 34. A phase difference plate 64 (phase difference compensation film) that compensates for a phase difference is arranged on the light emission side (projection optical system 40 side) with respect to the liquid crystal 34 so that elliptically polarized light is converted into linearly polarized light. Specifically, a phase difference plate 64 is interposed between the second substrate 32 and the polarizing plate 62. The liquid crystal panel 30R has a retardation plate 64R, the liquid crystal panel 30G has a retardation plate 64G, and the liquid crystal panel 30B has a retardation plate 64B.

  FIG. 3 is a graph illustrating the phase difference values (in-plane phase difference values) of the liquid crystal panel 30 (30R, 30G, 30B) and the phase difference plate 64 (64R, 64G, 64B) for each wavelength of incident light. is there. The material and thickness of the liquid crystal 34 are common to the three liquid crystal panels 30 (30R, 30G, 30B). Therefore, the phase difference value of the liquid crystal 34 in the three liquid crystal panels 30 (30R, 30G, 30B) shows an equivalent wavelength dispersion characteristic (characteristic F_LC in FIG. 3). That is, the longer the wavelength of incident light on the liquid crystal panel 30, the smaller the phase difference value. The phase difference value Re_LC (λ) in FIG. 3 means a phase difference added when light having a wavelength λ (λ = 450, 550, 650) is transmitted through the liquid crystal 34.

  In order to effectively compensate for the phase difference generated when light of wavelength λ passes through the liquid crystal 34, the phase difference value with respect to the wavelength λ is approximated by the liquid crystal 34 and the phase difference plate 64 (ideally match). )It is necessary. However, since the chromatic dispersion characteristics of the retardation value do not match between the actual liquid crystal 34 and the retardation plate 64, the retardation value of the liquid crystal 34 matches the retardation value of the retardation plate 64 for all wavelengths in the visible light range. It is difficult to make it. Therefore, when the phase difference plate 64 having the same wavelength dispersion characteristic of the phase difference value is installed in each of the three liquid crystal panels 30 (30R, 30G, 30B), the phase difference is effectively compensated in all the liquid crystal panels 30. It is difficult. For example, when the phase difference plate 64 having the characteristic FG in FIG. 3 is installed in common on the three liquid crystal panels 30 (30R, 30G, 30B), the liquid crystal 34 of the liquid crystal panel 30G on which green light (wavelength: about 550 nm) is incident. The phase difference is effectively compensated for, but the phase difference is not sufficiently compensated for in the liquid crystal panel 30R on which red light (wavelength: about 650 nm) is incident and the liquid crystal panel 30B on which blue light (wavelength: about 450 nm) is incident.

  In the present embodiment, the wavelength dispersion characteristic of the retardation value of the retardation plate 64 (64R, 64G, 64B) is different for each liquid crystal panel 30 (for each color) so that the phase difference of each liquid crystal panel 30 is effectively compensated. Is different. Specifically, the phase difference plate 64R having the characteristic FR shown in FIG. 3 is installed in the liquid crystal panel 30R, the phase difference plate 64G having the characteristic FG is installed in the liquid crystal panel 30G, and the phase difference of the characteristic FB is installed in the liquid crystal panel 30B. A plate 64B is installed. The characteristic FR of the phase difference plate 64R is such that the phase difference value of the phase difference plate 64R with respect to the red light is the phase difference value of the liquid crystal 34 with respect to the red light (that is, the phase difference value corresponding to the wavelength of 650 nm in the characteristic F_LC) Re_LC (650 ) Is selected. Similarly, the characteristic FG of the phase difference plate 64G is selected so that the phase difference value of the phase difference plate 64G with respect to green light matches the phase difference value Re_LC (550) of the characteristic F_LC. The characteristic FB of the phase difference plate 64B is selected so that the phase difference value of the phase difference plate 64B with respect to blue light matches the phase difference value Re_LC (450) of the characteristic F_LC.

  In the present embodiment, it is assumed that the birefringence (difference between ordinary light refractive index and extraordinary light refractive index) Δn of each phase difference plate 64 (64R, 64G, 64B) is equal. Specifically, each phase difference plate 64 (64R, 64G, 64B) is formed of a common material. Since the phase difference value of the phase difference plate 64 corresponds to a product value (Δn · d) of the birefringence Δn and the thickness d of the phase difference plate 64, the characteristics (FR, FG, FB) of the phase difference plate 64 are as follows. It depends on the thickness (dR, dG, dB) of each phase difference plate 64. A procedure for determining the thickness (dR, dG, dB) of each phase difference plate 64 so that the characteristic FR, the characteristic FG, and the characteristic FB satisfy the conditions of FIG. 3 will be described in detail below.

  FIG. 4 is a flowchart of a procedure for determining the thickness (dR, dG, dB) of each phase difference plate 64. First, for the liquid crystal 34 of the liquid crystal panel 30 (any one of the three), as shown in FIG. 3, the phase difference value Re_LC (650) for red light, the phase difference value Re_LC (550) for green light, and blue light A phase difference value Re_LC (450) is measured (S1). A known technique is arbitrarily employed for measuring the phase difference value Re_LC (λ) of the liquid crystal 34.

  Next, the phase difference value (characteristic FG) of the phase difference plate 64G with respect to green light matches the phase difference value Re_LC (550) measured in step S1 (that is, the phase difference value Re_LC (550) in FIG. 3). The thickness dG of the phase difference plate 64G is determined (so that the characteristic FG passes through the point PG) (S2). Further, as shown in FIG. 3, the phase difference value Re_REF (650) for red light and the phase difference value Re_REF (450) for blue light are measured for the phase difference plate 64G having the thickness dG determined in step S2. (S3). A known technique is arbitrarily employed for measuring the phase difference value Re_REF (λ) of the phase difference plate 64G.

  Then, the phase difference values (Re_LC (650), Re_REF (650), Re_LC (450), Re_REF (450)) measured in step S1 and step S3 and the thickness of the phase difference plate 64G determined in step S2. Through calculation using dG, the thickness dR of the phase difference plate 64R and the thickness dB of the phase difference plate 64B are determined (S4, S5). The determination of the thickness dR and the thickness dB will be described in detail below.

First, the following formula including the phase difference value Re_LC (650) of the liquid crystal 34 measured in step S1 for red light and the phase difference value Re_REF (650) of the phase difference plate 64G measured in step S3 for red light. The thickness dR of the phase difference plate 64R is set according to the thickness dG of the phase difference plate 64G determined in step S2 so that the relationship (1) is established (S4).
dR = dG · (Re_LC (650) / Re_REF (650)) (1)

  That is, the thickness dR of the retardation plate 64R is multiplied by the relative ratio of the retardation value Re_LC (650) of the liquid crystal 34 to the retardation value Re_REF (650) of the retardation plate 64G and the thickness dG of the retardation plate 64G. Defined as a value. As understood from the contents of the equation (1) and the definition of the retardation value (Δn · d), the characteristic FR (FIG. 3) of the retardation plate 64R having the thickness dR calculated by the equation (1) is: This corresponds to a characteristic obtained by translating the characteristic FG of the phase difference plate 64G in the axial direction of the phase difference value so as to pass the point PR of the phase difference value Re_LC (650) of the liquid crystal 34 with respect to red light. As illustrated in FIG. 3, when the retardation value Re_LC (650) of the liquid crystal 34 is lower than the retardation value Re_REF (650) of the retardation plate 64G, the thickness dR of the retardation plate 64R is the thickness of the retardation plate 64G. Below dG (dR <dG).

The thickness dB of the phase difference plate 64B is set by the same method as the thickness dR of the phase difference plate 64R. That is, the following formula including the phase difference value Re_LC (450) of the liquid crystal 34 measured in step S1 for blue light and the phase difference value Re_REF (450) of the phase difference plate 64G measured in step S3 for blue light. The thickness dB of the phase difference plate 64B is set according to the thickness dG of the phase difference plate 64G determined in step S2 so that the relationship (2) is established.
dB = dG (Re_LC (450) / Re_REF (450)) (2)

  Similar to the description of the characteristic FR described above, the characteristic FB of the retardation plate 64B having the thickness dB calculated by the equation (2) is the retardation value Re_LC (450 of the liquid crystal 34 with respect to the blue light as shown in FIG. This corresponds to a characteristic obtained by translating the characteristic FG of the phase difference plate 64G in the axial direction of the phase difference value so as to pass through the point PB. As shown in FIG. 3, when the retardation value Re_LC (450) of the liquid crystal 34 exceeds the retardation value Re_REF (450) of the retardation plate 64G, the thickness dB of the retardation plate 64B is equal to the thickness dG of the retardation plate 64G. Over (dB> dG).

  In the above embodiment, the thickness required for the retardation plate 64R according to the numerical values (Re_LC (650), Re_REF (650), Re_LC (450), Re_REF (450), dG) related to the liquid crystal panel 30 and the retardation plate 64G. Since the thickness dR and the thickness dB required for the phase difference plate 64B are set, the wavelength dispersion characteristic of the phase difference value is measured for each of the phase difference plate 64R and the phase difference plate 64B to obtain the thickness (dR, dB). The work of optimizing (the work of step S2) is unnecessary. That is, there is an advantage that the thickness (dR, dG, dB) of the phase difference plate 64 (64R, 64G, 64B) capable of effectively compensating for the phase difference of incident light with respect to each liquid crystal panel 30 can be easily determined.

  By the way, in the projection light from the projection optical system 40, the amount of green light is generally larger than that of red light and blue light, and human vision has higher sensitivity to green light than sensitivity to red light and blue light. . In the above embodiment, since the thickness dG of the phase difference plate 64G corresponding to the green light is set according to the actual measurement result, the phase difference of the green light that is easily perceived by the observer is compensated with high accuracy. It is possible. Therefore, as compared with the configuration based on the phase difference plate 64R and the phase difference plate 64B, there is an extraordinary effect that it is difficult for an observer to perceive a deterioration in display quality due to insufficient phase difference compensation.

<Modification>
In the above embodiment, both the thickness dR of the phase difference plate 64R and the thickness dB of the phase difference plate 64B are determined according to the characteristic FG of the phase difference plate 64G, but step S4 is performed for only one type of phase difference plate 64. It is also possible to apply the same method as in step S5. For example, when the thickness dG of the phase difference plate 64G and the thickness dR of the phase difference plate 64R are determined in the same manner as in step S2 according to the measurement result of the wavelength dispersion characteristic of the phase difference value, the calculation of Equation (2) Thus, only the thickness dB of the phase difference plate 64B is calculated from the thickness dG, and step S4 for calculating the thickness dR of the phase difference plate 64R is omitted.

  In the above embodiment, the thickness dR of the phase difference plate 64R and the thickness dB of the phase difference plate 64B are calculated from the thickness dG of the phase difference plate 64G. This is the basis of the calculation in step S4 and step S5. The thickness d is not limited to the thickness dG of the phase difference plate 64G. For example, when the thickness dR of the phase difference plate 64R is determined in step S2, the thickness dG of the phase difference plate 64G and the thickness dB of the phase difference plate 64B are determined in step S2 in step S4 and step S5. Is calculated from dR. Furthermore, the color combination (color type and number of colors) of the image formed by each liquid crystal panel 30 is not limited to the above examples (three colors of red, green, and blue).

  In the above embodiment, the transmissive liquid crystal panel 30 is exemplified. However, the above-described method for determining the characteristics of each phase difference plate 64 is similarly applied to a projection display device using the reflective liquid crystal panel 30. .

DESCRIPTION OF SYMBOLS 10 ... Illuminating device, 20 ... Separation optical system, 30 (30R, 30G, 30B) ... Liquid crystal panel, 40 ... Projection optical system, 42 ... Dichroic prism, 44 ... Projection lens, 31 ... 1st Substrate, 32 ... second substrate, 34 ... liquid crystal, 61, 62 ... polarizing plate, 64 (64R, 64G, 64B) ... retardation plate.

Claims (3)

A first liquid crystal panel that modulates light of a first wavelength;
A second liquid crystal panel that modulates light of a second wavelength different from the first wavelength;
A projection optical system for projecting light modulated by each of the first liquid crystal panel and the second liquid crystal panel;
The first liquid crystal panel has a first retardation plate,
The second liquid crystal panel has a second retardation plate,
The first liquid crystal panel and the second liquid crystal panel have the same wavelength dispersion characteristic of the retardation value of the liquid crystal,
A numerical formula (A) including a retardation value Re_LC (λ2) of the liquid crystal of the first liquid crystal panel with respect to the light of the second wavelength and a retardation value Re_REF (λ2) of the first retardation plate with respect to the light of the second wavelength. ) Is established in accordance with the thickness d1 of the first retardation plate d2 = d1 · (Re_LC (λ2) / Re_REF (λ2) ) (A)
Projection display device. Comprising a third liquid crystal panel that modulates light of a third wavelength different from the first wavelength and the second wavelength;
The projection optical system projects light modulated by each of the first liquid crystal panel, the second liquid crystal panel, and the third liquid crystal panel,
The third liquid crystal panel has a wavelength dispersion characteristic of a retardation value of liquid crystal that is equivalent to that of the first liquid crystal panel and the second liquid crystal panel, and has a third retardation plate,
Formula (B) including a phase difference value Re_LC (λ3) of the liquid crystal of the first liquid crystal panel with respect to the light of the third wavelength and a phase difference value Re_REF (λ3) of the first phase plate with respect to the light of the third wavelength. ) Is set in accordance with the thickness d1 of the first retardation plate d3 = d1 · (Re_LC (λ3) / Re_REF (λ3) ) (B)
The projection display device according to claim 1. The light of the first wavelength is green light;
The light of the second wavelength is red light;
The projection display apparatus according to claim 2, wherein the third wavelength light is blue light.

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