JP2679103B2 - Projection lens system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection lens system using a zoom lens, and more specifically, to a pupil position on the reduction side of a zoom lens system that is unchanged during zooming. The present invention relates to a projection lens system that always satisfies the conditions of Koehler illumination without changing the position of the condenser lens system.

[Conventional technology]

Koehler illumination has been widely used in projection optical systems such as microscopes, since an image with uniform illuminance can be obtained.
A projection optical system using a conventional Koehler illumination system will be described with reference to FIG. That is, the projection lens system is a zoom lens system formed by the diaphragm 7, the first positive lens group 5 and the second negative lens group 6 from the side of the screen 8 on the enlargement side. It is designed to project. Then, in order to illuminate the film 4, the light flux from the light source 1 is made into a substantially parallel light flux by the first condenser lens group 2, and is brought to the position of the diaphragm 7 of the zoom lens system for projection by the second condenser lens group 3. An image of the light source 1 is formed. In this way, the filament image of the light source 1 is formed at the pupil position of the projection lens system by transmitting and illuminating the film 4 so that the Koehler illumination condition is satisfied, and an image of uniform and efficient illuminance is displayed on the screen 8. Is projected.

[Problems to be solved by the invention]

By the way, since the projection lens system is a zoom lens,
As the lens moves from the long focal length end shown in FIG. 4 (A) to the short focal length end shown in FIG. 4 (B) for zooming, the position of the diaphragm 7 also changes, and the Koehler illumination The condition is no longer satisfied. For this reason, the first lens group 2 or the second lens group 3 of the condenser lens system or the entire condenser lens system is moved so as to satisfy the Koehler illumination condition.

Therefore, in order to maintain this illumination condition during zooming of the projection lens system, the user must adjust the condenser lens system or move the condenser lens system mechanically in conjunction with the zoom lens system. However, there is a problem that the operability of the user is lowered or the cost of the device is increased.

The present invention has been made in view of such a point,
In a projection lens system consisting of a zoom lens, a projection lens system is formed that does not change the position of the pupil on the reduction side during zooming and that always satisfies the conditions of Koehler illumination without changing the arrangement of the condenser lens system. The purpose is to provide.

[Means and actions for solving the problems]

According to the present invention, a stop is provided from the enlargement side, a two-component zoom lens system having a finite conjugate distance composed of a first positive lens group and a second negative lens group, and a light beam from a light source is imaged on a reduction-side pupil position of the zoom lens system. In the projection lens system using the condition of the Koehler illumination composed of a condensing lens system for making the light source and the light source, the second negative lens group is used when zooming from the long focal length end to the short focal length end of the zoom lens system. The projection lens system is characterized in that the pupil position on the reduction side is kept constant in conjunction with the movement of.

Therefore, even if zooming is performed, the conditions of Koehler illumination are always satisfied, the projected image on the screen is uniform and the illuminance is efficient, and the operability is remarkably improved.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows the diaphragm from the enlargement side, the first positive lens group and the second positive lens group.
FIG. 1 is a schematic diagram showing a zooming state in a two-component zoom lens system having a finite conjugate distance composed of a negative lens group, FIG. 1 (A) being at a long focal length end, and FIG. 1 (B) being a short focal length. The state of the edge is shown. This zoom lens system
It is composed of a diaphragm 7, a first positive lens group 5, and a second negative lens group 6 from the image plane 8 side, and when zooming from the long focal length end to the short focal length, the first positive lens group 5 and the second negative lens Zooming is performed by moving both the lens groups 6 toward the object plane 4 so as to open the lens groups from each other.

Next, in such a projection lens system, a specific example for fixing the pupil position on the reduction side will be described using a paraxial power arrangement.

As shown in FIGS. 1A and 1B, the refractive power of the first positive lens group 5 (the reciprocal of the focal length) Ψ ₁ (Ψ ₁ <o), the second
The refractive power of the negative lens group 6 is Ψ ₂ (Ψ ₂ <o), and the conversion surface exchange between the first positive lens group 5 and the second negative lens group 6 at the long focal length end is e ₁ (e ₁ > O), the distance between the first positive lens group 5 and the reference image plane 8 at the long focal length end is S ₁ (S ₁ <o), and the object surface 4 when the zooming state is at the long focal length end The distance from the upper object point to the image point by the second negative lens group 6 with respect to the second negative lens group 6 is a ₁ (a ₁ > o), and the object plane 4 and the second surface at the long focal length end The distance of the negative lens group 6 is b ₁
(B ₁ <o), the moving distance of the second negative lens group 6 at the long focal length end reference is x (x> o), and the moving distance of the first positive lens group 5 at the long focal length end reference is y (Y> o), the image point of the second negative lens group 6 when the second negative lens group 6 moves by x is a (a> o).

(I) Paraxial imaging condition at the long focal length extremity Regarding the second negative lens group 6 Regarding the first positive lens group 5 It is.

(II) Paraxial condition when the second negative lens group 6 moves x Regarding the second negative lens group 6 Magnification is Regarding the first positive lens group 5 The magnification is It is.

When the above formula (5) is rearranged with respect to y, Ψ ₁ y ² + Ay + B = 0 (7) where A = −Ψ ₁ (x + a + s ₁ + e ₁ ) B = Ψ ₁ s ₁ (x + a + e ₁ ) + x + a + e ₁ −s ₁ (8) From the above formula (3) And y can be written as a function of x.

Next, the paraxial ray tracing of the pupil is used to find the movement condition of the diaphragm position for fixing the pupil position on the reduction side.

In FIGS. 2 (A) and 2 (B), the conversion surface spacing up to the position of the diaphragm 7 based on the first positive lens group 5 at the long focal length end is e ₂
(E ₂ <0 in the figure), similarly for the first positive lens group 5 based on the first
Distance to the image point position P of the diaphragm 7 by the positive lens group 5 (c ₁
<0), when the object point is set to the image point position P of the diaphragm 7 by the first positive lens group 5, the distance to the image position by the second negative lens group 6 based on the second negative lens group 6 is d ₁ ( d ₁ <0) The above conditions are calculated when the values corresponding to c ₁ and d ₁ when the moving distance of the second negative lens group 6 is x are c and d, respectively.

(III) Pupil position at the long focal length extremity The imaging conditions for the first positive lens group 5 are: Regarding the second negative lens group 6, The pupil position is given by the following formula.

P _I = d ₁ −b ₁ (12) (P _I <0) (IV) The pupil position when the second negative lens group 6 moves x The imaging conditions for the first positive lens group 5 are: Regarding the second negative lens group 6, The pupil position is P _II = d- (b ₁ -x) where the condition for invariant pupil position is P _I = P _II d = d ₁ -x (15) Equation (10) above Than From equation (11) above Becomes

Eliminating c from Eqs. (13) and (14) and solving for Z, which is the amount of movement of the diaphragm, Therefore, the movement amount Z of the diaphragm can be expressed as a function of x with Ψ ₁ , Ψ ₂ , e ₁ , e ₂ , b ₁ as initial values.

That is, the movement amount given by the above equation (18) is
If the movement of the negative lens group 6 is given, the minimum pupil position can be kept constant.

Specific examples of the embodied projection lens system to which the embodiment of the present invention is applied are shown in Table 1 below, and its sectional view is shown in FIG.

Here, Ψ ₁ = 0.03450, Ψ ₂ = −0.02533, e ₁ = 14.94
When 2, e ₂ = -11.794, S ₁ = -1344.994, X _max = 16.276, y _max = 7.593, Z = -6.778, and P _I = P _II = -41.86.
And the pupil position is unchanged.

According to the present invention, the movement of the diaphragm 7 does not necessarily have to be a strict non-linear movement as shown in the above equation (18), and the Koehler illumination condition is not practically collapsed so that the illuminance required on the image plane can be obtained. Of course, it is only necessary to move approximately.

Further, the positive / negative two-component zoom lens system has been described. However, a zoom lens system of three or more components having a moving lens group integrated with a diaphragm or a fixed lens group not integrated with the first positive lens group. Also in the above, the pupil position on the reduction side can be kept constant by moving the optical diaphragm position.

〔The invention's effect〕

As described above, according to the present invention, the projection lens is composed of the zoom lens system, and since it is not necessary to move the condenser condenser lens system at the time of zooming, only the fixing member is provided, In addition to simplification and cost reduction, the user can omit the adjustment operation for satisfying the condition of the Koehler illumination, and the operability is remarkably improved.

[Brief description of the drawings]

1 (A) and (B) and FIGS. 2 (A) and (B),
FIG. 3 is a diagram showing a state of a long focal length end and a short focal length end showing paraxial power arrangement in a zoom lens system, for explaining the configuration of the present invention. FIG. 3 is a lens to which the present invention is applied. Sectional views of the system, and FIGS. 4A and 4B are diagrams showing the states of the conventional projection optical system at the long focal length end and the short focal length end. 5 ... First positive lens group 6 ... Second negative lens group 7 ... Aperture

Claims (2)

(57) [Claims] 1. A diaphragm, a first positive lens group, and a second lens from the enlargement side.
A two-component zoom lens system with a finite conjugate distance consisting of a negative lens group, and a Koehler illumination composed of a condensing lens system for focusing a light beam from a light source on the reduction side pupil position of the zoom lens system and a light source. In the magnifying projection lens system used, when zooming from the long focal length end side of the zoom lens system to the short focal length end side, the first positive lens group and the second negative lens group are directed toward the object side and the distance between the lens groups is increased. The projection lens system is characterized in that the aperture is moved to open and the aperture is moved in conjunction with the movement of the first and second lens groups so as to keep the pupil position on the reduction side of the zoom lens system constant. 2. The projection lens system according to claim 1, wherein the movement of the diaphragm substantially satisfies the following equation, where Z is the amount of movement. Where Ψ _{1 is} the refracting power of the first positive lens group Ψ _{2 is} the refracting power of the second negative lens group e ₁ : The reduced surface distance e ₂ between the first positive lens group and the second negative lens group at the long focal length end : Converted surface distance at the long focal length end between the first positive lens unit and the aperture based on the first positive lens unit reference x: Moving amount during zooming from the long focal length end of the second negative lens unit y: First Amount of movement of the positive lens unit from the long focal length end during zooming d: The pupil position on the reduction side of the second negative lens unit reference during zooming, where d = d ₁ −x d ₁ : At the long focal length end Pupil position on the reduction side of the second negative lens group reference In both cases, the direction from the reference position to the reduction side is positive.