JPS61275615A - Two-split photodetecting element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention [Field of Industrial Application] The present invention relates to a two-split light-receiving element for an active automatic focus adjustment (autofocus) device of a camera.

[Conventional technology]

The principle mechanism of currently used autofocus devices is that, as shown in Fig. 19, infrared light emitted from a light source bulb 1 passes through a projection system lens 2 and then is always spotted on the photographing optical axis. The spot image S is formed on the light receiving elements 5A and 5B, which are divided into upper and lower parts by a straight boundary line 5, as shown in FIG. 20.

Photoelectric conversion is performed by the pixel element, and the respective outputs, OA and Os, are converted to the front pin (S n) and the red pin (S f) by the comparison circuit 6.
The signal is converted into a motor control signal corresponding to the motor control signal and transferred as the output of the motor 7. The lens 4 or another focusing lens not shown in the drawings is moved in a direction according to this output signal, and focusing is achieved by matching the outputs of the upper and lower elements.

[Problem that the invention seeks to solve]

However, for some reason, an object having a contrast between a portion R of high reflectance and a portion of low reflectance may be covered by the distance measuring light projection spot.

Now, as shown in Fig. 21(a), a spot image S with contrast in the horizontal direction (abbreviated as horizontal stripes) is detected by the two-split light-receiving element (
(hereinafter abbreviated as sensor), sensor 5A
Output OA/
An imbalance occurs in the OB, and the resensor or the spot image, or both, are relatively moved by the servo until the OB becomes balanced, for example, in the state shown in FIG.

At this time, since the light-receiving lens 4 is of course linked to the servo, it moves regardless of the distance to the subject, and the center 0 of the spot image S on the sensor is shifted by a distance qo with respect to the boundary line 5. Therefore, the image becomes blurred and sufficient focusing cannot be achieved.

The present invention aims to reduce the above-mentioned blur.

1. Configuration of the Invention [Means for Solving Problems] The present invention uses this type of two-split light-receiving element to project infrared light from the camera side to the subject, and to split the reflected light from the subject into two. In a two-split light receiving element for an active automatic focus adjustment device that detects the subject distance by receiving light with a light receiving element section, the above light receiving element is placed on the horizontal center line of the spot circle when it is at the in-focus position with uniform brightness. On the other hand, the upper and lower boundaries are made equal in area, and the divided shapes are formed so as not to protrude outside the spot circle.

A second invention is the first invention described above, in which the upper and lower division patterns are formed so as to be substantially vertically symmetrical with respect to the center line.

[For production]

FIG. 1 shows the basic form of the first invention of the present invention. When a spot image of a contrasting object is applied to the senna, the spot center O is q from (a) to (b) in the same figure.
After the shift by the same amount, the spot light due to the high reflectance R will also hit the senna 5B, and its output will increase rapidly, and finally both outputs will be 0A11 at the position shown in the same figure (C).
0B will be equal.

The amount of deviation qo in this case is the same as q in the example shown in FIG.

It should naturally be smaller than , so the blur will be less.

According to the second invention, the structure of the invention described above can prevent the vertical contrast pattern from becoming weak.

〔Example〕

A detailed description will be given below with reference to the accompanying drawings.

FIG. 1(a) shows the horizontal center line x- or It coincides with the Oxki division boundary line 5.

The upper and lower boundaries 5-1φ parallel to the horizontal center line XX
5-2, a boundary line extending above and below the center line x-x consisting of a perpendicular line 5-3 passing through the center O of the spot circle is formed, and the areas of the upper and lower sensors 5A and 5B are equally divided.

Note that if there is a protrusion A outside the spot circle S as in this division pattern, the sensitivity (difference in output between the in-focus state and the state slightly deviated from the focused state) will decrease, so as shown in Figure 2. The divided shapes are formed so as not to protrude outside the spot circle S by boundary lines 5-4 and 5-5.

Figures 3rjgJ to 12 are examples formed under the above conditions, and in Figures 3 to 6, the boundary line is sine music @5-6,
Figure 8 shows the sine curve and the horizontal line 5-9, and Figure 9 shows the h arc 5-9.
10 and L shadow line 5-11, Figure 10 is an example of the spot circle being divided to the left and right along the vertical center line Y-Y, Figure 11 is the vertical center line Y-Y and the diagonal straight line 5-12, Figure 12 A boundary line is formed by vertical straight zigzag lines 5-13 within the spot circle.

However, if the above structure has a contrast as shown in FIG. 3H, for example, there is a problem that it is susceptible to vertical stripes for the same reason as explained with respect to FIG. 21(a).

Therefore, the second invention is that the blank section 5B in FIG.
As is clear from the contrast between the dotted portion 5A and the dotted portion 5A, in addition to the configuration conditions of the first invention, the one-segment patterns 5A to 5B are formed substantially vertically symmetrical with respect to the horizontal center line x-x. 14 to 18 show various other embodiments of the second invention.

C. Effects of the invention ゛In Fig. 22, which schematically shows the relative positions of the sensor and the spot when a conventional sensor focuses on a contrast pattern and obtains a balanced output, r is the spot radius, qo is the spot center. The amount of deviation between the sensor boundary line 5 and the sensor boundary line 5, a
The distance between the spot center O and the contrast boundary R1, R
When the reflectance of the spot portion R above 1 is 84% and the reflectance below is 8%, the change in distance a when the position of the contrast boundary R1 is changed is plotted as the horizontal axis, and the spot shift N is
q o is represented by the graph shown by the solid line in FIG. 23 on the vertical axis.

The maximum amount of deviation was so large that it could not be ignored compared to the depth of field of the photographic lens, and sufficient focusing could not be achieved.

The sensor of the present invention is represented by the dotted line in FIG. 23 because the amount of deviation qo' is smaller than qo in FIG. 22 for the reason explained in the operation section of FIG. It has the effect of eliminating or reducing defects.

In addition, in the case of the present invention, since the protrusion A in FIG. 1(a) is eliminated as shown in FIG. 2 (the same applies to other embodiments), even if the spot circle S moves slightly up or down in FIG. , output OA・0
There is almost no change in Higami, so there is no decrease in sensitivity.

FIG. 24 is a graph showing the conventional dividing line 5, the dividing line of the present invention, the quantity ratio, and the sensitivity ratio.

In the first invention, for example, in Fig. 3, when vertical stripes R are formed, there is a difference in the light receiving area (5A>5B), so it is weak.If the upper and lower patterns of the second invention are made symmetrical, the R As can be understood from the above, it is possible to prevent contrast blurring even for the vertical stripes.

[Brief explanation of the drawing]

FIGS. 1 to 12 show various embodiments of the light receiving element of the first invention, FIGS. 13 to 18 show embodiments of the second invention, and FIGS.
The figure is a conceptual diagram of a conventionally used active automatic focus detection device, Figure 20 is a diagram showing the relationship between a two-split light receiving element and a spot image, and Figures 21 and 22 are a diagram showing the relationship between a two-split light receiving element and a spot image. An explanatory diagram when a contrasting spot image is applied, FIG. 23 is a graph showing the amount of spot shift when changing the position of the contrast boundary, and FIG. 24 is a graph of the amount of blur and sensitivity. 1 is an infrared light source, 2 is a projection system lens, 3 is a subject, 4 is a light receiving system lens, 5A and 5B are two-part light receiving elements, 6 is a comparison circuit, and 7 is a motor. Figure 16 Figure 17 Figure 18 Figure 13 Figure 14 Figure 15 Aya

Claims (2)

[Claims] (1) A two-split light-receiving element for an active automatic focus adjustment device that emits infrared light from the camera side to the subject, and detects the subject distance by receiving the reflected light from the subject with a two-split light-receiving element. In this case, the above light-receiving element is arranged so that the upper and lower areas are equal on the boundary line that extends above and below the horizontal center line of the spot circle when it is in the focused position with uniform brightness, and the divided shape is outside the spot circle. A light receiving element characterized by being formed so as not to protrude. (2) A two-split light-receiving element for an active automatic focus adjustment device that emits infrared light from the camera side to the subject, and detects the subject distance by receiving the reflected light from the subject with a two-split light-receiving element. In this case, the above light-receiving element is arranged so that the upper and lower areas are equal on the boundary line that extends above and below the horizontal center line of the spot circle when it is in the focused position with uniform brightness, and the divided shape is outside the spot circle. A light-receiving element characterized in that it is formed so as not to protrude, and that its upper and lower division patterns are formed substantially symmetrically with respect to the center line.