diff --git a/src/camera.rs b/src/camera.rs
index c9dcf20..bc7b230 100644
--- a/src/camera.rs
+++ b/src/camera.rs
@@ -2,7 +2,7 @@ use std::fs::File;
 use std::io::{BufWriter};
 
 use crate::hittable::HittableList;
-use crate::math_utils::{clamp, degrees_to_radians};
+use crate::math_utils::{clamp, degrees_to_radians, random_in_unit_disk};
 use crate::ppm_writer::PPMWriter;
 use crate::types_defined::{Camera, Color, HitRecord, Point, Ray, Vec3};
 use rand::rngs::ThreadRng;
@@ -19,14 +19,17 @@ impl<'a> Camera<'a> {
         v_up: Vec3,
         sample_times: i8,
         reflect_depth: i8,
+        defocus_angle : f32,
+        focal_distance: f32,
         ppm_file_writer: &'a mut PPMWriter<BufWriter<File>>
     ) -> Self {
 
-       let focal_length = (look_at - center).length();
+    //    let focal_length = (look_at - center).length();
 
        let theta = degrees_to_radians(fov);
        let h = f32::tan(theta / 2.);
-       let viewport_height = 2. * h * focal_length;
+       let viewport_height = 2. * h * focal_distance;
+    //    let viewport_height = 2. * h * focal_length;
 
         let image_height = ((image_width as f32 / aspect_ratio) as i32).max(1);
         let viewport_width = viewport_height * (image_width as f32 / image_height as f32);
@@ -48,11 +51,18 @@ impl<'a> Camera<'a> {
         // height per pix
         let viewport_v_delta = viewport_v / (image_height as f32);
         let viewport_top_left_pixel =
-            center - focal_length * w - viewport_u / 2.0 - viewport_v / 2.0;
+            center - focal_distance * w - viewport_u / 2.0 - viewport_v / 2.0;
+            // center - focal_length * w - viewport_u / 2.0 - viewport_v / 2.0;
         // padding 0.5* delta u/v
         let viewport_top_left_pixel_center =
             viewport_top_left_pixel - viewport_u_delta / 2.0 - viewport_v_delta / 2.0;
 
+
+        // Calculate the camera defocus disk basis vectors.
+        let defocus_radius = focal_distance * degrees_to_radians(defocus_angle / 2.0).tan();
+        let defocus_disk_u = u * defocus_radius;
+        let defocus_disk_v = v * defocus_radius;
+
         Camera {
             image_width,
             image_height,
@@ -65,6 +75,10 @@ impl<'a> Camera<'a> {
             // focal_length,
             // viewport_u,
             // viewport_v,
+            defocus_angle,
+            defocus_disk_u,
+            defocus_disk_v,
+
             viewport_u_delta,
             viewport_v_delta,
             viewport_top_left_pixel_center,
@@ -87,11 +101,7 @@ impl<'a> Camera<'a> {
                 let mut color = Color::new(0.0, 0.0, 0.0);
                 let rng = &mut rng();
                 for _ in 0..self.sample_times {
-                    let bias = self.random_square(rng);
-                    let pix_sample = self.viewport_top_left_pixel_center
-                        + (i as f32 + bias.x) * self.viewport_u_delta
-                        + (j as f32 + bias.y) * self.viewport_v_delta;
-                    let r = Ray::new(self.center, pix_sample - self.center);
+                    let r = self.get_ray(i, j);
                     let sample_color = self.ray_color(&r, self.reflect_depth, world);
                     color = color + sample_color;
                 }
@@ -114,6 +124,26 @@ impl<'a> Camera<'a> {
         // img_content
     }
 
+    fn defocus_disk_sample(&self) -> Point {
+        // Returns a random point in the camera defocus disk.
+        let p = random_in_unit_disk();
+        return self.center + (p.x * self.defocus_disk_u) + (p.y * self.defocus_disk_v);
+    }
+
+    fn get_ray(&self, i: i32, j: i32) -> Ray {
+        let rng = &mut rng();
+        let bias = self.random_square(rng);
+        let pix_sample = self.viewport_top_left_pixel_center
+            + (i as f32 + bias.x) * self.viewport_u_delta
+            + (j as f32 + bias.y) * self.viewport_v_delta;
+        let center = if self.defocus_angle < 0. {
+            self.center
+        } else {
+            self.defocus_disk_sample()
+        };
+        Ray::new(center, pix_sample - self.center)
+    }
+
     fn ray_color(&self, ray: &Ray, depth: i8, world: &HittableList) -> Vec3 {
 
         // 反射次数
diff --git a/src/main.rs b/src/main.rs
index d751b23..63a8702 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -23,10 +23,10 @@ fn main() {
 fn camera_render() {
 
     let fov: f32 = 60.;
-    let scale = 1;
+    let scale = 2;
     let width: i32 = 800/scale;
     let height: i32 = 600/scale;
-    let sample_times = 50;
+    let sample_times = 20;
     let reflect_depth = 20;
 
 
@@ -44,11 +44,13 @@ fn camera_render() {
         fov,
         width,
         width as f32 / height as f32,
-        Point::new(-2.0, 0.0, -1.0),
+        Point::new(-0.0, 0.0, 0.0),
         Point::new(0.0, 0.0, -1.0),
         Vec3::new(0., 1., 0.),
         sample_times,
         reflect_depth,
+        2.0,
+        1.0,
         pw
     );
     // world
diff --git a/src/math_utils.rs b/src/math_utils.rs
index 0dc0285..3ee490d 100644
--- a/src/math_utils.rs
+++ b/src/math_utils.rs
@@ -1,7 +1,19 @@
 use std::f32::consts::PI;
 
+use rand::{rng, Rng};
+
 use crate::types_defined::{Ray, Vec3};
 
+pub fn random_in_unit_disk() -> Vec3 {
+    let rng = &mut rng();
+    loop {
+        let p = Vec3::new(rng.random_range(-1.0..1.0), rng.random_range(-1.0..1.0), 0.0);
+        if (p.length_squared() < 1.0) {
+            return p;
+        }
+    } 
+}
+
 pub fn degrees_to_radians(deg: f32) -> f32 {
     deg * PI / 180.
 }
diff --git a/src/types_defined.rs b/src/types_defined.rs
index d8c75c9..21be19d 100644
--- a/src/types_defined.rs
+++ b/src/types_defined.rs
@@ -43,6 +43,10 @@ pub struct Camera<'a> {
     // pub focal_length: Vec3,
     // pub viewport_u: Vec3,
     // pub viewport_v: Vec3,
+    pub defocus_angle: f32,
+    pub defocus_disk_u: Vec3,
+    pub defocus_disk_v: Vec3,
+
     pub viewport_u_delta: Vec3,
     pub viewport_v_delta: Vec3,
     pub viewport_top_left_pixel_center: Vec3,